OPERATION
OF
WASTEWATER
TREATMENT
PLANTS
Volume II


A
Field
Study
Training
Program

. ENVIRONMENTAL PROTECTION AGENCY •
• OFFICE OF WATER PROGRAMS •
• DIVISION OF MANPOWER AND TRAINING •

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Environmental Protection Agency Review Notice
This training manual has been reviewed by the Office of Water Program
Operations, U.S. Environmental Protection Agency, and approved for publi-
cation. Approval does not signify that the contents necessarily reflect the
views and policies of the Environmental Protection Agency. Mention of trade
names or commercial products does not constitute endorsement or recom-
mendation for use by the Environmental Protection Agency, California State
University, Sacramento, California Water Pollution Control Association, au-
thors of the chapters or project reviewers and directors.

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OPERATION OF WASTEWATER
TREATMENT PLANTS
Second Edition
Volume II
A Field Study Training Program
prepared by
California State University, Sacramento
(formerly Sacramento State College)
Department of Civil Engineering
in cooperation with the
California Water Pollution Control Association
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Kenneth D. Kerri, Project Director
Bill B. Dendy, Co-Director
John Brady, Consultant and Co-Director
William Crooks, Consultant
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~A1
for the
Environmental Protection Agency
Office of Water Program Operations
Municipal Permits and Operations Division
First Edition, Technical Training Grant No. 5TT1-WP-16-03 (1970)
Second Edition, Grant No. T900690010
1980

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MOTICE
This manual is revised and updated before each printing based en com-
ments from persons using fee manual.
First printing, t671
5,AM
Second printing, 1972
7,000
Third printing, 1973
9,000
Fourth printing, 1974
6,660
Fitti printing, 1975
4,666
Sixth printing, 1977
11,000
Seventh printing, 1979
4,666
SECOND EDITION, Volume W
First printing, 1960	7,600
ii

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PREFACE TO THE SECOND EDITION
VOLUME II
Volume II is a continuation of Volume I. In Volume I, the emphasis was on the knowledge and skills needed by
new operators and the operators of smaller treatment facilities. Volume II stresses information needed by these
operators, but shifts emphasis towards larger conventional treatment plants. This volume also will be helpful to
operators in supervisory and management positions.
All operators need to know how to perform basic arithmetic calculations and laboratory procedures to measure
wastewater characteristics. Chapter 16 outlines in detail the step-by-step procedures to measure wastewater
characteristics. Chapter 17 contains example problems showing how to solve most arithmetic problems that
operators may have to work while operating their plant. You can solve all of these problems by the use of addition,
subtraction, multiplication and division. All of these problems can be easily worked by the use of pocket electronic
calculators. Many operators have looked at and actually started these two chapters while they were working on
Volume I.
Regardless of the size or type of treatment plant that you operate, all of the chapters in Volume II contain
information you need to know to do your job. Every treatment plant requires the operator to know how to treat and
handle solids, dispose of the plant effluent, conduct your duties following safe procedures, maintain the equipment,
keep records, analyze data and write reports. If your plant has advanced waste treatment processes, unusual solids
handling or disposal facilities, or treats industrial wastes, you will want to continue to Volume III after you have
completed Volume II.
For information on:
1.	Uses of this manual,
2.	Instructions to participants in home-study course, and
3.	Summary of procedure,
please refer to Volume I.
Kenneth D. Kerri
John Brady
1980
iii

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OPERATION OF WASTEWATER TREATMENT PLANTS
VOLUME II, SECOND EDITION
Chapter Topic	Page
["'"11 Activated Sludge	1
i (Conventional Activated Sludge Plants)
12 Sludge Digestion and Solids Handling	91
^ 13 Effluent Disposal	183
^14 Plant Safety and Good Housekeeping	205
p15 Maintenance	239
i
1 16 Laboratory Procedures and Chemistry	327
r~17 Basic Arithmetic and Treatment Plant Problems 467
18 Analysis and Presentation of Data	515
- 19 Records and Report Writing	547
Final Examination	565
Glossary	577
Index	607
TECHNICAL CONSULTANTS, FIRST EDITION
William Garber	Frank Phillips
George Gardner	Warren Prentice
Carl Nagel	Ralph Stowed
Joe Nagano	Larry Trumbull
TECHNICAL CONSULTANTS, SECOND EDITION
George Gardner	Cart Nagel
Larry Hannah	Al Petrasek
Mike Mulbarger
tv

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COURSE OUTLINE
VOLUME I, SECOND EDITION
Chapter	Topic
1	The Treatment Plant Operator
2	Why Treat Wastes?
3	Wastewater Treatment Facilities
4	Racks, Screens, Comminutors and Grit Removal
5	Sedimentation and Flotation
6	Trickling Filters
7	Rotating Biological Contactors
8	Activated Sludge
(Package Plants and Oxidation Ditches)
9	Waste Treatment Ponds
10	Disinfection and Chlorination
Final Examination
Glossary
Index
VOLUME III, SECOND EDITION
20	Odor Control
21	Activated Sludge
(Pure Oxygen and Operational Control Alternatives)
22	Solids Handling and Disposal
23	Solids Removal from Secondary Effluents
24	Phosphorus Removal
25	Wastewater Reclamation
26	Instrumentation
27	Industrial Waste Monitoring
28	Industrial Waste Treatment
29	Support Systems
Final Examination
Glossary
Index
v

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CHAPTER 11
ACTIVATED SLUDGE
Volume I, Chapter 8
Package Plants and Oxidation Ditches
Volume II. Operation of Conventional
Activated Sludge Plants
Volume III, Chapter 21
Pure Oxygen Plants and Operational Control Options
by
John Brady
Revised by
Ross Gudgel

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2 Treatment Plants
TABLE OF CONTENTS
Chapter 11. Activated Sludge
Volume II. Operation of Activated Sludge Plants
Page
OBJECTIVES		6
GLOSSARY 		7
LESSON 1
11.0	Basic Variables and Record Keeping 		13
11.00	Need for Record Keeping		13
11.01	Variables in Collection System 		13
11.010	Combined Sewer Systems		13
11.011	Waste Dischargers to the System 		13
11.012	Maintenance of the Collection System 		13
11.02	Operational Variables		13
11.03	Plant Records		15
11.04	Typical Lab Results for an Activated
Sludge Plant		16
11.05	Design Variables 		16
11.050	Aeration Methods		16
11.051	Variation of Activated Sludge Process 		16
LESSON 2
11.1	Aeration Systems		20
11.10	Purpose of Aeration		20
11.11	Mechanical Aeration Systems		20
11.12	Diffused Aeration Systems		20
11.120	Air Filters		22
11.121	Blowers (Process Air Compressors) 		22
11.122	Air Distribution System		28
11.123	Air Headers		28
11.124	Diffusers 		28

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Activated Sludge 3
11.2	Safety		28
11.20	Aeration Tanks and Clarifiers 		28
11.21	Surface Aerators 		35
11.22	Air Filters		35
11.23	Blowers 		35
11.24	Air Distribution System		35
11.25	Air Headers and Diffusers		35
LESSON 3
11.3	Checking Out a New Plant	 36
11.30	A New Activated Sludge Plant: Description 		36
11.31	Aerator		36
11.310	Control Gates		36
11.311	Storm Flow Gates and Pedestal
Lift Gates		38
11.312	Weirs 		38
11.313	Movable Gates		3®
11.314	Water Sprays for Froth Control		38
11.315	Air System		38
A.	Air Filters		38
B.	Blowers (Compressors) 		39
C.	Air Headers		4^
D.	Diffusers 		40
E.	Blower Testing		41
11.32	Secondary Clarifiers 		41
11.33	Return Sludge and Waste Sludge Pumps 		41
LESSON 4
11.4	Process Start-Up Procedures		43
11.40	General 		43
11.41	First Day 		43
11.42	Second Day 		44
11.43	Third through Fifth Days		44
11.44	Sixth Day		44
LESSON 5
11.5	Routine Operational Control 		46
11.50	How to Control the Process		46
11.51	Determination of Sludge Age		46

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4 Trsatnwnt Plants
11.52	Wasting Activated Sludge 		47
11.53	Determination of Waste Sludge Pumping Rate		49
11.54	Operational Strategy		49
11.540	Influent Characteristics		49
11.541	Aeration Tank Environment		49
11.542	Secondary Clarifier		50
11.543	Plant Effluent 		50
11.55	Actual Operation Under Normal Conditions		50
11.550	Initial Inspection		50
11.551	Process Adjustment 		50
11.56	Actual Operation Under Abnormal Conditions		54
11.57	Summary		54
LESSON 6
11.6	Operational Problems (Abnormal Operation)		57
11.60	Typical Problems		57
11.61	Plant Changes		57
11.62	Sludge Bulking		59
11.63	Septic Sludge		60
11.64	Toxic Substances		60
11.65	Rising Sludge		60
11.66	Foaming/Frothing		60
LESSON7
11.7	Aerator Loading Guidelines		62
11.70	Use of Loading Guidelines		62
11.71	Food/Microorganism Ratio		62
11.72	Calculation of Food/Microorganism
Aerator Loading		62
11.73	Mean Cell Residence Time (MCRT) 		63
11.74	Calculation of Mean Cell Residence Time 		63
11.8	Activated Sludge Process Equipment		63
11.80	Need for Understanding Equipment		63
11.81	Shutdown		64
11.810	Surface Aerators		64
11.811	Positive Displacement Blowers		64
11.812	Centrifugal Blowers		64
11.813	Air Distribution System		64
11.814	Air Headers and Diffusers		64

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Activated Sludge 5
11.82	Abnormal Conditions		64
11.820	Surface Aerators 		64
11.821	Air Filters		64
11.822	Blowers		66
11.823	Air Distribution System		66
11.824	Air Headers		66
11.825	Air Diffusers 		66
11.83	Maintenance		66
11.830	Surface Aerators 		66
11.831	Air Filters		66
11.832	Blowers 		70
11.833	Air Distribution System		71
11.834	Air Headers		71
11.835	Diffusers 		71
LESSON 8
11.9	Modifications of the Activated Sludge Process 		72
11.90	Reasons for Other Modes of Operation 		72
11.91	Contact Stabilization		72
11.92	Kraus Process 		72
11.93	Step-Feed Aeration		75
11.94	Complete Mix		75
11.95	Modified Aeration		75
11.10	Acknowledgment 	78
11.11	Additional Reading		78
11.12	Metric Calculations 		79
11.120	Conversion Factors		79
11.121	Problem Solutions	 		79

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6 Treatment Plants
OBJECTIVES
Chapter 11. ACTIVATED SLUDGE
The activated sludge process is a very important wastewater
treatment process. For this reason, the chapters on activated
sludge have been divided into three parts and will be pre-
sented in three separate volumes.
I.	Package Plants and Oxidation Ditches
II.	Typical Activated Sludge Plants
III.	Pure Oxygen Plants and Operational Control
If you are the operator of a package plant or oxidation ditch,
Volume I will provide you with the information you need to
know to operate your plant. Volumes II and III will help you
better understand your plant and do a better job. If you operate
a conventional activated sludge plant or a modification, Vol-
ume I will help you understand the activated sludge process
and Volume II will tell you how to operate your plant. Volume III
will explain to you alternative means of operational control that
may work very well for your plant. If you operate a pure oxygen
plant, Volume III will tell you what you need to know to operate
the pure oxygen system. All three parts contain information
important to the proper operation of your plant. Volume III also
contains information helpful to operators using the activated
sludge process to treat special wastes such as industrial
wastes.
The following list of objectives apply to the treatment plants
covered in each of the three parts. After completion of the
appropriate part on activated sludge you should be able to:
1.	Explain the principles of the activated sludge process and
the factors that influence and control the process,
2.	Inspect a new activated sludge facility for proper installa-
tion,
3.	Place a new activated sludge process into service,
4.	Schedule and conduct operation and maintenance duties,
5.	Collect samples, interpret lab results, and make appropri-
ate adjustments in treatment processes,
6.	Recognize factors that indicate an activated sludge pro-
cess is not performing properly, identify the source of the
problem, and take corrective action,
7.	Conduct your duties in a safe fashion,
8.	Determine aerator loadings and understand the applica-
tion of different loading guidelines,
9.	Keep records for an activated sludge plant,
10.	Identify the common modifications of the activated sludge
process, and
11.	Review plans and specifications for an activated sludge
plant.

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Activated Sludge 7
GLOSSARY
Chapter 11. ACTIVATED SLUDGE
ABSORPTION (ab-SORP-shun)	ABSORPTION
Taking in or soaking up of one substance into the body of another by molecular or chemical action (as tree roots absorb dissolved
nutrients in the soil).
ACTIVATED SLUDGE (ACK-ta-VATE-ed sluj)	ACTIVATED SLUDGE
Sludge particles produced in raw or settled wastewater (primary effluent) by the growth of organisms (including zoogleal bacteria) in
aeration tanks in the presence of dissolved oxygen. The term "activated" comes from the fact that the particles are teeming with
bacteria, fungi, and protozoa. Activated sludge is different from primary sludge in that the sludge particles contain many living
organisms which can feed on the incoming wastewater.
ACTIVATED SLUDGE PROCESS (ACK-ta-VATE-ed sluj)	ACTIVATED SLUDGE PROCESS
A biological wastewater treatment process which speeds up the decomposition of wastes in the wastewater being treated. Activated
sludge is added to wastewater and the mixture (mixed liquor) is aerated and agitated. After some time in the aeration tank, the
activated sludge is allowed to settle out by sedimentation and is disposed of (wasted) or reused (returned to the aeration tank) as
needed. The remaining wastewater then undergoes more treatment.
ADSORPTION (add-SORP-shun)	ADSORPTION
The gathering of a gas, liquid, or dissolved substance on the surface or interface zone of another substance.
AERATION LIQUOR (air-A-shun)	AERATION LIQUOR
Mixed liquor. The contents of the aeration tank including living organisms and material carried into the tank by either untreated
wastewater or primary effluent.
AERATION TANK (air-A-shun)	AERATION TANK
The tank where raw or settled wastewater is mixed with return sludge and aerated. The same as aeration bay, aerator or reactor.
AEROBES	AEROBES
Bacteria that must have molecular (dissolved) oxygen (DO) to survive.
AEROBIC DIGESTION (AIR-O-bick)	AEROBIC DIGESTION
The breaking down of wastes by microorganisms in the presence of dissolved oxygen. Waste sludge is placed in a large aerated
tank where aerobic microorganisms decompose the organic matter in the sludge. This is an extension of the activated sludge
process.
AGGLOMERATION (a-GLOM-er-A-shun)	AGGLOMERATION
The growing or coming together of small scattered particles into larger floes or particles which settle rapidly. Also see FLOC.
AIR LIFT	AIR LIFT
A special type of pump. This device consists of a vertical riser pipe submerged in the wastewater or sludge to be pumped.
Compressed air is injected into a tail piece at the bottom of the pipe. Fine air bubbles mix with the wastewater or sludge to form a
mixture lighter than the surrounding water which causes the mixture to rise in the discharge pipe to the outlet. An air-lift pump works
similar to the center stand in a percolator coffee pot.
ALIQUOT (AL-li-kwot)	ALIQUOT
Portion of a sample.
ANAEROBES	ANAEROBES
Bacteria that do not need molecular (dissolved) oxygen (DO) to survive.

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8 Treatment Plants
BACTERIAL CULTURE (back-TEAR-e-al)	BACTERIAL CULTURE
In the case of activated sludge, the bacterial culture refers to the group of bacteria classed as AEROBES and facultative organisms,
which covers a wide range of organisms. Most treatment processes in the United States grow facultative organisms which utilize the
carbonaceous (carbon compounds) BOD. Facultative organisms can live when oxygen resources are low. When "nitrification" is
required, the nitrifying organisms are OBLIGATE AEROBES (require oxygen) and must have at least 0.5 mgIL of dissolved oxygen
throughout the whole system to function properly.
BATCH PROCESS	BATCH PROCESS
A treatment process in which a tank or reactor is filled, the water is treated, and the tank is emptied. The tank may then be filled and
the process repeated.
BIOMASS (BUY-o-MASS)	BIOMASS
A mass or clump or living organisms feeding on the wastes in wastewater, dead organisms and other debris. This mass may be
formed for, or function as, the protection against predators and storage of food supplies. Also see ZOOGLEAL MASS.
BULKING (BULK-ing)	BULKING
Clouds of billowing sludge that occur throughout secondary clarifiers and sludge thickeners when the sludge becomes too light and
will not settle properly.
CATHODIC PROTECTION (ca-THOD-ick)	CATHODIC PROTECTION
An electrical system for prevention of rust, corrosion, and pitting of steel and iron surfaces in contact with water or wastewater.
CHEMICAL OXYGEN DEMAND or COD	CHEMICAL OXYGEN DEMAND or COD
A measure of the oxygen-consuming capacity of inorganic and organic matter present in wastewater. COD is expressed as the
amount of oxygen consumed from a chemical oxidant in mg/L during a specific test. Results are not necessarily related to the
biochemical oxygen demand because the chemical oxidant may react with substances that bacteria do not stabilize.
COAGULATION (ko-AGG-u-LAY-shun)	COAGULATION
The use of chemicals that cause very fine particles to clump together into larger particles. This makes it easier to separate the solids
from the liquids by settling, skimming, and draining or filtering.
COMPOSITE (PROPORTIONAL) SAMPLE	COMPOSITE (PROPORTIONAL) SAMPLE
(com-POZ-it)
A composite sample is a collection of individual samples obtained at regular intervals, usually every one or two hours during a
24-hour time span. Each individual sample is combined with the others in proportion to the flow when the sample was collected. The
resulting mixture (composite sample) forms a representative sample and is analyzed to determine the average conditions during the
sampling period.
CONIN6 (CONE-ing)	CONING
Development of a cone-shaped flow of liquid, like a whirlpool, through sludge. This can occur in a sludge hopper during sludge
withdrawal when the sludge becomes too thick. Part of the sludge remains in place while liquid rather than sludge flows out of the
hopper. Also called "coring."
CONTACT STABILIZATION	CONTACT STABILIZATION
Contact stabilization is a modification of the conventional activated sludge process. In contact stabilization, two aeration tanks are
used. One tank is for separate re-aeration of the return sludge for at least four hours before it is permitted to flow into the other
aeration tank to be mixed with the primary effluent requiring treatment.
DECIBEL	DECIBEL
A unit for expressing the relative intensity of sounds on a scale from zero for the average least perceptible sound to about 130 for the
average pain level.
DEN ITRIFICATION	DENITRIFICATION
A condition that occurs when nitrite or nitrate ions are reduced to nitrogen gas and bubbles are formed as a result of this process.
The bubbles attach to the biological floes and float the floes to the surface of the secondary clarifiers. This condition is often the
cause of rising sludge observed in secondary clarifiers.
DIFFUSED-AIR AERATION	DIFFUSED-AIR AERATION
A diffused air activated sludge plant takes air, compresses it, and then discharges the air below the water surface of the aerator
through some type of air diffusion device.
DIFFUSER	DIFFUSER
A device (porous plate, tube, bag) used to break the air stream from the blower system into fine bubbles in an aeration tank or
reactor.

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Activated Sludge 9
DISSOLVED OXYGEN	DISSOLVED OXYGEN
Molecular oxygen dissolved in water or wastewater, usually abbreviated DO.
ENDOGENOUS (en-DODGE-en-us)	ENDOGENOUS
A reduced level of respiration (breathing) in which organisms break down compounds within their own cells to produce the oxygen
they need.
F/M RATIO	F/M RATIO
Food to microorganism ratio. A measure of food provided to bacteria in an aeration tank.
Food	_ BOD, lbs/day
Microorganisms	MLVSS, lbs
Flew, MGD x BOO, mgH. x 8.34 lbs/gal
er =
Volume, MG x MLVSS, mgIL x 8.34 lbs/gal
BOB, hg/dey
MLVSS, kg
FACULTATIVE (FACK-ul-TAY-twe)	FACULTATIVE
Facultative bacteria can use either molecular (dissolved) oxygen or oxygen obtained from food materials such as sulfate or nitrate
ions. In other words, facultative bacteria can live under aerobic or anaerobic conditions.
FILAMENTOUS BACTERIA (FILL-a-MEN-tuss)	FILAMENTOUS BACTERIA
Organisms that grow in a thread or filamentous form. Common types are thiothrix and actinomyces.
FLIGHTS	FLIGHTS
Scraper boards, made from redwood or other rot-resistant woods or plasic, used to collect and move settled sludge or floating scum.
FLOC	FLOC
Groups or clumps of bacteria that have come together and formed a cluster. Found in aeration tanks and secondary clarifiers.
FLOCCULATION (FLOCK-you-LAY-shun)	FLOCCULATION
The gathering together of fine particles to form larger particles.
FOOD/MICROORGANISM RATIO	FOOD/MICROORGANISM RATIO
Food to microorganism ratio. A measure of food provided to bacteria in an aeration tank.
Food	= BOD, lbs/day
Microorganisms MLVSS, lbs
= Flow, MGD x BOD, mg/L x 8.34 lbs/gal
Volume, MG x MLVSS, mg/L x 8.34 lbs/gal
oj. = BOD, kg/day
MLVSS. kg
Commonly abbreviated F/M Ratio.
HEADER	HEADER
A large pipe to which the ends of a series of smaller pipes are connected. Also called a "manifold."
MANIFOLD	MANIFOLD
A large pipe to which the ends of a series of smaller pipes are connected. Also called a "header."
MEAN CELL RESIDENCE TIME (MCRT)	MEAN CELL RESIDENCE TIME (MCRT)
An expression of the average time that a microorganism will spend in the activated sludge process.
MCRT days = Solids in Activated Sludge Process, lbs
Solids Removed from Process, Iba/day

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10 Treatment Plants
MECHANICAL AERATION	MECHANICAL AERATION
The use of machinery to mix air and water so that oxygen can be absorbed into the water. Some examples are: paddle wheels,
mixers, or rotating brushes to agitate the surface of an aeration tank; pumps to create fountains; and pumps to discharge water
down a series of steps forming falls or cascades.
MICROORGANISMS (micro-ORGAN-is-ums)	MICROORGANISMS
Very small organisms that can be seen only through a microscope. Some microorganisms use the wastes in wastewater for food
and thus remove or alter much of the undesirabfe matter.
MIXED LIQUOR	MIXED LIQUOR
When the activated sludge in an aeration tank is mixed with primary effluent or the raw wastewater and return sludge, this mixture is
then referred to as mixed liquor as long as it is in the aeration tank. When the mixed liquor flows from the aeration tank it goes into
the secondary clarifiers or final sedimentation tanks. Mixed liquor also may refer to the contents of mixed aerobic or anaerobic
digesters.
MIXED LIQUOR SUSPENDED SOLIDS	MIXED LIQUOR SUSPENDED SOLIDS
(MLSS)	(MLSS)
Suspended solids in the mixed liquor of an aeration tank.
MIXED LIQUOR VOLATILE SUSPENDED	MIXED LIQUOR VOLATILE SUSPENDED
SOLIDS (MLVSS)	SOLIDS (MLVSS)
The organic or volatile suspended solids in the mixed liquor of an aeration tank.
NITRIFICATION (NYE-tri-fi-KAY-shun)	NITRIFICATION
A process in which bacteria change the ammonia and organic nitrogen in wastewater into oxidized nitrogen (usually nitrate). The
second-stage BOD is sometimes referred to as the "nitrification stage" (first-stage BOD is called the "carbonaceous stage").
OXIDATION (ox-i-DAY-shun)	OXIDATION
Oxidation is the addition of oxygen, removal of hydrogen, or the removal of electrons from an element or compound. In wastewater
treatment, organic matter is oxidized to more stable substances. The opposite of REDUCTION.
PLUG FLOW	PLUG FLOW
A type of flow that occurs in tanks, basins or reactors when a slug of wastewater moves through a tank without ever dispersing or
mixing with the rest of the wastewater flowing through the tank.
DIRECTION
OF FLOW

PLUG FLOW
POLYELECTROLYTE (POLY-electro-light)	POLYELECTROLYTE
A high-molecular-weight substance that is formed by either a natural or synthetic process. Natural polyelectrolytes may be of
biological origin or derived from starch products, cellulose derivatives, and alignates. Synthetic polyelectrolytes consist of simple
substances that have been made into complex, high-molecular-weight substances. Often called a "polymer."
POLYMER (POLY-mer)	POLYMER
A high-molecular-weight substance that is formed by either a natural or synthetic process. Natural polymers may be of biological
origin or derived from starch products, cellulose derivatives, and alignates. Synthetic polymers consist of simple substances that
have been made into complex, high-molecular-weight substances. Often called a "polyelectrolyte."
PROTOZOA (pro-toe-ZOE-ah)	PROTOZOA
A group of microscopic animals (usually single-celled) that sometimes cluster into colonies.
REDUCTION (re-DUCK-shun)	REDUCTION
Reduction is the addition of hydrogen, removal of oxygen, or the addition of electrons to an element or compound. Under anaerobic
conditions in wastewater, sulfate compounds or elemental sulfur are reduced to odor-producing hydrogen sulfide (H2S) or the
sulfide ion (S~ ). The opposite of OXIDATION.
RISING SLUDGE	RISING SLUDGE
Rising sludge occurs in the secondary clarifiers of activated sludge plants when the sludge settles to the bottom of the clarifier, is
compacted, and then starts to rise to the surface, usually as a result of denitrification.

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Activated Sludge 11
SECCHI DISC (SECK-key)	SECCHI DISC
A flat, white disc lowered into the water by a rope until it is just barely visible. At this point, the depth of the disc from the water
surface is the recorded secchi disc reading.
SEIZING	SEIZING
Seizing occurs when an engine overheats and a component expands so the engine will not run. Also called "freezing."
SEPTIC (SEP-tick)	SEPTIC
This condition is produced by anaerobic bacteria. If severe, the wastewater turns black, gives off foul odors, contains little or no
dissolved oxygen and creates a heavy oxygen demand.
SHOCK LOAD	SHOCK LOAD
The arrival at a plant of a waste which is toxic to organisms in sufficient quantity or strength to cause operating problems. Possible
problems include odors and solids in the effluent. Organic or hydraulic overloads also can cause a shock load.
SLUDGE AGE	SLUDGE AGE
A measure of the length of time a particle of suspended solids has been undergoing aeration in the activated sludge process.
Sludge Age, _ Suspended Solids Under Aeration, lbs or kg
days	Suspended Solids Added, lbs/day or kg/day
SLUDGE DENSITY INDEX (SDI)	SLUDGE DENSITY INDEX (SDI)
This test is used in a way similar to the Sludge Volume Index (SVI) to indicate the settleability of a sludge in a secondary clarifier or
effluent. SDI = 100/SVI. Also see SLUDGE VOLUME INDEX (SVI).
SLUDGE VOLUME INDEX (SVI)	SLUDGE VOLUME INDEX (SVI)
This is a test used to indicate the settling ability of activated sludge (aerated solids) in the secondary clarifier. The test is a measure
of the volume of sludge compared to its weight. Allow the sludge sample from the aeration tank to settle for 30 minutes. Then
calculate SVI by dividing the volume (ml) of wet settled sludge by the weight (mg) of that sludge after it has been dried. Sludge with
an SVI of one hundred or greater will not settle as readily as desirable because it is as light or lighter than water.
SVI = Wet Settled Sludge, ml x 100q
Dried Sludge Solids, mg
STABILIZED WASTE	STABILIZED WASTE
A waste that has been treated or decomposed to the extent that, if discharged or released, its rate and state of decomposition would
be such that the waste would not cause a nuisance or odors.
STEP-FEED AERATION	STEP-FEED AERATION
Step-feed aeration is a modification of the conventional activated sludge process. In step aeration, primary effluent enters the
aeration tank at several points along the length of the tank, rather than all of the primary effluent entering at the beginning or head of
the tank and flowing through the entire tank.
SUPERNATANT (sue-per-NAY-tent)	SUPERNATANT
Liquid removed from settled sludge. Supernatant commonly refers to the liquid between the sludge on the bottom and the scum on
the surface of an anaerobic digester. This liquid is usually returned to the influent wet well or to the primary clarifier.
TOC	TOC
Total Organic Carbon. TOC measures the amount of organic carbon in water.
TURBIDITY METER	TURBIDITY METER
An instrument for measuring the amount of particles suspended in water. Precise measurements are made by measuring how light
is scattered by the suspended particles. The normal measuring range is 0 to 100 and is expressed as Nephelometric Turbidity Units
(NTU's).
TURBIDITY UNITS	TURBIDITY UNITS
Turbidity units, if measured by a nephelometric (reflected light) instrumental procedure, are expressed in Nephelometric Turbidity
Units (NTU). Those turbidity units obtained by other instrumental methods or visual methods are expressed in Jackson Turbidity
Units (JTU) and sometimes as Formazin Turbidity Units (FTU). The FTU nomenclature comes from the Formazin polymer used to
prepare the turbidity standards for instrument calibration. Turbidity units are a measure of the cloudiness of water.

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12 Treatment Plants
VOLUTE (vol-LOOT)	VOLUTE
The spiral-shaped casing which surrounds a pump, blower, or turbine impeller and collects the liquor or gas discharged by the
impeller.
ZOOGLEAL MASS (ZOE-glee-al)	ZOOGLEAL
Jelly-like masses of bacteria found in both the trickling filter and activated sludge processes. These masses may be formed for or
function as the protection against predators and for storage of food supplies. Also see BIOMASS.
(y&fre P&tf-ee)

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Activated Sludge 13
CHAPTER 11. ACTIVATED SLUDGE
VOLUME II. OPERATION OF ACTIVATED SLUDGE PLANTS
(Lesson 1 of 8 Lessons)
NOTE: Review Volume I, Chapter 8, "Package Plants and
Oxidation Ditches" before starting Volume II.
11.0 BASIC VARIABLES AND RECORD KEEPING
11.00	Need for Record Keeping
Wastewater flows and contents change daily. The activated
sludge plant operator attempts to maintain the process at
some balanced state that will be capable of handling the minor
variations in flows or wastewater characteristics and produce
the desired quality of effluent. To accomplish this goal you
must establish the activated sludge process (Fig. 11.1) on
known data and knowledge obtained at other plants and relate
them to your plant. After your plant becomes operational, you
then must relate the control procedures to actual plant experi-
ence. The variations that affect the operation are derived from
two sources: (1)Tfie discRanJers~to" tne collection system and
(2) in-plarTf^eraTiori5n7afraBles~ "
11.01	Variables in Collection System
11.010	Combined Sewer Systems
During storms the treatment plant will receive an increase in
flow which may cause the following problems:
1.	Reduced wastewater time in treatment units (hydraulic
overload);
2.	Increased amounts of grit and silt which lower the volatile
(food) content of the solids;
3.	Increased organic load during initial washout of accumu-
lated sewer deposits; and
4.	Rapid changes in wastewater temperature and solids con-
tent.
11.011	Waste Dischargers to the System
Various industries, businesses, and cesspool or septic tank
service firms can cause uneven flows and changes in the types
of wastewater entering a plant. You should become ac-
quainted with the managers of businesses and facilities whose
discharges could upset your treatment processes. Convince
these people in a friendly manner how vital it is to your plant
processes and the receiving waters for you to be notified of any
potentially harmful discharges. Try to obtain their cooperation
and request them to notify you whenever an accidental spill, a
process change, or a cleaning operation occurs which could
cause undesirable waste discharges. This requires diplomacy
to obtain cooperation from dischargers to regulate their own
discharges and to reduce the number of midnight dumps.
11.012 Maintenance of the Collection System
Advance notice of collection system maintenance crew ac-
tivities can be very helpful. If a lift station has been out of
service for a period of time, large volumes of septic wastewater
could cause a shock load on your treatment processes. Similar
problems could be created when a blockage in a line is cleared
or a new line is connected to the system. Analysis of inflow
quantities and characteristics when these flows reach a treat-
ment plant can indicate whether or not they will cause a seri-
ous problem.
11.02 Operational Variables
Continual review of laboratory test results is essential in de-
termining whether a treatment plant is discharging effluent of
the required quality in terms of such WATER QUALITY INDI-
CATORS AS COD, SUSPENDED SOLIDS, AND NITROGEN.
If the desired quality of the plant effluent is not achieved, the
operator must determine what factor or factors have changed
to upset plant performance and thus reduce efficiency.
Important factors that could have changed include:
1.	Higher COD or BOD load applied to the aerator (influent
load);
2.	More difficult to treat wastes have caused a change in in-
fluent characteristics;
3.	Unsuitable mixed liquor suspended solids concentration in
the aerator;
4.	Lower or higher rate of wasting activated sludge;
5.	Unsuitable rate of returning sludge to the aerator could ad-
versely influence mixed liquor suspended solids;
6.	Higher solids concentrations in digester SUPERNATANT1
returned to the plant flow, or return too rapid;
1 Supernatant (sue-per-NAY-tent). Uquid removed from settled sludge. Supernatant commonly refers to the liquid between the sludge on the
bottom and the scum on the surface of an anaerobic digester. This liquid is usually returned to the influent wet well or to the primary clarifier.

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14 Treatment Plants
treatment pgoae^	function
P££TP£Am£A/r
INFUI6MT
££MOl/£S	04/V£f/4£&£-
0££#/g	7Z>4^4A'£>/r//U., O&AT
PoS6/g/f /&%<& S0Z./0S
K/WS PAr/SO#£A//
-------
Activated Sludge 15
7.	Dropping of oxygen concentration in the aerator below de-
sirable levels; and
8.	Increase or decrease in wastewater temperature.
Examination of plant records should reveal the items which
have changed that could have upset the treatment process.
QUESTIONS
Write your answers in a notebook and then compare your
answers with those on page 82.
11 .OA What two major variables affect the way an activated
sludge plant is operated?
11 .OB What problems can be caused in an activated sludge
plant when excessive storm water flows through the
process?
11 .OC Besides excessive storm water flows, what other vari-
ables in the collection system can affect the operation
of an activated sludge plant?
11.03 Plant Records
Accurate daily plant and laboratory records on the items
listed below can help the operator determine the best oper-
ating ranges for operational controls on the basis of plant per-
formance. Records can also indicate when problems develop
and help identify the source of the problem. RECORD THE
FOLLOWING DATA ON A DAILY BASIS. (Also see Monthly
Data Sheet in the Appendix.)
1.	Suspended Solids and Volatile Content
a.	Primary effluent
b.	Aerator mixed liquor
c.	Return sludge
d.	Final clarifier or secondary sedimentation tank effluent
2.	BOD, COD, or TOC2
a.	Plant influent
b.	Primary effluent
c.	Final clarifier or secondary sedimentation tank effluent
NOTE: COD is recommended to determine the strength of
influent wastewater because the results are available
"within four hours and can be used to control the activated
'sludge process: F6r marty years operators attempted to
use the BOb test for operational control, but the test has
the following disadvantages:
(1)	Procedural errors can cause a large variation in re-
sults.
(2)	Five days of waiting are required before results are
available.
(3)	Only a portion of the load on the activated sludge
process is measured by the test.
3.	Dissolved Oxygen
a.	Aerator
b.	Final clarifier or secondary sedimentation tank (inside
the effluent weir)
c.	Final effluent
4.	Settleable Solids
a.	Influent
b.	Mixed liquor settleability test
c.	Digester supernatant
d.	Final effluent
5.	Temperature
a.	Influent
b.	Aerator
c.	Final effluent
6.	pH
a.	Influent
b.	Primary effluent
c.	Aerator3
d.	Final effluent
7.	Clarity (SECCHI DISC)* or Turbidity (TURBIDIMETER)5
a. Final clarifier
8.	Chlorine Demand
a. Final clarifier effluent
9.	Coliform Group Bacteria6
a. Plant effluent
10.	Meter Readings and Calculations
a.	Daily flow
b.	Pounds of solids under aeration
c.	Pounds of COD or BOD to aerators
d.	Pounds of solids in effluent
e.	Return sludge rate
f.	Waste sludge rate
g.	Air to aerators (diffused air system): hours operated at
various speeds (mechanical aeration)
h.	Sludge age (other similar calculations include Food/
Microorganism Ratio and Mean Cell Residence Time,
(see Sections 11.71 and 11.73)
i.	Pounds of solids in sludge to digester
j. Pounds of solids in digester supernatant
k. Power cost
11.	Daily Observations
a.	Odors
b.	Influent. Color and level of inflow.
c.	Primary clarifier. Scum and color.
d.	Aeration tank. Turbulence, color and amount of sur-
face foam and scum.
e.	Secondary clarifier. Effluent clear or turbid, type of
solids on surface and influent.
2	TOC or Total Organic Carbon. TOC measures the amount of organic carbon in water.
3	Measure aerator pH in the aerator or immediately after sample is collected, because the pH can change very rapidly once the sample is out of
the aerator. Do not take sample to the lab.
4	Secchi Disc (SECK-key). A flat, white disc lowered into the water by a rope until it is just barely visible. At this point, the depth of the disc
from the water surface is the recorded secchi disc reading.
5	Turbidity Meter. An instrument for measuring the amount of particles suspended in water. Precise measurements are made by measuring
how light is scattered by the suspended particles. The normal measuring range is 0 to 100 and is expressed as Nephelometric Turbidity Units
(NTU's).
6	Check with your regulatory agency for test and procedures. Tests approved by agencies include MPN by multiple fermentation tubes,
membrane filter, and fecal coliform.

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16 Treatment Plants
f.	Return activated sludge. Color and odor.
g.	Equipment and motors. Smooth operation, vibrations,
noises and temperature.
h.	Condition of receiving water upstream and downstream
from point of discharge.
f Accurate records will show when you have established\
| operating procedures that will produce the best possible ]
I effluent. This effluent will be low in COD (or BOD) and sus-/
pended solids, and the effluent clarity will be good. Waste
loadings and operational procedures will change frequently
due to seasonal changes. This requires the operator to con-
stantly review the plant records for changes and to make ap-
propriate changes to maintain the best possible effluent qual-
ity. Process control consists not only of maintaining the equip-
ment, but of making a constant daily review of process condi-
tions to determine when adjustments must be made to com-
pensate for the many variables that can influence effluent qual-
ity. Remember that the sight, smell, and touch observations
often are your first indications that problems are developing
and frequently offer indications of appropriate corrective ac-
tion.
QUESTIONS
Write your answers in a notebook and then compare your
answers with those on page 82.
11,0D Why should the strength or waste load of the influent
to the activated sludge process be measured by the
COD test instead of the BOD test?
11,0E Why should the aerator pH be measured in the aerator
instead of the lab?
11 .OF Sight and smell observations are often the operator's
first indication that process problems are developing.
True or False?
11.04	Typical Lab Results for an Activated Sludge Plant
Typical results of lab tests (Table 11.1) for an activated
sludge plant are provided to assist in the evaluation of lab
results and plant performance. Remember that every plant is
different and is influenced by different conditions.
11.05	Design Variables
Several different types of activated sludge plants have been
built using various flow arrangements, tank configurations, or
oxygen application equipment. However, all of these variations
are essentially modifications of the basic concept of conven-
tional activated sludge.
11.050 Aeration Methods
Two methods are commonly used to supply oxygen from the
air to the bacteria — MECHANICAL AERATION and DIF-
FUSED AERATION. Both methods are mechanical processes
with the difference being whether the mechanisms are at or in
the aerator or at a remote location.
Mechanical aeration devices agitate the water surface in the
aerator to cause spray and waves by paddle wheels (Fig.
TABLE 11.1 TYPICAL LAB RESULTS
Test	Location	Common Range
COD
Influent
Primary Effluent
Final Effluent
(Conv. Act. SI.)
300 - 700
200 - 400
30-70
mg/L
mg/L
mg/L
BOD
Influent
Primary Effluent
Final Effluent
(Conv. Act. SI.)
150 - 400
100-280
10-20
mg/L
mg/L
mg/L
SUSPENDED
SOLIDS
Influent
Primary Effluent
Mixed Liquor
Return Sludge
Final Effluent
(Conv. Act. SI.)
150 - 400
60-160
1000-4500
2000- 10,000
1 -20
mg/L
mg/L
mg/L
mg/L
mg/L
DISSOLVED
OXYGEN
Mixed Liquor
Final Effl. (Outfall)
0.5-4
2-6
mg/L
mg/L
CHLORINE
RESIDUAL
(30 min.)
Final Effluent
<0.1 -2.0
mg/L *
COLIFORM
GROUP
BACTERIA, MPN
Final Effluent
(Chlorinated)
2-700/100 ml
CLARITY
(Secchi Disc)
Final Effluent
3-8 ft

TURBIDITY
(Turbidimeter)
Final Effluent
1 - 3 NTU

PH
Influent
Effluent
6.8-8.0
6.9-8.5

* Regulatory agencies normally specify a chlorine residual remaining
after a certain time period.
< Means less than. For example, less than 0.1 mg/L chlorine re-
sidual.
11.2),	mixers, rotating brushes, or some other method of
splashing water into the air or air into the water where the
oxygen can be absorbed.
Mechanical aerators in the tank tend to be lower in installa-
tion and maintenance costs. Usually they are more versatile in
terms of mixing, production of surface area of bubbles, and
oxygen transfer per unit of applied power.
Diffused air systems use a device called a diffuser (Fig.
11.3)	which is used to break up the air stream from the blower
system into fine bubbles in the mixed liquor. The smaller the
bubble, the greater the oxygen transfer due to the greater sur-
face area of rising air bubbles surrounded by water. Unfortu-
nately, fine bubbles will tend to regroup into larger bubbles
while rising unless broken up by suitable mixing energy and
turbulence.
11.051 Variation of Activated Sludge Process
The activated sludge plant may be operated in any one of
three ranges or operational zones on the basis of "SLUDGE
AGE"7 which is an expression of pounds of organic loading
7 Sludge Age, days = (Suspended Sol. In Mixed Liq., mg/L) (Aerator Vol., MG) (8.34 lbs/gal)
(Suspended Sol. in Primary Effl., mgIL) (Flow, MGD) (8.34 Ibslgal)
Suspended Solids Under Aeration, lbs
Suspended Solids Added, Ibslday

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Activated Sludge 17
Fig. 11.2 Mechanical aeration device
(Courtesy INFILCO INC.)

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18 Treatment Plants
Fig. 11.3 Air diffuser (fine bubbles)
(Courtesy Paul Hallbach, National Training Center, Water Quality Office/EPA)

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Activated Sludge 19
added per day per pound of organisms maintained in the par-
ticular process. Sludge age is a control guide that is widely
used and is an indicator of the length of time a pound of solids
is kept under aeration in the system. If the amount of solids
under aeration remains fairly constant, then an increase in the
influent solids load will decrease the sludge age. Use of this
measure of sludge age is recommended for the new activated
sludge plant operator because of the ease in understanding
this approach. The experienced operator may not accept this
method of control because it ignores the soluble BOD that is
related to the solids production but not measured by sus-
pended solids tests on the influent.
The following values are typical sludge ages for different
types of municipal activated sludge plants with very little indus-
trial waste. Actual loadings must be related to the type of waste
and local situation.
1.	HIGH-RATE. A high-rate activated sludge plant operates at
the highest loading of food to microorganisms; the sludge
age ranges from 0.5 to 2.0 days. Due to this higher loading,
the system produces a lower quality of effluent than the
other types of activated sludge plants. This system is more
easily upset than others and requires tighter control and
frequent testing.
2.	CONVENTIONAL. Conventional activated sludge plants are
the most common type in use today. The loading of food to
microorganisms is approximately 50 percent lower than in a
high-rate plant, and the sludge age ranges from 3.5 to 7.0
days. This method of operation produces a high quality of
effluent and is able to absorb some shock loads without
lowering effluent quality.
3. EXTENDED AERATION. Extended aeration is often used in
smaller package-type plants (Chapter 8) or so-called com-
plete oxidation systems. These are the most stable of the
three processes due to the light loading of food to mi-
croorganisms, and the sludge age is commonly greater
than ten days. Effluent suspended solids commonly are
higher than found under conventional loadings.
For a summary of the loadings for different types of activated
sludge processes, see Table 11.2.
There are other variations of activated sludge processes
such as contact stabilization, step-feed, Kraus and complete
mix which are discussed in Section 11.9.
QUESTIONS
Write your answers in a notebook and then compare your
answers with those on page 82.
11,0G List two methods of supplying oxygen from air to bac-
teria in the activated sludge process.
11 .OH Write the formula for calculating sludge age.
TABLE 11.2 AERATION TANK CAPACITIES AND PERMISSIBLE LOADINGS*
PROCESS
AERATION TANK ORGANIC
LOADING - lb. BOD5/day
per 1000 cu. ft.b
F/M Ratio
lb. BODs/day
per lb. MLVSS0
MLSS*
mg/llter
Conventional
Step Aeration
Complete Mix
40
0.2 - 0.5
1000 - 3000
Contact Stabilization
so-
0.2 - 0.6
1000 - 3000
Extended Aeration
Oxidation Ditch
is
0.05 - 0.1
3000 - 5000
* MLSS values are dependent upon the surface area provided for sedimentation and the rate of sludge return as well as the aeration process.
** Total aeration capacity, includes both contact and reaeration capacities. Normally the contact zone equals 30 to 35% of the total aeration
capacity.
a RECOMMENDED STANDARDS FOR SEWAGE WORKS (10 STATE STANDARDS), Great Lakes-Upper Mississippi River Board of State
Sanitary Engineers, 1978 Edition, published by Health Education Service, P.O. Box 7126, Albany, New York 12224. Price, $1.75 plus 59' for
shipping and handling charges.
b lb BOD/day per 1000 cu ft x 16.02 = gm/day per cu m = kg/day per 1000 cu m
c lb BOD per day/lb MLSS = kg BOD per day/kg MLSS
m OF L&&0H 1 QtyU&OM
Activate? *
Please answer the discussion and review questions before
continuing with Lesson 2.

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20 Treatment Plants
DISCUSSION AND REVIEW QUESTIONS
Chapter 11. ACTIVATED SLUDGE
(Lesson 1 of 8 Lessons)
At the end of each lesson in this chapter you will find some
discussion and review questions that you should work before
continuing. The purpose of these questions is to indicate to you
how well you understand the material in the lesson.
Write the answers to these questions in your notebook be-
fore continuing. Write the numbers for the correct answers to
question 1 on your answer sheet in your notebook.
1. During storms an activated sludge plant will receive an in-
creased inflow which may cause the following problems:
1.	Dilution of wastes which makes them easy to treat,
2.	Reduced wastewater time in treatment units,
3.	Increased amounts of grit and silt,
4.	Increased organic loading, and
5.	Fluctuating wastewater temperatures.
Which possible answers are correct?
2.	How can the operator attempt to reduce problems caused
by waste discharges into the collection system?
3.	How can maintenance activities in a collection system
cause operational problems in an activated sludge treat-
ment plant?
4.	What can the operator determine from laboratory test re-
sults on the plant effluent?
5.	What are some of the disadvantages of using the BOD test
for operational control?
6.	The operator of an activated sludge plant must constantly
review plant records and make appropriate changes to ac-
count for seasonal changes. True or False?
7.	What is the difference between mechanical aeration and
diffused aeration?
CHAPTER 11. ACTIVATED SLUDGE
OPERATION OF ACTIVATED SLUDGE PLANTS
(Lesson 2 of 8 Lessons)
11.1 AERATION SYSTEMS
11.10	Purpose of Aeration
Aeration serves the dual purpose of providing dissolved
oxygen and mixing of the mixed liquor and wastewater in the
aeration tank. Two methods are commonly used to disperse
oxygen from the air to the microorganisms — MECHANICAL
AERATION and DIFFUSED AERATION. Oxygen also may be
provided to the microorganisms by PURE OXYGEN systems
(see Chapter 21, Volume III).
11.11	Mechanical Aeration Systems
Surface aerators use a motor-driven rotating impeller (Fig.
11.4) or a brush rotor (Volume I, Chapter 8, Fig. 8.11). Both
devices splash the mixed liquor into the atmosphere above the
aeration tank. Oxygen transfer to the mixed liquor is achieved
by this method of aeration as the mixed liquor passes through
the atmosphere. Surface aerators either float (for use in aer-
ated ponds) or are mounted on supports in or above an aera-
tion basin. In ponds they are equipped with draft tubes to im-
prove their mixing characteristics.
A surface aerator's oxygen transfer efficiency is stated in
terms of oxygen transferred per motor horsepower per hour.
Typical oxygen transfer efficiencies are about two to three
pounds of oxygen per hour per motor horsepower (1.2 to 1.8
kg/hr/kW). The oxygen transfer efficiency increases as the
submergence of the aerator is increased. However, power
costs also increase because more power is required to move
the aerator impeller or agitator through the mixed liquor due to
greater submergence and increased load on the drive motor.
The turbine aerator (Volume III, Chapter 21) is another type
of motor-driven mechanical aerator. Turbine aerators are fre-
quently used in the complete mix or pure oxygen activated
sludge process. An outside source of air is supplied to the
aerator, usually from a blower or oxygen-generating system.
Turbine aerators are more efficient and use less horsepower
than standard surface aerators because the extra air supply
creates turbulence in the immediate area of the rising air bub-
bles.
11.12 Diffused Aeration Systems
Diffused aeration systems are the most common type of
aeration system used in the activated sludge process. A dif-
fuser breaks up the air stream from the blowers into fine bub-
bles in the mixed liquor. The aeration tank distribution system
consists of numerous diffusers attached to the bottom of air
HEADERS8 and located near the bottom of the aeration tank.
Diffusers located in this position maximize the contact time of
the air bubbles with the mixed liquor. Also, this location en-
courages mixing and discourages deposits on the tank bottom.
Although diffused aeration is used in the aeration tanks of
activated sludge plants, it may also be found in aerated grit
chambers, pre-aeration systems, aerated flow channels, and
return sludge wet well aeration.
8 Header. A large pipe to which the ends of a series of smaller pipes are connected. Also colled a "manifold."

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Activated Sludge
1
-J.

¦ m ¦ ¦¦
	C
1.,
T"
¦, j— — i
%

Fig. 11.4 Bridge mounted surface aerators. Motor, gear
reducer and impeller shown
(Courtesy of Chino Basin Municipal Water District)

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22 Treatment Plants
11.120	Air Filters
Filters (Fig. 11.5) remove dust, dirt, and grease from air
before it is compressed and sent to the various plant pro-
cesses. Clean air is essential for the protection of:
1.	Blowers
a.	Large objects entering the impellers or lobes may
cause severe damage.
b.	Deposits on the impellers or lobes reduce clearances
and cause excessive wear and vibration problems.
2.	Process systems
a.	Clean air is required by downstream equipment.
b.	Clean air prevents fouling of air conduits, pipes, tubing
or dispersing devices on diffusers.
The filters may be constructed of a fiber mesh or metal mesh
material that is sandwiched between a screen material and
encased in a frame. The filter frames are then installed in a
filter chamber.
The process air is usually drawn directly from the atmos-
phere. Some treatment plants have pre-treatment and primary
treatment process tanks covered for odor control. In plants of
this type, odorous air is also drawn from under these covered
tanks.
11.121	Blowers (Process Air Compressors) (Figures 11.6
and 11.7)
Blowers are of the positive displacement type or the cen-
trifugal type that provide air to the various plant processes
through a diffuser system. Usually positive displacement blow-
ers operate at low RPMs and produce less than 20,000 CFM
(570 cu m/min) while centrifugal blowers operate at high RPMs
and produce from 20,000 to 150,000 CFM (570 to 4300 cu
m/min).
POSITIVE DISPLACEMENT BLOWERS
The positive displacement blower (Fig. 11.8) provides a
constant volume (cubic feet or cubic meters) output of air per
revolution of the rotors or lobes. Blower output is varied by
changing rotor or lobe speed (Revolutions Per Minute). The
higher the RPM, the greater the air output. Usually output from
positive displacement blowers ranges from 100 to 2,000 cubic
feet per minute (cfm) (3 to 57 cu m/min). They are installed to
be operated at a fixed volume output and directly driven by
electric motors through direct couplings or sheaves and belts.
Changes in air volume may be accomplished by changing
sheaves to increase or decrease blower rotor or lobe rotation
(RPM), thus increasing or decreasing air output.
Large positive displacement blowers (2,000 to 20,000 CFM
or 57 to 570 cu m/min) also may be driven by internal combus-
tion engines or variable speed electric motors in order to
change blower volume outputs as required in activated sludge
plants. By increasing or decreasing engine or motor RPM, the
positive displacement blower output can be increased or de-
creased.
The air lines are connected to the blower through a flexible
coupling in order to keep vibration to a minimum and to allow
for heat expansion. When air is compressed, heat is gener-
ated, thus increasing the discharge temperature as much as
100 degrees F (56°C), or more.
A check valve follows next which prevents the blower from
operating in reverse should other blowers in the same system
be operating while this blower is off.
The discharge line from the blower is equipped with an air
relief valve which protects the blower from excessive back-
pressure and overload. Air relief valves are adjusted by
weights or springs to open when air pressure exceeds a point
above normal operating range, around 6.0 to 10.0 psi (0.4 to
0.7 kg/sq cm) in most wastewater treatment plants.
An air discharge silencer is also installed to provide DEC-
IBEL0 noise reduction. Ear protective devices should be worn
when working near noisy blowers.
The impellers are machined on all exterior surfaces for
operating at close tolerances; they are statically and dynami-
cally balanced. Impeller shafts are made of machined steel
and are securely fastened to the impellers. Timing gears accu-
rately position the impellers.
Lubrication to the gears and bearings is maintained by a
lube oil pump driven from one of the impeller shafts. An oil
pressure gage monitors the system oil pressure. An oil filter is
located in the oil sump to insure that the oil is free from foreign
materials. An oil level is maintained in the gear housing so that
gears and bearings will receive splash lubrication in case of
lube oil pump failure. Air vents are located between the seals
and the impeller chamber to relieve excessive pressure on the
seals.
CENTRIFUGAL BLOWERS
The centrifugal blower (Fig. 11.9) is a motor to speed-
increasing gear driven blower that provides a variable air out-
put. Minimum through maximum air output is controlled by
guide vanes, which are located on the intake side of the blower
and are normally positioned manually by operating personnel.
In many plants they also are controlled by plant instrumenta-
tion by either dissolved oxygen levels in the aeration tanks or
by plant influent flows.
The blower consists of an impeller, VOLUTE'10 casing, shaft
and bearings, speed-increasing gear box, and an electric
motor or internal combustion engine to drive the unit. Air enters
the volute casing through an inlet nozzle and is picked up by
the whirling vanes of the impeller where it is hurled by cen-
trifugal force into the volute casing. Air enters the volute in its
smallest section and moves in a circular motion to the largest
section of the volute where it is discharged through the dis-
charge nozzle.
Air lines are connected to the blower through flexible cou-
plings in order to keep vibration to a minimum and to allow for
heat expansion. The air suction line is usually equipped with a
manually operated butterfly valve. Air bypass and discharge
valves are usually electrically or pneumatically operated.
The impeller is machined on all surfaces for operating at
close tolerances and is statically and dynamically balanced.
The impeller shaft is supported in a shaft bearing stand which
contains a thrust bearing and journal bearings.
9 Decibel. A unit for expressing the relative intensity of sounds on a scale from zero for the average least perceptible sound to about 130 for
the average pain level.
,0 Volute (vol-LOOT). The spiral-shaped casing which surrounds a pump, blower, or turbine impeller and collects the liquid or gas dis-
charged by the impeller.
i

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Activated Sludge 23
Grease filters at a primary sedimentation inlet channel
Dust and dirt filters in a filter chamber
1.	Filter elements
2.	Filter chamber
3.	Filter chamber inlet pressure tube to manometer or water
column gage
4.	Filter chamber outlet pressure tube to manometer or water
column gage
Manometer on a filter chamber (not a U-tube manometer)
reading inches of pressure difference
Fig. 11.5 Air Filters

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24 Treatment Plants
1. Air enters the compressor at the left and leaves at the right.
2. As the rotors turn away from each other on the inlet side, air
is drawn into pockets formed between the rotors and the
casing wall.
3. The pockets of air along and around the rotor axes, then
join and diminish in volume, thus compressing the air. The
air flow is smooth and continuous, without pumping or surg-
ing.
Fig. 11.6 How a rotary positive-displacement compressor
works
(Permission of Chicago Pump)

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Activated Sludge
Timing gears synchronize
the rotors and maintain
close tolerances.
Non-rubbing labyrinth seals
at each end of both rotors
control outleakage.
Helical rotors
Oil is force-fed to all gears
and bearings by a built-in
gear pump.
Slingers are used to keep
oil out of the compression
chamber.
Anti-friction bearings.
Fig. 11.7 Cut-away view of rotary positive-displacement
compressor
(Permission of Chicago Pump)

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26 Treatment Plants
1.
motor
2.*
belts
3.*
sheaves
4.*
air line (suction)
5.
air line (discharge)
6.
flexible coupling
7.
check valve
8.
air relief valve
9.
air discharge silencer
10.*
impellers
11.
lube oil pump
12.
oil pressure gage
13.
oil filter
14.
oil level indicator and reservoir
15.
oil seal air vents
16.
inlet valve
17.*
discharge valve
18.
oil temperature gage
19.
belt guard
* Not marked on photos
Fig. 11.8 Positive displacement blower


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Activated Sludge 27
1.	impeller casing
2.	motor
3.	speed increasing gears
4.	guide vanes
5.	intake nozzle
6.	discharge nozzle
7.	flexible coupling
8.	manual suction line valve
9.	bypass valve
10.	discharge valve
11.	bearing stand
12.	main oil pump
13.	auxiliary oil pump
14.	oil reservoir
15.	couplings
Fig. 11.9 Centrifugal blower

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28 Treatment Plants
Lubrication to the bearings and gears is maintained by a
positive displacement main oil pump that is driven by the
speed-increasing gear unit. An auxiliary electrically operated
centrifugal oil pump also is used to provide oil pressure in the
event of failure of the main oil pump and to lubricate the blower
shaft bearings before start-up and after shutdown. The oil re-
servoir is located in the blower baseplate. Cartridge type or
disc-and-spacer type oil filters are provided to insure the oil to
be free of foreign materials. The selection of either type filter is
based on the degree of filtration required.
Due to the very high speeds at which these blower units
operate and resultant high oil temperatures, an oil cooler unit is
installed. This unit, in most cases, is a shell and tube, oil-to-
water heat exchanger.
11.122	Air Distribution System
The air distribution system consists of pipes, valves, and
metering devices that deliver air from the blowers to air head-
ers in the aeration tanks and other plant processes (Fig.
11.10).
An air metering device should be located in a straight section
of the air main on the discharge side of the blower. This device
consists of an orifice plate inserted between two specially
made pipe flanges. The orifice plate is made of stainless steel
with a precision hole cut through the center. The diameter of
the hole will vary according to the flow rates to be measured.
The plate is made of Vs-inch (3 mm) thick material and is
slightly larger than the inside diameter of the pipe. A rectangu-
lar shaped handle is attached to the plate. The plate is installed
between the flanges, blocking the pipeline except for the hole
in the center of the plate. One side is bevelled, leaving a sharp
edge on the opposite side. The handle of the orifice plate will
have numbers stamped into it giving the orifice size. These
numbers on the handle are stamped on the same side as the
sharp edge of the orifice opening. When viewing the plate to
read the numbers, the blower should be behind you. THE
SHARP EDGE OF THE PLATE AND THE NUMBERS MUST
BE ON THE SIDE TOWARD THE BLOWER FOR THE METER
TO OPERATE PROPERLY.
On fop of each pipe flange holding the orifice plate will be a
hole tapped and connected to tubing leading to the instrument
which indicates the rate of air flow. There may be more than
one orifice plate and metering device in the distribution system
to monitor the air to the various plant processes.
Condensate traps are located at each meter and at the low-
est point(s) of the distribution system.
11.123	Air Headers
Air headers are located in or along the aeration tank and are
connected to the air distribution system from which they supply
air to the diffusers. The two most common types of air headers
are the swing header and the fixed header.
The swing header is a pipe with a distribution system con-
nector fitting, a valve, a double pivot upper swing joint, upper
and lower riser pipes, pivot elbow, leveling tee, and horizontal
air headers. An air blow-off leg, as an extension of the lower
tee connection, is fabricated with multiple alignment flanges,
gaskets, and jack screws for leveling of the header.
The swing joint and pivot elbow allow the header to be raised
from the aerator with an electric or manual hydraulic hoist so
the header or diffusers may be serviced (Fig. 11.11).
The fixed header is a pipe with a distribution system connec-
tor fitting, a valve, a union, a riser pipe, horizontal air headers,
and header support "feet." These headers are generally not
provided with adjustable leveling devices, but rely on the fixed
leveling afforded by the "feet" attached to the bottom of the
horizontal air headers.
Raising and lowering the air header is accomplished by
manually lifting and lowering the header from or to the aerator.
The fixed header is commonly found in package plants,
channel aeration, and grit chamber aeration (Fig. 11.12).
Header valves are used to adjust the air flow to the header
assembly and to secure the air to the assembly when servicinq
the header or diffusers.
Headers are designed for a maximum air flow in cubic feet
per minute at a total maximum head loss measured in inches
(or millimeters) of water.
11.124 Diffusers
Two types of diffusers are commonly in use today, fine bub-
ble diffusers and coarse bubble diffusers. Fine bubble diffusers
are commonly porous nylon or dacron socks, and fiberglass- or
saran-wrapped tubes (Fig. 11.13). Fine bubble diffusers are
easily clogged because these diffusers are self sealing from
the inside if dirty air is pumped into them. They may clog from
the outside due to biological growths. These diffusers typically
have an oxygen transfer efficiency of around six percent or
more.
Coarse bubble diffusers are generally made of plastic and
are of various shapes and sizes (Fig. 11.14). Although these
types of diffusers have lower oxygen transfer efficiencies
(about three percent), they are lower in cost and relatively
maintenance free.
In most applications many of the same type diffusers are
mounted to the horizontal air header. The number of diffusers
mounted to the air header is determined by the desired mixing
(diffusion pattern), and oxygen transfer requirements desired
for the aeration tank (Fig. 11.15).
QUESTIONS
Write your answers in a notebook and then compare your
answers with those on page 82.
11.1A What are the purposes of aeration?
11.1B Why are diffusers located near the bottom of the aera-
tion tank?
11.1C How are the guide vanes positioned that control air
output from centrifugal blowers?
11.1D Why are fine bubble diffusers easily clogged?
11.2 SAFETY
ALWAYS READ THE MANUFACTURERS' MANUALS AND
THOROUGHLY UNDERSTAND THEM BEFORE OPERATING
OR MAINTAINING ANY PIECE OF EQUIPMENT.
11.20 Aeration Tanks and Clarifiers
Whenever you must work around aeration tanks and clarifi-
ers, use safe procedures and exercise extreme caution at all
times.
1. Wear shoes with soles that retard slipping. Cork-inserted
composition soles provide the best traction for all-around
use.

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Activated Sludge
Air distribution piping entering "Y" wall of a large
activated sludge plant.
1.	orifice plate between pipe flanges
2.	meter tubing
3.	meter
4.	air headers
5.	air regulating/isolation valve
6.	condensate traps
7.	meter manifold valves
8.	meter air supply tubing take-off valves
9.*	header valves
'Not marked on photos
Air distribution piping in the "Y" wall of a large activated
sludge plant connected to air headers.
Fig. 11.10 Air distribution piping

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30 Treatment Plants

Air headers

Swing header
Air distribution piping and air headers
1.	distribution system connector fittings
2.	valve; regulating and isolation
3.	double pivot upper swing joint
4.	upper riser pipe
5.	lower riser pipe
6.	pivot elbow
7.	leveling tee
8.	horizontal air header
9.	air blow-off leg
10.	hoist
Fig. 11.11 Swing headers

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Activated Sludge
¦¦K.> l|!Ur. „ Jr* ! ¦
¦¦km :sss,s5 ~ - r
Air header (grit chamber)
Air headers (package plant)
%
1.	distribution system connector fitting
2.	header valve; regulating/isolation
3.	union
4.	riser pipe
5.	horizontal air header
6.	diffuser
Air header (channel aeration)
Fig. 11.12 Fixed header

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Treatment Plants
1.	sock support frame and threaded header mount
2.	sock to support frame clamp
3.	porous sock (air comes out between ends indicated by
rows)
Nylon sock
1 header mounting hole (fastening bolt not shown)
2. porous fiberglass (air comes out between ends indicated by
arrows)
Fiberglass wrapped tube
Fig. 11.13 Fine bubble diffusers

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Activated Sludge 33
:
1.	threaded stub for header mounting	1. threaded stub for header mounting
2.	air outlet orifices, four	2. air outlet orifices, four
3. air deflector crown
1.	air inlet and header mounting surfaces
2.	air outlet orifices, eight
3.	plunge tubes
Fig. 11.14 Coarse bubble diffusers

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34 Treatment Plants
-	... .Till
Narrow band pattern
(Diffusers installed on only one side of air header)
Wide band pattern
(Diffusers on both sides of air headers)
Fig. 11.15
Diffuser patterns

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Activated Sludge 35
2.	Wear a life jacket when working around an aeration tank.
Falling into an aeration tank when air is being injected is
almost certain to result in drowning unless a life jacket is
worn.
3.	Slippery algal growths should be scrubbed and washed
away whenever they appear on walkways.
4.	Keep the area clear of spilled oil or grease.
5.	Oo not leave tools, equipment and materials where they
could create a safety hazard.
6.	Adequate lighting should be permanently installed for night
work, especially for use during emergencies.
7.	Ice conditions in winter may require spiked shoes and icy
areas should be sanded if ice cannot be thawed away with
wash water.
8.	Remove only sections of handrails necessary for the im-
mediate job. Removed sections should be properly stored
out of the way and secured against falling.
11.21	Surface Aerators
If maintenance or repair is required on the aerator, the
aerator must be shut down and the MAIN POWER BREAKER
MUST BE SHUT OFF, LOCKED OUT AND PROPERLY
TAGGED. The lock out should be accomplished with a padlock
and you should keep the key in your pocket. Tag the breaker
with a lock-out tag and note the date the aerator was locked
out, the reason for the lock out, and the name of the person
who locked out the aerator.
If an electrical problem exists with the aerator drive, ONLY
QUALIFIED ELECTRICIANS should be allowed to troub-
leshoot and repair the problem. Serious damage has occurred
to equipment and to non-qualified people who were "just trying
to fix it."
Surface aerators are located directly over the aeration basin
and caution is required when working in that area. If the basin
is empty, a 15- to 40-foot (4.5 to 12 m) fall could be fatal. When
the basin is full of water you could drown if you fell into the
water. Whenever any work must be done on a surface aerator
over a basin, the work should be done by two persons wearing
life preservers or life lines.
11.22	Air Filters
Shut down and secure the blower system when cleaning the
filters if you don't have two separate air filter systems on your
blower system. A 30- to 60-minute shutdown will not adversely
affect the aerated processes. Don't take chances by trying to
operate the blower system while cleaning the filters if you can't
bypass the filters being cleaned. If the blowers are operating
while tying to remove or install filters, foreign material can be
drawn into the filter chamber and ultimately into the blower unit
where extensive damage to the blower will result.
Wear gloves when removing and installing filters to protect
your hands from cuts. Safety glasses or goggles should be
worn when cleaning the filters to keep foreign matter out of
your eyes. A dust and mist mask/respirator should be worn to
prevent ingestion of filter dust through your nose and mouth.
11.23	Blowers
Before starting any blower, be sure all inlet and discharge
valves are open throughout the system. Remove all foreign
matter that might enter the blower. All personnel must be clear
of the blower before starting. Always wear appropriate ear pro-
tection when working near an operating blower. Whenever a
blower must be shut down for maintenance or repair, be sure
the main power breaker is SHUT OFF, LOCKED OUT AND
PROPERLY TAGGED. If an electrical problem exists with the
blower drive motor, only QUALIFIED AND AUTHORIZED
ELECTRICIANS should be allowed to troubleshoot and repair
the problem.
11.24	Air Distribution System
The aeration tank areas where the distribution piping is lo-
cated are hazardous and caution is required when working on
distribution systems. If the aeration tank or channel is empty, a
10- to 20-foot (3 to 6 m) fall could be fatal. When the aeration
tank or channel is full of water you could drown if you fell into
the water. When working on air distribution system piping near
an aeration tank or channel, have at least two operators pre-
sent and have everyone wear a life preserver or life line.
11.25	Air Headers and Diffusers
Air headers are located in areas with hazards similar to
those encountered when working on the air distribution sys-
tem. Exercise care to avoid falling into empty tanks or tanks full
of wastewater.
Before using an electric or manual hydraulic hoist, become
fully familiar with all of the electric and hydraulic controls. The
hydraulic fluid flow-control valve must be adjusted to allow the
header lifting arm to descend at a safe rate of speed. Descend-
ing too fast could be hazardous.
Other cautions that should be observed when using the hoist
include:
1.	Never lift or lower a header pipe until you are sure the hoist
is firmly and properly anchored. If it is not, the hoist may
jackknife into the tank when lifting or lowering starts and
you could be knocked into the tank.
2.	Never lift or lower a header pipe until the double pivot upper
swing joint locking pin is removed. Lifting or lowering the
header with the locking pin in place will cause the pivot to
crack.
3.	Make sure that the hoist support foot transmits the load to
the concrete tank structure and not to the removable deck-
ing. This decking is designed to support only a few hundred
pounds of weight.
4.	Use the double pivot upper swing joint locking pin to secure
the header assembly above the walkway. Failure to do this
will result in the header assembly lowering itself into the
tank if the hoist hydraulic system fails.
QUESTIONS
Write your answers in a notebook and then compare your
answers with those on pages 82 and 83.
11.2A What precautions must be taken before attempting to
maintain or repair a surface aerator?
11.2B What information should be on a lock-out tag?
11 2C What precautions should be taken when working with
blowers?
W OfLf&QH 2 0F6U&0N4
Please answer the discussion and review questions before
continuing with Lesson 3.
ACTIVATE hUXQW

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36 Treatment Plants
DISCUSSION AND REVIEW QUESTIONS
Chapter 11. ACTIVATED SLUDGE
(Lesson 2 of 8 Lessons)
Write the answers to these questions in your notebook be-
fore continuing. The problem numbering continues from Les-
son 1.
8.	What happens to power costs when the submergence of a
surface aerator is increased and why?
9.	Why is clean air essential for the protection of blowers and
process systems?
10. Why should you always read the manufacturers' manuals
and thoroughly understand them before operating or main-
taining any piece of equipment?
11.	What can happen to blowers if someone attempts to re-
move or install the air filters while the blowers are running?
12.	What safety precautions must be taken when removinq
cleaning and installing air filters?
13.	What hazards could be encountered while working on air
headers?
CHAPTER 11. ACTIVATED SLUDGE
OPERATION OF ACTIVATED SLUDGE PLANTS
(Lesson 3 of 8 Lessons)
11.3 CHECKING OUT ANEW PLANT
The section outlines the steps you should follow when
checking out a new plant. The descriptions are based on a
particular typical type of plant layout (Volume I, Fig. 8.4). Your
plant may vary from this plant; but by following this outline and
obtaining assistance during checkout from the design engineer
and representatives of the equipment manufacturers, many
initial operating problems can be eliminated.
11.30 A New Activated Sludge Plant: Description
Imagine that your primary treatment plant has just been ex-
panded to a diffused air activated sludge plant. You will con-
tinue to use your old screens, grit channel, and primary
clarifiers. The new aeration tank is 100 feet (30 m) long, 45 feet
(13.5 m) wide, and 16.5 feet (5m) deep, and has a "Y" wall
dividing it down the center. AIR HEADERS are located along
the full length of the tank on each side of the "Y" and spaced
approximately 10 feet (3 m) apart. Air bubbles come out at the
bottom of the tank through the headers equipped with diffusers
(Figs. 11.3, 11.11, and 11.12). Drawings of the aeration tank
and secondary clarifier are provided in Fig. 11.16.
The new secondary clarifier is circular with an 80-foot (24 m)
inside diameter and a 12-foot (3.7 m) side wall depth sloping
from the wall to the center of the tank. The tank is equipped
with a sweep mechanism fitted with suction devices to collect
the sludge after it has settled.
The resident engineer informs you that the contractor has
completed the work and the new system may be put into serv-
ice. First item on the agenda is to completely recheck the
equipment and structures. Normally the contractor and the
construction inspector are charged with this responsibility, but
many times important items are overlooked due to time
schedules, negligence or oversight.
There is nothing more disappointing than starting a new
plant and having to shut down after two or three days because
of some small item that would have required only an hour or so
to correct on a preliminary checkout. When each item is
checked, be sure that you know what it is supposed to do, how
it is done, and how to service it correctly and safely. If possible,
have a contractor or manufacturer's representative present
during checkout and start-up. When each item of equipment is
examined, check your manual of instructions to be sure your
equipment is discussed. Start NOW with an orderly file on each
piece of equipment if you have not already started.
11.31 Aerator
11.310 Control Gates
In Fig. 11.16 (Plan) there are four storm flow gates (S) and
four pedestal lift gates (P). The storm flow gates are marked by
rectangles and the pedestal gates by circles. Open and close
the gates even if it does permit the entry of some wastewater
and check them for ease of operation and access. They must
travel smoothly with no binding or jumping during opening and
closing. Now is the time to check your means of noting the gate
or valve location in the open, closed, or partially opened posi-
tion. If you don't have a rising stem or other visible indicator of
valve position, count the valve turns and record.
When you have the gates open, check the aerator influent
line or channel for debris such as rocks, sand, timber, waste
concrete, or other foreign material. Short pieces of 2 x 4 boards
and other form-lumber can suddenly appear during initial flow
and this material can jam a pump or stall a clarifier mechanism.
After the line or channel is clean, close the gate, making sure
there is no foreign material along the side guides and DOGS.11
When the gate closes, be sure it is properly seated.
11 Dogs. Wedges attached to a slide gate and frame that force the gate to seal tightly.

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Activated Sludge 37
<8>

T5	O	O	O	O	C	cr
2 s
EJ S-3
g S-4
S 	
P-1, 2, 3 and 4 are
pedestal lift gates
S-1, 2, 3 and 4 are
storm flow gates
S SPRAY LINES
P-3
i-*-
—-®-
P-4
PLAN
WATER SURFACE
n	r
( f ! f
111!!
a
i
100'
SIDE
AIR '
HEADERS
DIFFUSEF
—7 — 1Y' WALL
37Jhl

C1"nf
16'.
-Vl
45'
END
AERATION TANK
WATER SURFACE
SCUM BAFFLE AND
DIRECTIONAL
FLOW CONTROL
EFFLUENT WEIR
EFFLUENT
TROUGH
FROM AERATOR
J I RETURN SLUDGE OR WASTE SLUDGE
SECONDARY CLARIFIER
Fig. 11.16 Activated sludge process units

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38 Treatment Plants
The gate should have been painted for rust and corrosion
protection, and now is an excellent time to touch up any chips
or scrapes. Remove the housing protecting the threaded stem
and check to be sure there is lubricant on the stem threads,
and see if there is a stop-nut at the top of the stem. If there is
not a stop-nut, insert one, because the gate could fall into the
aeration tank when you or some other operator opens it just a
little bit too far, or the stem could be bent attempting to close it
farther than necessary.
11.311	Storm Flow Gates and Pedestal Lift Gates
Storm flow gates may be used for normal conventional type
aeration tank feeding and/or abnormally high flows. Pedestal
lift gates are commonly used for STEP-FEED AERATION.12
Open and close each valve, checking for ease of operation and
proper seating. Give each stem a generous coat of heavy-duty
waterproof grease because the stems are normally exposed
directly to the wastewater.
QUESTIONS
Write your answers in a notebook and then compare your
answers with those on page 83.
11.3A Why should the operator completely check the equip-
ment and structures before start-up?
11.3B Why should lines and channels be cleaned before
start-up?
11.3C Why should chips and scrapes on gates be painted
before a tank is filled?
11.3D What is the purpose of stop-nuts on the stems of
valves?
11.312	Weirs
Weirs are used to control flow at the outlet or effluent end of
the aeration tank. Check these with a surveyor's level to be
sure one end is not higher than the other. Recheck after tank is
filled. If they are not level, the effluent will not be evenly distrib-
uted over the weir. This could cause short-circuiting and an
uneven distribution of solids in the effluent. The weirs should
have an adequate protective paint coating unless they are
made of a corrosion-resistant material.
11.313	Movable Gates
Check the guide slots of bulkheads for nicks or rocks and
make sure the gate seats and operates properly.
11.314	Water Sprays for Froth Control
Check each water spray head to see if it has a nozzle which
will form a fan of water. The fan of water should have an angle
to the tank surface of approximately 45°. Turn the water on for
a few minutes and check to be sure the spray properly covers
the desired area.
The nozzles must be properly installed to cover the
intended area of the aerator or they will be ineffective,
spraying the rails and walks. This creates a hazardous
condition of algae growths in the summer, or ice condi-
tions in the winter, and also does not dissipate much
foam.
There should be no leakage in the piping system, and the
water fans should overlap one another for effective control. At
the dead-end of each pipeline, check the operation of the valve
that allows flushing the whole line when opened. A "Y" strainer
should be installed at the inlet end of the system to filter out
large material, thus saving future maintenance time.
QUESTIONS
Write your answers in a notebook and then compare your
answers with those on page 83.
11.3E Why should an effluent weir be level?
11.3F What dangers are created if a foam spray nozzle
sprays on a rail or walk?
11.315 Air System
Check the air system by following it through in the direction
of air flow to the aeration tank.
A. Air Filters
Filters remove dust and dirt from the air before it is com-
pressed and sent to the aeration tank.
First check the access doors or hatches to the filter
chamber. These should be lined around the edges with rubber
or some material to form a tight seal. If there is a gap or torn
place, repair it. Check the inside of the filter chamber floors for
cleanliness and debris — remove any sand, dirt, paper, or
other debris.
Check the filter bags for proper coating of filter media. The
main check is to be sure that they are securely installed and
that one of the workers did not leave a tool or some item that
could go directly into one of the blowers.
A manometer is installed to read the difference in pressure
between the inlet side of the filters and the outlet side. The "U"
tube manometer is mounted on the outside of the filter housing
with two small copper lines running to the intake and outlet side
of the filters.
To check the manometer, remove the glass "U" tube from
the manometer housing, taking care not to break it. Blow air
through each line back to the manometer, checking to see that
the lines are clear and not plugged or accidentally crimped
during installation. If the lines are equipped with fittings, check
for tightness and leakage. If the lines are okay, fill the manome-
ter "U" tube with the required fluid. This could be a specified
oil, or water may be acceptable. Fill the "U" tube approximately
half the distance from the top of the tubes to the bottom of the
"U"; both columns should be the same height. If water is per-
missible to use, a drop or two of red or blue chart ink added to
the tube before the water is added gives a good color and an
easy indicator for reading the manometer. Before adding the
ink, experiment with laboratory glassware to be sure the ink will
12 Step-Feed Aeration Step-feed aeration is a modification of the conventional activated sludge-process. In step aeration, primary effluent
enters the aeration tank at several points along the length of the tank, rather than all of the primary effluent entering at the beginning or head
of the tank and flowing through the entire tank.
i

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Activated Sludge 39
not permanently stain the manometer glass and make future
readings impossible.
See Chapter 18, Section 18.2, for instructions on how to
read manometers.
The difference in pressure recorded by the manometers will
be small when the filters are clean, but as they become dirtier,
the manometer reading will increase and each column will
move farther away from the manometer zero mark. When this
difference reaches approximately 2 to 3 inches (5 to 8 cm) of
water column more than the initial difference, it is probably time
to clean or change the filters. The manufacturer's operating
manual should be reviewed for the recommended maximum
allowable pressure differential as well as the procedure for
cleaning the screens.
Check the air duct valving from the filters to the inlet side of
the air blowers (compressor) for proper installation. Also check
these ducts or pipes for dirt and debris.
QUESTIONS
Write your answers in a notebook and then compare your
answers with those on page 83.
11.3G Why and how is air cleaned before being compressed
and sent to the aeration tank?
11.3H How can you determine when the air filters need
cleaning?
B. Blowers (Compressors)
The blowers are of the positive displacement type. READ
THE MANUFACTURER'S MANUAL AND THOROUGHLY
UNDERSTAND IT BEFORE THE BLOWERS ARE EVER
STARTED. This manual should be provided by the manufac-
turer and can be obtained by writing to the company indicated
on the equipment name plate. Usually in the construction spec-
ifications the equipment suppliers are requested to supply
three or four copies of instructions for each piece of equipment.
If they are lost, a new one may be obtained by writing to the
manufacturer and giving the name, size, serial number, and
the treatment plant location and contract number if possible.
Each manufacturer normally supplies a one-year warranty on
their equipment. If the equipment is mistreated due to improper
operation, the warranty becomes void, and your community or
district must absorb the cost. Proper operation prolongs the life
of equipment and reduces the cost of repairs and replacement.
Special attention must be directed towards starting and
stopping procedures. PREPARE A LIST OF ITEMS TO BE
CHECKED BEFORE THE START BUTTON IS PUSHED.
Check switches, indicators, and pump connectors with draw-
ings. Check the type of oil and oil level. Start the oil circulation
pump and check the circulation system and oil level BEFORE
the blowers are started.
Check inlet and discharge valves by opening and closing
them and noting ease of operation. These units are to be
started under no load (the discharge air is vented to atmos-
phere until the unit is running properly), and then valved in
slowly to put the air into the system and load the unit. When the
unit is shut down, the reverse of the starting procedure is fol-
lowed. Be absolutely positive of the correct procedure for start-
ing and stopping the unit, including procedures for starting and
stopping one unit while the others are operating. Improper pro-
cedures can shorten the life of the equipment considerably.
Your supervisor will not be happy when equipment breaks
down or is worn out because of improper procedures.
Next, check the driver (electric motor), the blower base
plates, and the COUPLING for alignment. Usually the contrac-
tor's millwright sets the equipment and aligns the couplings
with a dial indicator. Request the dial readings from the con-
tractor and file them with the rest of the equipment data. These
readings are invaluable in case of equipment failure, or for
future checks on proper alignment. These should be no more
than 0.005 of an inch (0.125 mm) off, and larger equipment
calls for even closer tolerances. Check for base plate bolts or
nuts because if one corner is loose, the whole alignment will be
thrown out on start-up. Do not attempt to tighten base plate
nuts or bolts because this also will cause misalignment. If one
nut is loose or there is a gap between the equipment mount
and the base plate, the coupling must be realigned and the
equipment mounts shimmed.
If the blower and driver are securely anchored, all lubrication
points are in good condition and coupling alignments are satis-
factory, then motor and compressor will turn with a reasonable
pull on the outside pulleys. When all safety guards are installed
and well clear of the moving parts, then you are ready to check
the main air lines or "air mains."
On both the inlet and discharge sides of the blower, air
mains (air lines) are connected through a flexible coupling in
order to keep vibration at a minimum and allow for heat expan-
sion because, when air is compressed, heat is generated. This
can increase the discharge temperature as much as 100°F
(56°C) or more. Check to be certain there is sufficient room for
movement in the flexible couplings.
The discharge air line from the blower is equipped with an air
relief valve which protects the blower from excessive back
pressure and overload. It is adjusted by weights or springs to
open when air pressure exceeds a point above normal oper-
ating range, around 7.5 to 10 psi (0.5 to 0.7 kg/sq cm). Check
this valve to insure its free operation by manually lifting the
valve off the seat.
Between the air relief valve and the discharge side of the
blower is a pressure gage to read discharge pressure. Check
the gage for proper installation by looking for air leaks and for
easy accessibility to read.
A metering device should be located in a straight section of
the air main on the discharge side of the blower. This device
consists of an orifice plate inserted between two specially
made pipe flanges. The orifice plate is made of stainless steel
with a precision hole cut through the center. The diameter of
the hole will vary according to the flow rates to be measured.
The plate is made of Ve-inch (3 mm) thick material and is

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40 Treatment Plants
slightly larger than the inside diameter of the pipe. A
rectangular-shaped handle is attached to the plate. The plate
is installed between the flanges, blocking the pipeline except
for the hole in the center of the plate. One side is bevelled,
leaving a sharp edge on the opposite side. The handle of the
orifice plate will have numbers stamped into it giving the orifice
size. These numbers on the handle are stamped on the same
side as the sharp edge of the orifice opening. When viewing
the plate to read the numbers, the blower should be behind
you. THE SHARP EDGE OF THE PLATE AND THE NUMBERS
MUST BE ON THE SIDE TOWARD THE BLOWER FOR IT TO
READ PROPERLY.
On top of each pipe flange holding the orifice plate will be a
hole tapped and connected to tubing leading to the instruments
which indicate the rate of air flow. Check these to see that
there are no air leaks. The instruments themselves should
have been installed and calibrated correctly, but occasionally
an orifice plate is installed backwards or an instrument line is
left disconnected. When the meter is properly connected to a
dial or totalizer, a zero reading should be recorded when the
pump is off.
Check the condensate trap or drain located near the aera-
tion tank at the lowest point of the air main. Open and close the
drain line and remove any dirt or sand in the air main at this
location.
Inspect the air main from the blowers to the air headers for
leaks, tightness, and expansion allowances.
QUESTIONS
Write your answers in a notebook and then compare your
answers with those on page 83.
11.31 Why is it important to read the blower or compressor
manufacturer's manual before starting the equip-
ment?
11.3J If your plant does not have a manufacturer's manual,
how would you obtain one?
11,3K Why should proper procedures be followed when start-
ing, operating, and stopping equipment?
11.3L How should the sharp edge of a metering orifice be
placed in a pipe?
C. Air Headers
The air main runs down the center "Y" wall of the aeration
tank, distributing air to the headers along the tank. This plant is
equipped with "swing headers." A swing header is merely a
pipe with movable couplings so the header may be raised from
the tank with a hoist to service the diffusers.
Take the hoist that is to be used to raise and lower the air
headers out to the center "Y" wall and make sure it properly fits
each air header. The hoist is anchored by the air header oppo-
site the one to be lifted. Sometimes the correct spacing is
missed and the hoist is either too short or too long. In either
case, you would not be able to lift those two headers, for there
is no other safe way to anchor the hoist. If you attempted to lift
a header without the hoist anchored, it could catapult into the
tank, possibly taking the operator with it and surely damaging
the hoist (and probably the diffusers and headers too).
Each header is equipped with a valve to shut the air off when
removing it from the tank to replace or clean the diffusers.
Consequently, the other headers may be kept in service, thus
not disrupting the air supply to the tank contents. Inspect each
air header valve for proper operation, and determine which
position of the stem indicates open and which position indi-
cates closed.
The center "Y" wall is a hazardous area and caution is
required when working here. If the aeration tank is empty, a
16-foot (5 m) fall could be fatal. When the tank is in service
you could drown if you fell into it. A good policy is that ANY
WORK ON THE CENTER "Y" WALL CALLS FOR TWO
OPERATORS AND LIFE PRESERVERS AND/OR LIFE
LINES.
Other safety precautions that should be observed at all times
when working on center "Y" walls include:
1.	Wear shoes with soles that retard slipping. Cork-inserted
composition soles provide the best traction for all-around
use.
2.	Slippery algal growths should be scrubbed and washed
down whenever they appear.
3.	Keep the area clear of spilled oil or grease.
4.	Do not leave tools, equipment, and materials where they
could create a safety hazard.
5.	Adequate lighting should be permanently installed for night
work.
6.	Ice conditions in winter may require spiked shoes and sand-
ing icy areas if ice cannot be thawed away with wash water.
7.	Remove only sections of removable handrails necessary
for immediate job. Removed sections should be properly
stored out of the way and secured against falling.
Since the aeration tank is empty or nearly empty, place a
ladder in the tank and continue the check-out.
First, remove any debris, including sand or dirt, from the
bottom of the tank.
Next, check the air headers. This is the continuation of the
air system to the bottom of the tank with the pipes creating an
inverted "T." The horizontal run of pipe forming the cross-bar
on the top of the "T" should be perfectly level. If one end is
1/2-inch (1.2 cm) higher than the other end, then more air will
escape through the high end, causing poor air distribution. The
contractor should have set them with a surveyor's level to in-
sure that they are all at the same elevation, but it is advisable
to check them again. Be sure diffusers are secure and header
or diffuser plugs are in place; replace damaged or defective
items.
The pipe should have been flushed with water to remove
dirt, dust, and scale.
QUESTIONS
Write your answers in a notebook and then compare your
answers with those on page 83.
11,3M Why must the hoist used to lift the air headers be
properly anchored?
11.3N What precautions would you take when working on the
center "Y" wall?
11.30 Why must the horizontal pipes containing the air dif-
fusers all be at the same elevation (level)?
D. Diffusers
Thread-type diffusers are installed in our example plant. Be-
fore the diffusers were installed, the pipe should have been
flushed clean with water. Inspect the diffusers. A light applica-
tion of grease on the threads (taking care that none of the
lubricant touches the opening into the diffuser) should have

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Activated Sludge 41
been applied for ease in removing the diffusers when they
need cleaning. DO NOT USE A WRENCH WHEN INSTALLING
THREADED DIFFUSERS; NORMAL "HAND TIGHT" IS SUF-
FICIENT, AND EVEN THIS CAN CREATE A PROBLEM WHEN
THE TIME ARRIVES TO REMOVE THEM.
E. Blower Testing
After you have inspected the air headers and diffusers in the
aeration tank, check the blower operation. Start with the blow-
ers discharging air directly to the atmosphere. Review the stop
and start procedure for the blowers and turn them on. If at all
possible, let them run for three or four hours to check on any
heating problems or vibrations. Check temperatures, amper-
age readings from the electric motors, and air flow rates and
differential pressures across the filter system, and RECORD
THEM.
Repeat these checks after the process tanks are filled. Now
is the time to check the air relief valves for correct settings by
closing several valves out on the headers until the air relief
valves open. Also take another set of amperage readings on
the blower motor to see if it is overloaded under operating
conditions. If everything functions properly for four hours, you
can feel fairly certain that you will not have any immediate
problems from the blowers.
QUESTIONS
Write your answer in a notebook and then compare your
answer with those on page 83.
11.3P While the blowers are running, what items should be
checked, and why?
11.3Q Why should a light application of grease be applied to
the threads of a diffuser?
11.32 Secondary Clarifiers
CIRCULAR CLARIFIERS - check items:
1.	Control gates for operation
2.	Clarifier tank for sand and debris
3.	Collector drive mechanism for lubrication, drive alignment,
and complete assembly
4.	Squeegee blades on the collector plows for proper distance
from the floor of the tank
5.	Connecting lines or channels between aerator and clarifier
for debris
6.	Pump suction line assembly and controls
7.	Inlet baffles and discharge weirs for level
8.	Scum control mechanism
Once the collectors are started in a new tank, each scraper
should be checked for a clearance of one to two inches (2.5 to
5 cm) between the wall and the end of the scraper. If a scraper
is too long, it may rub the tank wall and break the scraper,
jamming other scrapers and breaking them. Once a broken
scraper is detected, it should be replaced or removed from the
support structure.
11.33 Return Sludge and Waste Sludge Pumps
Since these two items are identical except for size, the same
checks may be used.
Clean out trash in all sludge hoppers, lines, valves, gates,
sweeps, and drive mechanisms before checking pumps.
To check out pumps, FIRST lock out and tag the pump
motor at the power panel so it cannot be started.
Remove the handhole cover, clean out the pump casing or
volute, and check the impeller for debris and secure fit to the
pump shaft. Wear gloves when cleaning pump casings to pro-
tect your hands from dangerous sharp objects. Replace the
handhole cover. Install or check pressure gages on the suction
and discharge lines of the pump. Check inlet and outlet valve
operation and connecting lines for clearance.
Check pump and motor bearings for lubrication. Inspect
coupling alignment and base plate anchor bolts. Turn on the
seal water to the pump. Since the pump has not operated,
back off the packing gland nuts and rotate the pump shaft by
hand through several revolutions. Leave the packing nuts
loose and adjust them properly after start-up. If everything
checks out satisfactorily, then run some water into the final
clarifier hopper or return sludge well where the pump suction is
located so it may be operated for a few minutes. While the
water is filling the hopper or wet well, check the suction and
discharge valves and check (flap) valves on the system. Check
the other valves on the return sludge line for proper operation.
Open both inlet and discharge valves before starting the pump
so the water may flow during the pump test.
There should be several hundred gallons of water available
in the final clarifier for the pump test. Prime the pump if neces-
sary and, if everything has checked out properly, unlock the
controls at the power panel and turn the pump on. First check
pump rotation and the packing gland for water, but let it flow
freely for now. Read both pressure gages on suction and dis-
charge and the level of the water in the clarifier or wet well;
RECORD all three measurements in order that the operational
characteristics and efficiency of the pumps may be checked.
Take an amperage reading on the motor and RECORD. If
possible, make sure that the meter is functioning, and RE-
CORD a flow meter reading too. The water available will not
afford a very long run, but it will indicate any major problems.
When the pump is shut off, make sure the check valve closes
and seats.
To check the waste sludge pump, the return sludge pump
also must be running. Run the waste sludge pump now to be
sure it will operate properly when you are ready to start wasting
activated sludge.

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42 Treatment Plants
The following list contains a summary of the items that
should be recorded when testing pumps.
A . Uame cA purr>p\ 		—	
2.	Location of pump: 	
3.	Pump suction pressure:	
4.	Pump discharge pressure:	
5.	Water level in wet well:	
6.	Motor amperage:	
7.	Pump discharge (flow):				
8.	Date of test.	_	____
9.	Name of operator:	
QUESTION
Write your answer in a notebook and then compare your
answer with the one on page 83.
11.3R List all the information which should be RECORDED
for future reference when you test the return sludge
and waste sludge pumps.
W OF 1 OfS WftOM
Ofouxmt)
ACTIVATEP <£UIP<2>&
Please answer the discussion and review questions before
continuing with Lesson 4.
DISCUSSION AND REVIEW QUESTIONS
Chapter 11. ACTIVATED SLUDGE
(Lesson 3 of 8 Lessons)
Write the answers to these questions in your notebook be-
fore continuing. The problem numbering continues from Les-
son 2.
14.	What should the operator look for when checking out con-
trol gates?
15.	What happens when spray nozzles are not installed prop-
erly and spray falls on rails and walks?
16.	Why should proper procedures be followed when check-
ing equipment?
17.	What safety precaution should be exercised before check-
ing the impeller of a return sludge pump?
18.	Why should the equipment manufacturer's manual be
thoroughly read and understood before any equipment is
started?

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Activated Sludge 43
CHAPTER 11. ACTIVATED SLUDGE
OPERATION OF ACTIVATED SLUDGE PLANTS
(Lesson 4 of 8 Lessons)
11.4 PROCESS START-UP PROCEDURES
11.40	General
Procedures for starting the activated sludge process are out-
lined in this lesson. Procedures and example calculations will
be for the plant checked out in the previous lesson. An initial
average daily flow of 4.0 MGD (15,140 cu m/day) will be as-
sumed, and the plant will be operated as a conventional acti-
vated sludge plant.
Start-up help should be available from the design engineer,
vendors, nearby operators, or other specialists. The equipment
manufacturers or contractor should be under contract for
start-up instruction and assistance. During start-up they should
be present to be sure that any equipment breakdowns are not
caused by improper start-up procedures.
The operator may have several options in the choice of
start-up procedures with regard to number of tanks used and
procedures to establish a suitable working culture in the aera-
tion tanks. The method described in this lesson is recom-
mended because it provides the longest possible aeration
time, reduces chances of solids washout, and provides the
opportunity to use most of the equipment for a good test of its
acceptability and workability before the end of the warranty.
11.41	First Day
First, start the air blowers and have air passing through the
diffusers before primary effluent is admitted to the aeration
tanks. This prevents diffuser clogging from material in the pri-
mary effluent.
Fill both aeration tanks to the normal operating water depth,
thus allowing the aeration equipment to operate at maximum
efficiency. Employing all of the aeration tanks will provide the
longest possible aeration time. You are trying to build up a
population with a minimum amount of seed organisms, and
you will need all the aeration capacity available to give the
organisms a chance to reach the settling stage.
When both aeration tanks have been filled, begin filling the
two secondary clarifiers. Use of all the secondary clarifiers will
provide the longest possible detention time to reduce washout
of light solids containing rapidly growing organisms and will
encourage solids buildup.
When the secondary clarifiers are approximately three-
fourths full, start the clarifier collector mechanism and return
sludge pumps. Return sludge pumping rates must be adjusted
to rapidly return the solids (organisms) back to the aeration
tanks. The solids should never remain in the secondary
clarifiers longer than 1.5 hours. Trouble also may develop if the
return sludge pumping rate is too high (greater than 50 percent
of the raw wastewater flow), because the high flows through
the clarifier may not allow sufficient time for solids to settle to
the bottom of the clarifier. A conventional activated sludge
plant usually operates satisfactorily at return sludge rates of 20
to 30 percent of raw wastewater flow, but the rate selected
should be based upon returning organisms back to the aerator
where they can treat the incoming wastes. A thin sludge will
require a higher return percentage than a thick one. However,
increasing the return percentage with a thin sludge can pro-
duce a thinner sludge. Addition of a coagulant or flocculant aid
at the end of the aeration tank will hasten solids buildup and
improve effluent during start-up.
When the secondary clarifiers become full and begin to over-
flow, start effluent chlorination to disinfect that plant effluent.
Filling the aeration tanks and aerating the wastewater starts
the activated sludge process. The AEROBES™ in the aeration
tank have food and are now being supplied with oxygen; con-
sequently this worker population will begin to increase.
After two or three hours of aeration, you should check the
dissolved oxygen (DO) of the aeration tanks to see if enough
air is being supplied. (See Chapter 16, "Laboratory Proce-
dures and Chemistry," for procedure to run DO test.)
Check the DO THROUGHOUT the aerator. If possible, use a
DO probe and determine the DO along both sides of the
aerator at both the water surface and bottom. Oxygen must be
available for the aerobes throughout the tank. If the DO is less
than 1.0 mg/L, increase the air supply. If the DO is greater than
3.0 mg/L the air supply may be decreased, but not to the point
where the tank would stop mixing. There will probably be an
excess amount of DO at first due to the limited number of
organisms initially present to use it.
^After a biological culture of aerobes is established in the
aeration tanks, sufficient oxygen must be supplied to the aera-
tion tank to overcome the following demands:
1.	DO usually is low in both influent wastewater and return
sludge to the aerator.
2.	Influent wastewater may be septic, thus creating an im-
mediate oxygen demand.
3.	Organisms in the presence of sufficient food create a high
demand for oxygen.
The effluent end of the aerator should have a dissolved oxy-
gen level of at least 1.0 mg/L. DO in the aerator should be
checked every two hours until a pattern is established. There-
after, DO should be checked as frequently as needed to main-
tain the desired DO level. Daily flow variations will creat differ-
ent oxygen demands. Until these patterns are established, you
won't know whether just enough or too much air is being deliv-
ered to the aeration tanks. Frequently excess air is provided
during early mornings when the inflow waste load is low. Air
supply may be too low during the afternoon and evening hours
because the waste load tends to increase during the day.
Turn on the spray-water system as soon as possible be-
cause foaming from detergents will be severe until there is a
sufficient build up of solids. If the spray-water pump is dry,
apply commercial defoamers to the surface of the aerator to
control foam.
13 Aerobes. Bacteria that must have molecular (dissolved) oxygen (DO) to survive.

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44 Treatment Plants
11.42	Second Day
Collect a sample from the aeration tank and run a 60-minute
settleability test using a 1000 ml graduated cylinder. If possi-
ble, use a 2000 ml cylinder with a five-inch (125 mm) diame-
ter14 in order to obtain better results. Observe the sludge set-
tling in the sample for approximately one hour. It will probably
have the same color as the primary effluent during the first few
days. After a few minutes in the cylinder, very fine particles will
start forming with a light buff color. The particles remain sus-
pended, but settling, similar to fine particles of dust in a light
beam. After one hour, a small amount of these particles may
have settled to the bottom of the cylinder to a depth of 10 or 20
ml, but most are still in suspension. This indicates that you are
making a start toward establishing a good condition in the
aeration tank, but many more particles are needed for effective
wastewater treatment.
11.43	Third Through Fifth Days
During this period of operation the only controls applied to
the system usually consist of maintaining DO concentrations in
the system and maintaining proper sludge return rates. A sam-
pling program should be started in accordance with Section
11.03, "Plant Records," to develop and record the necessary
data required for future plant control.
Aeration of wastewater to maintain DO will require some
time before settling will produce a clear liquid over the settled
solids. Time is required for organisms to grow to the point
where there are sufficient numbers to perform the work needed
— to produce an activated sludge. Usually within 24 to 72
hours of aeration you will note that the settleable solids do not
fall through the liquid quite so rapidly, but the liquid remaining
above the solids is clearer.
The active solids (organisms) are light and may wash out of
the clarifier to some extent. Try to retain most of them, because
a rapid solids buildup will not occur unless they are retained. A
good garden soil will add organisms and solids particles for
start-up. Mix the soil with water and hose in the lighter slurry,
but try to avoid a lot of grit. A truckload of activated sludge from
a neighboring treatment plant also will help to start the pro-
cess. Hopefully you will not have to treat design flows during
plant start-up. More time is needed both for aeration and
clarification until you have collected enough organisms in your
return sludge to enable you to produce a clear effluent after a
short period of mixing with the influent followed by settling.
QUESTIONS
Write your answers in a notebook and then compare your
answers with those on page 84.
11,4A Why should chlorination equipment be put in service
when effluent starts leaving the plant?
11 4B How is the return sludge rate selected during initial
start-up?
11.4C Why should the blowers be started before primary
effluent is admitted to the aeration tanks?
11,4D At what locations in the aeration tank would you check
the DO, and why?
11.44 Sixth Day
A reasonably clear effluent should be produced by the sixth
day. Solids buildup in the aeration tank should be closely
checked using the 60-minute settleable solids test during the
first week. Results of this test indicate the flocculating, settling,
and compacting characteristics of the sludge. Suspended sol-
ids buildup is very slow at first but increases as the waste
removal efficiency improves. This buildup should be carefully
measured and evaluated each day.
Microorganisms in the system are so varied and small that it
is impossible to count them. To obtain an indication of the size
of the organism population in the aeration tank, the solids are
measured either in mgIL or in pounds of dry solids. Suspended
solids determinations for aerator mixed liquor will give the de-
sired information in mgIL, and the total pounds of solids may
be calculated on the basis of the size of the aerator.
Soli^lbs = Susp' So,ids' m9lL x Aer. Vol, MG x 8.34 lbs/gal
or
= SS, mgIL x Aer. V,
Solids, kg
cu m x
1 kg
, 1,000 L
1,000,000mg 1 cu m
The suspended solids test (see Chapter 16, "Laboratory
Procedures and Chemistry") conducted on activated sludge
plant mixed liquor is normally a grab sample obtained at the
effluent end of the aerator. The sample should be collected at
the same time every day, preferably during peak flows, in order
to make day-to-day comparisons of the results. Collect the
mixed liquor sample approximately five feet (1.5 m) from the
effluent end of the aeration tank and 1.5 to 2 feet (0.4 to 0.6 m)
below the water surface to insure a good sample. A return
sludge sample also should be collected at this time every day
to determine its concentration.
With information from the tab tests, estimates of the or-
ganisms mass (weight) in the aerator can be calculated.
Information needed:
1.	Aeration Tank Dimensions
100 ft long, 45 ft wide, and 16.5 feet deep
2.	Results of Laboratory Tests
Mixed Liquor Suspended Solids, 780 mgIL
Steps to calculate pounds of solids in aeration tank:
1.	DETERMINE AERATION TANK VOLUME.
Volume, = Length, ft x Width, ft x Depth, ft
cu ft
= 100 ft x 45 ft x 16.5 ft
= 74,250 cu ft
2.	CONVERT CU FT TO GALLONS.
Aerator
Volume,
gals
or
or
74, 250 cu ft x 7.48 gals/cu ft
555,390 gals
555,000 gals (approximately)
0.55 MG
14 Mai lory Direct Reading Settlometer (a 2 liter graduated cylinder approximately 5 inches (125 mm) in diameter and 7 inches (175 mm) high).
Obtain from SGA Scientific, Inc., 735 Broad Street, Bloomfield, New Jersey 07003. Catalog No. JS-1035. Price $35.00 each.

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Activated Sludge 45
3. CALCULATE POUNDS OF SOLIDS UNDER AERATION.
Formula:
Solids, lbs
= MLSS, mgIL x Aer. Vol, M Gal x 8.34 lbs/gal
= 780 mgIL X 0.55 M Gal x 8.34 lbs/gal
= 780 mg x 0.55 M Gal x 8.34 lbs/gal
M mg
= 780 x 4.6* lbs
= 3588 lbs
Close observation of the suspended solids buildup and re-
sults from the 60-minute settleability test will indicate the solids
growth rate, condition of solids in aerator, and how much
sludge should be returned to insure proper return of the or-
ganisms to the aerator. It will be necessary to return all of the
sludge for 10 to 15 days or longer if the wastewater is weak.
Results from the 60-minute settleability test can be used to
estimate if the return sludge rate is too high or too low. If the
volume of settled sludge in the cylinder is indicative of the
amount of sludge settling in the secondary calrifier, the volume
of return sludge should be equal to or slightly greater than the
percentage of settling sludge in the cylinder multiplied by the
sum of the primary effluent and the return sludge flows.
Estimate the return sludge pumping rate.
Information needed:
1.	Flow to Aerator from Primary Clarifier, 4.0 MGD
2.	Return Sludge Flow, 1.0 MGD
3.	Volume of Mixed Liquor Solids Settled in 60 Minutes, 360
ml in 2 liters, or 18%
EXAMPLE:
Flow to Aerator from Primary Clarifier = 4.0 MGD
Return Sludge Flow to Aerator	= 1.0 MGD
Total Flow through Aerator	= 5.0 MGD
RauTMGD196 = Aera,or F|0W- MGD * Settleable Solids, %
= 5.0 MGD x 0.18
- 0.9 MGD or 900,000 gals/day
Return Sludge
Rate, GPM
900,000 GPP
1440 min/day
625 GPM (39.4 Usee)
Therefore, the initially selected 700 GPM return sludge rate
is acceptable at this time. It insures that most solids are being
returned to the aeration tank. A return sludge pumping rate
slightly higher than calculated is recommended to return the
organisms as fast as possible to the aerator. However, a return
sludge rate that is too high must be avoided because the result-
ing high flows reduce the detention time in the aerator and
secondary clarifier.
If the return sludge rate is too low, the following undesirable
conditions may develop:
1.	Insufficient organisms will be in the aerator to treat the in-
fluent waste (food) load. This normally occurs during the
first week or two of start-up.
2.	Septic sludge could develop if the detention time in the
secondary clarifier is too long.
3.	Accumulation of sludge in the clarifier creates a deep
sludge blanket which will allow solids to escape in the
effluent.
QUESTIONS
Write your answers in a notebook and then compare your
answers with those on page 84.
11,4E When and where should solids samples be collected
to provide the operator with a record of solids buildup
in the aeration tank?
11.4F Determine the pounds of solids in an aeration tank
with a volume of 0.25 MG and a Mixed Liquor Sus-
pended Solids (MLSS) concentration of 640 mgIL.
11,4G Estimate the return sludge pumping rate (GPM) if the
plant inflow is 2.0 MGD and the return sludge flow is
0.5 MGD. The results of the 60-minute settleability test
indicate the volume of solids settled to be 340 ml in 2
liters, or 17%.
W OF L&&OH 4 0F3 U&iOM
Q/OUMPX)
rMCTlVATe? £UIP6E-
Please answer the discussion and review questions before
continuing with Lesson 5.
* The factor 4.6 lbs is equivalent to 0.55 x 8.34, a constant for your
plant. You will use this value every day as long as you use the same
aeration tank capacity. Only a change in the suspended solids
concentration will cause a change in the pounds of solids in the
aeration tank.

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46 Treatment Plants
DISCUSSION AND REVIEW QUESTIONS
Chapter 11. ACTIVATED SLUDGE
(Lesson 4 of 8 Lessons)
Write the answers to these questions in your notebook be-
fore continuing. The problem numbering continues from Les-
son 3.
19. When starting a new activated sludge plant, who might the
operator contact for assistance and advice?
20.	When starting the activated sludge process, why should
you use all of the aerators and all of the secondary
clarifiers?
21.	What are the essential laboratory tests for starting the
activated sludge process, and why?
CHAPTER 11. ACTIVATED SLUDGE
OPERATION OF ACTIVATED SLUDGE PLANTS
(Lesson 5 of 8 Lessons)
11.5 ROUTINE OPERATIONAL CONTROL
11.50 How to Control the Process
Effectiveness of the activated sludge treatment process in
reducing the waste load depends upon the AMOUNT OF AC-
TIVATED SLUDGE SOLIDS IN THE SYSTEM and the HEALTH
OF THE ORGANISMS which are a part of the solids. To suc-
cessfully maintain control of the solids and health of the or-
ganisms requires continuous (seven days a week) observation
and checking by the plant operators. SLUDGE AG£15 is one of
the methods used by operators to determine and maintain the
desired amount of activated sludge solids in the aeration tank.
Sludge age is recommended for operational control because
suspended solids are relatively easy to measure. In addition,
sludge age considers two factors vital to successful operation:
(1) solids (food) entering the treatment process and (2) solids
(organisms) available to treat the incoming waste (food). A
critical point to recognize is that the solids test is capable of
indicating both the amount of food carried by the inflow to the
process and the number of organisms available to treat the
waste.
Operation of a conventional activated sludge plant is illus-
trated in this section because the example plant selected to
indicate start-up procedures has an allowable effluent BOD of
20 mgIL. A sludge age of five days (see Table 11.2, Section
11.05, page 19) will serve as a satisfactory loading target dur-
ing start-up for this plant. After the plant is in operation, various
sludge ages may be tried in an effort to improve the quality of
the plant effluent.
How activated sludge is wasted can have an important im-
pact on the "best" sludge age for your plant. If activated sludge
is wasted to the primary clarifiers, the wasted organisms could
be mistaken for food entering the treatment process. If acti-
vated sludge is wasted to a gravity thickener, not as many
organisms would be in the effluent from the primary clarifier.
Therefore, plants wasting to the primary clarifier may have a
lower sludge age than plants wasting to a gravity thickener.
Temperature also influences sludge age. The warmer the
weather the more active the organisms, so the sludge age can
be lowered by reducing the MLSS (Mixed Liquor Suspended
Solids).
Always remember that you must maintain the DO in the
aerator and more air will be required when aeration tank solids
increase in concentration and activity.
11.51 Determination of Sludge Age
Whether a new plant is being started or the operation of an
existing plant is being checked, the sludge age is used to
indicate when activated sludge should be wasted and, if nec-
essary, the waste sludge pumping rate.
Information needed to determine sludge age includes:
1.	Mixed Liquor Suspended Solids = 2380 mgIL
2.	Primary Effluent Composite Suspended Solids = 72 mg/L
(average of daily values for past week)
3.	Average Daily Influent Flow = 4.0 MGD
1. DETERMINE POUNDS OF MIXED LIQUOR SUSPENDED
SOLIDS IN AERATOR.
Solids in
Aerator, = MLSS, mgIL x Aerator Vol., MG x 8.34 lbs/gal
"38, = 2380 mg/L x 4.6 (factor from Section 11.44, pg. 45)
= 10,948 lbs, or approximately 11,000 lbs
'5 Sludge _ Mixed Uquor suspended Solids in Aerator, lbs
Days ~ Suspended Solids In Primary Effluent, Ibslday

-------
Activated Sludge 47
2. DETERMINE POUNDS OF SOLIDS ADDED PER DAY TO
SYSTEM BY PRIMARY EFFLUENT.
Solids
Added by
Primary = Prim. Effl. SS, mgIL x Flow, MGD x 8.34 lbs/gal
lbs/day' = 72 mg/L x 40 MGD x 834 lbs/9al
= 72 x 88.4 lbs/day
= 2404 lbs/day, or approximately 2400 lbs/day
3. CALCULATE SLUDGE AGE IN DAYS.
Sludge
Age,
days
Suspended Solids in Aerator, lbs
Suspended Solids in Primary Effluent, lbs/day
11,000 lbs
2400 lbs/day
= 4.5 days
If the results of lab tests and calculations indicate a sludge
age of 4.5 days when the target sludge age is five days, no
sludge should be wasted. If a sludge age of 4.5 days was
obtained during the start-up of the example plant, the operator
should continue to allow the solids to increase in the aerator. In
an existing plant, if the sludge age is below the desired level,
any sludge wasting should be reduced or stopped.
A simple way to find the desired pounds of aerator solids to
be maintained is to multiply the average daily pounds of pri-
mary effluent solids added per day by the desired sludge age.
EXAMPLE:
Find the desired pounds of solids to be maintained in the
aerator.
Information needed:
Desired Sludge Age, days = 5 days
Solids in Primary Effluent, lbs/day = 2400 lbs/day
Calculate pounds of solids desired in aerator.
Sludge = Suspended Solids in Aerator, lbs
Age,
days
Suspended Solids in Primary Effluent, lbs/day
Rearrange the equation to obtain:
Suspended
Solids in
Aerator,
lbs
= Sludge Age, days x SS in Prim. Effl., lbs/day
= 5 days x 2400 lbs/day
= 12,000 lbs
Suspended solids in the mixed liquor in the aerator should
be allowed to build up until 12,000 pounds (5,455 kg) of solids
are in the aerator. Sludge wasting may be started when the
desired level is exceeded.
To determine when an excess of activated sludge is in the
aerator and some should be wasted, many operators calculate
the desired mixed liquor suspended solids concentration in the
aerator. When this concentration is exceeded, some of the
excess activated sludge is wasted.
Calculation of the desired mixed liquor suspended solids
concentration in mg IL can be determined from either of the two
formulas listed below (they are the same).
Desired Mixed
Liquor Suspended
Solids, mgIL
Desired Susp. Sol. in Aerator, lbs
Weight of Water in Aerator, million lbs
Qr	_ Desired Susp. Sol. in Aerator, lbs
Vol. of Aerator, M gal x 8.34 lbs/gal
= 12.000 lbs
4.6 M lbs (factor from Section 11.44, page 45)
= 2608 mgIL
= 2600 mg/L (target concentration)
Wasting of activated sludge from the example plant should
not start until the mixed liquor suspended solids concentration
exceeds 2600 mg/L.
11.52 Wasting Activated Sludge
The amount of activated sludge wasted may vary from 1 to
20 percent of the total incoming flow. Normally waste activated
sludge is expressed in gallons per day or pounds of solids
removed from the aeration system. Continuous wasting is pre-
ferred. Try not to change your sludge wasting rate by more
than 10 or 15 percent from one day to the next day. The main
purpose is to maintain a sludge age that produces the best
effluent.
Wasting (Fig. 11.17) is normally accomplished by diverting a
portion of the return sludge to a primary clarifier, thickener,
aerobic digester, or anaerobic digester. Normal operations in a
conventional activated sludge plant will concentrate return
sludge and waste sludge solids three to four times as much as
the solids concentration of the mixed liquor. This may provide
return sludge with a concentration of 2,000 to 10,000 mg/L, or
0.2 to 1.0 percent in terms of total solids. If the waste sludge
line discharges directly to the anaerobic digestion system, it
would contain 10 to 20 times as much water as should be
entering the anaerobic system with that amount of solids.
Operating an anaerobic digester would be difficult under this
condition. It would be wiser to waste to the primary clarifiers
where combining with primary sludge minimizes the addition of
excess water to the digester.
Wasting activated sludge will occur in the effluent whether or
not it is controlled. In all activated sludge plants, wasting must
be controlled by the operator. Mixed liquor suspended solids
which need to be wasted accumulate from two sources. The
first is the suspended solids in the plant flow from the primary
clarifiers or raw wastewater. The second and main source is
the new cell production by the microorganisms.
For every pound of BOD or solids removed in the activated
sludge system, a part of that pound will remain in the system
as microorganisms. The rate of production of excess sludge
will depend on the type of process being operated and the
nature of the waste load. The high-rate activated sludge plant
is capable of producing 0.75 pounds of sludge volatile matter
for every pound of BOD removed. The conventional plant runs

-------
PRIMARY EFFLUENT
TO
RECEIVING
WATERS
PLANT—*
INFLUENT
RETURN
ACTIVATED SLUDGE (RAS)
THICKENER
EFFLUENT-
WASTE ACTIVATED SLUDGE (WAS)
SOLIDS
ANAEROBIC
DIGESTER
(PRIMARY)
/ANAEROBIC^
DIGESTER
^SECONDARY]
SOLIDS
THICKENER
PRIMARY
CLARIFIER
SECONDARY
CLARIFIER
AERATION
TANK
PRETREATMENT
CHLORINE
CONTACT-
SOLIDS
DEWATERING
DRY SOLIDS
SOLIDS WASTING WITH A GRAVITY OR FLOATATION THICKENER
oo
H
3
S
3
9
3
r*
¦o
»
3
V*
CO
Fig. 11.17 Waste sludge flow diagram

-------
Activated Sludge 49
around 0.55 pounds of sludge volatile matter per pound of
BOD removed in the activated sludge system. The extended
aeration plant drops down to about 0.15 pounds of sludge
volatile matter per pound of BOD removed. Excessive silt or
inert material may increase sludge production beyond that in-
dicated by the BOD test.
11.53 Determination of Waste Sludge Pumping Rate
To illustrate the determination of a waste sludge pumping
rate, assume the following plant data:
1.	Mixed Liquor Suspended Solids = 2985 mgIL
2.	Return Sludge, Suspended Solids = 6200 mg/L
3.	Primary Effluent, Suspended Solids = 72 mg/L
4.	Average Daily Flow = 4.0 MGD
5.	Current Waste Sludge Pumping Rate = 0.050 MGD
Using the procedures outlined in this lesson, the following
information can be calculated.
1.	Solids in Aeration Tank = 13,731 pounds
2.	Solids Added by Primary Effluent = 2400 lbs/day
3.	Sludge Age = 5.7 days
The results of the calculations indicate that the sludge age is
too high (5.7 days instead of 5 days) and the solids in the
aeration tank also are too high (13,731 pounds instead of
12,000 pounds). To reduce the sludge age and solids in the
aerator, some of the activated sludge removed by the second-
ary clarifier should be pumped to the inlet of the primary
clarifier or to the solids thickener, depending on facilities in the
plant for wasting activated sludge.
The formula to calculate the additional waste return sludge
pumping rate is:
Additional Waste Return Sludge Pumping Rate, MGD
= Additional Solids to be Wasted, lbs/day
Return Sludge Cone., mgIL x 8.34 lbs/gal
= (13,700 lbs - 12,000 lbs)/day*
6200 mg/L x 8.34 lbs/gal
=	1700 lbs/day
6200 mg/L x 8.34 lbs/gal
_ 1,700
Usually the waste sludge pumping rate is expressed in gal-
lons per minute instead of MGD.
Pump Waste
Rate, GPM
51,700
= 0.032 MGD
Calculate the total waste return sludge pumping rate.
Total Return Sludge = Current + Additiona,
Pumping Rate, MGD Rate MQD Rate MQD
= 0.050 MGD + 0.032 MGD
= 0.082 MGD
= Pumping Rate, gals/day
1400 min/day
_ 82,000 gals/day
1440 min/day
= 57 GPM (3.6 L/sec)
Set the waste pumping rate at 50 or 55 GPM for the next
24-hour period. It is better to waste a little less activated sludge
than the theoretical calculation. Also try not to make large
changes in the waste pumping rate from one day to the next
day.
11.54 Operational Strategy
An excellent effluent can be produced by the activated
sludge process if the operator has a plan of operation or opera-
tional strategy and understands how the microorganisms re-
move wastes from the water being treated. This section pro-
vides a brief plan for operating an activated sludge plant on a
day-to-day basis. If problems develop, refer to Section 11.6,
"Operational Problems," for possible solutions. There are
three areas of major concern for the operator of an activated
sludge plant:
1.	What enters the plant,
2.	The environment for treating the wastes, and
3.	What leaves the plant.
All three of these areas are closely related or are influenced
by the other two areas.
11.540	Influent Characteristics
As the influent flows and waste concentrations change, the
environment changes in the aeration tank and secondary
clarifiers where the wastes are treated. If the activated sludge
process is in balance (a good secondary effluent with BOD and
suspended solids levels less than 20 or 25 mg/L) for routinely
experienced high flows, then the plant should perform as ex-
pected. If flows increase significantly, a switch to step-feed
aereation (Section 11.93) may be necessary to avoid loss of
the activated sludge bacteria. This solution will be effective if it
causes a reduction in the mixed liquor suspended solids fed to
the secondary clarifiers. If the influent solids loading increases,
the mixed liquor suspended solids may have to be increased to
treat these wastes by reducing the sludge wasting rate.
11.541	Aeration Tank Environment
If a good effluent is being produced, maintain a DO of 2 to 4
mg/L and thorough mixing throughout the entire aeration tank.
Recall from the previous section that if significant changes
occurred in the influent solids, adjustments were made to the
mixed liquor suspended solids by regulating the waste sludge
rate. If there is a white foam on the aeration tank surface,
reduce sludge wasting rates. If there is a thick, dark foam on
the tank surface, increase the sludge wasting rates.
' Biological cultures should be subject to slow changes rather than
rapid ones: therefore, the pounds wasted will be removed during a
24-hour period.

-------
50 Treatment Plants
11.542	Secondary Clarifier
Hopefully your effluent is always clear and free of solids. The
settleability test is a good indication of how solids will settle in a
clarifier. Adjust the return sludge rate so the sludge blanket will
stay as low as possible in the clarifier. REMEMBER THAT THE
SLUDGE BLANKET CAN INCREASE OR RISE WITH EITHER
AN INCREASE OR A DECREASE IN THE RETURN SLUDGE
RATE as a result of either an increase or decrease in detention
time. This increase or decrease in detention time also can be
caused by changes in the influent flow. For these reasons you
must keep good records and experiment to find the best return
rate for the conditions in your plant. See Section 11.6, "Opera-
tional Problems," for different types of solids that may be ob-
served on the surface of the clarifier or the plant effluent and
possible solutions to the problems.
11.543	Plant Effluent
The turbidity test using a turbidimeter is a quick way to de-
termine the quality of your plant effluent. When your plant is
operating properly, try to determine why. Plot trend charts de-
scribing influent characteristics, aeration tank and secondary
clarifier conditions, and effluent characteristics. When prob-
lems start to develop, try to determine why and correct the
situation. Remember that influent and process environmental
conditions (such as temperature) are continuously changing
and you must adjust for these changes.
11.55 Actual Operation Under Normal Conditions
This section describes the operational strategy of an effi-
ciently operating activated sludge plant. REMEMBER that
every plant is different and that YOU must develop a strategy
that works for YOUR PLANT.
The example plant is an activated sludge plant that operates
in the contact stabilization mode with diffused aeration provid-
ing complete mixing in the aeration tanks. It was designed to
treat a flow of 20 MGD. During the month studied the peak flow
was 29.1 MGD due to a storm and the peak influent BOD was
500 mgIL as a result of an industrial waste spill of methanol. In
spite of the abnormal events, the operator produced an aver-
age effluent BOD of 9 mgIL with a maximum BOD of 16 mg IL.
The effluent suspended solids averaged 13 mg IL and the
maximum was 27 mgIL. This excellent effluent was produced
because EVERY OPERATOR ON EVERY SHIFT FOLLOWED
THE SAME OPERATIONAL STRATEGY.
11.550 Initial Inspection
At the start of every shift, the shift operator goes through the
following steps.
1. Review the log book.
a.	Has anything unusual happened? If so, were any cor-
rections required and has the problem been corrected?
b.	Check the status of the return sludge pumps and waste
sludge pumps.
c.	What are the levels of DO in the aerators? Keep the DO
in the reaerator between 1.0 and 2.0 mgIL. Maintain a
DO of 3.5 to 4.0 mg IL in all three aerators.
NOTE: This DO level may be higher than what is rec-
ommended or required for most plants, but is essential
for this particular plant in order to maintain DO in the
secondary clarifiers.
d.	If chlorinating the return sludge flow for control of fila-
mentous growths, be sure to check the pounds of
chlorine applied per day.
2.	Visually inspect the activated sludge process.
a.	Is there any foam on the surface of the aerators? If so,
is it white or a thick, dark foam?
b.	Do the secondary clarifiers appear normal? Are they
turbid or are there any solids on the surfaces? Check
the depth of the sludge blanket in each clarifier. If the
sludge blanket is high, be sure the return sludge pumps
are working properly.
NOTE: In this plant the sludge blanket is kept as low as
possible in order to maintain aerobic conditions in the
secondary clarifiers.
c.	Inspect the effluent from the secondary clarifiers. The
effluent should be clear and free of suspended solids
and floatables.
3.	Review lab results.
a.	SVI
If the SVI is high, something is wrong. Collect a sample
of aerator mixed liquor and examine under a mi-
croscope for the typical numbers, types and condition
of the mixed liquor microorganisms. If there is an ex-
cess or lack of any type of microorganism, carefully
inspect the laboratory data. Look for unusual values for
(1)	pounds of volatile suspended solids under aeration,
(2)	sludge wasting rates, (3) air usage, and (4) dis-
solved oxygen levels in the reaerator and aerators. If
the microscopic examination of the mixed liquor indi-
cates an excess of normal filamentous mi-
croorganisms, then chlorination of the return activated
sludge should be started.
b.	Pounds of volatile matter under aeration.
Check the suspended solids levels in mgJL and percent
volatile matter in both the reaerator and aerators.
c.	Sludge wasting rate.
Adjust the sludge wasting rate to maintain the desired
pounds of volatile matter under aeration.
d.	Air usage.
Examine air usage in millions of cubic feet per day
needed to maintain desired DO levels in the reaerator
and aerators. Air required serves as an excellent indi-
cation of influent BOD and solids that will be produced
in the aerator that will have to be wasted.
e.	Microorganisms in aeration tank.
Examine microorganisms in aerator under a mi-
croscope and look for filamentous growths. If the SVI is
in the normal range, this examination will indicate the
normal numbers, types and condition of the mi-
croorganisms.
11.551 Process Adjustment
Table 11.3 contains a portion of the data available to the
operator for controlling the activated sludge process. Figures
11.18 and 11.19 show the results of plotting the lab data. YOU
must decide what information to plot that will help you carry out
your operational strategy. The remainder of this section de-
scribes how the operator of this plant identified a potential
problem and corrected it BEFORE there was any major deteri-
oration of the effluent quality.
Lab data indicated that the SVIs were high during the first
four days of the month. An inspection of the mixed liquor under
a microscope on the first day revealed excessive filamentous
growths. Chlorination of the return sludge was started and con-
tinued until the SVIs dropped down to normal and the exces-
sive filamentous growths disappeared on the fifth day.

-------
Activated Sludge 51
On the second day of the month a storm started and reached
a peak flow of 29.2 MGD on the third day. The percent volatile
matter in the reaerator and aerator suspended solids dropped
below 80 percent. The waste sludge rate had to be carefully
decreased to maintain the desired pounds of volatile matter
under aeration and to build the percent volatile matter under
aeration back up to 80 percent.
An industrial waste spill containing methanol hit the plant on
the 27th day of the month. The air requirement immediately
increased drastically due to the COD of the methanol and the
increased activity of the microorganisms. The waste sludge
rate had to be increased the next day to maintain the desired
pounds of volatile matter under aeration and to prevent solids
from escaping in the effluent.
In spite of three different problems resulting from filament-
ous growths, a storm and an industrial spill, Figure 11.18 re-
veals that by sticking to this plant's operational strategy, the
operators produced a consistently high quality effluent. The
key to success was the fact that the process was adjusted
BEFORE the effluent deteriorated by identifying the causes of
changes in the aeration tank environment and taking appropri-
ate corrective action immediately.
TABLE 11.3 SELECTED LABORATORY DATA FOR MARCH
Date
Day
Flow,
BOD
COD
Sus
Sol
Sus
Sol
Vol
Sol
Total
F/M
Waste
Air
SVI


MGD
Infl
Effl
Infl
Infl
Effl
Reaer
Aera
Reaer
Aer®
Vol
Ratio
lbsc
MCFd




mg/L
mg/L
mg/L
mg/L
mg/L
mg/L
mg/L
%
%
lbsb

day
day

1
W
19.9
440
8
992
436
8
8060
2150
83
82
95786
.43
44298 g
80.2
270
2
T
22.3
430
11
957
540
18
8860
2160
80
80 e
98453
.66

50544

30.2
384
3
F
29.2
580
9
1420
682
11
9830
2510

81
80

109930
.38

59929

64.8
295
4
S
24.0
270
12
838
542
27
7930
2170

77
74

87353
.60

53041

51.2
248
5
S
18.8
280
10
770
586
16
8880
2380

73
72

98932
.17

39474

39.0
109
6
M
20.0
360
12
894
456
12
9470
2140

72
72

91818
.38!
59156

56.6
98
7
T
20.0
380
8
992
502
26
6090
3050

71
72

85877
.56 |
36112

61.8
125
8
W
21.7
350
6
881
476
11
8690
2180

74
77

91710
.75 j
50152

72.5
92
9
T
20.0
340
8
770
380
14
8370
1750
75
79
83716
.44
42931
66.3
-
10
F
25.0
360
9
846
430
16
6070
2040
76
78
74570
.56
24350
68.2
98
11
S
19.9
400
6
710
476
16
8580
2390
76
79
97214
.38
33130
43.7
106
12
S
17.1
210
6
650
380
6
7820
1790
77
75
80672
.25
21131
32.0
156
13
M
21.3
380
9
930
424
6
8220
1990
76
78
87313
.45
23720
65.8
106
14
T
21.2
400
9
920
430
8
8960
2160
78
82 f
98466
.47
38335
72.4
113
15
W
20.9
440
16
1000
472
21
8720
2680
80
[_67j
98913
.49
44798
77.5
101
16
T
19.1
380
8
927
450
12
8410
2080
81
84
96448
.43
46362
75.3
135
17
F
16.3
350
6
907
428
11
7070
1950
82
87
86835
.38
34965
66.0
133
18
S
16.5
320
5
720
418
14
6120
1830
84
89
79820
.31
23785
42.0
131
19
S
15.4
200
6
620
360
11
5460
1800
84
85
72937
.25
15665
36.4
138
20
M
16.3
400
9
1040
470
8
5430
1590
82
84
67433
.54
13812
51.5
151
21
T
15.4
460
14
1080
416
8
6300
1940
84
86
81982
.50
20176
71.4
155
22
W
15.8
420
6
986
432
9
6620
2120
85
86
88288
.37
28213
69.4
189
23
T
15.1
400
6
888
418
12
6410
1990
85
85
83811
.33
29510
62.2
347
24
F
14.8
360
8
848
414
13
5940
1900
86
90
81395
.21
22689
57.5
289
25
S
16.2
220
8
797
400
14
5490
1800
85
84
73218
.30
15567
42.0
183
26
S
14.2
260
8
700
396
14
5850
1710
84
85
74451
.22
14442
38.4
292
27
M
20.3
420
16
1010
489
14
6330
1510
83
93
75674
.54
18530
58.9
h
152
28
T
20.4
440
7
961
428
12
6960
1770
85
88
84673
.52

25889
82.1

158
29
W
20.3
480
7
1120
438
8
7180
1810
86
85
86398
.63

30360
94.2

138
30
T
20.8
500
8
1200
616
7
7870
1880
86
88
93977
.54

40300
97.1

144
31
F
21.9
410
7
952
320
10
7710
1870
87
91
74545
.60

38709
92.0

128
Ave

19.1
368
9
914
455
13
7390
2035
81
82
87777
.44
33551
63.5
172
a.	Middle of three aeration tanks
b.	lbs x 0.454 = kg
c.	lbs/day x 0.454 = kg/day
d.	MCF/day x 0.0283 = Million cu m/day
e.	Drop in percent volatile
matter due to storm.
f.	Lab error.
g.	Carefully increase solids wasting
rate due to storm.
h.	Increased air requirements and
increase solids wasting due to
industrial dump of methanol.
i.	Filamentous growths. Increase
chlorine dose to return sludge.

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52 Treatment Plants
600 --
500 --
«0
Q
§ 400
t-
300 -
20 -
10 -
INFLUENT SS
INFLUENT BOD 1 j
FLOW, MGD
EFFLUENT SS
EFFLUENT BOD
DAYS
Fig. 11.18 Flow and influent and effluent
BOD and suspended solids

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100
50
100
50
250
200
150
90
80
20
10
Activated Sludge 53
IA
STORM
V\A
V\V \
WASTE
V\V \	X /
l i wl
-A >^AIR	r"\
/YNN	/	/'	/ I
/ \ x /	* '	\ /	I	METHANOL
I \ N-'	Nv/'	l\	SPILL
/N
FILAMENTOUS GROWTHS
STORM
AERATOR VOLATILE MATTER
¦ ¦ t
J—U
EFFLUENT BOO
-L-l.
» 1 ' ' ¦ 1
10
15
DAYS
20
25
30
Fig. 11.19 Process adjustment information

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54 Treatment Plants
11.56 Actual Operation Under Abnormal Conditions
Some wastewater treatment plants become seriously over-
loaded during certain times of the year, such as during the
canning season. Figure 11.20 shows the extent of overload our
example activated sludge plant experiences during the can-
ning season. To meet the NPDES permit requirement of
80,000 pounds of BOD per month, the operator estimated the
effluent BOD using daily COD tests. Figure 11.21 shows the
cumulative plots of both the estimated BOD using the COD test
results and the actual effluent BOD which was obtained five
days later. Use of the COD test results allows the operator to
make changes immediately when a problem develops, rather
than waiting five days and also avoiding violating NPDES per-
mit requirements.
Under the overloaded conditions the operator had to work
very hard to meet the daily, seven-day average and monthly
NPDES permit requirements. Both the blowers and return
sludge pumps worked at full capacity the entire month. Ferric
chloride was added in the primary clarifier to reduce the solids
and BOD loadings on the activated sludge process. Towards
the end of the month a portion of the effluent had to be diverted
to storage oxidation ponds in order for the plant to meet permit
requirements.
11.57 Summary
After a plant is started, the sampling and laboratory testing
program must be continued to identify and correct operational
problems whenever they start to develop. See Lesson 6 for
possible approaches to solving operational problems.
QUESTIONS
Write your answers in a notebook and then compare your
answers with those on page 84.
11.5A Why must some activated sludge be wasted?
11,5B Where is the best place for excess activated sludge to
be wasted?
11,5C Calculate the sludge age for an activated sludge pro-
cess if the aerator volume is 0.5 MG and the mixed
liquor suspended solids concentration is 2100 mg/l
The influent flow is 4.0 MGD, and the primary effluent
suspended solids concentration is 70 mg/L.
6NP OF L0&OH $ 0P&M&OM
(VOUmx)
A^flVATgP &LUP6&
Please answer the discussion and review questions before
continuing with Lesson 6.
DISCUSSION AND REVIEW QUESTIONS
Chapter 11. ACTIVATED SLUDGE
(Lesson 5 of 8 Lessons)
Write the answers to these questions in your notebook be-
fore continuing. The problem numbering continues from Les-
son 4.
22.	Estimate the pounds of solids under aeration in a
200,000-gallon tank when the suspended solids concen-
tration is 1600 mg/L. Show your work.
23.	What level of dissolved oxygen should be maintained in
the aeration tank during start-up?
24.	What do the letters MLSS stand for?
25.	Calculate the desired pounds of mixed liquor suspended
solids in an aeration tank if the primary effluent suspended
solids are 1800 pounds per day and the loading is based
on a five-day sludge age. Show your work.
26.	Calculate the desired mixed liquor suspended solids con-
centration (mg/L) if 4000 lbs are desired in a 200,000-
gallon aeration tank. Show your work.
27.	If sludge should be wasted at a rate of 0.05 MGD, what
should be the waste pumping rate in GPM?
28.	Why must some activated sludge be wasted?

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Activated Sludge 55
TOTAL INFLUENT SUSPENDED SOLIDS, MILLION POUNDS
112,117 LBS/DAY-
(3,363,508 LBS/MONTH)
	 PLANT DESIGN
88,000 LBS/DAY OR
2,664 MILLION LBS/MONTH
DAYS
Fig. 11.20 Plant overload during canning season

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Treatment Plants
80 --
» EFFLUENT BOO
ESTIMATED USING COD—^ *
70
ACTUAL EFFLUENT BOD
50
CO
O
o
00
I-
z
UJ
3
_l
u.
u.
UJ
NPDES PERMIT
EFFLUENT BOD = 80,000 LBS/MO
30
5
10
25
0
20
DAYS
Fig. 11.21 Estimated and actual effluent BOD

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Activated Sludge 57
CHAPTER 11. ACTIVATED SLUDGE
OPERATION OF ACTIVATED SLUDGE PLANTS
(Lesson 6 of 8 Lessons)
11.6 OPERATIONAL PROBLEMS (ABNORMAL OPERA-
TION)
11.60 Typical Problems
An activated sludge plant can accept quite a shock load now
and then without adverse effects to the system, but it cannot
survive a continuous series of shock loads.
Many factors may change that the operator cannot antici-
pate or control but must compensate for by adjusting the oper-
ational controls. For example, a conventional activated sludge
plant has operated satisfactorily for several weeks. The sec-
ondary clarifier had good clarity of 68 inches (1.7 m) with a
Secchi disc, and the effluent BOD and suspended solids were
running from 5 to 18 mg/L. The aeration tanks had been main-
tained at 15,000 pounds (6,000 kg) of mixed liquor suspended
solids with a volatile content of 78.5 percent, and sludge age of
five days.
A minimum DO of 2.8 mg/L had been measured in the last
two-thirds of the aerator. Sludge wasting had been at a rate of
2000 lbs/day (900 kg/day) from the system.
This week the situation has changed; the clarity in the sec-
ondary tanks has dropped to 18 inches (0.5 m). The sus-
pended solids in the secondary clarifier effluent have remained
about the same, but the BOD test started five days ago came
out at 38 mg/L. If a COD test had been run at the time the BOD
was started, an operational correction could have been made
at that time.
Overall, the plant effluent has definitely deteriorated from the
previous week.
Only you and your records can determine the cause and
what corrective action should be taken.
Has plant flow increased or decreased? Have air rates been
maintained? Have you received some toxic or untreatable slug
dose in the effluent? Are your sludge return pump and lines
clear? Has the BOD load to the aeration tank changed? Have
mixed liquor solids been the same? These are just a few of the
conditions that may change effluent quality.
The difficult decision after determining the cause or probable
cause is — should a change be made? This is where an
operator's thorough knowledge of plant processes pays off. If
you know the situation is unusual and will only last a couple of
days, minor changes may quickly improve the effluent quality.
But if the condition occurred before and lasted several weeks
according to past records, a process change may be neces-
sary to compensate for it. This is where experience with your
plant and records plays an important role in activated sludge
operation.
BY KEEPING ACCURATE RECORDS you can find the de-
sirable operating range in terms of efficiency of waste removal
and cost of operation. Usually each plant will have some mixed
liquor suspended solids concentration where the plant will
function best. This concentration should produce a clear final
effluent, with low suspended solids and BOD of 8 to 20 mg/L.
However, depending on plant design, type of waste, and sea-
son of year, the best mixed liquor suspended solids concentra-
tion might be found to be anywhere from 1000 to 4000 mg/L.
When a satisfactory mixed liquor suspended solids concentra-
tion is found for a specific plant under certain conditions, the
operator should attempt to maintain this level until something
changes.
If the mixed liquor suspended solids are allowed to start
building up, the final effluent will begin to deteriorate by becom-
ing turbid. When the mixed liquor suspended solids are al-
lowed to increase too high for the conventional activated
sludge plant, other problems can develop. The previous return
sludge rate for the plant flow would not be sufficient. Return
rates may have to be increased considerably. If the return
sludge rate was not increased, the activated sludge in the final
clarifiers would build a higher blanket. The deep blanket in the
final tank could cause solids to be swept over the weirs during
peak flow.
Another limiting factor is aeration equipment. The amount of
oxygen supplied to the aerator also limits the microorganism
mass that can be maintained in an aerobic state. A high oxy-
gen demand in the aerator can be created by a high solids
content in the plant influent.
The other factor is the organisms themselves. If insufficient
food is available, only a limited number of organisms will
develop energy to multiply. This is where the struggle for survi-
val begins. When food supply is low, the microorganisms begin
to feed upon themselves. This is the period of most complete
oxidation, and new sludge production is at a minimum. Ex-
tended aeration plants are designed to operate under these
conditions which tend to increase solids in the plant effluent.
QUESTIONS
Write your answers in a notebook and then compare your
answers with those on page 84.
11,6A Why are plant records of the activated sludge opera-
tion important?
11.6B What could happen if the mixed liquor suspended sol-
ids were allowed to increase beyond the best range in
an activated sludge process?
11.61 Plant Changes
IF THE PLANT BECOMES UPSET, THE FIRST ACTION
BEFORE MAKING ANY CHANGES IS TO CHECK THE
PLANT DATA FOR AT LEAST THREE PREVIOUS WEEKS.
The problem probably started last week or earlier. To look for
the cause of the problem, ask yourself the following questions:
1. Have any changes been made to other plant units such as
the digesters or primary clarifiers? Was a digester super-
natant with excessive amounts of solids returned to the
primary clarifiers? Return of supernatant should be slow
and easy at low-load periods. Digester supernatant solids
mixed with raw wastewater and waste activated sludge may
create a light sludge that may be washed out of the primary
clarifier. The solids washed out of the primary clarifier
create undesirable recycle and loading problems.

-------
58 Treatment Plants
2.	Have plant daily flows and waste concentrations increased
or decreased? Heavy rains following a dry spell, a new
industrial plant, or a different process discharge from an
existing industry can cause problems.
3.	Has temperature of the influent changed a significant
amount?
4.	Has the sampling program been consistent?
Most of the time a plant upset is due to some in-plant prob-
lem and not the influent raw wastewater, unless your plant is
frequently overloaded.
CONDITION 1: (High Solids in Digester Supernatant)
A high solids content in digester supernatant can throw a
curve to the operator. The solids in digester supernatants are
usually high in immediate oxygen demand and contain high
colloidal and dissolved solids. If a large quantity of low volatile
content solids escapes from the primary clarifier to the aeration
system, several undesirable events occur. The supernatant
solids are picked up by the activated sludge in the aerator and
carried through the system. This creates extra oxygen de-
mand, and air output must be increased. Digester solids make
a good settling activated sludge, but the color of the floe will be
darker. Total pounds of solids in the aerator will increase due
to the supernatant solids, and the operator will normally in-
crease waste sludge rates to hold the established range of
solids or sludge age. Consequently, the effluent from the plant
deteriorates. Why? Lab tests show that the solids in the aerator
are at the desired level, and DO of the mixed liquor has been
held at 2.0 mgIL (probably more air was required).
What has occurred is that by wasting apparently excess
activated sludge, many of the microorganisms have been re-
placed in the aerator by digested or inert solids. They are
sampled the same as mixed liquor suspended solids and are
included as total pounds of solids under aeration. THIS IS WHY
MANY PLANTS BASE AERATOR LOADINGS ON MIXED
LIQUOR VOLATILE SUSPENDED SOLIDS AND NOT MIXED
LIQUOR SUSPENDED SOLIDS. They are making the as-
sumption that the volatile content of the mixed liquor sus-
pended solids represents microorganisms.
Most activated sludge mixed liquor suspended solids fall into
a range of 70 to 80 percent volatile content for municipal waste
when the process is operating properly. This would mean that
if you are striving to maintain a sludge age of five days, you are
attempting to maintain a prescribed number of organisms for
every pound of food applied to the aeration tanks. A five-day
sludge age is equivalent to 20 pounds of food for every 100
pounds of organisms. When the supernatant was admitted into
the aeration tank, the pounds of solids in the aerator was in-
creased. When sludge was wasted to maintain the five-day
sludge age, many of the organisms needed to treat the incom-
ing wastes were replaced by the inert supernatant solids. This
placed a higher food load on the remaining organisms of
maybe 30 to 35 pounds per 100 pounds of organisms and
reduced the effective sludge age from five days to possibly 3.5
days.
Storm flow may sweep excessive silt into the plant by infiltra-
tion into sewers or through combined sewer systems. Solids
increase drastically but the percent of volatile solids may drop
to 50 percent of the total solids. If you measure only total solids
in this type of situation, it will appear that you have excess
solids that need to be removed. However, wasting solids at this
point may produce serious organism losses.
In the example plant, the supernatant solids may not appear
to produce much of a change, but over a period of several days
the system could become severely upset. When the total
pounds of volatile solids in the aerator becomes too low due to
excessive amounts of inert solids from digester supernatant or
storm inflow, the solution to the problem is to reduce or stop
wasting sludge for several days. This will provide the time
necessary to rebuild the microorganism population to handle
the incoming waste load.
Try to hold solids in the digester a little longer and try to
increase solids concentration in the sludge fed to the digester.
It is possible that the poor supernatant was due to overloading
the digester and/or insufficient seed sludge in the digester. In
this case the problem "snowballs" — first the digester is over-
loaded, then supernatant solids overload the aerator which
overloads the clarifier, and the problem keeps getting worse.
CONDITION 2: (Flow or Waste Changes)
Always be alert for the possibility of toxic dumps, accidental
spills (particularly the midnight variety), storms, or other up-
sewer factors that may change the influent flow or waste
characteristics.
A frequent problem is the increased flows from storm infiltra-
tion or other sources. These flows may create shorter aeration
times or loss of activated sludge solids from the final clarifiers
due to a hydraulic overload. To compensate for this condition,
regulate return and waste sludge rates to hold as much of the
solids as possible in the aerator. Or change plant operation to
step-feed or contact stabilization mode of operation (see Sec-
tions 11.91, "Contact Stabilization" and 11.93, "Step-Feed
Aeration").
Changes in waste characteristics may be caused by isolated
dumps or spills, or changes may be seasonal. Become ac-
quainted with plant managers whose activities may cause
changes in the waste loadings on your plant and encourage
these people to notify you whenever a problem discharge oc-
curs. Try to convince them to release unusual dumps at a low
discharge rate rather than all at once. Certain industries such
as canneries create seasonal problems which the operator
should prepare for in advance.
CONDITION 3: (Temperature Changes)
The activated sludge system is influenced by temperature
changes similar to the response of trickling filters to tempera-
ture changes in spring and fall. During the summer, the acti-
vated sludge plant may operate satisfactorily in a certain load-
ing range and air rates, but in winter the best loading ranges
and air rates change and the plant requires less air and more
solids under aeration. Usually a temperature change is not
significant unless it raises or lowers the wastewater tempera-
ture more than 10°F (6°C).
Temperature is an important factor in oxidation relative to
sludge accumulation. A high temperature produces a rapid
microorganism growth rate and more waste storage in the or-
ganism cell with less oxidation. Therefore, lower biological ac-
tivity will result in more overall sludge production but the sludge
may be thinner than usual.
CONDITION 4: (Changes in Sampling Program)
Data on system performance can be greatly affected by
changes in a sampling program. If improper sampling locations

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Activated Sludge 59
or laboratory procedures are used, lab results could vary con-
siderably. When the lab data varies widely from one day to the
next, check sampling location, time and lab procedures for
errors.
When considering a major process change, first review
the plant data. Next, make only one major change at a time.
If two changes are made, you won't know whether one or
both changes provided the corrective action. When a
change is made, give the system at least one week before
attempting another change or modification. Don't make too
many changes too fast.
QUESTIONS
Write your answers in a notebook and then compare your
answers with those on page 84.
11.6C How would you determine the best solids loading for
an aerator?
11.6D What would you do if an activated sludge plant be-
came upset?
11,6E (a) What can happen if a digester supernatant with a
high solids content is returned to the primary
clarifier?
(b) How can this be remedied?
11.6F How would you correct or compensate for an upset
created by high flows from storm water infiltration?
11.6G How would you correct an upset apparently caused by
a temperature difference due to seasonal changes?
11,6H What would you do if a review of the lab data revealed
considerable variation from day to day?
11.61	How long would you allow an activated sludge process
to react and stabilize after a change?
11.62	Sludge Bulking
Bulking is the term applied to the condition in which the
mixed liquor solids tend to show a very slow settling rate and
compact to a limited extent. The liquid that does separate from
the solids usually has excellent clarity but generally there is not
enough time for complete removal of the solids in the second-
ary clarifier. The sludge blanket in the clarifier becomes deeper
and rises to overflow the weirs and is discharged with the
effluent.
Bulking may be associated with production of a highly jelly-
like, water-logged (hydrated) sludge that has a very low sludge
density. At other times, FILAMENTOUS ORGANISMS16 may
grow from one floe mass to another and act as stay rods to
prevent compaction of the sludge particles and produce poor
settling results.
Low pH, low DO, and low nitrogen concentrations have been
related to bulking. High food-to-microorganism loading rates
(low sludge ages) are the major causes of repeated bulking.
Organisms that grow rapidly tend to spread out and will not
clump or form a floe mass until growth rates decrease. It is
difficult to retain enough low-density (light) sludge to decrease
the food-to-microorganism load ratio (or increase sludge age)
without chemical flocculation or other tricks to increase the
sludge density (weight). A rain may provide enough silt to favor
increased sludge density. Low loads during weekends may
help. Addition of some pre-aerated digested sludge (Kraus
process, Section 11.92) helps reduce bulking. Some of the
POLYELECTROLYTE17 FLOCCULENV8 aids are very effec-
tive in controlling a bulking activated sludge. If it is possible,
bulking may be reduced by decreasing the load to the aeration
tanks until the sludge becomes sufficiently oxidized to floccu-
late. Addition of clay or bentonite has been used to control
bulking.
The main objective of most bulking control procedures is to
increase sludge age or decrease the ratio of waste (food) load
added per day per unit of mixed liquor volatile solids in the
aerator. Some good methods for holding solids under aeration
are the addition of aluminum sulfate (Al2 (S04)3 • 14 H,0) or
iron ferric chloride (FeCU. Also, ferric sulfate (Fe2 (S04)3 • 3
HzO) may be used as a flocculent with alkaline (lime) addition
to prevent the alkalinity from dropping below 50 to 100 mgIL as
Ca C03. The proper polyelectrolyte may cost more than other
chemicals, but alkali addition may not be required to increase
the alkalinity.
Chlorination is not an effective cure because chlorine inacti-
vates the organisms that are needed to treat the wastes.
Effluent turbidity may increase for several days after an appli-
cation of chlorine. Bulking is likely to return unless the cause is
identified and permanently corrected.
When bulking occurs it will generally be associated with the
load ratio or sludge age. Plant records should be reviewed in
an attempt to locate the cause of the problem. Identification of
the cause will not remedy the present bulking condition, but
should be considered a valuable lesson, and measures should
be taken to prevent the same conditions from occurring again.
To prevent sludge bulking from occurring, the following
items should be carefully controlled in an activated sludge
plant:
1.	SUITABLE SLUDGE AGE. Carefully review plant records
and maintain a sludge age that produces the best quality
effluent. Watch influent solids loadings, maintain desired
level of solids in the aerator, and carefully regulate waste
sludge rates. Generally, bulking may be cured by increas-
ing the sludge age.
2.	LOW DO. Prevent low levels of DO from developing. Mi>«Bd
liquor DO tests are a quick and simple test, or a DO probe
will give you a continuous reading. There is no valid excuse
for low DO concentrations during normal conditions if suffi-
cient oxygenation capacity is available, unless a slug of
waste with an excessive oxygen demand is received.
3.	SHORT AERATION PERIOD. Bulking caused by the aera-
tion period being too short is usually the result of a design
problem, unless the operator has formed the habit of return-
ing too high a volume of return sludge. To correct this prob-
lem, reduce the return sludge rate and thicken the return
sludge solids concentration by COAGULATION19 (if neces-
16	Filamentous organism (FILL-a-men-tous). Organisms that grow in a thread or filamentous form. Common types are thiothrix and actinomy-
ces.
17	Polyelectrolyte (POLY-eiectro-light). A high-molecular weight substance that is formed by either a natural or synthetic process. Natural
polyelectrolytes may be of biological origin or derived from starch products, cellulose derivatives, and allgnates. Synthetic polyelectrolytes
consist of simple substances that have been made into complex, high-molecular-weight substances. Often called a "polymer."
is Flocculation (FLOCK-you-LAY-shun). The gathering together of fine particles to form larger particles.
18	Coagulation (ko-AGG-u-LAY-shun). The use of chemicals that cause very fine particles to clump together Into larger particles. This makes
it easier to separate the solids from the liquids by settling, skimming, draining or filtering.

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60 Treatment Plants
sary). In this way you still return the same number of or-
ganisms to meet the new food (waste) entering the aerator,
but effectively reduce the total flow through the aerator and
clarifier.
4. FILAMENTOUS GROWTH. The growth of filamentous or-
ganisms may be caused by incorrect sludge age or nutri-
tional differences, such as a shortage or abundance of nit-
rogen, phosphorus, or carbon. If filamentous growths are
allowed to become well established, they create a difficult
problem to overcome. Control may be achieved by increas-
ing MLSS (more microorganisms which will increase sludge
age), by maintaining higher DO's and in special instances
supplementing a nutrient deficiency.
11.63 Septic Sludge
Septic sludge may be produced when any type of sludge
remains too long in such places as hoppers and channels. It is
likely to cause a foul odor, rises slowly, and sometimes rises in
clumps. Even small amounts can upset an aerator.
Septic sludge may occur in poorly designed or constructed
hoppers, wet wells, channels, or pipe systems. This occurs
when activated sludge is allowed to be deposited and
anaerobic decomposition starts. Septic sludge deposits also
may develop on the floor of the aerator due to insufficient air
rates that are not keeping the tank completely mixed. A high
solids load also can cause septic problems.
To effectively control septic sludge, aerators must be thor-
oughly mixed and sludge must be pumped frequently. In chan-
nels and pipelines, a velocity over 1.5 feet per second (0.45
m/sec) will prevent the formation of sludge deposits that could
become septic.
Sludge going septic in the secondary clarifier may develop
from four causes:
1.	Return sludge rate too low, thus holding the solids in the
final clarifier too long and allowing them to become septic.
2.	Clarifier collection mechanism turned off, thus the sludge is
not being moved to the draw-off hopper.
3.	Sludge draw-off lines plugged, obstructed, or used in-
frequently.
4.	Return sludge pump off or a valve closed.
A good operator checks the system several times a day. In
most new activated sludge plants the secondary clarifiers have
air lift samplers or photocells to indicate sludge blanket level in
the tank. Whenever the final clarifier sludge blanket level
changes, an immediate investigation should be undertaken. In
any of the cases above, the correction is quite obvious —
restore suitable return sludge flow as soon as possible.
11.64 Toxic Substances
Toxicity causes a severe slowdown or death of working or-
ganisms and produces system and effluent up sets. The
operator has limited control over toxic waste entering the plant.
When this happens, however, sludge wasting should be
stopped immediately and all available solids returned to the
aerator. Toxic materials such as heavy metals, acids, insec-
ticides, and pesticides should never be dumped into a sewer
system without proper control.
11.65 Rising Sludge
Rising sludge is not to be confused with bulking. The sludge
settles and compacts satisfactorily on the bottom of the
clarifier, but after settling it rises to the top of the secondary
tank in patches or small particles the size of a pea. Rising
sludge usually produces a fine scum or froth (brown in color)
on the surface of the aeration and secondary tanks.
Rising sludge is caused by DENITRIFICATION20 or SEPTIC-
ITY21 and results from too long a detention time in the secon-
dary clarifiers. The secondary clarifiers should be equipped
with scum baffles and skimmers to prevent these solids from
escaping in the plant effluent.
Denitrification is most common when the sludge age is high
(extended aeration). When this type of activated sludge flows
from the aerator to the secondary clarifier or becomes short of
oxygen, the organisms first use the available dissolved oxygen
and the oxygen in the nitrate compounds resulting in the re-
lease of nitrogen gas. Denitrification is an indication of good
treatment, providing the sludge in the settleability test stays on
the bottom of the cylinder for at least one hour, but floats to the
surface in two hours. If it floats up too early in the settleability
test, the sludge age should be reduced or the food-to-micro-
organism ratio should be increased. This solution will be suc-
cessful if the nitrifying bacteria are washed out of the system. If
the sludge stays down for an hour in the settleability test but
problems are still present in the secondary clarifier, increase
the return sludge rates to move the solids out of the clarifier at
a faster rate. Under some circumstances this will not help and
better results might be obtained by decreasing the return
sludge rate, so be careful.
Rising sludge also may be controlled by increasing the load
to the aerator by removing a primary clarifier from service if
more than one is being used. During low flow periods, raw
wastewater may be discharged directly to the aerator. Another
possibility is to check the possibility of going to a tapered aera-
tion diffuser placement.
11.66 Foaming/Frothing
Aerator foaming or frothing has been a problem for some
plants. There have been many theories presented on the
cause, such as surfactants (detergents), polysaccharides, and
over-aeration. Whatever the cause, there is a definite relation-
ship between froth buildup on the aerator and the amount of
suspended solids in the mixed liquor and air supply to the
aerator.
For control:
1.	Maintain higher mixed liquor suspended solids concentra-
tions;
2.	Reduce air supply during periods of low flow while still main-
taining DO; and
3.	Return supernatant to the aeration tank during low flows (be
caution in this method — supernatant should be returned
slowly and steadily because too much supernatant could
cause an excess oxygen demand).
These solutions apply only to detergent foam. In some ex-
tended aeration systems or nitrification systems (Chapter 21),
20	denitrification. A condition that occurs when nitrite or nitrate ions are reduced to nitrogen gas and bubbles are formed as a result of this
process. The bubbles attach to the biological floes and float the floes to the surface of the secondary clarifiers. This condition is often the
cause of rising sludge observed in secondary clarifiers.
21	Septicity (sep- TIS-it-tee). Septicity is the condition in which organic matter decomposes to form foul-smelling products associated with the
absence of free oxygen. If severe, the wastewater turns black, gives off foul odors, contains little or no dissolved oxygen and creates a heavy
oxygen demand.

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Activated Sludge 61
a froth builds up that can sometimes be controlled by higher
sludge wasting rates.
Most plants are equipped with water sprays along the
aerator to dissipate the foam. If mixed liquor solids are allowed
to be reduced, low water sprays will not be sufficient to hold the
foam. When this occurs, two problems develop — mainte-
nance and safety.
SAFETY FIRST — The froth from an aerator is an excellent
vehicle for minute grease particles and, when deposited on
"Y" walls or walks, will leave a grease deposit that is very
slippery. More than one operator has been injured by slip-
ping on a walk or step previously coated with foam.
This deposit not only is unsafe, but unsightly, and it must be
cleaned up immediately. The best way to remove this type of
deposit is with water (preferably hot), trisodium phosphate
(TSP), and a stiff bristle deck brush. Wet the area to be
cleaned, lightly sprinkle TSP granules on the area, let the TSP
dissolve for a few minutes, and then brush the area to spread
the TSP and loosen the grease. Let it work for five minutes,
rebrush, and then hose off.
QUESTIONS
Write your answers in a notebook and then compare your
answers with those on page 85.
11.6J How can froth or foam be controlled in an aerator?
11,6K How can grease deposits (from foam) on walks be
removed?
11.6L How would you differentiate between bulking and ris-
ing sludge?
11.6M What would you do to correct a rising sludge problem?
W OFLS^OtidOP.
(VOLUM&
ACTlVATEP'^tU
Please answer the discussion and review questions before
continuing with Lesson 7.
DISCUSSION AND REVIEW QUESTIONS
Chapter 11. ACTIVATED SLUDGE
(Lesson 6 of 8 Lessons)
Write the answers to these questions in your notebook be-
fore continuing. The problem numbering continues from Les-
son 5.
29.	When an activated sludge plant becomes upset what
should the operator do first?
30.	Why do many activated sludge plants base aerator load-
ings on mixed liquor VOLATILE suspended solids and not
total mixed liquor suspended solids?
31.	When attempting to correct an upset activated sludge pro-
cess, why should only one major change be made at a
time?
32.	Is sludge bulking undesirable? Why?
33.	What is the purpose of the 60-minute Settleability Test?
34.	What safety hazard can a frothing aerator cause?

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62 Treatment Plants
CHAPTER 11. ACTIVATED SLUDGE
OPERATION OF ACTIVATED SLUDGE PLANTS
(Lesson 7 of 8 Lessons)
11.7 AERATOR LOADING GUIDELINES
11.70	Use of Loading Guidelines
The activated sludge process can be controlled by changes
in the aerator loadings based on sludge age, food/
microorganism ratio, or mean cell residence time (MCRT). All
three methods of control are mathematically similar. In each
case, the operator begins operations with aerator loadings
based on data and the experience of other similar plants. This
value (loading rate) is then adjusted by the operator until the
operating range is found that produces the best quality effluent
for the plant.
The critical factor in any method of aeration tank control is
the food/microorganism relationship and this cannot be pre-
cisely estimated for any specific plant. The operator tries to
keep enough solids (microorganisms) in the aeration tank to
use up the incoming waste (food). Neither too many organisms
nor too few organisms should be in the aeration tank in relation
to the incoming food. Operation of the activated sludge pro-
cess requires removing the organisms (settled activated
sludge) from the secondary clarifier as quickly as possible. The
organisms are either returned to the aerator to use the incom-
ing food, or they are wasted. This procedure has been dis-
cussed and an example provided in Section 11.52 using
sludge age to determine the aerator loading value. Select a
method to operate your plant and stick with it. Don't continually
try to switch form one method to another.
11.71	Fopd/Microorganism Ratio
The food-to-microorganism loading ratio is based upon the
FOOD PROVIDED each day to the microorganism mass in the
aerator. Food (waste) provided is preferably measured by the
COD of the influent to the aerator. COD is recommended be-
cause test results are available within four hours and process
changes can be made before the process becomes upset.
Many operators load aerators on the basis of the BOD test, but
results five days later are too late for operational control.
If you know the amount of waste (food) entering the aerator,
you can provide sufficient organisms in the aerator to treat
(eat) the incoming waste. You estimate the amount of or-
ganisms in the aerator by measuring the suspended solids in
the mixed liquor (MLSS). The Mixed Liquor Suspended Solids
consist of both organic (volatile) and inorganic material. The
organic portion represents the organisms available to treat the
incoming waste. Thus by measuring the mixed liquor volatile
suspended solids (MLVSS), you have a more accurate meas-
ure of the organisms present to treat the incoming waste.
MLSS is a measure of organisms and inorganic or inert mate-
rials present, but MLVSS is a more accurate measure for con-
trol purposes because only organisms and organic materials
are measured.
Typical loading guidelines (ranges) have been established
for the three operational zones of activated sludge and are
summarized as follows:
1.	HIGH-RATE
COD: >1 * lb COD per day/1 lb of MLVSS under aeration
BOD: >0.5* lb BOD per day/1 lb of MLVSS under aera-
tion
2.	CONVENTIONAL
COD: 0.5 to 1.0 lb COD per day/1 lb of MLVSS under
aeration
BOD: 0.25 to 0.5 lb BOD per day/1 lb of MLVSS under
aeration
3.	EXTENDED AERATION
COD: <0.2** lb COD per day/1 lb MLVSS under aeration
BOD: <0.10** lb BOD per day/1 lb MLVSS under aeration
* > means greater than. Greater than 1 lb COD.
" < means less than. Less than 0.2 lb COD.
11.72 Calculation of Food/Microorganism Aerator
Loading
Determine the amount of mixed liquor volatile suspended
solids to be maintained in the aerator of the conventional plant
studied in this chapter. Assume a food/microorganism ratio of
0.5.lb	COD per day/1 lb of mixed liquor volatile suspended
solids under aeration. Frequently this loading is expressed as
50 lbs COD per day/100 lbs of MLVSS.
Information needed:
1.	Average COD of primary effluent, 150 mg/L
2.	Average daily flow, 4.0 MGD
FIND POUNDS OF COD PROVIDED TO AERATOR PER
DAY.
Aerator
Loading,	= Prim Effl COD, mg/L x Daily Flow, MGD x 8.34 lbs/gal
lbs C0D	= 150 mg/L x 4.0 MGD x 8.34 lbs/gal
day	= 5004 or 5000 lbs COD/day
FIND DESIRED POUNDS OF MIXED LIQUOR VOLATILE
SUSPENDED SOLIDS UNDER AERATION, BASED UPON
0.5 LB COD PER DAY/1 LB OF MLVSS.
MLVSS lbs =	Primary Effluent COD, lbs/day	
Loading Factor in lbs COD/day/1 lb MLVSS
5000 lbs COD/day
0.5 lb COD/day/lb MLVSS
5000
0.5/lbs MLVSS
= 10,000 lbs MLVSS under aeration
The MLVSS is a measure of the organisms in the aerator
available to work on the incoming waste. When operating your
plant on the basis of MLVSS, you should note any fluctuations
that may occur during the week and make appropriate adjust-
ment.

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Activated Sludge 63
If the COD load applied to the aerator increases or drops to a
significantly different level for two consecutive days, a new
mixed liquor solids value should be calculated and activated
sludge wasting adjusted to achieve the new value of solids
desired under aeration. Calculation of waste sludge rates is
outlined in Sections 11.52 and 11.53.
11.73	Mean Cell Residence Time (MCRT)
Another approach for solids control used by operators is the
Mean Cell Residence Time (MCRT) or Solids Retention Time
(SRT). This is a refinement of the sludge age. Both terms are
almost the same. The equation for MCRT is:
MCRT, = 	Pounds of Suspended Solids in Aeration System*	
days Lbs of Susp Sol Wasted/day + Lbs of Susp Sol Lost in Effl/day
The most desirable MCRT for a given plant is determined
experimentally just as with the use of sludge age or the mixed
liquor volatile suspended solids concentration. The desired
MCRT for conventional plant operation should fall between 5
and 15 days. (Don't confuse this time with the recommended
range for Sludge Age of 3.5 to 10 days.)
*NOTE: There are THREE different ways to calculate the
pounds of suspended solids in the aeration system!
1.	MLSS, mgIL x Aerator Vol, MG x 8.34 lbs/gal
2.	MLSS, mg/L x (Aerator Vol, MG + Final Clar Vol, MG) x
8.34 lbs/gal
3.	[MLSS, mg/L x Aerator Vol, MG + Return Sludge SS, mg/Z.
x Sludge Blanket Vol, MG] x 8.34 lbs/gal
The first method is illustrated in this section, but you may use
whichever method you prefer and will produce satisfactory re-
sults for your plant.
A way of determining MCRT for the example plant in this
chapter would be as follows:
Required Data:
1.	Aerator
2.	Final clarifier volume
3.	Wastewater flow to aerator
4.	Waste sludge flow for past 24 hrs
5.	Mixed liquor suspended solids
concentration
6.	Waste sludge (or return sludge)
suspended solids concentration
7.	Final effluent suspended solids
concentration	= 12 mg/L
11.74	Calculation of Mean Cell Residence Time
= 1,000,000 gals
= 500,000 gals
= 4.0 MGD
= 0.075 MGD
= 2400 mg/L
= 6200 mg/Z.
MCRT,
days
	Suspended Solids In Aeration System, lbs	
Susp Sol Wasted, lbs/day + Susp Sol Lost in Effl, lbs/day*
MCRT _ Susp Sol in Mixed Liq, mgIL x Aerator, MG x 8.34 lbs/day
(Susp Sol in Waste, mg/L x Waste Rate, MGD x 8.34 lbs/gal)
+ (Susp Sol in Effl, mg/L x Plant Flow, MGD x 8.34 lbs/gal)
2400 mg/L x 1.0 MG x 8.34 lbs/gal
(6200 mg/L x 0.075 MGD x 8.34 lbs/gal)
-i- (12 mg/L x 4.0 MGD x 8.34 lbs/gal)
20,016 lbs	
3878 lbs/day + 400 lbs/day
= 20,016 lbs
4278 lbs/day
= 4.7 days
'NOTE: Some operators use volatile suspended solids in-
stead of suspended solids.
If you are operating the plant on the basis of MCRT and the
plant operates satisfactorily at the MCRT of 8, 9, 10, 11, or
even 15 days, the main method of control is to adjust the waste
sludge rate to maintain the MCRT at the desired number of
days.
Rearranging the equation in the previous column, calcula-
tion of the sludge waste rate from the system merely means
plugging in the chosen MCRT (use 4.7 days) and solids fig-
ures.
EXAMPLE:
Waste
Sludge, = Susp Sol in System, lbs _ Susp So, in Eff, ,bs/day
lbs/day	MCRT, days
_2400 mg/L x 1.0 MG x 8.34 lbs/gal
4.7 days
- 12 mg/L x 4.0 MGD x 8.34 lbs/gal
_ 20,016 lbs _ 400 ibs/day
4.7 days
= 4259 lbs/day - 400 lbs/day
= 3859 lbs/day
The waste sludge pumping rate of 3878 lbs/day appears to
be correct to maintain a Mean Cell Residence Time of 4.7
days.
QUESTIONS
Write your answers in a notebook and then compare your
answers with those on page 85.
11.7A Why is it sometimes necessary to waste some acti-
vated sludge?
11,7B If you calculate that your plant has 12,000 pounds of
mixed liquor volatile suspended solids under aeration
and you need 9,000 pounds under aeration, how many
pounds should be wasted?
11,7C What should be the waste sludge pumping rate (GPM)
if a plant should be wasting 3000 pounds per day and
the concentration of return sludge is 6000 mg/L?
11,7D Estimate the waste sludge rate (lbs/day) from an acti-
vated sludge plant operating at an MCRT of 10 days.
The system contains 40,000 pounds of suspended sol-
ids and the effluent has a suspended solids concentra-
tion of 10 mg/L at a flow of 5 MGD.
11.8 ACTIVATED SLUDGE PROCESS EQUIPMENT
11.80 Need for Understanding Equipment
Always read and understand manufacturers' literature be-
fore starting, operating, maintaining or shutting down equip-
ment. You may be very capable of operating the activated
sludge process, but if your equipment does not perform, life
can be very difficult. Proper shutdown procedures may be
overlooked in manufacturers' literature and O&M manuals. If
proper shutdown procedures are not followed, equipment can
be damaged and not start again properly.
This section will identify important steps to follow when shut-
ting down aeration system equipment, when attempting to
handle abnormal conditions or troubleshooting problems and
when maintaining equipment. Remember that these steps are
general and you must prepare your own detailed list if one is
not available. There are many equipment manufacturers in
business today and they are continually improving their prod-
ucts; therefore the lists in this section are presented to guide
you in the preparation of your own lists for the equipment in
your plant.

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64 Treatment Plants
11.81 Shutdown
11.810	Surface Aerators
Aerator shutdown is required when any maintenance service
is performed to prevent injury to maintenance personnel and
possible damage to equipment.
1.	Turn the "on-off-auto" switch to "off."
2.	Turn the main power breaker "off."
3.	Lock-out and tag the main power breaker in the "off' posi-
tion.
Maintenance service may be performed now.
11.811	Positive Displacement Blowers
Blower shutdown is required when any maintenance service
is performed in order to prevent injury to maintenance person-
nel and possible damage to equipment.
1.	Turn the "on-off-auto" or "on-off" switch to "off."
2.	Turn the main power breaker "off."
3.	Lock-out and tag the main power breaker in the "off" posi-
tion.
4.	Close the discharge and suction valves.
When the blower is shut down, insure that the check valve
closes and seats. Many blowers run backwards for a mo-
ment or two after shutdown and this reverse operation
creates a vacuum condition which will pull liquid up the
headers and into the air distribution system.
Maintenance service may be performed now.
11.812	Centrifugal Blowers
Blower shutdown is REQUIRED when any maintenance
service is performed to prevent injury to maintenance person-
nel and possible damage to equipment.
1.	Depress the stop button.
2.	Open the bypass valve.
3.	Close the discharge valve.
4.	Let the auxiliary oil pump run for a 10-minute post-
lubrication period. This allows the bearings and gears to
cool gradually.
5.	Turn the control panel power to "off."
6.	Turn the main power breakers to "off."
7.	Lock-out and tag the main power breakers in the "off' posi-
tion.
Maintenance service may be performed now.
11.813	Mr Distribution System
Periodically, the air distribution system may need to be shut
down for repairs, modifications, or cleaning. If your distribution
system is composed of different pipes serving different plant
processes, and if regulating/Isolation valves have been in-
stalled, the section to be serviced may be shut down effectively
by closing the regulating/isolation valve. Keep in mind that
when closing down a section of the distribution system, an
increase of air flow, head loss, and system pressure in the
active sections of the distribution system may occur.
Where only one or no regulating/isolation valve is installed or
there is only one distribution line, the blower must be shut
down before service on the distribution system begins. CAU-
TION: Before service begins on the distribution system, the
regulating/isolation valve(s) or the blower must be locked out
and tagged to prevent air from entering the system.
Do not attempt to repair even the smallest leaks or dis-
crepancies in the distribution system unless the system is shut
down. Although 6.0 to 10.0 psi (0.4 to 0.7 kg/sq cm) system
pressure may not seem like much, SERIOUS BODILY INJURY
may result from escaping air or foreign material.
11.814 Air Headers and Dlffusers
Before shutting down the headers) or diffusers, mark the
valve position of the butterfly valve or count the number of
turns that a gate valve is open and record it. This will provide a
ready reference for positioning the valve when the header(s)
and diffusers are returned to service.
Close the header(s) regulating/isolation valve.
QUESTIONS
Write your answers in a notebook and then compare your
answers with those on page 85.
11.8A Why must both surface aerators and blowers be shut
down before any maintenance service is performed?
11.8B List the steps you would follow to shut down an aerator.
11.8C Before service begins on the air distribution system,
why should the regulating/isolation valve(s) or the
blower be locked out and tagged?
11.8D Why should the air distribution system be shut down
before attempting to repair even the smallest leaks?
11.82 Abnormal Conditions
When making routine checks and inspections you may oc-
casionally find some abnormal conditions. Serious damage
may result to the equipment if these conditions are not cor-
rected as soon as possible. Listed in the Tables in this section
are some abnormal conditions for activated sludge process
equipment, possible causes, and operator response to the
conditions that will aid you in the safe and efficient operation of
the equipment in your plant. As you become familiar with your
plant and discover abnormal conditions, add the causes and
your response to these tables for use by other operators in
your plant.
11.820	Surface Aerators
Table 11.4 lists abnormal surface aerator conditions, possi-
ble causes and operator response. High oil temperature and
motor amperage are not uncommon when "breaking In" a new
or overhauled surface aerator.
11.821	Air Filters
The difference in pressure recorded by the manometers will
be small when the fitters are clean, but as they become dirtier,
the manometer reading will increase and the fluid in each tube
will move farther away from the manometer zero mark. When
this difference reaches approximately two to three inches (50
to75 mm) of water column more than the initial (clean filters)
difference, it is time to clean the filters.

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Activated Sludge 65
TABLE 11.4 ABNORMAL SURFACE AERATOR OPERATION
ITEM
ABNORMAL CONDITION
POSSIBLE CAUSE
OPERATOR RESPONSE
Motor
High or uneven amperage
Moisture
Winding breakdown
Have electrician MEG®
check motor. Have
motor rewound.
Degree of impeller submergence
results in amperage draw in excess
of motor amperage design.
Adjust aerator.
Excessive motor bearing or gear
reducer friction
Inspect and lubricate
bearings and gears.
Overhaul if needed.
Gear Reducer
Bearing or gear noise
Lack of proper lubrication
Repair or replace
oil pump. Change
oil.
Remove obstruction
in oil line.
Shaft Coupling
Unusual noise and vibration
Cracked coupling
Replace coupling.
Align impeller shaft.
Loose coupling bolts/nuts as
a result of vibration.
Torque bolts.6 Use
"locking" nuts.
Align impeller shaft.
Impeller
Unusual noise and vibration
Loose blades
Torque blade bolts."
Use lock-washers.
Align impeller.
Cracked blades
Replace. Torque bolts.b
Align.
* Use Instrument (megger) to check insulation resistance o1 motor.
b Tighten bolts to manufacturer's torque rating. Ratings are given in foot-pounds or kilogram-meters.

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66 Treatment Plants
11.822 Blowers
Blower operation is ESSENTIAL for the efficient operation
of the activated sludge process, and any other in-plant pro-
cess that requires blower-supplied air. Loss of blower air for
an extended period of time (longer than four hours) will turn
the plant into an upset and cause bulking of the activated
sludge process. Table 11.5 lists abnormal blower conditions,
possible causes and operator response. High oil tempera-
ture, oil pressure, and motor amperage are not uncommon or
abnormal when "breaking in" a new or overhauled blower
unit. Realize that your response to an abnormal condition
may depend on the type of blower and blower manufacturer.
11.823 Air Distribution System
Although there are only a few moving parts connected with
the air distribution system, failures in the system can be ex-
pected. Table 11.6 lists some abnormal conditions, possible
causes and the operator's response to the conditions that will
aid you in the safe and efficient operation and maintenance of
the air distribution system.
11.824	Air Headers
The wet and corrosive environment that the header is ex-
posed to, the upward water current drag forces exerted on
the header, vibration, and normal deterioration all contribute
to the abnormal conditions listed in Table 11.7 that should be
anticipated.
11.825	Air Diffusers
Abnormal operation of the fine-bubble diffusers is usually the
result of the porous surfaces clogging due to dirt and biological
growths. Abnormal operation of the coarse-bubble diffusers,
though infrequent, is usually the result of clogging due to
biological growth or broken diffusers. Table 11.8 lists some
abnormal conditions, possible causes, and the operator's re-
sponse to the conditions that will aid you in the efficient opera-
tion and maintenance of the air diffusers.
QUESTIONS
Write your answers in a notebook and then compare your
answers with those on page 85.
11.8E What factors might cause the motor on a surface
aerator to draw a high or uneven amperage?
11.8F How can you determine if filters need cleaning if the
filter chamber does not have a manometer?
11.8G What can clog fine-bubble diffusers?
11.83 Maintenance
A comprehensive preventative maintenance program is an
essential part of plant operations. Proper maintenance will in-
sure longer and better equipment performance than equipment
that is given little, if any care. This section should be used as a
guideline in performing the required maintenance on activated
sludge process equipment. For more detailed information on
maintenance, see Chapter 15, "Maintenance," your treatment
plant's operation and maintenance manual, and the manufac-
turer's manuals.
11.830	Surface Aerators
MOTORS
Motors should be greased after about 2000 hours of opera-
tion. The motor must be stopped when greasing begins.
Remove filler and drain plugs, free the drain hole of any
hardened grease, add new grease through the filler hole until it
starts to come out of the drain hole. Start the motor and let it
run for about 15 minutes to expel any excess grease. Stop the
motor and install the filler and drain plugs.
After about 5 years of operation, the motor windings may
tend to deteriorate due to moisture and heat. Have the motor
inspected and removed from service for repair by an au-
thorized motor repair facility.
GEAR REDUCER
Generally all new oil-lubricated equipment has a "break-in"
period of about 400 hours. After this time the oil should be
drained from the gear reducer, the reservoir flushed and new
oil added. This procedure removes fine metal particles that
have worn off of the internal components as a result of the
initial close tolerances as the equipment was "breaking-in." If
large quantities of fine metal particles are found after the
"break-in" period, the manufacturer should be consulted.
A high quality turbine-type oil is normally used in the gear
reducer assembly. After an oil change has been completed
and with the reducer assembly inspection plates removed, in-
spect the gears for proper operation and the oil for proper flow.
Grease-lubricated bearings should be greased about every
500 hours of operation, depending on service conditions.
NOTE: More damage is done to bearings by overgreasing than
undergreasing.
Oil for gears and bearings should be changed after about
1400 hours of operation under normal service and more fre-
quently when required. NOTE: The proper type of oil is a
necessity. If it is too thin or too thick, it will impede proper
functioning of bearings and gears.
COUPLING AND IMPELLER
Every 6 to 12 months the aerator should be stopped and all
bolts and nuts on the impeller and coupling should be re-
torqued according to the manufacturer's specifications. This is
also a good time to inspect the metal surfaces for deterioration
such as cracks or worn components. While the unit is "off,"
check the impeller and shaft for proper alignment.
After performing routine maintenance, the unit and surround-
ing area must be wiped or washed. Be sure to remove any
spilled oil or grease. Dispose of oil- and grease-soiled rags in a
covered container to avoid a fire hazard.
11.831	Air Filters
When filter cleaning is scheduled, remove the filters from the
filter chamber and check the inside of the chamber. Remove
any sand, dirt, paper, water, or other debris.
Usually filters may be cleaned by using a relatively high
pressure clean water or by steam cleaning. The filter manufac-
turer's equipment manual should be consulted for the recom-
mended method of cleaning your particular type of filter.
Allow the filters to dry, securely install the filters in the filter
chamber, and insure that no tools or other items are left in the
filter chamber that could be drawn into the blowers.

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Activated Sludge 67
TABLE 11.5 ABNORMAL BLOWER OPERATION
ITEM
ABNORMAL CONDITION
POSSIBLE CAUSE
OPERATOR RESPONSE
Unusual noise
or vibration
Coupling misaligned
Incorrect installation
Align coupling with
blower at operating
temperature according
to manufacturer.
Loose nuts, bolts, or screws
Vibration
Tighten.
Air system
pressure
Low pressure
By-pass valve open, leaks or breaks
in distribution piping
Close valve, repair
leaks or breaks.
Diffusers came off air header
Replace diffusers.
High pressure
Blockage or partially closed valve
in distribution piping
Remove blockage
or open valve.
Plugged diffusers
Blow out or remove
and clean.
Air flow
Low total flow
High ambient temperatures
Add more air if needed.
Blower air control malfunction
Repair or replace
control.
System oil
pressure
Low pressure
Oil level too low
Add oil.
Oil filter dirty
Replace.
Check valve sticks open
Replace valve.
Incorrect oil type
Drain and refill
with proper oil type.
High pressure
Incorrect oil type
Drain and refill
with proper oil type.
Oil discharge
pressure
Low pressure
Suction lift too high
Reduce lift.
Air or vapor in oil
Purge air at filter.
Coupling slipping on pump shaft
Secure coupling.
Oil temperature
Low temperature
Oil cooler water flow too high
Throttle water flow.
High temperature
Oil cooler water flow too low
Increase water flow.
Incorrect oil type
Drain and refill with
proper oil type.
Insufficient oil circulation
Replace oil filter,
check oil lines for
restrictions.
Bearings
Hot bearing(s)
Blower speed too high
Reduce speed to
recommended RPM.
Defective bearing(s)
Check bearing(s) for
clearance, hot spots,
cracks or other
damage. Repair or
replace.
Oil cooler water flow too low
Increase water flow.
Motor
Won't start
Overload relay tripped
Correct and reset.
Noisy
Noisy bearing
Check and lubricate.
High temperature
Restricted ventilation
Check openings and
duct work for
obstructions.
Electrical
Check for grounded
or shorted colls and
unbalanced voltages
between phases.

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68 Treatment Plants
TABLE 11.6 ABNORMAL AIR DISTRIBUTION SYSTEM OPERATION
ITEM
ABNORMAL CONDITION
POSSIBLE CAUSE
OPERATOR RESPONSE
Meter(s)
High, low, or no Indication
Loose movement
Tighten or replace.
Out of calibration
Calibrate.
Dirt in mechanism
Clean.
Pointer dragging on scale plate
Adjust pointer.
By-pass valve open or leaking
Close or repair.
Meter piping leaks
Tighten or replace.
Meter piping plugged
Clean piping.
Seals, gaskets, and
flex connections
Leaking
Loose bolts or fittings
Tighten.
Blown-out
Replace.
Worn
Usual deterioration
Replace.
Pipe
Corrosion
Condensate
Drain traps daily,
install additional traps,
flush pipe, paint pipe,
and/or remove standing
water from around pipe.
Sludge inside pipe
Vacuum action by blower operating
in reverse
Rush pipe, install
check valve on blower,
and/or repair check
valve.
Dirt
No or inefficient air filtration
Install filters. Clean
filters more frequently.
Valves
Difficult to operate or
frozen
Hardened grease
Remove old grease and
apply seizing* inhibitor.
Operate valves monthly.
Corrosion
Drain condensate
traps daily. Apply
seizing inhibitor.
* Seizing. Seizing occurs when an engine overheats and a component expands so the engine will not run. Also called "freezing."

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Activated Sludge 69
TABLE 11.7 ABNORMAL AIR HEADER OPERATION
ITEM
ABNORMAL CONDITION
POSSIBLE CAUSE
OPERATOR RESPONSE
Valve
Valve leaks at stem
Loose stem packing nut
Tighten nut.
Defective packing
Secure distribution
system and replace
packing.
Valve will not seat closed
Corrosion
Secure distribution
system and clean or
replace valve.
Butterfly rubber seat defective
Secure distribution
system and replace
rubber seat.
Butterfly, or gate has come off
valve system
Secure distribution
system and replace
Swing header
pivot joints
Air leaks from joint
Defective "0" ring
Close header valve,
pull header from tank
with crane and replace
"0" ring.
Loose joint
Tighten.
Insufficient grease in joint
Apply 3 to 5 shots of
grease.
Cracked joint
Replace.
Fixed header
couplings or
unions
Air leaks from couplings,
unions, or end caps
PVC has defective glue bond
Remove, clean with PVC
solvent, bond and
allow bond to cure.
Pipe has leak through thread
Remove, apply teflon
tape, tighten.
Horizontal
header
Uneven water motion
(roll) in tank
Header not perfectly level, thus
allowing more air to one side
Level header with
surveyor's level (tank
empty) or use Mason's
level.
"0" rings or gaskets defective
or connections loose
Replace "0" rings or
gaskets. Tighten
connections.
Header pipe
Interior corrosion
Moisture
Use PVC or galvanized
pipe.
Exterior corrosion
Moisture
Use PVC, galvanized
pipe, or paint pipe
with an epoxy coating.
Electrolysis
Use a sacrificial
(magnesium) anode or
coat surface.

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70 Treatment Plants
TABLE 11.8 ABNORMAL AIR DIFFUSER OPERATION
ITEM
ABNORMAL CONDITION
POSSIBLE CAUSE
OPERATOR RESPONSE
Fine-bubble
diffuser
Exterior clogged
Biological growth
Raise air header, remove dif-
fuser, scrub and wash diffuser.
Interior clogged
Dirt from distribution
system
Raise air header, remove dif-
fuser, scrub and wash diffuser.
Install filters, clean filters
more frequently.
Coarse-bubble
diffuser
Exterior clogged
Biological growth
Raise air header, scrub and wash
diffuser. Once a month increase
air flow 2 to 3 times normal for
15 minutes to "blow out" diffuser
orifices.
Cracked
Overtightened when
installed, structural failure
Replace.
Fine-arid coarse-
bubble diffusers
Accumulation of rags,
hair, string
Inefficient pre-treatment,
normal conditions
Yearly, raise headers and clean
diffusers.
Insufficient diffusion
pattern or oxygen
transfer
Clogged diffusers
Clean the diffusers.
Inadequate diffuser
arrangement
Modify diffuser arrangement.
Too few diffusers
Add diffusers or install a
different type.
11.832 Blowers
Generally all new oil-lubricated equipment has a "break-in"
period of about 400 hours. After this time the oil should be
drained from the blower, the reservoir and filter cleaned and
flushed, and new oil added. This procedure removes fine metal
particles that have worn off of the internal components as a
result of the initial close tolerances as the equipment was
"breaking-in." If large quantities of fine metal particles are
found after the "break-in" period, the manufacturer should be
consulted.
Grease-tubricated bearings should be greased about every
500 hours of operation, depending on service conditions.
NOTE: More damage is done to bearings by overgreasing than
undergreasing.
Oil for gears and bearings should be changed and the filters
cleaned about every 1400 hours of operation under normal
service, more frequently when required. NOTE: The proper
grade of oil is a necessity. If it is too thin or thick it will impede
proper functioning of bearings and gears.
See Section 11.830, "Surface Aerators," MOTORS, for a
discussion on blower motors. Maintenance on blower motors is
similar to maintenance of surface .aerator motors.
After performing routine maintenance, the units and sur-
rounding area must be wiped or washed, removing any spilled
oil or grease. Dispose of oil-soiled rags in a covered container.
A routine should be established whereby the blower, pres-
sure relief valve, and blower suction and discharge valves are
operated to prevent the equipment from SEIZING22 up and
becoming inoperable. Blowers that are not routinely in service
should be operated at least six hours per week on a given day.
Pressure relief valves should be checked at least once per
month by manually lifting the valve off of the valve seat. Test
the pressure relief valve for the correct setting by SLOWLY
closing the blower discharge valve SLIGHTLY, with the blower
operating, until the pressure relief valve opens. Observing the
air system pressure gage while noting when the relief valve
opens will alert you to the pressure setting at that time. Instruc-
tions for making adjustments on the pressure relief valve and
the proper setting for your blower installation should be con-
tained in the manufacturer's manual. NOTE: When testing the
pressure relief valve, DO NOT CLOSE THE BLOWER DIS-
CHARGE VALVE COMPLETELY or serious damage to the
blower may result. Use this test procedure ONLY if the pres-
sure relief valve is located between the blower and the dis-
charge valve.
Never use any oil or grease on the pressure relief valve. Due
to the heat generated by compressing air, oil and grease lubri-
cants will harden and may keep the pressure relief valve from
opening. A metal seizing inhibitor may be applied and is gen-
erally available from most hardware stores.
Blower suction and discharge valves should be operated
once a month, with the blower off, by fully closing and opening
the valves. A metal seizing inhibitor should also be applied to
the gear assembly of each valve.
The blower check valve should be checked once a month for
free operation by opening and closing the valve while checking
that the valve seats properly when it is in the closed position.
22 Seizing. Seizing occurs when an engine overheats and a component expands so the engine will not run. Also called "freezing."

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Activated Sludge 71
11.833 Air Distribution System
Depending on the harshness of the environment surround-
ing the distribution piping, an inspection schedule should be
established for the entire piping system from at least once
monthly to once every six months. During this inspection, look
for loose pipe support clamps or cracked pipe support welds,
shifting of pipe out of original position due to structural settling,
loose nuts and bolts on fittings, stuck or difficult to operate
valves, and damage from corrosion.
Exterior pipe, fittings, and valve surfaces should be painted
with a primer coat and a finish coat. Painting should be done as
frequently as needed to prevent and inhibit corrosion. Meters
should be calibrated at least once a year to insure meter accu-
racy.
All valves in the distribution system, including meter valves,
should be fully opened and fully closed once a month (with
blowers off) to insure free operation.
For more detailed information on maintenance of your me-
ters, fittings, valves, and pipes consult your manufacturer's
manual, the plant operation and maintenance manual, and
Chapter 15, "Maintenance," of this training manual.
11.834 Air Headers
Due to the severe environment that the headers are ex-
posed to, a maintenance program should be adopted so that
header failure and resultant lengthy down time can be
minimized or avoided. The following activities should be
scheduled on a monthly and yearly basis.
1- Monthly
a.	Fully close and open all regulating/isolation valves to
insure free operation.
b.	Apply 3 to 5 shots of grease to the upper pivot swing
joint "O" ring cavity (swing header).
c.	Check for loose fittings, bolts and nuts. Secure if loose.
2. Yearly
a.	Raise headers, clean and check for loose bolts, nuts,
and fittings. Secure if loose.
b.	Apply 3 to 5 shots of grease to the pivot joint "O" ring
cavity (swing header).
c.	Check for corrosion. Properly prepare pipe and paint
with epoxy coating where needed.
Hydraulic fluid in the swing header hoist should be changed
at least once yearly.
A weatherproof tarpaulin should be provided to cover the
hoist to protect it from the elements when it is not in use.
Secure the tarpaulin to the hoist to prevent the wind from blow-
ing it into the tanks.
11.835 Diffusers
Maintenance activities that should be scheduled on a
monthly and yearly basis are listed in this section.
1.	Monthly
Increase the air flow to the diffusers 2 to 3 times normal for
about 15 minutes to "blow out" the biological growths that
have accumulated around the diffuser orifices.
2.	Yearly, or as conditions warrant
Raise the air header from the tank and clean diffusers,
inspect for damage, and replace as needed.
Diffusers that are allowed to remain in a defective condition
reduce the diffusers' effectiveness and will result in inefficient
wastewater treatment.
QUESTIONS
Write your answers in a notebook and then compare your
answers with those on page 85.
11,8H What causes motor windings to deteriorate?
11.81 How are air filters cleaned?
11,8J What causes equipment to "seize up" and become in-
operable?
ACTIVATE? &LUP6&
Please answer the discussion and review questions before
continuing with Lesson 8.


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72 Treatment Plants
DISCUSSION AND REVIEW QUESTIONS
Chapter 11. ACTIVATED SLUDGE
(Lesson 7 of 8 Lessons)
Write the answers to these questions in your notebook be-
fore continuing. The problem numbering continues from Les-
son 6.
35.	What is the formula for calculating the Mean Cell Resi-
dence Time?
36.	Calculate the MCRT for an activated sludge process.
Plant inflow is 4.0 MGD, MLSS is 2700 mg/L, waste
sludge flow 0.05 MGD, aeration system volume is 2.0 MG,
waste sludge suspended solids concentration is 6500
mg/L, and final effluent suspended solids concentration is
15 mg/L.
37.	Why must proper equipment shutdown procedures be fol-
lowed?
38.	Why should you develop your own lists of shutdown pro-
cedures for equipment in your plant?
39.	How would you dispose of oil- and grease-soaked rags
and why?
CHAPTER 11. ACTIVATED SLUDGE PLANTS
OPERATION OF ACTIVATED SLUDGE PLANTS
(Lesson 8 of 8 Lessons)
11.9 MODIFICATIONS OF THE ACTIVATED SLUDGE
PROCESS
11.90	Reasons for Other Modes of Operation
Edification of the conventional activated sludge process
has been developed to improve operational results under cer-
tain circumstances. Some of these conditions may be:
1.	Current or actual loadings are in excess of design loading
for conventional operation.
2.	Wastewater constituents require added nutrients to prop-
erly treat influent waste load.
3.	Flow or strength of waste varies seasonally.
11.91	Contact Stabilization (Fig. 11.22)
Operation of an activated sludge plant on the basis of con-
tact stabilization requires two aeration tanks. One tank is for
separate re-aeration of the return sludge for at least four hours
before it is permitted to flow into the other aeration tank to be
mixed with the primary effluent requiring treatment. Overall
loading factors are the same as for conventional activated
sludge.
If the solids content in aeration tank "A" (mixed liquor
aerator, Fig. 11.22) and aeration tank "B" (return sludge aera-
tion only) are combined, the loading ratio of food/
microorganisms is the same as conventional operation. How-
ever, if you only look at aeration tank "A" where the load is
applied, we approach double the load ratio established for
conventional activated sludge.
Contact stabilization attempts to have organisms assimilate
(take in) and store large portions of the influent waste load in a
short time (as short as 30 minutes). The activated sludge is
separated from the treated wastewater in the secondary
clarifier and returned to the re-aeration tank "B." No new food
is added to the re-aeration tank and the organisms must use
the waste material they collected and stored in the first aera-
tion tank. When the stored food is used up, the organisms
begin searching for more food and are ready to be returned to
tank "A."
Process controls for a contact stabilization plant are the
same as those described for a conventional plant in this chap-
ter. The contact stabilization system with its off-stream reser-
voir of organisms in aeration tank "B" avoids a complete solids
"wash-out" when high flows occur or a "kill" of microorganisms
when toxic wastes reach the plant. When calculating loading
guidelines, the solids in the reaeration tank may be ignored.
You must realize that the effluent quality will not be the same
as for loadings on the conventional process, but the results
from the calculations can be used to operate your plant and to
reveal any trends.
11.92 Kraus Process (Fig. 11.23)
The Kraus process is a modification of conventional acti-
vated sludge, and the process is patented by its developer.
The process is widely used when the wastewater contains a
much greater ratio of carbonaceous to nitrogenous material
than found in normal domestic wastewater and when activated
sludge has poor settling characteristics.
This nutrient imbalance commonly occurs when wastes from
canneries or dairies are treated. When the organisms use all of
a limiting constituent (nitrogen for example) they refuse to re-
move the remaining portions of the other constituents (carbon
for example). Normally this nutrient deficiency is nitrogenous
material which is readily available in anaerobic digester super-

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PRIMARY
EFFLUENT
MIXED LIQUOR
CLARIFIER
EFFLUENT
	V-
SECONDARY
CLARIFIER
RE-AERATED
RETURN
SLUDGE
RETURN SLUDGE
RETURN SLUDGE
RE-AERATION
AERATOR 'B'
MIXED LIQUOR
AERATOR 'A'
Fig. 11.22 Plan layout of contact stabilization plant

-------
J*
PRIMARY
CLARIFIER
SECONDARY
CLARIFIER
INFLUENT
EFFLUENT
RETURN SLUDGE
WASTE
SLUDGE
RETURN
SLUDGE
ANAEROBIC
DIGESTER
DIGESTER SLUDGE
AERATION
TANK 'B'
AERATION
TANK 'A'

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Activated Sludge 75
natant and sludges. Feeding anaerobic digester supernatant
or digester sludge to the aeration system will usually supply the
proper nutrients to maintain the balance and also add inert
suspended solids to assist with liquid-solid separation in the
clarifier. The method of supernatant application is very impor-
tant.
In the Kraus process, the return sludge is sent to the re-
aeration aerator ("B") to be mixed with the digested sludge
from a completely mixed digester. In the re-aeration tank ("B"),
the digested sludge and the return sludge are mixed, re-
aerated, and then sent to the mixed liquor aerator ("A"). The
amount of digested sludge introduced to the system is deter-
mined by laboratory evaluation and by carbonaceous material
removal through the system.
The same controls apply as described for controlling a con-
ventional activated sludge plant. The main objective is to prop-
erly balance nutrients; however, other advantages include in-
creased activated sludge settleability and (similar to contact
stabilization) a reservoir of organisms off the main processing
stream.
11.93 Step-Feed Aeration (Fig. 11.24)
Step-feed aeration actually is a step-feed process based on
conventional activated sludge loading guidelines. The differ-
ence between step-feed and conventional operation is that in
conventional activated sludge the primary effluent and return
sludge are introduced at one point only, the entrance to the
aeration tanks. In step-feed aeration the return sludge is intro-
duced separately and, in many cases, allowed a short re-
aeration period by itself at the entrance to the tank. The pri-
mary effluent is admitted to the aeration tanks at several differ-
ent locations. These locations distribute the waste load over
the aeration tank and reduce oxygen sags in an aerator. If you
introduce the influent near the outlet end of the aeration tank,
the process will become similar to contact stabilization.
Step-feed aeration distributes the oxygen demand from the
wastewater over the entire aerator instead of concentrating it
at the inlet end. Some of its advantages over conventional
operation include less aeration volume to treat the same vol-
umes of wastewater, better control in handling shock loads,
and the potential for lower applied solids to the secondary
clarifiers. When a conventional plant is operating above design
loads and/or the secondary clarifiers cannot handle the solids
load, switching to step-feed aeration or contact stabilization
allows the operator to maintain more solids under aeration with
a lower applied solids concentration to the secondary clarifiers.
Successful operation requires transfer of wastes into the acti-
vated sludge solids in the short time interval before the waste
reaches the effluent end of the aeration tank.
Step-feed aeration can be operated on a variable basis by
using combinations of the modes shown in Figure 11.24. For
example, use Mode 4 (contact stabilization) during peak flows
resulting from storms or when treating strong industrial wastes
in order to preserve the activated sludge solids in the system.
Peak flows could wash out the activated sludge solids or the
activated sludge culture could be killed by a strong industrial
waste if you were operating in Mode 1 (conventional activated
sludge process). Therefore, you would ideally operate in Mode
1 to treat ordinary domestic flows and switch to Modes 2, 3,
and eventually 4 depending on the quantity of industrial waste
flows, seasonal wastewaters or temperature variations in rela-
tion to operating partially or fully nitrified (see Chapter 21, "Ac-
tivated Sludge,") and/or the ability of your existing facility to
adequately process the existing flows.
Selection of the proper mode depends on influent charac-
teristics (flow rate and waste strength) and the capabilities of
the plant to handle these characteristics. Mode 1 is usually
best for providing maximum treatment of normal domestic
wastewaters because all of the wastewater is exposed to aera-
tion and microorganisms for the longest possible time which
will produce the highest degree of treatment. If your activated
sludge process develops a sludge bulking or rising sludge
problem, a shift to Modes 2, 3, or 4 would help to cure the
problem by (1) allowing more solids to be maintained in the
aeration system thus controlling the solids volume entering the
secondary clarifiers (more in aeration and less in clarification),
and (2) exposing the solids to a more evenly distributed
oxygenated environment which provides for healthy bugs
throughout the aeration system. When dealing with a bulking
sludge the problem is usually caused by inadequate dissolved
oxygen levels which are conducive to the growth of filamen-
tous organisms. Rising sludge usually results from high dis-
solved oxygen levels in the aerator and prolonged secondary
clarifier detention times which will cause denitrification.
When attempting to cure a bulking or rising sludge problem,
an increase in return sludge flows may be helpful to reduce
solids on a short-term basis. This procedure should not be
relied upon to solve the problem. Increased return sludge flows
will cause the sludge blanket in the secondary clarifier to drop
initially, yet the blanket could rise as the result of excessive
clarifier underflow rates. Try to find the return rate that pro-
duces the lowest sludge blanket and seek to correct the bulk-
ing or rising problem by modifying the aeration system opera-
tional mode. Your job as an operator is to select the best mode
that will do the best job for the normal wastewater characteris-
tics and meet effluent requirements.
The step-feed mode of operation is controlled by many of the
same procedures used for the conventional process. An ex-
ception is that the mixed liquor suspended solids determina-
tions must be made at each point of wastewater addition to
measure the waste content and dilution factor provided by the
primary effluent to determine the total pounds of solids in the
aeration tank.
11.94	Complete Mix (Fig. 11.25)
The complete mix mode of operation is a design modification
of tank mixing techniques to insure equal distribution of applied
waste load, dissolved oxygen, and return sludge throughout
the aeration tank. The theory of this modification is that all
parts of the aeration tank should be similar in terms of amount^
of food, organisms, and air. This is accomplished by providing
diffuser location and application points of influent and return
sludge to the aerator at several locations. Providing a similar
condition throughout the entire aeration tank allows a food/
organism ratio of 1/1 and still produces effluent qualities com-
parable to conventional operation. Generally, smaller aeration
tanks are more completely mixed than larger ones. Usually
aeration is more efficient in a complete mix facility such as
illustrated in Fig. 11.25 because of the locations of the air
headers.
11.95	Modified Aeration (Fig. 11.26)
Modified aeration is also known as high-rate activated
sludge. Frequently it is used as intermediate treatment where
the discharge requirements demand higher treatment than
primary, but not as high as conventional activated sludge, in
terms of BOD and suspended solids removals.
Either raw wastewater or primary effluent is applied to an
aeration tank with a detention time of two hours and a mixed
liquor suspended solids concentration of less than 1000 mg/L.
Air requirements are lower because of fewer organisms (sol-

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76 Treatment Plants
MODES OF FLOW
MODE 1
Return Sludge
100% Primary Effluent
\ Conventional Flow Activated Sludge Process
Aerator
Effluent
MODE 2
Return Sludge
Step-Feed
25% Primary Effluent
\
Aerator
Effluent
MODE 3
Return Sludge
Step-Feed
0%	331/a% 331/3% 331/3% Primary Effluent
\ \ \
. Aerator
r Effluent
MODE 4
Return Sludge
0%
Step-Feed
0%	50%	50% Primary Effluent
\ \ \
or Contact Stabilization
100% Influent
Aerator
Effluent
Several possible modes of feeding primary effluent to the aera-
tion tanks. Some tanks may have more or fewer points of
discharge into the tank.
Fig. 11.24 Modes of step aeration

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Activated Sludge
EFFLUENT
FROM AERATOR
RAW WASTE AND RETURN
SLUDGE INLET POINTS
'	PLAN VIEW
AIR HEADERS - NOTE VARIOUS POSITIONS
(HERRINGBONE PATTERN)
AIR
HEADERS
Fig. 11.25 Air header locations In complete mix

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78 Treatment Plants
PRIMARY EFFLUENT
OR RAW WASTEWATER
SECONDARY
CLARIFIER
EFFLUENT
RETURN
SLUDGE
ALTERNATE
ESS stuDGE
THICKENER
EXCESS SLUDGE TO PRIMARY INFLUENT
IF PRIMARY CLARIFIER AVAILABLE
AERATION TANK
2 HOURS DETENTION
Fig. 11.26 Modified aeration
ids) under aeration as a result of a younger sludge age or a
lower mean cell residence time. Effluent quality ranging from
primary treatment to conventional activated sludge treatment
can be achieved by the operator by controlling the air supply,
aeration period, and the pounds of solids under aeration.
11.10	ACKNOWLEDGMENT
Mr. F.J. Ludzack, Chemist, National Training Center, U.S.
Environmental Protection Agency, provided many helpful
comments to the original development of this chapter. His con-
tributions are gratefully appreciated.
11.11	ADDITIONAL READING
1.	MOP 11, Chapter 11*, "Activated Sludge."
2.	NEW YORK MANUAL, Chapter 6, "Secondary Treatment,
Activated Sludge," pages 58-69.
3.	TEXAS MANUAL, Chapter 13, "The Activated Sludge Pro-
cess."
4.	Jenkins, D., and Garrison, W.E., "Control of Activated
Sludge by Mean Cell Residence Time," JWPCF, Vol. 40,
No. 11, p. 1905 (November 1968).
5.	McKinney, R.E., and O'Brien, W.J., "Activated Sludge —
Basic Design Concepts," JWPCF, Vol. 40, No. 11, p. 1831
(November 1968).
6.	Stewart, M.J., "Activated Sludge Process Variables — The
Complete Spectrum," Water and Sewage Works Magazine,
Reference Volume, p. R-241 (November 30, 1964).
7.	AERATION PRACTICE, MOP No. 5, Water Pollution Con-
trol Federation, 2626 Pennsylvania Avenue, Washington,
D.C. 20037. $3.00 to members, $6.00 to others.
or
Journal Water Pollution Control Federation, Vol. 41, Nos.
11 and 12, and Vol. 42, No. 1 (November and December
1969 and January 1970).
8.	OPERATIONAL CONTROL PROCEDURES FOR THE AC-
TIVATED SLUDGE PROCESS, by Alfred W. West. Obtain
from U.S. Environmental Protection Agency, National Train-
ing and Operational Technology Center, Cincinnati, Ohio
45268. EPA-330/9-74-001.
The best documents available on how to control the acti-
vated sludge process.
9.	PROCESS MANUAL FOR AEROBIC BIOLOGICAL
WASTEWATER TREATMENT FACILITIES, EPA-430/9-
77-006, March 1977, Municipal Operations Branch, Office
of Water Program Operations, U.S. Environmental Protec-
tion Agency, Washington, D.C. 20460.
* Depends on edition.
W 0F L&&0N 0 QF&
T!» (voimtx) ^ ^
o n
g^ACTlVATgP	I
Please answer the discussion and review questions before
working the objective test.

-------
Activated Sludge 79
DISCUSSION AND REVIEW QUESTIONS
Chapter 11. ACTIVATED SLUDGE
(Lesson 8 of 8 Lessons)
Write the answers to these questions in your notebook be-
fore continuing. The problem numbering continues from Les-
son 7.
40.	Why might an operator wish to use step-feed aeration?
41.	What is the name of the treatment process that is capable
of producing effluents with a quality (BOD and suspended
solids) between primary treatment and conventional acti-
vated sludge?
42. How would you operate the step-feed aeration process
during:
1.	Peak flows; and
2.	Sludge bulking in the secondary clarifier?
PLEASE WORK THE OBJECTIVE TEST NEXT.
1112 METRIC CALCULATIONS
This section contains the solutions to all problems in this
chapter using metric calculations.
11.120 Conversion Factors
ft x 0.3048
= m
m x 3.281
-ft
lb x 0.454
= kg
kg x 2.205
= lb
MGD x 3785
= cu m/day
cu m/day x 0.000264
= MGD
GPM x 0.063
= Usee
Usee x 15.85
= GPM
1000 L
= 1 cu m
11.121 Problem Solutions
FROM SECTION 11.44 SIXTH DAY
1. Calculate the kilograms of solids under aeration in an aera-
tion tank.
Unknown
Solids Under Aeration, kg
Known
Aeration Tank Dimensions
Length, m = 30 m
Width, m = 14 m
Depth, m = 5 m
MLSS, mg/1. = 2000 mgIL
a.	Determine the aeration tank volume in cubic meters.
= Length, m x Width, m x Depth, m
= 30 m x 14 m x 5 m
= 2,100 cu m
b.	Calculate kilograms of solids under aeration.
Solids, = MLSS mg/L x Tank Vo, cu m x 1 k9 x 1'00
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80 Treatment Plants
2. Determine if the existing return sludge pumping rate is
satisfactory.
Known
Flow to Aerator
from Prim.
Clar., cu/day
Return Sludge
Flow, cu m/day
Vol of MLSS
Settled in 60
minutes, %
Unknown
= 15,000 cu m/day Desired Return
Sludge Flow,
cu m/day
= 4,000 cu m/day Return Sludge
Pumping Rate,
liters/sec
= 20%
a. Determine total flow through aerator in cubic meters
per day.
Flow, = Inflow, cu m/day + Return Flow cu m/day
cu m/day
= 15,000 cu m/day + 4,000 cu m/day
= 19,000 cu m/day
Calculate desired return sludge flow in cu m/day.
Set Sol, %
b.
Return = Total flow, cu m/day x
Sludge
F'°w. = 19,000 cu m/day x
cum/day	100o/o
100%
= 3,800 cu m/day (slightly less than actual
4,000 cu m/day)
c. Determine desired return sludge pumping rate in liters
per second.
Return = Return Flow, cum . 1.000 L . 1 day . 1 hr
Sludge	day cu m 24 hr 3,600 sec
Rate""9 = 3,800 cumxV0O0L x 1 day x 1 hr
Usee	day cu m 24 hr 3,600 sec
- 44 ifs&c
FROM SECTION 11.51 DETERMINATION OF SLUDGE AGE
1. Calculate the sludge age in days.
Known
MLSS, mg/L
Prim. Effl. SS, mg/L
Infl. Flow, cu m/day
Aerator Vol, cu m
= 2,400 mg/L
= 70 mg/L
= 15,000 cu m/day
= 2,100 cu m
Unknown
Sludge Age, days
a.	Determine the kilograms of mixed liquor suspended sol-
ids in aerator.
Solids, = mlss, mg/i. xAerVol, cu m x 	Lk9	xli0001
1,000,000 mg 1 cum
= 2,400 mg1L x 2,100 cu m x 		x 1 lQOOL
1,000,000 mg 1 cum
= 5,040 kg
b.	Determine the kilograms of solids added per day to
system by primary effluent.
1 kg
1,000 L
Solids = Row, £!i[D x P.E.SS. ™.9. x
Added by	day	L 1,000,000 mg 1 cum
kg/day = 15.°°° 70^x 1 k9 X<.000L
day L 1,000,000 mg 1 cum
= 1,050 kg/day
c. Calculate the sludge age in days.
Suspended Solids in Aerator, kg
Sludge _
Age,
days Suspended Solids in Primary Effluent, kg/day
= 5,040 kg
1,050 kg/day
= 4.8 days
2. Determine the desired kilograms of suspended solids to be
maintained in the aerator and the desired MLSS in mg/L.
Known	Unknown
Desired Sludge Age, days = 5 days	Susp. Sol. in
Solids in Prim. Effl,	= 1,050 kg/day Aerator, kg
kg/day
Aerator Vol, cu m	= 2,100 cu m Desired MLSS,
mg/i.
a.	Calculate the kilograms of suspended solids desired in
the aerator.
SS in = Sludge Age, days x SS in Prim. Effl., kg/day
Aerator,
kg =5 days x 1,050 kg/day
= 5,250 kg
b.	Calculate the desired MLSS in mg/L.
Desired _ Desired SS in Aerator, kg . 1,000,000 mg 1 cum
ui cc —		—-—-			x 	 * 	
Aerator Volume, cu m	1kg	1,000 L
mg IL
5,250 kg x 1,000,000 mg x 1 cu m
2,100 cu m	1 kg	1,000 L
= 2,500 mg/L
FROM SECTION 11.53 DETERMINATION OF WASTE
SLUDGE PUMPING RATE
1. Calculate the waste sludge pumping rate.
Known	Unknown
MLSS, mg/L	= 2985 mg/L Return Sludge Pumping
Rate, cu m/day
Return SI. SS, mg/L = 6200 mg/L
Return Sludge Pumping
Prim. Eff. SS, mg/L = 72 mg/L	Rate, LI sec
Flow, cu m/day = 15,000 cu m/day
= 200 cu m/day
= 2.31 L/sec
= 2,100 cu m
= 5 days
Current Waste SI.
Pumping Rate
Aerator Vol, cu m
Desired Sludge
Age, days
a. Determine the kilograms of mixed liquor suspended sol-
ids in the aerator.
Solids,
kg
mg
1kg
MLSS, ysx Aer Vol, cu m x
L	1,000,000 mg
1000 L
1 kg
1 cu m
1000 L
1 cu m
= 2955 29 x 2100 cum xiooooo0mg
= 6206 kg
Determine the kilograms of solids added per day to
system by primary effluent.
S/MiH. CU m mfl 1 1(0 1000 L
Solids - 		 d c e© w	
cum	ma
Added by = ' da7 * P E SS' T~
Pri. Eff.,	y	L
kg/day
1,000,000 mg 1 cu m
1 15,000-r— x 72 -
day ' L
' 1080 kg/day
1000 1.
1,000,000 mg 1 cu m
1kg

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Activated Sludge 81
Calculate the DESIRED kilograms of mixed liquor sus-
pended solids in the aerator.
Sludge
Age,
days
Suspended Solids in Aerator, kg
Suspended Solids in Primary Effluent, kg/day
Desired
SS in = Sludge Age, days x SS in P.E., kg/day
Aerator,
kg = 5 days x 1080 kg/day
= 5400 kg
d. Estimate the increase in waste return sludge pumping
rate in cubic meters per day.
Increase in Waste Return Sludge Pumping Rate, cu m/day
Additional Solids to be Wasted, kg/day
~ Return Sludge Cone., mgIL
1,000,000 mg 1 cu m
* 1 kg * 1000 L
_ (6206 kg - 5400 kg)/day' 1,000,000 mg 1 cu m
6200 mg/i.	1 kg 1000 L
= 130 cu m/day
Calculate the total waste return sludge pumping rate.
Total Return
Sludge Pumping = Current Rate, cu m/day + Inc. Rate, cu m/day
Rate, cu/m day
= 200 cu m/day + 130 cu m/day
= 330 cu m/day
e.
Total Return	1000 i. 1 day
Sludge Pumping = 330 cu m/day x	x rrr1 x ;
Rate, /./sec
= 3.8 L/sec
1 hr
cum "24 hr " 3600 sec
FROM SECTION 11.72 CALCULATION OF FOODI
MICROORGANISM AERATOR LOADING
1. Calculate the food/microorganism aerator loading as kilo-
gram COD per day per kilogram MLVSS under aeration.
Known
Prim Effl COD, mgIL = 150 mgIL
Unknown
F/M Loading Factor in
kg COD/day/kg MLVSS
Infl Flow, cu m/day = 15,000 cu m/day
Aerator Vol, cum - 2,100cu m
MLVSS, mgIL = 1,700 mgIL
a. Find kg of COD provided to aerator per day.
mg 1 Kg
Aerator	cu m
Loading, - Flow, ~— x Prim Effl COD, -.
kg COD/diy	"•*	L
1,000 L
1,000,000 mg J 1 cum
1 kg
1,000 i.
-	15.000^* 150^000 x -10000Mmfl. , eu m
-	2,250 kg COO/day
b. Calculate kg of MLVSS under aeration.
mg 1 kg
MLVSS.
kg
¦ Aar Vol, cu m x MLVSS, -
mg
¦	2,100 cu m x 1,700——
¦	3,570 kg under aeration
1,000 L
" 1,000,000mg * 1 cum
1 kg	1,0001.
1,000,000 mg 1 cu m
c. Determine the F/M loading factor in kg of COD per day
per kg of MLVSS under aeration.
_ Aerator Loading, kg COD/day
Loading ~~ MLVSS Under Aeration, kg
kg COD/	2,250 kg COD/day
day/kg =
MLVSS 3,570 kg MLVSS Under Aeration
= 0.63 kg COD/day/1 kg MLVSS
FROM SECTION 11.74 CALCULATION OF MEAN CELL
RESIDENCE TIME
1. Calculate the mean cell residence time in days.
Known	Unknown
Aerator Vol, cu m =4,200 cu m	MCRT, days
Flow to Aerator,	= 15,000 cu m/day
cu m/day
Waste Sludge Flow for	= 300 cu m/day
Past 24 Hours,
cu m/day
MLSS, mgIL	= 2,400 mgIL
Waste Sludge SS, mgIL	= 6,200 mgIL
Final Effl SS, mg/i.	= 12 mgIL
a. Calculate the kilograms of suspended solids in the aer-
ation system.
mg
Aerator « Aerator x MLSS,
SS, kg Vol, cu m	L
1,000 L
.<	
1,000,000 mg 1 cu m
1 Kg
1 kg
¦ 4,200 cu m x 2,400 5^-x
L 1,000.000 mg
> 10,080 kg
1,000 L
1 cu m
b. Determining the kilograms per day of solids wasted.
SS Wasted,
kg/day
C.
cum ... . m9 1 kg	1,000 L
>	Row, 		x Waste SS, — x »— x 		
day	L 1,000,000 mg 1 cu m
cum . mg 1 kg	1,000 L
>	300 —— x 6,200 ~r~ x , „„„ *— x —	
day	L 1,000,000 mg 1 cu m
¦ 1,860 kg SS wasted/day
Estimate the Kilograms per day of solids lost in the
effluent.
cu m 		mg	1 kg
SS Lost, - Flow, -— x Effl SS,-f— x "
kg/day day L 1,000,000 mg
cum mg 1 kg
- 15,000-	* 12 —	°
1,000 L
1 cu m
1,000 L
day L 1,000,000 mg 1 cum
*> 180 kg SS lost in effluent/day
d. Calculate the MCRT in days.
MCRT Smpwidod Solids In Aeration System, kg
days' Wasted, kg/day + SS In Effl, kg/day
10,080 kg
* 1,860 kg/day + 180 kg/day
- 4.9 days
* Biological cultures should be subject to stow changes rather than rapid ones; therefore, the kilograms wasted will be removed during a 24-hour
period.

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82 Treatment Plants
2. Calculate the waste sludge pumping rate for the next 24
hours in liters per second if the desired MCRT is 6 days.
Known
Unknown
Information from Problem 1 Waste Sludge Pumping
Desired MCRT, days = 6 days Rate, liters/sec
a. Determine the desired suspended solids wasted in
kilograms per day.
SS Under Aeration, kg
SS Wasted,
kg/day
180 kg/day
MCRT, days
- 10.080 Kg
6 days
= 1,680 kg/day - 180 kg/day
= 1,500 kg/day
SS In Effl, kg/day
b. Calculate the waste sludge pumping rate in liters per
second.
SS Wasted, kg/day 1,000,000 mg 1 day 1 hr
Wast© —	x	x _. , x
Sludge Was,e SS' m&L
Pumping
Rate,
liters/sec
=2.8 liters/sec
1,000,000 mg
kg
1500 kg/day 1,000,000 mg 1 day	
6200 mgIL kg	24 hr 3600 sec
24 hr 3600 sec
1 hr
SUGGESTED ANSWERS
Chapter 11. ACTIVATED SLUDGE
Volume II. Operation of Activated Sludge Plants
Answers to questions on page 15.
11 .OA The two major variables that affect the operation of an
activated sludge plant are (1) the dischargers to the
collection system and (2) in-plant operational vari-
ables.
11,0B Excessive storm water can upset the activated sludge
process by (1) reducing treatment time of the waste-
water, (2) increasing the amount of grit and silt, (3)
increasing the organic loading, and (4) causing fluctu-
ations in wastewater temperature and solids content.
11,0C Other variables in the collection system affecting the
activated sludge plant include the (1) wastes dis-
charged, and (2) maintenance activities.
Answers to questions on page 16.
11.0D The COD test is recommended to measure the
strength of the influent wastewater to the activated
sludge process because the results are available
within four hours and can be used to control the pro-
cess.
11.0E The aerator pH should be measured in the aerator
because the pH of the sample can change very rapidly
outside the aerator.
11.OF True.
Answers to questions on page 19.
11 .OG The two methods used to supply oxygen from air to
bacteria in the activated sludge process are (1) me-
chanical aeration, and (2) diffused aeration.
11 .OH Sludge Age, _ Suspended Solids Under Aeration, lbs
days	Suspended Solids Added, lbs/day
END OF ANSWERS TO QUESTIONS IN LESSON 1
Answers to questions on page 28.
11.1 A Aeration serves the dual purposes of providing dis-
solved oxygen and mixing of the mixed liquor and
wastewater in the aeration tanks.
11.1B Diffusers are located near the bottom of the aeration
tank to maximize the contact time of the air bubbles
with the mixed liquor. Also, this location encourages
mixing and discourages deposits on the tank bottom.
11.1C Guide vanes on centrifugal blowers are positioned
manually by operating personnel or by plant in-
strumentation by either dissolved oxygen levels in the
aeration tanks or by plant influent flows.
11.1D Fine bubble diffusers are easily clogged because
these diffusers are self-sealing from the inside if dirty
air is pumped into the diffusers. They may clog from
the outside due to biological growths.
Answers to questions on page 35.
11.2A Before attempting to maintain or repair a surface
aerator, shut down the aerator and be sure the main
power breaker is shut off, locked out and properly
tagged.
11.2B A lock-out tag must note the date of the lock out, the
reason for the lock out, and the name of the person
who locked out the aerator.

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Activated Sludge 83
11.2C The following precautions should be taken when work-
ing on blowers:
1.	Be sure all inlet and discharge valves are open
before starting;
2.	Remove all foreign matter that might enter blower;
3.	All personnel must be clear of blower before start-
ing;
4.	Always wear ear protection when working near an
operating blower;
5.	When shutting down a blower, be sure the main
power breaker is shut off, locked out and properly
tagged; and
6.	Allow only qualified and authorized electricians to
troubleshoot and repair electrical problems.
END OF ANSWERS TO QUESTIONS IN LESSON 2
Answers to questions on page 38.
11.3A The main reasons are to familiarize the operator with
plant equipment and locations of piping. Also to be
reasonably sure that everything will function properly
when the plant is put into service.
11.3B Lines and channels should be cleaned before start-up
to remove any sand, debris, or material that will oc-
cupy space or damage equipment. Cleaning also will
familiarize the operator with the flow routes.
11.3C Chips and scrapes on gates should be painted for the
protection of the equipment. The cost of equipment is
expensive, and it is part of the operator's responsibility
to obtain as long a life as possible for plant equipment.
11.3D If storm flow gates and pedestal lift gates travel down
from an overhead stem, it may be possible to drop the
gates into the tank. The main purpose of the stop-nuts
on the stems of valves is to set length of travel.
Answers to questions on page 38.
11.3E The effluent weir should be level to prevent short-
circuiting and an uneven flow of solids over the weir.
11.3F The water sprayed on a walk may create a hazard by
being slippery either from ice in the winter or algal
growths in the summer.
Answers to questions on page 39.
11.3G Air passing through porous media diffusers must be
free of dirt or it will clog the inside of the diffuser mak-
ing it necessary to remove the diffusers for cleaning.
The dirt is removed by filters.
11.3H When the difference in pressure recorded by the man-
ometers reaches approximately 2 to 3 inches (5 to 8
cm) of water column more than the initial difference, it
is probably time to clean or change the filters. See the
manufacturer's manual for recommended pressure
differences.
Answers to questions on page 40.
11.31 Most manufacturers normally supply a one-year war-
ranty on their equipment. If the equipment is mis-
treated due to improper operation, the warranty be-
comes void, and your community or district must ab-
sorb the cost. Proper operation prolongs the life of
equipment and reduces the cost of repairs and re-
placement.
11.3J Usually in the construction specifications the equip-
ment suppliers are requested to supply three or four
copies of instructions for each piece of equipment. If
they are lost, a new one may be obtained by writing to
the manufacturer and giving the name, size, serial
number, and the treatment plant location and contract
number if possible.
11.3K Proper starting, operating, and stopping procedures
must be followed when running equipment to reduce
equipment wear and failure and to insure the safety of
the operator.
11 3L The sharp edge of a metering orifice is usually on the
same side as the orifice information which is stamped
on the orifice plate handle. The sharp edge should be
placed so as to be facing the stream flow with the
bevel on the discharge side. If the orifice is installed
backwards, it will give an incorrect reading.
Answers to questions on page 40.
11.3M If the hoist is not anchored properly and a header is
being raised, the hoist could catapult into the aeration
tank and could cause injury to operators and equip-
ment.
11.3N Important safety precautions which should be ob-
served when working on a center "Y" wall include the
wearing of life preservers, having help standing by,
keeping the area clear and free of slippery materials,
providing secure footing, and requiring adequate light-
ing.
11.30 If air diffuser headers, or the pipe containing them, are
slanted so that one end of the header cross arm is
higher than the-other (by as little as Vz inch or 1.2 cm),
the air will be unevenly released into the aerator. The
diffusers on the high side at low air rates will allow
most of the air to pass out of them through the path of
least resistance rather than go through the diffusers
which are located on the low end of the header and
which have only Vz inch (1.2 cm) more water over the
top of them. This creates an undesirable flow pattern
in the tank.
Answers to questions on page 41.
11.3P Whenever a blower is first put on the line, the bearing
lubrication and temperature should be checked, along
with driven equipment load, air flow rates, and tem-
perature. The purpose of the checks is to determine if
the blower is operating properly and to prevent dam-
age to the blower.
11.30 Grease should be applied to the threads of a diffuser
to serve as a protective coating and to make it easier
to remove the diffuser for cleaning.
Answers to questions on page 42.
11,3R 1. Name of pump: 	
2.	Location of pump: 	
3.	Pump suction pressure:	
4.	Pump discharge pressure: 	
5.	Water level in wet well: 	
6.	Motor amperage: 	
7.	Pump discharge (flow): 	
8.	Date of test:			
9.	Name of operator: __—		
END OF ANSWERS TO QUESTIONS IN LESSON 3

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84 Treatment Plants
Answers to questions on page 44.
11.4A Chlorination equipment should be put in service to dis-
infect the plant effluent and to protect the health of the
receiving water users.
11.4B Return sludge rates during start-up are selected to
return the settled activated sludge in the secondary
clarifier as fast as possible and to keep the sludge
blanket in the secondary clarifier as low as possible.
11 AC Blowers should be started and air should be flowing
out the diffusers before wastewater is admitted to the
aeration tanks to prevent diffuser clogging by waste
solids. This is particularly important if porous-type dif-
fusers are used.
11.4D DO should be checked throughout the aerator. If pos-
sible, use a DO probe and determine the DO along
both sides of the aerator at both the water surface and
bottom.
Answers to questions on page 45.
11.4E To record the solids buildup in the aeration tank the
operator should collect a grab sample at the same
time every day, preferably during peak flows. The
sample of mixed liquor should be collected approxi-
mately 5 feet (1.5 m) from the effluent end of the aera-
tion tank and 1.5 to 2 feet (0.4 to 0.6 m) below the
water surface to insure a good sample.
11.4F Calculate pounds of solids under aeration.
Solids, lbs
= Mixed Liq Susp Sol, mg/Z. x Aerator Vol, MG x
8.34 lbs/gal
= 640 mg/L x 0.25 MG x 8.34 lbs/gal
= 1334 lbs
11.4G Estimate return sludge pumping rate, GPM.
Flow to aerator from primary clarifier = 2.0 MGD
Return sludge flow to aerator	= 0.5 MGD
Total flow through aerator	= 2.5 MGD
Rate^MGcf96 = Aerator F,ow' MGD x Settleable Solids, %
= 2.5 MGD x 0.17
= 0.425 MGD
Return Sludge _ 425,000 GPP
Rate, GPM 1440 min/day
= 295 GPM
END OF ANSWERS TO QUESTIONS IN LESSON 4
Answers to questions on page 54.
11.5A Some activated sludge must be wasted to prevent an
excessive solids buildup in the aerator.
11.5B The best place to waste excess activated sludge is to
divert it to the primary clarifier, sludge thickener, or
aerobic digester, but not directly to an anaerobic di-
gester.
11.5C Sludge _
Age,
days
Suspended Solids in Aerator, lbs	
Suspended Solids in Primary Effluent, lbs/day
= ^°° (°-5 (8-34 lbs/gal)
(70 mg/L) (4.0 MGD) (8.34 lbs/gal)
_ (30) (0.5)
4
= 3.75 days
END OF ANSWERS TO QUESTIONS IN LESSON 5
Answers to questions on page 57.
11 6A Plant records of the activated sludge operation are
important because they are helpful in identifying the
cause of operational problems or upsets and indicat-
ing what corrective action should be taken.
11.6B If the mixed liquor suspended solids were allowed to
build up too high, the quality of the plant effluent would
deteriorate.
Answers to questions on page 59.
11.6C The best solids loading for an aerator is determined by
experimentation and careful measurement of loading
guidelines and effluent quality.
11.6D Check the plant records to determine the cause and
then make adjustments to process. However, only one
change at a time should be made to the activated
sludge system, and one week should be allowed to
observe the response.
11.6E When digester supernatant with a high solids content
is returned to the primary clarifier, it may greatly in-
crease the suspended solids content of the primary
effluent, particularly if waste activated sludge is also
being applied to the same primary clarifier. The rem-
edy is to draw sludge from the digester to reduce the
supernatant load to the plant.
11,6F During the high flows a solids loss could occur. If pos-
sible, change the plant to step-feed aeration to retain
more mixed liquor solids in the aeration tank. If the
solids were already lost, stop wasting and attempt to
build more solids.
11.6G There could be a significant increase in air flow rates
to maintain desired DO level in the mixed liquor if the
wastewater temperature increases. The suspended
solids in the mixed liquor should be decreased if the
wastewater temperature increases. Also, bacteria are
more active at higher temperatures.
11.6H When lab data varies considerably from day to day,
check sampling times, locations, methods, and labora-
tory procedures for causes of variations.
11.61 Allow one week for a plant to stabilize after a process
change. An experienced operator who knows the plant
may be able to determine if the proper changes have
been made after several days, but some plants require
up to two weeks to stabilize after a change.

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Activated Sludge 85
Answers to questions on page 61.
11 6J Froth or foam may be controlled by:
1.	Maintaining higher mixed liquor suspended solids
concentrations;
2.	Reducing air supply during periods of low flow
while still maintaining 00; and
3.	Returning supernatant to the aeration tank during
low flows.
11.6K Grease deposits can be removed from walks by using
trisodium phosphate and a stiff bristle deck brush and
hose.
11-6L Bulking sludge will be indicated by large mats of float-
ing sludge or a tremendous amount of suspended sol-
ids being carried out of the final clarifier in the effluent.
Rising sludge will be light flocculent particles of floe
collecting mainly on the surface of the final tanks and
forming a thin surface scum. Rising sludge is accom-
panied by high DO in the aerator effluent and final
clarifier.
11.6M Several adjustments may be attempted to correct a
rising sludge problem, but only one should be under-
taken at a time.
1.	Increase return sludge rates, but control final
clarifier sludge level.
2.	Increase load to aerator by removing a primary
clarifier from service if more than one is being
used.
3.	Admit raw wastewater directly to the aerator during
low flows.
4.	Check the possibility of going to a tapered aeration
diffuser placement.
END OF ANSWERS TO QUESTIONS IN LESSON 6
Answers to questions on page 63.
11.7A New microorganisms are continually being repro-
duced, and some of them must be removed from the
system to control their population in order to balance
the food supply.
11 7B Solids Wasted, lbs
= Solids in System, lbs - Desired Solids, lbs
= 12,000 lbs - 9,000 lbs
= 3000 lbs
11 7C Waste Sludge Rate, MGD
_	Solids to be Wasted, lbs/day
Return Sludge Cone., mgIL x 8.34 lbs/gal
3000 lbs/day
6000 mgIL x 8.34 lbs/gal
_ 3000/day x —1	 (Remember, one liter = 1 M mg)
6000 8.34/MG
= 3000/day nr 3000/day
50,040/MG 50,000/MG
= 0.06 MGD
Waste Sludge Rate, GPM
= 0 06 MGD
1440 min/day
= 60'OOP 9als
1440 mins
= 41.8 GPM Waste at 40 GPM.
11.7D Waste = Susp Sol in System, lbs gusp Sol in
Sludge,	MCRT, days ~ Effl, lbs/day
lbs/day
= 40,000 !bs ,1Q mg/L x 5 0 MQD x 8 34 (bs/ga|
10 days
= 4000 lbs/day - 417 lbs/day
= 3583 lbs/day
Answers to questions on page 64.
11.8A Both surface aerators and blowers must be shut down
before any maintenance is performed to prevent injury
to maintenance personnel and possible damage to
equipment.
11.8B To shut down an aerator:
1.	Turn the "on-off-auto" switch to "off";
2.	Turn the main power breaker to "off"; and
3.	Lock-out and tag the main power breaker in the
"off" position.
11,8C The regulating/isolation valve(s) or the blower must be
locked out and tagged before servicing the air distribu-
tion system to prevent air from entering the system.
11.8D The air distribution system must be shut down before
attempting to repair even the smallest leak because
serious bodily injury may result from escaping air or
foreign material.
Answers to questions on page 66.
11.8E The motor on a surface aerator could draw a high or
uneven amperage due to:
1.	Moisture;
2.	Winding breakdown;
3.	Excessive impeller submergence; and
4.	Excessive motor bearing or gear reducer friction.
11.8F If filters do not have a manometer, you can determine
if filters need cleaning by removing them and observ-
ing the degree of dirt and dust buildup.
11.8G Fine-bubble diffusers can become clogged due to dirt
and biological growths.
Answers to questions on page 71.
11.8H Motor windings deteriorate due to heat and moisture.
11.81 Air filters are cleaned by using a relatively high pres-
sure clean water or by steam cleaning.
11 8J Equipment may "seize up" and become inoperable
when the equipment overheats and a component ex-
pands so the equipment will not work. This is also
called "freezing."
1b QU&liDWb

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86 Treatment Plants
OBJECTIVE TEST
Chapter 11. ACTIVATED SLUDGE
Please write your name and mark the correct answers on the
answer sheet as directed at the end of Chapter 1. There may
be more than one correct answer to each question.
1.	Operators in activated sludge plants must control the aera-
tion rates in the aeration tanks.
*1. True
2. False
2.	Aeration tank suspended solids are an important test for
controlling the activated sludge process.
1.	True
2.	False
3.	Orifice plates are used to measure air flow rates.
.1. True
2. False
4.	Air header diffusers should be threaded into place using a
torque wrench.
1. True
'¦>'2. False
5.	A volute is a type of bacteria.
1. True
/2. False
6.	Aerobes need DO.
1.	True
2.	False
7.	All suspended solids are volatile.
1.	True
^2. False
8.	Rising sludge is a problem that occurs in secondary
clarifiers.
J1. True
2.	False
9.	Septic sludge produces a recognizable foul odor.
, 1. True
2. False
10.	Storm water infiltration usually improves plant efficiency.
1.	True
2.	False
11.	The oxygen transfer efficiency of a surface aerator in-
creases as the submergence of the aerator is decreased.
1.	True
2.	False
12.	The "best" sludge age for an activated sludge plant wast-
ing sludge to the primary clarifier should be the same as
the sludge age for a plant wasting to a gravity thickener.
1.	True
2.	False
13.	The activated sludge process
^.	Is a biological process.
2.	Is an anaerobic process.
3.	Requires activated carbon.
M.	Requires aeration.
¦;5. Usually follows primary sedimentation.
14.	Before starting a new plant, the operator should check the
1.	Aeration equipment.
2.	Aerator control gates.
3.	Blower system.
4.	Effluent weirs for level.
5.	Painted gates for chips and scrapes.
15.	When operating an activated sludge plant, which is the
MOST IMPORTANT SUSPENDED SOLIDS TEST FOR
OPERATIONAL CONTROL?
1.	Aerator mixed liquor
2.	Final clarifier effluent
3.	Plant influent
4.	Primary effluent
5.	Return sludge
16. Which of the following are considered the main opera-
tional PROCESS CONTROLS available to an operator?
1.	Air rates
2.	BOD test
3.	Maintenance
4.	Pounds of solids under aeration
5.	Return sludge rate
17. Why is the COD test a better operational control test than
the BOD test?
1.	Everyone uses it.
2.	It isn't better.
3.	The oxygen demand is not caused by biological or-
ganisms.
4.	The results are available sooner.
5.	This chapter says so.
18. The effectiveness of the organisms in the aerator depends
on the
1.	Characteristics of food supply.
2.	pH.
3.	Presence of inhibiting substances.
4.	Temperature.
5.	Time of reaction or time available for the reaction.
19. The hoist used to lift the air headers in the aeration tank
must be properly anchored or it
1.	Could fall into the aerator.
2.	Could hurt someone.
3.	Could not lift the aerator.
4.	Will float away.
5.	Won't allow even distribution of the air.

-------
Activated Sludge 87
20.	Blowers may be of which of the following types?
1.	Centrifugal
2.	Positive displacement
3.	Progressive cavity
4.	Rotary
5.	Turbine
21.	Why should all of the diffusers in an aeration tank be
cleaned at once?
1.	So the air will flow evenly from all the diffusers
2.	So the plant won't use too much air
3.	To get the job done in a hurry
4.	To improve tapered aeration
5.	To improve the step-feed aeration
22.	When the return sludge rate is too low, what happens?
1.	The activated sludge in the aerator will starve.
2.	The activated sludge in the secondary clarifier could
become septic.
3.	The sludge blanket in the secondary clarifier could be-
come too high.
4.	The tank will not fill.
5.	There will be insufficient organisms to treat the waste
load entering the aerator.
23.	What items would you check if an activated sludge plant
becomes upset?
1.	COD loadings
2.	Chiorinator
3.	Daily flow rates
4.	Digester operation
5.	Influent temperature
24.	How long would you allow an activated sludge process to
react and stabilize after a change?
1.	3 hours
2.	12 hours
3.	1 day
4.	2 days
5.	1 week
25.	Causes of sludge bulking include
1.	Aeration period too short.
2.	Air supply too low.
3.	Bulk of sludge too large.
4.	Loading rate too high.
5.	Sludge going septic in secondary clarifier.
26.	How many pounds of solids are in a 400,000-gallon aera-
tion tank if the suspended solids concentration is 1200
mg/L?
1.	3000	^
2.	4000
3.	4400
4.	4800
5.	5200
27.	What should be the waste sludge pumping rate if a plant
should be wasting 2000 pounds per day and the concen-
tration of return sludge is 5000 mg/L? Select the closest
answer.
1.	25gpm
2.	33gpm
3.	35 gpm
4.	36 gpm
5.	40 gpm
28. What is the food/microorganism loading ratio in an acti-
vated sludge plant with a flow of 1 MGD? The average
BOD to the aerator is 140 mg/L, the aeration tank contains
250,000 gallons, and the mixed liquor suspended solids
concentration is 2000 mg/L. Select the closest answer.
1.	25 lbs BOD per day/100 lbs MLSS
2.	28 lbs BOD per day/100 lbs MLSS
3.	30 lbs BOD per day/100 lbs MLSS
4.	32 lbs BOD per day/100 lbs MLSS
5.	35 lbs BOD per day/100 lbs MLSS
29. Mixed liquor suspended solids which need to be wasted
accumulate from what sources?
1.	Death of filamentous organisms
2.	Dissolved solids in the plant influent
3.	New cell production by the microorganisms
4.	Scum pumped from the scum box
5.	Suspended solids from the primary clarifier
30. Inspection of an aeration tank produces the following ob-
servations:
Violent turbulence throughout the aeration tank,
Large air bubbles reaching the surface, and
Dissolved oxygen level is 7 mg/L.
This aeration tank is being
1.	Hydraulically overloaded.
2.	Organically overloaded.
3.	Over aerated.
4.	Over fed with organisms.
5.	Under aerated.
31. A review of operating data from an activated sludge plant
reveals the following information:
Air rates are high,
Dissolved oxygen level in aeration tank is low,
Low turbulence is observed throughout the aeration
tank,
Organic load is normal, and
Hydraulic load is normal.
What could be the cause of the low dissolved oxygen in
the aeration tank?
1.	Blower speed too high
2.	Excessive shearing of air bubbles by diffusers
3.	Leaks in the aeration system piping
4.	Return sludge rate too high
5.	Waste activated sludge rate too high
32. Observations and lab tests of a secondary clarifier in an
activated sludge process reveal the following data:
Clumps of sludge rising to the clarifier surface,
Bubbles visible on the tank surface,
Mixed liquor solids settling normally in settleability
test, and
Mixed liquor solids rising after settling in settleability
test.
What could be the cause of the clumps of sludge rising to
the clarifier surface?
1.	Denitrification is occurring in the clarifier.
2.	Dissolved oxygen level is too high.
3.	Return activated sludge pumping rate is too high.
4.	Waste activated sludge pumping rate is too high.
5.	Wastewater temperature is too low.

-------
88 Treatment Plants
REVIEW QUESTIONS
A trickling filter 120 feet in diameter treats a flow of 4.0 MGD
with an applied BOD of 90 mg/L. The filter is 4 feet deep.
34. What is the organic (BOD) loading on the filter?
1.	0.07 lbs BOD/day/1000 cu ft
2.	0.7 lbs BOD/day/1000 cu ft
3.	6.6 lbs BOD/day/1000 cu ft
4.	66 lbs BOD/day/1000 cu ft
5.	264 lbs BOD/day/1000 cu ft
33. What is the hydraulic loading on the filter?
1.	30 gpd/sq ft
2.	35 gpd/sq ft
3.	300 gpd/sq ft
4.	350 gpd/sq ft
5.	1400 gpd/sq ft
END OF OBJECTIVE TEST

-------
CLE AN WATER, U.S.A.
WATER POLLUTION CONTROL PLANT
MnuTHiv BFrnnn iq hpfrator •
DATE
DAY
WEATHER
FLOW - MGD
RAW WASTEWATER
PRIM. EFF.
FINAL EFFLUENT
AERATION SYSTEM
SUMMARY DATA
a:
z
UJ
h-
X
a.
SETT. SOLIDS
B. 0. D.
SUSP SOLIDS
B. 0. D.
SUSP SOLIDS
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SUSP SOLIDS
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% VOL.
30 MIN. SETT.
S.V. 1.
D.O.
RETURN
SUSP SOLIDS
RETURN-M6D
WASTE
GAL. X I000
WASTE
LBS./DAY
% REMOVAL
B.O. D.
S. S.
INF-PRI
39.7
49.6
INF-EFF
93.5
92.8
SLUDGE DATA
1
s
CLIM
1.782
75
7.2
14


118
84
o.e
6.9
(9
18
0.1
2.7
67*6
2036
7§.9
150
73
2.5
5961
0.702
70
3480
% SOLIDS - AVG.
5.6
2
M
ClCML
2.347
74
7.3
13
218
I50
156
84
0.3
£.8
19
15
1.0
2.8
6851
2078
786
150
72
1.4
4683
0.711
72
2812
LBS. DRY SOLIDS/ DAY
5 579
3
T
CLM
2.165
74
7.3
a


I0S
66
0.8
6.8
14
9
1.2
8.8
7224
2211
77.fi
170
76
2.1
6625
a708
71
3922
4
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2.012
74
7.5
12


135
74
0.5
6.8
16
14
0.8
4.4
73 OS
2213
78,6
180
81
2.0
6641
0.712
70
3877
% VOL. SOLIDS — AVG.
79.6
5
T
CLEM
2.483
74
7.2
13
181
138
134
62
0.3
6.8
9
II
1.7
5.2
7014
2106
79.3
170
80
2.6
6098
0.722
78
396G
LBS. VOL. SOLIDS / DAY
4452
6
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74
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0.4
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6
2.6
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79.0
160
77
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5862
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3911
7
S
CLCM
2.131
75
7.3
13


89
66
0.7
6.1
14
7
1.2
4.4
6296
1905
78.7
150
78
2.6
5564
0.70t
80
3712
LBS. VOL S0L./1000 FT^DAY
£7.5
8
S
CUBM
I.8C7
76
7.4
12
174
134
84
74
0.9
6.1
9
15
0.8
4.2
7057
2138
786
180
84
0.9
6758
0.703
72
4058
GALS. SLUDGE TO BEDS
28,000
9
M
CLEM
2.634
71
7.3
14


117
68
0.3
6.S
II
II
I.G
3.5
6767
2037
79.1
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78
2.5
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0.712
70
3515
'9
T
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2307
76
7.3
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120
ce
0.3
1.1
8
8
1.5
6.6
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1861
78.3
170
91
2.8
6135
Q705
64
327+
CU. YDS. CAKE REMOVED
63
it
W
CLEM
2.IW
7C
7.3
16
112
I42
III
6S
0.4
7.0
9
10
I.I
6.6
7035
2123
7&1
ZOO
94
1.7
£183
Q700
70
3609
FT3 GAS /LB. VOL. SOLIDS
G.8
12
T
CUM
2202
76
7.3
II



72
0.4
7.0
11
9
2.0
3.8
6352
115+
77.4
190
97
3.0
6027
0.7(94
70
3518
13
F
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2 J 78
77
7.3
II


81
58
0.6
7.0
15
18
3.5
4.0
6313
1937
77.C
170
87
4.8
5542
0.681
72
3327
FT3 GAS/ LB. MG FLOW
14,286
14
S
CUM
IM
78
7.3
12
155
I5G
105
76
0.3
6.9
12
8
3.1
3.8
6335
1929
78.2
160
82
4-3
4856
0703
70
2834


15
s
CLCM
1.942
76
7.2
12


113
74
0.4
6.1
q
9
1.3
4.4
6873
2010
78.3
180
86
2.2
5753
&7II
73
3502
r.nsT DATA
16
M
CLEAR
2.+M
78
7.2
II


128
74
0.3
6.1
10
10
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.3.0
7082
2162
78.0
200
92
25
6852
0.723
76
+3f*


17
T
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im
76
7.1
&
IG8
I44
no
64
0.4
6.8
10
It
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6.6
6215
1937
764
190
98
22
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74
4106
MAN DAYS 63 PAYROLL
2,325.78
18
W
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78
7.3
15


105
£4
0-2
6.1
II
7
22
4.4
6227
i923
77.1
190
98
3.3
5767
0.717
83
3992
POWER PURCHASED
520.32
19
T
CwEM
2.457
78
7.3
12


87
72
0.5
6.1
in
7
2.9
6.2
4844
153+
75.2
170
110
4.5
4762
0.721
25
992
20
F
CLEAR
2.418
79
7.3
II
I93
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105
66
0.7
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18
12
3.1
4.4
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1822
76.4
190
104
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0
0
OTHER UTILITIES (GAS.H20)
NONE
21
s
CLEM
f.213
7G
7.1
12


109
76
0.6
7.1
10
9
1.2
4.2
6812
2096
78.3
200
95
2.6
5128
0.7oe
35
1730
GASOLINE. OIL. GREASE
108.56
??
s
CLEM
l.fflB
76
7.3
12


131
7ft
0.4
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10
0.5
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7518
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791
260
114
1.8
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35
1136
23
M
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2.101
77
7.3
12
I87
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133
89
0.2
G.I
13
13
0.3
2.5
8386
2541
78.6
310
121
1.9
8396
0.741
70
4901
CHEMICALS AND SUPPLIES
5+7.25
24
T
&£*
2.3M
78
7.3
13


114
56
&3
6.9
14
10
2.2
4.2
7162
2409
787
230
95
3.6
8824
0.700
VI
5225
MAINTENANCE
238.46
25
W
CLEM
2+21
76
7.3
13


89
56
0.4
7.0
12
8
2.8
4X>
7688
2332
78.5
230
98
4.1
738Z
0.713
72
4432
26
T
CLIM
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7"}
7.3
12
2I2
170
143
87
0.6
7.0
10
6
1.7
4.3
6697
2047
77.9
210
102
2.6
6867
0.618
70
4008
VEHICLE COSTS
NOME
71
F
CLEM
2.428
71
7.3
10


128
84
0.5

15
10
0.5
3.6
6923
ZI03
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200
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1.2
7436
0.702
64
3961
OTHER
NONE
29
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66
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16
5
0.6
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2180

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91
1.7
8412
0.706
68
4770
29
s
CLEM
1.862
79
7.3
7
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117
60
0.5
6.9
14
8
0.5
3.9
7852
2397
780
230
95
1.0
7117
0.7D0
66
3917
TOTAL
$ 3,740.39
30
M
CLEM
2.74C
79
7.3
13


107
73
0.2
6.8
8
6
1.6
3.5
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2335
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220
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70
4515


31


























MAX

ISO)
79
7.4
18
2.I8
no
156
e?
0.9
7.1
19
16
3-5
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6388
25+1
79.1
310
121
4.8
882+
0.74-I
83
5225
OPER. COST/MG TREATED
* 54.C2
MIN

1.782
74
7.1
7
I55
102
84
5G
0.2
6.8
8
5
0.5
2.5
4S44
1534
76.4
ISO
72
0.1
4683
0.648
0
0
OPER. COST/CAPITA/MO.
5 0.158
AVG

2283
77
7.3
12
ISC
131
112
70

6.9
12
10
1.6
4.4
6868
2012
78.1
192
91
2.6
6328
0.70t
65
3511
FLOW
LAST
1st
T0TA
METER:
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ELECT
LAST
1st
RIC ME'
7836
rER:
RAW
LA
ST
SLUDGE:

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-------
Chapter 12
SLUDGE DIGESTION AND SOLIDS HANDLING
by
John Brady
(With a special section by William Garber)
Revised
by
James F. Stahl

-------
92 Treatment Plants
TABLE OF CONTENTS
Chapter 12. Sludge Digestion and Solids Handling
Page
OBJECTIVES	 95
GLOSSARY 	 96
LESSON 1
12.0	Need for Sludge Digestion	 98
12.00	Purpose of Sludge Digestion	 98
12.01	How Anaerobic Sludge Digestion Works	 98
12.1	Components in the Anaerobic Sludge Digestion Process	102
12.10	Pipelines and Valves	102
12.11	The Anaerobic Difester	102
12.110	Fixed-Cover Tanks 	103
12.111	Floating Cover	103
12.112	Digester Depth	103
12.113	Raw Sludge Inlet	103
12.114	Supernatant Tubes	103
12.115	Sludge Draw-off Lines 	103
LESSON 2
12.12	Gas System 	107
12.120	Gas Dome	107
12.121	Pressure Relief and Vacuum Relief Valves	109
12.122	Flame Arresters	109
12.123	Thermal Valves 	109
12.124	Sediment Traps	117
12.125	Drip Traps — Condensate Traps	117
12.126	Gas Meters	117
12.127	Manometers	117
12.128	Pressure Regulators	117
12.129	Waste Gas Burner	117
12.13	Sampling Well (Thief Hole) 	117
12.14	Digester Heating 	117

-------
Sludge Digestion 93
12.15	Digester Mixing	129
12.150	Gas Mixing	129
12.151	Mechanical Mixing	129
12.16	Floating-Cover Digesters	132
12.160	Purpose of Floating Covers	132
12.161	Types of Floating Covers	132
12.162	Parts of Floating Covers		 132
12.163	Safety	134
LESSON 3
12.2	Operation of Anaerobic Digesters	135
12.20	Raw Sludge, Scum, Waste Activated Sludge	135
12.21	Starting a Digester	136
12.22	Feeding 	137
12.23	Neutralizing a Sour Digester	138
12.24	Enzymes 	139
12.25	Foaming	139
12.26	Gas Production	139
12.27	Supernatant and Solids 	139
12.28	Rate of Sludge Withdrawal 	141
LESSON 4
12.3	Anaerobic Digestion Controls and Test Interpretation 	142
A.	Temperature 	142
B.	Volatile Acid/Alkalinity Relationship	142
C.	Digester Gas	142
D.	pH 	142
E.	Solids Test	142
F.	Volume of Sludge	143
G.	Raw Sludge	143
H.	Recirculated Studge	143
I.	Secondary Digested Sludge	144
J. Digester Supernatant	145
K. Computing Digester Loadings	145
L. Computing Gas Production	145
M. Solids Balance 	146

-------
94 Treatment Plants
LESSON 5
12.4	Operational Strategy	148
12.40	Operation and Maintenance Checklist	148
12.41	Sampling and Data Checklist 	150
12.42	Normal Operation	153
12.43	Troubleshooting	153
12.44	Actual Digester Operation 	155
12.5	Digester Cleaning 	155
12.50	Need for Digester Cleaning	155
12.51	Pre-Cleaning Decisions 	157
12.52	Cleaning Methods and Necessary Equipment	157
12.53	Safety	157
LESSON 6
12.6	Aerobic Sludge Digestion	159
12.60	Comparison between Anaerobic and Aerobic Digestion 	159
12.61	Process Description	160
12.62	Operation	160
12.63	Operational Records	161
12.64	Operational Problems	161
12.640	Scum 	161
12.641	Odors	161
12.642	Floating Sludge 	161
12.65	Maintenance Problems	161
12.650	Diffuser Maintenance 	161
12.651	Aeration Equipment	161
12.7	Digested Sludge Handling	161
12.70	Sludge Drying Beds	161
12.71	Blacktop Drying Beds	164
12.72	Sludge Lagoons	164
12.73	Withdrawal to Land	164
12.74	Mechanical Dewatering	164
12.740	Vacuum Filters	166
12.741	Centrifuge	166
12.8	Review of Plans and Specifications	169
12.9	Additional Reading	169
12.10	Metric Calculations 	170
12.100	Conversion Factors	170
12.101	Problem Solutions	170

-------
OBJECTIVES
Chapter 12. SLUDGE DIGESTION AND SOLIDS
HANDLING
Following completion of Chapter 12, you should be able to
do the following:
1. Explain how a sludge digester works and what factors
influence and control the digestion process,
2 Inspect new sludge digesters and solids handling facilities
for proper installation,
3.	Place a new sludge digester into operation,
4.	Schedule and conduct operation and maintenance duties,
5.	Collect samples, interpret lab results, and make appropri-
ate adjustments in the sludge digestion and solids han-
dling processes,
6.	Recognize factors that indicate the sludge digestion and
solids handling processes are not performing properly,
identify the source of the problem, and take corrective
action,
7.	Discuss the various methods of solids handling and know
how to operate and maintain these processes,
8.	Determine loadings on sludge digesters and solids han-
dling facilities,
9.	Conduct your duties in a safe fashion,
10.	Keep records for the sludge digestion and solids disposal
processes,
11.	Develop an operational strategy for a sludge digester, and
12.	Review plans and specifications for a sludge digester.

-------
96 Treatment Plants
GLOSSARY
Chapter 12. SLUDGE DIGESTION AND SOLIDS HANDLING
AEROBIC DIGESTION (AIR-O-bick)	AEROBIC DIGESTION
The breaking down of wastes by microorganisms in the presence of dissolved oxygen. Waste sludge is placed in a large aerated
tank where aerobic microorganisms decompose the organic matter in the sludge. This is an extension of the activated sludge
process.
ALKALINITY (AL-ka-LIN-ity)	ALKALINITY
The capacity of water or wastewater to neutralize acids. This capacity is caused by the water's content of carbonate, bicarbonate,
hydroxide, and occasionally borate, silicate and phosphate. Alkalinity is expressed in milligrams per liter of equivalent calcium
carbonate. Alkalinity is not the same as pH because water does not have to be strongly basic (high pH) to have a high alkalinity.
Alkalinity is a measure of how much acid can be added to a liquid without causing a great change in pH.
ANAEROBIC DIGESTION (AN-air-O-bick)	ANAEROBIC DIGESTION
Wastewater solids and water (about 5% solids, 95% water) are placed in a large tank where bacteria decompose the solids in the
absence of dissolved oxygen. At least two general groups of bacteria act in balance: (1) SAPROPHYTIC BACTERIA break down the
complex solids to volatile acids; and (2) METHANE FERMENTERS break down the acids to methane, carbon dioxide, and water.
BTU (BEE-TEA-YOU)	BTU
British Thermal Unit. The amount of heat required to raise the temperature of one pound of water one degree Fahrenheit.
BIODEGRADATION (BUY-o-de-grah-DAY-shun)	BIODEGRADATION
The breakdown of organic matter by bacteria to more stable forms which will not create a nuisance or give off foul odors.
BUFFER	BUFFER
A solution or liquid whose chemical makeup neutralizes acids or bases without a great change in pH.
BUFFER CAPACITY	BUFFER CAPACITY
A measure of the capacity of a solution or liquid to neutralize acids or bases. This is a measure of the capacity of water or
wastewater for offering a resistance to changes in pH.
CENTRATE	CENTRATE
The water leaving a centrifuge after most of the solids have been removed.
CONING (CONE-ing)	CONING
Development of a cone-shaped flow of liquid, like a whirlpool, through sludge. This can occur in a sludge hopper during sludge
withdrawal when the sludge becomes too thick. Part of the sludge remains in place while liquid rather than sludge flows out of the
hopper. Also called "coring."
DECOMPOSITION, DECAY	DECOMPOSITION, DECAY
Processes that convert unstable materials into more stable forms by chemical or biological action. Waste treatment encourages
decay in a controlled situation so the material may be disposed of in a stable form. When organic matter decays under anaerobic
conditions (putrefaction), undesirable odors are produced. The aerobic processes in common use for wastewater treatment produce
much less objectionable odors.
DEWATERABLE	DEWATERABLE
This is a property of a sludge related to the ability to separate the liquid portion from the solid, with or without chemical conditioning.
A material is considered dewaterable if water will readily drain from it.
ELUTRIATION (e-LOO-tree-A-shun)	ELUTRIATION
The washing of digested sludge in plant effluent. The objective is to remove (wash out) fine particulates and/or the alkalinity in
sludge. This process reduces the demand for conditioning chemicals and improves settling or filtering characteristics of the solids.

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Sludge Digestion 97
ENDOGENOUS (en-DODGE-en-us)	ENDOGENOUS
A reduced level of respiration (breathing) in which organisms break down compounds within their own cells to produce the oxygen
they need.
ENZYMES (EN-zimes)	ENZYMES
Enzymes are organic substances produced by living organisms and speed up chemical changes.
HYDROLYSIS (hi-DROL-e-sis)	HYDROLYSIS
The addition of water to the molecule to break down complex substances into simpler ones.
INOCULATE (in-NOCK-you-LATE)	INOCULATE
To introduce a seed culture into a system.
JOULE Qewel)	JOULE
A measure of energy, work or quantity of heat. One joule is the work done when the point of application of a force of one newton is
displaced a distance of one meter in the direction of the force.
LIQUEFACTION (LICK-we-FACK-shun)	LIQUEFACTION
The conversion of large solid particles of sludge into very fine particles which either dissolve or remain suspended in wastewater.
MESOPHILIC BACTERIA (mess-O-FILL-lick)	MESOPHILIC BACTERIA
Medium temperature bacteria. A group of bacteria that grow and thrive in a moderate temperature range between 68°F (20°C) and
113°F (45°C). The optimum temperature range for these bacteria in anaerobic digestion is 85°F (30°C) to 100°F (38°C).
PSYCHROPHILIC BACTERIA (sy-kro-FILL-lick)	PSYCHROPHILIC BACTERIA
Cold temperature bacteria. A group of bacteria that grow and thrive in temperatures below 68°F (20°C).
SAPROPHYTIC ORGANISMS (SAP-pro-FIT-tik)	SAPROPHYTIC ORGANISMS
Organisms living on dead or decaying organic matter. They help natural decomposition of the organic solids in wastewater.
SEED SLUDGE	SEED SLUDGE
In wastewater treatment, seed, seed culture or seed sludge refers to a mass of sludge which contains very concentrated populations
of microorganisms. When a seed sludge is mixed with the wastewater or sludge being treated, the process of biological decomposi-
tion takes place more rapidly.
STASIS (STAY-sis)	STASIS
Stagnation or inactivity of the life processes within organisms.
STUCK	STUCK
Not working. A stuck digester does not decompose organic matter properly. The digester is characterized by low gas production,
high volatile acid/alkalinity relationship, and poor liquid-solids separation. A digester in a stuck condition is sometimes called a
"sour" or "upset" digester.
SUPERNATANT (sue-per-NAY-tent)	SUPERNATANT
Liquid removed from settled sludge. Supernatant commonly refers to the liquid between the sludge on the bottom and the scum on
the surface of an anaerobic digester. This liquid is usually returned to the influent wet well or to the primary clarifier.
THERMOPHILIC BACTERIA (thermo-FILL-lick)	THERMOPHILIC BACTERIA
Hot temperature bacteria. A group of bacteria that grow and thrive in temperatures above 113°F (45°C). The optimum temperature
range for these bacteria in anaerobic digestion is 120°F (49°C) to 135°F (57°C).
UPSET	UPSET
An upset digester does not decompose organic matter properly. The digester is characterized by low gas production, high volatile
acid/alkalinity relationship, and poor liquid-solids separation. A digester in an upset condition is sometimes called a "sour" or "stuck"
digester.

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98 Treatment Plants
CHAPTER 12. SLUDGE DIGESTION AND SOLIDS HANDLING
(Lesson 1 of 6 Lessons)
12.0 NEED FOR SLUDGE DIGESTION
In primary treatment the settled sludge solids that are re-
moved from the bottom and the floating scum removed from
the top of the clarifiers or sedimentation tanks are a watery,
odorous mixture called raw sludge and scum. The raw sludge
and sludges from secondary trickling filter and activated sludge
processes are most commonly pumped to a SLUDGE DI-
GESTER for treatment. The sludge digester can either be an
anaerobic or aerobic treatment system. In either treatment sys-
tem, bacteria decompose the sludges to simpler forms prior to
ultimate disposal. This chapter discusses the operation of both
anaerobic and aerobic sludge digesters.
The basics of operation of an anaerobic digester are dis-
cussed in Sections 12.1 through 12.5. Aerobic digesters are
discussed in Section 12.6.
Figure 12.1 shows the location of either digestion system in
a typical plant. Figures 5.2, 6.2 and 8.4 in previous chapters
also show plan views of the location of sludge digestion and
solids handling facilities in relation to other treatment pro-
cesses.
12.00 Purpose of Anaerobic Sludge Digestion
ANAEROBIC DIGESTION1 reduces wastewater solids from
a sticky, smelly mixture to a mixture that is relatively odor free,
DEWATERABLE2 and capable of being disposed of without
causing a nuisance. In this process organic solids in the sludge
are liquefied, the solids volume is reduced, and valuable
methane gas is produced in the digester by the action of two
different groups of bacteria living together in the same envi-
ronment. One group consists of SAPROPHYTIC OR-
GANISMS3, commonly referred to as "acid formers." The sec-
ond group, which uses the acid produced by the saprophytes,
are the "methane fermenters." The methane fermenters are
not as abundant in raw wastewater, as are the acid formers.
The methane fermenters desire a pH range of 6.6 to 7.6 and
will reproduce only in that range.
The object of good digester operation is to maintain suitable
conditions in the digester for a growing (reproducing) popula-
tion of both acid formers and methane fermenters. You must
do this by controlling the loading rate or FOOD SUPPLY (or-
ganic solids), VOLATILE ACIDlALKALlNITY RELATIONSHIP,
MIXING, and TEMPERATURE. Generally, you have done your
job properly if the digester reduces the volatile (organic) solids
content by between 50 and 60 percent of what they were in the
raw sludge.
To obtain the desired degree of organic solids reduction may
require from 5 to 120 days of digestion time. The time required
depends on how good a job you are required to do on digesting
the sludge, and on the adequacy of mixing, the organic loading
rate, and the temperature at which the bacterial culture is main-
tained.
12.01 How Anaerobic Sludge Digestion Works
(by William Garber)
The equations shown in Fig. 12.2 illustrate one way of outlin-
ing what happens in a digester. These equations indicate two
general types of reactions:
1.	Acid forming reactions which proceed at a rate dependent
upon temperature, pH, and food conditions.
2.	Methane fermentation reactions which proceed at a rate
dependent upon temperature, pH, and food conditions.
You must try to operate an anaerobic sludge digester so that
the rate of acid formation and methane formation are approxi-
mately equal; otherwise the reaction will get out of balance.
The most common condition of imbalance is excess acid fer-
mentation. This occurs when the methane fermenters fail to
keep pace with the acid formers. As the rate at which methane
fermenters convert acids slows down, the digester becomes
more and more acid and the level of imbalance rises. Efficient
operation depends on keeping both types of organisms in
proper balance. The literature has been full of terms such as
"Standard-Rate" and "High-Rate" digestion. These terms refer
to digester loading and not to the rates of bacterial action. In
"High-Rate" systems, mixing is used to obtain the best possi-
ble distribution of the substrate (food) and seed (organisms) so
that more bacterial reaction can occur.
Mixing is the most important factor in the so-called "High-
Rate" processes, and it is considered to accomplish the follow-
ing:
1.	Utilize as much of the total content of a digester as possible.
2.	Quickly distribute the raw sludge food throughout the vol-
ume of sludge in the tank.
3.	Put the microorganisms in contact with the food.
4.	Dilute the inhibitory by-products of microbiological reactions
throughout the sludge mass.
1	Anaerobic Digestion (AN-air-O-bick). Wastewater solids and water (about 5% solids, 95% water) are placed in a large tank where bacteria
decompose the solids in the absence of dissolved oxygen. At least two general groups of bacteria act in balance: SAPROPHYTIC BACTERIA
(see Footnote 3) and METHANE FERMENTERS break down the acids to methane, carbon dioxide, and water.
2	Dewaterable. This is a property of a sludge related to the ability to separate the liquid portion from the solid, with or without chemical
conditioning. A material is considered dewaterable if water will readily drain from it.
3	Saprophytic Organisms (SAP-pro-FIT-tik). Organisms or bacteria living on dead or decaying organic matter. They help natural decomposi-
tion of the organic solids in wastewater.

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Sludge Digestion 99
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Fig. 12.1 Flow diagram of typical plant

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RAW 
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Sludge Digestion 101
5.	Achieve good pH control by distributing BUFFERING4 AL-
KALINITY5 throughout the digestion tank.
6.	Obtain the best possible distribution of heat through the
tank.
7.	Minimize the separation of grit and inert solids to the bottom
or floating scum material to the top.
An anaerobic digester may be operated in one of three tem-
perature zones or ranges, each of which has its own particular
type of bacteria. The lowest range (in an unheated digester)
utilizes PSYCHROPHILIC (cold temperature loving) BAC-
TERIA6. Temperture of the sludge inside tends to adjust to the
outside temperature.
However, below 50°F (10°C) little or no bacterial activity oc-
curs and the necessary reduction in sludge vo/at/les (organic
matter) will not occur. When the temperature increases above
SOT (10°C), bacterial activity increases to a measureable rate
and digestion starts again. The bacteria appear to be able to
survive temperatures well below freezing with little or no harm.
The psychrophilic upper range is around 68°F (20°C). Diges-
tion in this range requires from 50 to 180 days, depending
upon the degree of treatment (solids reduction) required. Few
digesters are designed today to operate in this range, but there
are many still in use, including most Imhoff tanks and similar
unheated digesters with no mixing devices. Generally these
digesters are not very effective in digesting sludge.
Organisms in the middle temperature range are called the
MESOPHILIC (medium temperature loving) BACTERIA7; they
thrive between about 68°F (20°C) and 113°F (45°C). The op-
timum temperature range is 85°F (30°C) to 100°F (38°C), with
temperatures being maintained at about 95°F (35°C) in most
anaerobic digesters. Digestion at 95°F (35°C) may take from 5
to 50 days or more (normally around 25 to 30 days), depending
upon the required degree of volatile solids reduction and ade-
quacy of mixing. The so-called "High-Rate" processes are
usually operated within the mesophilic temperature range.
These are nothing more than procedures to obtain good mixing
so that the organisms and the food can be brought together to
allow the digestion processes to proceed as rapidly as possi-
ble. With the most favorable conditions, the time may be no
more than five days for an intermediate level of digestion.
Organisms in the third temperature range are called THER-
MOPHILIC (hot temperature loving) BACTERIA8 and they
thrive above 113°F (45°C). The optimum temperature range is
considered 120°F (49°C) to 135°F (57°C). The time required for
digestion in this range falls between 5 and 12 days, depending
upon operational conditions and degree of volatile solids re-
duction required. However, the problems of maintaining tem-
perature, sensitivity of the organisms to temperature change,
and some reported problems of poor solids-liquid separation
are reasons why only a few plants have actually been operated
in the thermophilic range.
You CANNOT merely raise the temperature of the digesters
and have a successful operation in another range. The bac-
teria must have time to adjust to the new temperature zone and
to develop a balanced culture before continuing to work. An
excellent rule for digestion is never change the temperature
more than one degree a day to allow the bacterial culture to
become acclimated (adjust to the temperature changes).
Secondary digestion tanks are sometimes used to allow liq-
uids (SUPERNATANT)9 to separate from the solids, to provide
a small amount of additional digestion, and to act as a SEED
SLUDGE10 source (the settled, digested sludge). However, di-
gestion tanks generally have too small a surface-area-to-depth
ratio to be good sedimentation tanks. Separation of solids from
liquids is more efficient in other processes such as centrifuges,
vacuum filters, filter presses, lagoons or in tanks designed for
separation. If a significant amount of digestion occurs in the
secondary tank, the result may be poor separation of solids.
Secondary digesters should be used for solids concentration
and for a reservoir of alkalinity and seed sludge which may be
returned to the primary digester when needed.
You have certain other items you can use for control in addi-
tion to mixing and temperature selection. These include:
1.	Varying the sludge concentration or water added to the
system;
2.	Varying the rate and frequency of feeding, with continuous
feed the most desirable;
3.	Closely controlling grit and skimming in order that capacity
of the tank is reduced as little as possible by these materi-
als;
4.	Cleaning regularly to maintain capacity;
5.	A good maintenance program to maintain the maximum
degree of flexibility; and
6.	Maintaining records and laboratory control in order that
process condition is known at all times.
Although anaerobic digestion is a complex process and only
a portion of its theory is understood, enough is known to allow
you to exercise good operational control. For anaerobic sludge
digestion as for any of the wastewater processes, remember
that for the most successful operation you need to do the fol-
lowing;
1.	Understand the theory of the process so you know what you
are basically trying to do;
2.	Know your facilities thoroughly so that you can attain
maximum flexibility of operation;
4	Buffer. A solution or liquid whose chemical makeup neutralizes acids or bases without a great change in pH.
5	Alkalinity (AL-ka-LIN-ity). The capacity of water or wastewater to neutralize acids. This capacity Is caused by the water's content of
carbonate, bicarbonate, hydroxide, and occasionally borate, silicate and phosphate. Alkalinity is expressed in milligrams per liter of
equivalent calcium carbonate. Alkalinity is not the same as pH because water does not have to be strongly basic (high pH) to have a high
alkalinity. Alkalinity is a measure of how much acid can be added to a liquid without causing a great change in pH.
6	Psychrophilic Bacteria (organisms) (sy-kro-FILL-lick). Cold temperature bacteria. A group of bacteria that grow and thrive in temperatures
below 68 °F (20°C).
7	Mesophilic Bacteria (mess-o-FILL-lick). Medium temperature bacteria. A group of bacteria that grow and thrive in a moderate temperature
range between 68°F (20°) and 113°F (45°C). The optimum temperature range for these bacteria in anaerobic digestion is 85°F (30°C) to
100"F (38°C).
8	Thermophilic Bacteria (thermo-FILL-lick). Hot temperature bacteria. A group of bacteria that grow and thrive in temperatures above 113°F
(45°C). The optimum temperature range for these bacteria in anaerobic digestion is 120°F (49°C) to 13S°F (57°C).
9	Supernatant (su-per-NAY-tent). Liquid removed from settled sludge. Supernatant commonly refers to the liquid between the sludge on the
bottom and the scum on the surface of an anaerobic digester. This liquid is usually returned to the influent wet well or to the primary clarifier.
10	Seed Sludge. In wastewater treatment, seed, seed culture or seed sludge refers to a mass of sludge which contains very concentrated
populations of microorganisms. When a seed sludge is mixed with the wastewater or sludge being treated, the process of biological
decomposition takes place more rapidly.

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102 Treatment Plants
3.	Keep careful records and use laboratory analyses to follow
the process continually; and
4.	Maintain your facilities in the best possible condition at all
times.
QUESTIONS
Write your answers in a notebook and then compare your
answers with those on page 174.
12.01 A Why must raw sludge be digested?
12.01B What happens during anaerobic digestion?
12.01C What are some of the important factors in controlling
the rate of reproduction of acid forming and methane
fermenting bacteria in an anaerobic digester?
12.1 COMPONENTS IN THE ANAEROBIC SLUDGE
DIGESTION PROCESS
To understand and operate an anaerobic sludge digester,
the operator must be familiar with the location and function of
the various components of the digestion facility.
12.10 Pipelines and Valves
Raw sludge pipelines are usually constructed of cast iron or
steel to withstand pumping pressures. In recent years glass-
lined or epoxy-lined sludge lines have been used to reduce the
problem of grease deposits. These deposits cut capacity and
may cause stoppages. To clean lines some plants use steam,
"go-devil" type cleaners and/or hot chemical solutions such as
T.S.P.
The valves used in sludge and scum lines are mostly of the
plug type. They give positive control where a gate or butterfly
valve may become blocked by rags or other material which will
not allow the valve to seat. In some cases a gate or butterfly
valve is indicated because a quick-closing plug valve could
result in water hammer and damage the pipeline.
£
CAUTION
1
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QUESTIONS
Write your answers in a notebook and then compare your
answers with those on page 174.
12.1 OA Why are plug type valves used in sludge lines?
12.1 OB Why should a positive displacement pump NEVER
be started against a closed valve?
12.10C Why should a sludge line NEVER be closed at both
ends?
12.11 The Anaerobic Digester
Anaerobic digestion tanks may be cylindrical or cubical in
shape. Most tanks constructed today are cylindrical. The floor
of the tank is sloped so that sand, grit, and heavy sludge will
tend to be removed from the tank. Most digesters constructed
today have either fixed or floating covers. The parts of a diges-
ter and their purposes are summarized in Table 12.1.
TABLE 12.1 PURPOSE OF ANAEROBIC SLUDGE
DIGESTER PARTS
Part*
1.	Sludge Feed
2.	Draft Tube
3.	Gas Injectors
4.	Hot Water Jacket
5.	Deflection Shield
6.	Gas Mixer
7.	Gas Draw-off
8.	Hot Water Piping
9.	Sludge Draw-off
10.	Supernate (supernatant)
Draw-off Tubes
11.	Supernate (supernatant) Box
12.	Water Seal
13.	Vacuum Relief
14.	Pressure Relief
15.	Flame Arrester
16.	Sediment Trap
17.	Condensate Drain
18.	Gas Piping
Purpose
Conveys sludge to digester
for treatment.
Directs mixture of raw and di-
gested sludge to heating re-
gion.
Inject gas into sludge to mix
sludge and increase heat
transfer.
Contains hot water that heats
sludge.
Deflects heated sludge
throughout digester.
Pumps gas from gas draw-off
to gas injectors.
Draws gas from top of diges-
ter to gas system.
Conveys hot water from heat
exchanger to hot water jacket.
Removes digested sludge
from bottom of digester.
Draw off supernatant from
various levels in digester.
Collects supernatant for
transport to headworks or
primary clarifier influent.
Prevents air entering digester
or digester gas from escap-
ing. Prevents development of
explosive conditions.
Relieves excessive vacuums
so digester cover will not col-
Relieves excessive pressures
in digester so water seal will
not be blown out.
Prevents spark or flame from
entering digester.
Traps sediment in digester
gas.
Drains condensate removed
from digester gas.
Conveys digester gas from
digester to heaters, mixers or
waste gas burners (See Sec-
tion 12.12, Gas System").
•Numbers correspond with parts on Figures 12.3 and 12.4

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Sludge Digestion 103
12.110	Fixed Cover Tanks
A fixed cover tank has a stationary roof, generally slab, coni-
cal, or cone-shaped, and constructed of concrete or steel. A
typical fixed cover digester is shown in Fig. 12.3. Both types of
covers are normally designed to maintain no more than an
eight-inch (20 cm) water column of gas pressure on the tank
roof (Fig. 12.4), but some are designed for a pressure of 25
inches (64 cm) or more. The domed cover is designed to hold a
larger volume of gas. Any type of mixing device may be used
with a fixed cover tank, and the tank must be equipped with
pressure and vacuum relief valves.
A fixed cover digester can have an explosive mixture in the
tank when sludge is withdrawn if proper precautions are not
taken to prevent air from being drawn into the tank. Each time
a new charge of raw sludge is added, an equal amount of
supernatant is displaced because the tank is maintained at a
fixed level.
12.111	Floating Cover
A floating cover moves up and down with the tank level and
gas pressure. Normally the vertical travel of the cover is about
eight feet (2.5 m), with stops (corbels) or landing edges for
down (lowering) control and maximum water level for upward
travel. Maximum water level is controlled by an overflow pipe
that must be kept clear to prevent damage to the floating cover
by overfilling. Gas pressure is dependent upon the weight of
the cover. The advantages of a floating cover include less
danger of explosive mixtures forming in the digester, better
control of supernatant withdrawal, and better control of scum
blankets. Disadvantages include higher construction and main-
tenance costs. For more details on floating cover digesters,
see Section 12.16, "Floating-Cover Digesters."
12.112	Digester Depth
A typical operation depth for digesters is around 20 feet (6
m) (side wall water level depth). The bottom slopes downward
to the center of the tank. A gas space of two to three feet (0.6 to
1.0 m) is usually provided above normal liquid sludge level, but
some floating covers allow more room for gas storage.
12.113	Raw Sludge Inlet
Typically the raw sludge feed is piped to the top of the pri-
mary digester and admitted on the side opposite the supernat-
ant overflow pipe (Figs. 12.3 and 12.4) to the secondary diges-
ter. Usually this line also carries any recirculated digested
sludge in the system so that the raw sludge is immediately
seeded with bacteria as it enters the tank.
12.114	Supernatant Tubes (Figs. 12.3 and 12.5)
On a fixed cover digester there may be three to five super-
natant tubes set at different levels for supernatant removal.
Normally only one tube is used at a time. The tube used is
selected to return the supernatant liquor with the lowest quan-
tity of solids back to the primary clarifier, or the sludge drying
beds, provided space is available.
A single adjustable tube is also used at some plants. On the
floating cover digester there is usually only one supernatant
tube. This may be adjusted to pull supernatant liquor from
various levels of the tank by raising or lowering the tube. In
smaller plants the supernatant withdrawal may be done only
once or twice a day, because the floating cover allows the tank
to handle volume changes. An adjustable tube usually allows a
supernatant with the least solids content to be selected. The
digester should be visually checked a minimum of once per
day for liquor levels to prevent overfilling and structural dam-
age to the tank.
12.115 Sludge Draw-off Lines (Figs. 12.3 and 12.4)
The sludge draw-off lines are typically placed on blocks
along the sloping floor of the digester. Sludge is withdrawn
from the center of the tank. Very seldom are they placed under
the floor of the digester because they would not be accessible
in case of blockages. These lines are normally six inches (150
mm) in diameter and equipped with plug valves. The lines are
used to transfer the digested sludge periodically to a sludge
disposal system of either drying beds or some type of dewater-
ing system. These lines also transfer seed sludge from the
secondary digester to the primary digester and recirculate bot-
tom sludge to seed and break up a scum blanket.
QUESTIONS
Write your answers in a notebook and then compare your
answers with those on page 174.
12.11A Why should you maintain no more than an eight-inch
(20 cm) water column of gas pressure on the roof of a
fixed cover digester?
12.11B Why must a fixed cover digester be equipped with
pressure and vacuum relief valves?
12.11C What are the advantages of a floating cover in com-
parison with a fixed cover digester?
12.11D Why is it desirable to mix recirculated digester sludge
with raw sludge?
WfefATi
END OF LESSON 1 OF 6 LESSONS
on
SLUDGE DIGESTION AND SOLIDS HANDLING
Please answer the discussion and review questions before
continuing with Lesson 2.

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6. OAS MIXER
11.SUPERNATE
/BOX
(EFFLUENT
LINE NOT
SHOWN TO
PRIMARY
EFFLUENT
CHANNEL)
5. DEFLECTION SHIELD
7. CAS DRAW-OFF
^ ~y FLOW
FLOW
8. HOT WATER PIPING
4FEET*
il ihh. ."T i
Mp -i
'l i> 'f
ii jji
n mill ,i
II 'Sti l>
UU'J
1. 3LUDQE FEED
10. SUPERNATE
DRAW-OFF
TUBES
HEAT
TRANSFER
OCCURS
IN THIS
REGION
4.H0T WATER JACKET
l££ECZ
3. OAS INJECTORS
2. DRAFT TUBE
SUPPORT LESS
V
9. SLUDGE DRAW-OFF

• DISTANCE BELOW LWUIO SURFACE
O
®
S
3
(D
3
D>
3
Fig. 12.3 Fixed cover digester
(Permission of County Sanitation Districts of Los Angeles County, California)

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INLET BOX
WATER SEAL
--i-LLJ/
-NORMAL WATER LEVEL
I? "^SUPERNATANT BOX
£i AND TUBES
SLUDGE DRAW OFF LINE
DIGESTER
NOTE: USUALLY WATER SEALS ARE LOCATED
IN THE VERTICAL SIDEWALLS OF
FL0ATIN6 COVER DIGESTERS, RATHER
THAN AS SHOWN ON ROOF.
15. FLAME ARRESTER-
13. VACUUM RELIEF /	
14.
PRESSURE RELIEF
18. GAS PIPING
FLAME ARRESTER
VALVE
ATMOSPHERIC
PRESSURE
?T
DIGESTER GAS PRESSURE
17. CONDENSATE DRAIN
12. WATER SEAL
INCHES OF
WATER PRESSURE
V-V. •; p.'.;.7- •' ; : fi. ' !¦'..• • • i ;
I -V • .. .A.-. *	A .. .A- ; 'A
V/V ». W•*.::: : . >:A
DIGESTER ROOF
Fig. 12.4 Water seal on digester

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106 Treatment Plants
3 FT. SUPERNATANT TUBE IN SERVICE
ADJUSTABLE RINGS-THREE LENGTHS
DIGESTER ROOF
v A
SUPER-
NATANT
BOX
NORMAL DIGESTER WATER LEVEL
o
I— oc
UJ
Ujf—
ZC/O
	UJ
—ICS
h-a
oc
a=
CD
O
O
	I
CO
CD
CD
U_
cd
o
ID
CD
O
O
ac
ao
CD
ac
CO
Fig. 12.5 Supernatant tubes and box for fixed cover digester

-------
Sludge Digestion 107
DISCUSSION AND REVIEW QUESTIONS
Chapter 12. SLUDGE DIGESTION AND SOLIDS HANDLING
(Lesson 1 of 6 Lessons)
At the end of each lesson in this chapter you will find some
discussion and review questions which you should work before
continuing. The purpose of these questions is to indicate to you
how well you understand the material in the lesson.
Write the answers to these questions in your notebook be-
fore continuing.
1.	Briefly explain what happens when sludge is added to an
anaerobic digester.
2.	Why is it important to keep the contents of a digester well
mixed?
3.	Why should the floor of a digester be sloped?
4.	Why do digesters have supernatant tubes?
CHAPTER 12. SLUDGE DIGESTION AND SOLIDS HANDLING
(Lesson 2 of 6 Lessons)
12.12 Gas System (Fig. 12.6)11
The anaerobic digestion process produces 8 to 12 cubic feet
of gas for every pound (0.44 to 0.75 cu m/kg) of volatile matter
ADDED, and from 12 to 18 cubic feet of gas for every pound
(0.75 to 1.12 cu m/kg) of volatile matter DESTROYED, depend-
ing upon the characteristics of the sludge. The gas consists
mainly of methane (CHJ and carbon dioxide (C02). The
methane content of the gas in a properly functioning digester
will vary from 65 to 70 percent, with carbon dioxide running
around 30 to 35 percent by volume. One or two percent of the
digester gas is composed of various other gases.
Digester gas (due to the methane) possesses a heat value
of approximately 500 to 600 B71/12 per cubic foot (18,630 to
22,350 k J13/cu m), 900 to 1200 BTU per cubic foot (33,530 to
44,700 k J leu m).
WARNING
Pi 6641"	CAW £XTfe£M-ELV DAN £r EG OX
IN-HA/O WAY^. WWBN MIX BP WITH OX\>(-r£M
IT CAW f=OUM &XPL04lVe MIXTURES, ANP IT
AL40 CAM CAU^e ASPHYXIATION 012 OXV6&N
STAEVATlOU. ^MOK/N6,OP€N	OR
4PAQ&Z MUST MOT &£ TOU£GAT£D ACOUMD
TUe DI6E4TEJ2S CM 4LUD&E WMPfNdr FA£ILITIE4
Digester gas is used in plants in various ways: for heating
and mixing the digesters, for heating the plant buildings, for
running engines, for air blowers for the activated sludge pro-
cess, or for electrical power for the plant.
The gas system removes the gas from the digester to a point
of use, or to be burned in the waste gas burner as excess. The
following items are components of the gas system.
12.120 Gas Dome
This is a point in the digester roof where the gas from the
tank is removed. On fixed cover tanks there may also be a
water seal (Fig. 12.4) to protect the tank structure from excess
POSITIVE PRESSURE14, or vacuum created by withdrawal of
sludge or gas too rapidly.
If gas pressure is allowed to build up to 11 inches (28 cm) of
water column pressure, it will escape around the water seal to
the atmosphere without lifting the roof. If sludge is drawn or
gas used too rapidly, the vacuum could exceed eight inches
(20 cm) and break the water seal, thus allowing air to enter the
tank. Without the water seal, the vacuum could become great
enough to collapse the tank. Air in the tank creates an explo-
sive condition. In addition, sulfuric acid corrosion is often found
where air is consistently in contact with the gas. The pipeline
between the gas storage tank and the digester will protect the
digester from water seal leaks, if the line is clear. When liquids
are pumped into the digester, gas can go out the line to the
storage tank and when liquids are pumped out of the digester,
gas can return through the line.
11	Many figures in this section were made available courtesy of VAREC, Inc., 301 East Alondra Blvd., Gardena, California 90247. Mention of
commercial products or manufacturers is for illustrative purposes and does not imply endorsement by California State University, Sac-
ramento, EPAIWQO, or any state or federal agency.
12	BTU (BEE-TEA-YOU): British Thermal Unit. The amount of heat required to raise the temperature of one pound of water one degree
Fahrenheit.
13	Joule (jewel). A measure of energy, work or quantity of heat. One joule is the work done when the point of application of a force of one
newton is displaced a distance of one meter in the direction of the force.
14	Positive Pressure. A positive pressure is a pressure greater than atmospheric. It is measured as pounds per square inch (psi) or as Inches
of water column. A negative pressure (vacuum) is less than atmospheric and is sometimes measured in inches of mercury. In the metric
system pressures are measured in kglsq m or kglsq cm.

-------
"VAREC"
PRESSURE RELIEF & VACUUM
BREAKER WITH FLAME ARRESTER
FIG. 5800-81
TYPICAL FLOW AND INSTALLATION DIAGRAM
MULTIPLE DIGESTER GAS SYSTEM
"VAREC"
COVER POSITION INDICATOR
WITH HI-LOW ALARM
FIG. 101
"VAREC"
SEDIMENT & DRIP TRAP ASSEMBLY
FIG. 233, 218, 246
TO PLANT UTILITIES SERVICE GAS
"VAREC"
FLAME TRAP ASSEMBLY
FIG. 450
"VAREC
MANHOLE COVER
FIG. 220-82
"VAREC
HANDHOLE
FIG. 42-81
COMPRESSOR
DIGESTER
(Fixed or floating roof)
VAREC''
MANHOLE COVER-FIG. 220-82
VAREC
PRESSURE REGULATOR
FIG. 187
"VAREC"
FLAME TRAP ASSEMBLY
FIG. 450
"VAREC"
GAS PURIFIER
FIG. 234 \
DIGESTER
(Fixed or floating roof)
"VAREC"
DRIP TRAP
FIG. 246
"VAREC"
CHECK VALVE
FIG. 211-92
'VAREC"
PRESSURE REGULATOR
FIG. 186
"VAREC
FLAME TRAP ASSEMBLY
FIG. 450
METER
(By others)
"VAREC
CHECK VALVE "VflREC
FIG. 211-92 QRip TRftp
FIG. 246
VAREC
WASTE GAS BURNER-i
METER
(By others)
FIG. 239
-s
& U
'VAREC
3 UNIT MANOMETER
FIG. 217 "VAREC"
PRESSURE RELIEF & FLAME
TRAP ASSEMBLY-FIG. 440
"VAREC"
SEDIMENT & DRIP TRAP ASSEMBLY
FIG. 233, 218,246
TO BOILER
"VAREC"
PRESSURE REGULATOR
FIG. 187
VAREC"
FLAME
TRAP
FIG. 52
"VAREC"
DRIP TRAP-FIG. 246
This schematic is for general guidance purposes
only and is not intended to represent a specific design.
"VAREC"
EXPLOSION RELIEF
VALVE-FIG. 700-81
(Install outside
building)
Fig. 12.6 Digester gas system
(Courtesy of VAREC)

-------
Sludge Digestion 109
QUESTIONS
Write your answers in a notebook and then compare your
answers with those on page 174.
12.12A What are the two main gaseous components of di-
gester gas after gas production has become well es-
tablished?
12.128 What are some uses of digester gas?
12.12C Why must the digester gas be controlled with ex-
treme caution?
12.121 Pressure Relief and Vacuum Relief Valves
(Fig. 12.7, VAREC Fig. No. 5800-81)
The pressure relief valve and the vacuum relief valve both
are attached to a common pipe, but each works independently.
The pressure relief valve is equipped with a seat and weighted
with lead washer weights. Each weight is stamped with its
equivalent WATER COLUMN HEIGHT15 such as 1 inch H20 or
3 inches H20 (2.5 or 7.5 cm). There should be sufficient
weights, combined with the weight of the pallet, to equal the
designed holding pressure of the tank. The gas pressure is
normally established between six inches and eight inches (15
and 20 cm) of water. Check pressure with a water manometer
and adjust lead weights as needed to maintain correct pres-
sure. If the gas pressure in the tank exceeds the pop-off set-
ting, then the valve will open and vent to the atmosphere for a
couple of minutes through the pressure relief valve. This
should occur before the water seal blows out. The water seal
can be broken when a tank is overpumped or gas removal is
too slow.
The vacuum relief valve operates similarly to the pressure
relief valve except that it relieves negative pressures to prevent
the tank from collapsing. Operation of either one of these
valves is undesirable, because this allows the mixing of diges-
ter gas with air and can create an explosion outside the tank if
the pressure relief valve opens and inside the tank if the vac-
uum relief valve opens.
These two valves should be checked at least every six
months for proper operation and daily under freezing condi-
tions.
QUESTIONS
Write your answers in a notebook and then compare your
answers with those on page 174.
12.12D How would you adjust the pressure relief valve to
prevent pressures within the digester from exceeding
the design pressure?
12.12E How could the water seal be broken in a digester?
12.12F Why is the operation of either the pressure relief
valve or the vacuum relief valve undesirable?
12.122 Flame Arresters (Fig. 12.9, VAREC Fig. No. 450)
A typical flame arrester is a rectangular box holding approx-
imately 50 to 100 corrugated aluminum plates with punched
holes. If a flame should develop in the gas line, it would be
cooled below the ignition point as it attempted to pass through
the baffles, but gas could flow through with little loss in pres-
sure.
To prevent explosions, flame arresters should be in-
stalled:
1.	Between vacuum and pressure relief valves and the di-
gester dome;
2.	After sediment trap on gas line from digester;
3.	At waste gas burner; and
4.	Before every boiler, furnace, or flame.
Flame arresters should be serviced every three months. Be-
fore servicing a flame arrester, valve off the gas flow to the line
and put out all flames and pilot lights in the area. Remove the
end housing and slide out cartridge containing flame arrester
baffles. The cartridge is designed to slide open to the baffles
and may be cleaned without complete dismantling. Separate
and wash the baffle plates in a solvent and dry. A buildup of
scale, salts from condensate, and residue buildup on the
plates restricts gas flow. When the unit is reassembled, it
should be tested for leaks by swabbing a soapsuds solution
over potential leaky areas and inspecting for bubbles.
12.123 Thermal Valves
Another protective device installed near a flame source and
near the gas dome is the thermal valve. The valve is round,
with a weighted seat attached to a stem. The stem sets on a
fusible disk holding the seat up. If enough heat is generated by
a flame, the fusible element melts and drops the stem and
valve seat to cut off gas flow. Most valves are equipped with a
wing nut on top of the valve body. If the wing nut is removed, it
uncovers a glass tube which shows visually if the stem is up. If
the stem cannot be seen, then the valve is closed and no gas
can flow. If this occurs, the valve is removed and heated in
boiling water to remove the melted fusible slug. A new slug is
installed (slightly larger than an aspirin tablet), the stem re-
placed on top of it, and the valve is ready for service. These
valves should be dismantled at least once a year in order to be
positive that the stem is free to fall and not gummed up with
residue or scale from the gas.
Figure 12.10 (VAREC Fig. No. 440) shows a flame arrester
connected to a pressure relief valve.
QUESTIONS
Write your answers in a notebook and then compare your
answers with those on page 175.
12.12G How would you service a flame arrester?
12.12H Why should you check the thermal valves at least
once a year?
WARNING
A &A4, M IXTUCE. CAflO OP 5.7-Tb 13.5.%
Dl
-------
110 Treatment Plants
PRESSURE RELIEF AND
VACUUM BREAKER VALVE
WITH FLAME ARRESTER
for Use on Digesters and Gas Holders
The "Varec" Figure No. 5800-81 unit consists
of a Figure No. 2000-81 Pressure Relief and
Vacuum Breaker Valve and a Figure No. 50-91
Flame Arrester. Maximum protection against ex-
cessive pressure and vacuum is afforded and acci-
dental ignition of sludge gas within the digester
and gas holder from external sources is eliminated.
Valve is light weight and corrosion resistant
construction. Interior parts are readily accessible
for inspection and maintenance purposes. Pallets
are dead weight loaded and include replaceable
synthetic rubber sludge gas resistant seat inserts
to insure gas tight seating and long life service
with minimum maintenance. Seat rings, pallets
and guide posts are anodized for extra corrosion
protection and are removable.
Flame arrester consists of a'flame arresting bank
assembly enclosed within a gas-tight housing. 1 he
bank consists of a multiple number of individual
corrugated stamped sheets and is readily remov-
able from the housing for inspection and cleaning
purposes. The arrester is listed by Underwriters
Laboratories and is approved by Associated 1'ac-
tory Mutual Laboratories.
FIGURE NO. 5800-81
SETTINGS
Valves are furnished with variable pressure
settings from 2" to 10" of water in increments of
l" of water. Vacuum setting is 2" of water unless
otherwise specified.
STANDARD MATERIALS OF CONSTRUCTION
Valve is substantially aluminum (impervious
to the attack of sludge gas) throughout except
for synthetic rubber pallet seat inserts and steel
studs, nuts and screws.
Flame arrester bank is all aluminum and the
housing consists of cast aluminum ends and cast
iron side and cover plates. Gaskets are graphited
asbestos.

-------
Sludge Digestion 111
--

-------
112 Treatment Plants
An Explosive Gas Mixture was Accidentally Ignited,
The Digester Cover Blew Off,
And Landed on Top of a Pickup Truck.
Fig. 12.8 Results of digester explosion

-------
Sludge Digestion 113
. J FLAME TRAP ASSEMBLY
Fig. No. 450
FIGURE NO. 450
Varec Fig. No. 450 is a combined unit consisting of
a Fig. No. 430 Thermal Operated Shutoff Valve and
a Fig. No. 53-81 Flame Arrester. The Fig. No. 450
assembly is normally installed in waste gas lines just
upstream of waste gas burners and/or as close as
possible to any point of possible combustion —and
where back pressure control is not required. This
unit serves much the same purpose as the Fig. No.
440 except the back pressure control feature is not
included.
FEATURES
Unit provides a simple flame arrester and flame
trap assembly. The Fig. No. 430 including a fusible
element (compression type) is rated at 260°F and
will shut off gas flow within 15 seconds when ele-
ment is contacted by flame. Indicator rod shows the
valve position when viewed through the Pyrex sight
glass. In certain materials of construction, the Fig.
No. 53-81 unit is Underwriters' Laboratories listed
and approved by Associated Factory Mutual Labo-
ratories. Unit may be installed in either vertical or
horizontal piping. Also, unit may be installed in either
direction with the Fig. No. 430 Shutoff Valve posi-
tioned to the closest possible source of ignition.

-------
114 Treatment Plants
125 LB. STD.
ANSI FLANGES
WINGED
INSPECTION CAP
SIGHT GLASS
INDICATOR ROD
PEEPHOLES
FLAME
ARRESTER
o
GAS FLOW
i^i
GAS TIGHT
FUSE PLUG
COVER
GASKET
\
DRAIN PLUG
^ REMOVABLE
BANK
PALLET
THERMAL
ELEMENT
THERMAL
SHUT-OFF VALVE
z
3
X
a
s
o
K
&
s
O
111
BC
3
CO
(0
Ul
a
a.
tc
ui
h
<
U.
O
(0
Ul
x
G
Z
SIZE AND DIMENSIONS
SIZE
A
B
C
D
2"
9
3Va
14 Va
8%
3"
11 Vs
4'/2
16
10
4"
12%
5
20
11%
6"
14Ve
5Ve
24%
15
8"
15%
7 V*
32'/e
22'/<
2.0 	
2"

3"
MATERIALS OF CONSTRUCTION
Flame Arrester Housing — heavy cast aluminum
Flame Arrester Element — aluminum
Thermal Valve Body & Cover — aluminum
Guide Steel —stainless steel
Sight Glass — Pyrex
Cover and Cap Gaskets — graphited asbestos
Sight Glass Gasket — synthetic rubber
Spring — stainless steel
(UNIT SIZE)
4	>	12	16	20	24	28
CAPACITY IN THOUSANDS CUBIC FEET PER HOUR GAS (SP. GR. 0.7)
All designs subject to change without notice. Such change does not imply any obligation on the part of Varec with respect to prior equipment shipments. Installation, mounting
arrangement, and dimensions are preliminary general information not to be used for construction. Certified drawings are available.

-------
Sludge Digestion 115
I i" at PRESSURE RELIEF and
FLAME TRAP ASSEMBLY
FIGURE NO. 440
A Varec Fig. No. 440 is a combined unit consisting
of a Fig. No. 386 Back Pressure Regulator and a Fig.
No. 53-81 Flame Arrester; in addition to the units
being combined, there is also a thermal shut-off
control valve.
The Fig. No. 440 assembly is normally installed in
waste gas lines, just upstream of the waste gas
burners. The purpose of the unit is to maintain a
predetermined back pressure throughout the gas
control system so that only surplus gas is flared; and
to inhibit the propagation of a possible flame flash-
back from the flare into the gas control system.
FEATURES
Unit provides simple, sensitive operation as well
as arrestment. The control unit is furnished as stand-
ard with a fusible element rated at 260°F and pro-
vides for a gas flow shut down within 15 seconds. The
fusible element being a compression type, precludes
valve shut off unless contacted by flame.
The Varec Flame Arrester Fig. No. 53-81 portion of
this unit is listed by Underwriters' Laboratories and
approved by Associated Factory Mutual Laboratories
when furnished in certain materials of construction.
Drip trap connection is provided as standard. The net
free area through the flame arrester bank is approxi-
mately four times the nominal pipe size connection;
each flow passageway has a net free area of approxi-
mately 0.042 sq. inches.
All sizes are standard with visual indicator for easy
adjustment by operator. Range of operation is 2 to
12 inches ot water (special springs available for
higher operating pressures when so specified). As
standard, unit is«supplied by factory set at 6 inches
of water when not specified otherwise. Schematics,
dimension charts, and flow curves shown on follow-
ing page.
MATERIALS OF CONSTRUCTION
Regulator Body — cast aluminum.
Diaphragm Cast — cast aluminum.
Bonnet — cast aluminum.
Spring — cadmium-plated steel.
Diaphragm — corded synthetic rubber.
Cap — iron.
Thermal Shutoff Valve — aluminum and
stainless steel.
Flame Arrester Housing — heavy cast aluminum.
Flame Arrester Element — aluminum.

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116 Treatment Plants
SYNTHETIC
RUBBER
DIAPHRAGM
CONTROL LINE
CONNECTION
N.P.T.

FIGURE NO. 440
CONN. "A1
""SETTING
SCALE
CONN. "B'
'/<" PIPE
VENT TO
ATMOSPHERE
304 STAINLESS
STEEL DOUBLE
ACTING NEEDLE
VALVE
CONN. "A"
SETTING
INDICATOR
NON-RISING
ADJUSTING
SCREW
COMPRESSION
SPRING
CONN. "B"
304
STAINLESS STEEL
I
GAS
FLOW
PRESSURE
RELIEF REGULATOR
(D
125 PSI-ANSI
FLANGE DRILLING
PACKING
GLAND
SECTION A-A
BY-PASS
VALVE

-©-
TO WASTE
GAS BURNER -
-	GAS TIGHT
FUSE PLUG,
NO PACKING
GLAND
-	FUSIBLE
ELEMENT
SIZES AND DIMENSIONS
SIZE
A
B
C
D
E
2"
20%
3Vb
4 
<0
UI
tc
0.
2.0
1.5
1.0
0.5
I

/











—
r	









i


























/ /

















5	10	15	20	25	30	35	40
CAPACITY IN THOUSANDS CUBIC FEET PER HOUR GAS (SP. GR. 0.7)
45
Ail designs subject to change without notice. Such change does not imply any obligation on the part of Varec with respect to prior equipment shipments. Installation, mounting
arrangement, and dimensions are preliminary general information not to be used for construction. Certified drawings are available.

-------
Sludge Digestion 117
12.124	Sediment Traps (Fig. 12.11, VAREC Fig. No. 233)
A sediment trap is a tank 12 to 13 inches (30 to 33 cm) in
diameter and two to three feet (0.6 to 1 m) in length. The trap is
usually located on top of the digester near the gas dome. The
inlet gas line is near the top of the tank and on the side. The
outlet line comes directly from the top of the sediment tank.
The sediment trap is also equipped with a perforated inner
baffle, and a condensate drain near the bottom. The gas enters
the side at the top of the tank, passes down and through the
baffle, then up and out the top. Moisture is collected from the
gas in the trap, and any large pieces of scale are trapped
before entering the gas system. The trap should be drained of
condensate frequently but may have to be drained twice a day
during cold weather, because greater amounts of water will be
condensed.
12.125	Drip Traps — Condensate Traps (Fig. 12.11,
VAREC Fig. Nos. 245 and 246)
Digester gas is quite wet and in traveling from the heated
tank to a cooler temperature the water condenses. The water
must be trapped at low points in the system and removed, or it
will impede gas flow and cause damage to equipment, such as
compressors, and interfere with gas utilization. Traps are usu-
ally constructed to have a storage space of one to two quarts
(one or two liters) of water. All drip traps on gas lines should be
located in the open air and be of the manual operation type.
Traps should be drained at least once a day and possibly more
often in cold weather. Actual required frequency of draining
traps depends on location of trap in gas system, temperature
changes and digester mixing system. Automatic drip traps are
not recommended because many automatic traps are
equipped with a float and needle valve orifice and corrosion,
sediment, or scale in the gas system can keep the needle from
seating. The resulting leaks may create gas concentrations
with a potential hazard to life and equipment.
12.126	Gas Meters
Gas meters may be of various types, such as bellows, dia-
phragm, shunt flow, propeller, and orifice plate or differential
pressure. They are described in detail in the metering section
of Chapter 15, "Maintenance."
12.127	Manometers
Manometers are installed at several locations to indicate gas
pressure within the system in inches (or centimeters) of a
water column.
12.128	Pressure Regulators (Fig. 12.12, VAREC Fig. No.
386 and 180,186 and 187)
Pressure regulators are typically installed next to and before
the waste gas burner. Such regulators are usually of the dia-
phragm type and control the gas pressure on the whole diges-
ter gas system. They are normally set at eight inches (20 cm)
of water column by adjusting the spring tension on the dia-
phragm. Whenever an adjustment of a pressure setting is
made, check the gas system pressure with a manometer for
the proper range. If the gas pressure in the system is below
eight inches (20 cm) of water column, no gas flows to the water
column, the regulator opens slightly, allowing gas to flow to the
burner. If the pressure continues to increase, the regulator
opens further to compensate. The only maintenance this unit
requires is on the thermal valve on the discharge side which
protects the system from back flashes. This unit is spring
loaded and controlled by a fusible element that vents one side
of the diaphragm, thus stopping the gas flow when heated.
Maintenance includes checking for proper operation of the
regulator and of the fusible element. Gas regulators are also
placed at various points in the system to regulate the gas
pressure to boilers, heaters, and engines. Diaphragm condi-
tions in the regulators should be checked at periodic intervals.
12.129 Waste Gas Burner (Fig. 12.13)
Waste gas burners are used to burn the excess gas from the
digestion system. The waste gas burner is equipped with a
continuous burning pilot flame so that any excess gas will pass
through the gas regulator and be burned. The pilot flame
should be checked daily to be sure that it has not been
BLOWN OUT BY WIND. If the pilot is out, gas will be vented to
the atmosphere creating an odorous and potentially explosive
condition.
QUESTIONS
Write your answers in a notebook and then compare your
answers with those on page 175.
12.121 How frequently should you drain a sediment trap?
12.12J Why must drip or condensate traps be installed in
gas lines?
12.12K What is a deficiency in automatic drip and conden-
sate traps?
12.12L How would you adjust the gas pressure of the diges-
ter gas system?
12.12M Why should the pilot flame in the waste gas burner
be checked daily?
12.13	Sampling Well (Thief Hole) (Fig. 12.14, VAREC
Fig. Nos. 42-81 and 48-81)
The sampling well consists of a 3- or 4-inch pipe (150 or
200 mm) (with a hinged-seal cap) that goes into the digestion
tank, through the gas zone, and is always submerged a foot
(0.3 m) or so into the digester sludge. This permits the sam-
pling of the digester sludge without loss of digester gas pres-
sure, or the creation of dangerous conditions caused by the
mixing of air and digester gas. However, caution must be
used not to breathe gas which will always be present in the
sample well and will be released when first opened. A sam-
pling well is sometimes referred to as a "thief hole."
12.14	Digester Heating
Digesters can be heated in several ways. Some facilities
provide digesters heat by recirculating the digester sludge
through an external hot water heat exchanger (Figs. 12.15
and 12.16). Digester gas is used to fire the boiler, which is
best maintained between 140 (60°C) and 180°F (82°C) for
proper operation. The hot water is then pumped from the
boiler to the heat exchanger where it passes through the
jacket system, while the recirculating sludge passes through
an adjacent jacket, picking up heat from the hot water. In
some units the boiler and exchanger are combined and the
sludge also is passed through the unit or to the draft tube of
the gas mixer.
Circulation of 130°F (54°C) water through pipes or heating
coils attached to the inside wall of the digester is another
method of heating digesters. This approach creates problems
of cooking sludge on the pipes and insulating them, thus reduc-
ing the amount of heat transferred. Some facilities use sub-
merged combustion of the gas with heat exchange between
the hot gaseous products evolved and the liquid sludge.
Other plants inject steam directly into the digesters for
heating. The steam is produced in separate boilers or is re-

-------
118 Treatment Plants
FIG. NO. 233 & FIG. NO. 232
FLOW IN S.C.F.H. (0.7 SP. GR. GAS)
PRESSURE IN H;0
SIZE
0.2
0.3
0.5
0.75
1.0
1.25
1.5
2.0
2"
1,500
1,800
2,350
2,950
3,300
3,700
4,100
4,700
3"
3,250
4,000
5,150
6,500
7,300
8,150
8,950
10,250
4
5,700
7,000
8,950
11,200
12,650
14,150
15,500
17,800
6"
13,000
16,250
21,000
26,300
29,600
33,100
36,400
41,700
8"
17,000
21,000
29,000
36,000
42,000
47,000
51,000
60,000
FIGURE NO. 233
(with 218 and 246)
DRIP TRAPS
VAREC drip traps are installed for collection and
safe removal of condensate from low points in gas
control lines. Standard materials of construction are
356 H.T. aluminum body and cover and S.S. internal
working parts.
FIG. 245—Automatic Type: employs a float operated
needle valve. Standard with 1" NPT connection and
rated for maximum working pressure of 5 psig as
standard (25 psig WP available on special order).
FIG. 246 — Manually Operated Type: with ports and
shaft positively sealed by synthetic rubber "O" rings.
Designed such that gas cannot escape regardless of
disc position. Available with 1" NPT connection as
standard and 21/2 quart or 6 quart capacity. Rated
for a maximum working pressure of 5 psig (50 psig
WP rating available on special order.)
(Note: Fig. 218 and 246 are shown, but ARE NOT
standard with Sediment Trap)
SEDIMENT TRAPS
and DRIP TRAPS
SEDIMENT TRAPS
VAREC sediment traps are installed in gas control
piping for removing sediment/condensate from wet
gas; installation is normally upstream from meters,
regulators, and other similar control equipment. Such
removal is accomplished by a combination of cen-
trifugal force and a sharp drop in velocity as the gas
enters the trap.
The Fig. No. 233 is furnished in all fabricated steel
construction as standard with NPT or flanged con-
nections as specified. The Fig. No. 232 is furnished
in all cast iron construction as standard. The total
reservoir capacity in both units is 12 gallons. Both
units are standard with connections for drip trap
and/or sight glass (Fig. No. 218). Top cover is remov-
able for access. Maximum working pressure rating
for sediment traps is 25 psig.
Note: Thl» rating DOES NOT Include Drip Trap.
FIGURE NO. 245
FIGURE NO. 246
NOTE: Sediment trap (Fig. No. 232/233), drip trap (Fig. No. 245/
246), and sight glass (Fig. 218) must be ordered separately.

-------
Sludge Digestion 119
PIPE THREADED CONNECTIONS FURNISHED
WITH 2" & 3" SIZES WELDED FLANGED
CONNECTIONS FURNISHED WITH 4", 6' & p,~nnc lin oil
8' SIZES C50 LB. ASA F.F.)	PluiUKC IMO.
OUTLET
INLET
®
INSPECTION PIPE
DRIP TRAP
CONNECTION
BAFFLE
BLOWOUT t DRAIN CONNECTION 2" PIPE NIPPLE
FIG. NO. 233—DIMENSIONS
SIZE
A
B
C
D
E
F
2"
2
2
3%
22'/2
16
26 
-------
120 Treatment Plants
fa*
REGULATORS/
SINGLE PORT-Fig. No. 386
Single port regulators are ideal for gas control
systems not requiring very sensitive operation, but
needing "tight" shut-off.
VAREC Fig. No. 386 single port regulator provides
tight shut-off and will maintain upstream pressure
within approximately 10% of predetermined set pres-
sure. This regulator is an "on/off" type and not
"throttling" type as is a double port regulator. Fig.
180 Series.
Standard materials of construction include heavy
duty cast aluminum body and diaphgram housing;
aluminum plug and seat; stainless steel stem; and
nylon reinforced Buna-N rubber diaphragm with cad-
mium plated spring. Visual indicator provides for
easy adjustment of set point while in service. Unit
can be set in increments of 0.5" W.C.
This regulator requires only 1" W.C. to 2" W.C.
differential for full flow capacity; providing total pres-
sure drop across the valve is not more than 20" W.C.
The Figure 386 is a BACK PRESSURE regulator for
controlling upstream pressure over a range of 2.0"
W.C. to 12.0" W.C. It generally is used downstream
of gas meters (controls upstream of meter) or up-
stream of waste gas burners.
FIGURE NO. 386
FIGURE NO. 387
DOWNSTREAM PRESSURE REGULATOR
HAS BEEN DISCONTINUED. USE
FIGURE NO. 187

-------
Sludge Digestion 121

SETTING
SCALE
NON-RISING
ADJUSTING
SCREW
SYNTHETIC
RUBBER
DIAPHRAGM
SETTING
INDICATOR
COMPRESSION
SPRING
%" VENT
TO OUTSIDE
svanvs
uj/surrl
72 CONTROL
CONNECTION
 (f) 1.0
10	15	20	25	30	35
THOUSANDS S.C.F.H. 0.7 SPECIFIC GRAVITY - GAS
50
All designs subject to change without notice. Such change does not imply any obligation on the part of Varee with respect to prior equipment shipments. Installation, mounting
arrangement, and dimensions are preliminary general information not to be used for construction. Certified drawings are available.

-------
122 Treatment Plants
id*
REGULATORS-DOUBLE PORT
BALANCED PLUG-Fig. No. 180
Sewage gas systems require regulators that
provide very sensitive operation. VAREC 180 Series
regulators provide such operation through a setting
range of 0.4" W.C. vacuum, to 1.5" W.C. pressure, and
2.0" W.C. pressure to 20.0" W.C. pressure, respec-
tively. (Under certain conditions, these setting ranges
might be extended 15% at either end with some com-
promise in repeatability.)
Standard materials of construction include cast
aluminum body, galvanized steel or cast aluminum
diaphragm housing, nylon reinforced Buna-N rubber
diaphragm, and 304 S.S. plugs, seats, and other trim.
Special materials such as cast iron, cast steel, Teflon
diaphragms, etc., are also available.
VAREC regulators have minimum friction through
the linkage because all friction points are subject
only to rotary motion. The double port feature pro-
vides for very sensitive and smooth operation as, for
example, is required for vapor recovery systems and
"throttling" of fuel gas to engines. It should be noted
that temperature changes often will preclude a 100%
shutoff; this is characteristic of any double port/
balanced plug type regulator.
All VAREC regulators are "self-contained"—no
outside power source is required.
FIGURE 180
For use in a vapor recovery system, upstream con-
trol; i.e., regulating flow of "wet gas" from tanks to
vacuum line. Setting range of 0.4" W.C. vacuum to
1.5" W.C. pressure; only 0.4" W.C. differential over
set point required to obtain full flow capacity.
In "wet gas" (vaccum line) service, the predeter-
mined opening pressure of this regulator will not vary
more than Wo" water, providing the suction pressure
remains between atmospheric and 10" mercury.
FIGURE 181
For use in a vapor recovery system, downstream
control; i.e., regulating flow of "dry gas" from source
to repressure tanks.
Setting range and pressure differential for full flow
capacity is the same as the Fig. 180. Upstream pres-
sure to the Fig. 181 should be maintained between
atmospheric and 20 psig.
FIGURE 186
Primarily a BACK PRESSURE regulator, ideal for
fuel governors for gas engines, and control valves
for low pressure burners. Same balanced double port
configurations as 180 Series EXCEPT smaller dia-
phragm and addition of a spring provide a higher
setting range of 2.0" W.C. to 20.0" W.C. pressure.
Pressure differential across valve must not be
greater than 5 psig in order to maintain to 5% any
predetermined upstream pressure from 2.0" W.C. to
20.0" W.C. Full flow capacity requires only 1.5" W.C.
differential pressure.
FIGURE NO. 180
FIGURE 187
Primarily a REDUCING regulator; same configura-
tion as Fig. 186 above EXCEPT for use in "down-
stream control."
Full flow capacity requires only 1.5" W.C. pressure
differential. Regulator will maintain to approximately
5% any predetermined downstream pressure pro-
viding upstream pressure is maintained between
atmospheric and 20 psig.
It should be noted that the above-described regu-
lators are sometimes referred to as "back pressure
regulators," "pressure relief valves," "low pressure
relief valves," "pressure reducing valves," etc.
Detailed schematics, dimensions, materials of con-
struction, and flow capacity curves relative to the
above regulators will be found on the following page.

-------
Sludge Digestion 123
FLOW**
SECTION A-A
Fl«. 1M
SECTION A-A
FIC. 117
VAfifcC
FLOW
2 w
6S
Ui
u.
u.
oc
iaj
I-
2
OS	IS
III J	I
K hi	O
3 K	Z
« 2	-
s? 8
K ?
1" N.P.T.
•12%" FOR 8" SIZE ONLY
r 1%" 2
FIG. 116—BACK PRESSURE TYPE (UPSTREAM CONTROL)
FIG. 117—PRESSURE REDUCING TYPE (DOWNSTREAM CONTROL)
FIGURE NO'S. 186 & 187
3"	4"
IRON WHEN IKON MOT SPECIFIED.
STEEL WHEN STEEL BODY SPECIFIED.
(VALVE FlUC ft SEATS Ail M4 S.S.)
I" ft IV SIZES TMREADtO (NFT).
2" ft LAMER SIZES, FIANCES.
12S fSI ANSJHFF) ALUMINUM A IRON.
150 PSI ANSI (RF) STEEL.
(REGULATOR SIZE)
20 24 28 32 36 40
THOUSANDS S.C.F.H. 0.7 SP. GR. GAS
SIZES, DIMENSIONS, WEI6HTS —FIG. NOS. 186 and 187
SIZE



Approx. Wt., Lb».
Screwed
End
Flanged
End
A
B
C
Net
Ship.
1"
—
7
5
3'/a
85
175
1 1/2 "
—
7'/l6
5%
3'/8
115
180
—
2"
7%
7"/l6
41/4
125
190
—
3"

10
51/«
160
233
—
4"
93/ie
12
5'/a
190
260
—
6"
11'/l6
15
7%
280
350
—
8"
12'/i6
17l/i
8%
325
400
All designs subject to change without notice. Such change does not imply any obligation on the part of Varec with respect to prior equipment shipments. Installation, mounting
arrangement, and dimensions are preliminary general information not to be used for construction. Certified drawings are available.

-------
GAS PIPING SCHEMATIC
ENCLOSED INSTALLATION
VAREC" FIG. 700-81 EXPLOSION RELIEF VALVES
"VAREC"
WASTE GAS BURNER
FIG. 239
6
V
V
BUILDING
f
lutfK-
r
r—RG
L=#=»
i
'VAREC"
FLAME
CHECK
RG. 52
SLOPE
UARFf"
REMOTE COVER
POSITION INDICATOR
FIG. 102
"VAREC
3 UNIT MANOMETER
FIG. 217
GAS SUPPLY
TO LABORATORY
"VAREC"
PRESSURE REDUCING
REGULATOR-FIG. 387
"VAREC
. PRESSURE RELIEF & FLAME
TRAP ASSEMBLY — FIG. 440
VAREC" FLAME
CHECK FIG. 52
METER
METER
(By others)
v
(By others)

7
GAS SUPPLY TO
SERVICE EQUIPMENT
"VAREC
CHECK VALVE
FIG. 211-92
- TO WASTE GAS BURNER
"VAREC
FLAME TRAP ASSEMBLY
FIG. 450
PILOT SUPPLY TO
WASTE GAS BURNER
GAS SUPPLY FROM
DIGESTER
NOTE: INSTALL DRIP TRAPS AT ALL LOW POINTS
"VAREC"
ORIP TRAP
"VAREC
DRIP TRAP
"VAREC"
SEDIMENT & DRIP TRAP ASSEMBLY
FIG. 233, 218, 246
FIG. 245 OR 246
FIG. 245 OR 246
This schematic is for general guidance purposes
only and is not intended to represent a specific design.
to
<0
09
3
(D
2
5T
3
C0
Fig. 12.13 Waste gas burner
(Courtesy of VAREC)

-------
Sludge Digestion 125
Non-sparking, Gas-tight
VAREC Sampling Hatches are for use on digester
covers or roofs. Insurance requirements are com-
plied with in that this equipment is non-sparking,
self-closing and gas-tight. Materials and construction
is non-corrosive in sludge gas service. Hatches are
designed for taqk working pressures up to 8 oz. per
square inch.

GAGE and THIEF
HOLE COVERS
Figure No. 42-81 incorporates a standard 125 lb.
ANSI flanged base for mounting. It is of extra heavy
construction, basically of aluminum throughout.
Specialty features are included such as a safety foot
pedal for quick opening, a hand wheel which may be
padlocked closed, and a synthetic rubber insert in
cover to insure a gas-tight seal.
Figure No. 48-81 is substantially same as Figure
No. 42-81 in that it includes all the specialty features
and is of same materials of construction. However,
the base is for Standard Pipe Thread mounting.
When ordering, please specify: Figure Number and Size.
For flange drilling other than standard, specify desired
bolt circle, number and size of holes.

Above photo ahow* simplicity
of operation.
Fig. No. 42-81
Flanged Based
Fig. No. 49-81
Screwed Base

-------
126 Treatment Plants
NON-REMOVABLE
HANDWHEEL
0 DIA. B.C.
(G)	NO. HOLES
(H)	DIA. HOLES
FOOT
PEDAL
LUGS FOR PADLOCK
//
rT
OPEN
POSITION
(A) DIA.
(C) DIA.
SYNTHETIC
RUBBER
INSERT
FIGURE NO. 42-81
125* ANSI DRILLING
NON-REMOVABLE
HANDWHEEL
FOOT
PEDAL
LUGS FOR PADLOCK
' OPEN v
POSITION '
SYNTHETIC
RUBBER
INSERT
(A) DIA.
STD. PIPE
THREAD
FIGURE NO. 48-81
SIZE
A
B
c •
D
E
F
G
H
J
K
APPROX. SHIPPING WEIGHTS
STD
. 125-LB
DRILLING
42-81
48-81
2"
2
—
—
—
5'/«
—
—
—
5
3
—
4#
3"
3
4%
71/2
V2
6%
6
4
%
5
5'/4
6#
5#
4"
4
5%
9 ~~1
1/2
8'/8
7'/a
8
%
61/2
6%
8#
8#
6"
6
6%
11
9/l6
9%
9'/2
8
%
8
9'/2
12#
12#
8"
8
6%
131/2
9/l6
10%
11%
8
%
7%
111/2
15#
12#
10"
10
7
16
Vb
12
141/4
12
1
—
—
20#
—
All designs subject to change without notice. Such change does not imply any obligation on the part of Varec with respect to prior equipment shipments. Installation, mounting
arrangement, and dimensions are preliminary general information not to be used for construction. Certified drawings are available.

-------
cool
HOT WATER PUMP
BOILER
DIGESTER GAS
FOR HEATING
HOT WATER
TEMPERATURE GAUGE
RAW SLUDGE
RECIRCULATED
SLUDGE
FROM
HEAT
iv/vre«
HOTsl
HEAT
EXCHANGER
UDG£
RECIRCULATED
SLUDGE
FROM
DIGESTER AS
NEEDED TO
MAINTAIN INLET
TEMPERATURE
TEMPERATURE GAUGE
HEATED SLUDGE
^ TO DIGESTER
Fig. 12.15 Gas fired external hot water heat exchanger

-------
128 Treatment Plants
Fig. 12.16 Hot water heat exchanger
(Permission ol Dorr-Oliver Incorporated)

-------
Sludge Digestion 129
covered in connection with vapor phase cooling of engines.
Careful treatment of the evaporated water to prevent scaling
of the system is necessary so the practice is generally con-
fined to plants with good laboratory control.
QUESTIONS
Write your answers in a notebook and then compare your
answers with those on page 175.
12.13A Why should a digester have a special sampling
well?
12.14A What causes a reduction in the amount of heat
transferred from coils within the digester?
12.15 Digester Mixing
Mixing is very important in a digester. The ability of the mix-
ing equipment to keep the tank completely mixed speeds di-
gestion greatly. Several important objectives are accomplished
in a well-mixed digester.
a.	INOCULATION16 of the raw sludge immediately with mi-
croorganisms.
b.	Prevention of a scum blanket from forming.
c.	Maintenance of homogeneous contents within the tank,
including even distribution of food, organisms, alkalinity,
heat and waste bacterial products.
d.	Utilization of as much of the total contents of the digester
as possible and minimization of the build-up of grit and
inert solids on the bottom.
12.150 Gas Mixing
This type of mixing is the most generally used in recent
years, and various approaches have been patented by manu-
facturers. Gas is pulled from the tank, compressed, and dis-
charged through gas outlets or orifices within the digester, or at
some point several feet below the sludge surface. The gas
rising to the surface through the digesting sludge carries
sludge with it, creating a gas lift with a rolling action of the tank
contents (Fig. 12.3). The gas mixer may be operated on either
a start and stop or a continuous basis, depending upon tank
conditions. The parts required for gas mixing include inlet and
discharge gas lines, a positive displacement compressor, and
a stainless steel gas line header in the digester. The gas
header is equipped with a cross arm to hold a specified
number of gas outlets, and may be mounted in a draft tube.
The gas compressor is sized for the digester and may range
from 30 to 200 cfm (1 to 6 cu m/min) of gas.
Work with "natural gas evolution" mixing at the Los Angeles
County Sanitation District's plants has indicated that loadings
of over 0.4 pounds of volatile solids per cubic foot per day (6.4
kg/cu m/day) were possible, but that if the loading dropped
below 0.3 pounds (4.8 kg/cu m/day) immediate stratification
(layering of contents) occurred. In terms of gas recirculation,
adequate mixing has been calculated from this study to require
about 500 cfm (cubic feet per minute) of gas per 100,000 cubic
feet of tank capacity if released at about a 15-foot (4.5 m)
depth. If released at a 30-foot (9 m) depth, about 250 cfm per
100,000 cubic feet of tank capacity should be satisfactory. If
hydraulic processes are used, either by recirculation or by draft
tubes and propellers, then something like 30 HP per 10,000
cubic feet of tank capacity is required. The latter figure is highly
dependent on the type of mixer and the geometry of the tank.
Maintenance requires that the condensate be drained from
the lines at least twice a day, that the diffusers be cleaned to
prevent high discharge pressures, and that the compressor
unit be properly lubricated and cooled.
QUESTIONS
Write your answers in a notebook and then compare your
answers with those on page 175.
12.15A Why should a digester be kept completely mixed?
12.15B What maintenance is necessary for the proper opera-
tion of a gas-type mixing system in a digester?
12.151 Mechanical Mixing
PROPELLER MIXERS (Figs. 12.17 and 12.18) are found
mainly on fixed cover digesters. Normally two or three of these
units are supported from the roof of the tank with the props
submerged 10 to 12 feet (3 to 3.5 m) in the sludge. An electric
motor drives the propeller stirring the sludge. Digested sludge
normally contains a great deal of grit and debris. As this mate-
rial comes in contact with the mixer shaft and impeller, the
surface of the impeller wears down and/or the shaft becomes
unbalanced and vibrates. When vibrations develop, the mixer
shaft and impeller must be replaced.
DRAFT TUBE PROPELLER MIXERS (Fig. 12.18) are either
single or multiple unit installations. The tubes are of steel and
range from 18 to 24 inches (45 to 60 cm) in diameter. The top
of the draft tube has a rolled lip and is located approximately 18
inches (45 cm) below the normal water level of the tank. The
bottom of the draft tube may be straight or equipped with a 90°
elbow. The 90° elbow type is placed so that the discharge is
along the outside wall of the tank to create a vortex (whirlpool)
action.
The electric motor driven propeller is located about two feet
(0.6 m) below the top of the draft tube. This type unit usually
has reversible motors so the prop may rotate in either direc-
tion. In one direction the contents are pulled from the top of the
digester and forced down the draft tube to be discharged at the
bottom. By operating the motor in the opposite direction, the
digested sludge is pulled from the bottom of the tank and dis-
charged over the top of the draft tube to the surface.
16 Inoculation (in-NOCK-you-LAY-shun). Introduction of a seed culture into a system.

-------
130 Treatment Plants
GEAR REDUCER
MOTOR
COVER

• '• '¦'f o '.V k *-<
% • . " c
Jt
SEAL

MIXER BLADE
/
F/gr. 72.77 Propeller mixer

-------
Sludge Digestion

-------
132 Treatment Plants
If two units are in the same tank, an effective operation for
breaking up a scum blanket is operating one unit in one direc-
tion and the other unit in the opposite direction, thereby creat-
ing a push-pull effect. The draft tube units are subject to shaft
bearing failure due to the abrasiveness of sludge and corrosion
by hydrogen sulfide (H2S) in the digester gas. Maintenance
consists of lubrication and, if belt-driven, adjustment of belt
tension.
A limitation of draft tube type mixers is the potential forma-
tion of a scum blanket. If the water level is maintained at a
constant elevation, a scum blanket forms on the surface. The
scum blanket may be a thick layer and the draft will only pull
liquid sludge from under the blanket, not disturbing it. Lowering
the level of the digester to just three or four inches (7 to 10 cm)
over the top of the draft tube forces the scum to move over and
down the draft tube. This applies mainly to single-direction
mixers.
PUMPS are sometimes used to mix digesters. This method
is common in smaller tanks. When external heat exchangers
are employed, a larger centrifugal pump is used to recirculate
the sludge and discharge it back into the digester through one
or two directional nozzles at the rate of 200 to 1000 gpm (1000
to 5000 cu m/day).
The tank may or may not be equipped with a draft tube such
that the pump suction may be from the top or valved from the
bottom of the digester. Control of scum blankets with this
method of mixing is dependent upon how the operator main-
tains the sludge level and where the pump is pulling from and
discharging to the digester.
Maintenance of the pump requires normal lubrication and a
good pump shaft sealing water system. The digested sludge is
abrasive and pump packing, shafts, wearing rings, and impel-
lers are rapidly worn. Another problem associated with pump
mixing is the clogging of the pump impeller with rags, rubber
goods, and plastic material. A pump may run for days not
pumping due to clogging because the operator was not check-
ing the equipment for proper operation.
Pressure gages should be installed on the pump suction and
discharged pipes. When a gage reading different than normal
occurs, the operator has an indication that some condition has
changed that requires checking.
QUESTIONS
Write your answers in a notebook and then compare your
answers with those on page 175.
12.15C How would you break up a scum blanket in a digester
with two or more draft tube propeller mixers?
12.15D Why should pressure gages be installed on mixing
pump suction and discharge lines?
12.16 Floating Cover Digesters
12.160	Purpose of Floating Covers
Floating covers on anaerobic digesters provide a flexible
space for digester gas storage. A properly operated floating
cover can effectively control the scum blanket in a digester. A
floating cover can keep the scum blanket submerged in the
digesting sludge. Submerged scum blankets are wet and
easier to digest than a dry scum blanket floating on the surface
of digesting sludge.
Explosive gas-air mixtures caused by too rapid withdrawal of
digested sludge or supernatant, are less apt to develop in
anaerobic digesters with floating covers than in digesters with
fixed covers. If sludge or supernatant withdrawal is too rapid,
fixed covers may suffer structural damage due to the develop-
ment of negative pressures.
12.161	Types of Floating Covers
Digester floating covers may be called flat, dome, gas
holder, convex, or wigwam. These names describe the shape
of the inside bottom of the floating cover. Otherwise they are
essentially all the same.
12.162	Parts of Floating Covers (Fig. 12.19)
CORBELS are spaced about 10 feet (3 m) apart on the
inside of the digester wall. They stick out from the wall and
provide support for the floating cover at its lowest position. A
floating cover resting on the corbels can drop no lower. Cor-
bels support the floating cover when the digester is emptied for
maintenance and cleaning. They are usually placed from 10 to
16 feet (3 to 5 m) from the top of the digester wall. This location
permits the floating cover to move from 6 to 10 feet (2 to 3 m)
depending on the design of the digester.
ROLLER GUIDES are located on the inner wall of the diges-
ter. Roller guides are usually made of channel steel and at-
tached vertically to the wall of the digester. Rollers are at-
tached to the outer edge of the floating cover at equal dis-
tances to prevent the cover from scraping the sidewall or rotat-
ing in the tank. Also this keeps the cover floating on top of the
sludge.
BALLAST BLOCKS are large concrete blocks positioned
along the outside top edge of the floating cover to provide
stability and the proper cover buoyancy on top of the digesting
sludge and gas. Some covers have a thin layer (3 to 6 inches
or 7 to 15 cm) of concrete on the cover surface to reduce the
number of ballast blocks.
ANNULAR SPACE is the space full of digesting sludge be-
tween the floating cover and digester side wall. The annular
space provides the digester water seal until the digester con-
tents are lowered below the corbels. If the digester contents
drop below the corbels, the water seal is broken and air can
enter the digester through the space (annular space) between
the outside edge of the floating cover and the digester wall.
WHEN AIR ENTERS THE DIGESTER AN EXPLOSIVE AT-
MOSPHERE DEVELOPS. Extreme caution must be exercised
to prevent an explosion whenever an anaerobic digester is
being emptied or dewatered for maintenance or cleaning.
FLOTATION CHAMBER is used to prevent the cover from
sinking into the digesting sludge and resting submerged on the
corbels. Flotation chambers are located in the roof of the
cover. Digester covers have sunk as a result of leaks in the
bottom of the flotation chamber, cracks on the surface or roof
which allows rainfall to enter the chamber, or of an absent-
minded person leaving an access hatch open. Flotation cham-
bers should be inspected frequently for leaks from rain or

-------
Sludge Digestion 133
180
-ROLLERS AND ROLLER GUIDES
&xv	\	\ \ t ! '
X^\ \ > i / /^x /  s\/x\	! r12 ,N- gas bonnet/ <&
.i ' 2AT 180°f' 'X ^
' / \''
HATCHES

-fl
^ ^ . 30 IN. MANHOLE •
" $\\\|>
6 IN. PRESSURE RELIEF
AND VACUUM BREAKER $--¦ ^
WITH FLAME ARRESTER
f-1	_
' '9>
%
V---I-
SAMPLE OUTLET 1 D
/ / £3/ "t-» Ca
8 IN. SLUDGEs"*® / / |!\ \ \	,
-	...... _ '	y ' I ! 1 v vei i inoe uivcd	fN^J
\
.SAMPLE \ / /
/*\ /
Ci X \ ~ / >. /
X / ' -i-*
v- - V / / / / 7
COVER POSITION TRANSMITTER
PRESSURE RELIEF AND VACUUM. PLAN
BREAKER WITH FLAME ARRESTER
SLUDGE GAS PIPE
.. \Js&
ROLLER GUIDE
TOP ROLLER
BOTTOM
ROLLER
BALLAST BLOCKS
30 IN. MANHOLE
ACCESS
BALLAST BLOCK
ROOF
FLOATATION
CHAMBER
ANNULAR SPACE'
SIDE SKIRT
CORBEL
SLUDGE
SAMPLE

HATCH WITH
COVER-^
SECTION
8 IN. BALL JOINT
SLUDGE MIXER
DRIVE
B	B

0
CORBELS
B> IB
ROLLER
BALLAST
BLOCK
FLOATING COVER
AT LOW LEVEL
DRAFT TUBE
FLOATATION CHAMBER
ILLUSTRATIVE SECTION
Fig. 12.19 Digester Floating Cover

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134 Treatment Plants
washdown water. Also look for signs of corrosion on steel or
other metal parts that could develop into leaks.
Before entering the flotation chamber in a floating cover di-
gester, treat the chamber like any other enclosed space. Use
the proper instruments to test the atmosphere for explosive
conditions, sufficient oxygen (at least 19.5 percent oxygen),
and toxic gases (hydrogen sulfide).
Many flotation chambers have sumps to aid in removing any
rain water or hose down water that enters the chamber. Small
hand pumps or portable submersible pumps are used to empty
the sump. If a cover leaks in one quadrant or section, it may tilt
the cover. A tipped cover either jams at an angle in the tank or
sinks to the corbels. Under these conditions the cover must be
unstuck by either pumping in or withdrawing sludge from the
digester until the cover is in a normal position. If the cover has
sunk to the corbels, the digester contents must be lowered to
the level of the bottom of the flotation chamber, the flotation
chamber pumped out, and the cover restored to service.
ACCESS HATCHES are usually installed on opposite sides
of the floating cover. Smaller covers have two hatches and
larger covers have four hatches or one in each quarter (quad-
rant) of the cover. They provide for cover access and mainte-
nance.
SKIRTS are found on most floating covers. The skirts are
approximately 18 to 24 inches (45 to 60 cm) wide, go around
the outside of the cover and extend into the digester parallel to
the digester walls. Skirts are used to prevent foaming in the
annular space. Foaming can get as high as two to four feet (0.6
to 1.2 m) above the top of a floating cover. Foaming may be
caused by excessive methane gas production or high-energy
digester mixing. Slots must be cut in the skirts to allow the main
structural components of the floating covers to rest on the
corbels rather than the bottom of the skirt resting on the cor-
bels.
COVER INDICATORS inform the operator by a glance at a
dial of the location of the cover in relationship to the amount of
cover travel. If the floating cover can move a distance of 8 feet
(2.4 m) and the dial reads from 0 to 8, then a dial reading of 2
indicates that the cover is 2 feet (0.6 m) from the top. If the
indicator goes past the zero mark, sludge could flow over the
digester walls or there could be structural damage to the cover
or the digester. Cover indicators may be equipped with an
alarm to warn of high or low cover positions.
GAS PIPING consists of flexible hoses (usually rubber) con-
necting pipes on the digester cover to pipes on the digester
wall. Flexible hoses allow digester gas to be removed from the
digester regardless of the level of the cover. Hoses and con-
nections must be inspected monthly for wear, deterioration,
cracks and leaks.
ACCESS LADDERS provide the operator with convenient
access to the roof of the cover regardless of the level or posi-
tion of the floating cover.
Floating cover digesters are equipped with other standard
components found on fixed cover digesters such as sample
holes (thief holes), supernatant withdrawal tubes, gas domes
and mixing equipment (propeller or gas mixers). Safety de-
vices include pressure and vacuum relief valves, flame arres-
ters, sediment traps and isolation valves on sludge and gas
lines.
12.163 Safety
Never allow the floating cover to be raised above the
maximum level because sludge could flow over the digester
walls or the rollers could leave the roller guides. Do not permit
the level of digesting sludge to drop so low that the cover rests
on the corbels and the water seal is broken, except when
cleaning the digester. If the water seal breaks and air enters
the digester, AN EXPLOSIVE ATMOSPHERE EXISTS IN THE
DIGESTER. Inspect the cover frequently (daily) to prevent the
cover from becoming crooked, tipped, stuck or jammed. Care-
fully control digester sludge feed and withdrawal rates. An ad-
ditional inspection of the cover every time the level of the di-
gester contents is changed is a good idea.
QUESTIONS
Write your answers in a notebook and then compare your
answers with those on page 175.
12.16A What is the purpose of floating covers on anaerobic
sludge digesters?
12.16B Why are explosive conditions less apt to develop in
an anaerobic digester with floating covers?
12.16C What is the annular space in the digester?
12.16D What kinds of hazardous atmospheric conditions
could be encountered inside the flotation chamber of
a floating cover digester?
12.16E What could happen if the floating cover rises too high
or drops too low?
END OF LESSON 2 of 6 LESSONS
on
SLUDGE DIGESTION AND SOLIDS HANDLING
Please answer the discussion and review questions before
continuing with Lesson 3.

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DISCUSSION AND REVIEW QUESTIONS
Chapter 12. SLUDGE DIGESTION AND SOLIDS HANDLING
Sludge Digestion 135
Write the answers to these questions before continuing with
Lesson 3. The question numbering continues from Lesson 1.
5.	Why is digester gas considered dangerous?
6.	What two purposes are served by the digester gas sys-
tem?
7.	Under what kind of circumstances will the pressure relief
valve and vacuum relief valve operate?
8.	Where should flame arresters be installed in the digester
gas system?
9.	How would you test for gas leaks around a flame arrester
after it has been serviced?
10.	Why must drip and condensate traps be drained regu-
larly?
11.	What means are used to mix the contents of digesters?
CHAPTER 12. SLUDGE DIGESTION AND SOLIDS HANDLING
(Lesson 3 of 6 Lessons)
12.2 OPERATION OF ANAEROBIC DIGESTERS
A digester can be compared with your own body. Both re-
quire food; but if fed too much, both become upset. Excess
acid will upset both. Both like to be warm, with a body tempera-
ture of 98.6°F (37°C) near optimum. Both have digestive pro-
cesses that are similar. Both discharge liquid and solid waste.
Both utilize food for cell reproduction and energy. If something
causes upsets in a digester, just think how you would react if it
happened to you and recall what would be the proper remedy.
The remedies for curing upset digesters will be discussed
throughout this chapter.
c
12.20 Raw Sludge, Scum, Waste Activated Sludge
Raw sludge is normally composed of solids settled and re-
moved from the primary clarifiers. Raw sludge contains car-
bohydrates, proteins, and fats, plus organic and inorganic
chemicals that are added by domestic and industrial uses of
water.
Solids are composed of organic (volatile) and inorganic ma-
terial with the volatile content running from about 60 to 80
percent of the total, by weight. Some plants do not have grit
removal equipment, so the bulk of the inert (inorganic) material
such as sand, eggshells, and other debris will end up on the
bottom of the digester occupying active digestion space. The
rate of debris accumulation is predictable so that the amount is
a function of the period of time between digester cleanings.
Where cleaning has been neglected, a substantial portion of
the active volume of the digester becomes filled with inert de-
bris. Scum-forming products, such as kitchen grease, soaps,
oils, cellulose, plastics, and other floatable debris, are gener-
ally all organic in nature but may create problems if the scum
blanket in the digester is not controlled. Control is provided by
adequate mixing and heat.
Several products end up in the digester that are not desir-
able because the bacteria cannot effectively utilize or digest
them, and they cannot be readily removed by the normal pro-
cess. These products include:
1.	petroleum products and mineral oils
2.	rubber goods
3.	plastics (back sheets to diapers)
4.	filter tips from cigarettes
5.	hair
6.	grit (sand and other inorganics)
Consequently, these items tend to accumulate in the diges-
ter and, without adequate mixing, may form a hard, floating
mat and a substantial bottom deposit. On the other hand, a
well-mixed tank may also present operational problems. For
example, the material shredded by a comminuter or barminu-

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136 Treatment Plants
ter may become balled together by the mixing action and plug
the digester supernatant lines.
Scum from the primary clarifiers is comprised mainly of
grease and other floatable material. It may be collected and
held in a scum box and then pumped to the digester once a
day, or it may be added continuously or at a frequency neces-
sary to maintain the proper removal of scum from the raw
wastewater flow. Many operators prefer not to pump scum to
the digesters, but to dispose of it by burning or burial. Scum
may also refer to the floating and gas-buoyed material found
on the surface of poorly mixed digesters. This material may
contain much cellulose, rubber particles, mineral oil, plastic,
and other debris. It may become 5 to 15 feet (2 to 5 m) thick in
a digester, but should not occur in a properly operating diges-
ter. A thick scum layer will reduce the active digestion capacity
of a digester.
Waste activated sludge is the sludge intentionally removed
from the activated sludge process and is comprised almost
entirely of the microorganisms from the activated sludge aera-
tion tanks. The volatile solids content of this material typically
ranges from 75 to 85 percent. The density of the sludge will
depend upon whether it is taken directly from the aeration tank,
the return sludge line from the secondary clarifier, or if it is
additionally thickened, whether by gravity, dissolved air flota-
tion or centrifugation. Under these different circumstances the
solids concentrations can vary from 2000 mgIL if taken from
the aeration tank to 60,000 mgIL if thickened by a centrifuge.
The waste activated sludge can be combined with the raw
sludge and this mixture digested, or the waste activated sludge
can be digested separately. In either case it must be recog-
nized that the activated sludge will not be destroyed in the
digester to the same extent as the raw sludge. This occurs
because of the complex organic nature of the microorganisms
and their resistance to digestion.
12.21 Starting a Digester
When wastewater solids are first added to a new digester,
naturally occurring bacteria attack the most easily digestible
food available, such as sugar, starches, and soluble nitrogen.
The anaerobic acid producers change these foods into organic
acids, alcohols, and carbon dioxide, along with some hydrogen
sulfide. The pH of the sludge drops from 7.0 to about 6.0 or
lower. An ACID REGRESSION STAGE17 then starts and lasts
as long as six to eight weeks. During this time ammonia and
bicarbonate compounds are formed, and the pH gradually in-
creases to around 6.8 again, establishing an environment for
the methane fermentation or alkaline fermentation phase. Or-
ganic acids are available to feed the methane fermenters.
Larger quantities of methane gas are produced as well as
carbon dioxide, and the pH increases to 7.0 to 7.2. Once al-
kaline fermentation is well established, strive to keep the di-
gesting sludge in the 7.0 to 7.2 pH range.
If too much raw sludge is added to the digester, the acid
fermenters will predominate, driving the pH down and creating
an undesirable condition for the methane fermenters. The di-
gester will go sour or acid again. When a digester recovers
from a sour or acid condition, the breakdown of the volatile
acids and formation of methane and carbon dioxide is usually
very rapid. The digester may then foam or froth, forcing sludge
solids through water seals and gas lines and causing a fairly
serious operational problem. A sour digester usually requires
30 to 60 days to recover.
As noted at the beginning of this section, the first group of
organisms must do its part before food is available to the next
group. Once the balance is upset, so is the food cycle to the
next group. When the tank reaches the methane fermentation
phase, there is sufficient alkaline material to buffer the acid
stage and maintain the process. Operational actions such as
poor mixing, addition of excess food, excess water supplied to
dilute the alkaline buffer, over-drawing digested sludge, or im-
proper temperature changes can cause souring again.
The simplest way to start a digester is with seed sludge
(actively digesting material) from another digester. The amount
of seed to use is dependent upon facters such as mixing pro-
cesses, digester sizes, and sludge characteristics, but
amounts between 10 and 50 percent of the digester capacity
have been used.
EXAMPLE (seed volume based on tank capacity):
Calculate the volume of seed sludge needed for a 40-foot
diameter digester with a normal water depth of 20 feet, if the
seed required is 25 percent of the tank volume. Most digesters
have sloping bottoms, but assume the normal side wall water
depth represents the average digester depth:
Tank Diameter, D = 40 feet
Depth, H	=20 feet
1	= .785
Tank Volume,
cu ft
40
= Area, sq ft x Depth, ft x4(J
1600
Tank Volume,
gal
= _ D x H
4
= 0.785 (40 ft)2 x 20 ft
= 25,120 cu ft
= (25,120 cu ft) (7.5 gal/cu ft)
= 188,400 gal
1600
x20
32000
0.785
32000
1570000
2355
25120.000
25120
7.5
125600
175840
188400.0
Seed required assumed to be 25 percent or '/4 of the diges-
ter tank volume:
Seed Volume,
_ Tank Volume, gal
4
= 16e'4°°gal
4
= 47,100 gal (180 cu m)
47100
4)188400
!£.
28
28
4
4
Therefore, 47,100 gallons (180 cu m) of seed sludge would
be needed. If seed sludge is not available, the tank may be
started by filling the digester with raw wastewater and heating
the tank to 85-95°F (30-35°C) with natural gas or other fuel.
Allow the bacteria to take the natural course of decomposition
as earlier described. The time required for a start of this nature
ranges from 45 to 180 days.
Rather than estimate the volume of seed sludge on the basis
of digester capacity, a better approach is to determine the
volume of seed necessary to maintain digestion under the ex-
17 Acid Regression Stage. A time period when the production of volatile acids is reduced. During this stage of digestion ammonia com-
pounds form and cause the pH to increase.

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Sludge Digestion 137
pected initial loading. To use this approach, allow 0.03 to 0.10
pound of new volatile solids to be added per day per pound of
volatile solids under digestion (0.3 to 0.1 kg added per day per
kg under digestion).
EXAMPLE (seed volume based on raw sludge to be added):
Initially a new plant expects to pump 500 gallons of raw
sludge per day to the digester. The raw sludge is estimated to
contain 6 percent solids with a volatile content of 68 percent.
Estimate the pounds of volatile solids needed by the digester
and the gallons of seed sludge, assuming the seed sludge
contains 10 percent solids with 50 percent volatile solids and
weighs nine pounds per gallon. (Digested sludge containing 10
percent solids weighs more than water [8.34 lb/gal] without
any solids.)
Find pounds of volatile matter pumped to digester per day.
Volatile
Matter
Pumped, = (Vol. of SI, gpd) (Solids, %) (Volatile, %) (8.34 lb/gal)
lbs/day = (500 gal/day) (0.06) (0.68) (8.34 lb/gal)
= 170 lbs/day
Select a digester loading between 0.03 and 0.10 pounds of
new volatile solids added per day per pound of volatile solids in
digester. Try 0.05 lb VM per day per pound under digestion for
a starting loading.
Find pounds of seed volatile matter needed.
0.05 lb VM added/day = 170 lb VM added/day
1 lb VM digester	Seed, lb VM
Seed, lb VM	= (170 lb VM added/day) |b VM
0.05 lb VM added/day
= 3400 lbs VM
Find gallons of seed sludge needed.
Seed Sludge, gal =	Seed, lb VM	
(9 lb/gal) (Solids, %) (VM, %)
= 	3400 lb VM	
(9 lb/gal) (0.10) (0.50 VM)
= 7560 gal (29 cu m)
To start a digester, add the necessary seed sludge and fill
the remainder of the tank with raw sludge and wastewater.
Some operators do not completely fill a digester during start-up
but this practice is not recommended. The reason is that the
tank may develop an explosive mixture of gases if air is al-
lowed into the partially-filled digester.
During the start-up of a digester, once production of a good,
burnable gas is obtained the raw sludge feed rate can be
gradually increased until the system is handling the total load.
QUESTIONS
Write your answers in a notebook and then compare your
answers with those on pages 175 and 176.
12.20A What is (1) raw sludge? (2) scum? (3) waste acti-
vated sludge?
12.21 A What happens if you add too much raw sludge to the
digester?
12.21 B What causes a digester to foam and froth?
12.21C Calculate the recommended volume of seed sludge
to start a digester 50 feet in diameter and 25 feet
deep (average). Assume 700 gallons per day of raw
sludge will be added, containing 6.5% solids and
70% volatile matter. Assume seed sludge contains
10% solids with 50% volatile solids and weighs nine
pounds per gallon. Use a digester loading of 0.05 lb
VM added per day per lb VM under digestion.
12.21 D Why is it dangerous to start a digester when it is only
partially full?
12.21E How could you determine when a new digester is
ready for the raw sludge feed rate to be gradually
increased to the full plant load?
12.22 Feeding
Food for the bacteria in the digester is the raw sludge from
the primary clarifier and/or waste activated sludge or trickling
filter "humus" from the secondary clarifiers. Make every effort
to pump as thick a sludge to the digester as possible. This may
be accomplished by holding a blanket of sludge as long as
possible in the primary clarifier, long enough to allow sludge
concentration, but not long enough for sludge to start gassing
or rising. In some plants concentration is accomplished in sep-
arate sludge-thickening or flotation tanks.
Better operational performance occurs when the digester is
fed several times a day, rather than once a day because you
are avoiding temporary overloads on the digester and you are
using your available space more effectively. Several pumpings
a day not only helps the digestion process, but maintains better
conditions in the clarifiers, permits thicker sludge pumping, and
prevents CONING18 in the primary clarifier hopper. On fixed
cover digesters frequent feeding spreads the return of digester
supernatant over the entire day instead of a return in one slug
with possible upset of the secondary treatment system. Sludge
is usually concentrated by holding a thick blanket on the bot-
tom of the clarifier; but if sludge sets for a prolonged period,
lowest layers may stick to the bottom and will no longer flow
with the liquid. When pumping is attempted, liquid flows but
solids remain in the hopper in a cone around the outlet.
Never pump thin sludge or water to a digester. A sludge is
considered thin if it contains less than 5 percent solids (too
much water). Reasons for not pumping a thin sludge include:
1.	Excess water requires more heat than may be available,
2.	Excess water reduces holding time of the sludge in the
digester, and
3.	Excess water forces seed and alkalinity from the digester,
jeopardizing the system due to insufficient BUFFER CA-
PACITY19 for the acids produced by digestion of the raw
sludge.
Sludge concentrations above about 10 to 12 percent solids
will usually not digest well in conventional digestion tanks since
18	Coning (CONE-ing). Development of a cone-shaped flow of liquid, like a whirlpool, through sludge. This can occur in a sludge hopper
during sludge withdrawal when the sludge becomes too thick. Part of the sludge remains in place while liquid rather than sludge flows out of
the hopper. Also called "coring."
19	Buffer Capacity. A measure of the capacity of a solution or liquid to neutralize acids or bases. This is a measure of the capacity of water or
wastewater for offering a resistance to changes in the pH. Buffer capacity is measured by titration with standard alkali and acid until the pH
reaches some reference or end point (a pH of 4.5 or 8.5). The higher the volume (ml) of known reagent requirements, the higher the buffer
capacity.

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138 Treatment Plants
adequate mixing cannot be obtained. This, in turn, leads to
improper distribution of food, seed, heat and metabolic prod-
ucts so that souring and a STUCK20 digester results. However,
most plants have difficulty in obtaining a raw sludge of 8 per-
cent solids. Where a trickling filter or activated sludge process
is used as the secondary system, sludges may have a solids
range from 1 to 3 percent. If additional thickening of waste
activated sludge is used, such as dissolved air flotation or
centrifuges, the solids content may range from 4.5 to 6 percent
solids.
Feeding a digester must be regulated on the basis of labora-
tory test results in order to insure that the volatile acid/alkalinity
relationship does not start to increase and become too high.
See Section 12.3B, "Volatile Acid/Alkalinity Relationship."
QUESTIONS
Write your answers in a notebook and then compare your
answers with those on page 176.
12.22k How would you attempt to pump as thick a sludge as
possible to a digester?
12.22B Why should sludge be pumped occasionally through-
out the day rather than as one slug each day?
12.22C Why should the pumping of thin sludge be avoided?
12.23 Neutralizing a Sour Digester
The recovery of a sour digester can be accelerated by neu-
tralizing the acids with a caustic material such as soda ash,
lime, or ammonia, or by transferring alkalinity in the form of
digested sludge from the secondary digester. Such neutraliza-
tion increases the pH to a level suitable for growth of the
methane fermenters and provides buffering material which will
help maintain the required volatile acid/alkalinity relationship
and pH. When ammonia is added to a digester, an added load
is eventually placed on the receiving waters. The application of
lime will increase the solids handling problems. Soda ash is
more expensive than lime, but doesn't add as much to the
solids deposits. Transferring secondary digester sludge has
the advantage of not adding anything extra to the system that
was not there at an earlier time and, if used properly, will
reduce both the effluent load and the solids handling problem.
If digestion capacity and available recovery time are great
enough, it is probably preferable to simply reduce loading while
heating and mixing so that natural recovery occurs. However,
there are often conditions in which such neutralization is nec-
essary.
When neutralizing a digester, the prescribed dose must be
carefully calculated. Too little will be ineffective, and too much
is both toxic and wasteful. In considering dosage with lime, the
small plant without laboratory facilities could use as a rough
guide a dosage of about one pound of lime added for every
1000 gallons of sludge to be treated. Thus, a 188,000-gallon
digester full of sludge would receive 188 pounds of lime. A
more accurate method is to add sufficient lime to neutralize
100 percent of the volatile acids in the digester liquor. (See
Volatile Acids Test in Chapter 16, "Laboratory Procedures and
Chemistry.")
You must realize that neutralizing a sour digester will only
bring the pH to a suitable level, it will not cure the cause of the
upset.
EXAMPLE:
Volatile acids in digester sludge = 2300 mg/L. We should
add lime equivalent to 2300 mg/L.
Lime
Required, = Volatile Acids, mg/L x Tank Volume, MG x 8.34 lbs/gal
lbs	= 2300 mg/L x 0.188 MG x 8.34 lbs/gal
= 2300 x 1.57 lbs
= 3611 lbs
Assume the acids are reported as acetic acid and the lime is
calcium hydroxide (Ca (OH)2). Another procedure would be to
take a sludge sample of known volume into the lab and add
lime until the desired pH is obtained. Use this result to deter-
mine the amount of lime to be added to the digester.
The lime must be mixed into a solution before being added
to the digester because dry lime would settle to the bottom in
lumps which are not only ineffective but take up digester ca-
pacity and are difficult to remove when cleaning the digester.
Use all of the mixing energy available while liming and thereaf-
ter in digester mixing. The easiest application point is through
the scum box if one is available. Add small quantities of lime
daily until the pH and volatile acid/alkalinity relationship (Sec-
tion 12.3B) of the tank are restored to desired levels and gas
production is normal. In any case, use lime only if recovery by
natural methods cannot be accomplished within the time avail-
able.
Caution must be taken to add lime only when the pH drops
below 6.5. Even then only enough lime should be added to
raise the pH to the range of 6.7 to 6.8. Upon addition of the lime
carefully watch the pH. As soon as it drops below 6.4 to 6.5,
add more lime to bring it back to the pH range of 6.7 to 6.8. Use
this procedure, combined with good digester mixing, to prevent
the formation of a vacuum in the digester. Otherwise, the lime
combines with carbon dioxide in the digester gas and forms a
dangerous vacuum in the digester.
Although it is seldom used because of higher costs, sodium
bicarbonate is a good substitute for lime. Besides requiring
smaller quantitites, use of sodium bicarbonate presents none
of the problems described in this section associated with lime.
QUESTIONS
Write your answers in a notebook and then compare your
answers with those on page 176.
12.23A Why is lime added to a digester?
12.23B How much lime should be added to a 100,000-gallon
digester, using the "rough guide" dosage in the pre-
vious section?
12.23C Why should lime be added in solution to the digester
rather than in dry form?
12.23D For how long a time should you add lime to a diges-
ter?
20 Stuck. Not working. A stuck digester does not decompose organic matter properly. The digester is characterized by low gas production,
high volatile acid/alkalinity relationship, and poor liquid-solids separation. A digester in a stuck condition is sometimes called a "sour" or
"upset" digester.

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Sludge Digestion 139
12.24	Enzymes21
In recent years several products containing "commercial"
enzymes or other biocatalysts (BUY-o-CAT-a-lists) have been
marketed for starting digesters, controlling scum, or simply to
maintain operation. Such biocatalysts or enzymes have rarely
been shown to be effective in controlled tests and could, in
fact, cause as much harm as good. A biological system such
as found in the digesters develops a balanced enzyme and
biocatalyst system for the conditions under which it is operat-
ing. The quantities of natural enzymes developed within the
digesting sludge are many, many times greater than any
amount you could either add or afford to purchase.
12.25	Foaming
Large amounts of foam may be generated during start-up by
the almost explosive generation of gas during the time of acid
recovery. Foaming is the result of active gas production while
solids separation has not progressed far enough (insufficient
digestion). It is encouraged during start-up by overfeeding.
Foaming can be prevented by adequate mixing of the digester
contents before foaming starts.
Bacteria can go to work very quickly when they have the
proper environment. Almost overnight they can generate
enough gas to create a terrible mess of black foam and sludge.
The foam not only plugs gas piping systems, but can exert
excess pressures on digester covers, cause odor problems,
and ruin paint jobs on tanks and buildings.
To clean up the mess, first drop the level of the digester a
couple of feet by withdrawing some supernatant. Next, cut off
the gas system and flush it with water. Then hose the outside
of the digester off as soon as possible or the paint will be
stained a permanent grey. Drain and refill the water seal to
remove the water fouled by the foaming. Use a strainer-type
skimming device to remove any rubber goods and plastic ma-
terials that have entered the water seal.
To control the foaming, the best method is to stir the tank
gently to release as much of the trapped gas from the foam as
possible. Some operators even stop mechanical mixing
equipment and stir with long, wooden poles. During stirring
with poles, air will get into the digester and create an explosive
condition. This explosive condition will persist until the digest-
ing sludge produces enough gas to carry the oxygen from the
air out of the digester by venting to the atmosphere or by way
of the waste gas burner. Try not to add too much water from
the cleaning hoses as this reduces the temperature and dilutes
the tank, which could create conditions for more foaming later.
Do not feed the tank heavily, preferably not at all, until the
foaming has subsided.
Foaming may occur when a thick sludge blanket is broken
up, temperature changes radically, or the sludge feeding to the
digester is increased. Avoid any conditions that give the acid
formers the opportunity to produce more food than the
methane fermenters can handle, because when the methane
fermenters are ready, they may work too fast.
IF THERE HAD BEEN ADEQUATE MIXING, FOAMING
PROBLEMS WOULD NOT HAVE DEVELOPED. START MIX-
ING FROM BOTTOM TO TOP OF THE TANK BEFORE
FOAMING STARTS, NOT AFTERWARDS.
12.26 Gas Production
When a digester is first started, extremely odorous gases
are produced, including a number of nitrogen and sulfur com-
pounds such as skatole, indole, mercaptans, and hydrogen
sulfide. Many of these are also produced during normal diges-
tion phases, but they are generally so diluted by carbon dioxide
and methane that they are hardly noticeable. Their presence
can be determined by testing if so desired.
During the first phases of digester start-up, most of the gas is
carbon dioxide (C02) and hydrogen sulfide (H2S). This combi-
nation will not burn and therefore is usually vented to the at-
mosphere. In such venting the operator should be aware of the
potential odor problem that can result. When methane fermen-
tation starts and the methane content reaches around 60 per-
cent, the gas will be capable of burning. Methane production
eventually should predominate, generating a gas with 65 to 70
percent methane and 30 to 35 percent C02 by volume. Diges-
ter gas will burn when it contains 56 percent methane, but is
not usable as a fuel until the methane content approaches 62
percent. When the gas produced is burnable, it may be used to
heat the digester as well as for powering engines and for pro-
viding building heating.
QUESTIONS
Write your answers in a notebook and then compare your
answers with those on page 176.
12.24A What is the function of enzymes in digestion?
12.25A How would you attempt to control a foaming diges-
ter?
12.25B What preventive measures would you take to prevent
foaming from recurring?
12.26A Why is the gas initially produced in a digester not
burnable?
12.27 Supernatant and Solids
Plants constructed today are typically equipped with two
separate digestion tanks (Fig. 12.20) or one tank with two di-
vided sections. One tank is called the primary digester and is
used for heating, mixing, and breakdown of raw sludge. The
second tank, or secondary digester, is used as a holding tank
for separation of the solids from the liquor. To accomplish such
separation, the secondary tank must be quiescent (qui-ES-
sent) (without mixing).
Most of the sludge stabilization work is accomplished in the
primary digester, and 90 percent of the gas production occurs
there. The primary tank must be very thoroughly mixed, but it is
undesirable to return the digested mixture to the plant as a
supernatant. Therefore, when raw sludge is pumped to the
primary digester, an equal volume is transferred to the secon-
dary digester, and settled supernatant from the secondary di-
gester is returned to the plant.
In the primary digester the binding property of the sludge is
broken, allowing the water to be released. In the secondary
digester the digested sludge is allowed to settle and compact,
21 Enzymes (EN-zimes). Enzymes are organic substances produced by living organisms and speed up chemical changes.

-------
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Sludge Digestion 141
with some digestion continuing. When the solids settle they
leave a light amber colored liquor zone between the top of the
settled sludge and the surface of the digester. By adjusting or
selecting the supernatant tube, the liquor with the least solids
is returned to the plant.
The settled solids in the secondary digester are allowed to
compact so that a minimal amount of water will be handled in
the sludge dewatering system. These solids are excellent seed
or buffer sludge in case the primary digester becomes upset. A
reserve of 30 to 100 thousand gallons (100 to 400 cu m) or 25
percent of the volume undergoing active digestion should al-
ways be held in the secondary digester. This represents a
natural enzyme reserve and may save the system during a
shock load. Primary and secondary sludge digesters should be
operated as a complement to each other. If you need more
seed or buffering capacity in the primary digester, it should be
taken from the secondary digester.
The secondary tanks should be mixed frequently, preferably
after sludge has been withdrawn and when supernatant will not
be returned to the plant. Usually secondary digesters are pro-
vided with mixers or recirculating pumps, preferably arranged
for vertical mixing. This periodic mixing prevents coning of sol-
ids on the bottom of the tank and the formation of a scum
blanket on the top. Mixing also helps the release of slowly
produced gas that may float solids or scum.
If your plant has only one digester, stop mixing for one day
before withdrawing digested sludge to drying beds.
Although this section and other textbooks describe super-
natant as a clear liquid with an amber color, this condition is
rarely observed. In some plants, the secondary digester can sit
for two days without mixing and no significant difference can
be observed between the digested sludge on the bottom and
the digested sludge on the top. In other words, the liquid did
not separate from the digested sludge. This occurrence is not
uncommon, especially when treating waste activated sludge.
For this reason, the trend appears to be away from the use of
secondary digesters for liquid-solids separation. Chapter 22
describes liquid-solids separation processes, including vac-
uum filters, pressure filters, centrifuges, dryers and multiple
hearth furnaces.
12.28 Rate of Sludge Withdrawal
The withdrawal rate of sludge from either digester should be
no faster than a rate at which the gas production from the
system is able to maintain a positive pressure in the digester
(at least two inches (5 cm) of water column).
WARNING : If the draw-off rate is too fast, the gas pressure
drops due to volume expansion. If continued, a negative
pressure develops on the system (vacuum). This may
create an explosive hazard by drawing air into the digester.
If the primary digester has a floating cover, the sludge may
be drawn down to where the cover rests on the corbels
without danger of losing gas pressure.
Some operators prefer to pump raw sludge or wastewater to
a digester during digested sludge draw-off to maintain a posi-
tive pressure. If gas storage lines permit, gas should be re-
turned to the digester to maintain pressure in the digester.
QUESTIONS
Write your answers in a notebook and then compare your
answers with those on page 176.
12.27A What is the purpose of the secondary digester?
12.27B When raw sludge is pumped to the primary digester,
what happens in the secondary digester?
12.27C How is the level of supernatant withdrawal selected?
12.28A How would you determine the rate of sludge with-
drawal?
END OF LESSON 3 OF 6 LESSONS
on
SLUDGE DIGESTION AND SOLIDS HANDLING
Please answer the discussion and review questions before
continuing with Lesson 4.
DISCUSSION AND REVIEW QUESTIONS
Chapter 12. SLUDGE DIGESTION AND SOLIDS HANDLING
(Lesson 3 of 6 Lessons)
Write the answers to these questions in your notebook be-
fore continuing with Lesson 4, The question numbering con-
tinues from Lesson 2.
12.	What kinds of material or products frequently end up in
digesters that are not desirable because bacteria cannot
effectively utilize or digest them?
13.	Why should seed sludge be added to a new digester?
14.	Why should a digester be fed at regular intervals during
the day, rather than once a day?
15.	What are enzymes?
16.	How can an operator attempt to prevent a digester from
starting to foam?
17.	Why should secondary digesters be mixed, if at all?

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142 Treatment Plants
CHAPTER 12. SLUDGE DIGESTION AND SOLIDS HANDLING
(Lesson 4 of 6 Lessons)
12.3 ANAEROBIC DIGESTION CONTROLS AND TEST
INTERPRETATION
lyOTE: See Chapter 16, "Laboratory Procedures and Chemis-
try," for testing procedures.
A.	TEMPERATURE
A thermometer is usually installed in the recirculated sludge
line from the digester to the heat exchanger. This thermometer
will accurately measure the temperature of the digester con-
tents when circulation is from bottom to top. The temperature
from the digester is recorded and should be maintained be-
tween about 95 and 98°F (35 and 37°C) for mesophilic diges-
tion. Never change the temperature more than 1 °F or 0.5°C per
day. Accurate temperature readings also may be taken from
the flowing supernatant tube or from the heat exchanger
sludge inlet line. The same temperature should be maintained
at all levels of the tank.
B.	VOLA TILE ACID I ALKALINITY RELA TIONSHIP
THE VOLATILE ACID/ALKALINITY RELATIONSHIP IS
THE KEY TO SUCCESSFUL DIGESTER OPERATION. As
long as the volatile acids remain low and the alkalinity stays
high, anaerobic sludge digestion will occur in a digester. Each
treatment plant will have its own characteristic ratio for proper
sludge digestion (generally less than 0.1). When the ratio
starts to increase, corrective action must be taken im-
mediately. This is the FIRST WARNING that trouble is starting
in a digester. If corrective action is not taken immediately or is
not effective, eventually the C02 content of the digester gas
will increase, the pH of the sludge in the digester will drop, and
the digester will become sour or upset.
A good procedure is to measure the volatile acid/alkalinity
relationship at least twice a week, plot the volatile acid/
alkalinity relationship against time, and watch for any adverse
trends to develop. Whenever something unusual happens,
such as an increased solids load from increased waste dis-
charges or a storm, the volatile acid/alkalinity relationship
should be watched closely. Chapter 16, "Laboratory Proce-
dures and Chemistry," contains a procedure for measuring
volatile acids by titration which gives satisfactory results for
operational control.
The volatile acid/alkalinity relationship is an indication of the
buffer capacity of the digester contents. A high buffer capacity
is desirable and is achieved by a low ratio which exists when
volatile acids are low and the alkalinity is high (120 mg/L vol-
atile acids/2400 mg/L alkalinity). Excessive feeding of raw
sludge to the digester, removal of digested sludge, or a shock
load such as produced by a storm flushing out the collection
system may unbalance the volatile acid/alkalinity relationship.
A definite problem is developing when the volatile acid/
alkalinity relationship starts increasing. Once the relationship
reaches the vicinity of 0.5/1.0 (1000 mg/L volatile acids/2000
mgIL alkalinity), serious decreases in the alkalinity usually oc-
cur. At a relationship of 0.5/1.0 the concentration of C02 in
digester gas will start to increase. When the relationship
reaches 0.8 or higher, the pH of the digester contents will begin
to drop. When the relationship first starts to increase, ample
warning is given for corrective action to be taken before prob-
lems develop and digester control is lost.
RESPONSE TO AN INCREASE IN VOLATILE ACID/
ALKALINITY RATIO
When the ratio starts to increase, extend mixing time of di-
gester contents, control heat more evenly, and decrease
sludge withdrawal rates. Mixing should be vertical mixing from
the bottom of the tank to the top of any scum blanket. If possi-
ble, some of the concentrated sludge in the secondary digester
should be pumped back to help correct the ratio. In addition,
the primary digester should not be operated as a continuous
overflow unit when raw sludge is added, but it should be drawn
down to provide room for some sludge from the secondary
digester too. During heavy rains when extra solids are flushed
into the plant, it may be necessary to add some digested
sludge to the primary digester. Use the volatile acid/alkalinity
ratio as a guide to determine the amount of digested sludge
that should be returned to the primary digester for control pur-
poses.
C.	DIGESTER GAS (C02 and Gas Production)
This is a useful test to record. The change of C02 in the gas
is an indicator of the condition of the digester. Good digester
gas will have a C02 content of 30 to 35 percent. The volatile
acid/alkalinity relationship will start to increase BEFORE the
carbon dioxide (C02) content begins to climb. If the C02 con-
tent exceeds 42 percent, the digester is considered in poor
condition and the gas is close to the burnable limit (44 to 45
percent C02).
Gas production in a properly operating digester should be
constant if feed is reasonably constant. If the volume produced
gradually starts falling, trouble of some sort is indicated.
D.	pH
pH is normally run on raw sludge, recirculated sludge, and
supernatant. This information is strictly for the record and not
for plant control. The raw sludge, if stale, will be acid and run in
the range of 5.5 to 6.8. Digester liquors should stay around 7.0
or higher. pH is usually the last indicator to change and gives
little warning of approaching trouble. Therefore, pH is the least
desirable control method.
QUESTIONS
Write your answers in a notebook and then compare your
answers with those on pages 176 and 177.
12.3A Where would you obtain the temperature of a diqes-
ter?
12.3B Why is the volatile acid/alkalinity relationship very use-
ful in digester control?
12.3C What should be done when the volatile acid/alkalinity
relationship starts to increase?
12.3D Why is pH a poor indicator of approaching trouble in a
digester?
E.	SOUDS TEST
Samples are collected of the raw sludge, recirculated
sludge, and supernatant. Each sample is tested for TOTAL
SOUDS and VOLATILE SOUDS.

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Sludge Digestion 143
The information from these tests is used to determine the
pounds of solids handled through the system, the digester
loading rates, and the percent of reduction of the organic mat-
ter destroyed by the digester. All of these tests are necessary
for the maintenance of efficient digester operation.
F. VOLUME OF SLUDGE
Volumes of sludge are needed to determine the pounds of
solids handled through the system. In smaller plants which use
a positive displacement pump, the volume of raw sludge is
determined by the volume the pump displaces during each
revolution. For instance, a 10-inch (25 cm) diameter piston
pump with a 3-inch (7.5 cm) stroke will discharge one gallon
per revolution. These pumps are equipped with a counter on
the end of the shaft and are seldom operated faster than 50
GPM.
EXAMPLE
Calculate the volume pumped per stroke (revolution) by a
piston pump with a 10-inch diameter piston and the stroke set
at three inches.
Volume of
Cylinder, = Area, sq ft x Depth, ft
cu ft
.83
.83
0.785 D H
10 in
12 in/ft
3 in
0.833 or 0.83 ft
249
664
= 0.25 ft
12 in/ft
= 0.785 x (0.83 ft)2 x 0.25 ft
= 0.785 x 0.69 ft x 0.25 ft
= 0.785 x 0.17
= 0.133 cu ft
Volume of
Cylinder, = 0.133 cu ft x 7.48 gal/cu ft
.69
.25
345
138
.6889
.785
.17
5495
785
.1725
= 0.995 gals/stroke
= 1.0 gal/stroke (3.8 liters)
(approximately)
.13345
7.48
.133
2244
2244
748
0.99484
This is the maximum volume that can be pumped per stroke
with this unit. Slow or incomplete valve closures are likely to
reduce this amount. You may check it by taking the delivery
volume and dividing it by the number of strokes to fill a drying
bed or tank.
UNITS:
The piston travels the depth of the cylinder each stroke. We
could have written our original equation in volume per stroke
by indicating depth as distance per stroke.
Volume, cu ft/stroke = Area, sq ft x Depth, ft/stroke
Therefore, if the pump counter recorded 2800 revolutions,
ideally the pump handled a total of 2800 gallons for that period
of time, which is normally a 24-hour period.
If a centrifugal pump is provided, it would be necessary to
determine the volume pumped within the system. Thus by de-
termining how long it took to pump one foot of sludge to the
digester, the volume per minute could be determined. The
quantity of sludge pumped per day is an important variable,
and the operator should make a real effort to determine the
quantity. The volume of sludge pumped to the digester should
be approximately the same each day.
QUESTIONS
Write your answers in a notebook and then compare your
answers with those on page 177.
12.3E Why would you run a solids test on digester sludge?
12.3F Calculate the volume of sludge pumped per stroke by
a 12-inch diameter piston pump with the stroke set at
four inches.
12.3G If a piston pump discharges 1.2 gallons per stroke and
the counter indicates 2000 revolutions during a 24-
hour period, estimate how many gallons were pumped
during that day.
12.3H Why would you want to know the volume of sludge
pumped per day?
G. RAW SLUDGE
If the 2800 gallons of raw sludge pumped by the piston pump
contained 6.5 percent total solids and had a volatile content of
68 percent:
1.	How many pounds of dry sludge were handled?
2.	What part is subject to digestion (volatile solids)?
EXAMPLE
Sludge Pumped = 2800 gallons
Solids	= 6.5%
Volatile	= 68%
Dry
Solids, = Gals Pumped x % Solids as decimal x 8.34 lbs water/gal
lbs = 2800 gals x 0.065 x 8.34 lbs/gal
= 182 gals x 8.34 lbs/gal of solids
= 1518 lbs during pumping period
2800
.065
14000
16800
182.000
182 x 8.34 = 1517.88
Volatile
Solids, =% Volatile as decimal x Total Solids, lbs
lbs =0.68 x 1518 lbs
= 1032 lbs of volatile solids during pumping period
H. RECIRCULATED SLUDGE
Laboratory tests indicate that the dry solids in a recirculated
digested sludge sample was 4.5 percent and contained 54.2
percent volatile content. This indicates that the process is re-
ducing the volatile content of the sludge, but the 4.5 percent
solids is lower than that of the raw sludge being pumped to the
digester. The reduction is a result of the conversion of a sub-
stantial portion of the volatile solids in the raw sludge to
methane, carbon dioxide, and water. Therefore, the reduction
in solids comes from some of the solids being converted to gas
and some of the solids being washed out in the supernatant.
The reduction of volatile solids that has occurred in the pri-
mary digester is arrived at mathematically by the following for-
mula:
P =
R - D
. x 100%=
In - Out
. x100%
R - (R x D)	In - (In x Out)
P = Percent Reduction of Volatile Matter
In R = Percent Volatile Matter in Raw Sludge
Out D = Percent Volatile Matter in Digested Sludge
This formula assumes that the digester is completely mixed.

-------
144 Treatment Plants
and that the pounds of fixed solids entering the digester equals
the pounds of fixed solids leaving. If these assumptions do not
apply to the situation, the answer given by the formula may be
in error.
EXAMPLE:
CHECK 2:
In
Out
P
68% Volatile Matter in Raw Sludge
54% Volatile Matter in Digested Sludge
In - Out
.x 100%
In - (In x Out)
0.68 - 0.54
0.68 - (0.68 x 0.54)
. x100%
0.68
-0.54
0.14
0.14
0.68 - 0.37
. x 100%
0.54
0.68
432
324
0.3672
or 0.37
0.14
x 100%
0.31
0.45 x 100%
45%
0.68
•0.37
0.31
•3,1f
45
00
1 60
1 55
What is actually happening in the calculation of the percent
reduction of volatile matter may be visualized by the following
example. Start with 100,000 pounds of raw sludge solids con-
sisting of 75 percent volatile (organic) solids and 25 percent
fixed (inorganic) solids. After digestion, 50,000 pounds of vol-
atile matter has been converted to methane, carbon dioxide,
and supernatant water containing recycle solids, nitrogen, and
a COO. The remaining digested sludge consists of 25,000
pounds volatile matter and 25,000 pounds of fixed solids.
BEFORE DIGESTION
100,000 LBS RAW SLUDGE
AFTER DIGESTION
75*
VOLATILE
25%
FIXED
75.000 lbs
DIGESTION CONVERTS
VOCATILES TO
CH4_ COj, AND H20
-+¦
REMAINING
DIGESTED SLUDGE
25,000 lbs
25,000 IDs
50,000 lbs
502
VOLATILE
FIXED

COMBINED WITH SUPERNATANT WATER
CONTAINING RECYCLE SOLIDS,
NITROGEN AND A COO
CHECK 1:
Percent Reduction
of Volatile Matter
(Reduction of Vol. Solids, lbs) x 100%
Starting Amt of Vol. Solids, lbs
(75,000 lbs • 25,000 lbs) x 100%
75,000 lbs
50,000 x 100%
75,000
ee.7%
ln ' °ut x 100%
In - (In x Out)
0.75 - 0.50
x 100%
0.75 - (0.75 x 0.50)
0.25
0.375
66.7%
x 100%
As previously mentioned it is important to make a mass
balance, or take an accounting of the fixed solids when ana-
lyzing the destruction of volatile matter in a digester. For
example, in the previous analysis the pounds of fixed solids
before digestion and after digestion were equal, and thus it
would seem that the sampling and digester mixing were good.
However what if the pounds of fixed solids before and after
digestion were not approximately equal? It would then seem
that either there was bad sampling, inadequate digester mix-
ing, or a combination of both. If this condition occurs, the previ-
ous calculations may be in error.
I. SECONDARY DIGESTER SLUDGE
Laboratory results indicate that a total digested sludge sofids
sample was 9.6 percent solids and 42.8 percent volatile con-
tent. The raw sludge solids volatile content was 68 percent.
The overall percent reduction, P, could then be arrived at by
using the formula,
D _ In - Out
.x 100%
In - (In x Out)
(0.68 - 0.43) x 100%
0.68 - (0.68) (0.43)
0.25 x 100%
0.68 - 0.29
0.25
x 100%
0.39
= 0.64 x 100%
= 64%
If sludge is drawn from the secondary digester, the total
pounds of dry solids may be calculated by using the 9.6 per-
cent solids results for that example and the volume of the
withdrawn sludge.
Thus,
Volume Secondary Digester Sludge in Gallons
x Solids, % x Weight of Sludge, LBIGAL22
= Total Solids, lbs
Total Solids, lbs x Volatile Solids, % = Volatile Solids, lbs
By subtracting from the raw sludge figures, the pounds re-
duction of total and volatile solids can be found.
QUESTIONS
Write your answers in a notebook and then compare your
answers with those on page 177.
12.31 During a 24-hour period, 3000 gallons of 5 percent
total solids sludge with a volatile content of 70 percent
was pumped to a digester. Calculate the pounds of:
(1) solids, and (2) volatile material pumped.
24 A gallon of water weighs 8.34 pounds. A gallon of digested sludge will weigh slightly more due to solids. The best way to find the weight Is to
weigh a gallon of the sludge.

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Sludge Digestion 145
12.3J Calculate the reduction in volatile solids if the percent
volatile entering the digester is 70 percent and the
percent leaving is 45 percent.
~ _ In - Out
x 100%
J.
In - (In x Out)
DIGESTER SUPERNATANT
The total solids test is run on the digester supernatant to
determine the solids load returned to the plant. The total solids
in the digester supernatant should be kept below V2 of 1 per-
cent (0.005 or 5000 mgIL. High solids content in the superna-
tant usually indicates that too much seed or digested sludge is
being withdrawn from the digester. This kind of withdrawal
could increase the volatile acid/alkalinity relationship which is
also undesirable.
Another simple method for checking supernatant is to draw a
sample into a 1000 ml graduate and let it stand for four or five
hours. The sludge on the bottom of the graduate should be
below 50 ml, with an amber colored liquor above it. If super-
natant solids are allowed to build too high, an excessive solids
and BOD load is placed on the secondary system and primary
clarifier. Sludge withdrawn from the secondary digester or
supernatant removal tubes should be changed to a different
level in the digester where the liquor contains the least amount
of solids when the supernatant load becomes too heavy on the
plant.
Plants should be designed to allow all sludge solids and
liquids to go to a lagoon or some such system for final or
ultimate disposal, rather than returning them to the plant.
K. COMPUTING DIGESTER LOADINGS
Digester loadings are reported as pounds of volatile matter
per cubic foot or 1000 cubic feet of digester volume per day.
The loading rate should be around 0.15 to 0.35 pounds of
volatile solids per cubic foot (2.4 to 5.6 kg/cu m) in a heated
and mixed digester. For an unmixed or cold digester, the load-
ing rate should not exceed 0.05 pounds of volatile matter per
cubic foot (0.8 kg/cu m), assuming that each cubic foot con-
tains approximately 0.5 pounds of predigested solids.
Going back to the 40-foot diameter and 20-foot water depth
digester described earlier, a raw sludge volume of 2800 gal-
lons was pumped, at 6.5 percent solids and 68 percent volatile
matter. It was determined that there were 1032 pounds of vol-
atile solids added to the digester per day.
EXAMPLE
Digester Loading,
lbs vol. matter/
cu ft/day
.041
lbs of Vol Matter Added per Day
Volume of Digester, cu ft
1032 lbs of Vol. Matter/day
25,120 cuft
= 0.041 lbs Vol. Matter/cu ft/day
25120) 1032.000
1004 80
27 200
25 120
This would be a light loading, but it is not uncommon in
small, new plants.
The pounds of solids that should remain in the digester to
maintain a suitable environment must be determined too. To
retain a favorable volatile acid/alkalinity relationship of around
0.1, at least ten pounds of digested sludge should be retained
in the digester for every pound of volatile matter added to the
digester.
Digested
Sludge
in Storage,
lbs
= Vol. Mat. Added, lbs/day x
10 lbs Dig. Sludge in Storage
1 lb Vol. Mat. Added per day
= 1032 lbs/day x t°Jbs Stora9e
1 lb Added/Day
= 10,320 lbs old sludge in storage on a dry
solids basis
The actual amount of sludge retained will depend on diges-
ter conditions and the volatile acid/alkalinity relationship.
Sometimes data are reported as pounds of volatile matter
destroyed per cubic foot or 1000 cubic feet of digester capacity
per day. Using the same data from above and starting from the
beginning with 2800 gallons, at 6.5 percent solids, and 68
percent volatile, assume a volatile solids reduction of 50 per-
cent.
EXAMPLE
Volatile Matter Destroyed, Ibs/day/cu ft
Volume of Sludge Pumped, gal/day x % Solids
x % Volatile x % Reduction x 8.34 lbs/gal
Volume of Digester, cu ft
Volume of Solids
2800 gals/day x 0.065 x 0.68 x 0.50 x 8.34 lbs/gal
25,120 cu ft
2800 gpd x 0.065 x Q.34 x 8.34
25.120 cu ft
.50
.68
400
300
.3400
.065
.34
260
195
2800 x 0.022 x 8.34
25,120 cu ft
.02210
2800 gpd
.022
5600
5600
61.600
61.6 x 8.34
25,120 cu ft
8.34
61.6
5004
834
5004
513.744
513.7 lb/day
25,120 cuft	024
= 0.0204 Ibs/day/cu ft	25120)513.70
or
= 20.4 lbs/day/1000 cu ft
L. COMPUTING GAS PRODUCTION
Digester gas data should be recorded in cubic feet produced
per day by the digestion system, as recorded daily from the
gas meter. The carbon dioxide (C02) content should normally
be tested once or twice a week. (See Chapter 16, "Laboratory
Procedures and Chemistry.") Gas production should range be-

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146 Treatment Plants
tween 12 and 18 cubic feet for each pound of volatile matter
destroyed (0.75 and 1.12 cu m/kg) in the digesters.
Assume that the gas meter readings have averaged 6000
cubic feet of gas per day. Using the data from the calculation of
volatile matter destroyed of 513.7 pounds per day, compute
gas produced per pound of volatile matter destroyed.
EXAMPLE
Gas Produced, cu ft/lb of vol. matter destroyed
Gas Produced, cu ft/day
lbs of Volatile Matter Destroyed, lb/day
6000 cu ft gas/day
11.67
513.7 lbs Volatile Matter Destroyed/day
12 cu ft gas/lb vol. matter destroyed
(0.75 cu m gas/kg vol. matter destroyed)
513.7)60000
5137
8630
5137
34930
30822
41080
QUESTIONS
Write your answers in a notebook and then compare your
answers with those on page 177.
12.3K Why would you run a total solids test on the digester
supernatant?
12.3L What would you do if the total solids were too high in
the digester supernatant?
Total water and solids to digester.
Water &
Solids,
lbs
Total Solids, lbs
% Solids as decimal
1518 lbs
0.065
= 23,400 lbs
Water to digester.
Water, lbs = Water & Solids, lbs - Solids, lbs
= 23,400 lbs-1518 lbs
= 21,882 lbs
or
= 21,900 lbs
Volatile Solids to digester.
Volatile
Solids,
lbs
= Total Solids, lbs x % Volatile Solids as decimal
= 1518 lbs x 0.68
= 1032 lbs
Inorganic Solids to digester.
Inorganic
Solids,
lbs
= Total Solids, lbs - Volatile Solids, lbs
= 1518 lbs - 1032 lbs
= 486 lbs
M. SOLIDS BALANCE, by F. Ludzack
What comes into a treatment plant must go out. This is the
basis of the solids balance concept. If you measure what
comes into your plant and can account for at least 90 percent
of this material leaving your plant as a solid (sludge), liquid
(effluent), or gas (digester gas), then you have control of your
plant and know what's going on in the treatment processes.
This approach provides a good check on your metering de-
vices, sampling procedures, and analytical techniques. It is an
eye opener when tried for the first time and advanced
operators are urged to calculate the solids balance for their
plant.
Using the data from Section G, "Raw Sludge," page 143, the
following example will illustrate the solids balance concept on a
digester and drying bed.
INPUT TO DIGESTER
2800 gallons of raw sludge with
solids content, 6.5% and volatile
solids content, 68%
DIGESTER OUTPUT or INPUT TO DRYING BED
Digested solids with
solids content, 4.5% and
volatile solids content, 54%
Calculate the pounds of total solids, water, volatile and inor-
ganic solids pumped into the digester.
Total solids to digester.
Dry
Solids, = Gals pumped x % solids as decimal x 8.34 lbs water/gal
lbs
= 2800 gals x 0.065 x 8.34 lbs/gal
= 1518 lbs. solids
Calculate the percent reduction in volatile matter in the di-
gester to find the pounds of gas produced during digestion.
Percent reduction of volatile matter
In - Out
. x 100%
In - (In x Out)
0.68 - 0.54
0.68 - (0.68 x 0.54)
45%
. x100%
Gas out of digester.
Gas, lbs = Volatile Solids, lbs x % reduction as a decimal
= 1032 lbs x .45
= 465 lbs
Determine the pounds of total, volatile, and inorganic solids
removed from the digester to the drying bed as digested
sludge.
Volatile Solids to drying bed.
Volatile
Solids,	= Volatile solids to digester, lbs -
lbs	Volatile solids out as gas, lbs
= 1032 lbs - 465 lbs
= 567 lbs
Total solids to drying beds.
Volatile Solids, lbs
Total
Solids,
lbs
% Volatile Solids as a decimal
_ 567 lbs
0.54
= 1050 lbs

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Sludge Digestion 147
Inorganic
Solids,
Inorganic solids to drying beds.
= Total Solids, lbs - Volatile Solids, lbs
= 1050 lbs-567 lbs
= 483 lbs (NOTE: Almost same as 486 lbs
to digester)
Total solids and water to drying bed.
_ Total Solids, lbs
Water &
Solids,
% Solids as decimal
= 1050 lbs
0.045
= 23,400 lbs	[NOTE: Same volume as put
into digester be-
cause of thinner
sludge going out.)
Find total pounds of water to drying bed and compare
amounts of water into and out of digester.
Water to drying bed.
Water, lbs = Water & Solids, lbs - Solids, lbs
= 23,400 lbs - 1050 lbs
= 22,350 lbs
or say = 22,400 lbs
Compare amounts of water in and out cf digester.
Water
Change, = Water Out, lbs - Water In, lbs
lbs = 22,400 lbs - 21,900 lbs
= 500 lbs drawdown in digester
In this case, more water was withdrawn in the thin sludge
than was added with the thick sludge. No supernatant was
withdrawn from the digester or recycled. All of the recycle ma-
terial must come from the dewatering operation.
DRYING BED OUTPUT
Dried residue removed, 2 lbs water/1 lb solids or 33% solids
Determine the pounds of water removed with the dried solids
and the pounds of drainage water recycled to the plant.
Water in solids.
Water in
Solids, = Total Solids, lbs x 2 lbs water/lb solids
lbs
= 1050 lbs x 2 lbs water/lb
= 2100 lbs
Drainage water recycled to plant.
Recycle
Water, = Water to Drying Bed, lbs
= 22,400 lbs - 2,100 lbs
= 20,300 lbs
lbs
Water in Solids, lbs
(less evaporation)
Summary
Constituent
Total Solids, lbs
Volatile Solids, lbs
Inorganic Solids, lbs
Water, lbs
Gas Out, lbs
Digester Drying Bed to Plant
1,518 1,050
1,032 567
486 483
21,900 22,400 20,300
465
To complete the solids balance, the quantity of water actu-
ally recycled and its solids content should be compared with
the calculated values. Another helpful solids balance is to
compare calculated and actual digester inputs and outputs on
an annual basis.
END OF LESSON 4 of 6 LESSONS
on
SLUDGE DIGESTION AND SOLIDS HANDLING
Please answer the discussion and review questions before
continuing with Lesson 5.

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148 Treatment Plants
DISCUSSION AND REVIEW QUESTIONS
Chapter 12. SLUDGE DIGESTION AND SOLIDS HANDLING
(Lesson 4 of 6 Lessons)
Write the answers to these questions in your notebook be-
fore continuing with Lesson 5. The question numbering con-
tinues from Lesson 3.
18.	Why is temperature measured in a digester?
19.	Why should the temperature in the digester not be
changed by more than one degree Fahrenheit per day?
20.	What is the first warning that trouble is developing in an
anaerobic digester?
21.	How would you try to stop and reverse an increasing vol-
atile acid/alkalinity relationship?
22. What is the percent reduction in volatile matter in a pri-
mary digester if the volatile content of the raw sludge is
69% and the volatile content of the digested sludge is
51%?
p _ In - Out
In - (In x Out)
23. How often should the volatile acid/alkalinity relationship in
a digester be checked?
CHAPTER 12. SLUDGE DIGESTION AND SOLIDS HANDLING
(Lesson 5 of 6 Lessons)
12.4 OPERATIONAL STRATEGY
All previous discussions and problem assignments were in-
tended to provide you with the basic working principles of
anaerobic sludge digestion. Their successful application in the
operation of a digestion system requires sound and thorough
daily operational checks in combination with adequate sam-
pling and neat, well-organized records of the resulting data.
Many operators find that plotting certain operational data in a
graphical form is very helpful to recognize changes or trends in
digester performance. Informative operational data that could
be plotted against time include:
1.	Digester loading
a. Volatile solids added, lbs/day per cubic foot of digester
capacity
or b. Volatile solids added, lbs/day per volatile solids under
digestion, lbs
2.	Volatile acids/alkalinity relationship
Volatile acids, mgIL per alkalinity, mgIL
3.	Gas production
1000 cubic feet of gas produced per day
4.	Carbon dioxide content of digester gas
Percent carbon dioxide
5.	Temperature
Degrees Fahrenheit or Degrees Celsius
Successful plant operators use basic knowledge together
with the daily checks and data to remain alert to changes in the
system and to anticipate problems, rather than finding it nec-
essary to react to fully developed upsets.
12.40 Operation and Maintenance Checklist
The following checklist is intended to help the operator re-
main "on-top" of the system. This list is general in nature, and
does not cover all situations, but serves as an example of the
checklist that should be made for each plant. You should pre-
pare a similar checklist for the anaerobic sludge digesters at
your treatment plant. As you make your rounds inspecting
each item, be alert. Investigate and record anything that looks
different or unusual, smells different, feels different (hotter or
vibrating more) and sounds different. If problems appear to be
developing, correct them now or alert your supervisor of the
changes.


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ITEM
A.	Raw Sludge Pumping
1.	Total sludge volume pumped in 24 hours or indi-
vidual feed periods. Record pump counter or meter
reading.
2.	Proper operation of pump(s). Check oil level. While
operating check motor, pump, packing (leaks), suc-
tion and discharge pressure.
3.	If density meter is used, check for proper operation
during pump run.
4.	Instrumentation, especially pump time clock opera-
tion.
5.	Sludge line valve positions.
6.	Visual observation of raw sludge being pumped.
Note consistency (thick or thin), color and odor (sep-
tic).
7.	Automatic sampler operation.
8.	Exercise all sludge valves by opening and closing.
9.	Lubricate all valve stems. Inspect and grease pump
motor bearings according to manufacturer"s rec-
ommendations.
B.	Boiler and Heat Exchanger
1 ¦ Temperature of the recirculated sludge.
2.	Temperature of the recirculated hot water.
3.	Boiler and heat exchanger temperature and pres-
sure.
4.	Water level in sight glass of day-water tank.
5.	Boiler and heat exchanger operation.
a.	Gas pressure
b.	Make-up water valve
c.	Pressure relief (pop-off) valve
d.	Power failure or low gas pressure shutdown
e.	Safety devices
6.	Boiler firing (flame-air mixture).
7.	Recirculated sludge pump operation. Check oil
level. While pump is operating check motor, pump,
packing (leaks), suction and discharge pressures.
8.	Inspect and grease pump motor bearings according
to manufacturer's recommendations.
C.	Digesters
1.	Record gas meter reading.
2.	Check gas manometers, (digester gas pressure)
3.	Record digester gas pressure and/or floating cover
position and indicator level reading.
4.	Drain gas line condensate traps and sedimentation
traps (from one to four times per day depending on
location of trap in gas system, temperature changes
and digester mixing systems).
5.	Check liquid level in the digester.
6.	Check supernatant tubes for operation and wash
down supernatant box.
7.	Check digester gas safety analyzer (L.E.L.) and
recorder.

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150 Treatment Plants
8.	Check and record level of water seal (located on
center dome of fixed cover digesters and between
tank wall and cover of floating cover digesters).
9.	Check operation of mixing equipment.
GAS
a.	Flow rate, cfm
b.	Pressure, psi
c.	Compressor operation
MECHANICAL
a.	Motor operation
b.	Drive belts or gear reducers
c.	Vibrations
d.	Direction of mixing (down-up)
10.	Examine waste gas burner for proper operation.
a.	Pilot on
b.	Number of burners on
c.	Digester gas pressure (wasting or excess)
11.	Exercise all sludge and gas system valves by open-
ing and closing.
12.	Check all supernatant tubes for operation and sam-
ple each for clearest liquor for supernatant removal
from digester.
13.	Check digester for scum blanket buildup.
14.	Examine the digester structure and piping system
for possible gas leaks. Examine the digester struc-
ture for cracks.
15.	Clean, inspect and calibrate the digester gas safety
analyzer and recorder.
16.	Lubricate all valve stems and rotating equipment as
required by the manufacturer.
17.	Clean and refill gas manometers with proper fluids
to levels specified by manufacturers.
18.	Flush and refill water seals (from 2 to 6 months).
Check weekly on fixed cover digester seals.
19.	For floating cover digesters, inspect flotation com-
partment for leakage or excessive condensation
buildup (pump out) and look for corrosion of cover
interior.
20.	Dewater digester and clean out, repair and paint.
Normal cleanout schedules are three (3) to eight (8)
years.
SCHEDULE
DAILY
WEEKLY
MONTHLY
SEMI-
ANNUALLY
AS
REQUIRED


•*-" i''-' '-V }',

*\ri JC,..,*.;
X




X




X




X




X




X




X




X





X



X





X




X



X





X




X





X




X





X




X





X



X





X
12.41 Sampling and Data Checklist
Results and interpretation of lab tests tell you what you are
feeding a digester and how the digester is treating the sludge.
Graphically recording lab results helps to interpret what's hap-
pening in a digester. If undesirable trends start to develop,
refer to the appropriate section in this manual for the proper
corrective action.

-------
ITEM
A.	Raw Sludge
1.	Composite raw sludge sample. If grab is taken instead,
then prepare a composite twice a week.
2.	Total and volatile solids.
3.	pH
B.	Supernatant
1. Solids (total and volatile) and COD. Graphically record
the data and be alert to long-term decreasing quality
(increased levels of solids and COD) of supernatant
quality.
C.	Digested Sludge
1.	Grab sample
2.	Temperature
3.	pH
4.	Cubic feet of total gas and C02 content.
5.	Calculate and graphically record gas production and
C02 content.
6.	Calculate and graphically record loading rate (solids
and hydraulic).
7.	Volatile acids
8.	Alkalinity
9.	Calculate and graphically record volatile acid/alkalinity
relationship.
10.	Digested sludge total solids and volatile solids.
11.	Solids (total and volatile) and temperature profile at
five-foot (1.5 m) intervals from the digester bottom up
to the surface. If scum blanket present, try to break it
up.
D.	Solids Balance
1. Calculate the solids balance on the digesters (see Sec-
tion 12.3M. Solids Balance). This calculation helps in-
dicate to you how well you are controlling the digester
operation.
In Item 12.41, C-11, as regards the profile sampling of the
digester, the solids and temperature data should be carefully
examined for indications of poor mixing in the digester or grit
accumulation at the bottom of the digester. The operator
should use the data to calculate the useful volume of the diges-
ter (total volume minus the grit volume). Such data can be
graphically plotted against time to show the rate of grit buildup
and the date for digester cleaning. An example of such a plot is
illustrated in Figure 12.21, although actual data may not plot a
straight line.
Sludge Digestion 151
SCHEDULE
DAILY
BI-
WEEKLY
WEEKLY
MONTHLY




X
(X)


X
(X)



X









X




X



X



X



X



X



X



X




X



X



X





X



X




-------
152 Treatment Plants
0	5	10	|5	20
TIME IN SERVICE (YEARS)
Fig. 12.21 Active volume of a digester tank
(Permission of Los Angeles County Sanitation District)

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Sludge Digestion 153
12.42 Normal Operation
In this chapter we have discussed the following important
topics regarding digester operation:
1- Section 12.1, Components in the Anaerobic Sludge Diges-
tion Process;
2.	Section 12.2, Operation of Digesters; and
3.	Section 12.3, Digester Controls and Test Interpretation.
This section combines the highlights of those portions of the
previous sections that are critical to the actual day-to-day op-
eration of an anaerobic sludge digester. For details, refer to the
actual section. The normal operation of a digester involves the
following activities:
1.	Feeding Sludge to the Digester (Section 12.22, Feeding);
2.	Maintaining the Proper Temperature (Section 12.14, Diges-
ter Heating);
3.	Keeping the Contents of the Digester Mixed (Section 12.15,
Digester Mixing);
4.	Removing Supernatant (Section 12.27, Supernatant and
Solids); and
5.	Withdrawing Sludge (Section 12.28, Rate of Sludge With-
drawal).
Let's study each one of these activities.
1 • Feeding Sludge to the Digester (See Section 12.41, A. Raw
Sludge)
a.	Pump as thick a sludge as possible to the digester.
Watch sludge being pumped, listen to sound of sludge
pump, and observe any instruments that indicate thick-
ness of sludge.
b.	Pump small amounts of sludge at regular intervals to
prevent adding too much raw sludge too fast for the
organisms or for the temperature controls to maintain a
constant temperature.
c.	Calculations
(1)	Try not to add more than one pound of volatile
matter per day for every ten pounds of digested
sludge in storage (1 kg V.M./day per 10 kg digested
sludge). This ratio may vary from digester to diges-
ter and from season to season.
(2)	Calculate the volatile acid/alkalinity relationship
and plot the results. If the relationship starts to in-
crease, try to pump a thicker sludge or reduce the
amount of volatile matter added per day. Also re-
duce the pumping rate of digested sludge.
See Section 12.3, Digester Controls and Test Interpretation,
B. Volatile Acid/Alkalinity Relationship and K. Computing Di-
gester Loadings for details.
2.	Maintaining the Proper Temperature (See Section 12.40, B.
Boiler and Heat Exchanger)
Record the temperature of the recirculated sludge every
day. If the temperature changes from the desired level, ad-
just the temperature controls. Do not allow the temperature
to change more than 1°F (0.5°C) per day. Determine the
temperature (usually between 95 and 98°F or 35 and 37°C)
that best suits your digester.
3.	Keeping the Contents of the Digester Mixed
How a digester is mixed depends on the mixing equipment
and whether you have a single-stage or two-stage digestion
process. Digester contents must be well mixed to provide
an even distribution of food (raw sludge), organisms, alka-
linity, heat and waste bacterial products. Good mixing
should prevent the buildup of a scum blanket and the depo-
sition of grit on the bottom of the digester. If mixing is in-
adequate, try increasing the time of mixing and/or looking
for equipment problems.
4.	Removing Supernatant
Supernatant should be removed from the digesters on a
daily basis. Whether you have a single-stage or two-stage
digestion process, mixing should be stopped for 6 to 12
hours before supernatant removal to allow the supernatant
to separate from the digested sludge. Adjust or select the
supernatant tube that produces the least solids to remove
supernatant from the digester. Carefully observe your other
treatment processes to be sure the supernatant does not
cause a solids or BOD overload on other treatment pro-
cesses. Remove supernatant and digested sludge until suf-
ficient space is obtained in the digesters for the incoming
raw sludge.
5.	Withdrawing Sludge
Before withdrawing sludge, stop mixing for 6 to preferably
12 hours to allow the digested sludge to separate from the
supernatant. The digester contents must be well mixed be-
fore stopping mixing so a lot of raw sludge will not be re-
moved with the digested sludge. Good mixing also prevents
the buildup of a scum blanket and the development of con-
ing during the removal of digested sludge. The withdrawal
rate of sludge from either digester should be no faster than
a rate at which the gas production from the system is able to
maintain a positive pressure in the digester (at least two
inches (5 cm) of water column).
12.43 Troubleshooting
Using the information obtained from the analysis of the sam-
ples and the daily rounds, the knowledgeable and alert
operator can note changes from normal operation. The first
step is to realize that there is a problem, and the second step is
to take the appropriate corrective action. Table 12.2 is in-
tended to be an example of a logical sequence that can be
followed to identify and correct an impending or actual digester
upset. The four indicators of a problem tell you to look for one
or more of the problem areas listed that need correcting.
Toxicity can be a very difficult problem to identify and solve.
Heavy metals can gradually creep up in concentrations until
toxic levels are reached. Also as the pH decreases the concen-
trations of dissolved metals tend to increase and become toxic
to bacteria in the digester.
Possible methods of controlling toxic materials include:
1.	Remove toxic material from waste,
2.	Dilute toxic material below its toxic level,
3.	Add a chemical that will neutralize the toxic material, and
4.	Add a chemical that will cause the toxic material to precipi-
tate out of solution or form an insoluble compound.
If soluble toxic heavy metals are present, sodium sulfide
(Na2S) can be added which will cause the formation of non-
toxic insoluble heavy metal sulfide compounds. Digesters are
similar to people in many ways. A small amount of something
may be very good for a digester, but too much may be toxic as
shown in Table 12.3.

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154 Treatment Plants
TABLE 12.2 DIGESTER OPERATION TROUBLESHOOTING
INDICATION FROM DATA
PROBLEM AREA

POSSIBLE CAUSE

Toxicity	
— 1.
2.
Slug of toxic material.
Constant feed that has reached toxic limit.

Digester Loading	
— 1.
2.
3.
Change in raw sludge pumping.
Raw sludge density or V.S. changed
Raw sludge pH change.
• Rise in V.A./Alk Ratio

4.
Decrease in effective volume of the
• Gas Production Decrease
	K

digester.
or Increase in C02
\ Digester Heating	
— 1.
Heat exchangers plugged.
• Decrease in V.S. Reduction
	*
2.
3.
Recirculated sludge pump not working.
Boiler malfunction.
• High Solids in Supernatant

4.
Unsteady sludge temperatures — more than 1°F/
day or 0.5°C/day.

Digester Mixing	
—-1.
2.
3.
Fouled draft tube.
Mechanical or electrical failure.
In case of gas mixing, inadequate recirculation.

Gas System	
—1.
2.
3.
4.
Gas meter failure.
Leaking gas.
Abnormal pressure.
Plugged gas line.

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Sludge Digestion 155
TABLE 12.3 BENEFICIAL AND TOXIC
CONCENTRATIONS OF MATERIALS ON DIGESTION
PROCESS
Material
Beneficial
Moderately
Inhibitory
Toxic
Ammonia Nitrogen, mg IL
Calcium, mgIL
Magnesium, mg IL
Potassium, mgIL
Sodium, mgIL
50-200
100-200
75-150
200-400
100-200
1500-3000®
2500-4500
1000-1500
2500-4500
3500-5500
3,000
8,000
3,000
12,000
8,000
aToxic at higher pH values
12.44 Actual Digester Operation
By using the procedures outlined in this Section, digesters
can be operated successfully without any problems. The in-
formation plotted in Figure 12.22 shows some of the informa-
tion used by an operator to operate four digesters with a total
capacity of 6.9 million gallons (26,000 cu m). This activated
sludge plant treats an average daily flow of approximately 18
MGD (68,130 cu m/day) with flows averaging over 24 MGD
(90,840 cu m/day) during the canning season. Under adverse
conditions, the digesters have provided only 8 days of deten-
tion time, yet the digesters have never become upset.
Raw sludge from the primary clarifiers and gravity thickened
waste activated sludge are fed on a regular basis throughout
the day to each digester. Every 2 hours the operators read and
record the gages, pump meters and temperature readings.
Temperatures are controlled by adjusting the heat exchanger.
Digester contents are continuously mixed through draft
tubes. Every day the flows through the draft tubes are reversed
for two hours to knock off rags accumulated on the draft tubes.
Additional mixing is available using digested sludge recircula-
tion pumps, if necessary. The operator reviews the lab data
and if problems appear to be developing, additional mixing is
applied, if appropriate. If everything is satisfactory and mixing
¦s greater than usual, mixing is reduced.
The following information is recorded with regard to the di-
gesters:
1 - Raw Sludge and Thickened Waste Activated Sludge to Di-
gesters
a.	Volume, gallons per day
b.	pH
c.	Total solids, %
d.	Volatile solids, %
2.	Digester Gas
a.	Total production, cubic feet per day
b.	Carbon dioxide, %
3.	Digested Sludge (mixed digester contents)
a.	Volatile acids, mgIL
b.	Alkalinity, mgIL
c.	Total solids, %
d.	Volatile acids, %
e.	pH
4.	Sludge removed (mixed digester contents)
a.	Volume, gallons per day
b.	Total solids, %
c.	Volatile solids, %
Volatile acid/alkalinity relationship has been the key to suc-
cessful digester operation over the last nine years without any
of the five digesters becoming upset. Volatile acids and alkalin-
ity are normally run three times per week on each digester. If
one high volatile acid reading is observed, the volatile acid test
is repeated the next day. Usually the volatile acid value is back
down to the normal range the next day. If the volatile acid value
is high, the raw sludge pumped to the digester is cut in half or
stopped until the volatile acid reading is normal again. Usually
this requires only one or two days.
These digesters are not used for liquid-solids separation.
Therefore, no information is collected on the supernatant.
QUESTIONS
Write your answers in a notebook and then compare your
answers with those on page 177.
12.4A How often should gas line condensate traps and
sedimentation traps be drained?
12.4B Where is the water seal located on both fixed cover
and floating cover digesters?
12.4C How can you tell if the quality of the digester superna-
tant is decreasing?
12.4D List the activities involved in the normal operation of a
digester.
12.5 DIGESTER CLEANING
12.50 Need for Digester Cleaning
Under the ideal conditions of perfect mixing and no grease
and grit accumulation, the total design volume of a digester will
always be available for operation. However, operators are well
aware that ideal conditions seldom exist in the field, and that
grease and grit do accumulate in digesters even with the best
mixing devices. As the grease and grit volume increases, the
digester volume available for good digestion (active volume)
decreases. This action is graphically shown in Figure 12.21 for
a typical digester. As shown by that curve, at the end of eight
years of service, only 67 percent or 2/3 of the design digester
volume is available for anaerobic digestion. Thus if the design
digester detention time was calculated to be 30 days, at the
end of eight years of service it would be 20 days (2/3 x 30
days = 20 days). A continued decrease in digester volume will
result in further decreases in volatile solids destruction, lower
gas production, and ultimately, failure of the digestion process
if the digester is not cleaned. Figure 12.21 is meant only as an
example of the decrease in the active volume of a digestion
tank with time. For the particular situation that an operator may
face, how rapidly the digester volume decreases and when to
clean the tank will depend on many factors. Among these fac-
tors are:
1.	Rate of grit and grease accumulation (this should be period-
ically measured as indicated in the checklist of Section
12.41);
2.	Type and extent of mixing;
3.	Shape of the digestion tank;
4.	Operating condition of the equipment inside the digester;
and
5.	Type of sludge treated.
The normal cleaning interval of anaerobic digesters is be-
tween three and eight years, but this will vary greatly with the
factors listed above. Between every 6 months to one year, the
depth of heavy solids and scum should be measured. The
important thing for the operator is to record the condition of the
digester volume with time and thus have a planned or lead time
for the cleaning operation. When approximately one-third of

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156 Treatment Plants
VOLATILE ACID/ALKALINITY (DIGESTER 1)
0.10
0.05
REDUCE
TOTAL SLUDGE TO DIGESTERS
500
400
300
200
VOLATILE MATTER TO DIGESTERS
85
80
75
10
25
15
20
5
30
DAY OF MONTH
Fig. 12.22 Actual digester operating data

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Sludge Digestion 157
the capacity is filled or when the process starts to fail, clean the
digester.
12.51	Pre-Cleaning Decisions
When it has been decided that a digester must be cleaned,
there are certain questions that must be answered before ac-
tual cleaning begins.
1.	While the digester is being cleaned, what will be done with
the raw sludge?
If the plant has only one digester, then the answers to this
question are limited: 1) the sludge could be hauled to a
nearby treatment plant for processing, 2) temporarily con-
vert an activated sludge aeration tank to an aerobic diges-
ter, 3) construct a temporary anaerobic lagoon, or 4) hold
the sludge in the primary clarifiers but keep the collector
mechanism running. The final two alternatives could pre-
sent significant odor problems and also seriously impact
surface or ground waters. Do not attempt these methods
without the permission of the appropriate regulatory agen-
cies. If more than one digester is available at the plant, then
the digester remaining in service can be used to digest all of
the raw sludge for a short time (usually not more than 10
days).
2.	Where will the cleanings be disposed of?
The digested sludge obtained from the digester while it is
being pumped down can be disposed of in the normal plant
manner. However the digester cleanings which are largely
composed of grit, grease and other heavy solids and fibrous
material, will normally require additional considerations for
disposal. This can vary from hauling directly to a landfill,
which can be very expensive, to ponding the material for
solar drying and subsequent disposal in a landfill or on the
land. Remember that the material has a large amount of grit
and grease and this may require special equipment for the
sludge hauling vehicles to control odor.
3.	Will the cleaning be accomplished by contract or with the
use of plant personnel?
Normally this is a decision between the price offered by the
contractor, compared to the equipment available and expe-
rienced plant operators available for the job.
12.52	Cleaning Methods and Necessary Equipment
The methods used in cleaning a digester can vary from sim-
ply opening a valve and draining the digester contents with the
aid of a washdown hose or fire hose, to a large drying bed, or
to using an extensive system such as shown in Figure 12.23.
In this system the digested sludge is first drained from the
digester to the normal sludge processing station. Then with the
aid of several turret nozzle mechanisms mounted over access
holes on the top of the digester, the remaining grease, grit and
other accumulated solids are washed from the digester and
pumped to the digester cleaning system. The cleaning system
consists of an inclined screen for the removal of all large size
solids such as hair, grease, seeds, and cigarette butts. A cen-
trifugal separator or degritter is used for the removal of all
remaining suspended and settleable material.
The above described system could be temporarily put to-
gether with lease equipment, but certainly there are other ways
to clean digesters. In summary, these can be broken down into
three conditions, depending upon how the digester cleanings
are to be handled:
1.	Gravity flow to the disposal area;
2.	Pump to the disposal area; and
3. Pump to a tank truck for distant disposal.
A general list of the equipment necessary to clean a digester
under any of the above methods is summarized in Table 12.4.
TABLE 12.4. DIGESTER CLEANING EQUIPMENT
SUMMARY-
eouipment ITEM	DIGESTER CLEANINGS DISPOSAL OPTIONb

1
2
3
1. Sludge line valves
X
X
X
2. Sludge line



(permanenl)
X
X
X
3. Sludge line



(temporary)
X
X
X
4. Digesler access
X
X
X
5. Explosion-proof



vent fan
X
X
X
6. Explosion meter
X
X
X
7. Safe ladder
X
X
X
8. Self-contained



breathing



apparatus
X
X
X
9. Safety harness
X
X
X
10. Explosion-proof



lights
X
X
X
11. Water source
X
X
X
12. Wash-down hose
X
X
X
13. Nozzle with shutoff
X
X
X
14. Wash water pump
O
X
oc
15. Fixed sludge pump

X
oc
16. Portable sludge



pump

X
oc
17. Turret nozzle


oc
18. Tripod or hoist


oc
19. Tank truck
O
X
oc
20. Cranec


X
NOTE: a Adapted from OPERATIONS MANUAL - ANAEROBIC
SLUDGE DIGESTION, Environmental Protection Agency,
February 1976. Available from Superintendent of Docu-
ments, U.S. Government Printing Office, Washington,
D.C. 20402, USPO #055-001-01075-3. Price $3.25.
b "X" indicates definitely needed equipment.
"O" indicates possibly needed equipment.
c This equipment will be definitely needed if there is an ab-
normally heavy accumulation of solidified solids, such as
grease and grit.
12.53 Safety
The efficient cleaning of a digester demands that the
operator follow appropriate safety rules. Some of the more
important safety precautions are listed below.
1.	When the digester is taken out of service, make sure the
gas collection system is isolated and provide adequate ven-
tilation through the access holes with the use of explosion-
proof vent fans.
2.	Test for explosive conditions with an explosion meter.
3.	Before entering a digester, always test the atmosphere for
oxygen content and toxic gases (hydrogen sulfide).
4.	Provide adequate ventilation at all times.
5.	Always use explosion-proof motors and electrical equip-
ment when working near openings in the digester.
6.	Never enter a digester alone. As a general rule, there
should always be at least two persons on top of the diges-
ter for every person inside the tank.

-------
tn
oo
diqester
PRIMARY EFFLUENT
0
fi>
3
(D
3
2
at
3
0)
DIGESTER CLEANINGS
STATIC SCREEN
TRUCK TO
LANDFILL
CYCLONE SEPARATOR
TRUCKTO
LANDFILL
DISSOLVED AIR FLOTATION
FLOAT SOLIDS TO DEWATERING
OR DISPOSAL

EFFLUENT
TO PLANT
STORAGE
Fig. 12.23
Flow diagram of digester cleaning treatment
system

-------
Sludge Digestion 159
7.	When working in the digester always use a safety harness
equipped with a safety line.
8.	Always use a bucket and rope to lower tools and equip-
ment.
QUESTIONS
Write your answers in a notebook and then compare your
answers with those on page 177.
12.5A What kinds of materials accumulate in digesters and
reduce the active volume for digesting sludge?
12.5B What happens in a digester when the active volume
is reduced?
12.5C What could be done with the raw sludge while the
digester is being cleaned if a plant has only one di-
gester?
12.5D What kinds of tests should be performed on the di-
gester atmosphere before entry?
END OF LESSON 5 OF 6 LESSONS
on
SLUDGE DIGESTION AND SOLIDS HANDLING
Please answer the discussion and review questions before
continuing with Lesson 6.
DISCUSSION AND REVIEW QUESTIONS
Chapter 12. SLUDGE DIGESTION AND SOLIDS HANDLING
(Lesson 5 of 6 Lessons)
Write the answers to these questions in your notebook be-
fore continuing. The question numbering continues from Les-
son 4.
24.	How can you anticipate problems with anaerobic diges-
ters and correct them before a problem becomes seri-
ous?
25.	When observing raw sludge being pumped, what items
would you observe?
26.	How would you feed sludge to a digester?
27.	How would you determine if an anaerobic digester was
not operating properly?
28.	How would you determine when a digester needs clean-
ing?
CHAPTER 12. SLUDGE DIGESTION AND SOLIDS HANDLING
(Lesson 6 of 6 Lessons)
12.6 AEROBIC SLUDGE DIGESTION
12.60 Comparisons between Anaerobic and Aerobic
Digestion (also see Volume III, Chapter 22)
Aerobic digestion of solids occurs, whether intentional or
not, in any of the conventional secondary treatment pro-
cesses. In the extended aeration process, the aerobic diges-
tion process is continued almost to the maximum obtainable
limit of volatile matter reduction. A separate aerobic digester
is intended mainly to insure that residual solids from aerobic
biological treatment processes are digested to the extent that
they will not cause objectionable odors during disposal. An
aerobic digester may be used to treat mixtures of waste acti-
vated sludge or trickling filter sludge and primary sludge, or
only waste activated sludge, or waste activated sludge from
plants with no primary sedimentation tanks. The aerobic di-
gester is a separate operation following other processes to
extend decomposition of solids and regrowth of organisms to
a point where available energy in active cells and storage of
waste materials are sufficiently low to permit the material to
be considered stable enough for discharge to some ultimate
disposal operation. Neither aerobic nor anaerobic sludge di-
gestion completes the oxidation of volatile materials in the
digester.
Important comparisons between aerobic and anaerobic
sludge digestion are summarized in the following sections.

UNTfe&

-------
160 Treatment Plants
will have a very poor quality.
Detention time depends on the origin of the sludge being
treated. Twenty days will provide sufficient digestion time for
sludges from an extended aeration process where the sludges
are already well digested. Sludges from a contact stabilization
process require more than twenty days. When temperatures
are very low, the sludge may have to be held until the weather
warms in the spring.
12.62 Operation
Aerobic digesters are operated under the principle of ex-
tended aeration from the activated sludge process, relying on
the mode or region called ENDOGENOUS23 respiration.
Aerobic digestion conists of continuously aerating the sludge
without the addition of new food, other than the sludge itself, so
the sludge is always in the endogenous region. Aeration con-
tinues until the volatile suspended solids are reduced to a level
where the sludge is reasonably stable, does not create a nui-
sance or odors, and will readily dewater.
"WW*'
n
& I 3
ANAEROBIC SLUDGE DIGESTION
1.	Does not use aeration as part of the process.
2.	Works best on fresh wastes that have not been treated
by prior stabilization processes.
3.	Uses putrefaction as a basic part of the process.
4.	Tends to concentrate sludge and improves drainability.
5.	Produces methane gas that provides energy for other
operations.
6.	Generates major digestion products consisting of solids,
carbon dioxide, water, methane, and ammonia.
7.	Produces liquids that may be difficult to treat when re-
turned to the plant.
8.	Generates sludges that need additional stabilization be-
fore ultimate disposal.
AEROBIC SLUDGE DIGESTION
1.	Has lower equipment costs, but operating costs are
higher, mainly because of energy requirements.
2.	Tends to produce less noxious odors.
3.	Produces liquids that usually are easier to treat when
returned to the plant.
4.	Generates major digestion products consisting of re-
sidual solids, carbon dioxide, water, sulfate, and nitrate
compounds. Most of these products are close to the final
stabilization stage.
5.	May achieve nitrogen removal by stopping aeration long
enough to allow the conversion of nitrate to nitrogen gas.
Aeration must be restarted before sulfate compounds
are converted to sulfide (H2S).
6.	Tends to work better on partially stabilized solids from
secondary processes that are difficult to treat by the
anaerobic digestion process.
7.	Produces a sludge that has a higher water content.
Aerobic sludges are difficult to concentrate higher than 4
percent solids.
8.	Uses oxygenation and mixing provided by aeration pro-
cess equipment.
9.	Has less hazardous cleaning and repairing tasks.
10. Works by aerobic decay which produces fewer odors
when operated properly.
12.61 Process Description
Aerobic digestion tanks may be either round or rectangular,
eighteen to twenty feet (5.4 to 6 m) deep, with or without
covers, depending on geographical location and climatic condi-
tions. The tanks use aeration equipment (mechanical or dif-
fused air) to maintain aerobic conditions. Each tank has a
sludge feed line at mid-depth of the tank, a sludge draw off line
at the bottom of the tank, and a flexible, multilevel supernatant
draw off line to remove liquor from the upper half of the tank.
Covers are used in colder climates to help maintain the tem-
perature of the waste being treated. Covers should not be used
if they reduce evaporative cooling too much and the liquid
contents become too warm. When the liquid becomes too
warm, offensive odors may develop and the process effluent
23 Endogenous (en-DODGE-en-us) A reduced level of respiration (breathing) in which organisms break down compounds within their own
cells to produce the oxygen they need.
To place aerobic digesters (assume this plant has three
aerobic digesters) in series into service, fill the first digester
with primary effluent to within three feet (1 m) of the normal
water level and start the aeration equipment. Pump to the
aerobic digestion process whenever sludge is pumped. Waste
aerobic sludge from the secondary clarifier will provide the
seed to start the process. Maintain a dissolved oxygen level
near 1.0 mgIL in the aerobic digester.
Pump raw primary and secondary sludges to the aerobic
digester in the same manner sludge is pumped to an anaerobic
digester, except sludge concentrations in the range of 1.5 to 4
percent are commonly pumped to the aerobic digester.
When the aerobic digester has filled to normal water level,
turn off the aeration equipment and allow the solids to settle to
the bottom of the tank. This will leave a supernatant above the
solids. Don't leave the aeration equipment off too long because
odors will start to develop.
After the solids have settled, adjust the flexible, multi-level
supernatant line to draw off a foot or two (0.3 to 0.6 m) of water
from the upper portion of the tank. Sufficient water is removed
from the digester in order to accommodate another 24-hour
flow of sludges from the primary and secondary clarifiers. Re-
start the aeration equipment when sufficient water has been
removed.
Water withdrawn from the aerobic digester may be dis-
charged to a pond or returned to the primary clarifier. If the
water is returned to the primary clarifier, the clarifier should be
capable of handling the extra flow. Primary effluents frequently
have undesirably high solids levels.
Next day, repeat the process of stopping aeration, allowing
settling, and removing a portion of the supernatant liquor to
make room for another day's pumping of sludge. After a week
or two the solids level will build-up to occupy approximately fifty
percent of the tank volume during the settling period with a
suspended solids concentration of 10,000 to 15,000 mg IL.

-------
Sludge Digestion 161
Place the second aerobic digestion tank in service at this
time. Fill the second aerobic digester with primary or secon-
dary effluent to within three feet (1 m) of the normal water level.
Transfer a foot (0.3 m) or so of sludge from the bottom of the
first digester to the second one, leaving sufficient room in the
first to accept another 24-hour period of sludge pumping. Start
the aeration equipment in both digesters.
On the next day supernatant should be removed only from
the second digester to the primary clarifier. Transfer enough
supernatant from the first aerobic digester to allow enough
room for one day's sludge pumping. When the second aerobic
digestion tank attains the desirable solids level, place the third
aerobic digester into service.
After all three tanks are in operation, the aeration equipment
is seldom stopped in the first tank. Remove supernatant from
the second and third tanks only. Withdraw solids from the third
tank for disposal to drying beds or mechanical dewatering as
required. The water levels in the tanks should be kept equal
when the tanks are operated in a series.
New sludge is introduced into the first tank. All of the tanks
receive organisms and their stored materials as food. When
starting with new cell mass containing negligible silt, up to
about 40 percent of the volatile material can be digested. By
the time the sludge reaches the third tank most of the food has
been used by the organisms, but they still require energy.
Under these conditions they use their own cell material to the
extent that only their empty shells remain.
The greatest oxygen demand is exerted in the first tank, and
the demand decreases as the sludge is moved to the second
and third tanks. Usually sufficient oxygen is being supplied in
the third tank if the sludge is kept mixed and not allowed to
settle to the bottom of the digester. Dissolved oxygen levels in
the tanks should be maintained at or above 1.0 mgIL.
12.63	Operational Records
Successful operation requires the operator to record the fol-
lowing information:
DAILY
1.	Volume of raw and secondary sludges transferred to the
aerobic digesters.
2.	Pounds of solids transferred and volatile content.
3.	Volume of supernatant liquor withdrawn from last digestion
tank.
WEEKLY
1. Supernatant solids and volatile solids content in digesters.
WHEN SLUDGE IS WITHDRAWN
1.	Volume of sludge withdrawn for dewatering.
2.	Pounds of solids dewatered and volatile content.
3.	Pounds of volatile solids destroyed during digestion.
12.64	Operational Problems
12.640 Scum
The aerobic digesters will have to be skimmed periodically to
remove floating grease and other material that will not digest.
This material should be disposed of by incineration or burial
with the scum collected from the primary clarifier.
12.641	Odors
Odors should not be a problem in aerobic digestion unless
insufficient oxygen is supplied or a shock load reaches the
aerobic digestion tanks. If an odor probem does occur, a very
effective cure is to recycle sludge from the bottom of the sec-
ond or third tank back to the first tank. This is also good prac-
tice in activated sludge plants that have bulking problems be-
cause sludge from the last aerobic digester responds very
quickly when returned to an aerator.
12.642	Floating Sludge
Floating sludge may become quite thick in the second and
third tanks when aeration is stopped during removal of the
supernatant. To avoid clogging, the supernatant draw-off line
should be installed so the withdrawal point is from two to six
feet (0.5 to 1.8 m) below the water surface. The floating sludge
is a problem only during supernatant removal. Scum and solids
must be removed from the supernatant to prevent interference
with other treatment processes and degradation of the plant
effluent.
12.65 Maintenance Problems
Usually this process requires very little maintenance.
Routinely hose the side walls of open tanks for appearance
and fly control.
12.650 Diffuser Maintenance
If diffused air is used for aeration, only open orifice or nozzle
type diffusers should be installed because of the daily stopping
of air flow during supernatant removal.
12.657 Aeration Equipment
Aeration equipment should be operated continuously except
when settling is needed for supernatant removal. Both settling
and supernatant removal should be accomplished in 0.5 to 1.5
hours.
QUESTIONS
Write your answers in a notebook and then compare your
answers with those on page 178.
12.6A Why do some plants have aerobic digesters?
12.6B What are some of the advantages of aerobic digestion
in comparison with anaerobic digestion?
12.6C What dissolved oxygen levels should be maintained in
aerobic digesters?
12.7 DIGESTED SLUDGE HANDLING
After sludge has passed through an aerobic or anaerobic
digestion system, it must be dewatered and disposed of. Small
treatment plants are usually provided with sludge drying beds,
while larger plants utilize mechanical dewatering and drying
systems. These processes will be briefly discussed in this sec-
tion. For a more detailed and complete discussion, refer to
Chapter 22, "Solids Handling and Disposal."
12.70 Sludge Drying Beds (See Fig. 12.24)
The drying process is accomplished through evaporation
and percolation of the water from the sludge after it is spread
on a drying bed. The drying bed is constructed with an under-
drain system covered with coarse crushed rock. Over the rock
is a layer of gravel, and then a layer of pea gravel covered with
six to eight inches (15 to 20 cm) of sand.

-------
162 Treatment Plants
CLEAN OUT AT GRADE-
SLUDGE LINE
fmjLLGiSIfllSJ
BED 1

BED UNDERDRAIN
BED 2
REMOVABLE REDWOOD
PLANKS FOR BED FILLING
A..	
SLUDGE INLET
TO BEDS
BED 4
BED 3
WALKWAY ON TOP OF
BED WALL
BED DRAIN LINE RETURNING TO PLANT HEADWORKS
PLAN SECTION
-D
CLEAN OUT
AT GRADE
SAND BED SURFACE
T
;• o o o c a o o o
f	SLUDGE INLET
O O O o v_> o o ^ o O

CROSS SECTION
BED DRAIN LINES
SAND
PEA GRAVEL
CRUSHED ROCK
DRAIN LINE
Fig. 12.24 Sludge Drying Bed

-------
Sludge Digestion 163
Before sludge is applied, loosen the compacted sand layer
by using a sludge fork with tines eight to twelve inches (20 to
30 cm) long. Stick the tines of the fork into the sand bed and
rock it back and forth several times. This is to loosen the sand
only, and care should be taken that the gravel and sand layers
are not mixed. After the whole surface of the bed is loosened,
rake it with a garden rake to break up the sand clods. Then
level the bed by raking or dragging a 4" x 6' or 2" by 12" board
on ropes to smooth the surface.
Sludge is then drawn to the bed from the bottom of the
secondary anaerobic digester, or the aerobic digester. Draw
the sludge slowly so as not to create a negative pressure in the
anaerobic digester and to prevent coning of sludge in the bot-
tom of the digester. A thick sludge of 8 percent solids travels
slowly, and if the draw-off rate is too fast, the sludge around the
pipe flows out and the thicker sludge on the bottom moves too
slowly to fill the void. Consequently, the thinner sludge above
the draw-off pipe moves in; and when it does, the supernatant
level is reached, thus allowing almost nothing but water to go
to the drying bed. The thin sludge and supernatant flowing
down to the draw-off pipe washes a hole (shaped like a cone)
in the bottom sludge. When this occurs it sometimes may be
remedied by "bumping." This is accomplished by quickly clos-
ing and opening the draw-off valve on a gravity flow system,
which creates a minor shock wave and sometimes washes the
heavier sludge into the cone. If the digested sludge is pumped
to the drying bed, quickly start and stop the pump using the
power switch to create the "bumping" action.
To draw sludge slowly is time consuming and requires fre-
quent checks to be sure it does not thicken and stop flowing
completely or cone and run too fast.
The sludge being drawn to the bed is sampled at the begin-
ning of the fill, when the bed is half full, and just before the bed
is filled to the desired level. The samples may be mixed to-
gether or analyzed separately for total and volatile solids.
The depth to which the sludge is applied is normally around
12 inches (30 cm), but sometimes it is as deep as 18 inches
(45 cm) in arid regions. If it is deeper, the time required for
drying is too long. A bed filled with 20 inches (50 cm) of sludge
would require approximately the same time to dry as a bed
loaded with 14 inches (35 cm), dried and removed and filled
with another load 14 inches (35 cm) deep. Drying anaerobi-
cally digested sludge requires special precautions.
After a bed of sludge is drawn, the sludge draw-off line
should be flushed and cleared with water so the solids won't
cement in the line. One end of the line is left open for gas to
escape, if it forms. Be sure to drain the line if freezing is a
problem.
In warm weather, a good sand bed will have the sludge dry
enough for removal within four weeks. The water separates
from the sludge and drains down through the sand. Evapora-
tion also dries the sludge and will cause it to crack.
When the sludge has formed cracks clear to the sand, it may
then be removed by hand with forks. The one major drawback
of sand beds is that heavy equipment, such as a skip loader,
cannot be used because the weight could damage the under-
drain system. Also the scraping action could mix the sand with
the gravel or remove some of the sand with the dried sludge.
The sand would then have to be replaced.
Some operators lay 2" x 12" boards across the sand for
wheelbarrows or light trucks and fork the sludge cake into them
to haul to a disposal site. The dried sludge cake is normally
three to six inches (8 to 15 cm) thick and is not heavy unless a
large amount of grit was present in the sludge The operator
calculates the amount of cake in cubic feet by the depth of the
dry sludge cake and surface area of the bed. The total dry
pounds is arrived at from the total solids in the sludge samples
when the sludge was drawn.
Dried sludge makes an excellent soil conditioner and a low-
grade fertilizer. However, in many states air-dried digested
sludge may only be used on lawns, shrub beds, and orchards.
It cannot be used on root crop vegetables unless heat dried (at
1450°F or 800°C), or unless it has been in the ground that the
crop is to be planted in for over one year. Always check with
the state or local health department before dried sludge is used
on a food crop.
If a bed of "green" sludge (partially digested) is accidentally
drawn, it will require special attention. The water will not drain
rapidly, odors will be produced, and the water held provides an
excellent breeding ground for nuisance insects. Flies, rat-tail
maggots, psychoda flies, and mosquitoes will breed profusely
in this environment. An application of dry lime spread over the
bed by shovel, and a spraying of a pesticide, is beneficial. The
sludge from such a bed should never be used for fertilizer.
Dry sludge cake will burn at a slow smoldering pace, pro-
ducing quite an offensive odor; therefore, don't allow it to catch
fire.
WARNING
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-------
164 Treatment Plants
12.70E What should you do to the sludge draw-off line after
sludge is applied to the drying bed?
12.70F Why should heavy equipment such as skip loaders
not be used to remove dried sludge from a sand
drying bed?
12.70G What is the volume of dry sludge in a bed 100 feet
long and 25 feet wide if the dried sludge is six inches
thick? How many two cubic yard dump truck loads
would be required to haul away this sludge?
12.70H If green sludge (partially digested) accidentally was
applied to a drying bed, how would you handle this
situation?
12.71 Blacktop Drying Beds (See Fig. 12.25)
This type of bed has become prevalent in the past few years
and has worked well with anaerobically digested sludges, if
designed properly. The bed is made of blacktop or asphalt with
both sides sloping gradually to the center to a one-foot (0.3 m)
wide drain channel. The drain channel runs the full length of
the bed with a three- or four-inch (75 or 100 mm) drain line on
the bottom. The drain line is covered with rock, gravel, and
sand as in a sand bed. The drain line usually has a cleanout at
the upper end, and a control valve on the discharge end.
When the bed is to be used, the cleanout on the drain line is
removed, the line is flushed with clear water, and the cleanout
cover replaced. The drain line valve should be closed and the
drain line and drain channel should be filled with water to the
top of the sand, so that the sand is not sealed with sludge.
Sludge is then admitted to the bed. Sludge is then applied to
the bed until it is between 18 to 24 inches (45 to 60 cm) deep.
Some plants have operated successfully without pre-filling the
collection system with water.
The sludge is sampled in the same way as when using a
sand bed, except one additional sample is taken in a glass jar
or beaker and set aside. By watching the jar of sludge, you can
observe at some time during the first 24 to 36 hours that the
sludge will rise to the top, leaving liquor on the bottom. This is
primarily caused by the gas in the sludge. (Later, the sludge
will again settle to the bottom and the liquor will be on the
surface.) The drain valve on the drying bed should be opened
when the sludge separates and rises to the top of the jar. The
liquor collected in the sludge bed drains is normally returned to
the primary clarifiers.
After the sludge has started to crack and has a crust, drying
time may be reduced by driving a vehicle through the bed to
mix the sludge. When the cake is dry, a skip loader is used to
clean the bed.
Blacktop beds may be able to handle two to three times as
much sludge as sand beds in a given period of time, because
of the ability to use mechanical equipment to mix the drying
sludge, to expose the sludge to the atmosphere and to clear
the bed of dried sludge.
12.72	Sludge Lagoons
Sludge lagoons are deep ponds that normally hold anaero-
bically digested sludge and, in some instances, supernatant.
Digested sludge is drawn to the lagoon periodically and may
require a year or two to fill. When the lagoon is full, sludge is
discharged into another lagoon while the first one dries. This
drying period can require a year or two before the sludge is
removed. Some large cities have used lagoons for many
years, avoiding the use of covered secondary anaerobic diges-
tion tanks.
QUESTIONS
Write your answers in a notebook and then compare your
answers with those on page 178.
12.71 A How would you attempt to reduce drying time in
blacktop beds?
12.72A How does a sludge lagoon operate?
12.73	Withdrawal to Land
Wet sludge (either aerobically or anaerobically digested) can
be spread on land to reclaim the land or on farm land and
ploughed in as a soil conditioner and fertilizer. Used with la-
goons this gives a flexible system. This is an excellent method
of sludge disposal wherever applicable, because it returns the
nutrients to the land and completes the cycle as intended by
nature.
Transporting sludge to the disposal site is accomplished by
tank truck or pipeline. The application of wet sludge to the land
depends upon the topography and the crop to be raised on that
land. When applied to grass or low ground cover crops, appli-
cation may be by spraying from the back of the tank truck while
driving over the land, by the use of irrigation piping, or by
shallow flooding.
The best method, but most costly, is leveling the land, con-
structing ridges and furrows, and then pumping the sludge
down the furrows similar to irrigation practices used in arid
regions. This method is not only capable of reclaiming land
unsuitable for growing plants and trees, but may yield crops
equal to or greater than those raised with commercial fertiliz-
ers.
Some precautions that must be practiced with this method of
sludge disposal include:
1.	Never apply partially digested ("green") sludge or scum.
2.	Residential areas must not be located near land disposal
sites.
3.	Land disposal sites must not be located on a flood plain
where the sludge may be washed into the receiving waters
during flooding.
4.	Domestic water wells must not be located on the land re-
ceiving the sludge.
5.	Root crop vegetables must not be grown on the land.
6.	Cooperation with the landowner as to application time, dry-
ing, and covering must be guaranteed.
7.	Access to the land during wet weather must be provided.
12.74	Mechanical Dewatering
In plants where large volumes of sludge are handled and
drying beds are not feasible, mechanical dewatering may be
used. Mechanical dewatering falls into two methods: vacuum
filters and centrifuges. Each is capable of reducing the mois-

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Sludge Digestion 165
BED DRAIN LINE RETURN TO PLANT HE ADWORKS
1
==j»C.O.
BED 1
BED 2
RED 3
BLACK
DRAIN
LINE AND
GRAVEL
SLUDGE
NLET
VALVE
DRAIN
LINE
VALVE
SLUDGE LINE FROM DIGESTERS
ENTRANCE RAMP WITH REDWOOD STOP LOG
PLAN VIEW
PLANT MIX 9LACKT0P ^
^	PEA GRAVEL	—EH—DRAIN LINE	Jji
SLUDGE LINE
CROSS SECTION ONE BED
Fig. 12.25 Blacktop drying bed

-------
166 Treatment Plants
ture content of sludge by 60 to 80 percent leaving a wet, pasty
cake containing 20 to 40 percent solids. This cake may then be
disposed of in a sanitary landfill, dried in furnaces for fertilizer,
incinerated to ash in furnaces or wet oxidation units, or aerobi-
cally composted and used as a fertilizer.
72.740 Vacuum Filters (Figs. 12.26 and 12.27)
For aerobically or anaerobically digested sludge to be dewa-
tered by this method usually requires a conditioning of the
sludge by the addition of chemicals. Elutriation (e-LOO-tree-
A-shun) is the washing of the digested sludge in plant effluent
in a suitable ratio of sludge to effluent. Elutriation may be ac-
complished in from one to three separate tanks, similar to
small rectangular clarifiers. The sludge is pumped to the elutri-
ation tank and mixed with plant effluent. Next this mixture is
admitted to the other tanks to establish a counter-current
wash. The sludge is then allowed to settle and is collected by
flights and pumped to the next elutriation tank. After one to
three washings it is then pumped to the conditioning tanks. The
main purpose of the elutriation tanks is to remove the fine
sludge particles which require large amounts of chemicals for
coagulation. It also removes amino acids and salts which may
have a small coagulant demand. After elutriation the sludge
will react with the chemicals better and produce better cake.
The elutriate (effluent from elutriation tanks) is returned to the
primary clarifiers and may result in a very heavy recirculating
load since it is chiefly fine solids. Many treatment plants have
discontinued the practice of elutriation. Although the process
may save approximately $2 per ton of dry solids handled on
chemical costs, the costs are excessive for treating the elu-
triate (wash water) in the biological treatment processes. Other
problems from elutriation include odors and the adverse im-
pact of the recycled suspended solids on the other treatment
processes and the plant effluent.
Sludge conditioning is accomplished by the addition of vari-
ous coagulants or flocculating agents such as ferric chloride,
alum, lime, and polymers. In the conditioning tank the amount
of chemical solution added is normally established by labora-
tory testing of sludge grab samples by adding various chemical
concentrations to the grab samples to obtain a practical filtra-
tion rate by vacuum with a Buchner funnel. This test estab-
lishes the operating rate for the chemical feed pumps or
rotameters from the chemical head tanks, which is normally
less than 10 percent of the dry sludge solids rate to the condi-
tioning tank. (Both rates could be in pounds per 24 hours.) In
this tank the chemical is mixed into the sludge by gentle agita-
tion for several minutes. The conditioned sludge then flows to
the filter bath where it is continuously and gently agitated. After
operation has started, chemical feed is regulated according to
cake appearance and behavior.
Filter drums are 10 to 18 feet (3 to 5.5 m) in diameter, and 12
to 20 feet (3.5 to 6 m) in length. They may use cloth blankets of
dacron, nylon, or wool, or use steel coilsprings in a double
layer, to form the outer drum covering and filter media. The
drum inside is a maze of pipe work running from a metal
screen and wood surface skin, and connecting to a rotating
valve port at each end of the drum.
Cloth blankets are stretched and caulked to the surface of
the filter drums with short sections of 1/4 inch (6 mm) cotton
rope at every screen section. The sides of the blanket are also
stretched and stapled to the end of the drums. The NAP of
the blanket should be out. After the blanket is stretched com-
pletely around the drum, it is then wrapped with two strands of
1/8-inch (3 mm) stainless steel wire, approximately 2 inches (5
cm) apart for the full length of the drum.
The installation of a blanket may require several days, and it
lasts from 200 to 20,000 hours. The life of the blanket depends
greatly on the blanket material, conditioning chemical,
backwash frequency, and acid bath frequency. An improper
adjustment of the scraper blade, or accidental tear in the blan-
ket, will usually require its replacement.
Both cloth blankets and coil springs filters require a high
pressure wash after 12 to 24 hours of operation, and in some
instances, an acid bath after 1000 to 5000 operating hours.
The filter drum is equipped with a variable speed drive to
turn the drum from 1/8 to 1 rpm. Normally, the lower rpm range
is used to give the filter time to pick up sufficient sludge as it
passes through the conditioned sludge tub under the filter.
Normally less than 1/5 of the filter surface is submerged in the
tub and pulling sludge to the blanket or springs by vacuum to
form the cake mat. As that area passes through the con-
ditioned sludge, the vacuum holds a layer 1/8 to 1/2 inch (0.3 to
1.2 cm) thick of sludge to the media, and continues to pull the
water from the sludge to approximately 210 degrees from the
bottom point of the filter after it leaves the vat. This is the drying
cycle. At this point the vacuum is released and a light air pres-
sure (3.0 psi or 0.2 kg/sq cm) is applied to the inside of the
blanket, lifting the sludge so that it falls from the blanket into a
hopper or conveyor belt. The drum then rotates past a scraper
blade to remove sludge that did not fall. The applied air is then
phased out as that section starts into the filter tub, and vacuum
is applied in order to pick up another coating of sludge.
The thickness of the sludge cake and moisture content de-
pend upon the sludge, chemical feed rate, drum rotation
speed, mixing time, and condition of the blanket or coil springs.
A filter may blank out (lose sludge cake) for any of the above
reasons or due to the loss of vacuum or filtrate pumps. Filtrate
is the liquor separated from the sludge by the filter; it is re-
turned to the primary clarifiers.
QUESTIONS
Write your answers in a notebook and then compare your
answers with those on page 178.
12.73A What are some of the advantages of applying
sludge to land?
12.74A How is sludge disposed of in many large plants or
areas where drying beds are not feasible?
12.74B How would you prepare digested sludge for drying
by vacuum filtration?
12.74C How would you determine the chemical feed rate to
condition sludge?
12.74D What factors influence the life of a filter blanket?
12.741 Centrifuge
Centrifuges are gaining in popularity for dewatering raw or
primary sludges for furnaces or incineration units. Their use
on digested sludge is becoming more widespread. Most di-
gested sludges are conditioned with polymers before being
fed to a centrifuge.
Centrifuges are various sized cylinders that rotate at high
speeds. The sludge is pumped to the center of the bowl where
centrifugal force established by the rotating unit sepa-
rates the lighter liquid from the denser solids. The CEN-
2* Nap. The soft, fuzzy surface of the fabric.

-------
Fig.12.26 Vacuum filter
(Permission of Komline-Sanderson Engineering Corporation)

-------
EXTERNAL PIPING
DRUM-
FILTER
VALVE
DRUM DRIVER
COIL SPRINGS
WASH HEADERS
CAKE
DISCHARGE
AGITATOR
DRIVE
AGITATOR
INLET 1 DRAIN-
SLUDGE LEVEL
o>
00
99
3
CD
u
5"
3
r+
(ft
Fig. 12.27 CoiHifter elevation
(Permission of Komtne-Sanderson Engineering Corporation)

-------
Sludge Digestion 169
TRATE25 is returned to the primary clarifiers, and the sludge
cake is removed to a hopper or to a conveyor for disposal.
The feed rate, pool depth, centrifuge rpm, and other factors
determine the condition of the discharge cake or slurry and
the quality of centrate. The centrate usually contains a high
amount of suspended solids that become difficult to handle in
the primary clarifiers and digesters. A large amount of grit in
the sludge greatly increases the wear rate on the centrifuge.
Similar to the wash water from the elutriation process, the
suspended solids in the centrate from centrifuges also exerts
a difficult load on biological treatment processes.
QUESTIONS
Write your answers in a notebook and then compare your
answers with those on page 178.
12.74E Centrifuges are commonly used to dewater what
types of sludges?
12.74F How would you regulate the condition of the sludge
cake from a centrifuge?
12.8 REVIEW OF PLANS AND SPECIFICATIONS
Operators should be given the opportunity to review the con-
tract plans and specifications to become knowledgeable about
proposed treatment processes. However, it is just as important
that operators participate in the design of the system whenever
possible. Operators can supply information about specific re-
quirements for effective and safe operation and maintenance
of treatment processes.
In a sludge digestion system, the following areas are among
those the operator should carefully examine when reviewing
plans and specifications. The operator should look for those
items that are important for proper operation and maintenance
and ask questions on unclear or confusing items. You must
realize that many items may not be shown in particular detail
on the plans, but will be described fully in the specifications.
A.	Generally review the specifications with regard to design
loading rates (peak and average) and check with any plant
operational history. Check:
1.	Equipment details regarding sizes, capacities, flow
rates, pressure, horsepower, efficiencies.
2.	Performance requirements or capabilities.
3.	Paints and protective coatings.
4.	Instrumentation - remote and local control board items
and recorders provided.
5.	Equipment warranties and responsibility for accep-
tance testing.
6.	Adequate supply of equipment operation and mainte-
nance manuals.
7.	Adequate number of operator and maintenance per-
sonnel training hours.
B.	In examining the plans, emphasize those areas having a
direct influence on plant operation and maintenance. For a
digestion system, the following items are recommended
for review.
1.	Examine the general site layout and make sure of
adequate access for maintenance equipment and
personnef. If overhead electrical power and telephone
lines are involved, note location and make sure of
proper clearance for any boom crane.
2.	Note location and sufficiency of power outlets and
washwater faucets.
3.	Carefully trace the piping flow scheme and examine
all valve placements and ability to route flow. Examine
operation under automatic and manual mode.
4.	Check for adequate access to all valves and piping for
maintenance and repairs. Give particular attention to
pipeline cleaning.
5.	If pump or other heavy equipment is located in under-
ground galleries, check for provisions for removal.
6.	Check for adequate backup or standby raw sludge
pumps.
7.	Examine the digester hopper configuration and suita-
bility for cleaning. Note provisions for adequate venti-
lation and access during cleaning. Determine how
sludge is transferred from the hoppers. Note provi-
sions for line cleaning.
8.	Determine how the raw sludge flow is to be meas-
ured. Check if the sludge pump is to be controlled by
timers, sludge density, clarifier blanket level, or some
combination thereof.
9.	Note how the digester gas is to be measured and
check for adequate liquid traps and provisions for
cleaning.
10.	Check for location, size and type of sampling ports.
11.	Examine the digester heating system. If heat ex-
changers are used, check for cleaning access. Note
the boiler operation and provision for temperature
control.
12.	Examine the mixing system. If a propeller mixer is
used, note provisions for removing the gear box or
entire unit.
13.	Examine the supernatant line and its control. Deter-
mine the number of sludge draw-off points.
14.	Check for combustible LRC gas analyzers and their
location in galleries or closed areas.
15.	Carefully study the digester system (Fig. 12.6, page
108) for your plant and be sure the sediment and drip
traps and flame traps are properly located and that
none are missing.
12.9 ADDITIONAL READING
1.	MOP 11, Chapter 18, "Anaerobic Sludge Digestion" and
Chapter 19, "Aerobic Sludge Digestion."
2.	NEW YORK MANUAL, Chapter 8, "Sludge Treatment and
Disposal" and Chapter 9, "Gas from Sludge Digestion."
3.	TEXAS MANUAL, Chapter 17, "Sludge Conditioning and
Thickening," Chapter 18, "Separate Sludge Digestion,"
Chapter 19, "Sludge Drying Beds" and Chapter 20,
"Sludge Disposal."
25 Centrate. The water leaving a centrifuge after most of the solids have been removed.

-------
170 Treatment Plants
4.	ANAEROBIC SLUDGE DIGESTION, WPCF Manual of
Practice No. 16, Water Pollution Control Federation, 2626
Pennsylvania Avenue, N.W., Washington, D.C. 20037.
Price $3.50 to members; $7.00 to others. Indicate your
member association when ordering.
5.	SLUDGE DEWATERING, WPCF Manual of practice No. 20,
Water Pollution Control Federation, 2626 Pennsylvania Av-
enue, N.W., Washington, D.C 20037. Price $3.00 to mem-
bers; $6.00 to others. Indicate your member association
when ordering.
6.	Dague, Richard R., "Digester Control," J. Water Pollution
Control Federation, Vol. 40, No. 12, p. 2021 (December
1968).
7.	OPERATIONS MANUAL - ANAEROBIC SLUDGE DIGES-
TION. EPA 430/9-76-001, Environmental Protection
Agency, Municipal Operations Branch, Office of Water Pro-
gram Operations, Washington, D.C. 20460. (February
1976). Available from Superintendent of Documents, U.S.
Government Printing Office, Washington, D.C. 20402
USGPO No. 055-001-01075-3. Price $3.25.
END OF LESSON 6 OF 6 LESSONS
on
SLUDGE DIGESTION AND SOLIDS HANDLING
Please answer the discussion and review questions before
continuing with the objective test.
DISCUSSION AND REVIEW QUESTIONS
Chapter 12. SLUDGE DIGESTION AND SOLIDS HANDLING
(Lesson 6 of 6 Lessons)
Write the answers to these questions in your notebook be-
fore continuing. The question numbering continues from Les-
son 5.
29.	What types of sludges are treated by aerobic digesters?
30.	What kind of sludge should be placed on a sand drying
bed?
31.	What precautions should be taken when applying sludge
to a drying bed?
32.	What are the advantages of a blacktop drying bed over a
sand drying bed?
33.	Why have some plants discontinued elutriation?
34.	What are some of the operational problems encountered
in using a centrifuge to dewater sludge?
PLEASE WORK THE OBJECTIVE TEST NEXT.
12.10 Metric Calculations
This section contains the solutions to all problems in this
chapter using metric calculations.
12.100 Conversion Factors
ft x 0.3048
= m
m x 3,281
= ft
lb x 0.454
= kg
kg x 2.205
= lb
gal x 3.785
= liters
liter x 0.264
= gal
MGD x 3785
cu m/day x 0.000264
GPM x 0.063
LI sec x 15.85
cu ft X 0.02832
cu m x 35.315
1000 L
1 L
= cu m/day
= MGD
= LI sec
= GPM
= cu m
= cu ft
= 1 cu m
= 1 kg
12.101 Problem Solutions
FROM SECTION 12.21 STARTING A DIGESTER
1. Calculate the volume of seed sludge for a digester based
on digester capacity.
Known	Unknown
Diameter, m	= 12 m	Seed Sludge, cu m
Depth, m	= 6 m
a. Determine digester tank volume.
Tank Volume,
cu m
—	(Diameter, m) x Depth, m
4
—	(12 mfx6m
4
678.6 cu m

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Sludge Digestion 171
Seed Volume,
cu m
b. Calculate seed volume. Assume seed required to be
25 percent or Va of the digester tank volume.
= Tank Volume, cu m x
Portion Volume Seed
= 678.6 cu m x 0.25
= 170 cu m
2. Calculate the volume of seed sludge for a digester based
on raw sludge added to the digester.
Unknown
2000 {./day Seed Sludge, cu m
= 6%
= 68%
Known
Raw Sludge,
liters/day
Raw Sludge
Solids, %
Volatile, %
Seed Sludge
Solids, %	=10%
Volatile, %	=50%
Specific Gravity	= 1.08
Digester Loading, k« VM/daV = 0 05 kg VM added/day
kg under dig. kg VM under digestion
a.	Find the kilograms of volatile matter pumped to diges-
ter per day.
Volatile = Raw Sludge _Lxl^x Solids' % x Votetlte- %
Matter	day 1L 100%	100%
Pumped,
kg/day = 2,000 L x 1 k0 x 6% x 68%
day 1L 100% 100%
= 81.6 kg/day
b.	Find the kilograms of seed volatile matter needed.
0.05 kg VM added/day = 81.6 kg VM added/day
1 kg VM digester	Seed, kg VM
Seed, kg VM = 81.6 kg VM added/day v1ltgVM
0.05 kg VM added/day
= 1632 kg VM
c.	Find the volume of seed sludge needed in cubic me-
ters.
Seed Sludge, = Seed, kg VM x 1 cu m x 100% x 100%
00 m	Specific Gravity 1000 kg Solids, % VM, %
_ 1632 kg VM x 1 cum x 100% x 100%
1.08 1000 kg 10% 50%
- 30 cu m
FROM SECTION 12.23 NEUTRALIZING A SOUR DIGESTER
1. How much lime should be added to a sour digester?
Known	Unknown
Volatile Acids,
mgIL
(Acetic Acid)
Tank Volume, cu m =* 700 cu m
¦ 2300 mgIL Lime Required, kg
Ca(OH)a
a. Calculate the lime required (Ca(OH)2) in kilograms.
Lime Required, = Vol Acids, !!!£ x Tank Vol, cu m x
kg	L
1 kg
1000 L
1,000,000 mg 1 cu m
= 2300 ID®, x 700 cum v 1 k9 x 1000 L
L	1,000,000 mg 1 cu m
= 1610 kg
FROM SECTION 12.3 ANAEROBIC DIGESTION CONTROLS
AND TEST INTERPRETATION
F. VOLUME OF SLUDGE
1. How much sludge is pumped per stroke by a piston pump?
Known	Unknown
= 25 cm
Piston Diameter,
cm
Piston Stroke,
cm
Sludge Pumped,
liters/stroke
= 8 cm
a. Calculate volume of cylinder in cubic meters.
Volume, cu m = JL. (Diameter, m)2 x (Stroke, m)
4
_ it (25 cm)'
4 (100 cm/m)2
= 0.0039 cu m
8 cm
100 cm/m
b. Determine volume of cylinder in liters.
10001.
Volume, liters = Volume, cu m x.
= 0.039 cu m
= 3.9 liters/stroke
1 cu m
1000 L
1 cu m
G. RAW SLUDGE
1. Determine kilograms of sludge pumped and kilograms of
volatile solids.
Known
Unknown
Sludge Pumped, = 10,000 liters Dry Solids, kg
liters
Total Solids, % = 6.5%	Volatile Solids, kg
Volatile Content, % = 68%
a. Calculate the kilograms of dry solids pumped.
Dry Solids, - Sludge Pumped, x Solld8'% x 1 kfl
kg	liters	100% 1 liter
- 10,000 liters x 65% x 1 kfl
100% 1 liter
« 650 kg dry solids pumped

-------
172 Treatment Plants
b. Calculate the kilograms of dry solids pumped.
Volatile = Total Dry Solids, kg x Volatile Content, %
= 650 kg x 680/0
Solids, kg
100%
100%
= 442 kg of volatile solids pumped
H.	RECIRCULATED SLUDGE
I.	Determine the percent reduction of volatile matter as a re-
sult of sludge digestion.
Known
Raw Sludge VM, % = 68%
Digested Sludge = 54%
VM, %
Unknown
Volatile Matter
Reduction, %
a. Calculate the reduction of volatile matter as a percent.
VM Reduction, % =
In - Out
x 100%
In - (In x Out)
0.68 - 0.54
0.68 - (0.68 x 0.54)
x 100%
0.14
x 100%
0.68 - 0.37
= 0.45 x 100%
= 45%
K. COMPUTING DIGESTER LOADINGS
1. Determine the digester loading in kilograms of volatile mat-
ter per day per cubic meter of digester.
Known
Unknown
Volatile Matter, = 600 kg/day Digester Loading,
kg/day	kg/day/cu m
Digester Volume, = 800 cu m
cubic meters
a. Calculate the digester loading in kilograms of volatile
matter per day per cubic meter of digester capacity.
Digester	= Volatile Matter Added, kg/day
SdaJ/cu m	Digester Volume, cum
_ 600 kg/day
800 cu m
= 0.75 kg/day/cu m
2. Determine the kilograms of solids (digested sludge) that
should remain in the digester to provide a seed sludge.
Known	Unknown
Volatile Matter = 600 kg/day Dig SI in Storage, kg
Added, kg/day
Diar - »«"*>»
kg Dig Sl/kg 1 kg VM/day
VM/day
a. Calculate the digested sludge in storage in kilograms.
Dig SI in _ Volatile Matter x 10 kg Dig SI in Storage
Storage, kg Added, kg/day 1 kg VM added/day
= 600 kg/day x 10 kg Dig SI in Storage
1 kg VM/day
- 6000 kg old sludge in storage on a dry
solids basis
3. Determine the digester loading in kilograms of volatile mat-
ter destroyed per day per cubic meter.
Known	Unknown
Raw Sludge Pumped, = 10,000 liters/day Digester Loading,
liters/day	kg VM/day/cu m
Total Solids, % = 6.5%
Volatile Matter, % = 68%
Volatile Reduction, % = 50%
Digester Volume, = 700 cu m
cu m
a. Calculate the kilograms of volatile matter destroyed per
day per cubic meter.
Sludge v Solids, % y VM, % x VR, % x 1 kg
Digester	2X 1°°% 1°°% 100% ^
Loading,	=				
kg VM/day/cu m	Digester Volume, cu m
10,000 L v 6.5% y 68% y 50% x 1 kg
= day 100% 100% 100% liter
790 cu m
= 221 kg VM/day
700 cu m
= 0.32 kg VM/day/cu m
L. COMPUTING GAS PRODUCTION
1. Determine the gas production in cubic meters per day for
each kilogram of volatile matter destroyed per day.
Unknown
= 170 cu m/day Gas Produced,
cu m/kg VM destroyed
= 230 kg/day
Known
Gas Produced,
cu m/day
Volatile Matter
Destroyed,
kg/day
a. Calculate the gas produced in cubic meters per kilo-
gram of volatile matter destroyed.
Gas Produced,
cu m/kg
, Gets Produced, cu m/day
VM Destroyed, kg/day
, 170 cu m gas/day
230 kg VM Destroyed/day
: 0.74 cu m gas/kg VM Destroyed

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Sludge Digestion 173
M. SOUDS BALANCE
1. Calculate the solids balance in the digester.
Known	Unknown
INPUT TO DIGESTER	Solids Balance
Raw Sludge, liters/day = 10,000 liters/day
Total Solids, %	= 6.5%
Volatile Matter, % = 68%
DIGESTER OUTPUT or INPUT TO DRYING BED
Total Solids, %	= 4.5%
Volatile Matter, % = 54%
a. Calculate the kilograms of total solids, water, volatile
and inorganic solids pumped into digester.
Total solids to digester.
Dry Solids, = Raw Sludge, v Solids, % v 1 kg
kg/day	liters/day 100% TiiteT
= 10,000 llters x 6 5% x 1 kfl
day 100% 1 liter
= 650 kg/day
Total water and solids to digester.
Water & = Total Solids, kg/day x 100%
Gas out of digester.
Solids,
kg/day
Total Solids, %
= 650 kg/day x
100%
6.5%
= 10,000 kg/day or 10,000 liters/day
Water to digester.
= Water & Solids, kg/day - Solids, kg/day
= 10,000 kg/day - 650 kg/day
= 9,350 kg/day
Water,
kg/day
Volatile solids to digester.
Volatile = Total Solids, kg/day x Volatile Matter, %
Solids,
kg/day = 650 kg/day x _68%^
100%
= 442 kg/day
Inorganic solids to digester.
Inorganic = Total Solids, kg/day x Volatile Solids, kg/day
= 650 kg/day - 442 kg/day
= 208 kg/day
Calculate the percent reduction in volatile matter in the
digester to find the kilograms per day of gas produced
during digestion.
In - Out
VM
Reduction, In - (In x Out)
%
0.68 - 0.54
x 100%
0.68 - (0.68 x 0.54)
45%
x 100%
Gas,
kg/day
= Volatile Solids, x VM Reduction, %
kg/day	—
100%
= 442 kg/day x
= 200 kg/day
45%
100%
Determine the kilograms of total, volatile, and inorganic
solids removed from the digester to the drying bed as
digested sludge.
Volatile
Solids,
kg/day
= Volatile Solids to - Volatile Solids Out as
Digester, kg/day	Gas, kg/day
= 442 kg/day - 200 kg/day
= 242 kg/day
Total solids to drying bed.
Total	= Volatile Solids, kg/day x 100%
Solids,
kg/day
Volatile Solids, %
_ 242 kg/day x 10Q%
54%
= 448 kg/day
Inorganic solids to drying bed.
Inorganic = Total Solids, kg/day - Volatile Solids, kg/day
Solids,
kg/day = 448 kg/day - 242 kg/day
= 206 kg/day NOTE: Almost same as 208 kg/day
to digester.
Total solids and water to drying bed.
Water & = Total Solids, kg/day x 100%
Solids,	Solids, %
kg/day
= 448	v inn%
4.5%
= 9960 kg/day
NOTE: Almost same vol-
ume as put into di-
gester because of
thinner sludge
going out.
Find total kilograms of water to drying bed and compare
amounts of water into and out of digester.
Water to drying bed.
= Water & Solids, kg/day - Solids, kg/day
= 9960 kg/day - 448 kg/day
= 9512 kg/day
or say = 9500 kg/day
Compare amounts of water in and out of digester.
Water = Water Out, kg/day - Water In, kg/day
Change,
kg/day = 9500 kg/day - 9350 kg/day
= 150 kg/day drawdown in digester
Water,
kg/day

-------
174 Treatment Plants
In this case, more water was withdrawn in the thin sludge
than was added with the thick sludge. No supernatant was
withdrawn from the digester or recycled. All of the recycle ma-
terial must come from the dewatering operation.
DRYING BED OUTPUT
Dried residual removed, 2 kg water per 1 kg solids or 33
percent solids.
Determine the kilograms of water removed per day with the
dried solids and the kilograms per day of drainage water recy-
cle to the plant.
Water in solids.
Water in = Total Solids, kg/day x 2 kg/day water
Solids,	1 kg/day solids
kg/day = kg/(Jay x 2 kg/day water
„„„ ,	1 kg/day solids
= 896 kg/day	'
Drainage water recycled to plant.
Recycle = Water to Drying - Water in Solids,
Water Beds, kg/day	kg/day
kg/day
= 9500 kg/day - 896 kg/day
= 8604 kg/day (less evaporation)
SUMMARY
Constitutent
Total Solids, kg/day
Volatile Solids, kg/day
Inorganic Solids, kg/day
Water, kg/day
Gas Out, kg/day
Input to Input to
Digester Drying Bed
650
442
208
9,350
448
242
206
9,500
200
Recycle
to Plant
8,604
SUGGESTED ANSWERS
Chapter 12. SLUDGE DIGESTION AND SOLIDS HANDLING
Answers to questions on page 102.
12.01 A Raw sludge must be digested so wastewater solids
may be disposed of without creating a nuisance.
12.01B During anaerobic digestion the organic solids are
broken down to other stable products, thus reducing
the solids volume and releasing the water from the
solids.
12.01 C Some of the important factors in controlling sludge
digestion include regulation of food supply (organic
solids), temperature, mixing, and volatile acid/
alkalinity relationship.
Answers to questions on page 102.
12.1 OA Plug type valves are used in sludge lines because
they are less apt to become fouled up by rags or
other materials than other types of valves.
12.10B A positive displacement pump will continue to build
pressure with each revolution until the safety devices
shut the pump off, the motor stalls and overheats, or
either the pump or the pipe breaks.
12.10C A sludge line should never be sealed at both ends
because sludge in it can produce gas and create
pressures high enough to break the line or valves.
Answers to questions on page 103.
12.11 A Normally the digester roof is designed to contain a
maximum operating pressure. If the pressure is ex-
ceeded, the water seal could be broken, allowing air
to enter the tank and form an explosive mixture of
gases. High gas pressures may cause structural
damage to the tank in severe cases.
12.11B Fixed cover digesters must be equipped with pres-
sure and vacuum relief valves to break a vacuum or
bleed off excessive pressure to protect the digester
from structural damage.
12.11C Floating cover. ADVANTAGES: Fluctuates with
sludge level and gas pressure in digester. Less
danger of explosive mixtures than in fixed cover di-
gester. Better control of supernatant withdrawal and
scum blanket.
12.11D Mixing recirculated digester sludge with raw sludge
provides immediate seeding of the raw sludge with
anaerobic bacteria from the digester.
END OF ANSWERS TO QUESTIONS IN LESSON 1.
Answers to questions on page 109.
12.12A The two main gaseous components of digester gas
are methane and carbon dioxide.
12.12B Digester gas is used to mix digesters; for fuel to heat
digesters and plant buildings; and to run engines on
pumps, blowers, and generators.
12.12C Digester gas must be handled with extreme caution
due to its ability to burn and explode.
Answers to questions on page 109.
12.12D The pressure relief valve is adjusted by placing the
correct amount of lead weights on the pressure relief
pallet and then checking the digester pressure with a
water manometer to insure the proper setting.
12.12E The water seal in a digester could be broken by
either excessive gas pressure or a vacuum in the
tank.
12.12F The operation of either the pressure or vacuum relief
valves can create an explosive condition due to di-
gester gas mixed with air.

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Sludge Digestion 175
Answers to questions on page 109.
12.12G 1. Cut off the gas flow in that line.
2.	Put out all flames and pilot lights in the area.
3.	Remove end housing and slide out cartridge con-
taining flame arrester baffles.
4.	Clean the baffles in solvent and dry.
5.	Reinstall cartridge and replace end plate.
6.	Return pressure to gas line and soap test for gas
leaks.
12.12H Thermal valves should be checked at least once a
year to make sure that the stem and valve seat are
clean and the valve will operate when needed.
Answers to questions on page 117.
12.121 A sediment trap should be drained as often as nec-
essary to prevent water from entering the gas lines,
which may be from one to four times per day. Actual
frequency of draining traps depends on location of
trap in gas system, temperature changes and diges-
ter mixing system.
12.12J Drip or condensate traps should be installed to keep
water out of the gas lines where it would restrict gas
flows.
12.12K Automatic drip and condensate traps may stick
open, venting gas to atmosphere and creating a
hazardous condition.
12.12L The gas pressure of the digester system may be
adjusted by connecting a manometer to the gas sys-
tem and adjusting the regulator to hold eight inches
(20 cm) of water column of gas pressure on the di-
gester.
12.12M The pilot flame in the waste gas burner should be
checked daily to prevent unburned waste gas from
being vented to the atmosphere and creating a po-
tentially hazardous condition.
Answers to questions on page 129.
12.13A A digester should have a special sampling well in
order that the tank contents may be sampled at vari-
ous depths without venting the digester gas to at-
mosphere.
12.14A If the temperature of the hot water in the heating coils
of this type of heating system is maintained too high,
it will cook the sludge onto the coils, thus acting as
insulation and reducing the heat transferred.
Answers to questions on page 129.
12.15A Complete mixing greatly speeds the digestion rate by
providing the bacteria with greater access to the or-
ganic material, and retards or prevents formation of
scum blankets. Other reasons for complete mixing
include an even distribution of alkalinity, heat and
waste material products and a reduction of grit and
inert solids deposits.
12.15B Maintenance consists of compressor lubrication,
condensate drainage from the gas lines, and clean-
ing diffusers to prevent high discharge pressures.
Answers to questions on page 132.
12.15C An effective operation for breaking up scum in diges-
ters with draft tube mixers is to operate one unit
(tube) as a top suction and the other unit as a bottom
suction. The direction of flow in the tubes should be
reversed each day.
12.15D Pressure gages should be installed. A change in
pressures could indicate that the pump is not func-
tioning properly and the desired mixing may not be
taking place in the digester.
Answers to questions on page 134.
12.16A The purpose of floating covers is to provide a flexible
space for digester gas storage. Floating covers also
can keep the scum blanket submerged in the digest-
ing sludge which helps to digest the scum.
12.16B Explosive conditions are less apt to develop in diges-
ters with floating covers because the cover can drop
during sludge or supernatant withdrawal and avoid
vacuum conditions that pull air into the digester.
12.16C The annular space is the space full of digesting
sludge between the floating cover and digester side
wall.
12.16D Hazardous atmospheric conditions that could be en-
countered inside the flotation chamber of a floating
cover digester include explosive gas-air mixtures,
oxygen deficiency and toxic gases (hydrogen sul-
fide).
12.16E If a floating cover rises too high sludge can overflow
the digester walls or structural damage could occur
to the cover. If the cover drops too low and rests on
the corbels, the water seal could break and explosive
conditions could develop inside the digester.
END OF ANSWERS TO QUESTIONS IN LESSON 2
Answers to questions on page 137.
12.20A Raw sludge is normally composed of solids settled
and removed from the clarifiers or sedimentation
tanks. Scum is composed mainly of grease and other
floatable material. Waste activated sludge is the
sludge intentionally removed from the activated
sludge process and is comprised almost entirely of
the microorganisms from the activated sludge aera-
tion tanks.
12.21 A If too much raw sludge is added to the digester, the
acid fermentation predominates, which lowers the pH
of the sludge and slows down the methane fermen-
ters.
12.21B A digester will usually foam and froth when large
amounts of material have been converted by the acid
formers into food for the methane bacteria group.
Methane fermenters then produce large volumes of
gas causing the digester to foam.

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176 Treatment Plants
12.21C Find pounds of volatile matter pumped to digester
per day.
Volatile
Matter = (Vol. Sludge, gpd) (Solids, %) (Volatile, %)
Pumped,	(8.34 lb/gal)
lbs/day = (70Q ga|/day) (0.065) (0.70) (8.34 lb/gal)
= 265 lb/day
Find pounds of seed volatile matter needed.
0.05 lb VM Added/day = 265 lb VM Added/day
1 lb VM in Digester	Seed, lb VM
Seed, lb VM	= (265 lb VM Added/day) lb VM
0.05 lb VM Added/day
= 5300 lbs VM
Find gallons of seed sludge needed.
Seed Sludge, gal =
Seed, lb VM
(9 lb/gal) (Solids, %) (VM, %)
5300 lb VM
(9 lb/gal) (0.10) (0.50 VM)
= 11,800 gal
12.21D It is hazardous to start a digester when it is only
partially full due to explosive conditions created by a
mixture of air and methane in partially full digesters.
12.21 E A new digester is ready for the raw sludge rate to be
gradually increased to the full plant load when it is
producing a burnable gas.
Answers to questions on page 138.
12.22A As thick a sludge as possible may be pumped to the
digester by operating the sludge pump for several
minutes each hour to clear the sludge hopper, and at
a rate not to exceed 50 gpm.
12.22B 1. Better performance of primary clarifier.
2.	Raw sludge will be well mixed in digester.
3.	Less chance of pumping thin sludge or water to
the digester.
4.	Supernatant is returned to the plant throughout
the day, rather than in one large slug.
12.22C The pumping of thin sludge should be avoided be-
cause too much water pumped to the digester in-
creases heating requirements, reduces digester
holding time, washes buffer and seed sludge out of
the digester, and imposes a heavier supernatant load
on the plant.
Answers to questions on page 138.
12.23A Lime is added to a digester in an attempt to neu-
tralize the acids and increase the pH to 7.0.
12.23B Assume a dosage of one pound of lime per 1000
gallons of digester sludge.
Lime Dose, lbs = P'9<*ter Sludge Volume, gal
1000 gals/lb lime
_ 100,000 gal
1000 gals/lb lime
= 100 lbs of lime
12.23C Lime must be mixed into a slurry before being added
to a digester or it will settle to the bottom in lumps
which will harden and be ineffective.
12.23D Lime should be added daily until the volatile acid/al-
kalinity relationship, gas production, and pH levels
are restored.
Answers to questions on page 139.
12.24A Bacteria secrete enzymes that help break down
compounds that the bacteria in the digester may use
as food.
12.25A To control a foaming digester, stop feeding, lower the
sludge level by a foot or two for room, start mechan-
ical mixers, and wash away the foam with a hose.
12.25B To prevent foam from recurring:
1.	Maintain temperature in digester.
2.	Feed studge at regular, short intervals.
3.	Exercise caution when breaking up scum blan-
kets.
4.	Don't overdrain sludge from digester.
5.	Keep contents of digester well mixed from bottom
to top at all times.
12.26A The gas initially produced in a digester is not burna-
ble because it contains mostly C02. Generally diges-
ter gas will burn when the methane content reaches
50 percent, but for use as a fuel the methane content
should be at least 60 percent.
Answers to questions on page 141.
12.27A The purpose of the secondary digester is to allow
separation of the sludge from the water, to store di-
gested sludge, and to allow more complete digestion.
This reserve of digested sludge is needed to act as
seed sludge or buffer sludge to be transferred to the
primary digester if it becomes upset.
12.27B When raw sludge is pumped to the primary digester,
usually an equal volume of sludge from the primary
digester is transferred to the secondary digester and
supernatant is displaced from the secondary digester
back to the plant.
12.27C The level of supernatant withdrawal is selected on a
fixed cover digester by selecting the supernatant
tube that reaches the clearest supernatant zone in
the digester. On floating cover tanks, the supernatant
draw-off line is raised or lovyered to the clearest
supernatant zone in the digester.
12.28A The rate of sludge withdrawal can be determined by
watching the gas pressure on the digester that the
sludge is being drawn from and not letting the gas
pressure drop below two inches (5 cm) of water col-
umn.
END OF ANSWERS TO QUESTIONS IN LESSON 3.
Answers to questions on page 142.
12.3A The temperature of a digester may be obtained from
the digester recirculation sludge line which carries
sludge from the digester to the heat exchanger or from
the operating supernatant tube.
12.3B The volatile acid/alkalinity relationship is useful in di-
gester control because it is the first indicator that the
digestion process is starting to get out of balance and
that corrective action is necessary.

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Sludge Digestion 177
12.3C When the volatile acid/alkalinity relationship starts in-
creasing, the operator should reduce the raw sludge
feed, maintain heat at the regular level, and thor-
oughly mix the tank contents. If the volatile acids con-
tinue to increase, add seed sludge from the secondary
digester.
12.3D pH is a poor indicator because it is usually the last
indicator to change, and by the time it changes signifi-
cantly the digester is already in serious trouble.
Answers to questions on page 143.
12.3E Solids tests are run on digester sludge to determine
the pounds of sludge, the pounds of volatile sludge
available to the bacteria, the pounds of volatile sludge
destroyed or reduced, the digester loading rates, re-
ductions, and the amount of solids handled through
the system.
12.3F Volume, cu ft = Area, sq ft x Depth, ft
_ 7tD
x Depth, ft
4
= 0.785 x
[12 in -| x 4 in
12in/ft J 12 in/ft
= 0.259 cu ft
Volume, gal = 0.259 cu ft x 7.48 gals/cu ft
= 1.93732 or 1.9 gals/stroke
12.3G Gallons = 1.2 gals/rev x 2000 rev/day
= 1.2 gals x 2000/day
= 2400 gals/day
12.3H The volume of sludge pumped per day is needed to
determine:
1.	Gallons pumped per day.
2.	Pounds of dry solids/day to the digester.
3.	Estimated gallons of supernatant returned to the
plant.
4.	Volume of sludge for ultimate disposal.
Answers to questions on pages 144 and 145.
12 31 lbs' S°lldS' = Gals PumPed x% Solids x 8.34 lbs/gal
= 3000 gals x 0.05 x 8.34 lbs/gal
= 1251 pounds
Volatile
Content, = Volatile x lbs Dry Solids
lbs
= 0.70 x 1251 lbs Dry Solids
= 875.70 pounds
12.3J	D _ In - Out
P =.
x 100%
In - (In x Out)
0.70 - 0.45
0.70 - (0.70 x 0.45)
x 100%
0.25
x 100%
0.70 - 0.315
0.25
x 100%
0.385
= 0.65 x 100%
= 65% reduction of volatile matter
Answers to questions on page 146.
12.3K Total solids tests are run on the digester supernatant
to estimate the solids load being returned to the plant.
12.3L If the total solids reached 0.5 of 1 percent, sludge
should be drawn or supernatant withdrawal level
changed.
Answers to questions on page 155.
12.4A Gas line condensate traps and sedimentation traps
should be drained as required (from one to four times
per day).
12.4B The water seal is located on the center dome of fixed
cover digesters and between the tank well and cover
of floating cover digesters.
12.4C The quality of the digester supernatant is decreasing
when the solids level and COD are increasing.
12.4D The normal operation of a digester involves the follow-
ing activities:
1.	Feeding sludge to the digester,
2.	Maintaining the proper temperature,
3.	Keeping the contents of the digester mixed,
4.	Removing supernatant, and
5.	Withdrawing sludge.
Answers to questions on page 159.
12.5A Grease (scum) and grit (sand, seeds, cigarette butts)
accumulate in digesters and reduce the active volume
for digesting sludge.
12.5B When the active volume in a digester is reduced, the
amount of volatile solids destruction is decreased, gas
production is lowered, and ultimately the digestion
process will fail if the digester is not cleaned.
12.5C While a plant's only digester is being cleaned, (1) raw
sludge could be hauled to a nearby treatment plant for
processing, (2) temporarily convert an activated
sludge aeration tank to an aerobic digester, (3) con-
struct a temporary anaerobic lagoon, or (4) hold the
sludge in the primary clarifiers.
12.5D Before entering a digester, test the digester atmos-
phere for explosive conditions, toxic gases (hydrogen
sulfide) and oxygen deficiency.

mmm
*
Mmw
10
QuetfiOHt
(M ,
4
%J '0'+'

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178 Treatment Plants
Answers to questions on page 161.
12.6A Aerobic digestion is commonly used to handle waste
activated sludge because of the operational problems
encountered when a waste aerobic activated sludge
with a low solids content is placed in an anaerobic
digester.
12.6B Advantages of aerobic digestion in comparison with
anaerobic digestion include fewer operational, main-
tenance, and safety problems. Aerobic digesters do
not require mixing, heating and gas handling facilities.
Potentially explosive methane gas is not produced
and close operational control of the volatile acid/alka-
linity relationship is not necessary.
12.6C Dissolved oxygen levels in aerobic digesters should
be above 1.0 mgIL throughout the tank.
Answers to questions on pages 163 and 164.
12.70A Prior to applying sludge to a drying bed, the operator
should loosen the sand, break the clods, and level
the sand bed.
12.70B Sludge should be drawn slowly from the digester to
prevent (1) coning of the sludge, and (2) causing a
negative pressure in the digester.
12.70C To eliminate a sludge cone, open and close the valve
rapidly to "bump" the sludge in the tank. If the sludge
remains thin, stop drawing it.
12.70D Flames and smoking should not be allowed due to
the presence of methane gas which is flammable.
12.70E After sludge has been applied to the drying beds, the
draw-off line should be flushed with wafer so the sol-
ids won't cement in the line and one valve left open
so any gas produced will not rupture the line. The line
should be drained if freezing is a problem.
12.70F Heavy equipment should not be used to remove
dried sludge from a sand drying bed because the
equipment may damage the underdrain system, mix
the sand and gravel in the bed, or remove sand that
will have to be replaced.
12.70G Volume, cu ft = Length, ft x Width, ft x Depth, ft
= 100 ft x 25 ft x 0.5 ft
Volume, yards
No. of Truck
Loads
= 1250 cu ft
= 1250 cu ft
27 cu ft/cu yd
- 46.3 cubic yards of dry sludge
		Volume, yds	
Truck Capacity, yds/truck load
46.3 yds
2 yds/truck load
¦ 23.15 truck loads
23 or 24 truck loads
12.70H If green sludge were applied to a drying bed, then the
operator should apply dry lime and if allowable, an
insecticide to control odors and insects. The sludge
should be burned or buried when dried.
Answers to questions on page 164.
12.71A To reduce drying time in a blacktop drying bed, ob-
tain a separate sample of the sludge applied to the
bed. When the sludge goes to the surface of the
sample, open the drain line and slowly bleed off the
lower liquor. When the sludge begins to dry and
crack, mix the bed, thereby exposing wet sludge.
12.72A A sludge lagoon is filled and then sludge is diverted
to another lagoon. The sludge in the full lagoon is
tilled, dried, and removed.
Answers to questions on page 166.
12.73A Applying sludge to land improves the condition of the
soil and returns nutrients to the soil.
12.74A Mechanical dewatering (vacuum filters and cen-
trifuges) is used to prepare sludge for disposal in
large plants or areas where drying beds are not fea-
sible.
12.74B Digested sludge can be prepared for vacuum filtra-
tion by washing, by elutriation and conditioning with a
coagulant.
12.74C The chemical feed rate to condition sludge is deter-
mined by sampling and adding various dosages of
flocculant to the samples and running filterability
tests with a Buchner funnel.
12.74D The life of a fitter blanket is influenced by care, main-
tenance, and the type of material.
Answers to questions on page 169.
12.74E Centrifuges are used to dewater raw or primary
sludges and digested sludges for incinerators or fur-
naces.
12.74F The condition of the sludge from a centrifuge is regu-
lated by the sludge feed rate, bowl speed, and if
chemical conditioners are used, by dosage rates and
pool depth.
END OF ANSWERS TO QUESTIONS IN LESSON 6

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Sludge Digestion 179
OBJECTIVE TEST
Chapter 12. SLUDGE DIGESTION AND SOLIDS HANDLING
Please write your name and mark the correct answers on the
answer sheet as directed at the end of Chapter 1. There may
be more than one answer to each question.
1.	All sludge digesters operate in an anaerobic condition.
1.	True
2.	False
2.	Digesters easily decompose organic plastics.
1.	True
2.	False
3.	Supernatant is a liquid withdrawn from a digester.
1.	True
2.	False
4.	Supernatant from a digester goes directly to the chbrina-
tion system.
1.	True
2.	False
5.	Excess water in sludge affects digester operation.
1.	True
2.	False
6.	"Seed" sludge usually contains considerable plant seeds.
1.	True
2.	False
7.	Mixing is done in a digester by gas diffusers, propellers, or
pumps.
1.	True
2.	False
8.	The thicker a scum blanket in a digester the better it oper-
ates.
1.	True
2.	False
9.	Elutriation has to do with "washing" raw, undigested
sludge.
1.	True
2.	False
10.	Sludge should be pumped to a digester several times a
day to prevent coning of the digested sludge.
1.	True
2.	False
11.	Methane gas is the major component of digester gas from
a property operating digester.
1.	True
2.	False
12.	Digester gas may be used in the system that heats diges-
ter sludge.
1.	True
2.	False
13.	Volatile acids should be kept as high as possible in an
anaerobic digester.
1.	True
2.	False
14.	Sludge should not be withdrawn from the primary digester
unless it shows signs of bulking.
1.	True
2.	False
15.	Foaming in a digester can be caused by overfeeding dur-
ing the start-up of a digester.
1.	True
2.	False
16.	The BOD test is a good test for checking digester opera-
tion.
1.	True
2.	False
17. A "stuck" digester means sludge pipes are clogged.
1.	True
2.	False
18. Digested sludge is sometimes dried on sand beds.
1.	True
2.	False
19. Sludge will dry faster if it is put onto a sand bed before it is
completely digested.
1.	True
2.	False
20. Sludge drying beds must be covered.
1.	True
2.	False
21. Material not readily decomposed in digesters includes
1.	Fruit.
2.	Grit.
3.	Hair.
4.	Plastic.
5.	Rubber goods.
22. A positive displacement pump should never be started
against a closed valve because the
1.	Excessive pressure may damage the line, the pump, or
the motor.
2.	Pump pressure cut-off device could fail and allow ex-
cessive pressure.
3.	Sludge will be pumped back to the clarifier.
4.	Sludge wHI spM.
5.	Valve wiH swing open.

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180 Treatment Plants
23.	Flame arresters should be installed
1.	After sediment trap on gas line from digester.
2.	At waste gas burner.
3.	Before every boiler, furnace, or flame.
4.	Between vacuum and pressure relief valves and the
digester dome.
5.	In the vent of the waste gas burner.
24.	The pilot flame in the waste gas burner should be checked
daily to
1.	Be sure odorous gases are burned.
2.	Make sure it has not been blown out by the wind.
3.	Make sure proper temperatures are maintained in the
digester.
4.	Prevent explosive conditions from developing.
5.	Prevent valuable gas from escaping.
25.	The function of the water seal on the gas dome of the
digester is to keep
1.	Air from entering the digester.
2.	Digester gas from escaping the digester.
3.	Foam inside the digester.
4.	Insects and rodents out of the digester.
5.	Sludge from leaking out of the digester.
26.	The purpose of the secondary digester is to allow
1.	An opportunity for more mixing.
2.	For more sludge digestion.
3.	Storage for seed sludge.
4.	The designer to make more money.
5.	The liquids and solids in digested sludge to separate.
27.	Useful anaerobic digester control tests include
1.	BOD.
2.	DO.
3.	pH.
4.	Temperature.
5.	Volatile acid/alkalinity relationship.
28.	Sludge should be pumped from the primary clarifier to the
digester several times a day to
1.	Keep the pump from becoming clogged.
2.	Maintain better conditions in the clarifier.
3.	Permit thicker sludge pumping.
4.	Prevent coning.
5.	Prevent temporary overloading of the digester.
29.	Digester gas may be used to
1. Digest solids.
30.
31. Sludge or gas should not be removed too rapidly from the
digester because
1.	If a vacuum develops in the tank, air may be drawn in
and form an explosive mixture.
2.	If a vacuum develops in the tank, the tank may col-
lapse.
3.	The sludge drying beds may become overloaded.
4.	The waste gas burner may become overloaded.
5.	The water seal could break.
32. A scum blanket in a digester may be broken up by
1.	An ax.
2.	Burning.
3.	Increasing mixing time.
4.	Rolling back the blanket.
5.	Vigorously mixing the digester contents.
33. Sludge should be withdrawn slowly from a digester to pre-
vent
1.	Coning.
2.	Forming a vacuum in the digester.
3.	Supernatant from overloading the plant.
4.	The possibility of an explosive gas mixture developing
in the digester.
5.	The possibility of the digester cover collapsing.
34. The environment in an anaerobic digester may be con-
trolled by regulating the
1.	Air supply.
2.	Domestic water supply.
3.	Food supply.
4.	Mixing.
5.	Temperature.
35. Digester gas may be used as a fuel when the methane
content exceeds
1.	25%.
2.	35%.
3.	50%.
4.	65%.
5.	75%.
36. High volatile acid/alkalinity relationship in a digester may
be caused by
2.	Gas rats around the plant.
3.	Heat digesters.
4.	Replace oxygen in activated sludge aeration tanks.
5.	Run engines.
Sludge pumped to the digester should be as thick as pos-
sible
1.	So a scum blanket won't be formed in the digester.
2.	So large amounts of digested sludge will not be dis-
placed to the secondary digester.
3.	So the sludge will settle to the bottom of the digester.
4.	To clean the grease out of the raw sludge line.
5.	To reduce heat requirements in the digester.
1.	Adding lime.
2.	Filling the tank too full.
3.	Overloading the tank with organic material.
4.	Pumping too thin a raw sludge.
5.	Withdrawing supernatant.
37. The contents of a primary digester should be mixed to
1.	Allow solids separation.
2.	Distribute food in the tank.
3.	Keep the temperature the same throughout the tank.
4.	Prevent formation of a scum banket.
5.	Warm up the sludge.

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Sludge Digestion 181
38.	Successful digester operation depends on
1.	Analysis and application of information from laboratory
tests.
2.	Cleaning the digester at regular intervals to maintain
capacity.
3.	Keeping all the digested sludge out of the digester.
4.	Regularly checking the skimmer.
5.	Understanding what's happening in the digester.
39.	The temperature of a digester should not be changed
more than one degree F (0.5°C) per day to
1.	Allow the organisms in the digester time to adjust to the
temperature change.
2.	Allow the walls of the digester time to expand and con-
tract.
3.	Allow time for heating gas to be produced in the diges-
ter.
4.	Avoid excessive heat losses.
5.	Avoid overloading the heat exchanger.
40.	What could be happening if gas production in a digester
starts decreasing?
1.	The raw sludge volume fed to the digester is decreas-
ing.
2.	The raw sludge volume fed to the digester is excessive.
3.	The scum blanket is breaking up.
4.	The volatile acid/alkalinity relationship is decreasing.
5.	The volatile acid/alkalinity relationship is increasing.
41.	What would you do if the volatile acid/alkalinity relation-
ship started to increase in a digester?
1.	Decrease sludge withdrawal rates.
2.	Increase time of mixing.
3.	Maintain constant temperature throughout the digester.
4.	Reduce volume of raw sludge pumped to digester.
5.	Return some digested sludge.
42.	After sludge has been applied to the drying bed, the
sludge draw-off line should be
1.	Closed at both ends to keep out rodents and insects.
2.	Filled with plant effluent.
3.	Left full of sludge.
4.	Open at one end to allow gas to escape.
5.	Washed out.
43.	The following precautions must be taken when applying
sludge to a drying bed
1.	Drag a 2 x 12 board over the sludge surface to insure a
uniform drying rate.
2.	Loosen sand before applying sludge.
3.	Never smoke in the vicinity where the sludge is being
drawn.
4.	When finished, flush the draw-off line and leave one
end open.
5.	Withdraw the sludge slowly from the digester.
44.	Laboratory tests indicate that the volatile content of a raw
sludge was 71% and after digestion the content is 53%.
The percent reduction in volatile matter is
1.	25%
2.	50%
3.	54%
4.	60%
5.	68%
45.	Calculate the volatile matter destroyed (Ibs/day/cu ft) in a
20,000 cubic foot digester receiving 2,400 gallons per day
of raw sludge. The solids content is 5%, the volatile con-
tent 71 %, and the volatile solids are reduced 50% by di-
gestion.
1.	.015
2.	.018
3.	.020
4.	.023
5.	.025
REVIEW QUESTION
46. A rotating biological contactor treats a flow of 1.9 MGD
with an influent soluble BOD of 95 mg/L. The surface area
of the media is 500,000 square feet. What is the organic
loading?
1.	3.0 lbs BOD/day/1000 sq ft
2.	4.0 lbs BOD/day/1000 sq ft
3.	6.0 lbs BOD/day/1000 sq ft
4.	12.0 lbs BOD/day/1000 sq ft
5.	24.0 lbs BOD/day/1000 sq ft
END OF OBJECTIVE TEST

-------
MONTHLY RECORD
CLEANWATER, USA
WATER POLLUTION CONfROL PLANT
19.
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-------
CHAPTER 13
EFFLUENT DISPOSAL
by
Bill B. Dendy
revised by
Daniel J. Hinrichs

-------
184 Treatment Plants
TABLE OF CONTENTS
Chapter 13. Effluent Disposal
Page
OBJECTIVES	185
GLOSSARY 	186
13.0	Importance of Effluent Disposal 	187
13.1	Effluent Disposal by Dilution 	187
13.10	Treatment Requirements 	187
13.11	Sampling and Analysis Equipment Variations 	190
13.12	Control Considerations	190
13.2	Operating Procedures	191
13.20	Start-up 	191
13.21	Normal Operation	191
13.22	Shutdown	191
13.23	Operational Strategy	191
13.24	Emergency Operating Procedures	191
13.25	Troubleshooting 	191
13.3	Receiving Water Monitoring			 191
13.30	Types of Monitoring Programs 	191
13.31	Temperature	193
13.32	Dissolved Oxygen 	196
13.33	Review of Sampling Results 	199
13.34	Interpretation of Test Results and Follow-up Corrections 	199
13.4	Sampling and Analysis	199
13.40	Collection	199
13.41	Frequency of Sampling	200
13.42	Size of Sample	200
13.43	Labeling of Samples 	200
13.44	What to Measure	200
13.5	Safety	200
13.6	Maintenance	200
13.7	Review of Plans and Specifications	201
13.8	Other Types of Receiving Waters		201
13.9	Additional Reading	201

-------
Effluent Disposal 185
OBJECTIVES
Chapter 13. EFFLUENT DISPOSAL
Following the completion of Chapter 13, you should be able
to do the following:
1.	Properly dispose of plant effluents in receiving waters;
2.	Develop an operation strategy for effluent disposal;
3.	Troubleshoot an effluent disposal system;
4.	Develop a receiving water monitoring program;
5.	Select the proper locations to collect samples;
6.	Determine when and how often samples should be col-
lected;
7.	Collect representative samples;
8.	Conduct your monitoring program in a safe fashion; and
9.	Review plans and specifications for an effluent disposal
system.

-------
186 Treatment Plants
GLOSSARY
Chapter 13. Effluent Disposal
COMPOSITE (PROPORTIONAL) SAMPLE	COMPOSITE (PROPORTIONAL) SAMPLE
(com-POZ-it)
A composite sample is a collection of individual samples obtained at regular intervals, usually every one or two hours during a
24-hour time span. Each individual sample is combined with the others in proportion to the flow when the sample was collected. The
resulting mixture (composite sample) forms a representative sample and is analyzed to determine the average conditions during the
sampling period.
ESTUARIES (ES-chew-wear-eez)	ESTUARIES
Bodies of water which are located at the lower end of a river and are subject to tidal fluctuations.
FIXED	FIXED
A sample is "fixed" in the field by adding chemicals that prevent the water quality indicators of interest in the sample from changing
before final measurements are performed in the lab.
GRAB SAMPLE	GRAB SAMPLE
A single sample of wastewater taken at neither a set time nor flow.
NPDES PERMIT	NPDES PERMIT
National Pollutant Discharge Elimination System permit is the regulatory agency document designed to control all discharges of
pollutants from point sources into U.S. waterways. NPDES permits regulate discharges into navigable waters from all point sources
of pollution, including industries, municipal treatment plants, large agricultural feed lots and return irrigation flows.
REPRESENTATIVE SAMPLE	REPRESENTATIVE SAMPLE
A portion of material or water identical in content to that in the larger body of material or water being sampled.
RESPIRATION	RESPIRATION'
The process in which an organism uses oxygen for its life processes and gives off carbon dioxide.

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Effluent Disposal 187
CHAPTER 13. EFFLUENT DISPOSAL
13.0 IMPORTANCE OF EFFLUENT DISPOSAL
Proper disposal of plant effluent is the final process for the
operator. The job you have done operating and maintaining all
of the processes contributes to the quality of the final effluent.
There are several means of effluent disposal. This chapter
emphasizes the most common method, disposal by dilution in
receiving waters (Fig. 13.1). Disposal on land and direct or
indirect reuse are covered in Chapter 25, "Wastewater Recla-
mation." Included there you will find a discussion of disposal
on land by the use of irrigation, groundwater recharge basins,
and underground disposal. However, the most common dis-
posal rrfethod is disposal by dilution or direct discharge to sur-
face waters. Surface waters include rivers, streams, lakes,
ESTUARIES,1 and oceans. Disposal requirements vary de-
pending on the probable use of the receiving waters. Typical
water quality indicators for various water uses are listed in
Table 13.1.
In addition to providing successful operation, effluent control
is extremely important in legal matters. For example, there
may be several effluents being discharged to the receiving
water. If a problem develops, then all discharges would be
investigated by the regulatory agency. If proper sampling and
analysis techniques were carefully followed and results re-
corded, then the regulatory agency can look for problem
causes elsewhere if your discharge is not causing the problem.
Another type of legal issue may be a change in the discharge
standards. If accurate sampling and analysis techniques show
that a certain constituent level is not causing a problem in the
receiving stream, then the required constituent level can be
changed in the discharge permit. For example, a chlorine re-
sidual of 1.0 mg/l may be required in the effluent. If sampling
and analysis showed this level was not necessary or was ex-
cessive in controlling coliform bacteria, then a formal request
can be made for a change in the standard. The result could
mean a substantial savings in chlorine costs.
Due to water shortages in many areas and extremely strin-
gent requirements for direct discharge in some locations, rec-
lamation and reuse are becoming popular. Land disposal sys-
tems are more often land reclamation systems. Usually sec-
ondary treatment systems remove suspended solids and BOD,
but not nutrients such as nitrogen and phosphorus. The nitro-
gen and phosphorus are extremely valuable to farmers who
irrigate with treated effluent. In some instances they do not
need to purchase and apply chemical fertilizers. In ALL in-
stances they can reduce their fertilizer costs. Land disposal
systems are beneficial to the municipality in that the soil layer
and plant material serve as a "living filter" to remove unwanted
materials from the effluent. Groundwater recharge basins or
infiltration-percolation basins are extremely simple to operate
and maintain. An underground disposal system usually con-
sists of a deep well injection system. These systems may be
used to displace oil or gas that is being pumped out of the
ground or to provide a barrier between underground salt water
and fresh groundwater.
Direct and indirect reuse of treated effluent is limited only by
the costs to treat the effluent to the necessary requirements for
a particular use. Normally, reuse systems supply washdown
water or cooling water.
QUESTIONS
Write your answers in a notebook and then compare your
answers with those on page 202.
13.0A What is the most common method of effluent dis-
posal?
13.0B What are common methods of wastewater reclama-
tion?
13.1 EFFLUENT DISPOSAL BY DILUTION
13.10 Treatment Requirements
Prior to disposal by dilution, the wastewater is treated to
protect the health of the people who may come in contact with
it, to prevent nuisances due to odors or unsightliness, and to
prevent the wastewater from interfering with the many uses of
the surface waters. Governmental regulatory agencies set dis-
charge requirements in order to insure that surface waters
receiving effluent are protected. The requirements will vary
depending on local conditions but may consist of both
TREATMENT EFFICIENCY2 standards and effluent quality
standards. For example, a plant may be required to remove 85
percent of the influent suspended solids and to maintain an
effluent suspended solids concentration of less than 30 mg/Z..
The operator measures both the influent and effluent concen-
trations and from these determines the percent reduction.
These measurements are called "in-plant measurements."
Those in-plant measurements which show the results of an
individual unit process or the entire plant are "performance
1 Estuaries (ES-chew-wear-eez). Bodies of water which are located at the lower end of a river and are subject to tidal fluctuations.
* Treatment Efficiency, % = (Concentration >"¦ mQ"- ~ Concentration Out, mg/L) 100%
Concentration In, mgIL

-------
188 Treatment Plants
RECEIVING STREAM
PLANT
EFFLUENT
DISCHARGE
Fig, 13.1 Effluent disposal by dilution

-------
Effluent Disposal 189
TABLE 13.1 WATER QUALITY CRITERIA®
(All units in mgIL unless otherwise noted)
WATER QUALITY
INDICATOR
WATER USE
NON-CONTACT
RECREATION
CONTACT
RECREATION
FISH
PROPAGATION
DRINKING
WATER SUPPLY
IRRIGATION
LIVESTOCK
AND WILDLIFE
Aquatic
Growth
Virtually
Free
Virtually
Free
	
	
	
Avoid blue-
green algae
Coliform
Bacteria
200 MPN/
100 mL
100 MPN/
100 mL
	
20,000 MPN/
100 mL
1000 MPN/
100 mL
5000/100 mL
COD
60
30
—
—
—
—
Floating Debris
and Scum
Virtually
Free
Virtually
Free
	
	
	
—
Odor,
Units
Virtually
Free
Virtually
Free
	
Virtually
Free
	
	
Oxygen,
Dissolved
Aerobic
Aerobic
5.0
	
	
Aerobic
pH, Units
6.5-8.3
6.5-8.3
6.5-9.0
—
6.0-9.0
7.0-9.0
Settleable
Solids
Virtually
Free
Virtually
Free
	
	
	
—
Nitrogen, total
—
10
—
—
—
—
Nitrite as N
—
—
—
1.0
—
10
Nitrite and
Nitrate as N
	
	
	
	
	
100
Ammonia as N
	
	
0.02
(un-ionized)
0.05
	
	
Nitrate as N
—
—
—
10.0
—
—
Phosphate
—
0.2
—
—
—
—
Suspended
Solids
—
5
25
—
—
—
NOTE: There are other elements which interfere with use of effluent for these purposes. However, these other elements can not be controlled by
conventional wastewater treatment processes.
» WATER REUSE - VOLUME 2, EVALUATION OF TREATMENT TECHNOLOGY (OWRT/RU-79/2) by Culp, Wesner, Culp; report for U.S.
Department of Interior, Office of Water Research and Technology, Washington, D.C., 1979.

-------
190 Treatment Plants
evaluation" tests. In-plant measurements which assist the
operator in deciding how to operate a unit are called "process
control" tests. For example, the dissolved oxygen test in an
aeration basin is a process control test. The results indicate to
the operator whether the aeration system is providing sufficient
oxygen to the organisms treating the wastes.
A second type of measurement consists of "receiving water
measurements." These tests are used to determine the effect
of the waste discharge on the receiving waters and on the
beneficial uses (water supply, recreation, fishery) of the receiv-
ing waters after the effluent has mixed with the receiving wa-
ters. A plant could be operating according to its design and be
removing 90 percent of the suspended solids, yet still be caus-
ing a bad impact on the water quality in the water which re-
ceives the effluent. This could happen because the plant was
not designed to meet the more demanding effluent standards
or there has been a change in the receiving water, such as a
reduction in flow or new industrial discharges since the plant
was built.
Receiving water measurements are as important as the in-
plant measurements because the real purpose of the plant is to
protect the receiving waters. However, plants should always
be operated as efficiently as possible, therefore in-plant meas-
urements must not be slighted. Also, the plant effluent must be
tested or measured so that it can be related to effects in the
receiving waters.
The usual approach in measuring the impact of a discharge
on receiving waters is to take a measurement in an area which
is not affected (upstream) and in an area which is affected
(downstream) and compare the two results. This comparison
shows how much of an impact the discharge has on the receiv-
ing waters. Analysis of the differences shows whether the dis-
charge is causing a violation of the water quality objectives or
standards which have been set by the regulatory agency.
Successful operation of a disposal by dilution system de-
pends on conscientious operators using proper techniques for
sampling and analysis.
13.11 Sampling and Analysis Equipment Variations
Equipment requirements include sampling and metering
equipment. The sampling equipment can vary from sample
bottles for manual GRAB SAMPLES3 to complex devices con-
sisting of timers and flow proportioning equipment for obtaining
composite samples. As the name grab sample suggests, these
samples are taken at no particular place nor time. A COMPOS-
ITE SAMPLE* is one which consists of a series of samples
taken over a given time period at a particular location. For
example, a 24-hour composite sample may consist of 24 indi-
vidual samples taken each hour or the sample may consist of a
continuous composite obtained by continually pumping a sam-
ple. Some composite samplers are more complex than others.
Each of the samples in the composite may be equal in size or
proportional to the flow at the time of the sampling.
Sampling equipment is usually required to collect samples
for measuring biochemical oxygen demand (BOD) and sus-
pended solids (SS). Dissolved oxygen (DO), temperature and
pH may be monitored or determined from measurements in the
actual flow stream (wastewater being treated). Total coliform
and fecal coliform determinations are performed only on care-
fully collected grab samples. Each area of surface water will
have certain special requirements for additional data or addi-
tional tests that must be conducted. For example, in areas with
slowly moving streams or rivers, fish may be endangered by
ammonia (NH3) resulting from the ammonium ion (NH4+) in the
effluent.
Flow-metering equipment is usually located at the plant
headworks. In most situations, the actual effluent flow is not
critical. However, some discharge requirements include a limit
on the total pounds per day of a constituent (suspended solids)
in addition to the concentration. The total pounds/day is equal
to the flow (MGD) times concentration (mg/L) times the con-
stant 8.34.5 Metering devices include weirs, Parshall flumes,
Venturi meters, propeller meters and magnetic meters.
13.12 Control Considerations
Physical control of effluent disposal by dilution is ususally
limited to discharging all flow that enters the plant. However,
some systems may have emergency effluent storage lagoons
available. Physical control is generally not needed unless
some special problem has arisen, such as a toxic waste spill
into the collection system. In this situation, there are two solu-
tions. The affected flow may be stored for future treatment or
treated chemically prior to entering the plant. Usually storage is
not possible, however, and a neutralizing chemical may be
added prior to discharge. If the treatment processes fail, or if
water quality levels in receiving waters become critical, the
emergency effluent storage facilities can be used.
Operators can detect adverse impacts on receiving waters
caused by the treatment plant effluent by observing odors,
visible floating substances, grease, or abnormal colors. Odors
may indicate failure in a treatment process in the plant or the
discharge of an industrial waste into the collection system or to
the receiving water. Visible floating substances may be indica-
tive of a malfunctioning skimmer or a final sedimentation tank.
QUESTIONS
Write your answers in a notebook and then compare your
answers with those on page 202.
13.1 A What water quality indicators are usually determined
by in-stream measurements?
13.1B What water quality indicators are usually determined
by samples collected in the field and analyzed in the
lab?
3 Grab Sample. A single sample of wastewater taken at neither a set time nor flow.
*	Composite (Proportional) Sample (com-POZ-it). A composite sample is a collection of individual samples obtained at regular intervals,
usually every one or two hours during a 24-hour time span. Each individual sample is combined with the others in proportion to the flow when
the sample was collected. The resulting mixture (composite sample) forms a representative sample and is analyzed to determine the average
conditions during the sampling period.
*	Loading on = (Flow, MGD) (Concentration, mg/L) (8.34 Ibslgal)
receiving
waters, Ibslday
mg
Remember that mgIL =	
M mg

-------
Effluent Disposal 191
13.2 OPERATING PROCEDURES
Effluent disposal by dilution is similar to other treatment pro-
cesses and fairly straightforward. Before starting your plant,
operating procedures covering initial start-up, routine opera-
tion, shutdown and abnormal conditions should be developed.
These procedures can help avoid forgetting a critical item that
could result in the violation of your NPDES PERMIT6 or cause
a fish kill in the receiving waters. The following procedures
apply to most plants, and you should use them as a guide for
developing procedures to be used at your own plant.
13.20	Start-up
1.	Inspect discharge line where possible.
2.	Open all valves.
3.	Start pumps (unless gravity system).
4.	Observe flow entering discharge system for visible pollu-
tants.
5.	Look at water surface over diffuser (if your plant has a
diffuser) or outfall pipe for unusual turbulence caused by
break in line (or conversely — lack of turbulence and possi-
ble clogged line). Also look for foam, oil, grease or discol-
oration of the water which would be undesirable from an
aesthetic viewpoint.
13.21	Normal Operation
1.	Conduct monitoring program. See Section 13.3, "Receiving
Water Monitoring," for detailed procedures.
2.	Inspect plant operation if sudden change in visual appear-
ance of effluent is observed.
13.22	Shutdown
1.	Stop pumps (unless gravity feed).
2.	Close valve preceding discharge line.
3.	Flush line and diffuser with fresh water, if possible.
13.23	Operational Strategy
Operational strategy consists of doing everything possible to
minimize the discharge of pollutants to the receiving waters.
This may involve the use of emergency holding tanks or reser-
voirs during times when treatment processes have failed or
toxic wastes reach the plant. After the failure has been cor-
rected, the stored effluent must be properly disposed of. Dis-
posal can be accomplished by any of three methods. (1) The
stored water may be slowly added to the treated effluent (dis-
posal by dilution in treated effluent). Another procedure (2)
consists of returning the stored water to the plant for treatment.
This would be done during periods of low flow into the plant so
the treatment processes would not become overloaded. (3) If
the waste is extremely toxic, treat it chemically or allow it to
become concentrated by evaporation in the storage pond.
After concentration, dispose of toxic waste in an approved san-
itary landfill.
The decision of which method to use depends on the condi-
tion of the stored water. If the wastes can be diluted with
treated effluent and the discharge requirements met, then this
is the preferred method. Otherwise, treatment is required. This
treatment should be done during times when the plant inflow is
low and returned at a low flow rate. A high rate of flow returned
during the day when flows coming to the plant are high could
cause the treatment processes to be upset.
13.24 Emergency Operating Procedures
The impact on the disposal system due to loss of power is
critical only with pumped discharge systems. These systems
should have standby generators which can be started to pro-
vide power to run pump motors.
Loss of upstream treatment units will result in poorer effluent
quality. If available, emergency storage reservoirs should be
used and discharge to the receiving stream stopped until up-
stream units are working properly again.
13.25 Troubleshooting
If your plant is not meeting National Pollutant Discharge
Elimination System Permit requirements, try to identify the
cause of the problem and to select the proper corrective action.
Solutions to the problems listed in this section (Tables 13.2,
13.3 and 13.4) have been covered in more detail in previous
chapters.
QUESTIONS
Write your answers in a notebook and then compare your
answers with those on page 202.
13.2A Operating procedures should be developed for what
conditions in an effluent disposal program?
13.2B What is the main consideration for an operational
strategy?
13.3 RECEIVING WATER MONITORING
13.30 Types of Monitoring Programs
There are two types of monitoring programs. The first is the
STREAM OR WATER QUALITY SURVEY. To plan a water
quality survey, you must understand the reasons for, or the
objectives of, the survey. A typical objective could be to detect
any adverse impact of the plant effluent on the receiving wa-
ters. An EFFLUENT SAMPLING program is the other type of
monitoring program. The overall objectives of each survey
greatly influence the location of sampling stations, types of
samples, frequency and time of day of collecting samples, and
any other critical factors. When developing sampling pro-
grams, survey planners also must realize that water quality
characteristics vary from one body of water to another, from
place to place in a given body of water, and from time to time at
a fixed location in a given body of water.
A sampling program must be prepared in a manner that will
produce accurate and useful results. The collection, handling,
and testing of each sample should be scheduled and con-
ducted in such a manner as to assure that the results will be
descriptive of the sources of the individual samples at the time
and place of collection. Select locations for sampling stations
and collect samples during times of the day and/or night that
will provide the data needed to meet the objectives of your
survey. Collect enough data over a period of time to
adequately describe the condition or quality of the water at
each sampling station.
4 NPDES Permit. National Pollutant Discharge Elimination System permit is the regulatory agency document designed to control all dis-
charges of pollutants from point sources Into U.S. waterways. NPDES permits regulate discharges into navigable waters from all point
sources of pollution, Including industries, municipal treatment plants, large agricultural feed lots and return irrigation flows.

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192 Treatment Plants
TABLE 13.2 TROUBLESHOOTING POND EFFLUENTS
Indicators/
Observations
PONDS
1. Floatables in
effluent
2.
Excessive
algae in
effluent
3. Excessive
BOD in effluent
Probable
Cause
1 a. Outlet baffle not at
proper location
1 b. Excessive floatables
and scum on surface
1c. Excessive velocity
or insufficient
detention time
2.	Temperature or
weather conditions
may favor a particular
species of algae
3.	Detention time too
short, hydraulic or
organic overload,
poor inlet and/or
outlet arrangements
and possible toxic
discharges
1a.
1b.
Check or
Monitor
Visually inspect
outlet baffle.
Visually inspect
pond surface.
1c. Visually inspect
pond effluent.
2. Visually observe
effluent or run
suspended solids
test.
3a. Influent flows.
3b. Calculate organic
loading.
3c. Observe flow thru
inlet and outlet
3d. Dead algae in
effluent.
Solutions
REVIEW CHAPTER 9
1 a. Adjust outlet baffle.
1b. Remove floatables from pond sufrace
using hand rakes or skimmers. Scum can
be broken up using jets of water or a
motor boat. Broken scum often sinks.
1c. Reduce flow from upstream units.
2. Operate ponds in series.
Draw off effluent from below
pond surface by use of
a good baffle arrangement.
Inspect collection system
3a.
3b.
3c.
Use pumps to recirculate
pond contents.
Rearrange inlets and outlets
or install additional ones.
3d. Prevent toxic discharges.
TABLE 13.3 TROUBLESHOOTING BIOLOGICAL PROCESS EFFLUENTS
Indicators/
Observations
SECONDARY
CLARIFIERS FOR
TRICKLING FILTERS,
ROTATING BIOLOGICAL
CONTRACTORS
OR
ACTIVATED SLUDGE
1. Floatables
In effluent
Probable
Cause
Check or
Monitor
2. Excessive
algae in
effluent
3. High BOD
1 a. Clarifiers hydrauli-
cally overloaded
1b. Skimmers not
operating properly
2a. Clarifiers hydrauli-
cally overloaded
2b. Biological treat-
ment process organi-
cally overloaded
3. See 2b above
1 a. Visually observe
effluent or cal-
culate hydraulic
loadings.
1b. Observe skimmer
movement.
2a. See 1 a above.
2b. Calculate BOD or
organic loading.
3. See 2b above.
Solutions
REVIEW CHAPTER 6
REVIEW CHAPTER 7
REVIEW CHAPTERS 8 8,11
1 a. Install hardware cloth or
similar screening device
in effluent channels.
Review Chapter 5.
1 b. Lower skimmer arm, replace
neoprene or adjust arm.
2a. See 1 a above and review
operation of bilogical
treatment process.
2b. Review operation of
biological treatment
process.
3. See 2b above.

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Effluent Disposal 193
TABLE 13.4 TROUBLESHOOTING DISINFECTED EFFLUENTS
Indicators/
Observations
DISINFECTION
1.	Unable to
maintain
chlorine
residual
2.	Unable to
meet coliform
requirements
1a.
1b.
2a.
2b.
Probable
Cause
Chlorinator not
working properly
Increase in
chlorine demand
Chlorine residual
too low
Chlorine contact
time too short
2c. Solids in
effluent
2d. Sludge in chlorine
contact basin
2e. Diffusernot
properly dis-
charging chlorine
2f. Mixing inadequate
Check or
Monitor
1a. Inspect chlorinator.
1b.
Run chlorine
demand tests.
2a. See 1 above.
2b. Measure time for
dye to pass thru
contact basin.
2c. Observe solids or
run suspended
solids test.
2d. Look for sludge
deposits in
contact basin
2e. Lower tank water
level and inspect.
Solutions
REVIEW CHAPTER 10
1 a. Repair chlorinator.
1b.
Increase chlorine dose and/or identify
correct cause of increase in demand.
2a. See 1 above.
2b. Improve baffling arrangement.
2c. Install hardware cloth or similar screening
device in effluent channels. Review
operation of biological treatment process.
2d. Drain and clean contact basin.
2e. Clean diffuser.
2f. Add dye to diffuser. 2f. Add mechanical mixer or move diffuser
To illustrate these important items, consider a simplified
example of a waste discharge into a flowing river. Assume the
river flows at 500 cubic feet per second (cfs) (14 cu m/sec) and
the treatment plant discharges at 10 cfs (6.46 MGD or 0.3 cu
m/sec). Assume that it is desirable to find out what is the im-
pact on the river. To determine the impact, the following ques-
tions must be answered:
1.	What are the characteristics of the river upstream from the
discharge?
2.	What are the characteristics downstream?
3.	If upstream and downstream river characteristics are differ-
ent, does the discharge cause the difference?
4.	Are the downstream river characteristics in violation of es-
tablished standards or objectives?
5.	If the river downstream is in violation of standards or objec-
tives, did the discharge cause it?
Start with Question 1. Assume that you wish to measure:
a.	Temperature
b.	Dissolved Oxygen
13.31 Temperature
You must develop a temperature measurement program
which will accurately describe the river temperature upstream
from the discharge. How can this be done so that the changes
from hour to hour during the day and from month to month
during the year are known? Also, how can the temperature be
measured so that the average for the river cross section can be
found, as well as the variations from the average in the cross
section. (See Fig. 13.2.)
In some rivers which are deep and slow-moving, the tem-
perature may be several degrees cooler on the bottom than on
the top. Thus if the temperature measurement up-river from
the discharge was taken near the bottom and the one down-
river near the top, it might appear that the discharge had
caused the stream to warm up when it actually had little im-
pact.
The first thing to do is locate the river cross section (line
across the stream) to be sampled. This may be located at a
bridge or near a boat dock or some other accessible place.
Then measure the temperature at several points across the
stream and at several depths at each point (see Fig. 13.2).
Measurements also should be taken near shorelines, in back-

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194 Treatment Plants
WATER SURFACE
SHORELINE
* SAMPLING POINTS
RIVER BOTTOM
NOTE: Sampling points should be located near the shoreline
and approximately one foot (0.3 m) below the water
surface and one foot (0.3 m) above the bottom. The
number of sampling points between the water surface
and the bottom will depend on the depth of the water,
and the number of vertical sampling sections will de-
pend on the width of the stream. Total number of sam-
pling points also will depend on budget, time, water
quality indicators being sampled and desired accu-
racy.
Fig. 13.2 River cross-section showing typical sampling
points

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Effluent Disposal 195
water areas, and near the stream bottom. These are locations
where problems first develop. If the temperatures are all about
the same (within about 1°C or 2°F),7 you can assume the
stream is well mixed with a uniform temperature.
The next thing to consider is the time of day. Most streams
will be cooler at night than during the day. Usually mid-channel
temperature measurements vary less than those in shallow
stretches. The minimum (lowest) temperature usually occurs
about dawn and the highest in the late afternoon. The best way
to measure these variations is to use a 24-hour recorder. If no
recorder is available, take a measurement each hour for 24
hours (a little night work never hurt anybody!) to get an aver-
age temperature for the day: add up all the numbers and divide
by 24. Then see WHAT TIME OF DAY the average value and
the maximum value usually occur. (This may vary with the
season.) Usually it is accurate enough for most streams to
measure the temperature at those times and use the values for
an average daily and maximum daily. For example, assume
the following measurements were recorded:
185 Time
Temperature °C
12 NOON
12.4
1 PM
12.8
2 PM
13.2
3 PM
13.6
4 PM
14.0
5 PM
13.8
6 PM
13.6
7 PM
13.3
8 PM
13.0
9 PM
12.7
10 PM
12.4
11 PM
12.0
12 MIDNIGHT
11.6
1 AM
11.2
2 AM
10.8
3 AM
10.5
4 AM
10.3
5 AM
10.1
6 AM
10.0
7 AM
10.2
8 AM
10.4
9 AM
10.8
10 AM
11.2
11 AM
11.8
Average Temperature, °C =
TOTAL = 285.7°C
Sum of Measurements, "C
Number of Measurements
285.7°C
24
= 11.9°C
The average temperature of 11,9°C occurs at about 11 AM
and again about 11 PM. If every day is like this, a measure-
ment taken at 11 AM each day will give a fairly accurate record
of the daily average temperature. Periodic rechecks of the
hourly variation should be made. The same goes for the
maximum value, which occurs at 4 PM.
The next thing to consider is the seasonal variation in tem-
perature. Streams normally warm up in summer and cool off in
winter. Obviously, if a measurement is taken daily (as ex-
plained above) this record will show all variations throughout
the year. But, usually the daily average temperature does not
change very much from day to day.
Assume that the daily values for each month have been
used to calculate monthly averages and that the following
numbers have been obtained.
Month
January
February
March
April
May
June
July
August
September
October
November
December
Monthly Average
Temperature, °C
7.0
6.0
8.0
10.0
12.0
14.0
16.0
19.0
18.0
14.0
10.0
8.0
TOTAL
Yearly Average, °C
142.0°C
Minimum Monthly
Average, °C
Maximum Monthly
Average, °C
_ Sum of Measurements, °C
Number of Measurements
= 142.0°C
12
= 11.8°C
= 6.0°C
= 19.0°C
The month-to-month changes in temperature are not very
predictable because some years are colder than others, or
summer lasts longer, or something else unusual can happen.
The minimum and maximum monthly averages indicate the
extent of the monthly changes for the observed year.
This discussion of temperature measurement does not
mean that temperature is the most important characteristic to
measure, although it is important from the standpoint of pro-
tecting fish. What is important is for you to be careful when
selecting a sample for measuring ANY characteristic of waste-
water or the receiving waters. Be sure to plan ahead so that
each sample will indicate or represent the actual conditions of
the river. If this is accomplished, you have obtained a REPRE-
SENTATIVE SAMPLE.8 Going out and blindly taking meas-
urements (sometimes known as "flailing the water") can yield a
lot of numbers which don't mean very much, but only the per-
son who takes the measurement knows that. Others who use
the numbers may assume they are meaningful and act accord-
ingly. ALWAYS PLAN AHEAD TO GET MAXIMUM BENEFIT
FROM YOUR RECEIVING WATER SAMPUNG PROGRAM.
Now go back to Question 2. What are the characteristics (in
this case, temperature) down-river from the discharge? The
same procedure for sample selection downstream should be
used as previously explained. There is an additional considera-
tion, however. The cross section selected for a sampling sta-
tion should be far enough downstream for the waste discharge
to have become well mixed.
If the stream is very sluggish and deep, the discharge may
not mix thoroughly for a mile or more; so it will be necessary to
sample in such a way that the unmixed condition can be de-
7 °C means "degrees centigrade or degrees Celsius," both of which refer to a particular temperature scale; °F means "degrees Fahrenheit," a
different temperature scale.
* Representative Sample. A portion of material or water identical In content to that in the larger body of material or water being sampled.

-------
196 Treatment Plants
scribed properly (Fig. 13.3). The higher the stream velocity,
shallower the water, and the sharper the bends in the stream,
the greater the turbulence and thus the quicker the discharge
becomes mixed with the receiving waters.
Before going out in the field to measure water quality, obtain
a range of expected values for guidance in sampling and inter-
preting results. Try various sampling locations to find high and
low values for different times of the day and season.
Look now at the problem of measuring the temperature (or
other characteristic) of the treatment plant effluent. Wastewa-
ter flow from a municipal discharge normally has a variable
flow rate and variable characteristics. Fortunately, this varia-
tion follows similar patterns from day to day, week to week,
year to year, so a logical sampling program can be set up to
keep track of the characteristics of the plant effluent.

REMEMBER:
THE EFFLUENT MEASUREMENT PROGRAM MUST BE
DESIGNED TO TELL THE OPERATOR HOW MUCH VOLUME
OF FLOW AND WHAT QUALITY OF CONSTITUENTS ARE
ENTERING THE RECEIVING WATERS HOURLY, DAILY,
WEEKLY, MONTHLY, AND YEARLY.
Try to have a convenient access location where the effluent
can be sampled easily. A remote sampling location or one
which is difficult to reach will discourage regular sampling.
Wherever the sampling station is located, it must provide
meaningful samples.
13.32 Dissolved Oxygen
Another measurable characteristic of the stream is dissolved
oxygen. The principles for collecting samples for measuring
dissolved oxygen are the same as for measuring temperature.
In fact, the amount of dissolved oxygen that can be in water
DEPENDS on temperature, among other things.
Cold water will hold more dissolved oxygen than hot water.
This does not mean that cold water always will contain more
oxygen. Cold waters tend to slip under warmer waters because
they have a greater density. In the lower layers of a body of
water they are farther from the sources of oxygen from surface
aeration and algal activity. Bottom waters may be close to
deposits of organic materials containing organisms that use
oxygen during RESPIRATION.9 The net result could be lower
oxygen concentrations in colder waters if they remain near the
bottom too long.
In measuring the dissolved oxygen downstream from a
treatment plant discharge, it is important to remember that a
decrease in dissolved oxygen may not be noticeable IM-
MEDIATELY downstream, even if the effluent is well mixed
with the stream. Many hours of flow time may be required for
the oxygen to be reduced due to organic material in the dis-
charge. So it is necessary to make an "oxygen profile" of the
stream to get a good measure of the effect of the effluent.
Making a profile means merely measuring the dissolved
oxygen at several different cross sections downstream from
the discharge to find out where the lowest dissolved oxygen
level occurs. For this example, assume the same waste dis-
charge and river used in the previous sample.
Number the cross sections to be samples as follows:
Cross Section No.
1
2
3
4
5
6
7
Location
1 mile above discharge
1 mile below discharge
3 miles below discharge
5 miles below discharge
7 miles below discharge
9 miles below discharge
11 miles below discharge
Identify the location of any additional waste discharges or
points of inflow from tributary streams. Selection of the number
and location of sampling cross sections depends on stream
characteristics, accessibility, and information desired. Nor-
mally locations are selected to show critical conditions and
changes in the receiving waters.
At each cross section, be sure representative samples are
being selected. Always remember that a gallon of sample is
supposed to be identical to the millions of gallons of water that
flow past the sampling point.
Now, assume that you have checked and found that only
one properly located sample was required to represent each
cross section and that the following measurements were ob-
tained:
Cross Section No. Temperature, °C Dissolved Oxygen, mg/L
13.5
13.5
13.5
13.5
13.5
13.5
13.5
10.5
10.0
9.0
7.5
6.0
7.1
8.9
(Note that the temperature is constant for all cross sections.
This is to simplify the example. If the temperature increased
downstream from the discharge, some of the drop in dissolved
oxygen would be due to the temperature increase and some
would be due to the organic material. You also should be sure
to notice any effects due to tributaries or other waste dis-
charges.)
Fig. 13.4 shows a plot or graph of the measurements listed
above. This is a good way to show the dissolved oxygen pro-
file. Profiles for different days or months can be plotted on the
same sheet in different colors to show how the profile changes
from season to season or from year to year. The location of the
9 Respiration. The process in which an organism uses oxygen for its life processes and gives off carbon dioxide.

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Effluent Disposal 197
SECTION A
SAMPLING POINTS WILL
HELP TO SHOW MIXED AND
UNMIXED AREAS
SECTION B
RIVER FLOW
V.SJ'.V.V
IIT
SECTION A
ol:®:?:

iSECT I ON B
A
i

vXvlv/lwX
.v.vXv!
mm
MS
SSii-SiSSiS:
Mm®
wmm
S&WSS8SS
XvMvXvM1

.V.V.V.V.V.
WASTE DISCHARGE
MIXING ZONE
« PATTERN
END OR SECTION VIEW
TOP VIEW
Fig. 13.3 Waste mixing in a river

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198 Treatment Plants
LOCATION OF DISCHARGE
CROSS SECTION NUMBER
Fig. 13.4 Dissolved oxygen profile

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Effluent Disposal 199
low point may move up or down the stream, depending on the
amount of flow in the stream and other factors. Therefore,
several points must be obtained for each profile to be sure the
amount and location of the low point can be determined. Addi-
tional discharges will complicate the profile.
13.33 Review of Sampling Results
To determine if sampling stations are in the proper location
and producing meaningful results, the results from the testing
program must be carefully reviewed. If the results don't appear
correct, try to determine why they appear strange. Look for
sampling errors, testing errors, and recording errors. Attempt
to verify each step in your sampling program. Remember that
you sample because something unusual can happen. Don't
reject strange results because they are unusual, but investi-
gate and attempt to identify the reasons for the results. Estab-
lish additional sampling locations when necessary and elimi-
nate or relocate stations that are not producing meaningful
results.
QUESTIONS
Write your answers in a notebook and then compare your
answers with those on page 202.
13.3A An assistant plant operator collected samples and
measured the temperature at one stream cross sec-
tion each hour for 24 hours. Following are the results
reported:

Temperature
Temperature
Time
°C
Time
°C
1 PM
13.5
1 AM
12,4
2 PM
13.4
2 AM
11.0
3 PM
14.3
3 AM
11.0
4 PM
14.7
4 AM
10.8
5 PM
14.5
5 AM
10.6
6 PM
13.8
6 AM
10.5
7 PM
14.0
7 AM
10.7
8 PM
13.7
8 AM
11.6
9 PM
13.4
9 AM
11.4
10 PM
22.7
10 AM
11.8
11 PM
12.7
11 AM
12.4
12 MIDNIGHT
12.2
12 NOON
13.0


TOTAL =
310.1°C
Average	_ Sum of Measurements, °C
Temperature, °C Number of Measurements
= 31°i°c
24
= 12.9°C
You are the supervisor. What would be your re-
sponse to these results?
13.3B Which measurement would you consider doubtful?
a.	12 MIDNIGHT
b.	4 AM
c.	10 PM
d.	6 AM
13.3C Assume that you tell the operator to collect a new set
of measurements two days later. The operator meas-
ures (not copies) all the same numbers except for the
one you questioned earlier, and the new reading for
that hour is 13.0. What are the new total and average
values?
a.	296.3 and 13.2
b.	316.9 and 12.6
c.	300.4 and 12.5
d.	306.1 and 12.7
e.	298.9 and 13.0
13.3D a. What are the new maximum and minimum val-
ues?
b.	At what times did they occur?
c.	Which sample most nearly represented the aver-
age value?
13.34 Interpretation of Test Results and Follow-up
Corrections
A sudden drop in the receiving stream dissolved oxygen
(DO) below the discharge line without a similar drop upstream
from the line indicates that the plant biochemical oxygen de-
mand (BOD) removal efficiency has decreased and should be
corrected. The sudden drop in DO might have been caused by
an increase in temperature resulting from an industrial waste
discharge. The source should be determined and corrective
action taken.
Sudden changes in effluent constituent concentrations may
be due to process failure, a sudden increase in flow quantity, or
a change in influent characteristics such as industrial waste
discharges into the system. A review of influent data will de-
termine whether the problem is in-plant or due to a change in
the influent. If the problem is in the influent, the source will take
time to trace. Until the source can be found and corrective
action taken, adjustments should be made in the plant to
minimize the detrimental effect on the receiving stream.
13.4 SAMPLING AND ANALYSIS
13.40 Collection
The proper technique to follow and precautions to observe to
be sure a good sample is obtained are adequately covered in
several publications. Complete information about proper sam-
pling techniques can be found in the publications listed in Sec-
tion 13.9, "Additional Reading." Also see Chapter 16, Section
16.3, "Sampling," in this manual. All of these books emphasize
having the proper equipment to do a good job. REMEMBER
THAT BEHIND ALL THE INSTRUCTIONS ON TECHNIQUES
IS THE BASIC IDEA THAT THE SAMPLE MUST BE COL-
LECTED AND PRESERVED IN SUCH A MANNER THAT IT
DOES NOT CHANGE SIGNIFICANTLY FROM THE TIME IT IS
FIRST OBTAINED IN THE FIELD UNTIL THE FINAL
ANALYSIS IS COMPLETED.
For example, if a gallon of water is selected from a stream
for a dissolved oxygen measurement, be sure that the amount
of dissolved oxygen in the sample does not change before it is
measured. The same goes for any other characteristic.

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200 Treatment Plants
Some characteristics change so rapidly that they should be
measured immediately. This is true of temperature, pH, and
dissolved oxygen. Some of the dissolved gases can be
F/XED10 tor a while to allow transporting the sample to the
laboratory for measurement. Procedures for "fixing" can be
found in Chapter 16, Section 16.36, "Preservation of Sam-
ples," STANDARD METHODS and other publications on
analysis. Usually it is not a good idea to try to fix a sample
containing a significant amount of organic matter, such as a
plant effluent, because it tends to change anyway. Take a field
kit to the sampling location and test at the site. Be sure the field
kit equipment is capable of producing the desired accuracy.
13.41	Frequency of Sampling
Regular sampling intervals should be developed in coopera-
tion with the regulatory agency having authority over the plant
and the receiving waters. When the treatment plant effluent is
not meeting discharge requirements or the receiving waters
are not meeting established water quality standards, the fre-
quency of sampling may be increased.
13.42	Size of Sample
When samples are tested in the field, the size of sample
should be sufficient to perform the desired tests. If samples are
preserved and transported to a lab for analysis, the size of
sample should be at least twice the amount needed to perform
the desired tests to allow for back-up or repeat tests.
13.43	Labeling of Samples
A record must be made of every sample collected. Every
sample bottle must be identified and should have attached to it
a label or tag indicating the exact location where the sample
was collected, date, hour, air and water temperature, and
name of collector. Other pertinent data such as water level or
river flow and weather conditions should be recorded. Precipi-
tation, cloud conditions and prevailing winds during the previ-
ous few days should be noted when collecting samples. The
weather during the three or four days before sampling may be
entirely different from the weather on the day of sampling and
may significantly affect the character of the sample. Sampling
points should be identified on maps, including a detailed de-
scription, and identified in the field by easily located markers or
landmarks.
13.44	What to Measure
There are hundreds, possibly thousands, of characteristics
which could be measured in receiving waters and plant
effluents. Many of them are not important to the operation of a
treatment plant; however, it is possible to list a minimum
number of characteristics which should enable the operator to
measure the effect of the plant's effluent and find out if it meets
water quality objectives. Measurements required for plant
effluents are specified in NPDES permits and vary with loca-
tion and use of receiving waters.
Table 13.5 contains a list of water quality characteristics
which should be observed or measured in the receiving waters
and in the plant effluent.
Many of these effluent tests are for the record rather than for
plant control purposes. The operator can do nothing in adjust-
ment of treatment plant processes to affect the characteristics.
However, the operator will often be asked to measure them
because they are listed in the plant's NPDES discharge re-
quirements or receiving waters standards. Some of them, such
as toxicity, can be controlled by ordinances which prevent toxic
substances from being put in the wastewater collection sys-
tem. Others, such as total dissolved solids, may require the city
to find a new water supply.
TABLE 13.5 EFFLUENT AND RECEIVING WATERS
CHARACTERISTICS
1.
Effluent
Visual Appearance (color,
floating materials)
Receiving Waters
Visual Appearance (color,
floating materials)
2.
Coliform Group Bacteria
and Chlorine Residual
Coliform Group Bacteria
3.
Biochemical Oxygen Demand
Dissolved Oxygen
4.
Suspended Solids and
Settleable Solids
Suspended Solids and
Clarity
5.
Temperature
Temperature
6.
pH
PH
7.
Odor
Odor
8.
Grease
Grease
The list above is basic. Some additional characteristics w
may be important in various situations are:
1.
Effluent
Total Dissolved Solids
Receiving Waters
Total Dissolved Solids
2.
Chlorine
Chlorine
3.
Hardness
Hardness
4.
Toxicity
Health of Aquatic
Animals
5.
Biostimulants (such as
nitrogen, phosphorus)
Algae and other Aquatic
Plants
6.
Iron and Manganese
Iron and Manganese
7.
Chlorinated Hydrocarbons
(pesticides)
Chlorinated Hydrocarbons
(pesticides)
8.
Fluoride
Fluoride
9.
MBAS
MBAS
10.
Phenols
Phenols
13.5	SAFETY
Take adequate precautions to prevent falling or slipping intq
the water when sampling. Not only can this save your life, it
also will prevent muddying the sample. Choose sampling cross
sections or "stations" carefully so that safe access is possible
in winter and summer. Use snap-on safety belts when leaning
over bridge railings or stream banks. When sampling on a
bridge, be sure there is enough room for the person collecting
the samples and traffic. Wear a life preserver when sampling
from a boat; and be sure the boat is well marked with lights,
reflectors, and flags to prevent collisions. At least two people
should be in a sampling boat. When the sampler's attention is
focused on collecting samples, the other person must watch
for other watercraft.
13.6	MAINTENANCE
Effluent disposal involves very few maintenance consid-
erations except for pumps. These are discussed in Chapter 15,
"Maintenance." Metering system maintenance consists mainly
of cleaning and visual inspections. Otherwise, maintenance
requires good housekeeping at all time.
10 Fixed. A sample is "fixed" in the field by adding chemicals that prevent the water quality indicator of interest in the sample from changing
before final measurements are performed in the lab.	*

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Effluent Disposal 201
13.7 REVIEW OF PLANS AND SPECIFICATIONS
A careful review of plans and specifications by an operator
can provide the design engineer with helpful suggestions.
These suggestions can produce a plant that is easier to oper-
ate and maintain.
1.	Flow Meters
Plant effluent flow rates may be measured in either open
channels or pipelines. Parshall flumes, weirs or similar devices
are used to measure flows in open channels and pipes flowing
partially full. Magnetic flow meters and Venturi meters are used
to measure flows in pipes, flowing completely full or under
pressure. Magnetic flow meters require an auxiliary power
source, but Venturi meters do not require any power.
2.	Outfall
The plant effluent should be discharged below the surface of
the receiving waters at all times to prevent complaints from
foaming and discoloration of the receiving waters. Inspect the
actual location in the field. Be sure the outfall is below low
water levels and the discharge conditions (such as location of
river channel) will not change in the near future. In areas near
oceans, the river level may fluctuate due to tidal action.
If the submerged outfall has a number of outlet ports or
diffusers, determine if any maintenance will be necessary. If
so, decide how to do the maintenance job and determine if
there might be an easier way. Be sure a cleanout is located
near the end of the outfall and is easily accessible. Often a
minimum outlet flow or velocity must be maintained to prevent
diffusers from clogging. Determine if minimum plant flows dur-
ing start-up or low-flow periods will be adequate to prevent
clogging. Maintenance consists of clearing outlet ports of any
debris that gets into the effluent channels and removing any silt
deposits or debris left by the river.
Sometimes receiving waters become very high during flood
conditions. Determine if the plant effluent pumps have suffi-
cient capacity and discharge head to perform as intended if the
plant receives high inflows when flood conditions exist in the
receiving waters.
3. Emergency Storage
What happens if your plant's chlorination facilities do not
work or other treatment processes are unable to provide
adequate treatment? Newer plants are being constructed with
emergency storage basins to hold peak storm runoff or in-
adequately treated wastewater until this wastewater can be
properly treated by the plant. If receiving waters serve as a
source for a downstream domestic water supply or other use
requiring high quality water, construction of an emergency
storage basin can be very important.
13.8	OTHER TYPES OF RECEIVING WATERS
This chapter on effluent disposal by dilution has emphasized
very simple examples of flowing streams or rivers. Some other
types of receiving waters you may encounter are:
1.	Oceans
2.	Estuaries
3.	Groundwaters
4.	Lakes
These receiving waters usually require a more sophisticated
approach to sampling and measurement of characteristics.
The basic rules are the same, however, for sample selection
and collection techniques. The best answer to sampling these
types of receiving waters is to seek advice from a consultant, a
regulatory agency, or other experts on where and how to sam-
ple and on how to evaluate the results.
13.9	ADDITIONAL READING
1.	MOP 11, Chapter 25, "Effluent Disposal."*
2.	NEW YORK MANUAL, Chapter 11, "Sampling and Testing
Procedures."
3.	STANDARD METHODS FOR EXAMINATION OF WATER
AND WASTEWATER, produced by APHA, AWWA, and
WPCF, Water Pollution Control Federation, 2626 Pennsyl-
vania Avenue, N.W., Washington, D.C. 20037. Price
$28.00 to members, prepaid only; otherwise $35.00. Indi-
cate your member association when ordering.
'Depends on edition
QUESTIONS
Write your answers in a notebook and then compare your
answers with those on page 202.
13.4A What is a "fixed" sample?
13.5A What safety precautions should be taken when sam-
pling?
13.6A What are the most important maintenance consid-
erations for effluent disposal systems?
13.7A What items should be examined when reviewing the
plans and specifications for an effluent disposal sys-
tem?

-------
202 Treatment Plants
DISCUSSION AND REVIEW QUESTIONS
Chapter 13. EFFLUENT DISPOSAL
Please write the answers to these questions in your
notebook.
1.	Why should receiving waters be sampled?
2.	Can a treatment plant operate as effectively as possible
and still have a bad effect on the receiving waters? Why?
3.	Why are receiving waters measured upstream from the
point of discharge?
4.	Where should samples be collected in the cross section of
a stream at a particular sampling location? Assume you
are trying to find the point in the section which will give you
a representative measurement of the entire section.
5.	Why should more than one sampling station be estab-
lished downstream from the point of wastewater dis-
charge?
6.	What does the term "representative sample" mean?
7.	What is a major concern regarding sample water quality
AFTER the sample has been collected?
8.	How large a sample should be collected?
9.	What information should be included on a sample label?
10.	What safety precautions should be taken when sampling
from a bridge?
11.	How would you determine the impact of a plant effluent on
receiving waters?
12.	Why are some water quality indicators measured in-
stream and others measured in the lab?
13.	What would you do if your plant is not meeting NPDES
permit requirements?
PLEASE WORK THE OBJECTIVE TEST NEXT.
SUGGESTED ANSWERS
Chapter 13. EFFLUENT DISPOSAL
Answers to questions on page 187.
13.OA The most common method of effluent disposal is by
dilution in receiving waters.
13.OB Common methods of wastewater reclamation include
disposal on land and direct or indirect reuse.
Answers to questions on page 190.
13.1 A Water quality indicators usually determined by in-
stream measurements include dissolved oxygen
(DO), pH and temperature.
13.1B Water quality indicators usually determined by sam-
ples collected in the field and analyzed in the lab in-
clude biochemical oxygen demand (BOD), suspended
solids and total coliform and tecal coliform bacteria.
Answers to questions on page 191.
13.2A Operating procedures should be developed for the fol-
lowing conditions in an effluent disposal program:
1.	Start-up
2.	Normal operation
3.	Shutdown
4.	Emergencies or abnormal conditions
13.2B An operational strategy should attempt to do every-
thing possible to minimize discharge of pollutants to
the receiving waters.
Answers to questions on page 199.
13.3A I would contact the assistant plant operator and at-
tempt to verify the results recorded. Also I would ask
the operator if anything unusual was observed while
collecting the sample.
13.3B
(c)
13.3C
(c)
13.3D
a.

b.

c.
Maximum 14.7°C and Minimum 10.5°C.
Time of maximum temperature, 4 PM; minimum
temperature 6 AM.
11 AM and 1 AM.
Answers to questions on page 201.
13.4A A "fixed" sample is a sample which has chemicals
added to prevent a particular water quality indicator
from changing before the sample can be analyzed.
13.5A Adequate safety precautions should be taken when
sampling to prevent falling or slipping into the water.
Provisions should be made to warn other watercraft
(flags). An assistant should be available to rescue
anyone falling into the water and to warn other water-
craft.
13.6A Important maintenance considerations for effluent dis-
posal systems include:
1.	Pumps,
2.	Meters, and
3.	Good housekeeping at all times.
13.7A When reviewing plans and specifications for an
effluent disposal system, consider:
1.	Flow meters,
2.	Outfall, and
3.	Emergency storage.

-------
OBJECTIVE TEST
Chapter 13. EFFLUENT DISPOSAL
Effluent Disposal 203
Please write your name and mark the correct answers on the
answer sheet as directed at the end of Chapter 1.
1.	Successful operation of an effluent disposal by dilution
system depends on proper sampling and analysis tech-
niques.
1.	True
2.	False
2.	Farmers who irrigate with treated effluent instead of
groundwater have to apply more fertilizer.
1.	True
2.	False
3.	Land disposal systems can remove unwanted materials
from the effluent of a treatment plant.
1.	True
2.	False
4.	Upstream receiving waters usually are unaffected by a
plant discharge.
1.	True
2.	False
5.	Remote sampling locations are best for a river.
1.	True
2.	False
6.	Accessible sampling locations along a river promote an
effective sampling program.
1.	True
2.	False
7.	Every sample must be identified by markings or by a label.
1.	True
2.	False
8.	All samples should be taken daily.
1.	True
2.	False
9.	A record must be made of every sample collected.
1.	True
2.	False
10.	Slipping and falling is a constant safety hazard when col-
lecting samples.
1.	True
2.	False
11.	A "fixed" sample is a standard against which other sam-
ples are compared.
1.	True
2.	False
12.	Color of receiving waters is not an important measurement
or observation.
1.	True
2.	False
13.	If a wastewater treatment plant effluent contains dissolved
oxygen (DO), it will not have an "oxygen" demand.
1.	True
2.	False
14.	pH measurement is important in a wastewater treatment
plant effluent, but not receiving waters.
1.	True
2.	False
15.	A "fixed" sample is in effect preserved until it can be prop-
erly tested.
1.	True
2.	False
16.	Dissolved gases in a receiving water sample should be
measured immediately after the sample is collected.
1.	True
2.	False
17.	Respiration by an organism is the use of oxygen and the
giving off of carbon dioxide by the organism.
1.	True
2.	False
18.	The average annual temperature for a stream can be
measured by sampling in one month out of the year.
1.	True
2.	False
19.	Receiving water measurements indicate the impact treat-
ment plant discharges have on receiving waters.
1.	True
2.	False
20.	Results from a sampling program should always be ac-
cepted without question or verification.
1.	True
2.	False
21.	Receiving water sampling requires proper
1.	Authorization by fishery agencies.
2.	Equipment and "flailing the water."
3.	Operation of wastewater treatment plants.
4.	Safety and temperature.
5.	Selection of samples and collection techniques.

-------
204 Treatment Plants
22.	Proper sample collection techniques are specified in
1.	All design manuals for concrete pipe.
2.	MOP 1.
3.	Safety precautions.
4.	STANDARD METHODS FOR THE EXAMINATION OF
WATER AND WASTEWATER.
5.	Water quality objectives.
23.	Some receiving water characteristics which should be
measured immediately after the sample is collected are
1.	Calcium and vitamins.
2.	Profiles and effluents.
3.	Sulfur and molasses.
4.	Temperature, pH, and dissolved gases.
5.	Velocity and dissolved solids.
24.	Which of the following water quality indicators are usually
"fixed" in the field?
1.	Carbon dioxide
2.	DO
3.	pH
4.	Temperature
5.	None of these
25.	Which of the following items must be put on the label of a
sample?
1.	Any sample preservatives or fixing chemicals.
2.	Date
3.	Location
4.	Name of person collecting sample
5.	Time
26.	Which of the following is a constant and major safety
hazard when collecting receiving water samples?
1.	Asphyxiation
2.	Explosion
3.	Lifting
4.	Slipping and falling
5.	Toxic gases
27.	The two types of measurements required in connection
with operating a treatment plant are
1.	Effluent and downstream.
2.	In-plant and receiving water.
3.	Temperature and dissolved oxygen.
4.	Temperature and receiving water.
5.	Upstream and downstream.
28.	To determine the location and amount of lowest dissolved
oxygen downstream from a discharge, it is necessary to
1.	"Flail the water."
2.	Make an "oxygen profile" of the stream.
3.	Make yearly measurements.
4.	Measure the effluent.
5.	Observe safety precautions.
29.	Which one of the following receiving waters requires the
most sophisticated sampling and measurement proce-
dures?
1.	A creek
2.	A lake
3.	A large stream
4.	A river
5.	A small stream
30.	Underground disposal systems may be used to
1.	Add nutrients to groundwater.
2.	Displace oil or gas that is being pumped out of the
ground.
3.	Increase the percolation rate of wastewater spreading
basins.
4.	Inhibit the growth of undesirable aquatic organisms.
5.	Provide a barrier between underground salt water and
fresh groundwater.
31.	Water quality indicators that are important for a drinking
water supply include
1.	BOD.
2.	Coliform bacteria.
3.	DO.
4.	Nitrate.
5.	Phosphate.
32.	An operator can detect adverse impacts on receiving wa-
ters from a plant effluent by observing or detecting
	 in the receiving waters. Pick correct an-
swers to fill in blank.
1.	A good settling floe
2.	Clearwater
3.	Dead fish
4.	Floating substances
5.	Odors
REVIEW QUESTIONS
33.	What is the volatile acid/alkalinity relationship in a digester
if the alkalinity is 1760 mgIL and the volatile acids are 140
mgIL?
1.	0.05
2.	0.08
3.	0.10
4.	0.50
5.	12.5
34.	A digester contains 1000 pounds of volatile matter under
digestion. If 0.05 pounds of new volatile solids can be
added per day per pound of volatile matter under diges-
tion, how many pounds of sludge solids can be added per
day with a volatile content of 70 percent?
1.	35 pounds per day
2.	50 pounds per day
3.	70 pounds per day
4.	100 pounds per day
5.	350 pounds per day
END OF OBJECTIVE TEST

-------
CHAPTER 14
PLANT SAFETY AND GOOD HOUSEKEEPING
by
Robert Reed

-------
206 Treatment Plants
TABLE OF CONTENTS
Chapter 14. Plant Safety and Good Housekeeping
Page
OBJECTIVES	208
LESSON 1
14.0	Why Safety?	209
14.1	Kinds of Hazards	209
14.10	Physical Injuries	209
14.11	Infections and Infectious Diseases	209
14.12	Oxygen Deficiency	210
14.13	Toxic or Suffocating Gases or Vapors	210
14.14	Toxic and Harmful Chemicals	210
14.15	Radiological Hazards 	210
14.16	Explosive Gas Mixture 	210
14.17	Fire	210
14.18	Electrical Shock	210
14.19	Noise 	210
14.2	Specific Hazards 	212
14.20	Collection Systems 	212
14.200	Traffic Hazards	212
14.201	Manholes	212
14.202	Excavations	214
14.203	Sewer Cleaning	214
14.21	Pumping Stations	215
14.22	Treatment Plants	215
14.220	Headworks 	215
14.221	Grit Channels	219
14.222	Clarifiers or Sedimentation Basins	 	219
14.223	Digesters and Digestion Equipment	219
14.224	Trickling Filters	221
14.225	Aerators		
14.226	Ponds	222

-------
Safety 207
14.227	Chlorine	222
14.228	Applying Protective Coatings	223
14.229	Housekeeping	223
14.23 Industrial Waste Treatment 	223
14.230	Fuels 	223
14.231	Toxic Gases	223
14.232	Amines	224
14.233	Surface-active Agents	224
14.234	Biocides	224
14.235	High or Low pH 	224
14.236	Summary	224
LESSON 3
14.3	Safety in the Laboratory	225
14.30	Sampling Techniques	225
14.31	Equipment Use and Testing Procedures	225
14.4	Fire Prevention	226
14.40	Ingredients Necessary for a Fire	226
14.41	Fire Control Methods	227
14.42	Fire Prevention Practices	227
14.43	Acknowledgment 	227
14.5	Water Supplies	227
14.6	Safety Equipment and Information	229
14.7	"Tailgate" Safety Meetings 	229
14.8	How to Develop Safety Training Programs	229
14.80	Conditions for an Effective Safety Program 	229
14.81	Start at the Top 	230
14.82	Plan for Emergencies	230
14.83	Promote Safety	230
14.84	Hold Safety Drills and Training Courses	230
14.85	Purchase the Obvious Safety Equipment First 	230
14.86	Safety is Important for Everyone 	230
14.87	Necessary Paper Work	230
14.88	Train for Safety	231
14.89	Safety Summary	231
14.9	Summary	231
14.10	Additional Reading	232

-------
208 Treatment Plants
OBJECTIVES
Chapter 14. PLANT SAFETY AND GOOD
HOUSEKEEPING
Following completion of Chapter 14, you should be able to:
1.	Identify the kinds of hazards you may encounter operating a
wastewater treatment plant.
2.	Recognize unsafe conditions and correct them whenever
they develop,
3.	Organize regular "tailgate" safety meetings, and
4.	Develop the habit of always THINKING SAFETY.
NOTE: Special safety information is given in other chapters
because of the importance of safety considerations
at all times.
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-------
Safety 209
CHAPTER 14. PLANT SAFE
(Lesson 1
14.0 WHY SAFETY?
A cat may have nine lives, but you have only one! Protect it!
Others may try, but only your efforts in thinking and acting
safely can ensure you the opportunity of continuing to live your
one life!
You are working at an occupation that has an accident fre-
quency rate second only to that of the mining industry! This is
not a very desirable record.
Your employer has the responsibility of providing you with a
safe place to work. But you, the operator who has overall re-
sponsibility for your treatment plant, must accept the task of
seeing to it that your plant is maintained in such a manner as to
continually provide a safe place to work. This can only be done
by constantly ACTING AND THINKING SAFETY.
You have the responsibility of protecting yourself and other
plant personnel or visitors by establishing safety procedures
for your plant and then by seeing that they are followed. Train
yourself to analyze jobs, work areas, and procedures from a
safety standpoint. Leam to recognize potentially hazardous
actions or conditions. When you do recognize a hazard, take
immediate steps to eliminate it by corrective action. If correc-
tion is not possible, guard against the hazard by proper use of
warning signs and devices and by establishing and maintain-
ing safety procedures. As an individual, you can be held liable
for injuries or property damage as a result of an accident
caused by your negligence.
•SAfEtV

AND GOOD HOUSEKEEPING
3 Lessons)
REMEMBER: "ACCIDENTS DON'T JUST HAPPEN —
THEY ARE CAUSED"!! How true it is! Behind every accident
there was a chain of events which led to an unsafe act, unsafe
condition, or a combination of both. THINK SAFETY!
Accidents may be prevented by using good common sense,
applying a few basic rules, and particularly by acquiring a good
knowledge of the hazards peculiar to your job as a plant
operator.
The Bell System has one of the best safety records of any
industry. A variation of their successful policy statement is:
"THERE IS NO JOB SO IMPORTANT NOR
EMERGENCY SO GREAT THAT WE CANNOT TAKE
TIME TO DO OUR WORK SAFELY."
Although this chapter is intended primarily for the wastewa-
ter treatment plant operator, the operators of many small
plants also have the responsibility of sewer maintenance.
Therefore the safety aspects of both sewer maintenance and
plant operation will be discussed.
14.1 KINDS OF HAZARDS
You are equally exposed to accidents whether working on
the collection system or working in a treatment plant. As a
worker, you may be exposed to:
1.	Physical injuries
2.	Infections and infectious diseases
3.	Oxygen deficiency
4.	Toxic or suffocating gases or vapors
5.	Radiological hazards
6.	Explosive gas mixtures
7.	Fire
8.	Electrical shock
9.	Noise
14.10	Physical Injuries
The most common physical injuries are cuts, bruises, burns,
crushing, and broken bones. Injuries can be caused by moving
machinery. Falls from or into tanks, deep wells, catwalks, or
conveyors can be disabling. Most of these can be avoided by
the proper use of ladders, hand tools, and safety equipment,
and by following established safety procedures. Slips and falls
are probably the greatest cause of injuries in wastewater
treatment plants.
14.11	Infections and Infectious Diseases1
Although treatment plants and plant personnel are certainly
not expected to be "pristine pure," personal cleanliness greatly
reduces the risk of infections and infectious diseases. Immuni-
zation shots for protection against typhoid and tetanus are
essential.
1 You MUST attempt to avoid skin infections and infectious diseases such as typhoid fever, dysentery, hepatitis, and tetanus.

-------
210 Treatment Plants
Make it a habit to thoroughly wash your hands before eating
or smoking, as well as before and after going to the toilet. If you
have any cuts or other broken skin areas on your hands, wear
proper protective gloves when in contact with wastewater or
sludge in any form. Bandages covering wounds should be
changed frequently.
Do not wear your work clothes home because diseases may
be transmitted to your family. Provisions should be made in
your plant for a locker room where each employee has a
locker. Work clothes should be placed or hung in lockers and
not thrown on the floor. Your work clothes should be cleaned at
least weekly or more often if necessary.
If your employer does not supply you with uniforms and
laundry sen/ice and you must take your work clothes home,
launder them separately from your regular family wash.
All of these precautions will reduce the possibility of you and
your family becoming ill because of your contact with wastewa-
ter.
What is wrong with the above sketch? NEVER stick objects
in your mouth that you do not intend to eat.
14.12 Oxygen Deficiency
Low oxygen levels may exist in any enclosed, unventilated
structure where gases such as hydrogen sulfide are produced.
This is particularly true when the structure is below grade
(ground level).
Ventilation may be provided by fans or blowers. Get air into
any hole BEFORE you go down to work and keep air coming
until you have left the work area. Equipment is available to
measure oxygen deficiency and must be used whenever you
enter a potentially hazardous area. Try your local fire depart-
ment for sources of this type of equipment in your area.
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14.13	Toxic or Suffocating Gases or Vapors
Toxic or suffocating gases may come from industrial waste
discharges or from the decomposition of domestic wastewater.
You must become familiar with the waste discharges into your
system. Table 14.1, Common Dangerous Gases Encountered
in Sewers and at Sewage Treatment Plants, contains informa-
tion on the simplest and cheapest safe method of testing for
gases.
14.14	Toxic and Harmful Chemicals
Strong acids, bases and liquid mercury are types of toxic
and harmful chemicals that operators may encounter working
in and around treatment plants and laboratories. Be very care-
ful when handling and using these chemicals.
14.15	Radiological Hazards
The newest of hazards to plant operators is a result of the
increasing use of radioactive isotopes in hospitals, research
labs, and various industries. Check your sewer service area for
the possible use of these materials. If you are receiving a
discharge that may contain a radioactive substance, contact
the contributor of the discharge. The discharger will usually
cooperate with you in monitoring this type of waste. Radioac-
tive wastes can be monitored with a Geiger Counter or an
ionization-chamber type of lab instrument that measures the
level of radioactivity.
Some sludge density meters contain a radioactive isotope to
measure the thickness of the sludge being pumped. Normally
these meters have adequate safeguards. However, if a meter
is damaged or does not perform properly, contact the equip-
ment manufacturer for instructions. Operators working with
density meters containing radioactive materials must be
trained by the manufacturer and certified as competent to use,
calibrate and maintian the meter.
14.16	Explosive Gas Mixtures
Explosive gas mixtures may develop in confined areas in
treatment plants from mixtures of air and methane, natural gas,
manufactured fuel gas, or gasoline vapors. Explosive ranges
can be detected by using a combustible gas indicator. Avoid
explosions by keeping open flames away from areas poten-
tially capable of developing explosive mixtures by providing
adequate ventilation with fans or blowers.
14.17	Fire
Burns from fires can cause very serious injury. Avoid build
up of flammable material and store any material of this type in
approved containers at proper locations. Know the location of
fire fighting equipment and the proper use of the equipment.
14.18	Electrical Shock
Electrical shock frequently causes serious injury. Do not at-
tempt to repair electrical equipment unless you know what you
are doing. You must be qualified and authorized to work on
electrical equipment before you attempt any troubleshooting or
repairs.
14.19	Noise
Loud noises from gas engines and gas or electric blowers
can cause permanent ear damage. Operators and mainte-
nance workers must wear the proper ear protecting devices
whenever working in noisy areas for any length of time.

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Safety 211
TABLE 14.1 COMMON DANGEROUS GASES ENCOUNTERED IN WASTEWATER COLLECTION
SYSTEMS AND AT WASTEWATER TREATMENT PLANTS1


Specific
Gravity
Explosive
Range (% by
volume in air)
Common Properties
Physiological Effects

Simplest and
Cheapest Safe
Method of Testing t
Name
of Gas
Chemical
Formulae
of Vapor
Density"
(Air = 1)
Lower
Limit
Upper
Limit
(Percentages below
are per cent in air
by volume)
(Percentages below
are per cent in air
by volume)
Most Common
Sources in Sewers
Oxygen
(In Air)
o,
1.11
Not flammable
Colorless, odorless,
tasteless, non-
poisonous gas. Sup-
ports combustion.
Normal air contains
20.93% of 02. Man
tolerates down to
12%. Below 5 to
7% likely to be
fatal.
Oxygen depletion
from poor ventila-
tion and absorption
or chemical
consumption of
available 02.
Oxygen deficiency
indicator.
Gasoline
Vapor
c5h,2
to
c,h20
3.0 to
4.0
1.3
7.0
Colorless, odor
noticeable in 0.03%.
Flammable.
Explosive.
Anesthetic effects
when inhaled.
2.43% rapidly fatal.
1.1% to 2.2%
dangerous for even
short exposure.
Leaking storage
tanks, discharges
from garages, and
commercial or home
dry-cleaning
operations.
1.	Combustible gas
indicator.
2.	Oxygen defi-
ciency indicator
for concentrations
over 30%.
Carbon
Monoxide
CO
0.97
12.5
74.2
Colorless, odorless,
non-irritating,
tasteless,
Flammable.
Explosive.
Hemoglobin of
blood has strong
affinity for gas
causing oxygen
starvation. 0.2 to
0.25% causes
unconsciousness in
30 minutes.
Manufactured
fuel gas.
CO ampoules.
Hydrogen

0.07
4.0
74.2
Colorless, odorless,
tasteless, non-
poisonous, flam-
mable. Explosive.
Propagates flame
rapidly ; very
dangerous.
Acts mechanically
to deprive tissues of
oxygen. Does not
support life. A
simple asphyxiant.
Manufactured
fuel gas.
Combustible gas
indicator.
Methane
ch4
0.55
5.0
15.0
Colorless, tasteless,
odorless, non-
poisonous. Flam-
mable. Explosive.
See hydrogen.
Natural gas, marsh
gas, mfg. fuel gas,
sewer gas.
1.	Combustible gas
indicator.
2.	Oxygen defi-
ciency indicator.
Hydrogen
Sulfide
h2s
1.19
4.3
46.0
Rotten egg odor in
small concentrations
but sense of smell
rapidly impaired.
Odor not evident at
high concentrations.
Colorless. Flam-
mable. Explosive.
Poisonous.
Death in few
minutes at 0.2%.
Paralyzes
respiratory center.
Petroleum fumes,
from blasting,
sewer gas.
1.	H2S analyzer.
2.	H2S ampoules.
Carbon
Dioxide
COj
1.53
Not flammable
Colorless, odorless,
non-flammable. Not
generally present in
dangerous amounts
unless there is
already a deficiency
of oxygen.
10% cannot be
endured for more
than a few minutes.
Acts on nerves of
respiration.
Issues from
carbonaceous strata.
Sewer gas.
Oxygen deficiency
indicator.
Nitrogen
n2
0.97
Not flammable
Colorless, tasteless,
odorless. Non-
flammable. Non-
poisonous. Principal
constituent of air
(about 79%).
See hydrogen.
Issues from some
rock strata.
Sewer gas.
Oxygen deficiency
indicator.
Ethane
c2h4
1.05
3.1
15.0
Colorless, tasteless,
odorless, non-
poisonous. Flam-
mable. Explosive.
See hydrogen.
Natural gas.
Combustible gas
Indicator.
Chlorine
Cl2
2.5
Not flammable
Not explosive
Greenish yellow
gas, or amber color
liquid under
pressure. Highly
Irritating and
penetrating odor.
Highly corrosive
in presence of
moisture.
Respiratory irritant,
irritating to eyes
and mucous mem-
branes. 30 ppm
causes coughing.
40-60 ppm danger-
ous in 30 minutes.
1000 ppm apt to be
fatal in few breaths.
Leaking pipe
connections.
Overdosage.
Chlorine detector.
Odor, strong.
Ammonia on swab
gives off white
fumes.
" Gases with a specific gravity less than 1.0 are lighter than air; those more than 1.0 heavier than air.
t The first method given is the preferable testing procedure.
1. Reprinted from Water and Sewage Works, August 1953.
Copied from "Manual of Instruction for Sewage Treatment Plant Operators," State of New York.

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212 Treatment Plants
QUESTIONS
Write your answers in a notebook and then compare your
answers with those on page 234.
14.1 A How can you prevent the spread of infectious dis-
eases from your job to you and your family?
14.1B What should you do BEFORE entering an unventi-
lated, enclosed structure?
14.1C What are potential sources of toxic or suffocating
gases or vapors?
14.2 SPECIFIC HAZARDS
In the remainder of this chapter an attempt will be made to
acquaint you with the specific hazards, by location and/or
types of work, that you may expect to encounter in the field of
wastewater collection and treatment.
14.20 Collection Systems
Good design and the use of safety equipment will not pre-
vent physical injuries in sewer work unless safety practices are
understood by the ENTIRE CREW and are enforced.
Never attempt to do a job unless you have sufficient help,
the proper tools, and the necessary safety equipment. THERE
ARE NO SHORTCUTS TO SAFETY!
14.200	Traffic Hazards
Before starting any job in a street or other traffic area, even if
you are just going to open a manhole, study the work area and
PLAN YOUR WORK. Adequate warning to and protection from
traffic MUST be provided. Try to avoid working during periods
of rush-hour traffic.
Traffic may be warned by high-level signs and flags far
enough ahead (500 feet or 150 meters) of the job to
adequately alert the driver, by traffic cones (the newer fluores-
cent red cones do an excellent job) arranged to guide traffic
around your work area, by signs or barricades to direct traffic,
by a flagman to direct and control traffic, or by any combination
of these. The local police department, state highway police, or
road department may be able to provide you with some basic
patterns on the use of cones, barricades, and other warning or
traffic control devices. Traffic warning devices must be placed
in such a fashion as to avoid causing confusion and conges-
tion.
An added protection, whenever possible, is to place your
work vehicle between you and the oncoming traffic. Be sure
the vehicle is far enough ahead of a manhole so that if the
vehicle is bumped, it will not cover the manhole in which you
are working. This will alert traffic to your presence. The use of
flashing or revolving amber or red warning lights (whichever
color is permissible in your area) is an excellent means of
alerting traffic to your presence.
14.201	Manholes2
Manhole work usually requires job site protection by bar-
ricades and warning devices. These devices are necessary to
warn highway traffic and pedestrians for the protection of the
public and the workers.
Never use your fingers or hands to remove a manhole lid!
Always use a tool such as a pick with the point bent in the form
of a hook, or a special tool specifically designed for this pur-
pose. You have only ten fingers. Protect them! When lifting a
lid, the use of the rule "Lift with your legs, not with your back"
will help eliminate back strains (Fig. 14.1). Once the lid is re-
moved, leave it flat on the ground and far enough away from
the manhole to provide adequate room for a working area. This
is usually at least two to three feet (0.6 to 1 m).
If there are ladder rungs or steps installed in the side of the
manhole, be very cautious when using these. Be alert for loose
or corroded steps. Always test each step individually before
placing your weight upon it. If possible, it is much safer to use a
ladder as a means of entering a manhole. Be certain, however,
that the bottom feet are properly placed so that the ladder will
not slip or twist when your weight is placed upon it. A special
truck winch or lift is the safest possible way to be lowered into a
manhole, wet well, or other below grade work area or to be
lifted to an elevated work area.
NO ONE SHOULD ENTER A MANHOLE ALONE. There
should always be at least one person standing by at the top of
the manhole to observe the person entering, working, and leav-
ing the manhole. There should always be AT LEAST ONE
MORE PERSON WITHIN HEARING DISTANCE of the man-
hole in case it is necessary to remove the person from the
manhole because of injury. A truck winch or lift also may be
used to remove an injured person from a manhole.
Before entering a manhole, put on an approved safety har-
ness equipped with a hand line or life line. Both of these should
be inspected by a fellow worker as well as the wearer. Be sure
to wear a safety hat or cap.
If you are working in wastewater, be sure to wear a properly
fitted pair of rubber gloves and boots, or an approved substi-
tute that will provide protection from infection.
2 Also see "Safe Procedure No. 1, Preparation lor Manhole Work,'' Journal, Water Pollution Control Federation, Vol. 42, No. 2, p. 331.
(February, 1970).

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214 Treatment Plants
Never enter a manhole without first checking for explosive
gases, hydrogen sulfide or other gases that may cause an
oxygen deficiency. PROVIDE FOR ADEQUATE VENTILATION
TO REMOVE THESE GASES BEFORE ENTERING A MAN-
HOLE. There are instruments available that can detect explo-
sive gases or oxygen deficiency. Your local fire department
can usually supply you with information on this type of equip-
ment. For detailed information on measurements of dangerous
concentrations of gases, refer to Table 14.1, Common
Dangerous Gases Encountered in Wastewater Collection Sys-
tems and at Wastewater Treatment Plants.
Tools and equipment should be lowered into a manhole by
means of a bucket or basket. Do not drop them into the man-
hole for the person in the hole to catch. Attempting to carry
tools in one hand while climbing down a ladder is an unsafe
practice.
14.202	Excavations3
If it becomes necessary for you to excavate a sewer line,
become familiar with the fundamentals of excavating and the
proper, safe approach for shoring a ditch. Check with your
State Safety Office or Industrial Accident Commission. They
can usually provide you with pamphlets on these subjects.
Don't wait until an emergency arises to obtain the information.
14.203	Sewer Cleaning
Never use a cleaning tool or piece of equipment unless you
have been properly trained in its use or operation. Insist that
the vendor provide you with this training. Know the limitations
and capabilities of your tools and equipment. Do not use tools
or equipment improperly because you could be seriously in-
jured.
If you use chemicals of any kind for root or grease control in
your system, be thoroughly familiar with their use, and specif-
ically, with any hazards involved.
QUESTIONS
Write your answers in a notebook and then compare your
answers with those on page 234.
14.2A Why should someone always be standing at the top of
a manhole when you enter it?
14.2B How would you determine if there is an oxygen defi-
ciency or toxic gas present in a manhole?
14.2C From whom should you learn the proper use of new
sewer cleaning equipment?
14.2D List three ways to alert traffic that you are working in a
street or traffic area.
END OF LESSON 1 OF 3 LESSONS
on
PLANT SAFETY AND GOOD HOUSEKEEPING
Please answer the discussion and review questions before
continuing with Lesson 2.
DISCUSSION AND REVIEW QUESTIONS
Chapter 14. PLANT SAFETY AND GOOD HOUSEKEEPING
(Lesson 1 of 3 Lessons)
At the end of each lesson in this chapter you will find some
discussion and review questions that you should work before
continuing. The purpose of these questions is to indicate to you
how well you understand the material in this lesson.
Write the answers to these questions in your notebook.
1.	What is the operator's responsibility with regard to safety?
2.	Accidents don't just happen — they are 		!
3.	How can an operator avoid physical injuries?
4.	Immunization shots protect against what infection and in-
fectious disease?
5.	What precautions should you take to avoid transmitting dis-
ease to your family?
6.	What should you do when you discover an area with an
oxygen deficiency?
7.	What kind of job site protection is usually required when you
are working in a manhole?
8.	Lift with your legs, not your	
9.	How should tools and equipment be transported to the bot-
tom of a manhole?
3 Also see 'Wastewater Wisdom Talk, Trench Shoring," Jour. Water Poll. Control Fed., Vol. 42, No. 6, p 1273 (June 1970).

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CHAPTER 14.
PLANT SAFETY AND GOOD HOUSEKEEPING
(Lesson 2 of 3 Lessons)
Safety 215
14.21 Pumping Stations
Pumping stations may vary from small, telemetered lift sta-
tions that are visited monthly to large pumping stations that
have operators on duty 24 hours a day. Regardless of the size,
type or complexity of the pumping station, safe procedures
must be followed at all times. Safety precautions discussed in
Section 14.201, "Manholes," are very important for work in any
confined space, including both wet wells and dry wells.
Always be aware of the possibility of toxic, explosive or
flammable gases that could be discharged into the sewers or
generated in the sewers. A properly operating ventilation sys-
tem is essential, particularly in underground pumping stations
where heavier-than-air gases may collect. Before entering a
confined space in an unattended lift station, test the atmos-
phere for an oxygen deficiency, explosive or flammable condi-
tions (Lower Explosive Limit) and toxic gases (hydrogen sul-
fide).
Do not touch electrical systems or controls unless you are an
expert. Even if you are qualified and authorized, use caution
when operating and maintaining electrical controls, circuits and
equipment. Operate only those switches and electrical controls
installed for the purpose of your job. Do not open or work inside
electrical cabinets or switch boxes unless you are authorized
and a qualified electrician.
Be aware of moving equipment, especially reciprocating
equipment and rotating shafts. Guards over couplings and
shafts should be provided and should be in place at all times.
Do not wear loose clothing and rings and other jewelry around
machinery. Long hair must be secured. Wear gloves when
cleaning pump casings to protect your hands from dangerous
sharp objects.
When starting rotating equipment after a shutdown, every-
one should stand away from rotating shafts. Dust and oil or
loose metal may be thrown from shafts and couplings, or sec-
tions of a long vertical shaft could come loose and whip
around, especially during start-up of equipment.
If stairs are installed in a pumping station, they should have
hand rails and non-slip treads. Where space limitations pre-
vent the installation of stairs, a spiral stairway, ship's ladder, or
vertical ladder should be provided. Vertical ladders should be
provided with a hoopage enclosure. If the ladder is 8 feet (2.4
m) in height, intermediate platforms or landings should be pro-
vided.
Electric lights should be sufficient in number and properly
located to avoid glare and shadows.
Fire extinguishers should be provided in the station, properly
located and maintained. They should be of a type that may be
used on electrical equipment as well as on solid material
and/or power overload-type fires. The use of liquid-type fire
extinguishers should be avoided. All-purpose A-B-C
Chemical-type fire extinguishers are recommended.
Good housekeeping is a necessity in a pumping station.
Common housekeeping problems include water and oil on the
floor, dirty or oily rags from cleanup operations, poor vision
caused by dirty lighting fixtures, and stairways with dirt or
grease carried in by maintenance or repair crews.
Always be sure you have properly secured an unattended lift
station when you leave. This procedure is necessary to pre-
vent injury to a neighborhood child and possible vandalism to
the station. Both of these problems can be very costly to your
employer if proper precautions are not taken.
QUESTIONS
Write your answers in a notebook and then compare your
answers with those on page 234.
14.2E What types of moving equipment should you be aware
of in a pumping station and what safety precautions
should be taken to protect yourself from injury?
14.2F What type of fire extinguisher should be available in a
pumping station?
14.22 Treatment Plants
Because hazards found in pumping stations are similar to
those found in treatment plants, the items discussed below
may be applied to both situations. Safety precautions outlined
in the previous section apply both to pumping stations and
treatment plants.
14.220 Headworks
Structures and equipment in this category may consist of bar
screens, racks, comminuting or grinding equipment, pump
rooms, wet pits, and chlorination facilities.
1. BAR SCREENS OR RACKS. These may be either manu-
ally or automatically cleaned. When manually cleaning
screens or racks, be certain that you have a clean, firm
surface to stand upon. Remove all slimes, rags, greases, or
other material that may cause you to slip. GOOD HOUSE-
KEEPING IN THESE AREAS IS ABSOLUTELY NECES-
SARY!
When raking screens, leave plenty of room for the length
of your rake handle so you won't be thrown off balance if the
handle strikes a wall, railing, or light fixture. Wear gloves to
avoid slivers from the rake handle or scraping your knuck-
les on concrete. Injury may allow an infection to enter your
body.
Place all material in a container that may be easily re-
moved from the structure. Be careful lifting containers full of
heavy material such as grit. Do not allow material to build up
on the working surface.
If your rack area is provided with railings, check to see
that they are properly anchored before you lean against
them. If removable safety chains are provided, never use
these to lean against or as a means of providing extra
leverage for removing large amounts of material.
A hanging or mounting bracket of some type should be
used to hold the rake when not in use. Do not leave it lying
on the deck.
If mechanically raked screens or racks are installed,
never work on the electrical or mechanical part of this
equipment without first turning the unit off by means of a
push-button lockout for momentary stoppages. When you

-------
216 Treatment Plants
need to remove parts or make a major adjustment to repair
the unit, always turn off, lock out and tag the main circuit
breaker before you begin repairs.
THE TAG SHOULD BE SECURELY FASTENED TO
THE BREAKER HANDLE AND SHOULD SAY SOME-
THING LIKE "DANGER. ... DO NOT START. . . .
OPERATOR WORKING ON EQUIPMENT" (SEE FIG-
URES 14.2 AND 14.3).
The time and date the unit was turned off should be noted
on the tag, as well as the reason it was turned off. The tag
should be signed by the person who turned the unit off. No
one should then turn on the main breaker and start the unit
until the tag has been removed by the person who placed it
there, or until specific instructions are received from the
person who tagged the breaker. Your local safety equip-
ment supplier can obtain these tags for you.
2.	COMMINUTING OR GRINDING EQUIPMENT. This
equipment may consist of barminutors, comminutors,
grinders, or disintegrators.
NEVER work on the mechanical or electrical parts of the
unit without first locking out the unit at either a push-button
lockout or the main circuit breaker of the control panel. Be
certain the breaker is properly tagged as explained in the
previous section.
Good housekeeping is essential in the area of comminut-
ing equipment. Keep all walking areas clean and free of
slimes, oils, greases, or other materials. Hose down all
spills immediately. Provide a proper place for equipment
and tools used in this area.
See that proper guards are installed and kept in place
around cables, cutters, hoists, revolving gears, and high-
speed equipment such as grinders. If it is necessary to
remove the guards prior to making adjustments on equip-
ment, be certain that they are reinstalled before restarting
the unit.
3.	PUMP ROOMS. The same basic precautions apply here as
they do to any type of enclosed room or pit where wastewa-
ter or gases may enter and accumulate.
Always provide adequate ventilation to remove gases
and supply oxygen. If the room is below ground level and
provided with only forced-air ventilation, be certain the fan
is on before entering the area. Wear a harness with a safety
line (as for manhole work) when entering pits, wet wells,
tanks, and below-ground pump rooms.
The tops of all stairwells or ladders should be protected
by a removable safety chain. Keep this chain in place when
the stairwell or ladder is not being used.
Never remove guards from pumps, motors, or other
equipment without first locking out or turning off equipment
at main breaker and properly tagging. Always replace all
guards before starting units.
Guards should be installed around all rotating shaft cou-
plings, belt drives, or other moving parts normally accessi-
ble.
Maintain good housekeeping in pump room. Remove all
oil and grease, and clean up spills immediately.
If you have a multi-level pump building, never remove
and leave off equipment removal hatches unless you are
actually removing or replacing equipment. Be sure to pro-
vide barricades or ropes around the opening to prevent
falls. Be extremely cautious when working around openings
that have raised edges. These are hazardous because you
can stumble over them easily.
Never start a positive displacement pump against a
closed valve. On piston pumps, the yoke over the ball check
could break and endanger personnel in the vicinity.
All emergency lights used in these areas should be ex-
plosion-proof. Be sure to keep light shields in place and
replace immediately when broken. Permanent lights should
be of an approved explosion-proof type. UNTIL THE AREA
HAS BEEN CHECKED FOR AN EXPLOSIVE ATMOS-
PHERE, NO OPEN FLAMES (SUCH AS A WELDING
TORCH) OR SMOKING SHOULD BE ALLOWED.
	J CAUTION 	
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4. WET PITS - SUMPS. Covered wet pits or sumps are poten-
tial death traps. Never enter one by yourself. Use a safety
harness and have sufficient personnel available to lift you
out. Always use forced air to ventilate the area, and check
for explosive gases and oxygen deficiency before entering.
Also, be particularly alert for hydrogen sulfide gas. Use your
nose initially, but do not continue to depend upon it as you
will become insensitive to the odor. A small, reasonably
priced hydrogen sulfide detection unit may be purchased.
Check with your local safety equipment supplier.
After you have checked and found the atmosphere is
safe, use extreme care in climbing up and down access
ladders to pit areas. The application of a nonslip coating on
ladder rungs is helpful. If available, a truck hoist is safer
than a ladder for entering pit areas.
Watch your footing on the floor of pits and sumps. They
are very slippery.
Never attempt to carry tools or equipment up or down
ladders into pits or sumps. Always use a bucket and hand-
line or a sling for this purpose.
Only explosion-proof lights and equipment should be
used in these areas.
A good safety practice is to turn off all chlorination,
whether located upstream or directly in the sump, and allow
ample time before entering the area. This, with forced venti-
lation, will give time for the area to be cleared of chlorine
fumes.
Chlorination safety is discussed in Chapter 10, "Disinfec-
tion and Chlorination."
QUESTIONS
Write your answers in a notebook and then compare your
answers with those on page 234.
14.2G Why should slimes, rags, or greases be removed from
around bar screens or racks?
14.2H What precautions would you take when working on
electrical or mechanical equipment?

-------
>
Safety 217
o
J-**
V DO NOT ^
START
THIS EQUIPMENT
BEING
REPAIRED
STATE COMPENSATION
INSURANCE FUND
OF
CALIFORNIA
A-l
Fig. 14.2 Typical warning tag
(Sourer SUUs Compontatlon Fund of Ctffforota)

-------
218 Treatment Plants
DANGER
MAN
WORKING
ON LINE
DO NOT CLOSE THIS
SWITCH WHILE THIS
TAG IS DISPLAYED
SIGNATURE: 		
This is the ONLY person authorized to remove this tag.
INDUSTRIAL INDEMNITY/INDUSTRIAL UNDERWRITERS/
INSURANCE COMPANIES
4E210—R66
Fig. 14.3 Typical Warning Tag (Con't.)
(Souroa: Industrial Indwnntty/lndutotal Undxwrttwa/lMtiranM Co*.)

-------
Safety 219
14.2I What parts of equipment should have guards installed
around them?
14.2J Why should you not depend on your nose to detect
hydrogen sulfide gas over long periods of time?
14.2K How would you transport tools or equipment into or
out of pits or sumps?
14.221 Grit Channels
Grit channels may be of various designs, sizes, and shapes,
but they all have one thing in common: THEY GET DIRTY.
Good housekeeping is needed! Keep walking surfaces free of
grit, grease, oil, slimes, or other material that will make a slip-
pery surface.
Before working on mechanical or electrical equipment, be
certain that it is turned off and properly tagged (Figs. 14.2 and
14.3). Install and maintain guards on gears, sprockets, chains,
or other moving parts that are normally accessible.
If it becomes necessary to enter the channel, pit, or tank for
cleaning or other work, do so with extreme caution. If this is a
covered area, provide and maintain adequate ventilation to
remove gases from the area and to supply oxygen to the work-
ers. Use only explosion-proof lights. Always check for explo-
sive gases and oxygen deficiency before entering.
Be sure of your footing when working in these structures.
RUBBER BOOTS WITH A NONSKID CLEAT-TYPE SOLE
SHOULD BE WORN. STEP SLOWLY AND CAUTIOUSLY as
there is usually an accumulation of slippery material or slimes
on the bottom. Use hand holds and railings; if none are avail-
able, install them now.
Use ladders, whether vertical or ships' ladders, cautiously. If
possible, apply nonslip material or coatings to ladder rungs.
Keep handrails free of grease and other slippery substances.
If it is necessary to take tools or equipment into the bottom
area, lower these in a bucket or sling by handline. Never at-
tempt to carry items up or down a ladder.
14.222 Clarlflers or Sedimentation Basins
The greatest hazard involved in working on or in a clarifier Is
the danger of slipping. H possible, maintain a good non-skid
surface on all stairs, ladders, and catwalks. This may be done
by using nonskld strips or coating. Be extremely cautious dur-
ing freezing weather. A small amount of ice can be very
dangerous. Be careful and don't fall in.
Your housekeeping program should include the brushing or
cleaning of effluent weirs and launders (effluent troughs).
When it is necessary to actually climb down into the launder,
always wear a harness with a safety line and have someone
with you. A fall may result in a very serious injury.
Be cautious when working on the bottom of a clarifier. When
hosing down, always hose a clean path to walk upon. Avoid
walking on the remaining sludge whenever possible.
Always turn off and lock out or turn off and tag the clarifier
breaker before working on the drive unit. If necessary, adjust-
ments may be made on flights or scrapers while the unit is in
operation; but keep in mind that, although these are moving
quite slowly, there is tremendous power behind their move-
ment. Stay clear of any situation where your body or the tools
you are using may get caught under one of the flights or scrap-
ers.
Guards should be installed over or around all gears, chains,
sprockets, belts, or other moving parts. Keep these in place
whenever the unit is in operation.
Railing should be installed along the tank side of all normal
walkways. If the unit is elevated above ground, railings should
be installed along the OUTSIDE of all walkways, also. Check
with your State Safety Office for requirements on railing in-
stallation.
14.223 Digesters and Digestion Equipment*
Digesters and their related equipment include many hazard-
ous areas and potential dangers.
NO SMOKING AND NO OPEN FLAMES should be allowed
in the vicinity of digesters, in digestion control buildings, or in
any other areas or structures used in the sludge digestion
system. This includes pipe galleries, compressor or heat ex-
changer rooms, and others. All these areas should be posted
with signs in a conspicuous place which forbid smoking and
open flames. METHANE GAS PRODUCED BY ANAEROBIC
CONDITIONS IS EXPLOSIVE WHEN MIXED WITH THE
PROPER PROPORTION OF AIR.
All enclosed rooms or galleries in this system should be well
ventilated with forced air ventilation. Never enter any enclosed
area or pit which is not ventilated. Always check for an oxygen
deficiency, explosive gases and hydrogen sulfide. DO NOT
depend upon your nose for hydrogen sulfide (H2S) detection in
these areas. A small amount of H2S in the air will make your
sense of smell immune to the odor in a short period of time.
Use an H2S detector.
When you are working in these areas, forced air ventilation
with a portable blower must be provided. Blower capacity in
cubic feet per minute should be greater than the digester vol-
ume in cubic feet divided by 20. Two blowers located at differ-
ent openings will do a better job than one large blower of the
same capacity as the total capacity of the two smaller ones.
Again, do not go into an area by yourself where H2S is present.
Have someone watch you.
Never enter a partially empty or completely empty digester
without first thoroughly ventilating the structure and then
checking for an explosive atmosphere and the presence of
hydrogen sulfide gas. Explosion-proof lights and NONSPARK-
INQ TOOLS5 and shoes must always bis used when working
around, on top of, or in a digester unless it has been com-
pletely cleaned and emptied, continuously ventilated by a
blower, and constant checks are made of the atmosphere in
the tank.
A  -SAPEHV PRACTlCe l-TO:
Nfrveg ALLOW	Qg OPEN
WrTHlN AM fcMfTV Pi^^TErlZ.

4 Also see "Safe Work Procedure No. 2, Entering and Working In Digesters," Jour. Water Poll. Control Fad., Vol. 42, No. 3, Part 1, p 466 (March
1070).
8 Nonaparklng tools are specially manufactured for use In areas where potentially explosive mixtures of gases may be present.

-------
220 Treatment Plants
Explosion blew off top of digester
tHWUfy
and landed on top of pickup truck
Fig. 14.4 Blown-up digester

-------
Be certain that guardrails are installed along the edges of the
digester roof or cover in areas where it is necessary to work
close to the edge. A fall from the top of a digester could be
fatal.
When working on equipment such as draft tube mixers,
compressors and diffusers, be certain that the unit which oper-
ates or supplies gas to these types of equipment is properly
locked out and appropriately tagged (Figs. 14.2 and 14.3).
If you have a heated digester, read and heed the manufac-
turer's instructions before working on the boiler or heat ex-
changer. Know that the gas valve is turned off before attempt-
ing to light the pilot. Be certain that the fire box has been
ventilated according to the manufacturer's instructions before
lighting the pilot.
When it becomes necessary to clean tubes or coils in a heat
exchanger, turn the unit supplying hot water off far enough in
advance to allow the heat exchanger to cool. Never open the
unit without double checking the water and sludge tempera-
tures. Be certain that they have cooled down to body tempera-
ture or lower.
Before working on any sludge pump, whether it is centrifugal
or positive displacement, be certain that the unit is turned off
and properly tagged (Figs. 14.2 and 14.3).
Positive displacement pumps should be equipped with an air
chamber and a pressure switch to shut the unit off at a pre-set
pressure. NEVER start a positive displacement pump against a
CLOSED DISCHARGE VALVE because pressure could build
up and burst a line or damage the pump. If you have closed
this valve in order to inspect or clean the pump, double check
to be sure that it is open before starting the unit.
Sludge pump rooms should be well ventilated to remove any
gases that might accumulate from leakage, spillage, or from a
normal pump cleaning. If you spill digesting sludge, clean it up
immediately to prevent the possible accumulation of gases or a
slippery walkway.
Provide thorough, regularly scheduled inspections and
maintenance of your gas collection system. Inspect drip traps
regularly. The so-called "automatic" drip trap is known to jam
open frequently, allowing gas to escape.
Good maintenance of flame arresters will ensure that they
will be able to perform their job of preventing a backflash of the
flame.
QUESTIONS
Write your answers in a notebook and then compare your
answers with those on page 234.
14.2L How can the danger of slipping be reduced on slippery
surfaces?
14.2M Why should no smoking or open flames be allowed in
the vicinity of digesters?
Safety 221
14.2N What safety precautions would you take before enter-
ing a recently emptied digester?
14.20 What would you do before relighting a waste gas
burner?
14.2P Why should you never start a positive displacement
pump against a closed discharge valve?
14.224 Trickling Filters
When it becomes necessary to inspect or service a rotating
distributor, stop the flow of wastewater to the unit and allow it to
come to rest. Tag the influent valve and tie down the distributor
arm so no one can start the distributor while you are working.
NeVBfc^TAMP ou WALk: ON THE P\tXtU
AA&PiA WHli-fc TH& GCTOcTiMGr Pl^TClBUTOR
\*y IN MOTION.
Provide an approved ladder or stairway for access to the
media surface. Be positive this is free from obstructions such
as hose bibs and valve stems.
Extreme caution should be used when walking on the filter
media. The biological slimes make the media very slippery.
Move cautiously and be certain of your footing.
NeveR ALLOW ANVONE TO Rl 17£- A
ROTATING Pl^rei&UTOE.
Although a rotating distributor moves fairly slowly, the force
behind it is powerful. If you fall off and are dragged by a dis-
tributor, you will be fortunate if you can walk away under your
own power.
When inspecting underdrains, remember that these are
dangerous confined spaces. Check to determine that the
channels or conduits are adequately ventilated. Gases are not
normally a problem here, but may be if there is a buildup of
solids which have become septic.
If it becomes necessary to jack up a distributor mechanism
for inspection or repair, always provide a firm base off the
media or drainage system for the jack plate. A firm base may
be provided by wooden planks which will spread the weight
over a large area. However, sometimes the only way to obtain
firm support is to remove the media and use the drainage
system as a firm base. Wooden planks should be placed over
the drainage system to distribute the weight better. Remember
you are lifting a heavy weight. Do not attempt inspection or
repair work until the distributor has been adequately and prop-
erly blocked in its raised position.
14.225 Aerators
Guardrails should be installed on the tank side of usual work
areas or walkways. If the tank is elevated above ground,
guardrails should also be installed on the ground side of the
tank. An operator should never go into unguarded areas alone.
When working on Y-walls, or other unguarded areas where
work is done infrequently, at least two people should do the
work. Approved life preservers with permanently attached
handlines should be accessible at strategic locations around
the aerator. You should wear a safety harness with a life line
when servicing aerator spray nozzles and other items around
an aerator.
An experiment in England found that if an operator fell into a
diffused aeration tank, the operator should be able to survive
because air will collect in the clothing and tend to help keep the
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222 Treatment Plants
operator afloat.6 Drownings apparently occur when a person is
overcome by the initial shock or there is nothing to grab hold of
to keep afloat or to pull oneself out of the aerator. In aerators
where diffused air is supplied only along the walls, strong cur-
rents are developed which will pull everyone but a very strong
swimmer under water. ALWAYS WEAR A LIFE PRESERVER
WHEN WORKING ON AN AERATOR.
When removing or installing diffusers, be aware of the limita-
tions of your working area. Inspect and properly position hoists
and other equipment used in servicing swing diffusers.
When it is necessary to work in an empty aerator, lower
yourself into the aerator with a truck hoist if one is available.
Ladders are awkward and dangerous; but if portable ladders
must be used, properly position them so that they will not slip
or twist. A good practice is to tie the top of the ladder so that it
cannot slip. Be extremely careful when using fixed ladders as
they become very slippery. The floor of the aerator also is likely
to be extremely slippery.
If your plant is in an area subject to freezing weather, be
aware of possible ice conditions around these units and use
caution accordingly.
14.226 Ponds
Ponds of any kind present basically the same hazards.
Therefore, the following safety measures will apply to ponds in
general.
If it is necessary to drive a vehicle on top of the pond levees,
maintain the roadway in good driving condition by surfacing it
with gravel or asphalt. Do not allow chuck holes or the forma-
tion of ruts. Be extremely cautious in wet weather. The material
used in the construction of most levees becomes very slippery
when wet. Slippery conditions should be corrected using
crushed rock or other suitable material.
Never go out on the pond for sampling or other purposes
when you are by yourself. Someone should be standing by on
the bank in case you get into trouble. Always wear an ap-
proved life jacket when working from a boat or raft on the
surface of the pond. And, as in any boating activity, DO NOT
STAND UP IN THE BOAT WHILE PERFORMING WORK.
QUESTIONS
Write your answers in a notebook and then compare your
answers with those on page 234.
14.2Q What precautions should you take when using a boat
to collect samples from a pond?
14.2R How would you stop the rotating distributor on a trick-
ling filter?
14.2S Why should you never work alone on the center "Y"
wall of an aerator?
14.227 Chlorine
Chlorine is usually purchased on a bid contract. Contracts
should specify the conditions under which chlorine containers
delivered to your plant will be accepted. The container should
be stamped with the last date when it was pressure tested. Do
not accept containers that have not been pressure tested
within five years of the delivery date. Cover cap should be
securely in place over the valve mechanism. All threaded con-
nections should be clean and not worn or cross threaded. New,
approved gaskets should be provided with each container. Do
not accept containers not meeting these standards. A few min-
utes spent inspecting containers when they are delivered can
prevent serious problems in the future.
CHUORINfc £rA^ RIGrttV IIZ12ITATIN6
AUV C0T2&0^\\J&
C?AN<3£(2	WlT-H CAUTlOM /
The most common causes of accidents involving chlorine
gas are leaking pipe connections and over-chlorinating.
Chlorine bottles or cylinders should be stored in a cool, dry
place, away from direct sunlight or from heating units. Some
heat is needed to cause desired evaporation and to control
moisture condensation on tanks. Chlorine bottles or cylinders
should never be dropped or allowed to strike each other with
any force. Cylinders should be stored in an upright position and
secured with a chain, wire rope, or clamp. They should be
moved only by hand truck and should be well secured during
moving. One-ton tanks should be blocked so that they cannot
roll. They should be lifted only by an approved lifting bar with
hooks over the ends of the containers. NEVER lift a bottle or
cylinder with an improvised sling.
Always wear a face shield when changing chlorine contain-
ers. Connections to cylinders and tanks should be made only
with approved clamp adaptors or unions. Always inspect all
surfaces and threads of the connector before making connec-
tion. If you are in doubt as to their condition, do not use the
connector. ALWAYS USE A NEW APPROVED TYPE GASKET
WHEN MAKING A CONNECTION. The reuse of gaskets very
often will result in a leak. Check for leaks as soon as the
connection is completed. Never wait until you smell chlorine. If
you discover even the slightest leak, correct it immediately, as
leaks tend to get worse rather than better. Like accidents,
chlorine leaks generally are caused by faulty procedure or
carelessness.
Obtain from your chlorine supplier and POST IN A CON-
SPICUOUS PLACE (OUTSIDE the chlorination room) the
name and telephone number of the nearest emergency service
in case of severe leak.
Cylinder storage and chlorinator rooms should be provided
with some means of ventilating the room. As chlorine is approx-
imately two and a half times heavier than air, vents or an
exhaust fan should be provided at floor level. Ideal installations
have a blower mounted on the roof to blow air into the room
and are vented at the floor level to allow escaped chlorine to be
blown out of the building.
Always enter enclosed cylinder storage or chlorinator rooms
with caution. If you smell chlorine when opening the door to the
area, immediately close the door, leave ventilation on, and
seek assistance.
Never attempt to enter an atmosphere of chlorine when you
are by yourself or without an approved air supply and protec-
tive clothing. Aid can usually be obtained from your local fire
department, which will normally have available a self-
contained breathing apparatus. This will allow a person to
enter safely into an atmosphere of chlorine.
6 Kershaw, M. A., "Buoyancy of Aeration Tank Liquid," Jour. Water Poll. Control Fed., Vol. 33, No. 11, p 1151 (Nov. 1961).

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Safety 223
Excellent booklets may be obtained from PPG Industries,
Inc., CHLORINE - SAFE HANDLING7 and from the Chlorine
Institute, CHLORINE MANUAL.8 Safety information on
chlorine handling is also contained in Chapter 10, "Disinfection
and Chlorination." Your local chlorine supplier will probably
provide you with all the information you need to handle and use
chlorine safely. It is your responsibility to obtain, read, and
understand safety information and to practice safety.
14.228	Apply Protective Coatings
CAUTION! When applying protective coatings in a clarifier or
any other tank or pit, whether enclosed or open topped, use
protective equipment to prevent skin burns from vapors from
asphaltic or bitumastic coatings. This may involve the use of
protective clothing as well as protective creams to be applied
to exposed skin areas. An air supply must be used when paint-
ing inside closed vessels or in an open, deep tank. Many paint
fumes are heavier than air; therefore, ventilation must be from
the bottom upward.
Check with your paint suppliers for any hazards involved in
using their products.
14.229	Housekeeping
Good housekeeping can and has prevented many acci-
dents.
Have a place for your tools and equipment. When they are
not being used, see that they are kept in their proper place.
Clean up all spills of oil, grease, chemicals, polymers,
wastewater and sludge. Keep walkways and work areas clean.
Provide proper containers for wastes, oily rags and papers.
Empty these frequently.
Remove snow and melt ice with salt in areas where a person
may slip and fall.
A clean plant will reduce the possibility of physical injuries
and infections.
QUESTIONS
Write your answers in a notebook and then compare your
answers with those on page 234.
14.2T How should one-ton chlorine tanks be lifted?
14.2U Why are chlorine vents placed at floor level?
14.2V What should you do if you open a door and smell
chlorine?
14.2W What factors are important in keeping a neat and safe
plant?
14.23 Industrial Waste Treatment
If your wastewater treatment plant treats strictly industrial
wastes or a mixture of both industrial and municipal wastes,
you must be aware of the industries and the types of wastes
that are discharged. Also, in spite of an effective sewer-use
ordinance, you must be alert for accidental spills and other
unanticipated discharges. These discharges can be toxic to
you, to the organisms in your treatment processes and corro-
sive to your equipment. From a safety viewpoint if you know
how to identify the types of wastes that may reach your plant,
you can be prepared to take the proper action and safety pre-
cautions. This section will discuss some of the hazardous or
toxic substances that could reach your treatment plant.
14.230 Fuels
Fuels may be dumped or drained into storm sewers con-
nected to sanitary sewers or they may enter the collection
system as a result of a leaking underground fuel line or tank.
Fuel oil and gasoline usually float on the surface of wastewater
and are not diluted by mixing. Therefore, most floating fuels
often collect in wet wells and can create both explosive and
toxic conditions or atmospheres.
To reduce the chances of an explosion in a wet well and
other downstream enclosed structures, an explosimeter
should be installed in wet wells to sound an alarm and teleme-
ter the situation to the main control panel BEFORE explosive
conditions are reached. Explosion-proof wiring will help to pre-
vent fires and explosions in hazardous areas such as wet
wells. Adequate ventilation also is essential. Oil skimmers
should be installed in wet wells to remove floating fuel oil and
gasoline. This equipment may be rarely used, but can remove
explosive fuels without exposing operators to hazardous condi-
tions.
Fuels may be detected by permanent or portable devices
which measure either hydrocarbons or the lower explosive limit
(L.E.L.). These devices must be installed in treatment plants
using pure oxygen treatment processes (activated sludge).
They are located in the collection system upstream from the
plant and in the headworks. If hydrocarbons or explosive con-
ditions are detected, the oxygen gas flow to the processes is
automatically shut off. The system is purged with air to prevent
a possible explosion. These detection devices must be prop-
erly located and maintained at frequent intervals to provide
reliable service.
14.231 Toxic Gases
Hydrogen sulfide (H2S) is the most common toxic gas en-
countered by operators because it is produced in collection
systems by decomposing sludge under anaerobic conditions.
Hydrogen sulfide and other toxic gases can be discharged into
sewers or produced by chemical and biological reactions in
sewers, in pretreatment facilities or at the wastewater treat-
ment plant's chlorination facilities. Other toxic gases include
phosgene ("war or mustard gas"), chlorine and tear-producing
substances (lacrimators).
Phosgene is produced in sewers when discharges of alcohol
saturated with phosgene-wasted chloroformates is back-
hydrolyzed (reverse chemical reaction) to phosgene. If an in-
dustry or laundry quickly dumps a few hundred to one
thousand gallons of bleach, a slug of chlorine can occur in the
plant's influent. Naphtha is used as both a fuel and a solvent
and can create hazardous conditions.
Hydrogen sulfide is usually produced by septic sludge in
collection systems. This is a continuing problem at treatment
plants. A serious hydrogen sulfide problem can develop when
a discharge of sodium sulfide (Na2S) from one industry mixes
with the discharge of an acid waste from another industry. This
mixture can produce extremely hazardous concentrations of
hydrogen sulfide which is not only toxic, but explosive, flam-
mable and very odorous.
7	PPG Industries, Inc., Chemical Division, One Gateway Center, Pittsburgh, Pennsylvania 15222.
8	Chlorine Institute, Inc., 342 Madison Avenue, New York, New York, 10017. Price $3.00.

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224 Treatment Plants
Tear-gas type substances (lacrimators) occasionally may
reach treatment plants. Certain organic insecticide wastes,
when only partially chlorinated at an industrial wastewater pre-
treatment plant, can form tear-gas type substances.
Toxic gases may be detected by probes which measure the
concentration of a particular gas such as hydrogen sulfide,
chlorine or sulfur dioxide. Some instruments are capable of
detecting the lower explosive limit (L.E.L.), an oxygen defi-
ciency and hydrogen sulfide. Sensors and monitors for toxic
gases usually require daily calibration and regular mainte-
nance.
14.232	Amines
Amines are compounds formed from ammonia. Some of
these compounds may react with other substances in waste-
water which could form nitrosoamines, some of which are con-
sidered carcinogens (capable of causing cancer in humans). A
remote possibility exists that nitrosoamines from industrial
dumps or chemical-biological reactions in sewers could con-
taminate the air space around treatment plants. If this problem
is discovered at a treatment plant, all treatment process struc-
tures (wet wells, clarifiers, aeration tanks) would have to be
covered. Exhaust air from these sources would have to be
treated to remove harmful contaminates and offensive odors.
Operators must test the atmosphere for harmful contaminates
before entering the area. The testing equipment will depend on
the contaminants that are expected to be present.
14.233	Surface-active Agents
Concentrated industrial surface-active agents, either acci-
dentally spilled or dumped into a collection system can upset
wastewater treatment processes. Certain industrial wastes can
serve as super floe agents which produce a much denser
sludge than usually pumped. This sludge can be too thick to
pump, which then requires special handling to reslurry the
sludge so it can be pumped. The opposite can occur when
antifloc agents lower the capture of suspended solids in pri-
mary clarifiers. Excessive solids can reach aeration tanks and
even flow out in the plant effluent. Rejected batches of deter-
gents can contain antifloc agents.
Foaming agents often cause treatment plant operators very
serious problems. Foam in wet wells can prevent inspection
and operation of screens and grinders. Foam on aeration tanks
that flows into neighbors' yards and on the surface of receiving
water is objectionable to the public. If foam is formed in a
chlorination chamber by a hydraulic jump, the foam bubbles
could contain chlorine gas. Detection devices are available
which are capable of detecting excessive levels of foaming
agents. These foam detection devices also can be pro-
grammed to automatically feed an antifoaming agent to keep
foaming under control.
14.234	Biocldes
Poisons or biocides from industries can be harmful to
operators as well as toxic to organisms purifying the wastewa-
ter in treatment processes. Unfortunately, biocides frequently
cannot be detected until after the organisms in the treatment
processes have been killed. Not only can the activated sludge
process and the digesters be put out of action, but the sludge
can be so contaminated that it cannot be disposed of on land
or in landfills.
14.235	High or Low pH
Highly acid or alkaline wastes can be very hazardous. They
are dangerous to personnel, treatment processes, and equip-
ment. pH probes installed in the headworks can detect abnor-
mal pH levels. A low pH caused by an acid can be increased by
the addition of sodium hydroxide (NaOH). Sulfuric acid
(H2S04) can be added at the headworks to lower the pH of an
alkaline waste.
14.236	Summary
Your main concern as an operator is your own personal
survival and that of your coworkers, and the preservation of
your plant and the organisms in the treatment processes. In-
dustrial dumps can produce especially serious hazards. Effec-
tive sewer-use ordinances and industrial pretreatment facilities
can help greatly to reduce the frequency and severity of indus-
trial dumps. This section only covers a few of the many poten-
tial hazards that can be created by industrial wastes. Most of
the hazards discussed in this section were described in a pa-
per, "Municipal Wastewater Treatment and Toxic Sub-
stances," written by Gerald H. Slattery, Plant Manager,
Patapsco Wastewater Treatment Plant, Baltimore, Maryland.
The paper was printed in the November, 1977, issue of "Deeds
& Data,'1 published by the Water Pollution Control Federation.
QUESTIONS
Write your answers in a notebook and then compare your
answers with those on page 235.
14.2X List the major types of discharges from industrial
plants that could create safety hazards.
14.2Y What would you do if a gasoline truck was in an acci-
dent and the fire department washed the spilled
gasoline into a storm drain? The storm drain conveys
wastewater to the wet well in the headworks of your
treatment plant.
14.2Z What kinds of problems can be caused by surface-
active agents?
END OF LESSON 2 OF 3 LESSONS
on
PLANT SAFETY AND GOOD HOUSEKEEPING
Please answer the discussion and review questions before
continuing with Lesson 3.

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Safety 225
DISCUSSION AND REVIEW QUESTIONS
Chapter 14. PLANT SAFETY AND GOOD HOUSEKEEPING
(Lesson 2 of 3 Lessons)
Write the answers to these questions in your notebook. The
problem numbering continues from Lesson 1.
10.	When cleaning racks or screens, on what kind of surface
should the operator stand?
11.	Never lean against a removable safety chain. True or
False?
12.	Why should only qualified electricians work on an electri-
cal control panel?
13.	Why should effluent weirs and launders on clarifiers be
brushed or cleaned?
14.	Why should no smoking or open flames be allowed in the
vicinity of the digester or sludge digestion system?
15.	Why are discharges of amines into collection systems
considered dangerous?
16.	Why should you never go out on a pond for sampling or
other purposes by yourself?
17.	Where should the name and telephone number of the
nearest emergency chlorine leak repair service be
posted?
18.	What safety precautions should be taken when applying
protective coatings?
CHAPTER 14. PLANT SAFETY AND GOOD HOUSEKEEPING
(Lesson 3 of 3 Lessons)
14.3 SAFETY IN THE LABORATORY9
In addition to all safety practices and procedures mentioned
in the previous sections of this chapter, the collecting of sam-
ples and the performance of laboratory tests require that you
be aware of the specific hazards involved in this type of work.
Laboratories use many hazardous chemicals. These chemi-
cals should be kept in limited amounts and used with respect.
Your chemical supplier may be able to supply you with a safety
manual.
14.30 Sampling Techniques
Whenever possible, rubber gloves should be worn when
your hands may come in direct contact with wastewater or
sludge. When you have finished sampling, always wash the
gloves thoroughly before removing them. After removing the
gloves, wash your hands thoroughly, using a disinfectant-type
soap.
NEVfcC COU-fcCT ANY -S-ANVPi-E^ VMITH
YOUR	VOU WAVC. AMV
4KIN AEG:A^	A^Oir^
OC ^02AT<1B&9..
Do not climb over or go beyond guardrails or chains when
collecting samples. Use sample poles, ropes and other de-
vices as necessary to collect samples.
14.31 Equipment Use and Testing Procedures
The following are some basic procedures to keep in mind
when working in the laboratory.
U0J&3. LOOU INTO -THE: OP&N &NP OZ-
A Container purine a REActioNi or
H&ATI NTVSEr £OMTAl Sit|Z.
1.	Use proper safety goggles or face shield in all tests where
there is danger to the eyes.
2.	Use care in making rubber-to-glass connections. Lengths
of glass tubing should be supported while they are being
inserted into rubber. The ends of the glass should be
FLAME POLISHED10 to smooth them out, and a lubricant
such as water should be used. Never use grease or oil.
Gloves or some other form of protection for the hands
should be used when making such connections. The tub-
ing should be held as close to the end being inserted as
possible to prevent bending or breaking. Never try to force
rubber tubing or stoppers from glassware. Cut the rubber
as necessary to remove it.
3.	Always check labels on bottles to make sure that the
proper chemical is selected. Never permit unlabeled or
undated containers to accumulate around or in the labora-
tory. Keep storage areas well organized to prevent mis-
takes when selecting chemicals for use. Clean out old or
excess chemicals. Separate flammable, explosive, or
special hazard items for storage in an approved manner.
See Section 14.9, "Additional Reading," Reference 10.
allcubm\cal containers
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9	Also see FISHER SAFETY MANUAL, Fisher Scientific Company, 711 Forbes Avenue, Pittsburg, PA 15219. Price $6.00.
10	Flame Polished. Melted by a flame to smooth out Irregularities. Sharp or broken edges of glass (such as the end of a glass tube) are
rotated In a flame until the edge melts slightly and becomes smooth.

-------
226 Treatment Plants
4.	Never handle chemicals with your bare hands. Use a
spoon or spatula for this purpose.
5.	Be sure that your laboratory is adequately ventilated.
Even mild concentrations of fumes or gases can be
dangerous.
6.	Never use laboratory glassware for a coffee cup or food
dish. This is particularly dangerous when dealing with
wastewaters.
7.	When handling hot equipment of any kind, always use
tongs, asbestos gloves, or other suitable tools. Burns can
be painful and can cause more problems (encourage
spills, fire, and shock).
8.	When working in the lab, avoid smoking and eating except
at prescribed coffee breaks or at the lunch period.
M-WW6 THOEOU&HLV WVOUPZ.
4AAOKIM6 ot? &ATIN<5r.
9. Do not pipet chemicals or wastewater samples by mouth.
Always use a suction bulb or an automatic burette.
10.	Handle all chemicals and reagents with care. Read and
become familiar with all precautions or warnings on labels.
Know and have available the antidote for all poisonous
chemicals in your lab.
11.	A short section of rubber tube on each water outlet is an
excellent water flusher to wash away harmful chemicals
from the eyes and skin. It is easy to reach and can quickly
be directed on the exposed area. Eyes and skin can be
saved if dangerous materials are washed away quickly.
12. Dispose of all broken or cracked glassware immediately.
Chipped glassware may still be used if it is possible to fire
polish the chip in order to eliminate the sharp edges. This
may be done by slowly heating the chipped area until it
reaches a temperature at which the glass will begin to
melt. At this point remove from flame and allow to cool.
N&V&E WOLV ASW PI £C& Of-
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Always use a suitable glove or tool.
13.
ee-M&MgglZ -TO APD ACID -To WAT&T2,
BUT N£V£G THE-	.
14.	Wear a protective smock or apron when working in the lab.
This may save you the cost of replacing your work clothes
or uniform. Protective eye shields should be worn too.
15.	Electrical equipment should be properly grounded and
safeguards provided to prevent insertion of improper plugs
into the equipment.
16.	Don't keep your lunch in a refrigerator that is used for
samples or chemical storage.
QUESTIONS
Write your answers in a notebook and then compare your
answers with those on page 235.
14.3A What safety precautions would you take when collect-
ing laboratory samples from a plant influent?
14.3B Why should you always wash your hands before eat-
ing?
14.3C Why should chemicals and reagents be handled with
care?
14.4 FIRE PREVENTION
Fires are a serious threat to the health and safety of the
operator and to the buildings and equipment in a treatment
plant. Fires may injure or cause the death of an operator.
Equipment damaged by fire may no longer function properly,
and your treatment plant may have difficulty adequately treat-
ing the influent wastewater.
Good safety practices with respect to fire prevention require
a knowledge of:
1.	Ingredients necessary for a fire
2.	Fire control methods
3.	Fire prevention practices
14.40 Ingredients Necessary for a Fire
The three essential ingredients of all ordinary fires are:
1.	FUEL — paper, wood, oil, solvents, and gas.
2.	HEAT — the degree necessary to vaporize fuel according
to its nature.
3.	OXYGEN — normally at least 15 percent of oxygen in the
air is necessary to sustain a fire. The greater the concentra-
tion, the brighter the blaze and more rapid the combustion.
ALWAV4 WOUK IN A fiJME \\OOV If iVOKklNd
W\TR £H£MICAL-^ OU.	HAVING-
TOX\C-

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Safety 227
14.41	Fire Control Methods
To extinguish a fire, it is necessary to remove only one of the
essentials by:
1.	Cooling (temperature and heat control)
2.	Smothering (oxygen control)
3.	Isolation (fuel control)
Fires are classed as A-, B-, C-, or D-type fires, according to
what is burning.
Class A fires (general combustibles such as wood, cloth,
paper, or rubbish) are usually controlled by cooling — as by
use of water to cool the material.
Class B fires (flammable liquids such as gasoline, oil,
grease, or paint) are usually smothered by oxygen control —
as by use of foam, carbon dioxide, or a dry chemical.
Class C fires (electrical equipment) are usually smothered
by oxygen control — use of carbon dioxide or dry-chemical
extinguishers — nonconductors of electricity.
Class D fires occur in combustible metals, such as mag-
nesium, lithium, or sodium, and require special extinguishers
and techniques.
Use carbon dioxide compressed gas extinguishers to control
fires around electrical contacts. Do not use soda-acid type
extinguishers because the electrical motor will have to be re-
wound and you could be electrocuted attempting to put out the
fire.
Know where fire extinguishers and hoses are kept and know
where yard hydrants are located, what each is for, and how to
use them.
14.42	Fire Prevention Practices
You can prevent fires by:
1.	Maintaining a neat and clean work area, preventing ac-
cumulation of rubbish.
2.	Putting oil- and paint-soaked rags in covered metal con-
tainers.
3.	Observing all "no smoking" signs.
4.	Keeping fire doors, exits, stairs, fire lanes, and firefighting
equipment clear of obstructions.
5.	Keeping all burnable materials away from furnaces or other
sources of ignition.
6.	Reporting any fire hazards you see that are beyond your
control, especially electrical hazards which are the source
of many fires.
Finally, here again are the things to remember:
1.	Prevent fire by good housekeeping and proper handling of
flammables.
2.	Make sure that everyone obeys "no smoking" signs in all
areas near explosive or flammable gases.
3.	In case of fire, turn in the alarm immediately and make sure
that the fire department is properly directed to the place of
the fire.
4.	Action during the first few seconds of ignition generally
means the difference between destruction and control. Use
the available portable fire-fighting equipment to control the
fire until help arrives.
5.	Use the proper extinguisher for that fire.
6.	Learn how to operate the extinguishers.
If it is necessary to get out of the building, do not stop to get
anything — just get out!
Can you prevent fires? You can if you try, so let's see what
we can do to preserve our well-being and the water pollution
control system.
If you guard against fires, you will be protecting your lives
and your community.
14.43 Acknowledgment
Material in this section on Fire Prevention appeared in the
July 1970 issue of the Journal of the Water Pollution Control
Federation, on pages 1426 and 1427, as a Wastewater Wis-
dom talk. Originally, the information appeared as a National
Safety Council "5 Minute Safety Talk," published in the IN-
DUSTRIAL SUPERVISOR.
QUESTIONS
Write your answers in a notebook and then compare your
answers with those on page 235.
14.4A What are the necessary ingredients of a fire?
14.4B How should oil- and paint-soaked rags be handled?
14.5 WATER SUPPLIES
Inspect your plant to see if there are any cross-connections
between your potable (drinking) water and items such as water
seals on pumps, feed water to boilers, hose bibs below grade
where they may be subject to flooding with wastewater or
sludges, or any other location where wastewater could con-
taminate a domestic water supply.
If any of these or other existing or potential cross-
connections are found, be certain that your drinking water sup-
ply source is properly protected by the installation of an ap-
proved back-flow prevention device. Many treatment plants
use an AIR-GAP DEVICE11 (Figure 14.5) to protect their drink-
ing water supply.
It is a good practice to have your drinking water tested at
least monthly for coliform group organisms. Sometimes the
best of back-flow prevention devices do fail.
Never drink from outside water connections such as sill
cocks and hoses. The hose you drink from may have been
used to carry effluent or sludge.
You may find in your plant that it will be more economical to
use bottled drinking water. If so, be sure to tack up conspicu-
ous signs that your water is not drinkable. This also applies to
all hose bibs in the plant from which you may obtain water
other than a potable source. This is a must in order to inform
visitors or absent-minded or thirsty employees that the water
from each marked location is not for drinking purposes.
11 Air-gap Device. An open vertical drop, or vertical empty space, between a drinking (potable) water supply and the point of use in a
wastewater treatment plant. This gap prevents back slphonage because there is no way wastewater can reach the drinking water supply.

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AIR GAP	g
AN OPEN VERTICAL DROP, OR VERTICAL EMPTY SPACE,	£
BETWEEN A DRINKING (POTABLE) WATER SUPPLY AND	g
THE POINT OF USE IN A WASTEWATER TREATMENT	3
PLANT. THIS GAP PREVENTS BACK SIPHONAGE BE-	Z
CAUSE THERE IS NO WAY WASTEWATER CAN REACH	»
THE DRINKING WATER SUPPLY.	=
w
PRESSURE TANK
OPEN
TANK

DRINKING
WATER
SUPPLY

TO
TREATMENT
^PLANT
(NON DRINKING
USES)

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Safety 229
QUESTION
Write your answer in a notebook and then compare your
answer with the one on page 235.
14.5A Why do some wastewater treatment plants use bottled
water for drinking purposes?
14.6	SAFETY EQUIPMENT AND INFORMATION
Post conspicuously on your bulletin board the location and
types of safety equipment available at your plant (such as first
aid kit, breathing apparatus and explosiometers). Vou, as the
plant operator, should be thoroughly familiar with the operation
and maintenance of each piece of equipment. You should re-
view these at fixed intervals to be certain that you can safely
use the piece of equipment as well as to be sure that it is in
good operating condition.
Contacts should be made with your local fire and police
departments to acquaint them with hazards at your plant as
well as to inform them of the safety equipment that is neces-
sary to cope with problems that may arise. Arrange a joint
training session with these people in the use of safety equip-
ment and the handling of emergencies. They also should know
access routes to and around the treatment plant.
If you have any specific problems of a safety nature, do not
hesitate to contact officials in your state safety agency. They
can be of great assistance to you. And do not forget your
equipment manufacturers; their familiarity with your equipment
will be of great value to you.
Also posted in conspicuous places in your plant should be
such information as the phone numbers of your fire and police
departments, ambulance service, chlorine supplier or repair-
man, and the nearest doctor who has agreed to be available on
call. Having these immediately available at telephone sites
may save your or a fellow worker's life. Check and make sure
these numbers are listed at your plant. If they are not listed,
ADD THEM NOW.
Prepare an emergency medical information sheet for each
operator. Keep all of these sheets together in one binder. Send
the binder with the ambulance that takes an injured operator to
the hospital.
QUESTION
Write your answer in a notebook and then compare your
answer with the one on page 235.
14.6A What emergency phone numbers should be listed in a
conspicuous place in your plant?
14.7	"TAILGATE" SAFETY MEETINGS12
Safety is crucial. Accidents cost money. No one can afford to
lose time from their job due to injury. Safety meetings provide
the opportunity to explain and discuss safe procedures and
safe conditions.
In some states, by law, you may be required to conduct
safety meetings at fixed intervals with employees. Whether this
is required or not, it certainly is a good practice. Invite police
and fire personnel to participate from time to time so you get to
know them and they become acquainted with you and your
facilities. Once every 7 to 10 days is a good frequency. These
meetings should usually be confined to one topic, and should
be no longer than 10 to 20 minutes. It will be worthwhile to
review monthly any accidents during the past month at one of
the meetings. Do not use this meeting to fix blame. Try to dig
into the cause and to determine what can be or has been done
to prevent a similar accident in the future.
To help you conduct "tailgate" safety meetings, this chapter
was arranged to discuss the safety aspects of different plant
operations. The material in some sections was deliberately
repeated to cover the topic and to remind you of dangers.
Some plants select topics for their "tailgate" safety meetings
from a "safety goof box." The box is placed in a convenient
location. Whenever anyone sees an unsafe situation or sees
someone perform a hazardous act without proper safety pre-
cautions, this person places a note in the box identifying the
situation or person and the act. The box is opened at each
safety meeting, and the cause of the "goof" and the steps that
can be taken to correct and prevent it from happening again
are discussed.
Your state safety agency, your insurance company, equip-
ment and material suppliers, and the Water Pollution Control
Federation are all excellent sources of literature and aids that
may help you in conducting "tailgate" safety meetings. Some
of these agencies may be able to supply you with posters,
signs, and slogans that are very effective safety reminders.13
You may wish to dream up some reminders of your own.
QUESTIONS
Write your answers in a notebook and then compare your
answers with those on page 235.
14.7A What is the purpose of "tailgate" safety meetings?
14.7B How frequently should safety meetings be held for
treatment plant operators?
14.8 HOW TO DEVELOP SAFETY TRAINING PROGRAMS
14.80 Conditions for an Effective Safety Program
Effective safety programs rely on many techniques to help
workers recognize hazards and learn safe procedures. These
safety programs can include highly organized meetings to tail-
gate safety sessions to informal get togethers or bull sessions.
Safety programs of all types have proven very effective when
the following conditions are met:
12"Tailgate." The term "tailgate" comes from safety meetings regularly held by the construction industry around the tailgate of a truck.
13 Chemical Laboratory Safety Posters have been prepared by the Manufacturing Chemists Association, 1825 Connecticut Avenue, N.W.,
Washington, D C. 20009. Price $3.50 per set of 12 posters.

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230 Treatment Plants
1.	Basic safety concepts and practices are thoroughly un-
derstood by all.
2.	EVERYONE PARTICIPATES and accepts personal re-
sponsibility for their own safety and that of their fellow
workers (participation at all levels is absolutely essential to
the continued success of any safety program).
3.	Adequate safety equipment is available and its capabilities
thoroughly understood. Crews must regularly review and
drill in the actual use of the equipment under emergency
and hazardous conditions.
4.	Everyone realizes that safety is a continuing learning and
re-learning process — a way of life that must become part
of your regular habits.
5.	ACCIDENTS are studied step by step and thoroughly re-
viewed with the attitude that "they are caused and don't
just happen." Every reasonable step will be taken to re-
duce the chance of an accident happening again to as
near zero as is practical.
6.	Every detail of work is a subject for discussion to the ex-
tent it will improve safety.
7.	Workers realize they should stop anyone performing an
unsafe act and remind the person that they are not follow-
ing safe procedures, why, and how the job can be done
safely.
8.	Ability. Before starting a job, assure yourself you can do
the job without injury. If you are assigned work you are not
qualified to perform, call this problem to the attention of
your supervisor.
9.	Understanding. Before starting a job, thoroughly under-
stand the work to be done, your job and the safety rules
that apply. Tailgate safety sessions or pre-job discussions
will help promote safe operations.
10. Management actively supports the safety training program
and demands that safe equipment and procedures be
used at all times.
14.81	Start at the Top
An effective safety training program must start at the top.
The Chief Executive, who controls the purse strings and
makes final decisions, must not only support safety but must
promote it from the start and continuously promote safety on a
day-to-day basis. The safety director must have a top man-
agement position or have direct access to the Chief Executive.
Without this type of organization, a safety program may be put
off, watered down or even eliminated in the name of urgency,
time and cost.
14.82	Plan for Emergencies
Start where you are. Nothing is going to stop while you get
your safety program organized. Emergencies, accidents and
injuries can happen at any time and usually at the wrong time.
Try to minimize the impact of accidents while trying to develop
or improve your plan for prevention. The first step is to prepare
emergency procedures for your treatment plants, collection
systems and vehicles. These plans should include;
1.	What to do and what not to do for the injured,
2.	How to contact the nearest fire department, rescue squad
or ambulance,
3.	Identification of the injured and notification of relatives,
4.	Direction for rescue vehicles to reach the scene and to
locate the victim,
5.	Prevention of further damage to people and property, and
6.	Names of persons and authorities to be notified after the
emergency.
All employees must be interested in these procedures and
copies should be posted in prominent places in all plant areas,
pumping stations, and vehicles. The fact that employees are
preparing for emergencies will have a positive effect in reduc-
ing accidents.
14.83	Promote Safety
Start early with your promotion of safety. Make safety a part
of discussions and work procedures. Follow safe practices
yourself — this applies especially to supervisory personnel.
Example is a powerful incentive.
14.84	Hold Safety Drills and Training Courses
Remember those fire drills in school? Try drilling on how
employees should respond during emergencies, including
evacuation of facilities. All facilities should have the necessary
fire extinguishers, gas masks and self-contained breathing ap-
paratus. Do not wait for an emergency before trying to learn
how to use this equipment. Get proper instructions and con-
duct practice sessions.
First aid and chlorine safety are important steps in organ-
izing others to assist in your safety program. You can use the
Red Cross multi-media program to train first aid teams and
instructors. Chlorine manufacturers or distributors provide ex-
cellent instruction in chlorine hazards and safety precautions.
When developing your training courses, try to emphasize the
most hazardous tasks where accidents are likely to happen.
Studies have shown that injuries most often occur when doing
activities that are not routine. In your course discussions try to
identify how hazards can cause injuries, how bad the injuries
can be, and ways to avoid injury.
14.85	Purchase the Obvious Safety Equipment First
Hard hats, safety shoes, and eye protection apply to all per-
sonnel in designated areas and/or specific jobs. Purchase this
equipment and post the areas where it must be used. The
purchase of more specific and expensive equipment such as
gas analyzers, explosion meters, and audio meters, are more
critical and costly. The need and time to purchase them will be
obvious as your safety program progresses.
14.86	Safety Is Important for Everyone
As your safety program develops, you will realize that safety
is the responsibility of everyone, from supervisors to workers.
Everyone must be involved. Organize safety committees and
meetings from top to bottom, as well as from bottom to top. If
we do it well, then safety practices will progress from top to
bottom. Ideas and suggestions will come if they are recognized
and implemented.
14.87	Necessary Paper Work
When you start to develop your safety program, concentrate
your efforts on programs that apply generally to all employees.
Paper work can be helpful to identify the causes of accidents
and to develop corrective procedures.
1.	Accident report forms (Figure 14.6). Use these forms to
analyze the causes of accidents and to prevent future acci-
dents.
2.	Safety policy. The Chief Executive must establish a safety
policy and repeatedly state support of the policy.

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Safety 231
3.	Safety rules. Safety rules are as important as work rules
and they should be implemented and enforced in the same
manner. Most people perform better and with more confi-
dence if they know the rules of the game. These rules must
apply to everyone. Supervisors should serve as examples
to the workers.
4.	Supervisor's guides. Supervisors must have guidelines on
how to promote and implement a safety program and en-
force the rules.
5.	Review of plans and specifications and also plant inspec-
tions. State and OSHA Regulations must be used when
reviewing plans and specifications. Checklists are a tre-
mendous aid during plant inspections.
14.88	Train for Safety
Training is essential. Use every opportunity to give safety
instruction from ten-minute on-the-spot chats to supervisory
safety meetings. Vary the techniques and timing with chats,
meetings, drills, exercises, workshops and seminars. Cover all
the subjects. Matching discussions to incidents such as slips
and falls during the slippery season, defensive driving if a bad
accident has occurred in the area, and chlorine safety if there
have been problems with leaks. Get your subject material out
while you have their attention.
14.89	Safety Summary
All types of safety programs are helpful. If variety is the spice
of life, let variety add spice to your safety program. Informal
chats on safety do not replace formal safety meetings or vice
versa. Every type of safety meeting can help you develop a
very effective safety program.
Your safety program should include the following items:
1.	Get your top official to support and promote safety,
2.	Give your safety officer direct access to the Chief Execu-
tive,
3.	Direct your program general topics to the more specific,
4.	Organize from top to bottom,
5.	Establish rules and implement and enforce them,
6.	Train at all levels from employment to retirement, and
7.	MAKE SAFETY A HABIT.
This section was prepared from material in:
1.	"A Practical Approach to a Safety Program," by Richard R.
Metcalf, Deeds & Data, Water Pollution Control Federation,
Washington, D.C., July, 1977, and
2.	"Safety for the Collection System Worker," by Glenn Davis
in OPERATION AND MAINTENANCE OF WASTEWATER
COLLECTION SYSTEMS for the U.S. Environmental Pro-
tection Agency by California State University, Sacramento,
Sacramento, California, 1976.
QUESTIONS
Write your answers in a notebook and then compare your
answers with those on page 235.
14.8A List three types of safety meetings.
14.8B What is the role of management in a safety training
program?
14.8C Why should safety drills be held regularly?
14.8D What types of paper work are necessary for an effec-
tive safety training program?
CITY OF	WASTEWATER TREATMENT
PLANT ACCIDENT REPORT
Date of this report	Name of person injured 			
a.m.
Date of injury ..	Time _	p.m. Occupation	
Home address 	 Age	Sex
Check	First aid case, or 	disabling (lost time) injury
	Employee or staff injury,	on duty, or	off duty
	Visitor injury
Date last worked 		Date returned to work 	
Person reporting 		
DESCRIPTION OF ACCIDENT
1.	Description of Accident	 	
(Describe in detail what happened) (Name machine, tool,
appliance, 				 	 —
gas or liquid involved — if machine or vehicle — name part,
gears, pulley, etc.)
2.	Accident occurred where?			—
If vehicle accident,
make simple sketch of
scene of accident.
3.	Describe nature of injury and part of body affected 	
(Amputation of finger, laceration of leg, back strain, etc.)
4. Were other persons involved? 	
(If yes, give names and addresses.)
5. Names and addresses of witnesses
6. If property damage involved, give brief description
7.	If hospitalized, name of hospital
8.	Name and address of physician
9.	Treatment given for injuries 	
Fig. 14.6 Typical accident report form
14.9 SUMMARY
Following is a summary of the safety precautions that have
been discussed in the previous sections.
1.	Good design without proper safety precautions will not
prevent accidents. ALL PERSONNEL MUST BE IN-
VOLVED IN A SAFETY PROGRAM AND PROVIDED
WITH FREQUENT SAFETY REMINDERS.
2.	Never attempt to do a job unless you have sufficient help,
adequate skills, the proper tools, and necessary safety
equipment.
3.	Never use fingers to remove a manhole cover or heavy
grate. Use the proper tool.

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232 Treatment Plants
4.	"Lift with your legs, not your back" to prevent back strains.
5.	Use ladders of any kind with caution. Be certain that por-
table ladders are positioned so they will not slip or twist.
Whenever possible, tie the top of a ladder used to enter
below-grade structures. Do not use metal ladders near
electrical boards or appliances.
6.	Never enter a manhole, pit, sump, or below-grade en-
closed area when by yourself and without adequate venti-
lation.
7.	Always test manholes, pits, sumps, and below-grade en-
closed areas for explosive atmosphere, oxygen defi-
ciency, and hydrogen sulfide. Before entering, thoroughly
ventilate with forced air blower.
8.	Wear or use safety devices such as safety harnesses, gas
detectors, and rubber gloves to prevent infections and in-
juries.
9.	Never use a tool or piece of equipment unless you are
thoroughly familiar with its use or operation and know its
limitations.
10.	When working in traffic areas, always provide:
a.	Adequate advance warning to traffic by signs and
flags.
b.	Traffic cones, barricades, or other approved items for
channeling the flow of traffic around your work area.
c.	Protection to workers by placing your vehicle between
traffic and job area, and/or by use of flashing or revolv-
ing lights, or other devices.
d.	Flagmen when necessary to direct and control flow of
traffic.
11.	Before starting a job, be certain that work area is of
adequate size. If not, make allowances for this. Keep all
working surfaces free of material that may cause surface
to be slippery.
12.	See to it that all guardrails and chains are properly in-
stalled and maintained.
13.	Provide and maintain guards on all chains, sprockets,
gears, shafts, and other similar moving pieces of equip-
ment that are normally accessible.
14.	Before working on mechanical or electrical equipment,
properly turn off and/or tag breakers to prevent the acci-
dental starting of the equipment while you are working on
it. Wear rubber gloves and boots wherever you may con-
tact "live" electrical circuits.
15.	Never enter a launder, channel, conduit, or other slippery
area when by yourself.
16.	Do not allow smoking or open flames in the area of, on top
of, or in any structure in your digestion system. Post all
these areas with warning signs in conspicuous places.
17.	Never enter a chlorine atmosphere by yourself or without
proper protective equipment. Seek the cooperation of your
local fire department in supplying self-contained breathing
apparatus.
18.	Obtain and post in a conspicuous location the name and
telephone number of the nearest chlorine emergency serv-
ice. Acquaint your police and fire department with this
service.
19.	Inspect all chlorine connectors and lines before using.
Discard any of these that appear defective.
20.	Keep all chlorine containers secured to prevent falling or
rolling. Use only approved methods of moving and lifting
containers.
21.	Maintain a good housekeeping program. This is a proven
method of preventing many accidents.
22.	Conduct an effective safety awareness and training pro-
gram.
These are the highlights of what has been previously dis-
cussed. Whenever in doubt about the safety of any piece of
equipment, structure, operation, or procedure, contact the
equipment manufacturer, your city or county safety officer, or
your state safety office. One of these should be able to supply
you with an answer to your questions.
ACCIPenTS PONT JUSTMAPPgN...
•mcv Atre CAusfrp/
You can be held personally liable for injuries or damages
caused by an accident as a result of your negligence.
Can you afford the price of one?
Can you afford the loss of one or more operators?
Can your family afford to lose YOU?
14.10 ADDITIONAL READING
1.	MOP 11, pages 156-163 or 479-496.*
2.	NEW YORK MANUAL, pages 169-182.
3.	TEXAS MANUAL, pages 689-706.
4.	CHLORINE - SAFE HANDUNG, PPG Industries, Inc.,
Chemical Division, One Gateway Center, Pittsburgh,
Pennsylvania 15222.
5.	SAFETY IN WASTEWATER WORKS, WPCF Manual o1
Practice No. 1, Water Pollution Control Federation, 2626
Pennsylvania Avenue, N.W., Washington, D.C. 20037.
Price: $1.00 to members, $2.00 to others. Indicate your
member association when ordering.
6.	SAFETY PROGRAM PROMOTIONAL PACKET, Water
Pollution Control Federation, 2626 Pennsylvania Avenue,
N.W., Washington, D.C. 20037. Price $3.00 to members,
$6.00 to others.
7.	CHLORINE MANUAL, The Chlorine Institute, Inc., 342
Madison Avenue, New York, New York 10017. Price
$3.00.
8.	MOTIVATING FOR SAFETY, Journal of American Water
Works Association, Vol. 61, No. 2, pp 57-59 (February
1969).
* Depends on edition.

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Safety 233
9. CRC HANDBOOK OF LABORATORY SAFETY, by Nor-
man V. Steere, Chemical Rubber Publishing Company,
18901 Cranwood Parkway, Cleveland, Ohio 44128. Price
$24.50.
10. GENERAL INDUSTRY, OSHA SAFETY AND HEALTH
STANDARDS (29 CFR 1910), OSHA 2206, revised Janu-
ary 1976. Obtain from Superintendent of Documents, U.S.
Government Printing Office, Washington, D.C. 20402.
Stock number 029-015-0054-6. Price $6.50.
11.	FISHER SAFETY MANUAL, Fisher Scientific Company,
711 Forbes Avenue, Pittsburgh, Pennsylvania 15219.
Price $6.00.
12.	Journal Water Pollution Control Federation, Annual Year-
book, Part Two of March Issue, contains listings of publi-
cations, films and slides.
END OF LESSON 3 OF 3 LESSONS
on
PLANT SAFETY AND GOOD HOUSEKEEPING
DISCUSSION AND REVIEW QUESTIONS
Chapter 14. PLANT SAFETY AND GOOD HOUSEKEEPING
(Lesson 3 of 3 Lessons)
Write the answers to these questions in your notebook. The
problem numbering continues from Lesson 2.
19.	How can samples for lab tests be collected without going
beyond guardrails or chains?
20.	What should be done with the jagged ends of glass tubes?
21.	How should hot lab equipment be handled?
22.	How can a fire be extinguished?
23.	Fires can be prevented by good housekeeping and proper
handling of flammables. True or False?
24.	Why should plant water supplies be checked monthly for
coliform group bacteria?
25.	Why should safety equipment be checked periodically?
26.	Where would you look for safety posters, signs, and slo-
gans to aid in "tailgate" safety meetings?
27.	Carefully study this illustration. List the safety hazards and
indicate how each one can be corrected.
IS
PLEASE WORK THE OBJECTIVE TEST NEXT.

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234 Treatment Plants
SUGGESTED ANSWERS
Chapter 14. PLANT SAFETY AND GOOD HOUSEKEEPING
Answers to questions on page 212.
14.1A You can protect yourself and your family from disease
by thoroughly washing your hands after being in con-
tact with wastewater and sludges and by careful clean-
ing of your work clothes.
14.1B Before entering an unventilated, enclosed structure
you should check for oxygen deficiency and provide
ventilation.
14.1C Toxic gases and vapors originate from the discharge
of certain industrial wastes into the wastewater collec-
tion system. The decomposition of certain wastes will
also produce dangerous gases too.
Answers to questions on page 214.
14.2A Someone should always be standing near a manhole
when you enter it in case you collapse from an oxygen
deficiency or are overcome by a toxic gas. An addi-
tional person should be in the vicinity to help the per-
son at the top of the manhole recover you by pulling on
the safety harness if you need help.
14.2B Instruments are available to measure the concentra-
tions of oxygen and toxic gases in manholes and other
enclosed areas.
14.2C Insist that the equipment vendor provide you and your
coworkers with the proper instruction regarding the
use of equipment.
14.2D Traffic may be alerted by signs, flags, fluorescent
cones, flagmen, and flashing lights on a truck parked
in front of the manhole.
END OF ANSWERS TO QUESTIONS IN LESSON 1
Answers to questions on page 215.
14.2E Moving equipment in pumping stations includes recip-
rocating equipment and rotating shafts. Safety precau-
tions include guards over couplings and shafts and not
wearing loose clothing and rings or other jewelry
around machinery and securing long hair.
14.2F Fire extinguishers in pumping stations should be of a
type that may be used on electrical equipment as well
as on solid material and/or power overload-type fires.
The use of liquid-type fire extinguishers should be
avoided. All-purpose A-B-C chemical-type fire extin-
guishers are recommended.
Answers to questions on pages 216 and 219.
14.2G Slimes, rags, or greases should be removed from any
area because they may cause people to slip and they
are unsightly.
14.2H When working on a mechanical or electrical part of
equipment, you should fasten a tag to the breaker
handle reading "DANGER, Do Not Start, Man Working
on Equipment," or some other similar notice and lock
out the equipment.
14.21 Guards should be placed around moving parts of
equipment such as rotating shaft couplings, belt
drives, and other moving parts normally accessible.
14.2J Our noses eventually become insensitive to some
odors, such as hydrogen sulfide gas. This phenome-
non is known as "olfactory fatigue."
14.2K Tools and equipment should not be carried, but should
be transported in and out of pits and sumps by the use
of buckets and handline or sling.
Answers to questions on page 221.
14.2L Slippery surfaces such as stairs, ladders, and cat-
walks can be made less dangerous if nonskid strips or
coatings are applied at proper locations.
14.2M Smoking and open flames should not be allowed in the
vicinity of digesters because when methane gas is
mixed with the proper portion of air it forms an explo-
sive mixture.
14.2N Before entering a recently emptied digester, you must
ventilate the digester and check for an explosive at-
mosphere.
14.20 Before relighting a waste gas burner, the main gas
valve should be turned off and the stack allowed to
vent itself for a few minutes.
14.2P If a positive displacement pump is started against a
closed discharge valve, pressures could build up and
break a pipe or damage the pump.
Answers to questions on page 222.
14.2Q When using a boat to collect samples from a pond,
have someone standing by in case you get into
trouble, wear an approved life jacket, and do not stand
up in the boat while performing work.
14.2R The rotary distributor should be stopped by turning off
the flow of water. Extreme care must be taken be-
cause of the force developed by the distributor.
14.2S You should never work alone on the center "Y" wall of
an aerator because you could fall into the aerator and
need help getting out.
Answers to questions on page 223.
14.2T Chlorine containers should only be lifted by an ap-
proved lifting bar with hooks over the ends.
14.2U Chlorine gas is heavier than air and is best removed
when leaks occur by blowing the gas out of the room at
floor level.
14.2V If you open a door and smell chlorine, immediately
close the door, turn on the ventilator, and seek help.
14.2W Good housekeeping can and has prevented many ac-
cidents. You should keep your plant clean, provide
containers for wastes, and empty them regularly.

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Safety 235
Answers to questions on page 224.
14.2X Major types of discharges from industrial plants that
could create safety hazards include:
1.	Fuels,
2.	Toxic gases,
3.	Amines,
4.	Surface-active agents, and
5.	Biocides.
14.2Y If gasoline reaches the wet well in the headworks of
your treatment plant:
1.	Try to remove the gasoline from the surface of the
wet well with skimmers (if available) or with a port-
able pump.
2.	Apply as much ventilation as possible to prevent an
explosive atmosphere from developing,
3.	Monitor the atmosphere for toxic and explosive
conditions,
4.	Keep personnel away from the area, and
5.	Do not allow any flames or sparks in the area (use
nonsparking tools, equipment and wiring).
14.2Z Surface-active agents can cause three types of prob-
lems.
1.	Super floe agents can produce a much denser
sludge than usually pumped. This sludge can be
too thick to pump, which then requires special han-
dling to reslurry the sludge so it can be pumped.
2.	Antifloc agents can lower the capture of suspended
solids in primary clarifiers and cause a solids over-
load on downstream treatment processes.
3.	Foaming agents can cause foam to cover treat-
ment processes and prevent inspection and main-
tenance. Foam that blows into neighbors' yards or
forms on the surface of receiving waters is ob-
jectionable to the public.
END OF ANSWERS TO QUESTIONS IN LESSON 2
Answers to questions on page 226.
14.3A When collecting influent samples, rubber gloves
should be worn to protect the operator's hands if there
is any chance of direct contact with the wastewater. If
possible, sample poles or other similar types of
samplers should be used.
14.3B Hands should always be washed before eating to pre-
vent the spread of disease.
14.3C Chemicals and reagents should be handled with care
to protect your body from serious injuries and possible
poisoning.
Answers to questions on page 227.
14.4A The necessary ingredients of a fire are fuel, heat, and
oxygen.
14.4B Oil- and paint-soaked rags should be placed in
covered metal containers and regularly disposed of in
a safe manner.
Answer to question on page 229.
14.5A Some treatment plants use bottled drinking water be-
cause it is an economical and reliable source of pota-
ble water. This practice reduces the possibility of the
spread of disease from unknown cross-connections or
defective devices installed to prevent contamination
by back-flows.
Answer to question on page 229.
14.6A The following phone numbers should be conspicu-
ously listed in your plant: Fire Department, Police De-
partment, Ambulance, Chlorine Supplier or Repair-
man, and Physician. Check your list to be sure they
are all listed and the numbers are correct.
Answers to questions on page 229.
14.7A The purpose of safety meetings is to remind operators
of the need for safety, and to review potential hazards
and how to correct or avoid dangerous situations.
14.7B Safety meetings should be held every 7 to 10 days.
Answers to questions on page 231.
14.8A Safety meetings could be:
1.	Formal, organized meeting,
2.	Tailgate safety session, and
3.	Informal get togethers or bull sessions.
14.8B Management must actively support a safety training
program and demand that safe equipment and proce-
dures be used at all times. An effective safety training
program must start at the top.
14.8C Safety drills should be held regularly so everyone
knows how to respond during emergencies. Do not
wait for an emergency before trying to learn how to
use safety equipment. Get proper instructions and
conduct practice sessions.
14.8D Paper work necessary for an effective safety training
program includes:
1.	Accident report forms,
2.	Safety policy,
3.	Safety rules,
4.	Supervisor's guides, and
5.	Checklists for review of plans and specifications
and also for plant inspections.
END OF ANSWERS TO QUESTIONS IN LESSON 3

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236 Treatment Plants
OBJECTIVE TEST
Chapter 14. PLANT SAFETY AND GOOD HOUSEKEEPING
Please write your name and mark the correct answers on the
answer sheet as directed at the end of Chapter 1. There may
be more than one correct answer to each question.
1.	Accidents don't just happen, they are caused.
1.	True
2.	False
2.	The greatest safety hazard working in and around a
clarifier is asphyxiation.
1.	True
2.	False
3.	An operator's nose never becomes insensitive to danger-
ous gases.
1.	True
2.	False
4.	Toxic and oxygen deficient atmospheres may be found in
recently emptied anaerobic digesters.
1.	True
2.	False
5.	Operators don't have to worry about hazardous industrial
waste discharges because industry will take care of these
problems.
1.	True
2.	False
6.	Flammable fuels may reach a treatment plant as a result
of a gasoline truck accident and the spilled gasoline flows
into a storm sewer connected to a sanitary sewer.
1.	True
2.	False
7.	Biocides are easily detected before they reach organisms
purifying the wastewater in treatment processes.
1.	True
2.	False
8.	Lift heavy weights on the job with your back muscles.
1.	True
2.	False
9.	Wear gloves when cleaning pump casings to protect your
hands from dangerous sharp objects.
1.	True
2.	False
10. Slippery footing is a constant danger in and around treat-
ment plant facilities.
1.	True
2.	False
11.	Guards are needed around power-drive units.
1.	True
2.	False
12.	Drowning is a danger when working around ponds.
1.	True
2.	False
13.	Drinking water used at wastewater treatment plants does
not have to be tested.
1.	True
2.	False
14.	Guard rails are always safe.
1.	True
2.	False
15.	You may safely enter a manhole when you are alone if you
have tested the atmosphere and properly ventilated the
manhole.
1.	True
2.	False
16.	Why should explosion-proof lights be used when working
in an empty digester?
1.	Explosion-proof lights will not produce a spark which
could cause an explosion.
2.	If there is an explosion, the lights won't go out.
17.	The greatest hazard working in a clarifier is
1.	Asphyxiation.
2.	Explosions.
3.	Slipping.
18.	Gases may accumulate in sludge pump rooms from
1.	Blowers.
2.	Chlorinators.
3.	Leakage.
4.	Normal pump cleaning.
5.	Underground seepage.
19.	An oxygen deficiency, or dangerous concentration of toxic
or suffocating gases, may be found in
1.	Chlorinator rooms.
2.	Empty digesters.
3.	Manholes.
4.	Pump rooms.
5.	Wet wells.
20.	Manhole lids should be lifted with
1.	A differential pulley.
2.	A magnet.
3.	A manhole hook.
4.	Your back.
5.	Your fingers.

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Safety 237
21.	Traffic may be warned of a job in a street or other traffic
area by
1.	A flagman directing traffic.
2.	High-level signs and flags far enough ahead of the job
to adequately alert drivers.
3.	Hoping autos headed toward the work area will be
warned by other drivers.
4.	Leaving some manholes open so everyone can see
that you are working.
5.	Traffic cones arranged to guide traffic around work
area.
22.	To minimize the danger of coming in contact with infec-
tions and infectious diseases, you should
1.	Never repair equipment that comes in contact with
sludge.
2.	Not wear your work clothes home.
3.	Wash your hands before eating.
4.	Wash your hands before going to the toilet.
5.	Wear protective gloves when in contact with wastewa-
ter and sludges.
23.	Good housekeeping around a treatment plant means
1.	Hosing down all spills immediately.
2.	Keeping all walking areas clean and free of slimes, oils,
and greases.
3.	Painting equipment exposed to the weather on a regu-
lar basis.
4.	Piling oily rags in a corner out of the way.
5.	Providing a proper place for equipment and tools.
24.	When working in an empty digester, an operator should
1.	Test for explosive gas mixtures.
2.	Test for H2S.
3.	Use explosion-proof lights.
4.	Ventilate the digester.
5.	Wear nonsparking shoes.
25.	When working on any piece of electrical equipment, the
circuit breaker should be (pick only the best answer)
1.	Closed.
2.	Locked out.
3.	Locked out and tagged.
4.	Open.
5.	Tagged.
27.	When applying protective coatings in a tank, the operator
should
1.	Apply protective creams to exposed skin areas.
2.	Avoid breathing fumes from the protective coating.
3.	Check with the manufacturer for safety precautions.
4.	Provide adequate ventilation.
5.	Wear protective clothing.
28.	When working in the lab, you may
1.	Add acid to water.
2.	Hold a piece of glassware in your bare hands while
heating it.
3.	Look into the end of a container during a reaction or
when heating the container.
4.	Smoke whenever you wish.
5.	Use laboratory glassware for a coffee cup.
29.	The purpose of a safety meeting is to
1.	Discuss the causes of accidents.
2.	Provide an awareness of the need for safety at all
times.
3.	Review potential safety hazards and outline the neces-
sary precautions.
4.	Schedule preventive maintenance.
5.	Study for certification examinations.
REVIEW QUESTIONS:
30.	How many pounds of solids are under aeration in an aera-
tion tank with a capacity of 0.4 MG when the MLSS is 2000
mgJL?
1.	650 pounds
2.	5000 pounds
3.	6500 pounds
4.	6700 pounds
5.	7000 pounds
31.	What is the food to organism ratio in an aeration tank if
1,000 pounds of BOD are added per day and 3,500
pounds of solids are under aeration?
1.	25 lbs BOD per day per 100 lbs of aeration solids
2.	28 lbs BOD per day per 100 lbs of aeration solids
3.	30 lbs BOD per day per 100 lbs of aeration solids
4.	32 lbs BOD per day per 100 lbs of aeration solids
5.	35 lbs BOD per day per 100 lbs of aeration solids
26. When working around a trickling filter, the operator should	END OF OBJECTIVE TEST
1.	Always provide a firm base when jacking up the dis-
tributor for repairs.
2.	Never try to stop a rotating distributor by standing in
front of it.
3.	Never walk on the filter media while the rotating dis-
tributor is moving.
4.	Ride on the distributor to get from one side to the other.
5.	Walk very cautiously on the media.

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CHAPTER 15
MAINTENANCE
GENERAL PROGRAM
by
Norman Farnum
MECHANICAL MAINTENANCE
by
Stan Walton
UNPLUGGING PIPES, PUMPS AND VALVES
by
John Brady
FLOW MEASUREMENT
by
Roger Peterson
REVISED
by
Malcolm Carpenter

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240 Treatment Plants
TABLE OF CONTENTS
Chapter 15. Maintenance
Page
OBJECTIVES	243
GLOSSARY 	244
LESSON t
15.0	Treatment Plant Maintenance - General Program	245
15.00	Preventive Maintenance Records	245
15.01	Building Maintenance 	247
15.02	Plant Tanks and Channels	247
15.03	Plant Grounds	248
15.04	Chlorinators	248
15.040	Maintenance	248
15.041	Chlorine and Sulfur Dioxide Safety 	249
15.042	Emergencies	249
15.04 Library 	249
LESSON 2
15.1	Mechanical Equipment 	250
15.10	Repair Shop 	250
15.11	Pumps 	250
15.110	Centrifugal Pumps	250
15.111	Propeller Pumps	257
15.112	Vertical Wet Well Pumps	257
15.113	Reciprocating or Piston Pumps	257
15.114	Incline Screw Pumps	257
15.115	Progressive Cavity (Screw-Flow) Pumps 	257
15.116	Pneumatic Ejectors	257
15.12	Pump Lubrication	257
15.13	Starting a New Pump 	269
15.14	Pump Shutdown	269
15.15	Pump-Driving Equipment		

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Maintenance 241
15.16	Electrical Controls 	269
15.17	Operating Troubles 	269
15.18	Starting and Stopping a Pump on Line	270
15.180	Centrifugal Pumps		270
15.181	Positive Displacement Pumps	274
LESSON 3
15.2	Mechanical Maintenance 	275
The format of this section differs slightly from the others. The arrangement of procedures was designed specif-
ically to assist you in planning an effective preventive maintenance program. The contents are at the beginning of
the section, and the paragraphs are numbered for easy reference on equipment service record cards.
PARAGRAPH
1.	Pumps, General (Incl. Packing)	276
2.	Reciprocating Pumps, General 	283
3.	Propeller Pumps, General 	285
4.	Progressive Cavity Pumps, General	285
5.	Pneumatic Ejectors, General	285
6.	Float and Electrode Switches 	285
LESSON 4
7.	Electric Motors 	287
8.	Belt Drives	290
9.	Chain Drives	290
10.	Variable Speed Belt Drives 	291
11.	Couplings	293
12.	Shear Pins	295
LESSON 5
13.	Gate Valves	296
14.	Check Valves 	299
15.	Plug Valves	299
16.	Sluice Gates	299
17.	Dehumidifiers 	308
18.	Air-Gap Separation Systems	308
19.	Plant Safety Equipment	308
20.	Acknowledgment 	308
LESSON 6
15.3	Unplugging Pipes, Pumps and Valves	311
15.30 Plugged Pipeline 	311

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242 Treatment Plants
15.31	Scum Lines	311
15.32	Sludge Lines	311
15.33	Digested Sludge Lines 	311
15.34	Unplugging Pipelines	311
15.340	Pressure Methods	311
15.341	Cutting Tools	312
15.342	High Velocity Pressure Units	312
15.343	Last Resort	312
15.35	Plugged Pumps and Valves	312
15.4	Flow Measurements - Meters and Maintenance 	312
15.40	Flow Measurements, Use and Maintenance	312
15.41	Operators' Responsibilities	313
15.42	Various Devices for Flow Measurement	313
15.43	Location of Measuring Devices	315
15.44	Conversion and Readout Instruments and Controls	315
15.440	Mechanical Meters	315
15.441	Transmitters 	315
15.442	Receivers	316
15.443	Controllers	316
15.45	Sensor Maintenance	316
15.46	Conversion and Readout Instrument Maintenance	318
15.47	Manufacturers' Responsibilities	318
15.48	Calibration and Cross-Checking Meter Performance	318
15.49	Troubleshooting Meters 	319
15.5	Review of Plans and Specifications	319
15.50	Examining Prints 	319
15.51	Reading Specifications	319
15.6	Summary	320
15.7	Additional Reading	320

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Maintenance 243
OBJECTIVES
Chapter 15. MAINTENANCE
Following completion of Chapter 15, you should be able to
do the following:
1.	Develop a maintenance program for your plant, including
equipment, buildings, grounds, channels, and tanks.
2.	Start a maintenance record-keeping system that will pro-
vide you with information to protect equipment warranties,
to prepare budgets, and to satisfy regulatory agencies,
3.	Schedule maintenance of equipment at proper time inter-
vals,
4.	Perform maintenance as directed by manufacturers,
5.	Recognize symptoms that indicate equipment is not per-
forming properly, identify the source of the problem, and
take corrective action,
6.	Start and stop pumps,
7.	Unplug pipes, pumps, and valves,
8.	Explain the operation and maintenance of sensors, trans-
mitters, receivers, and controllers, and
9.	Determine when you need assistance to correct a problem.
NOTE: 1. Special maintenance information is given in the pre-
vious chapters on treatment processes where ap-
propriate.
2. Also see Chapter 29, "Support Systems," for more
information.

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244 Treatment Plants
GLOSSARY
Chapter 15. MAINTENANCE
AIR GAP
An open vertical drop, or vertical empty space, between a drinking (potable) water
supply and the point of use in a wastewater treatment plant. This gap prevents
back siphonage because there is no way wastewater can reach the drinking water.
DRINKING
WATER
AIR GAP
3
AIR
.GAP
OPEN
TANK
TO
PLANT
I PUMP
1

AXIS OF IMPELLER
AXIAL TO IMPELLER
AXIS OF IMPELLER
In line with the shaft.
AXIAL TO IMPELLER
Material being pumped flows around the impeller or parallel to the shaft.
CROSS CONNECTION	CROSS CONNECTION
A connection between drinking (potable) water and an unsafe water supply. For example, if you have a pump moving nonpotable
water and hook into the drinking water system to supply water for the pump seal, a cross connection or mixing between the two
water systems can occur. This mixing may lead to contamination of the drinking water.
DATEOMETER (day-TOM-uh-ter)	DATEOMETER
A small calendar disc attached to motors and equipment to indicate the year in which the last maintenance service was performed.
MULTI-STAGE PUMP
A pump that has more than one impeller. A single-stage pump has one impeller.
PRUSSIAN BLUE
A paste or liquid used to show a contact area. Used to determine if gate valve seats fit properly.
RADIAL TO IMPELLER
Material being pumped flows at right angle to the impeller or perpendicular to the shaft.
SINGLE-STAGE PUMP
A pump that has only one impeller. A multi-stage pump has more than one impeller.
STATOR
That portion of a machine which contains the stationary (non-moving) parts that surround the moving parts (rotor).
STETHOSCOPE
An instrument used to magnify sounds and convey them to the ear.
MULTI-STAGE PUMP
PRUSSIAN BLUE
RADIAL TO IMPELLER
SINGLE-STAGE PUMP
STATOR
STETHOSCOPE

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Maintenance 245
CHAPTER 15.
(Lesson 1
15.0 TREATMENT PLANT MAINTENANCE — GENERAL
PROGRAM
A treatment plant operator has many duties. Most of them
have to do with the efficient operation of the plant. An operator
has the responsibility to discharge an effluent that will meet all
the requirements established for the plant. By doing this, the
operator develops a good working relationship with the reg-
ulatory agencies, water recreationists, water users, and plant
neighbors.
Another duty an operator has is that of PLANT MAINTE-
NANCE. A good maintenance program is a must in order to
maintain successful operation of the plant. A successful main-
tenance program will cover everything from mechanical
equipment to the care of the plant grounds, buildings, and
structures.
Mechanical maintenance is of prime importance as the
equipment must be kept in good operating condition in order
for the plant to maintain peak performance. Manufacturers
provide information on the mechanical maintenance of their
equipment. You should thoroughly read their literature on your
plant equipment and UNDERSTAND the procedures. Contact
the manufacturer or the local representative if you have any
questions. Follow the instructions very carefully when perform-
ing maintenance on equipment. You also must recognize tasks
that may be beyond your capabilities or repair facilities, and
you should request assistance when needed.
For a successful maintenance program, your supervisors
must understand the need for and benefits from equipment
that operates continuously as intended. Disabled or improperly
working equipment is a threat to the quality of the plant
effluent, and repair costs for poorly maintained equipment
usually exceed the cost of maintenance.
15.00 Preventive Maintenance Records
Preventive programs help operating personnel keep equip-
ment in satisfactory operating condition and aid in detecting
and correcting malfunctions before they develop into major
problems.
MAINTENANCE
: 6 Lessons)
A frequent occurrence in a preventive maintenance program
is the failure of the operator to record the work after it is com-
pleted. When this happens the operator must rely on memory
to know when to perform each preventive maintenance func-
tion. As days pass into weeks and months, the preventive
maintenance program is lost in the turmoil of everyday opera-
tion.
The only way an operator can keep track of a preventive
maintenance program is by GOOD RECORD KEEPING.
Whatever record system is used, it should be kept up to date
on a daily basis and not left to memory for some other time.
Equipment sen/ice record cards (Fig. 15.1) are easy to set up
and require little time to keep up to date.
An EQUIPMENT SERVICE CARD (master card) should be
filled out for each piece of equipment in the plant. Each card
should have the equipment name on it, such as Sludge Pump
No. 1, Primary Clarifier.
1.	List each required maintenance service with an item
number.
2.	List maintenance services in order of frequency of perform-
ance. For instance, show daily service as items 1, 2, and 3
on the card; weekly items as 4 and 5; monthly items as 6, 7,
8, and 9; and so on.
3.	Describe each type of service under work to be done.
Make sure all necessary inspections and services are
shown. For reference data, list paragraph or section numbers
as shown in the mechanical maintenance section of this lesson
(Section 15.2, p. 275). Also list frequency of service as shown
in the time schedule columns of the same section. Under time,
enter day or month service is due. Service card information
may be changed to fit the needs of your plant or particular
equipment as recommended by the equipment manufacturer.
Be sure the information on the cards is complete and correct.
The SERVICE RECORD CARD should have the date and
work done, listed by item number and signed by the operator
who performed the service. Some operators prefer to keep
both cards clipped together, while others place the service
record card near the equipment.
When the service record is filled, it should be filed for future
reference and a new card attached to the master card. The
EQUIPMENT SERVICE CARD tells what should be done and
when, while the SERVICE RECORD CARD is a record of what
you did and when you did it.

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246 Treatment Plants
EQUIPMENT SERVICE CARD
EQUIPMENT: #1 Raw Wastewater Lift Pump
Item No.
Work to be Done
Reference
Frequency
Time
1
Check water seal and packing gland
Par. 1
Daily

2
Operate pump alternately
Par. 1
Weekly
Monday
3
Inspect pump assembly
Par. 1
Weekly
Wed.
4
Inspect and lube bearings
Par. 1
Quarterly
1-4-7-10*
5
Check operating temperature of
bearings
Par. 1
Quarterly
1-4-7-10
6
Check alignment of pump and motor
Par. 1
Semi-Ann.
4 & 10
7
Inspect and service pumps
Par. 1
Semi-Ann.
4 & 10
8
Drain pump before shutdown
Par. 1












* 1-4-7-10 represent the months of the year when the equipment should be serviced — 1. January, 4. April, 7. July, and 10. October.
SERVICE RECORD CARD
EQUIPMENT: #1 Raw Wastewater Lift Pump


Date
Work Done
(Item No.)
Slgned

Date
Work Done
(Item No.)
Signed
1-5-80
1 & 2
J.B.



1-6-80
1
J.B.



1-7-80
1-3-4-5-
R.W.







































Fig. 15.1
Equipment service card and service record card

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Maintenance 247
QUESTIONS
Write your answers in a notebook and then compare your
answers with those on page 321.
15.0A Why should you plan a good maintenance program for
your treatment plant?
15.0B What general items would you include in your mainte-
nance program?
15.0C Why should your maintenance program be accom-
panied by a good record keeping system?
15.0D What is the difference between an EQUIPMENT
SERVICE CARD and a SERVICE RECORD CARD?
15.01	Building Maintenance
Building maintenance is another program that should be
maintained on a regular schedule. Buildings in a treatment
plant are usually built of sturdy materials to last for many years.
Buildings must be kept in good repair. In selecting paint for a
treatment plant, it is always a good idea to have a painting
expert help the operator select the types of paint needed to
protect the buildings from deterioration. The expert also will
have some good ideas as to color schemes to help blend the
plant in with the surrounding area. Consideration should also
be given to the quality of paint. A good quality, more expensive
material will usually give better service over a longer period of
time than the economy-type products.
Building maintenance programs depend on the age, type,
and use of a building. New buildings require a thorough check
to be certain essential items are available and working prop-
erly. Older buildings require careful watching and prompt atten-
tion to keep ahead of leaks, breakdowns, replacements when
needed, and changing uses of the building. Attention must be
given to the maintenance requirements of many items in all
plant buildings, such as electrical systems, plumbing, heating,
cooling, ventilating, floors, windows, roofs, and drainage
around the buildings. Regularly scheduled examinations and
necessary maintenance of these items can prevent many
costly and time-consuming problems in the future.
In each plant building, periodically check all stairways, lad-
ders, catwalks, and platforms for adequate lighting, head
clearance, and sturdy and convenient guardrails. Protective
devices should be around all moving equipment. Whenever
any repairs, alterations, or additions are built, avoid building
accident traps such as pipes laid on top of floors or hung from
the ceiling at head height which could create serious safety
hazards.
Organized storage areas should be provided and main-
tained in an accessible and neat manner.
KEEP ALL BUILDINGS CLEAN AND ORDERLY. Janitorial
work should be done on a regular schedule. All tools and plant
equipment should be kept clean and in their proper place.
Floors, walls, and windows should be cleaned at regular inter-
vals in order to maintain a neat appearance. A treatment plant
kept in a clean, orderly condition makes a safe place to work
and aids in building good public and employer relations.
15.02	Plant Tanks and Channels
Plant tanks and channels such as clarifiers, channels, grit
channels, and wet wells should be drained and inspected at
least once a year. Be sure the groundwater level is down far
enough so the tanks will not float on the groundwater when
empty or develop cracks from groundwater pressure.
Schedule inspections of tanks and channels during periods
of low inflow. Route flows through alternate units, if available;
otherwise provide the best possible treatment with remaining
units not being inspected or repaired.
All metal and concrete surfaces that come in contact with
wastewater and covered surfaces exposed to fumes should
have a good protective coating. The coating should be
reapplied where necessary at each inspection.
Digesters should also be drained and cleaned on a regular
basis. Once every five years (actual times range from three to
eight years) has been accepted as an approximate interval for
this operation. Most digesters have a sludge inlet box on one
side and a supernatant box on the opposite side. A sludge
sampler can be lowered through the pipes into both of these
boxes to check for sand and grit buildup. To determine the
amount of grit buildup, you must know the side wall depth of
the digester. If the sludge sampler will only drop to within four
feet (1.2 m) of the bottom, you can assume that you have a
four-foot buildup of sand and grit. By measuring the depth of
sand and grit at periodic intervals, you can determine how fast
the buildup is accumulating. In digesters, all metal and con-
crete surfaces should be inspected for deterioration.
On surfaces where the protective coatings are dead and
flake off, it is necessary to sand blast the entire surface before
new coatings are applied. Usually two or more coats are
needed for proper protection.
The protective coatings used on these types of tanks and
channels are usually of black asphaltic-type paint. These coat-
ings should be used wherever practical. In areas where fumes
and moisture are not severe, aluminum or a color scheme may
be desirable. In these areas, a rubber-base paint or some
similar material may be used. Follow the recommendations of
a paint expert.
-	.	_	CAUTION 1		—	
PE0OPIC t7tZAIWA<2>£, IN4P£CTION, ANU
REPAIE Of=- TANKS AMP CHANNELS I^
E4^6MTIAL-. FAILURE- TO PO «O MAV
KE4ULT IN CO/MPL-e-fE Cn4euPT"/OW OF-
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-------
248 Treatment Plants
15.03	Plant Grounds
Plant grounds that are well groomed and kept in a neat
condition will greatly add to the appearance of the overall plant
area. This is important to the operator in building good rela-
tions with plant neighbors as well as the general public. Good
appearance also aids in the eyes of management as to your
ability as an operator.
If the plant grounds have not been landscaped, it is some-
times the responsibility of the operator to do so. This may
consist of planting shrubs and lawns or just keeping the
grounds neat and weed free. Some plant grounds may be
entirely paved. In any case, they should be kept clean and
orderly at all times.
Control rodents and insects so they won't spread diseases
or cause nuisances.
For the convenience of visitors and new operators, signs
directing people to the plant, indicating the way to different
plant facilities, identifying plant buildings and the direction of
flow and contents flowing in a pipe can all be very helpful.
Well-lighted and well-maintained walks and roadways are very
important. Plant grounds should be fenced to prevent unau-
thorized persons and animals from entering the area. Keep
seldom-used items and old, discarded equipment neatly stored
to avoid the appearance of a cluttered junk yard. Groom your
plant grounds in a fashion that you will be proud of, and you will
be amazed at the favorable impression your facility will convey
to the public and administrators.
QUESTIONS
Write your answers in a notebook and then compare your
answers with those on page 321.
15.0E What items should be included in a building mainte-
nance program?
15.0F When plant tanks and channels are drained, what
items would you inspect?
15.0G Why are neat and well-groomed grounds important?
15.04	Chlorinators
15.040 Maintenance
Chlorine gas leaks around chlorinators or containers of
chlorine will cause corrosion of equipment. Check every day
for leaks. Large leaks will be detected by odor; small leaks may
go unnoticed until damage results. A green or reddish deposit
on metal indicates a chlorine leak. Any chlorine gas leakage in
the presence of moisture will cause corrosion. Always plug the
ends of any open connection to prevent moisture from entering
the lines. Never pour water on a chlorine leak because this will
only create a bigger problem by enlarging the leak. Chlorine
gas reacts with water to form hydrochloric acid.
	^warning!	
AKIOT-Hee IMTt>CTAMT C?£A40M FOG PBeVEWTfN6
CHLOKINfc U&AI^TMAT TW&	i£>
TOXIC TO WUMAN4.
Ammonia water will detect any chlorine leak. A small piece
of cloth, soaked with ammonia water and wrapped around the
end of a short stick, makes a good leak detector. Wave this
stick in the general area of the suspected leak (do not touch
the equipment with it). If chlorine gas leakage is occurring, a
white cloud of ammonium chloride will form. You should make
this test at all gas pipe joints, both inside and outside the
chlorinators, at regular intervals. Bottles of ammonia water
should be kept tightly capped to avoid loss of strength. All pipe
fittings must be kept tight to avoid leaks. NEW GASKETS
SHOULD BE USED FOR EACH NEW CONNECTION.
	f CAUTION |
to LOCATE" A C.HUORIN& LEAk, VO MOT"
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An ammonia-filled spray bottle may be used to look for
chlorine leaks around connections and cylinders. However, do
not use a spray bottle in a room where large amounts of
chlorine gas have already leaked into the air. After one
squeeze, the entire area may be full of white smoke and you
will have trouble locating the leak. Under these conditions, use
a cloth soaked in ammonia water to look for leaks.
The exterior casing of chlorinators should be painted as re-
quired; however, most chlorinators manufactured recently
have plastic cases that do not require protective coatings. A
clean machine is a better operating machine. Glass bell jars
may be cleaned with water and a washing compound. Parts of
a chlorinator handling chlorine gas must be kept dry to prevent
the chlorine and moisture from forming hydrochloric acid.
Some parts may be cleaned, when required, first with water to
remove water soluble material, then with wood alcohol, fol-
lowed by drying. The above chemicals leave no moisture resi-
due. Another method would be to wash them with water and
dry them over a pan or heater to remove all traces of moisture.
Water strainers on chlorinators frequently clog and require
attention. They may be cleaned by flushing with water or, if
badly fouled, they may be cleaned with dilute hydrochloric
acid, followed with a water rinse.
The atmosphere vent lines from chlorinators must be open
and free. These vent lines evacuate the chlorine to the outside
atmosphere when the chlorinator is being shut down. Place a
screen over the end of the pipe to keep insects from building a
nest in the pipe and clogging it up.
When chlorinators are removed from service, as much
chlorine gas as possible should be removed from the supply
lines and machines. The chlorine valves at the containers are
shut off and the chlorinator injector is operated for a period to
remove the chlorine gas. With visible bell jar chlorinators, the
absence of the characteristic yellow color of chlorine is an
indication that the chlorine has been expelled. In "V" notch
chlorinators (Chapter 10), the rotameter goes to the bottom of
the manometer tube when the chlorine gas has been expelled.
All chlorinators will give continuous trouble-free operation if
properly maintained and operated. Each chlorinator manufac-
turer provides with each machine a maintenance and opera-
tions instruction booklet with line diagrams showing the opera-
tion of the component parts of the machine. Manufacturer's
instructions should be followed for maintenance and lubrica-
tion of your particular chlorinator. If you do not have an instruc-
tion booklet, you may obtain one by contacting the manufac-
turer's representative in your area.

-------
Maintenance 249
QUESTIONS
Write your answers in a notebook and then compare your
answers with those on page 321.
15.0H Why should chlorine leaks be detected and repaired?
15.0I How would you search for chlorine leaks?
Taken in part from OPERATING AND MAINTAINING
CHLORINATOR AND CHLORINE CONTAINERS, by LeRoy
W. VanKleek, reprinted from WASTE ENGINEERING, July
1965. Distributed by Wallace &Tiernan, Incorporated.
15.041	Chlorine and Sulfur Dioxide Safety
For information on chlorine and sulfur dioxide safety, see
Chapter 10, "Disinfection and Chlorination," and Chapter 14,
"Plant Safety and Good Housekeeping." READ THESE
CHAPTERS BEFORE ATTEMPTING MAINTENANCE ON
CHLORINATORS, SULFONATORS, LINES, OR CYLINDERS.
Sulfur dioxide (S02) is commonly used today for dechlorina-
tion purposes. Most of the principles which apply to chlorine
also apply to sulfur dioxide. Leaks are detected with ammonia
water. Sulfonators (the machine through which the chemical is
fed) are identical in appearance and function to chlorinators.
Strainers should be kept clear to avoid plugging. Sulfonators
should be completely emptied before performing maintenance.
You must always remember that sulfur dioxide (S02) is just as
toxic to humans as chlorine.
15.042	Emergencies
If your plant has not developed procedures for handling po-
tential emergencies, do it NOW. Emergency procedures must
be established for operators to follow when emergencies are
caused by the release of chlorine, sulfur dioxide, or other
hazardous chemicals. These procedures should include a list
of emergency phone numbers located near a telephone that is
unlikely to be affected by the emergency.
1.	Police
2.	Fire
3.	Hospital and/or Physician
4.	Responsible Plant Officials
5.	Local Emergency Disaster Office
6.	CHEMTREC (800) 424-9300
7.	Emergency Team (if your plant has one)
The CHEMTREC toll-free number may be called at any time.
Personnel at this number will give information on how to han-
dle emergencies created by hazardous materials and will notify
appropriate emergency personnel.
An emergency team for your plant may be trained and as-
signed the task of responding to SPECIFIC EMERGENCIES
such as chlorine or sulfur dioxide leaks. This emergency team
must meet the following strict specifications at all times.
1.	Team personnel must be physically and mentally qualified.
2.	Proper equipment must be available at all times.
a.	Protective equipment, including self-contained breath-
ing apparatus.
b.	Repair kits.
c.	Repair tools.
3.	Proper training must take place on a regular basis and in-
clude instruction about:
a.	Properties and detection of hazardous chemicals.
b.	Safe procedures for handling and storage of chemicals.
c.	Types of containers, safe procedures for shipping con-
tainers, and container safety devices.
d.	Installation of repair devices.
4.	Team members must be exposed regularly to simulated
field emergencies or practice drills. Team response must be
carefully evaluated and any errors or weaknesses cor-
rected.
5.	Emergency team performance must be reviewed annually
on a specified date. Review must include:
a.	Training program.
b.	Response to actual emergencies.
c.	Team physical and mental examinations.
WARNING. One person should never be permitted to attempt
an emergency repair alone. Always wait for trained
assistance. Valuable time could be lost rescuing a
foolish individual rather than repairing or correct-
ing a serious emergency.
15.05 Library
A plant library can contain helpful information to assist in
plant operation. Material in the library should be cataloged and
filed for easy use. Items in the library should include:
1.	Plant operation and maintenance manual.
2.	Plant plans and specifications.
3.	Manufacturers' instructions.
4.	Reference books on wastewater treatment.
5.	Professional journals and publications.
6.	Manuals of Practice and Safety Literature published by the
Water Pollution Control Federation, 2626 Pennsylvania Av-
enue, N.W., Washington, D.C. 20037.
7.	First-aid book.
8.	Reports from other plants.
9.	A dictionary.
QUESTIONS
Write your answers in a notebook and then compare your
answers with those on page 321.
15.0J Prepare a list of emergency phone numbers for your
treatment plant.
15.0K What items should be included in the training program
for an emergency team?
£NP OP IfchkbW 1 Of £
MAt NT6NAN6& @
Please answer the discussion and review questions before
continuing with Lesson 2.

-------
250 Treatment Plants
DISCUSSION AND REVIEW QUESTIONS
Chapter 15. MAINTENANCE
(Lesson 1 of 6 Lessons)
At the end of each lesson in this chapter you will find some
discussion and review questions that you should work before
continuing. The purpose of these questions is to indicate to you
how well you understand the material in the lesson.
Write the answers to these questions in your notebook.
1.	Why should the operator thoroughly read and understand
manufacturers' literature before attempting to maintain
plant equipment?
2.	Why must administrators or supervisors be made aware of
the need for an adequate maintenance program?
3.	What is the purpose of a maintenance record-keeping pro-
gram?
4.	What kinds of maintenance checks should be made period-
ically of stairways, ladders, and catwalks?
5.	When should inspection and maintenance of the underwa-
ter portions of plant structures such as clarifiers and diges-
ters be scheduled?
6.	Why should rodents and insects be controlled?
7.	What items should be included in a plant library?
8.	Why should your plant have an emergency team to repair
chlorine leaks?
9.	Why should one person never be permitted to repair a
chlorine leak alone?
CHAPTER 15. MAINTENANCE
(Lesson 2 of 6 Lessons)
15.1 MECHANICAL EQUIPMENT
Mechanical equipment commonly used in treatment plants
are described and discussed in this section. Equipment used
with specific treatment processes such as clarifiers or aeration
basins are not discussed. Vou must be familiar with equipment
and understand what it is intended to do before developing a
preventive maintenance program and maintaining equipment.
15.10	Repair Shop
Many large plants have fully equipped machine shops
staffed with competent mechanics. But for smaller plants,
adequate machine shop facilities often can be found in the
community. In addition, most pump manufacturers maintain
pump repair departments where pumps can be fully recon-
ditioned.
The pump repair shop in a large plant commonly includes
such items as welding equipment, lathes, drill press and drills,
power hacksaw, flame-cutting equipment, micrometers, calip-
ers, gages, portable electric tools, grinders, a forcing press,
metal-spray equipment, and sand-blasting equipment. You
must determine what repair work you can and should do and
when you need to request assistance from an expert.
15.11	Pumps
Pumps serve many purposes in wastewater collection sys-
tems and treatment plants. They may be classified by the
character of the material handled: raw wastewater, grit,
effluent, activated sludge, raw sludge, or digested sludge. Or,
they may relate to the conditions of pumping: high lift, low lift,
recirculation, or high capacity. They may be further classified
by principle of operation, such as centrifugal, propeller, recip-
rocating, and turbine.
The type of material to be handled and the function or re-
quired performance of the pump vary so widely that the design-
ing engineer must use great care in preparing specifications for
the pump and its controls. Similarly, the operator must conduct
a maintenance and management program adapted to the
peculiar characteristics of the equipment.
15.110 Centrifugal Pumps
A centrifugal pump is basically a very simple device; an
impeller rotating in a casing. The impeller is supported on a
shaft which is, in turn, supported by bearings. Liquid coming in
at the center (eye) of the impeller (Fig. 15.2) is picked up by the
vanes and by the rotation of the impeller and then is thrown out
by centrifugal force into the discharge.
To help you understand how pumps work and the purpose of
the various parts, a section titled "Let's Build a Pump" has
been included on the following pages. This material has been
reprinted with the permission of Allis-Chalmers Corporation,
Milwaukee, Wisconsin, Industrial Pump Division, Norwood!
Ohio. Originally, the material was printed in Allis-Chalmers Bul-
letin No. OBX62568.

-------
Maintenance 251
- ^^Discharge
\ Suction

Impeller ' N
eye
- Vanes
Refer to Fig. 15.3 for location of impeller in pump.
Fig. 15.2 Diagram showing details of centrifugal pump
impeller
(Source: CENTR/FUGAL PUMPS by Karassik and Carter of Worthington Corporation)

-------
252 Treatment Plants
CENT&M('AL	W ACTION^
ALL MOVING BODIES TENO TO TRAVEL IN ASTRAMHT
LINE. WHEN FORCED TO TRAVEL IN A CURVE,THEY
CONSTANTLY TRY TO TRAVEL ON A TANGENT***
'A
4# "gy-nj	II
*'*PlANE RIDE"
1MB
force pushes dummy planes swung1
in a. circle away from center of rotation..
1
Centrifugal force tends to push swirling water
outw&rd... forming vortex in center.

-------
Maintenance 253
Let's Build a Pump!
A student of medicine spends long years learning exactly
how the human body is built before attempting to prescribe for
its care. Knowledge of PUMP anatomy is equally basic in car-
ing for centrifugal pumps!
But whereas the medical student must take a body apart to
learn its secrets, it will be far more instructive to us if we put a
pump TOGETHER (on paper, of course). Then we can start at
the beginning — adding each new part as we need it in logical
sequence.
As we see WHAT each part does, HOW it does it
see how it must be CARED FOR!
we'll
Another analogy between medicine and maintenance: there
are various types of human bodies, but if you know basic
anatomy, you understand them all. The same is true of cen-
trifugal pumps. In building one basic type, we'll learn about ALL
types.
Part of this will be elementary to some maintenance people
... but they will find it a valuable "refresher" course, and, after
all, maintenance just can't be too good.
So with a side glance at the centrifugal principle on the page
at the left, let's get on with building our pump ...
FIRST WE REQUIRE A DEVICE TO SPIN LIQUID AT HIGH
SPEED ...
That paddle-wheel device is called the "impeller"... and it's
the heart of our pump.
Note that the blades curve out from its hub. As the impeller
spins, liquid between the blades is impelled outward by cen-
trifugal force.

1ST. unc	ommi >*
WAT** CATlWlN® STICK*,CTC»
Note, too, that our impeller is open at the center — the
"eye." As liquid in the impeller moves outward, it will suck more
liquid in behind it through this eye ... PROVIDED ITS NOT
CLOGGED!
That brings up Maintenance Rule No. 1: if there's any
danger that foreign matter (sticks, refuse, etc.) may be sucked
into the pump — clogging or wearing the impeller unduly —
PROVIDE THE INTAKE END OF THE SUCTION PIPING WITH
A SUITABLE SCREEN.
NOW WE NEED A SHAFT TO SUPPORT AND TURN THE
IMPELLER ...
Our shaft looks heavy — and it IS. It must maintain the
impeller in precisely the right place.
But that ruggedness does NOT protect the shaft from the
corrosive or abrasive effects of the liquid pumped ... so we
must protect it with sleeves slid on from either end.
-tokSc
Siccvci.
will
Mwrtcr t«* shvt
What these sleeves — and the impeller, too — are made of
depends on the nature of the liquid we're to pump. Generally
they're bronze, but various other alloys, ceramics, glass, or
even rubber-coating are sometimes required.
Maintenance Rule No. 2: NEVER PUMP A LIQUID FOR
WHICH THE PUMP WAS NOT DESIGNED.
Whenever a change in pump application is contemplated
and there's any doubt as to the pump's ability to resist the
different liquid, CHECK WITH YOUR PUMP MANUFAC-
TURER!
WE MOUNT THE SHAFT ON SLEEVE, BALL OR ROLLER
BEARINGS...
As we'll see later, clearances between moving parts of our
pump are QUITE SMALL.
If bearings supporting the turning shaft and impeller are al-
lowed to wear excessively and lower the turning units within a
pump's closely-fitted mechanism, the life and efficiency of that
pump will be seriously threatened.


-------
254 Treatment Plants
Maintenance Rule No. 3: KEEP THE RIGHT AMOUNT OF
THE RIGHT LUBRICANT IN BEARINGS AT ALL TIMES. FOL-
LOW YOUR PUMP MANUFACTURER'S LUBRICATION IN-
STRUCTIONS TO THE LETTER.
Main points to keep in mind are .. .
1.	Although too much oil won't harm sleeve bearings, too
much grease in antifriction type bearings (ball or roller) will
PROMOTE friction and heat. Main job of grease in anti-
friction bearings is to protect steel elements against corro-
sion, not friction.
2.	Operating conditions vary so widely that no one rule as to
frequency of changing lubricant will fit all pumps. So play
safe: if anything, change lubricant BEFORE it's too worn or
too dirty.
TO CONNECT WITH THE MOTOR, WE ADD A COUPLING
FLANGE ...
Some pumps are built with pump and motor on one shaft, of
course, and offer no alignment problem.
But our pump is to be driven by a separate motor... and we
attach a flange to one end of the shaft through which bolts will
connect with the motor flange.

JJ
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Maintenance Rule No. 4: SEE THAT PUMP AND MOTOR
FLANGES ARE PARALLEL VERTICALLY AND AXIALLY . . .
AND THAT THEY'RE KEPT THAT WAY!
If shafts are eccentric or meet at an angle, every revolution
throws tremendous extra load on bearings of both pump and
motor. Flexible couplings will NOT correct this condition if ex-
cessive.
Checking alignment should be regular procedure in pump
maintenance. Foundations can settle unevenly, piping can
change pump position, bolts can loosen. Misalignment is a
MAJOR cause of pump and coupling wear.
NOW WE NEED A "STRAW" THROUGH WHICH LIQUID
CAN BE SUCKED...
Notice two things about the suction piping: 1) the horizontal
piping slopes UPWARD toward the pump; 2) any reducer
which connects between the pipe and pump intake nozzle
should be horizontal at the top — (ECCENTRIC, not concen-
tric).
o
Al I OWED Br 'DOWN-SlOPlN&'Pl'PE AUOWfD BY TAPETJED 'RFDUCE'R
This up-sloping prevents air pocketing in the top of the pipe
... which air might be drawn into the pump and cause loss of
suction.
Maintenance Rule No. 5: ANY DOWNSLOPING TOWARD
THE PUMP IN SUCTION PIPING (AS EXAGGERATED IN THE
DIAGRAMS ABOVE) SHOULD BE CORRECTED.
This rule is VERY important. Loss of suction greatly endan-
gers a pump ... as we'll see shortly.
WE CONTAIN AND DIRECT THE SPINNING LIQUID WITH A
CASING ...
We got a little ahead of our story in the previous paragraphs
... because we didn't yet have the casing to which the suction
piping bolts. And the manner in which it is attached is of great
importance.
Maintenance Rule No. 6: SEE THAT PIPING PUTS ABSO-
LUTELY NO STRAIN ON THE PUMP CASING.
TW€ V/€ll^»N£ CAN
EASILY -RUIH A "PUM"P /

-------
Maintenance 255
When the original installation is made, all piping should be in
place and self-supporting before connection. Openings should
meet with no force. Otherwise the casing is apt to be cracked
... or sprung enough to allow closely-fitted pump parts to rub.
It's good practice to check the piping supports regularly to
see that loosening, or settling of the building, hasn't put strains
on the casing.
NOW OUR PUMP IS ALMOST COMPLETE, BUT IT WOULD
LEAK LIKE A SIEVE ...
We're far enough along now to trace the flow of water
through our pump. It's not easy to show suction piping in the
cross-section view above, so imagine it stretching from your
eye to the lower center of the pump.
Our pump happens to be a "double suction" pump, which
means that water flow is divided inside the pump casing .. .
reaching the eye of the impeller from either side.
/liquid
(	(UHOCK SUCTION)
COMEiour I
fate* nx iu/m/
yy
BUTSOMt OF |T LFAKSuACK^RoM PRESSURE It) SUCTION /
As water is sucked into the spinning impeller, centrifugal
force causes it to flow outward ... building up high pressure at
the outside of the pump (which will force water OUT) and creat-
ing low pressure at the center of the pump (which will suck
water IN.) This situation is diagrammed in the upper half of the
pump, above.
So far so good .. . except that water tends to be sucked
back from pressure to suction through the space between im-
peller and casing — as diagrammed in the lower half of the
pump, above — and our next step must be to plug this leak, if
our pump is to be very efficient!
SO WE ADD WEARING RINGS TO PLUG INTERNAL LIQ-
UID LEAKAGE ...
You might ask why we didn't build our parts closer fitting in
the first place — instead of narrowing the gap between them by
inserting wearing rings.
W
The answer is that those rings are removable and RE-
PLACEABLE .. . when wear enlarges the tiny gap between
them and the impeller. (Sometimes rings are attached to impel-
ler rather than casing — or rings are attached to BOTH so they
face each other.)
.PR'

stPvc,ti'
"DsstHvc,tiv,e
Friction ano
©
A. COT "DEPENDS ON
maintaining, "pr
Maintenance Rule No. 7: NEVER ALLOW A PUMP TO RUN
DRY (either through lack of proper priming when starting or
through loss of suction when operating). Water is a LUBRI-
CANT between rings and impeller.
Maintenance Rule No. 8: EXAMINE WEARING RINGS AT
REGULAR INTERVALS. When seriously worn, their replace-
ment will greatly improve pump efficiency.
TO KEEP AIR FROM BEING SUCKED IN, WE USE STUFF-
ING BOXES...
We have two good reasons for wanting to keep air out of our
pump: 1) we want to pump water, not air; 2) air leakage is apt
to cause our pump to lose suction.
Each stuffing box we use consists of a casing, rings of pack-
ing and a gland at the outside end.
TUli IS THE 
TACKINft
Maintenance Rule No. 9: PACKING SHOULD BE RE-
PLACED PERIODICALLY - DEPENDING ON CONDITIONS -
USING THE PACKING RECOMMENDED BY YOUR PUMP
MANUFACTURER. Forcing in a ring or two of new packing
instead of replacing worn packing is BAD PRACTICE. It's apt
to displace the seal cage (see next page).
Put each ring of packing in separately, seating it firmly be-
fore adding the next. Stagger adjacent rings so the points
where their ends meet do not coincide.
Maintenance Rule No. 10: NEVER TIGHTEN A GLAND
MORE THAN NECESSARY ... as excessive pressure will
wear shaft sleeves unduly.
Maintenance Rule No. 11: IF SHAFT SLEEVES ARE BADLY
SCORED, REPLACE THEM IMMEDIATELY ... or packing life
will be entirely too short.

-------
256 Treatment Plants
TO MAKE PACKING MORE AIR-TIGHT, WE ADD WATER
SEAL PIPING ...
In the center of each stuffing box is a "seal cage." By con-
necting it with piping to a point near the impeller rim, we bring
liquid UNDER PRESSURE to the stuffing box.
This liquid acts both to block out air intake and to lubricate
the packing. It makes both packing and shaft sleeves wear
longer. . . PROVIDING IT'S CLEAN LIQUID!
&
WAT-ET5, 15 A LUB^CTAHT!
3. Friction in piping should be minimized . .. use as few and
as easy bends as possible ... avoid scaled or corroded
pipe
DISCHARGE lift, plus suction lift, plus friction in the piping
from the point where liquid enters the suction piping to the end
of the discharge piping equals total head.
PUMPS SHOULD BE OPERATED NEAR THEIR RATED
HEADS.
Otherwise, pump is apt to operate under unsatisfactory and
unstable conditions which reduce efficiency and operating life
of the unit.
Note the description of "cavitation" below — and directions
for figuring the head your pumps are working against.
PUMP CAPACITY generally is measured in gallons per
minute. A new pump is guaranteed to deliver its rating in ca-
pacity and head.
But whether a pump RETAINS its actual capacity depends to
a great extent on its maintenance.
Wearing rings must be replaced when necessary — to keep
internal leakage losses down.
Friction must be minimized in bearings and stuffing boxes by
proper lubrication . .. and misalignment must not be allowed to
force scraping between closely-fitted pump parts.
POWER of the driving motor, like capacity of the pump, will
not remain at a constant level without proper maintenance. (If
you use electric motors, by all means send for Allis-Chalmers
free "Guide to Care of Electric Motors!")
Starting load on motors can be reduced by throttling or clos-
ing the pump discharge valve (NEVER the suction valve!) ...
but the pump must not be operated for long with the discharge
valve closed. Power then is converted into friction — overheat-
ing the water with serious consequences.
Maintenance Rule No. 12: IF THE LIQUID BEING PUMPED
CONTAINS GRIT, A SEPARATE SOURCE OF SEALING LIQ-
UID SHOULD BE OBTAINED (e.g. it may be possible to direct
some of the pumped liquid into a container and settle the grit
out).
To control liquid flow, draw up the gland just tight enough so
a THIN stream flows from the stuffing box during pump opera-
tion.
DISCHARGE PIPING COMPLETES THE PUMP INSTALLA-
TION — AND NOW WE CAN ANALYZE THE VARIOUS
FORCES WE'RE DEALING WITH ...

SUCTION At least 75% of centrifugal pump troubles trace to
the suction side. To minimize them ...
1.	Total suction lift (distance between center line of pump and
liquid level when pumping, plus friction losses) generally
should not exceed 15 feet.
2.	Piping should be at least a size larger than pump suction
nozzle.
A HBM THr KfSPCcr FOP CAV/rA7toN}
IF PUMP CAPACITY, SPEED, HEAD, AND SUCTION LIFT
AREN'T FIGURED PROPERLY, CAVITATION CAN EAT AN
IMPELLER AWAY FAST! A LABORATORY WATER
.HAMMER INDICATES IT'S EROSIVE FORCE ...
I FAST MQVI ME NT
OF (MPfcLlfR 81 AOf
1KBOUGH WAU ft . . .
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Maintenance 257
Centrifugal pumps designed for pumping wastewater (Figs.
15.3 and 15.4) usually have smooth channels and impellers
with large-sized openings to prevent clogging.
Impellers may be of the open or closed type (Fig. 15.5).
Submersible pumps (Fig. 15.6) usually have open impellers
and are frequently used to pump wastewater from wet wells in
lift stations.
15.111	Propeller Pumps
There are two basic types of propeller pumps (Fig. 15.7),
axial-flow and mixed-flow impellers. The axial-flow propeller
pump is one having a flow parallel to the AX/S1 of the impeller
(Fig. 15.8). The mixed-flow propeller pump is one having a flow
that is both AXIAL2 and RADIAL3 to the impeller (Fig. 15.8).
15.112	Vertical Wet Well Pumps
A vertical wet well pump is a vertical shaft, diffuser-type
centrifugal pump with the pumping element suspended from
the discharge piping (Fig. 15.9). The needs of a given installa-
tion determine the length of discharge column. The pumping
bowl assembly may connect directly to the discharge head for
shallow sumps, or may be suspended several hundred feet for
raising water from wells. Vertical turbine pumps are used to
pump water from deep wells, and may be of the SINGLE-
STAGE or MULTI-STAGE TYPE*
15.113	Reciprocating or Piston Pumps
The word "reciprocating" means moving back and forth, so a
reciprocating pump is one that moves sludge by a piston that
moves back and forth. A simple reciprocating pump is shown in
Fig. 15.10. If the piston is pulled to the left, Check Valve A will
be open and sludge will enter the pump and fill the casing.
When the piston reaches the end of its travel to the left and is
pushed back to the right, Check Valve A will close, Check
Valve B will open, and wastewater will be forced out the exit
line.
A piston pump is a positive-displacement pump. Never op-
erate it against a closed discharge valve or the pump, valve,
and/or pipe could be damaged by excessive pressures. Also,
the suction valve should be open when the pump is started.
Otherwise an excessive suction or vacuum could develop and
cause problems.
PISTON

FLOW IN
> FLOW OUT
15.10 Simple reciprocating pump
(See page 284 for pump details)
15.114 Incline Screw Pump
Incline screw pumps (Fig. 15.11) consist of a screw operat-
ing at a constant speed within a housing or trough. When the
screw rotates, it moves the wastewater up the trough to a
discharge point. The screw is supported by two bearings; one
at the top and one at the bottom.
15.115	Progressive Cavity (Screw-Flow) Pumps
(Fig. 15.12)
The operation of a progressive cavity pump is similar to that
of a precision incline screw pump (Fig. 15.11). The progressive
cavity pump consists of a screw-shaped rotor snugly enclosed
in a non-moving STATOR5 or housing (Fig. 15.13). The
threads of the screw-like rotor (commonly manufactured of
chromed steel) make contact along the walls of the stator
(usually made of synthetic rubber). The gaps between the rotor
threads are called "cavities." When wastewater is pumped
through an inlet valve, it enters the cavity. As the rotor turns,
the waste material is moved along until it leaves the conveyor
(rotor) at the discharge end of the pump. The size of the
cavities along the rotor determines the capacity of the pump.
All progressive cavity pumps operate on the basic principle
described above. To further increase capacity, some models
have a shaped inside surface of the stator (housing) with a
similarly shaped rotor. In addition, some models use a rotor
that moves up and down inside the stator as well as turning on
its axis (Fig. 15.12). This allows a further increase in the capac-
ity of the pump.
These pumps are recommended for materials which contain
higher concentrations of suspended solids. They are com-
monly used to pump sludges. Progressive cavity pumps
should NEVER be operated dry (without liquid in the cavities),
nor should they be run against a closed discharge valve.
15.116	Pneumatic Ejectors (Fig. 15.14)
Pneumatic ejectors are used when it is necessary to handle
limited flows. Centrifugal pumps are highly efficient for pump-
ing large flows; however, when scaled down for lower flows,
they tend to plug easily. Unstrained solids will tend to block the
small impeller opening (if less than two inches) of a centrifugal
pump and will quickly reduce the flow. Pneumatic ejectors, on
the other hand, are capable of passing solids up to the size of
the inlet and discharge valves, and there is nothing on the
inside of the ejector-receiver to restrict the flow. The ejector
may be useless, however, if a stick or another object gets stuck
under the inlet or discharge check valve preventing it from
closing.
15.12 Pump Lubrication
Pumps, motors, and drives should be oiled and greased in
strict accordance with the recommendations of the manu-
facturer. Cheap lubricants may often be the most expensive In
the end. Oil should not be put in the housing while the pump
shaft is rotating because the rotary action of the ball bearings
will pick up and retain a considerable amount of oil. When the
unit comes to rest, an overflow of oil around the shaft or out of
the oil cup will result.
1	Axis of impeller. In line with the shaft.
2	Axial to impeller. Material being pumped flows around the impeller or parallel to the shaft.
3	Radial to impeller. Material being pumped flows at right angle to the Impeller or perpendicular to the shaft.
4	Single-stage type pumps have only one impeller while multi-stage type pumps have more than one impeller.
5	Stator. The portion of a machine which contains the stationary (non-moving) parts that surround the moving parts (rotor).

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to
yi
00
o
B)
DEEP
STUFFING	3
(D
BOX	3
§
PACKING
GLAND
SHAFT
SLEEVE
LANTERN RING
DISCHARGE
SHIM ADJUSTMENT TO
COMPENSATE FOR WEAR
HEAVY CAST-IRON
FRAME, VERY RIGID
IMPELLER
MACHINED
CENTERING FIT
DRAIN PLUG
FULL-SIZE PASSAGEWAYS
IN IMPELLER & CASING
HEAVY-DUTY
RADIAL BEARING
HEAVY DUTY
THRUST BEARING
WITH DOUBLE
LOCKNUTS
DISC TYPE
WEARING
RINGS
VENT PLUG
PACKING
FLOW IN
ALLOY-STEEL SHAFT
GROUND TO SIZE
I
Fig. 15.3 Horizontal wastewater pump
(Source: War Department Technical Manual TM5-666)

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Maintenance 259
ALLOY-STEEL SHAFT
GROUND TO SIZE ~
HEAVY CAST-IRON_
FRAME. VERY RIGID
LANTERN RING
_ HEAVY-DUTY
RADIAL BEARING
FLOW OUT
MACHINED
CENTERING
FIT
WEARING RING
DRAIN PLUG
SHIM ADJUSTMENT
TO COMPENSATE -
FOR WEAR
HEAVY-DUTY
THRUST-BEARING
WITH DOUBLE
LOCKNUTS
FULL-SIZE
PASSAGEWAYS
IN IMPELLER
AND CASING
FLOW IN
HAND HOLE
ELBOW WITH
FULL-SIZE
CLEANOUT
RIBBED
CAST-IRON
BASE
PACKING GLAND
DEEP STUFFING BOX
IMPELLER
Fig. 15.4 Vertical ball-bearing type wastewater pump
(Source: War Department Tehnical Manual TM5-666)

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260 Treatment Plants
Closed Radial
(Closed radial impellers are used in wastewater treatment plants.)
Open Radial
Fig. 15.5 Impellers
(Source: Centrifugal Pumps by Karasaik and Carter of Worthington Corporation)

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Maintenance 261
1.	LIFTING HANDLE
2.	JUNCTION CHAMBER WITH WATERTIGHT
CABLE ENTRIES
3.	ANTI-FRICTION BEARINGS
4.	SHAFT
5.	STATOR WITH TEMPERATURE
SENSING THERMISTORS
6.	ROTOR
7.	STATOR HOUSING LEAKAGE SENSOR
8.	BRG. TEMPERATURE THERMISTOR
9.	SHAFT SEAL
10.	OIL CHAMBER
11.	VOLUTE
12.	NON-CLOG IMPELLER
13.	COOLING JACKET
14.	SLIDING BRACKET
15.	AUTOMATIC DISCHARGE
CONNECTION
®L
£p'

Fig. 15.6 Submersible wastewater pump
(Courtesy of Flygt Corporation)

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262 Treatment Plants
MOTOR
SHAFT TUBE
LINE SHAFT
DISCHARGE COLUMN
SHAFT BEARING
PROPELLER SHAFT
TOP BOWL
BOTTOM BEARING
FLOW IN
OILER
*
PROPELLER
DISCHARGE TUBE
FLOW OUT
(See Fig. 15.8 for
propeller details)
!!!!!! ••••••¦•¦ •»¦ ••••!!
j Miiiiiiiaaaaamn,!,,,
tlhiiiiMitaaiiimi,!,,!
Fig. 15.7 Propeller pump
(Source: Unknown)
FLOW IN
SUCTION SCREEN

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Maintenance 263
Mixed Flow
Propeller
Fig. 15.8 Impellers (continued)
(Source: Centrifugal Pumps by Karasslk and Carter of Worthlngton Corporation)

-------
264 Treatment Plants
SHAFT
BEARING BALL
PACKING
GLAND STUD
GREASE
FITTING
FLOOR
PLATE
PACKING
BOX
BRONZE SLEEVE
BEARING
PERFECT
SEAL RING
IMPELLER
LOCK SCREW
DISCHARGE!
CASING
PUMP^
BOWL
ASSEMBLY

—.fffr-
ItWl
PACKING
GLAND
DISCHARGE
INTERMEDIATE
BEARING PLATE
IMPELLER
FLOAT
ROD
•§$ CLEARANCE
Fig. 15.9 Vertical wet well pump
(Courtesy Chicago Pump)
NOTE: Fig. 15.10 is on page 257.
\

(J

FLOAT
SWITCH
Y7&777?,I
NStPT R00 IN 'HIS
direction onl
FLOAT
CAP
FLOAT
ROD
SEAL
HOUSING
SEALS
FLOAT ROD
SEAL ASSEMBLY

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Suction
Gear Reducer-
Top Bearing
Screw
Coupling
Discharge
-Bottom of Trough
. b-t

-Bottom Bearing and Support
Fig. 15.11 Incline screw pump
(Courtesy of FMC Corporation, Environmental Equipment Division)
(D
3
0)
3
O
(D
o>
in

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INLET
STATOR
ROTOR
PACKING
DISCHARGE
PACKING
GLAND
HAND
HOLE
MOUNTING
Fig. 15.12 Progressive cavity (screw-flow) pump
(Permission of Moyno Pump Division, Robbing & Meyer, Inc.)

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Pumping principle
0°

135'
180<

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#1111111)11
Maintenance 267
Fig. 15.13 Pumping principle of a progressive cavity pump
(PcrmMon of ANw*H«r Pump*, Inc.)

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"V
x&A/r	^<7*r/?
YW
CO//T#0L 4/R
SL/PE VALVES
^CMS Z/^y£i-
JfsU///0££-
-xV/e	\
~/?/sr/y.
r/s^rr^ wz y^r
sttrsyi^/e
S
•H
3
s
3
0
3
r*
2
0
3
S»
Fig. 15.14 Pneumatic ejector system
(Courtesy of James Equipment and Manufacturing Company)

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Maintenance 269
15.13 Starting a New Pump
The initial start-up work described in this paragraph should
be done by a competent and trained person, such as a man-
ufacturer's representative, consulting engineer, or an experi-
enced operator. The operator can learn a lot about pumps and
motors by accompanying and helping a competent person put
new equipment into operation.
Before starting a pump, lubricate it according to the lubrica-
tion instructions. Turn the shaft by hand to see that it rotates
freely. Then check to see that the shafts of the pump and motor
are aligned and the flexible coupling adjusted. (Refer to Para-
graph 11, see Section 15.2, "Mechanical Maintenance," page
293.) If the unit is belt driven, sheave (pulley) alignment and
belt adjustment should be checked. (Refer to Paragraph 8.)
Check the electric current characteristics with the motor
characteristics and inspect the wiring. See that thermal units in
the starter are set properly. Turn on the motor just long enough
to see that it turns the pump in the direction indicated by the
rotational arrows marked on the pump. If separate water seal
units or vacuum primer systems are used, these should be
started. Finally, make sure lines are open. Sometimes there is
an exception (see following paragraph) in the case of the dis-
charge valve.
A pump should not be run without first having been primed.
To prime a pump, the pump must be completely filled with
water or wastewater. In some cases, automatic primers are
provided. If they are not, it is necessary to vent the casing.
Most pumps are provided with a valve to accomplish this. Allow
the trapped air to escape until water or wastewater flows from
the vent; then replace the vent cap. In the case of suction-lift
applications, the pump must be filled with water unless a self-
primer is provided. In nearly every case, you may start a pump
with the discharge valve open. Exceptions to this, however, are
where water hammer or velocity disturbances might result, or
where the motor does not have sufficient margin of safety or
power. Sometimes there are no check valves in the discharge
line. In this case (with the exception of positive displacement
pumps) it is necessary to start the pump and then open the
discharge lines. Where there are common discharge headers,
it is essential to start the pump and then open the discharge
valve. A positive displacement pump (reciprocating or piston
types) should never be operated against a closed discharge
line.
After starting the pump, again check to see that the direction
of rotation is correct. Packing-gland boxes (stuffing boxes)
should be observed for slight leakage (approximately 60 drops
per minute), as described in Paragraph 1. Check to see that
the bearings do not overheat from over- or under-lubrication.
The flexible coupling should not be noisy; if it is, the noise may
be caused by mis-alignment or improper clearance or adjust-
ment. Check to be sure pump anchorage is tight. Compare
delivered pump flows and pressures with pump performance
curves. (See Chapter 17, "Basic Arithmetic and Treatment
Plant Problems.") If pump delivery falls below performance
curves, look for obstructions in the pipelines. Inspect piping for
leaks.
15.14 Pump Shutdown
When shutting down a pump for a long period, the motor
disconnect switch should be opened, locked out, and tagged
with reason for tag noted. All valves on the suction, discharge,
and water-seal lines should be shut tightly. Completely drain
the pump by removing the vent and drain plugs. Do not permit
sludge to remain in pumps or piping for any length of time;
there are on record cases in which the gas produced has rup-
tured pipes and sludge pumps.
Inspect the pump and bearings thoroughly so that all neces-
sary servicing may be done during the inactive period. Drain
the bearing housing and then add fresh lubricant. Follow any
additional manufacturer's recommendations.
15.15	Pump-Driving Equipment
Driving equipment used to operate pumps includes electric
motors and internal combustion engines. In rare instances,
pumps are driven with steam turbines, steam engines, air and
hydraulic motors.
In all except the large installations, electric motors are used
almost exclusively, with synchronous and induction types
being the most commonly used. Synchronous motors operate
at constant speeds and are used chiefly in large sizes. Three-
phase, squirrel-cage induction motors are most often used in
treatment plants. These motors require little attention and,
under average operating conditions, the factory lubrication of
the bearing will last approximately one year. (Check with the
manufacturer for average number of operating hours for bear-
ings.) When lubricating motors, remember that too much
grease may cause bearing trouble or damage the winding.
Clean and dry all electrical contacts. Inspect for loose elec-
trical contacts. Make sure that hold-down bolts on motors are
secure. Check voltage while the motor is starting and running.
Examine bearings and couplings.
15.16	Electrical Controls
A variety of electrical equipment is used to control the opera-
tion of wastewater pumps or to protect electric motors. The
simplest type of control unit consists of a counter-weighted
float which triggers a switch. When the float is raised by the
wastewater to a predetermined level, a switch is tripped to start
the pump. When the wastewater level falls to the cutoff level,
the float switch stops the pump. The time required for each
cycle and the length of time between cycles depend on the
pumping rate and the quantity of wastewater flow.
If starters, disconnect switches, and cutouts are used, they
should be installed in accordance with the local regulations
(city and/or county codes) regarding this equipment. In the
case of larger motors, the power company often requires start-
ers which do not overload the power lines.
The electrode-type, bubbler-type, and diaphragm-type water
level control systems are all similar in effect to the float-switch
system. Scum is a problem with most water-level controls that
operate pumps and must be removed on a regular basis.
QUESTIONS
Write your answers in a notebook and then compare your
answers with those on page 322.
15.1 A Where would you find out how to lubricate a pump?
15.1B What problems can develop if too much grease is
used in lubricating a motor?
15.17	Operating Troubles
The following list of operating troubles includes most of the
causes of failure or reduced operating efficiency. The remedy
or cure is either obvious or may be identified from the descrip-
tion of the cause.

-------
270 Treatment Plants
SYMPTOM A - PUMP WILL NOT START
CAUSES:
1.	Blown fuses or tripped circuit breakers due to:
A.	Rating of fuses or circuit breakers not correct
B.	Switch (breakers) contacts corroded or shorted
C.	Terminal connections loose or broken somewhere in
the circuit
D.	Automatic control mechanism not functioning prop-
erly
E.	Motor shorted or burned out
F.	Wiring hookup or service not correct
G.	Switches not set for operation
H.	Contacts of the control relays dirty and arcing
I.	Fuses or thermal units too warm
J. Wiring short-circuited
K. Shaft binding or sticking due to rubbing impeller, tight
packing glands, or clogging of pump
2.	Loose connection, fuse, or thermal unit
SYMPTOM B - REDUCED RATE OF DISCHARGE
CAUSES:
1.	Pump not primed
2.	Mixture of air in the wastewater
3.	Speed of motor too low
4.	Improper wiring
5.	Defective motor
6.	Discharge head too high
7.	Suction lift higher than anticipated
8.	Impeller clogged
9.	Discharge line clogged
10.	Pump rotating in wrong direction
11.	Air leaks in suction line or packing box
12.	Inlet to suction line too high, permitting air to enter
13.	Valves partially or entirely closed
14.	Check valves stuck or clogged
15.	Incorrect impeller adjustment
16.	Impeller damaged or worn
17.	Packing worn or defective
18.	Impeller turning on shaft because of broken key
19.	Flexible coupling broken
20.	Loss of suction during pumping may be caused by leaky
suction line, ineffective water or grease seal
21.	Belts slipping
22.	Worn wearing ring
SYMPTOM C - HIGH POWER REQUIREMENTS
CAUSES:
1.	Speed of rotation too high
2.	Operating heads lower than rating for which pump was
designed, resulting in excess pumping rates
3.	Check valves open, draining long force-main back into
well
4.	Specific gravity or viscosity of liquid pumped too high
5.	Clogged pump
6.	Sheaves on belt drive misaligned or maladjusted
7.	Pump shaft bent
8.	Rotating elements binding
9.	Packing too tight
10.	Wearing rings worn or binding
11.	Impeller rubbing
SYMPTOM D - NOISY PUMP
CAUSES:
1.	Pump not completely primed
2.	Inlet clogged
3.	Inlet not submerged
4.	Pump not lubricated properly
5.	Worn impellers
6.	Strain on pumps caused by unsupported piping fastened
to the pump
7.	Foundation insecure
8.	Mechanical defects in pump
9.	Misalignment of motor and pump where connected by flex-
ible shaft
10. Rags or sticks bound (wrapped) around impeller
QUESTIONS
Write your answers in a notebook and then compare your
answers with those on page 322.
15.1 C What items would you check if a pump will not start?
15.1 D How would you attempt to increase the discharge from
a pump if the flow rate is lower than expected?
15.18 Starting and Stopping Pumps
The operator must determine what treatment processes will
be affected by either starting or stopping a pump. The pump
discharge point must be known and valves either opened or
closed to direct flows as desired by the operator when a pump
is started or stopped.
15.180 Centrifugal Pumps
Figure 15.15 illustrates a typical wet well and pumping sys-
tem. The purpose of each part is explained in Table 15.1. Rpiqje
rules for the operation of centrifugal pumps include the follow-
ing items.

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Maintenance 271
DISCHARGE
VALVE
INLET
PROCESS
VALVES
DISCHARGE
CHECK
VALVE —i
DISCHARGE
GAGE
VOLUTE
BLEED LINE
vV
SUCTION
VALVE
WET
WELL
SUCTION
GAGE
?
\x. & v\ r\\p-.
< * ) . s »'. * A ^ I /.
* ¦' 0:v. oVv «
TO
TREATMENT
PROCESSES
Fig. 15.15 Wet well and pump system

-------
272 Treatment Plants
1.	Do not operate the pump when safety guards are not in-
stalled over or around moving parts.
2.	Do not start a pump that has been locked or tagged out for
maintenance or repairs.
3.	Never run a centrifugal pump when the impeller is dry. Al-
ways be sure the pump is primed.
4.	Never attempt to start a centrifugal pump whose impeller or
shaft is spinning backwards.
5.	Do not operate a centrifugal pump that is vibrating exces-
sively after start-up. Shut unit down and isolate pump from
system by closing the pump suction and discharge valves.
Look for a blockage in the suction line and the pump impel-
ler.
There are several situations in which it may be necessary to
start a CENTRIFUGAL pump against a CLOSED discharge
valve until the pump has picked up its prime and developed a
satisfactory discharge head for that operating system. Once
the pump is primed, slowly open the pump discharge valve
until the pump is fully on line. This procedure is used with
treatment processes or piping systems with vacuums or pres-
sures that cannot be dropped or allowed to fluctuate greatly
while an alternate pump is put on the line.
Most centrifugal pumps used in wastewater treatment plants
are designed so that they can be easily started even if they
haven't been primed. This is accomplished with a positive
static suction head or a low suction lift. On most of these ar-
rangements, the pump will not require priming as long as the
pump and the piping system do not leak. Leaks would allow the
water to drain out of the pump volute. When pumps in waste-
water systems lose their prime, the cause is often a faulty
check valve on the pump discharge line. When the pump
stops, the discharge check valve will not seal (close) properly.
Wastewater previously pumped then flows back through the
check valve, down through the pump, and back into the wet
well. The pump is drained and has lost its prime.
The other danger associated with a faulty check valve is that
if the pump wet well has a high inflow, plus inflow from the
water running back through the pump, the wet well water level
will rise to the elevation set to turn on the pump. If the pump
attempts to start while the pump, motor, and shafting are rotat-
ing in the opposite direction, very serious damage can occur to
the pumping equipment.
About ninety-five percent of the time, the centrifugal pumps
in wastewater treatment plants are ready to operate with suc-
tion and discharge valves open and seal water turned on.
When the automatic start or stop command is received by the
pump from an air or electronic controller, the pump is ready to
respond properly.
When the pumping equipment must be serviced, take it off
the line by locking and tagging out the pump controls until all
service work is completed.
QUESTIONS
Write your answers in a notebook and then compare your
answers with those on page 322.
15.1E Why should a pump that has been locked or tagged
out for maintenance or repairs not be started?
15.1 F Under what conditions might a centrifugal pump be
started against a closed discharge valve?
TABLE 15.1 PURPOSE OF WET WELL AND PUMP
SYSTEM PARTS
Part	Purpose
1.
Inlet
Carries wastewater to wet well.
2.
Wet Well
Stores wastewater tor removal by
pump.
3.
Suction Bell
Guides wastewater into pump suction
pipe and reduces pipe entrance en-
ergy losses.
4.
Suction Valve
Isolates pump and piping from wet
well.
5.
Suction Gage
Indicates suction head or lift on suc-
tion side of pump.
6.
Volute
Collects wastewater discharged by
pump impeller and directs flow to
pump discharge.
7.
Volute Bleed Line
Keeps pump primed for automatic
operation by allowing entrapped
gases (air) to escape from the pump
volute.
8.
Discharge Gage
Indicates discharge head (energy im-
parted to wastewater by pump).
9.
Discharge Valve
Isolates pump from discharge sys-
tem.
10.
Discharge Check Valve
Prevents discharge pipe and treat-
ment process tanks from draining
back through pump and into wet well.
11.
Process Valve
Directs flow.
Stopping Procedures
This section contains a typical sequence of procedures to
follow to stop a centrifugal pump.
1.	Inspect process system affected by pump, start alternate
pump if required, and notify supervisor or log action.
2.	Before stopping the operating pump, check its operation.
This will give an indication of any developing problems,
required adjustments, or problem conditions of the unit!
This procedure only requires a few minutes. Items to be
inspected include:
a.	Pump packing gland
1)	Seal water pressure
2)	Seal leakage (too much, sufficient or too little leak-
age)
3)	Seal leakage drain flowing clear
4)	Mechanical seal leakage (if equipped)
b.	Pump operating pressures
1)	Pump suction (Pressure-Vacuum)
A higher vacuum than normal may indicate a par-
tially plugged or restricted suction line. A lower vac-
uum may indicate a higher wet well level or a worn
pump impeller or wearing rings.
2)	Pump discharge pressure
System pressure is indicated by the pump dis-
charge pressure. Lower than normal discharge
pressures can be caused by:

-------
Maintenance 273
a)	Worn impeller or wearing rings in the pump;
b)	A different point of discharge can change dis-
charge pressure conditions;
c)	A broken discharge pipe can change the dis-
charge head.
NOTE: To determine the maximum head a centrifugal
pump can develop, slowly close the discharge
valve at the pump. Read the pressure gage
between the pump and the discharge valve
when the valve is fully closed. This is the
maximum pressure the pump is capable of
developing. Do not operate the pump longer
than a few minutes with the discharge valve
closed completely because the energy from the
pump is converted to heat and water in the
pump can become hot enough to damage the
pump.
c.	Motor temperature and pump bearing temperature.
If motor or bearings are too hot to touch, further check-
ing is necessary to determine if a problem has devel-
oped or if the temperature is normal. High temperatures
may be measured with a thermometer.
d.	Unusual noises, vibrations, or conditions about the
equipment.
If any of the above items indicate a change from the
pump's previous operating condition, additional service
or maintenance may be required during shutdown.
3. Actuate stop switch for pump motor and lock out switch. If
possible use switch next to equipment so that you may
observe the equipment stop. Observe the following items:
a. Check valve closes and seats.
Valve should not slam shut, or discharge piping will
jump or move in their supports. There should not be
any leakage around the check valve shaft. If check
valve is operated automatically, it should close
smoothly and firmly to the fully closed position.
NOTE: If the pump is not equipped with a check valve,
close discharge valve before stopping pump.
b.	Motor and pump should wind down slowly and not
make sudden stops or noises during shutdown.
c.	After equipment has completely stopped, pump shaft
and motor should not start back-spinning. If back-spin-
ning is observed, close the pump discharge valve
SLOWLY! Repair faulty check or foot valve.
4.	Go to power control panel containing the pump motor start-
ers just shut down and OPEN motor breaker switch, lock
out, and tag.
5.	Return to pump and close:
a.	Discharge valve,
b.	Suction valve,
c.	Seal water supply valve, and
d.	Pump volute bleed line (if so equipped).
6.	If pump is to be left out of service more than two days, drain
pump volute and leave volute empty. Indicate "volute
empty" on lock-out tag.
7.	If required, close and open appropriate valves along piping
system through which pump was discharging.
Starting Procedures
This section contains a typical sequence of procedures to
follow to start a centrifugal pump.
1.	Check motor control panel for lock and tags. Examine tags
to be sure that NO item is preventing start-up of equipment.
2.	Inspect equipment.
a.	Be sure stop switch is locked out at equipment location.
b.	Guards over moving parts must be in place.
c.	Clean-out on pump volute and drain plugs should be
installed and secure.
d.	Valves should be in closed position.
e.	Pump shaft must rotate freely.
f.	Pump motor should be clean and air vents clear.
g.	Pump, motor, and auxiliary equipment lubricant level
must be at proper elevations.
h.	Determine if any special considerations or precautions
are to be taken during start-up.
3.	Follow pump discharge piping route. Be sure all valves are
in the proper position and that the pump flow will discharge
where intended.
4.	Return to motor control panel.
a.	Remove tag.
b.	Remove padlock.
c.	Close motor main breaker.
d.	Place selector switch to manual (if have automatic
equipment).
5.	Return to pump equipment.
a.	Open seal water supply line to packing gland. Be sure
seal water supply pressure is adequate.
b.	Open pump suction valve slowly.

-------
274 Treatment Plants
c.	Bleed air out of top of pump volute in order to prime
pump. Some pumps are equipped with air relief valves
or bleed lines back to the wet well for this purpose.
d.	When pump is primed, slowly open pump discharge
valve and recheck prime of pump. Be sure no air is
escaping from volute.
e.	Unlock stop switch and actuate start switch. Pump
should start.
6.	Inspect equipment.
a.	Motor should come up to speed promptly. If ammeter is
available, test for excessive draw of power (amps) dur-
ing start-up and normal operation.
b.	No unusual noise or vibrations should be observed dur-
ing start-up.
c.	Check valve should be open and no chatter or pulsation
should be observed.
d.	Pump suction and discharge pressure readings should
be within normal operating range for this pump.
e.	Packing gland leakage should be normal.
f.	If a flow meter is on the pump discharge, record pump
output.
7.	If the unit is operating properly, return to the motor control
panel and place the motor mode of operation selector in the
proper operation position (manual-auto-off).
8.	The pump and auxiliary equipment should be inspected
routinely after it has been placed back into service.
QUESTIONS
Write your answers in a notebook and then compare your
answers with those on page 322.
15.1G What should be done before stopping an operating
pump?
15.1H What could cause a pump shaft or motor to spin
backwards?
15.11 Why should the position (open or closed) of all valves
be checked before starting a pump?
15.181 Positive Displacement Pumps
Steps for starting and stopping positive displacement pumps
are outlined in this section. There are two basic differences in
the operation of positive displacement pumps as compared
with centrifugal pumps. Centrifugal pumps (due to their design)
will permit an operator error, but a positive displacement pump
.will not and someone will have to pay for correcting the dam-
ages.
Important rules for operating positive displacement pumps
include:
i.Meveg.N&veg ore bats a po&rive
CEMENT 9m? A&AlNfrT A &U>56 0
VAlA/e, AllV A PUfclAAgfrg VALVE.
2.	Positive displacement pumps are used to pump solids
(sludge) and certain precautions must be taken to prevent
injury or damage. If the valves on both ends of a sludge line
are closed tightly, the line becomes a closed vessel. Gas
from decomposition can build up to a pressure that will
rupture pipes or valves.
3.	Positive displacement pumps also are used to meter and
pump chemicals. Care must be exercised to avoid venting
chemicals to the atmosphere.
4.	Never operate a positive displacement pump when it is dry
or empty, especially the progressive-cavity types that use
rubber stators. A small amount of liquid is needed for lubri-
cation in the pump cavity between the rotor and the stator.
In addition to NEVER closing a discharge valve on an operat-
ing positive displacement pump, the only other difference
(when compared with a centrifugal pump) may be that the
positive displacement pump system may or may not have a
check valve in the discharge piping after the pump. Installation
of a check valve depends upon the designer and the material
being pumped.
Other than the specific differences mentioned in this section,
the starting and stopping procedures for positive displacement
pumps are similar to the procedures for centrifugal pumps.
QUESTIONS
Write your answers in a notebook and then compare your
answers with those on page 322.
15.1 J What is the most important rule regarding the opera-
tion of positive displacement pumps?
15.1 K What could happen if a positive displacement pump is
started against a closed discharge valve?
15.1L Why should both ends of a sludge line never be closed
tight?
, oe
LS46ow i
Of 6 le&oM)
Oft
/KAlWTBMAMCg
Please answer the discussion and review questions before
continuing with Lesson 3.

-------
Maintenance 275
DISCUSSION AND REVIEW QUESTIONS
Chapter 15. MAINTENANCE
(Lesson 2 of 6 Lessons)
Write the answers to these questions in your notebook be-
fore continuing. The problem numbering continues from Les-
son 1.
10.	What should you do if you can't understand the manufac-
turer's instructions?
PICK THE CORRECT WORD:
11.	Cheap lubricants may be the (1) MOST or (2) LEAST ex-
pensive in the end.
12.	Start-up of a new pump should be done by (1) A NEW
OPERATOR or (2) A TRAINED PERSON.
13.	How can you determine if a new pump will turn in the
direction intended?
14.	When shutting down a pump for a long period, what pre-
cautions should be taken with the motor disconnect
switch?
15.	How can you tell if a new pump is delivering design flows
and pressures?
16.	What is a maintenance problem with water-level float con-
trols?
CHAPTER 15. MAINTENANCE
Table of Contents
15.2 MECHANICAL MAINTENANCE
(Lesson 3 of 6 Lessons)
Paragraph	Page
1	Pumps, General (Incl. Packing)	276
2	Reciprocating Pumps, General 	283
3	Propeller Pumps, General	285
4	Progressive Cavity Pumps, General	285
5	Pneumatic Ejectors, General	285
6	Float and Electrode Switches	285
(Lesson 4 of 6 Lessons)
7	Electric motors 	287
8	Belt Drives	290
9	Chain Drives 	290
10	Variable Speed Belt Drives	291
11	Couplings	293
12	Shear Pins	295
(Lesson 5 of 6 Lessons)
13	Gate Valves	296
14	Check Valves 	299
15	Plug Valves	299
16	Sluice Gates 	299
17	Dehumidifiers	308
18	Air-Gap Separation Systems 	308
19	Plant Safety Equipment	308
20	Acknowledgment	308

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276 Treatment Plants
The format of this section differs from the other chapters.
This format was designed specifically to assist you in planning
an effective preventive maintenance program. The table of
contents is outlined on the preceding page, and the para-
graphs are numbered for easy reference when you use the
Equipment Service Cards and Service Record Cards men-
tioned in Section 15.00, page 246.
An entire book could be written on the topics covered in this
section. Step-by-step details for maintaining equipment are not
provided because manufacturers are continually improving
their products and these details could soon be out of date. Vou
are assumed to have some familiarity with the equipment
being discussed. FOR DETAILS CONCERNING A PARTICU-
LAR PIECE OF EQUIPMENT, YOU SHOULD CONTACT THE
MANUFACTURER. This section indicates to you the kinds of
maintenance you should include in your program and how you
could schedule your work. Carefully read the manufacturer's
instructions and be sure you clearly understand the material
before attempting to maintain and repair equipment. If you
have any questions or need any help, do not hesitate to con-
tact the manufacturer or your local representative.
A glossary is not provided in this section because of the
large number of technical words that require familiarization
with the equipment being discussed. The best way to learn the
meaning of these new words is from manufacturers' literature
or from their representatives. Some new words are described
in the lessons where necessary.
Frequency
of
Service
Preventive Maintenance
The following paragraphs list some general preventive main-
tenance services and indicate frequency of performance.
There are many makes and types of equipment and the wide
variation of functions cannot be included; therefore, you will
have to use some judgement as to whether the services and
frequencies will apply to your equipment. If something goes
wrong or breaks in your plant, you may have to disregard your
maintenance schedule and fix the problem now.
NOTE: If you need to shut a unit down, make sure it is also
locked out and tagged property.
cope-
PAVEANS RMLVj \N, weiWUVi M,MOMfWL.Y;
Q, QOACreCtV; ^^MIAHWAUV; A.ANMUAUV
Paragraph 1: Pumps, General
This paragraph lists some general preventive
maintenance services and indicates frequency of
performance. Typical centrifugal pump sections
are shown in Figs. 15.3 and 15.4.
D 1. CHECK WATER-SEAL PACKING GLANDS
FOR LEAKAGE. See that the packing box is
protected with a clear-water supply from an
outside source, make sure that water seal
pressure is at least 5 psi (0.35 kg/sq cm)
greater than maximum pump discharge
pressure. See that there are no CROSS
CONNECTIONS.6 Check packing glands for
leakage during operation. Allow a slight seal
leakage when pumps are running to keep
packing cool and in good condition. The
proper amount of leakage depends on
equipment and operating conditions. Sixty
drops of water per minute is a good rule-of-
thumb. If excessive leakage is found, HAND
TIGHTEN glands' nuts evenly, but not too
tight. After adjusting packing glands, be sure
shaft turns freely by hand. If serious leakage
continues, renew packing, shaft, or shaft
sleeve.
D 2. CHECK GREASE-SEALED PACKING
GLANDS. When grease is used as a pack-
ing gland seal, maintain constant grease
pressure on packing during operation.
When a spring-loaded grease cup is used,
keep it loaded with grease. Force grease
through packing at a rate of about one
ounce (30 gm) per day. When water is used,
adjust seal pressure to 5 psi (0.35 kg/sq cm)
above maximum pump discharge pressure.
Never allow the seal to run dry.
W 3. OPERATE PUMPS ALTERNATELY. If two
or more pumps of the same size are in-
stalled, alternate their use to equalize wear,
keep motor windings dry, and distribute lu-
bricant in bearings.
W 4. INSPECT PUMP ASSEMBLY. Check float
controls noting how they respond to rising
water level. See that unit starts when float
switch makes contact and that pump
empties basin at a normal rate. Apply light oil
to moving parts.
D 5. CHECK MOTOR CONDITION. See Para-
graph 7.
W 6. CLEAN PUMP. FIRST lock out power and
tag switch (Fig. 15.16). Clean-out handholes
are provided on the pump volute. To clean
pump, close all valves, drain pump, remove
handhole cover, and remove all solids. Wear
gloves to protect your hands from sharp ob-
jects.
—			;—L * HrinUnn (notable) water and an unsafe water supply. For example, If you have a pump moving
• Cross Connection. A connection b*Meen drinking (p supply water for the pump seal, a cross connection or mixing between the two
nonpotable water and hook into ^ drinking	wafer.
water systems can occur. This mixing may lead to contaminavon or we w

-------
Maintenance 277
DANGER
MAN
WORKING
ON LINE
DO NOT CLOSE THIS
SWITCH WHILE THIS
TAG IS DISPLAYED
SIGNATURE : 	 .
This is the ONLY person authorized to remove this tag.
INDUSTRIAL INDEMNITY/INDUSTRIAL UNDERWRITERS/
INSURANCE COMPANIES
4E210—R66
NOTE: Tag also should include: TIME OFF	
DATE 	
Fig. 15.16 Typical warning tag
(Source: Industrial Indemnity/Industrial Undarwritera/lnsuranca Coa.)

-------
278 Treatment Plants
Frequency
of
Service
W 7. CHECK PACKING GLAND ASSEMBLY.
Check packing gland, the unit's most
abused and troublesome part. If stuffing box
leaks excessively when gland is pulled up
with mild pressure, remove packing and
examine shaft sleeve carefully. Replace
grooved or scored shaft sleeve because
packing cannot be held in stuffing box with
roughened shaft or shaft sleeve. Replace
the packing a strip at a time, tamping each
strip thoroughly and staggering joints. (See
Fig. 15.17). Position lantern ring (water-seal
ring) properly. If grease sealing is used,
completely fill lantern ring with grease be-
fore putting remaining rings of packing in
place. The type of packing used (Fig. 15.18)
is less important than the manner in which
packing is placed. Never use a continuous
strip of packing. This type of packing wraps
around and scores the shaft sleeve or is
thrown out against outer wall of stuffing box,
allowing wastewater to leak through and
score the shaft. The proper size of packing
should be available in your plant's equip-
ment files. See Fig. 15.19 for illustrated
steps on how to pack a pump.
W 8. CHECK MECHANICAL SEALS. Mechanical
seals usually consist of two sub-assemblies:
(1) a rotating ring assembly, and (2) a sta-
tionary assembly.
Inspect seal for leakage and excessive heat.
If any part of the seal needs replacing, re-
place the entire seal (both sub-assemblies)
with a new seal that has been provided by
the manufacturer. Before installing a new
seal, be sure that there are no chips or
cracks on the carbide sealing surface. Keep
a new mechanical seal clean at all times.
Always be sure that a mechanical seal is
surrounded with water before starting and
running the pump.
Q 9. INSPECT AND LUBRICATE BEARINGS.
Unless otherwise specifically directed for a
particular pump model, drain lubricant and
wash out oil wells and bearing with solvent.
Check sleeve bearings to see that oil rings
turn freely with the shaft. Repair or replace if
defective. Refill with proper lubricant.
Measure bearings and replace those worn
excessively. Generally, allow clearance of
0.002 inch plus 0.001 inch for each inch or
fraction of inch of shaft-journal diameter.
Q 10. CHECK OPERATING TEMPERATURE OF
BEARINGS. Check bearing temperature
with thermometer, not by hand. If antifriction
bearings are running hot, check for over-
lubrication and relieve if necessary. If sleeve
bearings run too hot, check for lack of lubri-
cant. If proper lubrication does not correct
condition, disassemble and inspect bearing.
Check alignment of pump and motor if high
temperatures continue.
S 11. CHECK ALIGNMENT OF PUMP AND
MOTOR. For method of aligning pump and
motor, see Paragraph 11. If misalignment
recurs frequently, inspect entire piping sys-
tem. Unbolt piping at suction and discharge
nozzles to see if it springs away, indicating
strain on casing. Check all piping supports
for soundness and effective support of load.
Vertical pumps usually have flexible shafting
which permits slight angular misalignment;
however, if solid shafting is used, align
exactly. If beams carrying intermediate bear-
ings are too light or are subject to contradic-
tion or expansion, replace beams and
realign intermediate bearings carefully.
S 12. INSPECT AND SERVICE PUMPS.
a.	Remove rotating element of pump and
inspect thoroughly for wear. Order re-
placement parts where necessary.
Check impeller clearance between vo-
lute.
b.	Remove any deposit or scaling. Clean
out water-seal piping.
c.	Determine pump capacity by pumping
into empty tank of known size or by tim-
ing the draining of pit or sump.
Pump Capacity, gpm = Volume, gallons
Time, minutes
or
Pump Capacity, liters _ Volume, liters
sec Time, seconds
See Chapter 17 on "Arithmetic and
Treatment Plant Problems" for a de-
tailed example.
d.	Test pump efficiency. Refer to pump
manufacturer's instructions on how to
collect data and perform calculations.
Or see Chapter 17 on "Arithmetic and
Treatment Plant Problems."
e.	Measure total dynamic suction lift and
discharge head to test pump and pipe
condition. Record figures for compari-
son with later tests.
f.	Inspect foot and check valves, paying
particular attention to check valves,
which can cause water hammer when
pump stops. (See paragraph 14 also.)
Foot valves are used when pumping
fresh water or plant effluent. Wet wells
must be dewatered before foot valves
can be inspected.
g.	Examine wearing rings. Replace seri-
ously worn wearing rings to improve ef-
ficiency. Check wearing ring clearances
which generally should be no more than
0.003 inch per inch of wearing diameter.
CAUTION: To protect rings and cast-
ings, never allow pump to run dry
through lack of proper priming when
starting or loss of suction when operat-
ing.

-------
Maintenance 279
WATER-SEAL SUPPLY
WATER-SEAL RING (LANTERN RING)
PACKING
GLAND
SHAFT
PACKING
Fig. 15.17 Method of packing shaft
(Source: War Department Technical Manual TM5-666)

-------
280 Treatment Plants
Teflon Packing
Graphite Packing
Fig. 15.18 Packing
(Courtesy A. W. Chesterton Co.)

-------
Maintenance 281
I Remove all old packing. Aim pocking
hook at bore of the box to keep from
scratching the shaft. Clean box thor-
oughly so the new packing won't hang up
Indicator
2 Check for bent rod, grooves or shoul-
ders. If the neck bushing clearance
in bottom of box is great, use sttffer
bottom ring or replace the neck bushing
3 Revolve rotary shaft. If the Indicator
runs out over 0.003-in., straighten
shaft, or check bearings, or balance
rotor. Gyrating shaft beats out packing
Right
6 Cutting off rings while packing Is
wrapped around shaft will glv« you
rings with parallel ends. This is very
important if packing is to do ]ob

Wrong
7 If you cut packing while stretched out straight, the ends will be at an angle.
With gap at angle, packing on either side squeezes into top of gap and ring,
cannot close. This brings up the question about gap for expansion. Most packings
need none. Channel-type packing with lead core may need slight gap for expansion
HOW
TO PACK
A PUMP
(Editor's Note: This step-by-step il-
lustration of a basic maintenance
duty was brought to our attention
by Anthony J. Zigment, Director,
Municipal Training Division, De-
partment of Community Affairs.)
Right
n Wrong
¦Woodtn bushings
11 Open ring joint sidewise, especially
'¦ lead-filled and metallic types. This
prevents distorting molded circumfer-
ence—breaking the ring opposite gap
14 Use split wooden bushing. Install
I" first turn of packing, then force
into bottom of box by tightening gland
against bushing. Seat each turn this way
Sectional
Diagonal
Cross expansion
1C Always install cross-expansion packing so plies slope toward the fluid pres-
IV sure from housing. Place sectional rings so slope between inside and outside
ring is toward the pressure. Diagonal rings must also have slope toward the fluid
pressure. Watch these details for bast results when installing new packing In a box
Fig. 15.19 How to pack a pump
(Source: Water Pollution Control Association of Pennsylvania Magazine,
January-February, 1976)

-------
282 Treatment Plants
E
m
R
* »
^ To find the right size of packing to
5 Wind packing, needed for filling stuffing box, snugly around rod (for soma size
shoft held in vise) and cut through each turn while coiled, as shown. If the
install, measure stuffing-box bore and
subtract rod diameter, divide by 2. packing is slightly too large, never flatten with a hammer. Place each turn on
Packing is too critical for guesswork, a clean newspaper and then roll out with pipe as you would with a rolling pin
Shoft
, Neck bushing
8 Install foil-wrapped packing so edges
on inside will face direction of shaft
rotation. This is a must; otherwise, thin
edges flake off, reduce packing life
9 Neck bushing slides into stuffing
box. Quick way to make it is to pour
soft bearing metal into tin can, turn
and bore for sliding fit Into place
1 A Swabbing new metallic packing* with
Iw lubricant supplied by packing maker
is OK. These include foil types, lead-
core, etc. If the rod is oily, don't swab it
L ontern ring.
Cloud .
1Q Stagger joints 180 degrees if only
10 two rings are in stuffing box. Space
at 120 degrees for three rings, or 90
degrees if four rings or more are in set
1 J Install packing so lantern ring lines up with cooling-liquid opening. Also, remem-
I • ber that this ring moves back into box as pocking is compressed. Leave space
for gland to enter as shown. Tighten gland with wrench—back off finger-tight.
Allow the packing to leak until it seats itself, then allow a slight operating leakage.
Hydraulic-packing pointers
First, clean stuffing box, examine ram or rod. Next, measure stuffing-box
depth and packing set—find difference. Place Vfe-in- washers over gland
studs as shown. Lubricate ram and packing set (if for water). If you
can use them, endless rings give about 17% more wear than cut rings.
Place male adapter in bottom, then carefully slide each packing turn
home—don't harm lips. Stagger joints for cut rings. Measure from top
of packing to top of washers, then compare with gland. Never tighten
down new packing set until all air has chance to work out. As packing
wears, remove one set of washers, after more wear, remove other washer.
Fig. 15.19 How to pack a pump (continued)

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Maintenance 283
Frequency
of
Service
A 13. DRAIN PUMP FOR LONG-TERM SHUT-
DOWN. When shutting down pump for a
long period, open motor disconnect switch;
shut all valves on suction, discharge,
water-seal, and priming lines; drain pump
completely by removing vent and drain
plugs. This procedure protects pump
against corrosion, sedimentation, and freez-
ing. Inspect pump and bearings thoroughly
and perform all necessary servicing. Drain
bearing housings and replenish with fresh
oil, purge old grease and replace. When a
pump is out of service, run it monthly to
warm it up and to distribute lubrication so the
packing will not "freeze" to the shaft. Re-
sume periodic checks after pump is put back
in service.
QUESTIONS
Write your answers in a notebook and then compare your
answers with those on page 322.
15.2A What is a cross-connection?
15.2B Is a slight water-seal leakage desirable when a pump
is running? If so, why?
15.2C How would you measure the capacity of a pump?
15.2D Estimate the capacity of a pump (in GPM) if it lowers
the water in a 10-foot wide x 15-foot long wet well 1.7
feet in five minutes.
15.2E What should be done to a pump before it is shut down
for a long time, and why?
Frequency
of
Service
Paragraph 2: Reciprocating Pumps, General
(See Fig. 15.20)
The general procedures in this paragraph
apply to all reciprocating sludge pumps de-
scribed in this section.
W 1. CHECK SHEAR PIN ADJUSTMENT. Set
eccentric by placing shear pin through
proper hole in eccentric flanges to give re-
quired stroke. Tighten the two %- or %-inch
hexagonal nuts on connecting rods just
enough to take spring out of lock washers.
(See Paragraph 12.) When a shear pin fails,
eccentric moves toward neutral position,
preventing damage to the pump. Remove
cause of obstruction and insert new shear
pin. Shear pins fail because of one of three
common causes:
(1)	Solid object lodged under piston
(2)	Clogged discharge line
(3)	Stuck or wedged valve
D 2. CHECK PACKING ADJUSTMENT. Give
special attention to packing adjustment. If
packing is too tight, it reduces efficiency and
scores piston walls. Keep packing just tight
enough to keep sludge from leaking through
gland. Before pump is installed or after it has
been idle for a time, loosen all nuts on pack-
ing gland. Run pump with sludge suction line
closed and valve covers open for a few min-
utes to break in the packing. Turn down
gland nuts no more than necessary to pre-
vent sludge from getting past packing.
Tighten all packing nuts uniformly.
When packing gland bolts cannot be taken
up farther, remove packing. Remove old
packing and thoroughly clean cylinder and
piston walls. Place new packing into cylin-
der, staggering packing-ring joints, and
tamp each ring into place. Break in and ad-
just packing as explained above. When
chevron type packing is used, tighten gland
nuts only finger tight because excessive
pressure ruins packing and scores plunger.
Q 3. CHECK BALL VALVES. When valve balls
are so worn that diameter is 5/s inch (1.5 cm)
smaller than original size, they may jam into
guides in valve chamber. Check size of
valve balls and replace if badly worn.
Q 4. CHECK VALVE-CHAMBER GASKETS.
Valve-chamber gaskets on most pumps
serve as a safety device and blow out under
excessive pressure. Check gaskets and re-
place if necessary. Keep additional gaskets
on hand for replacement.
A 5. CHECK ECCENTRIC ADJUSTMENT. To
take up babbitt bearing, remove brass shims
provided on connecting rod. After removing
shims, operate pump for at least one hour
and check to see that eccentric does not run
hot.
D 6. NOTE UNUSUAL NOISES. Check for
noticeable water hammer when pump is
operating. This noise is most pronounced
when pumping water or very thin sludge; it
decreases or disappears when pumping
heavy sludge. Eliminate noise by opening
the V-t-inch (0.6 cm) petcock on pump body
slightly; this draws in a small amount of air,
keeping discharge air chamber full at all
times.
D 7. CHECK CONTROL VALVE POSITIONS.
Because any plunger pump may be dam-
aged if operated against closed valves in the
pipeline, especially the discharge line, make
all valve setting changes with pump shut
down; otherwise pumps which are installed
to pump from two sources or to deliver to
separate tanks at different times may be
broken if all discharge line valves are closed
simultaneously for a few seconds or dis-
charge valve directly above pump is closed.
W 8. GEAR REDUCER. Check oil level by remov-
ing plug on the side of the gear case. Unit
should not be in operation.
Q 9. CHANGE OIL AND CLEAN MAGNETIC
DRAIN PLUG.
W 10. CONNECTING RODS. Set oilers to dis-
perse two drops per minute.

-------
284 Treatment Plants
sera ?
GREASE
RETAINER
GEAR
MAIN SHAFT
GREASE
RETAINER
V-BELTS
COUNTERSHAFT
PULLEY
MOTOR
PULLEY
r
4	$
ECCENTRIC
PACKING
STUFFING BOX
SUCTION
CHECK BALL
CHAMBER YOKE
CONNECTING
ROD
PLUNGER
PACKING
GLAND
*
AIR
CHAMBER
	
DISCHARGE
CHECK BALL
CHAMBER YOKE
DISCHARGE
VALVE
CHAMBER
DISCHARGE
CHECK BALL
SUCTION
CHECK
BALL
VALVE
SEAT
SUCTION
ELBOW
KLBOW Tom. I
Fig. 15.20 Reciprocating pump
(Courtesy ITT Marlow, a Unit of International Telephone and Telegraph Corp.)

-------
Maintenance 285
Frequency
of
Service
W
D
M
W
W
W
W
D
D
D
S
S
11.	PLUNGER CROSSHEAD. Fill plunger as
required to half cover the wrist pin with oil.
12.	PLUNGER TROUGH. Keep small quantity
of oil in trough to lubricate the plunger.
13.	MAIN SHAFT BEARING. Grease bearings
monthly. Pump should be in operation when
lubricating to avoid excessive pressure on
seals.
14.	CHECK ELECTRIC MOTOR. See Para-
graph 7.
Paragraph 3: Propeller Pumps, General (Fig.
15.7)
1.	CHECK MOTOR CONDITION. See Para-
graphs 7.1 and 7.2.
2.	CHECK PACKING GLAND ASSEMBLY.
See Paragraph 1.7.
3.	INSPECT PUMP ASSEMBLY. See Para-
graph 1.4.
4.	LUBE LINE SHAFT AND DISCHARGE
BOWL BEARING. Maintain oil in oiler at all
times. Adjust feed rate to approximately four
drops per minute.
5.	LUBE SUCTION BOWL BEARING. Lube
through pressure fitting. Usually three or
four strokes of gun are enough.
6.	OPERATE PUMPS ALTERNATELY. See
Paragraph 1.3.
7.	LUBE MOTOR BEARINGS. See Paragraph
7.
Paragraph 4: Progressive Cavity Pumps,
General (Fig. 15.12)
1.	CHECK MOTOR CONDITION. See Para-
graphs 7.1 and 7.2.
2.	CHECK PACKING GLAND ASSEMBLY.
See Paragraph 1.7.
3.	CHECK DISCHARGE PRESSURE. A
higher than normal discharge pressure may
indicate a line blockage or a closed valve
downstream. An abnormally low discharge
pressure can mean reduced rate of dis-
charge.
4.	INSPECT AND LUBRICATE BEARINGS —
GREASE. If possible, remove bearing cover
and visually inspect grease. When greasing,
remove relief plug and cautiously add 5 or 6
strokes of the grease gun. Afterwards, check
bearing temperature with thermometer. If
over 220°F (104°C), remove some grease.
5.	LUBEFLUSH MOTOR BEARINGS. See
Paragraph 7.3
6.	CHECK PUMP OUTPUT. Check how long it
takes to fill a vessel of known volume or
quantity; or check performance against a
meter, if available.
A 7. SCOPE MOTOR BEARINGS. See Para-
graph 7.4.
A 8. SCOPE PUMP BEARINGS. See Paragraph
7.4.
Paragraph 5: Pneumatic Ejectors, General
(Fig. 15.14)
D 1. INSPECT UNIT. Check unit through a com-
plete cycle. Look for air or water leaks. Keep
units clean.
W 2. BLOWDOWN RECEIVERS.
M 3. CHECK VALVES. Keep check valve pack-
ing tight enough to prevent air or water
leaks.
S 4. CLEAN AIR STRAINERS. Isolate air inlet
line to ejector pot. Remove strainer and
clean with water and wire brush ensuring
free strainer openings. In case of different
types of filters, consult particular manufac-
turer's literature.
A 5. CLEAN RECEIVER. After completely isolat-
ing ejector and power to it, remove and
clean electrodes. Open ejector pot inspec-
tion plate and scrape inside walls of the pot.
Clean sight glass tube.
A 6. INSPECT CHECK VALVES. Check opera-
tion by closing discharge valve, and actuat-
ing ejector on "hand" until pressure relief
valve operates continuously for several min-
utes. Non-operation, or intermittent opera-
tion of relief valve in this mode indicates inlet
check valve not holding. Discharge check
valve can be checked by automatic ejection
of pot, followed by locking out controls, clos-
ing inlet and discharge valves, removing top
inspection plate and checking for fluid leak-
ing by the check valve. Some check valves
can be checked by manually operating and
feeling if they seat. At times, gages, located
in strategic locations, can indicate proper or
improper operation. Inspect all check valves
for leakage around packing.
A 7. INSPECT MAIN AIR VALVE. Check packing
nut for lubrication. Check for smooth opera-
tion.
A 8. INSPECT PILOT VALVE. Time the ejection
and check pressure gage for maximum
steady pressure.
Paragraph 6: Float and Electrode Switches
To ensure the best operation of the pump, a
systematic inspection of the water level controls
should be made at least once a week. Check to
see that:
W 1. CHECK CONTROLS. Controls respond to a
rising water level in the wet well.
W 2. START-UP. The unit starts when the float
switch or electrode system makes contact,
and the pump stops at the prescribed level in
the wet well.

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286 Treatment Plants
Frequency
of
Service
W
W
w
w
3.	MOTOR SPEED. The motor speed comes
up quickly and is maintained.
4.	SPARKING. A brush-type motor does not
spark profusely in starting or running.
5.	INTERFERENCE WITH CONTROLS.
Grease and trash are not interfering with
controls. Be sure to remove scum from
water-level float controls.
6.	ADJUSTMENTS. Any necessary adjust-
ments are properly completed.
QUESTIONS
Write your answers in a notebook and then compare your
answers with those on page 322.
15.2F What are some of the common causes of shear pin
failure in reciprocating pumps?
15.2G What may happen when water or a thin sludge is being
pumped by a reciprocating pump?
END OF LESSON 3 OF 6 LESSONS
on
MAINTENANCE
8
Hfc
Please answer the discussion and review questions before
continuing with Lesson 4.
DISCUSSION AND REVIEW QUESTIONS
Chapter 15. MAINTENANCE
(Lesson 3 of 6 Lessons)
Write the answers to these questions in your notebook be-
fore continuing. The problem numbering continues from Les-
son 2.
17.	What would you do if considerable water was leaking from
the water-seal of a pump?
18.	When two or more pumps of the same size are installed,
why should they be operated alternately?
19.	What should be checked if pump bearings are running
hot?
20.	What happens when the packing is too tight on a recip-
rocating pump?
21.	Why should changes in control valves for reciprocating
pumps be adjusted when the pump is shut down?

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Maintenance 287
CHAPTER 15.
(Lesson 4
Frequency
of
Service
Paragraph 7: Electric Motors (Fig. 15.21)
In order to ensure the proper and continuous
function of electric motors, the items listed in this
paragraph must be performed at the designated
intervals. If operational checks indicate a motor
is not functioning properly, these items will have
to be checked to locate the problem.
D 1. CHECK MOTOR CONDITIONS.
a.	Keep motors free from dirt, dust and
moisture.
b.	Keep operating space free from articles
which may obstruct air circulation.
c.	Check for excessive grease leakage
from bearings.
W 2. NOTE ALL UNUSUAL CONDITIONS.
a.	Unusual noises in operation.
b.	Motor failing to start or come to speed
normally, sluggish operation.
c.	Motor or bearings which feel or smell
hot.
d.	Continuous or excessive sparking
commutator or brushes. Blackened
commutator.
e.	Intermittent sparking at brushes.
f.	Fine dust under coupling having rubber
buffers or pins.
g.	Smoke, charred insulation, or solder
whiskers extending from armature.
h.	Excessive humming.
i.	Regular clicking.
j. Rapid knocking.
k. Brush chatter.
I. Vibration.
m. Hot commutator.
A 3. LUBRICATE BEARINGS. (Fig. 15.22)
a. Check grease in ball bearings and re-
plenish when necessary.
Follow instructions below when prepar-
ing bearings for grease.
MAINTENANCE
f 6 Lessons)
b.	Wipe pressure gun fitting, bearing hous-
ing, and relief plug to make sure that no
dirt gets into bearing with grease.
c.	Before using grease gun, always re-
move relief plug from bottom of bearing
to prevent excessive pressure in hous-
ing which might rupture bearing seals.
d.	Use clean screwdriver or similar tool to
remove hardened grease from relief
hole and permit excess grease to run
freely from bearing.
e.	While motor is running, add grease with
hand operated pressure gun until it
flows from relief hole, purging housing of
old grease. If there is no bottom or relief
plug on bearing housing, insert grease
cautiously through upper plug. Usually
four or five strokes of gun are enough. If
bearing is over-lubricated, seal may be
ruptured. If lubricating a running motor is
dangerous, follow above procedure with
motor at a standstill. Lubricating a run-
ning motor is dangerous if you must re-
move protective gear such as guards
over moving parts in order to lubricate
the motor.
f.	Allow motor to run for five minutes or
until all excess grease has drained from
bearing house.
g.	Stop motor and replace relief plug tightly
with wrench.
A 4. USING A STETHOSCOPE,7 CHECK BOTH
BEARINGS. Listen for whines, gratings, or
uneven noises. Listen all around the bearing
and as near as possible to the bearing. Lis-
ten while the motor is being started and shut
off. If unusual noises are heard, pinpoint the
location.
5. IF YOU THINK THE MOTOR is running un-
usually hot, check with a thermometer.
Place the thermometer on the casting near
the bearing, holding it there with putty or
clay.
A 6. DATEOMETER,8 If there is a dateometer on
the motor, after changing the oil in the motor,
loosen the dateometer screw and set to the
corresponding year.
QUESTION
Write your answer in a notebook and then compare your
answer with the one on page 322.
15.2H What are the major items you would include when
checking an electric motor?
7 Stethoscope. An instrument used to magnify sounds and carry them to the ear.
1 Dateometer (day- TOM-ut-ter). A small calendar disc attached to motors and equipment to indicate the year in which the last maintenance
service was performed.

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288 Treatment Plants
DRIP PROOF
ITEM

NO.
PART NAME
1
Wound Stator w/ Frame
2
Rotor Assembly
3
Rotor Core
4
Shaft
5
Bracket
6
Bearing Cap
7
Bearings
8
Seal, Labyrinth
9
Thru BoIts/Caps
10
Seal, Lead Wire
11
Terminal Box
12
Terminal Box Cover
13
Fan
14
Deflector
15
Lifting Lug
TOTALLY ENCLOSED FAN COOLED
ITEM
NO.
PART NAME
1
Wound Stator w/ Frame
2
Rotor Assembly
3
Rotor Core
4
Shaft
5
Brackets
6
Bearings
7
Seal, Labyrinth
8
Thru Bolts/Caps
9
Seal, Lead Wire
10
Terminal Box
11
Terminal Box Cover
12
Fan, Inside
13
Fan, Outside
14
Fan Grill
15
Fan Cover
16
Fan Cover Bolts
17
Lifting Lug
Fig. 15.21 Typical motors
(Courtesy of Sterling Power Systems. Inc.)

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Maintenance 289
ELECTRIC MOTOR
MOTOR LUBRICATION
FILL
LUBE FITTING
©3
1
1	FRONT BEARING BRACKET
2	FRONT AIR DEFLECTOR
3	FAN
4	ROTOR
5	FRONT BEARING
6	END COVER
7	STATOR
8	SCREENS
9	CONDUIT BOX
10	BACK AIR DEFLECTOR
11	BACK BEARING
12	BACK BEARING BRACKET
13	OIL LUBRICATION CAP
Fig. 15.22 Electric motor lubrication

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290 Treatment Plants
Frequency
of
Service
Paragraph 8: Belt Drives
1. GENERAL. Maintaining a proper tension
and alignment of belt drives ensures long life
of belts and sheaves. Incorrect alignment
causes poor operation and excessive belt
wear. Inadequate tension reduces the belt
grip, causes high belt loads, snapping, and
unusual wear.
a.	Cleaning belts. Keep belts and sheaves
clean and free of oil, which causes belts
to deteriorate. To remove oil, take belts
off sheaves and wipe belts and sheaves
with a rag moistened in a non-oil base
solvent. Carbon tetrachloride is NOT
recommended because exposure to its
fumes has many toxic effects on hu-
mans. Carbon tetrachloride also is ab-
sorbed into the skin on contact and its
effects become stronger with each con-
tact.
b.	Installing belts. Before installing belts,
replace worn or damaged sheaves, then
slack off on adjustments. Do not try to
force belts into position. Never use a
screwdriver or similar lever to get belts
onto sheaves. After belts are installed,
adjust tension; recheck tension after
eight hours of operation. (See Table
15.2)
c.	Replacing belts. Replace belts as soon
as they become frayed, worn, or
cracked. NEVER REPLACE ONLY
ONE V-BELT ON A MULTIPLE DRIVE.
Replace the complete set with a set of
matched belts, which can be obtained
from any supplier. All belts in a matched
set are machine-checked to ensure
equal size and tension.
d.	Storing spare belts. Store spare belts in
a cool, dark place. Tag all belts in stor-
age to identify them with the equipment
on which they can be used.
2. V-BELTS. A properly adjusted V-belt has a
slight bow in the slack side when running;
when idle it has an alive springiness when
thumped with the hand. An improperly tight-
ened belt feels dead when thumped.
If the slack side of the drive is less than 45°
from the horizontal, vertical sag at the center
of the span may be adjusted in accordance
with Table 15.2 below:
TABLE 15.2 HORIZONTAL BELT TENSION
Span
(inches)

to
20
50
100
150
200
Vertical
Sag
From
.01
.03
.20
.80
1.80
3.30
(inches)
To
.03
.09
.56
2.30
4.90
8.60
Span
(millimeters)

250
500
1250
2500
3750
5000
Vertical
Sag
From
0.25
0.75
5-00
20.0
45.0
82.5
(millimeters)
To
0.75
2.25
14.50
57.5
122.5
2150
M	a. Check tension. If tightening belt to
proper tension does not correct slipping,
check for overload, oil on belts, or other
possible causes. Never use belt dress-
ing to stop belt slippage. Rubber wear-
ings near the drive are a sign of im-
proper tension, incorrect alignment, or
damaged sheaves.
M	b. Check sheave (pulley) alignment. Lay a
long straight edge or string across out-
side faces of pulley, and allow for differ-
ences in dimensions from center lines of
grooves to outside faces of the pulleys
being aligned. Be especially careful in
aligning drives with more than one
V-belt on a sheave, as misalignment
can cause unequal tension.
Paragraph 9: Chain Drives
1. GENERAL. Chain drives may be designated
for slow, medium, or high speeds.
a.	Slow-speed drives. Because slow-
speed drives are usually enclosed,
adequate lubrication is difficult. Heavy
oil applied to the outside of the chain
seldom reaches the working parts; in
addition, the oil catches dirt and grit and
becomes abrasive. For lubricating and
cleaning methods, see 5 and 6 below.
b.	Medium- and high-speed drives.
Medium-speed drives should be con-
tinuously lubricated with a device similar
to a sightfeed oiler. Highspeed drives
should be completely enclosed in an oil-
tight case and the oil maintained at
proper level.
D 2. CHECK OPERATION. Check general
operating condition during regular tours of
duty.
Q 3. CHECK CHAIN SLACK. The correct amount
of slack is essential to proper operation of
chain drives. Unlike other belts, chain belts
should not be tight around the sprocket;
when chains are tight, working parts carry a
much heavier load than necessary. Too
much slack is also harmful, on long centers
particularly, too much slack causes vibra-
tions and chain whip, reducing life of both
chain and sprocket. A properly installed
chain has a slight sag or looseness on the
return run.
S 4. CHECK ALIGNMENT. If sprockets are not in
line or if shafts are not parallel, excessive
sprocket and chain wear and early chain
failure result. Wear on inside of chain, side
walls, and sides of sprocket teeth are signs
of misalignment. To check alignment, re-
move chain and place a straight edge
against sides of sprocket teeth.
S 5. CLEAN. On enclosed types, flush chain and
enclosure with a petroleum solvent
(kerosene). On exposed types, remove
chain and soak and wash it in solvent. Clean
sprockets, install chain, and adjust tension.

-------
Maintenance 291
Frequency
of
Service
6. CHECK LUBRICATION. Soak exposed-type
chains in oil to restore lubricating film. Re-
move excess lubricant by hanging chains up
to drain.
Do not lubricate underwater chains which
operate in contact with considerable grit. If
water is clean, lubricate by applying water-
proof grease with brush while chain is run-
ning.
Do not lubricate chains on elevators or on
conveyors of feeders which handle dirty or
gritty materials. Dust and grit combine with
lubricants to form a cutting compound which
reduces chain life.
7.	CHANGE OIL. On enclosed types only,
drain oil and refill case to proper level.
8.	INSPECT. Note and correct abnormal condi-
tions before serious damage results. Do not
put a new chain on worn sprockets. Always
replace worn sprockets when replacing a
chain because out-of-pitch sprockets cause
as much chain wear in a few hours as years
of normal operation.
9. TROUBLESHOOTING. Some common
symptoms of improper chain-drive operation
and their remedies follow:
a.	Excessive noise. Correct alignment, if
misaligned. Adjust centers for proper
chain slack. Lubricate in accordance
with aforementioned methods. Be sure
all bolts are tight. If chain or sprockets
are worn, reverse or renew if necessary.
b.	Wear on chain, side walls, and sides of
teeth. Remove chain and correct align-
ment.
c.	Chain climbs sprockets. Check for
poorly fitting sprockets and replace if
necessary. Make sure tightener is in-
stalled on drive chain.
d.	Broken pins and rollers. Check for chain
speed which may be too high for the
pitch, and substitute chain and sprock-
ets with shorter pitch if necessary.
Breakage also may be caused by shock
loads.
e.	Chain clings to sprockets. Check for in-
correct or worn sprockets or heavy,
tacky lubricants. Replace sprockets or
lubricants if necessary.
f.	Chain whip. Check for too-long centers
or high, pulsating loads and correct
cause.
g.	Chains get stiff. Check for misalignment,
improper lubrication, or excessive over-
loads. Make necessary corrections or
adjustments.
Paragraph 10: Variable Speed Belt Drives
(See Fig. 15.23)
D 1. CLEAN DISCS. Remove grease, acid, and
water from disc faces.
D 2. CHECK SPEED-CHANGE MECHANISM.
Shift drive through entire speed range to
make sure shafts and bearings are lubri-
cated and discs move freely in lateral direc-
tion on shafts.
W 3. CHECK V-BELT. Make sure it runs level and
true. If one side rides high, a disc is sticking
on shaft because of insufficient lubrication or
wrong lubricant. In this case, stop the drive
at once, remove V-belt, and clean disc hub
and shaft thoroughly with petroleum solvent
until disc moves freely. Relubricate with soft
ball-bearing grease and replace V-belt in
opposite direction from that in which it for-
merly ran.
M	If drive is not operated for 30 days or more,
shift unit to minimum speed position, placing
spring on variable-speed shaft at minimum
tension and relieving belt of excessive pres-
sure.
4. LUBRICATE DRIVE. Make sure to apply lu-
bricant at all the six force-feed lubrication
fittings (Fig. 15.23: A, B, D, E, G, and H) and
the one cup type fitting (C).
NOTE: If the drive is used with a reducer,
fitting E is not provided.
W	a. Once every ten days to two weeks, use
two or three strokes of a grease gun
through fittings A and B at ends of shift-
ing screw and variable-speed shaft, re-
spectively, to lubricate bearings of mov-
able discs. Then, with unit running, shift
drive from one extreme speed position
to the other to ensure thorough distribu-
tion of lubricant over disc-hub bearings.
Q	b. Add two or three shots of grease
through fittings D and E to lubricate
frame bearing on variable-speed shaft.
Q	c. Every 90 days, add two or three cupfuls
of grease to Cup C which lubricates
thrust bearing on constant-speed shaft.
Q	d. Every 90 days, use two or three strokes
of grease gun through fittings G and H to
lubricate motorframe bearings.
CAUTION: Be sure to follow manufac-
turer's recommendation on type of
grease. After lubricating, wipe excessive
grease from sheaves and belt.
QUESTIONS
Write your answers in a notebook and then compare your
answers with those on page 323.
15.21 How can you tell if a belt on belt-drive equipment has
proper tension and alignment?
15.2J Why should sprockets be replaced when replacing a
chain in a chain-drive unit?

-------
292 Treatment Plants
MOTOR
-V. BELT
MOTOR —*
REDUCER
DISCS
SPEED
CHANGE
MECHANISM
NOTE: A, B, D, E, G, and H are force-feed lubrication
fittings. C is a cup type lubrication fitting.
Fig. 15.23 Reeves varidrive
(Source: War Department Technical Manual TM5-06S)

-------
Maintenance 293
Frequency
of
Service
Paragraph 11: Couplings
1.	GENERAL Unless couplings between the
driving and driven elements of a pump or
any other piece of equipment are kept in
proper alignment, breaking and excessive
wear results in either or both the driven ma-
chinery and the driver. Burned-out bearings,
sprung or broken shaft, and excessively
worn or ruined gears are some of the dam-
ages caused by misalignment. To prevent
outages and the expense of installing re-
placement parts, check the alignment of all
equipment before damage occurs.
a.	Improper original installation of the
equipment may not necessarily be the
cause of the trouble. Settling of founda-
tions, heavy floor loadings, warping of
bases, excessive bearing wear, and
many other factors cause misalignment.
A rigid base is not always security
against misalignment. The base may
have been mounted off level, which
could cause it to warp.
b.	Flexible couplings permit easy assem-
bly of equipment, but they must be
aligned as exactly as flanged couplings
if maintenance and repair are to be kept
to a minimum. Rubber-bushed types
cannot function properly if the bolts can-
not move in their bushings.
2.	CHECK COUPLING ALIGNMENT (straight
edge method). Excessive bearing and motor
temperatures caused by overload, notice-
able vibration, or unusual noises may all be
warnings of misalignment. Realign when
necessary (Fig. 15.24) using a straight edge
and thickness gage or wedge. To ensure
satisfactory operation, level up to within
0.005 inch (0.13 mm) as follows:
a.	Remove coupling pins.
b.	Rigidly tighten driven equipment; slightly
tighten bolts holding drive.
c.	To correct horizontal and vertical mis-
alignment, shift or shim drive to bring
coupling halves into position so no light
can be seen under a straight edge laid
across them. Place straight edge in four
positions, holding a light in back of
straight edge to help ensure accuracy.
d.	Check for angular misalignment with a
thickness or feeler gage inserted at four
places to make certain space between
coupling halves is equal.
e.	If proper alignment has been secured,
coupling pins can be put in place easily
using only finger pressure. Never ham-
mer pins into place.
f.	If equipment is still out of alignment, re-
peat the procedure.
3.	CHECK COUPLING ALIGNMENT (dial indi-
cator method). Dial indicators also are used
to measure coupling alignment. This method
produces better results than the straight
edge method. The dial indicates very small
movements or distances which are meas-
ured in mils (one mil equals 1/1000 of an
inch). The indicator consists of a dial with a
graduated face (with "plus" and "minus"
readings, a pedestal, and a rigid indicator
bar (or "fixture") as shown in Figure 15.25.
The dial indicator is attached to one coupling
via the fixture and adjusted to the zero posi-
tion or reading. When the shaft of the ma-
chine is rotated, misalignment will cause the
pedestal to compress (a "plus" reading), or
extend (a "minus" reading). Literature pro-
vided by the manufacturer of machinery
usually will indicate maximum allowable tol-
erances or movement.
Carefully study the manufacturer's literature
provided with your dial indicator before at-
tempting to use the device.
4.	CHANGE OIL IN FAST COUPLINGS. Drain
out old oil and add gear to proper level. Cor-
rect quantity is given on instruction card
supplied with each coupling.
STRAIGHT EDGE
—EL
PARALLEL MISALIGNMENT
FEELER GAGE -
ANGULAR MISALIGNMENT
-EE
JH
STRAIGHT EDGE
]
	FEELER GAGE
PERFECT ALIGNMENT
Fig. 15.24 Testing alignment, straight edge
(Source: Unknown)

-------
294 Treatment Plants
DIAL
25
25 	25
25
25	 25,
PEDESTAL
50
50
50
DIAL
INDICATORS
25 MILS	25 MILS
INDICATOR BAR
(FIXTURE)
REVERSE
DIALING
PARALLEL
MISALIGNMENT
ILLUSTRATION INDICATES
A TOTAL OFFSET OF
40 MILS (20 MILS + 20 MILS)
20 MILS
L_
20 MILS
Fig. 15.25 Use of a dial indicator
(Permission of DYMAC, a Division of Spectral Dynamics Coiporation)

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Maintenance 295
Frequency
of
Service
Paragraph 12: Shear Pins
Many wastewater treatment units use shear pins
as protective devices to prevent damage in case
of sudden overloads. To serve this purpose,
these devices must be in operational condition at
all times. Under some operating conditions,
shearing surfaces of a shear pin device may
freeze together so solidly that an overload fails to
break them.
Manufacturers' drawings for particular in-
stallations usually specify shear pin material and
size. If this information is not available, obtain the
information from the manufacturer, giving the
model, serial number, and load conditions of unit.
When necessary to determine shear pin size,
select the lowest strength which does not break
under the unit's usual loads. When proper size is
determined, never use a pin of greater strength,
such as a bolt or a nail.
If necked pins are used, be sure the necked-
down portion is properly positioned with respect
to shearing surfaces. When a shear pin breaks,
determine and remedy the cause of failure be-
fore inserting new pin and starting drive in opera-
tion.
M 1. GREASE SHEARING SURFACES.
Q 2. REMOVE SHEAR PIN. Operate motor for a
short time to smooth out any corroded spots.
A 3. CHECK SPARE INVENTORY. Make sure
an adequate supply is on hand, properly
identified and with record of proper pin size,
necked diameter, and longitudinal dimen-
sions.
QUESTIONS
Write your answers in a notebook and then compare your
answers with those on page 323.
15.2K What factors could cause couplings to become out of
alignment?
15.2L What is the purpose of shear pins?

Tmsenak
Please answer the discussion and review questions before
continuing with Lesson 5.
DISCUSSION AND REVIEW QUESTIONS
Chapter 15. MAINTENANCE
(Lesson 4 of 6 Lessons)
Write the answers to these questions in your notebook be-
fore continuing. The problem numbering continues from Les-
son 3.
22.	Why would you use a stethoscope to check an electric
motor?
23.	How would you determine if a motor is running unusually
hot?
24.	How would you clean belts on a belt drive?
25.	Why should you never replace only one belt on a
multiple-drive unit?
26.	What do rubber wearings near a belt drive indicate?
27.	How can you determine if a chain in a chain-drive unit has
the proper slack?
28.	What happens when couplings are not in proper align-
ment?

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296 Treatment Plants
CHAPTER 15. MAINTENANCE
(Lesson 5 of 6 Lessons)
Frequency
of
Service
Frequency
of
Service
S
A
Paragraph 13: Gate Valves (Figures 15.26 and
15.27)
The most common maintenance required by
gate valves is oiling, tightening, or replacing the
stem stuffing box packing.
1.	REPLACE PACKING. Modern gate valves
can be repacked without removing them
from service. Before repacking, open valve
wide. This prevents excessive leakage when
the packing or the entire stuffing box is re-
moved. It draws the stem-collar tightly
against the bonnet on a non-rising stem
valve, and tightly against the bonnet bushing
on a rising stem valve.
a.	Stuffing box. Remove all old packing
from stuffing box with a packing hook or
a rattail file with bent end. Clean valve
stem of all adhering particles and polish
it with fine emery cloth. After polishing
remove the fine grit with a clean cloth to
which a few drops of oil have been add-
ed.
b.	Insert packing. Insert new split-ring
packing in stuffing box and tamp it into
place with packing gland. Stagger ring
splits. After stuffing box is filled, place a
few drops of oil on stem, assembly
gland, and tighten it down on packing.
2.	OPERATE VALVE. Operate inactive gate
valves to prevent sticking.
3.	LUBRICATE GEARING. Lubricate gate
valves as recommended by manufacturer.
Lubricate thoroughly any gearing in large
gate valves. Wash open gears with solvent
and lubricate with grease.
4.	LUBRICATE RISING-STEM THREADS.
Clean threads on rising-stem gate valves
and lubricate with grease.
5.	LUBRICATE BURIED VALVES. If a buried
valve works hard, lubricate it by pouring oil
down through a pipe which is bent at the end
to permit oiling the packing follower below
the valve nut.
6.	REFACE LEAKY GATE VALVE SEATS. If
gate valve seats leak, re face them im-
mediately, using the method discussed be-
low. A solid wedge disc valve is used for
illustration, but the general method also
applies to other types of reparable gate
valves. Proceed as follows:
a.	Remove bonnet and clean and examine
disc and body thoroughly. Carefully de-
termine extent of damage to body rings
and disc. If corrosion has caused ex-
cessive pitting or eating away of metal,
as in guide ribs in body, repairs may be
impractical.
b.	Check and service all parts of valve
completely. Remove stem from bonnet
and examine it for scoring and pitting
where packing makes contact. Polish
lightly with fine emery cloth to put stem
in good condition. Use soft jaws if stem
is put in vise.
c.	Remove all old packing and clean out
stuffing box. Clean all dirt, scale, and
corrosion from inside of valve bonnet
and other parts.
d.	Do not salvage an old gasket. Remove it
completely and replace with one of
proper quality and size.
e.	After cleaning and examining all parts,
determine whether valve can be re-
paired by removing cuts from disc and
body seat faces or by replacement of
body seats. If repair can be made, set
disc in vise with face leveled, wrap fine
emery cloth around a flat tool, and rub or
lap off entire bearing surface on both
sides to a smooth, even finish. Remove
as little metal as possible.
f.	Repair cuts and scratches on body
rings, lapping with an emery block small
enough to permit convenient rubbing all
around rings. Work carefully to avoid
removing so much metal that disc will
seat too low. When seating surfaces of
disc and seat rings are properly lapped
in, coat faces of disc with PRUSSIAN
BLUE9 and drop disc in body to check
contact. When good, continuous con-
tact is obtained, the valve is tight and
ready for assembly. Insert stem in bon-
net, install new packing, assemble other
parts, attach disc to stem, and place as-
sembly in body. Raise disc to prevent
contact with seats so bonnet can be
properly seated on body before tighten-
ing the joint.
g.	Test repaired valve before putting it
back in line to ensure that repairs have
been properly made.
9 Prussian Blue. A paste or liquid used to show a contact area.

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Maintenance 297
125-Pound Ferrosteel Wedge Gate Valves
Names of Parts
STEM COLLAR
GASKET
yoke sleeve nut
yoke sleeve
gland flange
packing
stuffing box
bushings
disc bushing
bonnet bushing
0
0
bonnet
stem
disc face
body seat rings
guide ribs
Outside Screw and
Non-Rising Stem Valve	Yoke Valve
Bronze Trimmed — Open	Bronze Trimmed Closed
Those illustration* are representative of sizes 12-inch and smaller only
Fig. 15.26 Wedge Gate Valve
(Source: Crane Co.)

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298 Treatment Plants
Cutaway
View of
Typical
Kennedy
A.W.W.A.
Non-Rising Stem
Iron Body
Bronze Mounted
Gate Valve
OPERATING NUT
Cast Iron
STUFFING BOX
"0" RING
STUFFING BOX
BONNET
PIPE PLUG
THROAT FLANGE
STEM
STEM NUT
DISC RINGS
SEAT RINGS
DISCS
WEDGE PIN
BODY
Fig. 15.27 Non-rising stem gate valve
(Permission of Kennedy Valve, Division of ITT Grinnell Valve Co., Inc.)

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Maintenance 299
Frequency
of
Service
Frequency
of
Service
h. If leaky gate valve seats cannot be re-
faced, remove and replace seat rings
with a power lathe. Chuck up body with
rings vertical to lathe and use a strong
steei bar across ring lugs to unscrew
them. They can be removed by hand
with a diamond point chisel if care is
taken to avoid damaging threads. Drive
new rings home tightly. Use a wrench on
a steel bar across lugs when putting in
rings by hand. Always coat threads with
a good lubricant before putting threads
into the valve body. This helps to make
the threads easier to remove the next
time the seats have to be replaced. Lap
in rings to fit disc perfectly.
Paragraph 14: Check Valves (Fig. 15.28)
A 1. INSPECT DISC FACING. Open valves to
observe condition of facing on swing check
valves equipped with leather or rubber seats
on disc. If metal seat ring is scarred, dress it
with a fine file and lap with fine emery paper
wrapped around a flat tool.
A 2. CHECK PIN WEAR. Check pin wear on bal-
anced disc check valve, since disc must be
accurately positioned in seat to prevent
leakage.
Paragraph 15: Plug Valves (Figs. 15.29,15.30,
15.31, 15.32 & 15.33)
M 1. ADJUST GLAND. The adjustable gland
holds the plug against its seats in body and
acts through compressible packing which
functions as a thrust cushion. Keep gland
tight enough at all times to hold plug in con-
tact with its seat. If this is not done, the lubri-
cant system cannot function properly; and
solid particles may enter between the body
and plug and cause damage.
M 2. LUBRICATE ALL VALVES. Apply lubricant
by removing lubricant screw and inserting
stick of plug valve lubricant for stated tem-
perature conditions. The check valve fitting
within the shank prevents line pressure from
blowing out when lubricant screw is re-
moved. Inject lubricant into valve by turning
screw down to keep valve in proper operat-
ing condition. If lubrication has been ne-
glected, several sticks of lubricant may be
needed before lubricant system is refilled to
operating condition. Be sure to lubricate
valves which are not used often to ensure
that they are always in operating condition.
Leave lubricant chamber nearly full so extra
supply is available by turning screw down.
Use lubricant regularly to increase valve ef-
ficiency and service, promote easy opera-
tion, reduce wear and corrosion, and seal
valve against internal leakage.
Paragraph 16: Sluice Gates (Fig. 15.34)
There are two general types of light duty sluice
gates: those which seat with the pressure, and
those which seat against the pressure. Both are
maintained similarly. Heavy-duty sluice gates
(Fig. 15.34) can seat under seating and unseat-
ing pressure.
M 1. TEST FOR PROPER OPERATION. Oper-
ate inactive sluice gates. Oil or grease stem
threads.
A 2. CLEAN AND PAINT. Clean sluice gate with
wire brush and paint with proper corrosion-
resistant paint.
A 3. ADJUST FOR PROPER CLEARANCE. For
gates seating against pressure, check and
adjust top, bottom, and side wedges until in
closed position each wedge applies nearly
uniform pressure against gate. (Fig. 15.35)
QUESTION
Write your answer in a notebook and then compare your
answer with the one on page 323.
15.2M What maintenance is required by;
a.	Gate valves?
b.	Sluice gates?

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300 Treatment Plants
CHECK VALVES
LEATHER DISK
FACING
DISK
Fig. 15.28 Check valves
(Source: Crane Co.)

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Maintenance 301
BONNET i
PS-GEAR
OPERATED
STEM SEAL
PLUG
Fig. 15.29 Eccentric plug valve
(Permlaakwi of DeZurlk, ¦ Unit ol General Signal)

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302 Treatment Plants
FRICTION
—HANDLE
ASSEMBLY
Fig. 15.30 Plug valve, lever operated
(Permission of DeZurik, a Unit of General Signal)

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Maintenance 303
Plug Valve
PLUG-—
TENSION
ADJUSTMENT
-LEVER
OPERATED
STEM SEAL
BONNET
BODY
PLUG

Fig. 15.31 Plug valve, lever operated
(Permission of DeZurik, a Unit of General Signal)

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304 Treatment Plants
PI u g Valve
GEAR
OPERATED
Fig. 15.32 Plug valve, gear operated
(Permission of DeZurik, a Unit of General Signal)

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Maintenance 305
PLUG
RESILIENT PACKING
WRENCH SQUARE
BODY
LUBRICANT CHECK VALVE
LUBRICANT SCREW
BOLTED PACKING
GLAND
METAL PACKING RING
LUBRICANT CHAMBER
FACING
PLUG
FORGED STEEL COVER
SHANK
GASKET AND STAINLESS
STEEL SEALING
DIAPHRAGM
PACKING GLAND NUT
LUBRICANT SEALING
GROOVES
CAP SCREW OR
COVER NUT
Fig. 15.33 Plug valve
(Source: War Department Technical Manual TM5-666)

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306 Treatment Plants
Fig. 15.34 Heavy-duty sluice gate
(Permission of ARMCO)

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Cap Screws
(Solid Bronze or
•Stainless Steel)
(SST)
Wedqe Block
Adjusting Bolt
Wedge (Solid Bronze
or Stainless
Steel)
Bronze or SST
Seating Faces
Gate
Slide
(Cast Iron)
Fig. 15.35 Adjustment of sluice gate side wedges	®
M
(Permission of ARMCO)	jj>
O
O
u
o

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308 Treatment Plants
Frequency
of
Service
Paragraph 17: Dehumidifiers
The job of the dehumidifier is to remove mois-
ture from the surrounding atmosphere. Moisture
can accumulate in locations that are below grade
since the surrounding air temperature will remain
relatively constant. This is especially true of
pump stations. In the summertime warm, humid
air will enter the pump stations and, unless the
air is dehumidified, moisture will form on pump
controls, circuits, and other essential equipment.
This moisture will cause malfunctions if allowed
to exist, due to corrosion and oxidation.
D Check dehumidifier performance by noting con-
densation on the walls of the station. If conden-
sation continues, set the dehumidifier to a dryer
setting. Inspect dehumidifier coils. If frost is on
coils, turn unit off until it defrosts.
S To lube dehumidifier, disassemble the unit and
clean it thoroughly, including the drip pan and
drain hose. Lube the fan with a few drops of oil.
After the unit is reassembled and installed, check
condensation buildup daily.
Q Be sure that the drain remains clear, since build-
up of water will make the unit operate less effi-
ciently.
Paragraph 18: Air-Gap Separation System
An air-gap separation system provides a phys-
ical break between the wastewater treatment
plant's municipal or fresh water supply (well) and
the plant's treatment process systems. The pur-
pose of this system is to protect the potable
(drinking) water supply in case wastewater backs
up from a treatment process. For example,
wastewater could travel back through a pump
seal and cause contamination of a drinking water
system.
A Installation of air-gap systems is controlled by
health regulations and periodically should be in-
spected by the local health department or the
public water supply agency.
W Precautions must be taken to ensure that the
air-gap separation from the discharge of the
water supply pipe is at least two pipe diameters
above the rim of the air-gap tank (see Figure
15.36). This separation prevents water from
being sucked back down into the main water
supply line under any circumstances because
the water can never reach the elevation of the
discharge pipe above the rim of the tank. Wind
guards may be necessary around the rim to pre-
vent water loss or damage by wind spray. The
device must be easily accessible for weekly in-
spections.
Frequency
of
Service
An examination of Figure 15.36 shows how the
plant receives its water supply in the receiving
tank. If a plant power outage or other occurrence
causes negative pressures in the plant water
lines, it would be physically impossible for any
contaminated water to enter the drinking water
system.
Preventive maintenance should include the fol-
lowing regularly scheduled items:
D 1. Pump and motor maintenance,
W 2. Servicing of float and control valve, and
A 3. Periodic draining and cleaning of air-gap
tank.
W Routine operational inspections should be con-
ducted at least once a week.
Paragraph 19: Plant Safety Equipment
After 1. AIR BLOWERS (for ventilation of confined
use	spaces). Examine carefully each time used,
or	Inspect hose carefully. If used infrequently,
W	check weekly.
After 2. SAFETY HARNESS. Examine carefully
use	each time used. Inspect stitching and rings,
or
W
W 3. PROTECTIVE CLOTHING. Inspect for rips
or holes.
W 4. GAS DETECTORS (PORTABLE). Ensure
battery is charged. Calibrate using known
standard gas concentrations obtained from
detector manufacturer.
M 5. FIRST AID KITS. Inventory contents. Re-
place contents whenever used or contents
discovered missing during inventory.
M 6. FIRE EXTINGUISHERS. Inspect and inven-
tory. Check carbon dioxide extinguishers
using a pressure gage. Chemical extin-
guishers are checked by recording weight,
comparing weight with original weight, and
inspecting pins.
Paragraph 20: Acknowledgment
Major portions and basic concepts in this sec-
tion on mechanical maintenance are from the
War Department Technical Manual, TM5-666,
"Inspections and Preventive Maintenance Serv-
ices, Sewage Treatment Plants and Sewer Sys-
tems at Fixed Installations," War Department,
September 1945.

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METER
r
AIR-GAP
WATER
RECEIVING
TANK
FLOAT
VALVE



n
TO PLANT
WATER SUPPLY - NO
CONNECTORS OR TEES
BETWEEN METER AND
TANK ON THIS LINE
WATER MAIN OR WELL
o
3
fit
3
O

-------
310 Treatment Plants
QUESTIONS
Write your answers in a notebook and then compare your
answers with those on page 323.
15.2N What is the job of the dehumidifier?
15.20 What happens if the dehumidifier does not do its job?
15.2P What is the purpose of an air-gap separation system?
15.2Q How would you maintain a portable gas detector?
Please answer the discussion and review questions before
continuing with Lesson 6.
fcUP Of UAhOtt h OF 6
DISCUSSION AND REVIEW QUESTIONS
Chapter 15. MAINTENANCE
(Lesson 5 of 6 Lessons)
Write the answers to these questions in your notebook be- 30. Why should plug valves which are not used very often be
fore continuing. The problem numbering continues from Les-	lubricated regularly?
son 4.
31.	Why is regular maintenance of plant safety equipment
29. Why should inactive gate valves be operated periodically?	necessary?

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Maintenance 311
CHAPTER 15.
(Lesson 6
15.3 UNPLUGGING PIPES, PUMPS AND VALVES
15.30	Plugged Pipelines
Plugged pipelines are encountered in lines transporting
scum, raw sludge, digested sludge, or grit. The frequency of a
particular line plugging depends on the type of material pass-
ing through the line, the construction material of the line, the
type of pumps or system used to move the material, and the
routine maintenance performed on the line. This section out-
lines the preventive maintenance measures to reduce plugging
problems in the different lines in a wastewater treatment plant
and the methods of unplugging pipes, pumps, and valves.
15.31	Scum Lines
Scum will cause more problems in pipelines than any other
substance pumped in a wastewater treatment plant. Problems
are more frequent and more severe in colder weather when
grease tends to harden quickly.
r^Tf
Preventive maintenance includes:
1.	Hose down scum troughs, hoppers, and flush lines to scum
box at least every two hours when an operator is on duty
and problems are occurring.
2.	Clean lines monthly using:
a.	Rods equipped with cutters
b.	High-pressure hydraulic pipe cleaning units
c.	Steam cleaning units
d.	Chemicals such as "Sanfax" or "Hot Rod" (strong hy-
droxides). This method is least desirable because of
costs and the possibility that the chemicals could be
harmful to biological treatment processes.
15.32 Sludge Lines
Sludge lines will plug more often when scum and raw sludge
are pumped through the same line, or when storm waters carry
in grit and silt that are not effectively removed by the grit re-
moval facilities.
Preventive maintenance includes:
1.	Flush lines monthly with plant effluent or wastewater.
2.	If possible, recirculate warm digested sludge for an hour
through the line each week if grease tends to build up on
pipe walls.
3.	Rod or high pressure clean lines monthly or quarterly, de-
pending on severity of problem.
4.	If possible, force cleaning tool (pig) through line using pres-
sures produced by pump. Line must be equipped with
valves and wyes to insert and remove pig. Pumps must be
located to allow pig to be forced through the line. A plastic
bag full of ice cubes makes an excellent cleaning tool or pig.
MAINTENANCE
f 6 Lessons)
Force the bag down the line with hot water. If the line plugs,
the ice will melt to the point where the bag will continue
down the line.
15.33	Digested Sludge Lines
Problems develop in digested sludge lines of small plants
from infrequent use, ineffective grit removal, and failure to re-
move sludge from the line after withdrawing sludge to a drying
bed.
Preventive maintenance includes checking:
1.	Condition of pipeline for wear or obstructions, such as
sticks and rags.
2.	Pump impellers for wear. A worn impeller will not maintain
desired velocity and pressure in the line.
15.34	Unplugging Pipelines
Selection of a method to unplug a pipe depends on the
location of the blockage and access to the plugged line. Pres-
sure methods and cutting tools are the most common tech-
niques used to clear stopped lines.
15.340 Pressure Methods
REQUIREMENTS:
1.	Must be able to valve off or plug one end of pipeline in order
to move obstruction or blockage down the line and out other
end to a free discharge.
2.	Pressure may be developed using water or air pressure.
Maximum available pressures are usually less than 80 psi
(5.6 kg/sq cm).
3.	Pipeline must have tap and control valves to control applied
water or air pressure.
PRECAUTIONS:
1.	Never use water connected to a domestic water supply
because you may contaminate the water supply.
2.	Do not exceed pipeline design pressures, usually 125 psi
(8.8 kg/sq cm).
3.	Never attempt to use a positive displacement pump by
over-riding the safety cut-out pressure switches. This prac-
tice may damage the pump.
PROCEDURE:
1.	Plug or valve off one end of pipe, but leave other end open.
For example, (1) close valve to digester but open line to the
drying beds, or a raw sludge line, or (2) close suction valve
on raw sludge pump, and open pipe back to primary clarifier
hopper.
2.	Connect hose from pressure supply to tap and valve on
pipeline as close as possible to the plugged or valved-off
end.
3.	Apply pressure to supply hose and then slowly open control
tap valve and allow pressure to build up until obstruction is
moved.

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312 Treatment Plants
DO NOT EXCEED PIPELINE WORKING DESIGN PRES-
SURE.
15.341	Cutting Tools
Cutting tools are usually available from sewer maintenance
crews and may consist of hand rods, power rods, or snakes
which are capable of cutting or breaking up material causing a
stoppage.
REQUIREMENTS:
1.	One end of the line must be open and reasonably accessi-
ble.
2.	Cutting tools should be able to remove material causing
stoppage when line is cleared.
LIMITATIONS:
1.	Most of these units cannot clean lines with sharp bends or
pass through some of the common types of plug valves
used in sludge lines.
2.	A 4-inch cutter tool may have to be used on a 6-inch line
due to 90-degree bends.
3.	A part of the line may have to be dismantled to use a cutting
tool.
4.	Rods are difficult to hand push over 300 feet (90 m). The
operator must have firm footing and room to work.
HAND RODS:
1.	Use sufficient sections to clean full length of line.
2.	Insert cutter in the open end of the pipeline and twist rods
as they are pushed up the line.
3.	If rods start to twist up due to torque, pull back and let rod
unwind.
POWER RODS:
1.	Power drive unit must be located over plugged line. Don't
attempt to run 40 feet (12 m) across a clarifier and then into
sludge line.
2.	Don't run rods into line too fast. You may hit an obstruction
or valve and break the cutter off of the rods. They will be
very difficult to recover.
15.342	High Velocity Pressure Units
This unit is very good for removing grease, sludge, or grit
from pipelines.
PROCEDURE:
1. Insert nozzle and hose 3 feet (1 m) into line.
2.	Increase pressure in cleaning system to 600 to 1000 psi (42
to 70 kg/sq cm) and slowly unreel the hose into the pipeline.
3.	Keep track of how much hose is in the line in order to
prevent the nozzle from attempting to go through an open
valve. The nozzle and hose may catch on the valve and
require taking apart the valve to free the nozzle.
4.	Run water through nozzle while reeling in hose.
15.343 Last Resort
If the methods described in this section fail, the only solution
is to attempt to locate the position of the stoppage, drain the
line, take apart the plugged section of pipe, and remove the
obstruction.
15.35 Plugged Pumps and Valves
Isolate plugged pump or valve from the remainder of treat-
ment plant by valving-off plugged section and locking-out
power supply to pump. Remove pump inspection plate or dis-
mantle valve and remove material causing blockage. When
removing pump inspection plate, loosen bolts and allow to
drain BEFORE removing bolts in case all pipes have not been
properly valved-off. Exercise caution when removing materials
to avoid damaging the pump or valve.
QUESTIONS
Write your answers in a notebook and then compare your
answers with those on page 323.
15.3A What methods are available for clearing plugged
pipelines?
15.3B How would you clear a plugged pump?
15.4 FLOW MEASUREMENTS - METERS AND
MAINTENANCE
(Also see Chapter 26, "Instrumentation.")
15.40 Flow Measurements, Use and Maintenance
Flow measurement is the determination of the quantity of a
mass in movement within a known length of time (Fig. 15.37).
The mass may be solid, liquid, or gas and is usually contained
within physical boundaries such as tanks, pipelines, and open
channels or flumes. The limits of such physical or mechanical
MASS
Fig. 15.37 Flow mass
boundaries provide a measurable dimensional AREA that the
mass is passing through. The speed at which the mass passes
through these boundaries is related to dimensional distance
and units of time; it is referred to as VELOCITY. Therefore, we
have the basic flow formula:
Quantity	=	Area x Velocity
Q	=	AV
or
Q, cu ft/sec	= (Area, sq ft) (V. ft/sec)
or
Q, cu m/aec	- (Area, sq m) (V, m/sec)

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Maintenance 313
The performance of a treatment facility cannot be evaluated
or compared with other plants without flow measurement. Indi-
vidual treatment units or processes in a treatment plant must
be observed in terms of flow to determine their efficiency and
loadings. Flow measurement is important to plant operation as
well as to records of operation. The devices used for such
measurement must be understood, be used properly, and
most important, be maintained so that information obtained is
accurate and dependable.
15.41	Operators' Responsibilities
Instrumentation and flow measurement devices should be
considered as fragile mechanisms. Rough handling will dam-
age the units in as serious a manner as does neglect. Treat the
devices with care, keep them clean, and they will perform their
designed functions with accuracy and dependability.
15.42	Various Devices for Flow Measurement
The selection of a type of flow-metering device, and its loca-
tion, is made by the designer in the case of new plant construc-
tion. It is also possible that a metering device will have to be
added to an existing facility. In both cases the various types
available, their limitations, and criteria for installation should be
known. Often the criteria for installation must be understood for
the proper use and maintenance of a fluid flow meter. Metering
devices commonly used in treatment facilities are listed below.
CONSTANT DIFFERENTIAL - A mechanical device called
the "float" is placed in a tapered tube in the flow line (Fig.
15.38). The difference in pressures above and below the float
causes the float to move with flow variations. Instantaneous
rate of flow is read out directly on a calibrated scale attached to
the tube. Read scale behind top of float to obtain flow rate.
FLOAT (READ TOP FLOAT RING
TO CORRESPOND WITH
ROTAMETER TUBE SCALE)
Fig. 15.38 Rotameter
HEAD AREA • A mechanical constriction or barrier is placed
in the open flow line causing an upstream rise in liquid level
(Figs. 15.39, 15.40 and 15.41). The rise or "head" (H) is
mathematically related to velocity (speed) of the flow. The
head measurement can be used in a formula to calculate flow
rate.
Type
Constant Differential
Head Area
Velocity Meter
Differential Head
Displacement
Common Name
Rotameter
Weirs
Rectangular
Cipoletti
V-Notch
Proportional
Flumes
Parshall
Palmer-Bowlus
Nozzles
Propeller
Magnetic
Shuntflow
Venturi Tube
Row Nozzle
Orifice
Piston
Diaphragm
Application
Liquids and Gases
a. Chlorination
Liquids - partially filled channels, basins, or
clarifiers
a.	Influent
b.	Basin control
c.	Effluent
d.	Distribution
Liquids - partially filled pipes and channels
a.	Influent
b.	Basin control
c.	Effluent
d.	Distribution
Liquids - channel flow, clean water piped
flow
Liquids and sludge in closed pipe
a.	Influent
b.	Basin control
c.	Sludge recirculation
d.	Distribution
Gases - closed pipe
a. Digester gas
Gases and liquids in closed pipes
a.
b.
c.
d.
e.
Influent
Basin control
Effluent
Digester gas
Distribution
Gases and liquids in closed pipes
a.	Plant water
b.	Digester gas
A description of how each device works is in reality a definition of the meter type.

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314 Treatment Plants
AREA
FLOW
HEAD
S1D£
Fig. 15.39 Rectangular weir
AREA
HEAD
FLOW
Fig. 15.40 Palmer-Bowles

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Maintenance 315
FLUME
HEAD
FLUME
SIDE
Fig. 15.41 Parshall flume
VELOCITY METERS - The velocity of the liquid flowing past
the measurement point through a given area gives a direct
relation to flow rate. The propeller type is turned by fluid flow
past propeller vanes which move gear trains. These gear trains
are used to indicate the fluid velocity or flow rate. The velocity
of liquid flow past the probes of a magnetic meter is related to
flow of electrical current between the probes and is read out as
the flow rate through secondary instrumentation. (See Section
15.44) Pitot tubes are used to measure the velocity head (H) in
flowing water to give the flow velocity (V = V2gH). (Fig.
15.42)
FLOW
H where
V-V2gH
Fig. 15.42 Pitot tube
DIFFERENTIAL PRODUCERS - A mechanical constriction
(Fig. 15.43) in pipe diameter (reduction in pipe diameter) is
placed in the flow line shaped to cause the velocity of flow to
increase through the restriction. When the velocity increases, a
pressure drop is created at the restriction. The difference be-
tween line pressure at the meter inlet and reduced pressure at
the throat section is used to determine the flow rate which is
indicated by a secondary instrument.
FLOW
I
DIFFERENTIAL
PRESSURE
-CONSTRICTION
Fig. 15.43 Differential producer
1
DISPLACEMENT UNITS - Liquid or gas enters, fills a tank or
chamber of known dimensions, activates a mechanical
counter, and empties the tank in readiness for another filling.
As the chamber fills and empties, mechanical gearing acti-
vates a counter which measures the amount of time the cycle
takes. Flow rate can then be calculated using the size of the
tank and the time factor.
15.43	Location of Measuring Devices
The selection of a particular type of meter or measuring
device and its location in a particular flow line or treatment
faciltiy is usually a decision made by the plant designer. Ideally
the flow should be in a straight section before the meter. The
device must be accessible for servicing. In open channels the
flow should not be changing directions, nor should waves be
present in the metering section above the measuring device.
Valves, elbows, and other items that could disrupt the flow
ahead of a meter can upset the accuracy and reliability of a
flow meter. Most flow meters are calibrated (checked for accu-
racy) in the factory, but they also should be checked in their
actual field installation. When a properly installed and field-
calibrated meter starts to give strange results, check for
obstructions in the flow channel and the flow-metering device.
QUESTIONS
Write your answers in a notebook and then compare your
answers with those on page 323.
15.4A	What is flow measurement?
15.4B	Write the basic flow formula.
15.4C	Why should flow be measured?
15.40	List several types of flow-measuring devices.
15.4E If a flow meter does not read properly, what items
should be checked as potential causes of error?
15.44	Conversion and Readout Instruments and
Controls
Conversion and readout instrumentation is used to convert
the initial measurement (for example, depth of water) to a more
commonly used number or value (depth of water in a Parshall
flume to flow of water in MGD). The type of device depends
upon what the sensor device measures and what kind of re-
sults are desired. Often the conversion device will only transmit
the signal (depth of water) to another meter which will interpret
the signal and convert it to a usable number (flow in MGD).
Instruments used with flow-measurement equipment are clas-
sified as transmitters, receivers, recorders, controllers, and
summators or totalizers. All of the different devices available
are too numerous to list. Most devices used today will fall into
the classifications outlined in the following paragraphs.
15.440	Mechanical Meters
Mechanical meters are devices which measure the variable
flow indicator and convert this value into a usable number.
Conversion of the flow variable to a scale or meter giving the
usable number may be by gear trains, hydraulic connections,
magnetic sensing, electrical connections, and many other de-
vices.
15.441	Transmitters
Transmitters send the flow variable, as measured by the
measuring device, to another device for conversion to a usable
number. Variables are transmitted mechanically, electrically,
and pneumatically.

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316 Treatment Plants
A type of transmitter which has come into great use is the
magnetic flow transmitter. This in-line unit contains two sen-
sors (electrodes) within an open tube. A third electrode serves
as a ground. When liquid flows in the tube, voltage is con-
ducted between the two sensors. This offers a measurable
signal for flow measurement.
15.442 Receivers
Receivers pick up the transmitted signal and convert it to a
usable number. There are four types of receivers (receiving
meters):
1.	INDICATING (Fig. 15.44): The components include (a) the
Indicator Hand, (b) the Indicator Scale, and (c) the Input
Connection. Power through the input connection (com-
monly 115 volts) moves the indicator hand which will point
to a value on the scale.
2.	RECORDING (Fig. 15.45): The chart upon which the meter
value is being recorded may run horizontally, vertically, or
circular. The pen (there may be more than one) is usually
self-inking with an ink reservoir providing the ink. Capillary
action carries the ink from the reservoir, through a small
supply tube, into the pen. The pen merely draws a line (after
receiving a signal through the input connection) on the
chart, as a motor slowly drives the chart. Commonly, the
pen moves when a different type of signal is received.
When this happens, the line will be drawn at another point
on the chart, and another value will be recorded.
3.	TOTALIZING (Fig. 15.46): The two components include the
dial face scale and the input connection. The dial face
(counter) is merely a display of numbers which may be
digital or a series of circular dials like an automobile odome-
ter.
4.	MULTIPURPOSE: Logically, this type of receiver has fea-
tures of two or more of the previously mentioned receivers.
Common units have an indicator, a recording chart, and a
totalizer.
15.443 Controllers
Controllers are similar to receivers except they are capable
of comparing received signals with other values and sending
corrective or adjusting signals when necessary. The compared
value may be manually set or it may be based on another
received signal. The correction or adjustment may be propor-
tional to the size of the deviation of the compared values, may
be a gradual adjustment, or may provide a predetermined cor-
rection based on the size of the deviation and your objectives.
Selection and adjustment of controllers should be done by a
specialist in the field or the manufacturer's representative.
Maintenance must be done according to manufacturer's in-
structions.
15.45 Sensor Maintenance
EACH INDIVIDUAL SENSING METER WILL HAVE ITS
OWN MAINTENANCE REQUIREMENTS. In any instrument,
the sensor is the most common source of problems.
The most important single item to be considered in mainte-
nance is good housekeeping. Always keep sensors and all
instrumentation very clean. Good housekeeping, the act of
providing preventive maintenance for each of the various sen-
sors, includes being sure that foreign bodies are not interfering
with the measuring device. Check for and remove deposits
which will build up from normal use. Repair the sensor or
measuring device whenever it is damaged.
.,...50
, ~ t
) 0N %	'
20~„
10
60


:80
" 'J•• '1
V
90
Fig. 15.44 Indicating receiver
Common preventive maintenance suggestions:
Meter Type
Constant Differential
Rotameters
Head Area
Weirs:
Retangular
Cipoletti
V-Notch
Proportional
Flumes:
Parshall
Palmer-Bowlus
Nozzles
Velocity Meter
Propeller
Shuntflow
Magnetic
Differential
Producers
Displacement
Suggested Maintenance
Disassemble and clean tube and float
when deposits are observed.
Flow formula is based on square clean
edges of the weir in contact with water
and with free fall over the weir (no
downstream water backing up and
flooding the weir). Clean and brush off
deposits that accumulate in the weir.
Keep weir and up- and down-stream
channels clear of foreign bodies and
interference.
Normally used with float wells, keep
sensor line between well and flume
clean; clean off deposits.
Should not be used on anything but
clear water. Grease and inspect
yearly.
Keep dampening chamber fluid level
up to indicating line; periodically drain
to remove collected sediment.
Manufacturers are providing various
cleaning mechanisms to clean the
Internal parts regularly. If you as an
operator manually operate, be sure to
perform maintenance on schedule; if
automatically, check action frequently.
Provide for periodic meter removal
from line and physically clean meter.
Provide for periodic back-flushing of
unit.
Venturi, nozzle, and orifice hydraulic
connections should be back-flushed
regularly. Installation should be ar-
ranged for internal surface cleaning on
a reasonable schedule.
Periodically drain and flush. Keep
greased as necessary; check fre-
quently on operation.

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Maintenance 317

Fig. 15.45 Recording receiver
Fig. 15.46 Totalizing receiver

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318 Treatment Plants
External connections between the sensing and conversion
and readout devices should be checked to ensure such con-
nections are clean in appearance and connections are firm. Be
sure no foreign obstruction will interfere or promote wear. On
mechanical connections, grease as directed; on hydraulic or
pneumatic connections, disconnect and ensure free flow in the
internal passage.
15.46 Conversion and Readout Instrument Maintenance
Both the mechanically actuated unit and the transmitters will
have direct sensor connections. Cleaning and checking on a
regular schedule is essential to avoid problems with the usual
accumulation of foreign material. Maintenance for the internal
parts to either device is minimized when the sensor connec-
tions are clean and operable. Normal wear will occur and is
increased when sediments and deposits are not removed regu-
larly as directed. Lubricate mechanical components as di-
rected by the equipment manufacturers' instrument manuals.
Do not over-lubricate, because it causes other difficulties
equally as troublesome as under-lubrication.
Receiver maintenance is limited to periodic checking of me-
chanical parts, proper lubrication, and good houskeeping
within the unit. When inking systems are used, ensure an
adequate supply of ink and a free flow through the capillary
tube. Moisture should be eliminated by heat if required.
Pneumatic instruments should be watched carefully to ensure
that foreign particles which might be introduced by the air sup-
ply do not cause clogging in the actuating elements. Pneumat-
ic systems are usually protected by air filters or traps at the
supply source and individual units at the instrument. Filters
should be cleaned and blown down on a regular schedule to
ensure their efficient operation in cleaning the air supply. Dou-
ble the frequency of blowdowns during wet weather and
periods of high humidity. In the case of clogging of small
orifices and devices of the pneumatic system, DO NOT AT-
TEMPT TO PRESSURIZE THE SYSTEM AT HIGHER THAN
NORMAL OPERATING PRESSURE FOR CLEANING. Such
action will damage internal parts. Check for air leaks which will
cause decreased efficiency. Follow procedures as outlined by
the manufacturer and as shown in the instrumentation manu-
als.
15.47 Manufacturer's Responsibilities
Most reputable manufacturers are equipped to provide re-
pair service in the case of worn parts or mechanical failure./r
IS RECOMMENDED THAT MAJOR SERVICE BE LEFT TO
TRAINED EMPLOYEES OF THE MANUFACTURER. It is pre-
ferred that manufacturers have field service available for repair
on the plant premises; however, if such service is not available,
the device should be returned to the factory.
Many manufacturers have a maintenance contract service
available in which a trained service employee periodically, on a
prescribed schedule, checks the instrument in all ways includ-
ing accuracy and wear factors. Such periodic checking allows
for replacement of parts prior to a complete breakdown. Parts
which would normally wear over a time period are replaced by
this service representative who will anticipate such need from
an experience factor.
DO NOT ATTEMPT INSTRUMENT SERVICE, PARTS
REPLACEMENT, OR REPAIR WORK UNLESS YOU HAVE
READ THE INSTRUCTION MANUAL THOROUGHLY AND
YOU UNDERSTAND WHAT YOU ARE DOING. FOLLOW
THE PROCEDURES AS SET FORTH IN THE INSTRUC-
TION MANUAL CAREFULLY.
All instruments are connected to a power supply from some
source. That power supply is potentially dangerous unless
handled properly. Be sure all electrical power is shut off and
secured so that others cannot unintentionally switch on the
source. On electrical and electronic devices, the electrical
power used and/or generated within the device is exceptionally
dangerous, both to the operator and to the other component
equipment. Do not attempt sen/ice unless you are qualified
and authorized to do so.
Recording charts often seem to accumulate at a rapid rate,
and a decision must be made whether to store or destroy old
records. Inconvenient as it may be, records should be retained.
They are the backbone of reference information needed for
future planning and plant expansion when necessary. Above
all, if properly used, they are a valuable source of information
for checking efficiency of the plant processes. Storage space
may be minimized by preparing summary records, microfilm
photocopy, or selective sampling and storage of the usual and
unusual.
15.48 Calibration and Cross-Checklng Meter
Performance
Ensuring proper meter performance protects the taxpayers'
investments as well as contributes to a smooth-running plant.
Properly calibrated meters reduce the need for many time-
consuming tasks (for example laboratory tests). Since in-
strumentation is the "nervous system" of the plant, field cali-
bration of meters is often the operator's responsibility and
should be done daily.
Recording meters are often difficult to calibrate; this task is
usually reserved for service instrumentation technicians.
Indicating meters often have a switch or knob which, when
placed in "calibration" mode, will cause the indicating hand to
move to a pre-set location on the scale. These meters also
may be compared with another meter or checked against a
substance of known value; for example, calibrating a pH meter
with a buffer solution of known value. The meter also may be
checked for performance. If an indicating flow meter, attached
to a pump, registers 50 GPM, check to see if it takes a minute
to fill a 55-galton drum to the 50 gallon mark or another mark in
a vessel of known volume.
Totalizing meters can be checked by adaptation of the same
principle. Compare the total flow shown by the meter with the
flow into a vessel with a known volume.
Multipurpose meters can usually be checked for calibration
by comparing one portion of the meter (for example, the indi-

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Maintenance 319
eating meter) to another portion (the value displayed on the
recording meter strip chart).
15.49 Troubleshooting Meters
If plant maintenance personnel are responsible for meter
troubleshooting, they will need:
1.	Adequate spare parts;
2.	Necessary test equipment;
3.	Proper tools;
4.	Proper shop area (clean and well-lighted);
5.	A thorough knowledge of operating principles of the plant's
instruments; and
6.	A complete set of service manuals and parts catalogs.
When a flow meter does not read properly, check the pri-
mary sensor, transmitter, receiver, and power supply.
Troubleshooting information on specific pieces of instrumenta-
tion will usually be covered in the instrument's service mainte-
nance manual. Unfortunately, the completeness of this infor-
mation often leaves much to be desired.
QUESTIONS
Write your answers in a notebook and then compare your
answers with those on page 323.
15.4F If a flow meter does not read properly, what items
should be checked as potential causes of error?
15.4G What is the purpose of transmitting instruments?
15.4H What is the most important item in maintaining flow
meters?
15.4I What should you do with old recording chart records?
15.4J Why should you calibrate and cross-check meter per-
formance regularly?
15.5 REVIEW OF PLANS AND SPECIFICATIONS
This section covers pumps and lift stations. Many large
municipal agencies do their own design work for pumps and lift
stations. Smaller agencies usually rely upon a consulting en-
gineering firm for design. In either case, operators should be
given the opportunity to review the prints and specifications of
a new lift station or pumping facility before the award of a
contract for construction and installation. This review is very
important to be sure adequate provisions have been made for
the station pumps, equipment and instrumentation to be easily
and property operated and maintained.
15.50 Examining Prints
When examining the prints, operators should look for acces-
sibility not only for equipment, but for operators to get to the
facilities. Is there sufficient space for vehicles to park and not
restrict vehicles passing on streets or pedestrians on side-
walks? Is there room to use hydrolifts, cranes and high velocity
cleaners as needed at the lift station? Are overhead clear-
ances of power lines, trees and roofs adequate for a crane to
remove large equipment? Is there sufficient room to set up
portable pumping units or other necessary equipment in cases
of major station failures or disasters? Are floors sloped to pro-
vide drainage where needed and are drains located in low
spots? Are station doors and access hatches large enough to
remove the largest piece of equipment? Are lifting hooks or
overhead rails available where needed in the structure? Has
sufficient overhead and work room been provided around
equipment and control panels to work safely? Is lighting inside
and outside the facility provided and is it adequate? Does the
alarm system signal high water levels in the wet well and water
on the floor of the dry well? Is there sufficient fresh water at a
high enough pressure to adequately wash down the wet well?
Are there any man traps or head knockers such as low hanging
projections or pipes, unprotected holes, or unsafe stairs or
platforms? Is there access to the wet well? If you have to clean
out incoming lines, it may be necessary to put a temporary
pump in the wet well. All of these questions must be answered
satisfactorily if the lift station or pumping facility is to be easily
operated and maintained.
Equipment should be laid out orderly with sufficient work
room and access to valves and other station equipment, con-
trols, wiring, pipes and valves. If there is any possibility of
future growth and the station may be enlarged, be sure provi-
sions are made to allow for pumping units to be changed or for
the installation of additional pumping units. If additional pump-
ing units will be necessary, be sure spools and valves are built
now for ease of expansion. Be sure there is sufficient room to
add electrical switchgear for future units. If stationary standby
power units are not provided, make certain there are external
connections and transfer switches for a portable generator.
15.51 Reading Specifications
Review the specifications for the acceptability of the equip-
ment, piping, electrical system, instrumentation, and auxiliary
equipment. Determine if the equipment is familiar to your
agency and if its reliability has been proven. Find out what
warranties, guarantees, and operation and maintenance aids
will be provided with the equipment and the lift station. Require
a list of names, addresses and phone numbers of persons to
contact in case help is needed regarding supplies or equip-
ment during start up and shake down runs. Be sure that the
equipment brochures and other information apply to the
equipment supplied. Sometimes new models are installed and
you are provided with old brochures.
Be sure the painting, color coding on pipes and electrical
circuits meet with your agency's practice. Try to standardize
electrical equipment and components as much as possible so
one manufacturer can't blame the other when problems
develop. Standardization also can help to reduce the inventory
of spare parts necessary for replacement. A few hours spent
reviewing plans and specifications will save many days of hard
and discouraging labor in the future when it is a major job to
make a change. Very often changes on paper are relatively
simple.

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320 Treatment Plants
QUESTIONS
Write your answers in a notebook and then compare your
answers with those on page 323.
15.5A Why should operators be given an opportunity to re-
view the prints and specifications of a new lift station
before the award of a construction contract?
15.5B Why is accessibility to pumping facilities important?
15.5C What information should be determined for equipment
to be installed in a pumping facility?
15.5D Why should prints and specifications be carefully re-
viewed?
15.6 SUMMARY
1.	Establish and follow a regular maintenance program.
2.	Thoroughly read and understand manufacturers' mainte-
nance instructions. Ask for assistance if you do not under-
stand them. Follow the manufacturers' instructions in your
maintenance program.
3.	Critically evaluate the maintenance and repair capabilities
of yourself and your facilities. Request the help of an expert
when necessary.
A.
15.7 ADDITIONAL READING
1.	MOP 11, Chapter 5, "Wastewater Pumping," and Chapter
26, "Process Management and Control. "*
2.	NEW YORK MANUAL, Chapter 13, "Maintenance of Plant
and Equipment."
* Depends on edition.
3.	TEXAS MANUAL, Chapter 7, "Lift Stations and Sewage
Pumps," Chapter 8, "Measurement of Wastewater Flow"
and Chapter 29, "Plant Maintenance."
4.	OPERATION AND MAINTENANCE OF WASTEWATER
COLLECTION SYSTEMS, Kenneth D. Kerri and John
Brady, California State University, Sacramento, 6000 Jay
Street, Sacramento, California 95819. Price $30.00. See
Chapter 5, "Pipeline Cleaning and Maintenance Methods,"
Chapter 7, "Lift Stations" and Chapter 8, "Equipment Main-
tenance."
5.	MAINTENANCE MANAGEMENT SYSTEMS FOR MUNIC-
IPAL WASTEWATER FACILITIES, U.S. Environmental Pro-
tection Agency, Office of Water Program Operations, Wash-
ington, D.C. 20460, October 1973, 430/9-74-004. For sale
by Superintendent of Documents, U.S. Government Print-
ing Office, Washington, D.C. 20402. Stock No. 055-011-
00762-1. Price $1.60.
&NP OP M&OH 6
OP 6
ON
aNfeNAMCe
Please answer the discussion and review questions before
continuing with the Objective Test.

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Maintenance 321
DISCUSSION AND REVIEW QUESTIONS
Chapter 15. MAINTENANCE
(Lesson 6 of 6 Lessons)
Write the answers to these questions in your notebook be-
fore continuing. The problem numbering continues from Les-
son 5.
32.	Calculate the quantity of flow in cubic feet per second
when wastewater flows through an area of 2.5 square feet
at a velocity of 1.5 feet per second.
33.	What type of flow meter is used to measure the flow of
chlorine gas?
34.	What does a pitot tube measure?
35.	Why should a flow meter be calibrated in its field installa-
tion?
36.	What is the most common source of problems in flow
meter instruments?
37.	Why should major repairs of instrumentation be conducted
by trained employees of the manufacturer?
38.	How can scum lines be kept from plugging?
PLEASE WORK THE OBJECTIVE TEST NEXT
SUGGESTED ANSWERS
Chapter 15. MAINTENANCE
Answers to questions on page 247.
15.OA A good maintenance program is essential for a
wastewater treatment plant to operate continuously at
peak design efficiency.
15.0B The most important item is maintenance of the me-
chanical equipment — pumps, valves, scrapers, and
other moving equipment. Other items include plant
buildings and grounds.
15.0C A good record system tells when maintenance is due
and also provides a record of equipment performance.
Poor performance is a good justification for replace-
ment or new equipment. Good records help keep your
warranty in force.
15.0D Both cards are vital in a good record-keeping system.
The equipment service record card is a permanent or
master card that indicates when or how often certain
maintenance work should be done. The service record
card is a record of who did that work on what date and
is helpful in determining when the future maintenance
work is due.
Answers to questions on page 248.
15.0E A building maintenance program will keep the building
in good shape and includes painting when necessary.
Attention also must be given to electrical systems,
plumbing, heating, cooling, ventilating, floors, win-
dows, and roofs. The building should be kept clean,
tools should be stored in their proper place, and es-
sential storage should be available.
15.0F When plant tanks and channels are drained, the
operator should check surfaces for wear and deterio-
ration from wastewater or fumes. Protective coatings
should be applied where necessary to prevent further
damage.
15.0G Well-groomed and neat grounds are important be-
cause many people judge the ability of the operator
and the plant performance on the basis of the appear-
ance of the plant.
Answers to questions on page 249.
15.0H Chlorine is toxic to humans and will cause corrosion
damage to equipment.
15.0I Large chlorine leaks can be detected by smell. Small
leaks are detected by soaking a cloth with ammonia
water and holding the cloth near areas where leaks
might develop. A white cloud will indicate the presence
of a leak.
Answers to questions on page 249.
15.0J Emergency phone numbers for a treatment plant
should include the phone numbers for police, fire,
hospital and/or physician, responsible plant officials,
local emergency disaster office, emergency team and
CHEMTREC, (800) 424-9300.
15.OK
A training program for an emergency team should in-
clude:
Use of proper equipment (self-contained breathing
apparatus, repair kits and repair tools).
Properties and detection of hazardous chemicals.
Safe procedures for handling and storage of chem-
icals.
Types of containers, safe procedures for shipping
containers, and container safety devices.
Installation of repair devices.
Simulated field emergencies.
END OF ANSWERS TO QUESTIONS IN LESSON 1

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322 Treatment Plants
Answers to questions on page 269.
15.1 A Pumps must be lubricated in accordance with manu-
facturers' recommendations. Quality lubricants should
be used.
15.1B In lubricating motors, too much grease may cause
bearing trouble or damage the winding.
Answers to questions on page 270.
15.1C If a pump will not start, check for blown fuses or tripped
circuit breakers and the cause. Also check for a loose
connection, fuse, or thermal unit.
15.1D To increase the rate of discharge from a pump, you
should look for something causing the reduced rate of
discharge, such as pumping air, motor malfunction,
plugged lines or valves, impeller problems, or other
factors.
Answers to questions on page 272.
15.1E If a pump that has been locked or tagged out for main-
tenance or repairs is started, an operator working on
the pump could be seriously injured and also equip-
ment could be damaged.
15.1F Normally a centrifugal pump should be started after
the discharge valve is opened. Exceptions are treat-
ment processes or piping systems with vacuums or
pressures that cannot be dropped or allowed to fluc-
tuate greatly while an alternate pump is put on the line.
Answers to questions on page 274.
15.1G Before stopping an operating pump:
1.	Start another pump (if appropriate); and
2.	Inspect the operating pump by looking for develop-
ing problems, required adjustments, and problem
conditions of the unit.
15.1H A pump shaft or motor will spin backwards if wastewa-
ter being pumped flows back through the pump when
the pump is shut off. This will occur if there is a faulty
check valve or foot valve in the system.
15.11 The position of all valves should be checked before
starting a pump to ensure that the wastewater being
pumped will go where intended.
Answers to questions on' page 274.
15.1 J The most important rule regarding the operation of
positive displacement pumps is to NEVER start the
pump against a closed discharge valve.
15.1K If a positive displacement pump is started against a
closed discharge valve, the pipe, valve or pump could
rupture from excessive pressure. The rupture will
damage equipment and possibly seriously injure or kill
someone standing nearby.
15.1L Both ends of a sludge line should never be closed tight
because gas from decomposition can build up and
rupture pipes or valves.
END OF ANSWERS TO QUESTIONS IN LESSON 2
Answers to questions on page 283.
15.2A A cross connection is a connection between two piping
systems where an undesirable water (water from
water seal) could enter a domestic water supply.
15.2B Yes. A slight leakage is desirable when the pumps are
running to keep the packing cool and in good condi-
tion.
15.2C To measure the capacity of a pump, measure the vol-
ume pumped during a specific time period.
Capacity, GPM= Volume- 9all°"s
Time, minutes
liters _ Volume, liters
or
Capacity,
sec Time, sec
15.2D rarity,	Volume- 9^5
Time, minutes
= 10 ft x 15 ft x 1.7 ft x 7.5 gal/cu ft
5 minutes
= 382.5 GPM
or
Capacity,liters = Volume' liters
sec Time, sec
= 3mx5mx0.5mx 1000 L/1 cu m
5 minutes x 60 sec/min
= 25 liters/sec
15.2E Before a prolonged shutdown, the pump should be
drained to prevent damage from corrosion, sedimenta-
tion, and freezing. Also, the motor disconnect switch
should be opened to disconnect motor.
Answers to questions on page 286.
15.2F Shear pins commonly fail in reciprocating pumps be-
cause of (1) a solid object lodged under piston, (2) a
clogged discharge line, or (3) a stuck or wedged valve.
15.2G A noise may develop when pumping thin sludge due to
water hammer, but will disappear when heavy sludge
is pumped.
END OF ANSWERS TO QUESTIONS IN LESSON 3
Answers to questions on page 287.
15.2H When checking an electric motor, the following items
should be checked periodically, as well as when
trouble develops:
1.	Motor condition
2.	Note all unusual conditions
3.	Lubricate bearings
4.	Listen to motor
5.	Check temperature

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Maintenance 323
Answers to questions on page 291.
15.21 A properly adjusted horizontal belt has a slight bow in
the slack side when running. When idle, it has an alive
springiness when thumped with the hand. Vertical
belts should have a springiness when thumped. To
check for proper alignment, place a straight edge
against the pulley face or faces. If a ruler won't work,
use a transit for long runs, or the belt may be exam-
ined for wear.
15.2J Always replace sprockets when replacing a chain be-
cause old, out-of-pitch sprockets cause as much chain
wear in a few hours as years of norma) operation.
Answers to questions on page 295.
15.2K Improper original installation of equipment, settling of
foundations, heavy floor loadings, warping of bases,
and excessive bearing wear could cause couplings to
become out of alignment.
15.2L Shear pins are designed to fail if a sudden overload
occurs that could damage expensive equipment.
END OF ANSWERS TO QUESTIONS IN LESSON 4
Answers to question on page 299.
15.2M The most common maintenance required by (a) gate
valves is oiling, tightening, or replacing the stem stuff-
ing box packing. The most common maintenance re-
quired by (b) sluice gates is testing for proper opera-
tion, cleaning and painting, and adjusting for proper
clearance.
Answers to questions on page 310.
15.2N The job of the dehumidifier is to remove moisture from
the atmosphere.
15.20 If the dehumidifier does not do its job, moisture will
form on pump controls, circuits, and other essential
equipment and cause malfunctions due to corrosion
and oxidation.
15.2P The purpose of an air-gap separation system is to pro-
tect the potable (drinking) water supply in case waste-
water backs up from a treatment process.
15.2Q To maintain a portable gas detector:
1.	Be sure battery is charged, and
2.	Calibrate using known standard gas concentrations
obtained from detector manufacturer.
END OF ANSWERS TO QUESTIONS IN LESSON 5
Answers to questions on page 312.
15.3A Plugged pipelines may be cleared by the use of pres-
sure methods, cutting tools, high-velocity pressure
units and as a last resort, dismantling the plugged sec-
tion and removing the obstruction.
15.3B To clear a plugged pump, isolate the pump from the
remainder of the plant by valving-off plugged pump
and tagging and locking-out power supply to pump.
Remove pump inspection plate and remove material
causing blockage.
Answers to questions on page 315.
15.4A Flow measurement is the determination of the RATE of
flow past a certain point, such as the inlet to the head-
works structure of a treatment plant. Flow is measured
and recorded as a quantity (gallons or cubic feet) mov-
ing past a point during a specific time interval (sec-
onds, minutes, hours, or days). Thus we obtain a flow
rate or quantity in cu ft/sec or MGD.
15.4B Quantity = Area x Velocity, or Q = AV.
15.4C Flow should be measured in order to determine
wastewater treatment plant loadings and efficiency.
15.4D Different types of flow measuring devices include con-
stant differential, head area, velocity meter, differential
head, and displacement.
15.4E Potential causes of flow meter errors include foreign
objects fouling the system or the meter may not be
installed in the intended location. (Liquids should flow
smoothly through the meter and flow should not be
changing directions, nor should waves be present on
the liquid surface above the measuring device.) Check
the primary sensor, transmitter, receiver, and power
supply.
Answers to questions on page 319.
15.4F When a flow meter does not read property, check the
primary sensor, transmitter, receiver, and power sup-
ply.
15.4G Transmitting instruments can take a reading (depth
measurement) from a flow metering device (Parshall
flume) and send it to a readout instrument which con-
verts the depth measurement to a flow rate (MGD).
15.4H The most important item in flow meter maintenance is
good housekeeping. Your instruments must be kept
clean and in good working condition.
15.4I Old recording charts should be stored for future refer-
ence, such as checks on plant performance, budget
justifications, and information needed for future plan-
ning. Storage space may be minimized by preparing
summary records, microfilm, photocopy, or selective
sampling and storage of the usual and unusual.
15.4J Meters should be calibrated and performance cross-
checked regularly to ensure accurate and reliable
meter readings under all conditions at all times.
Answers to questions on page 320.
15.5A Operators should review prints and specifications for
pumping facilities before construction to be sure
adequate provisions have been made for the facility to
be easily and properly operated and maintained.
15.5B Accessibility to a pumping facility is important because
operators and equipment need to be able to easily
reach the facility and have room to park vehicles and
work.
15.5C Before equipment is installed in a pumping facility, de-
termine its familiarity to your agency, reliability, war-
ranty, guarantees and operation and maintenance
aids that will be provided.
15.5D Prints and specifications should be carefully reviewed
before construction and installation because changes
are easily made on paper and much more difficult in
the field.
END OF ANSWERS TO QUESTIONS IN LESSON 6

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324 Treatment Plants
OBJECTIVE TEST
Chapter 15. MAINTENANCE
Please write your name and mark the correct answers on the
answer sheet as directed at the end of Chapter 1. There may
be more than one answer to each question.
1.	An Equipment Service Card is another name for a Service
Record Card.
1.	True
2.	False
2.	Building maintenance is NOT part of a treatment plant
operator's duties.
1.	True
2.	False
3.	A treatment plant library should contain copies of the
plant's drawings and specifications.
1.	True
2.	False
4.
5.
6.
7.
8.	Chlorine can be detected by a pH meter.
1.	True
2.	False
9.	An empty clarifier drained for inspection purposes could
float up out of the ground when the ground water level is
high.
1.	True
2.	False
10.	All gate valves have non-rising valve stems.
1.	True
2.	False
11.	Modern gate valves can be repacked without removing
them from service.
1.	True
2.	False
12.	Old gaskets should be salvaged.
1.	True
2.	False
13.	Which of the following would NOT be found on an equip-
ment service card?
1.	When work is to be done
2.	Work done
3.	Work to be done
14.	Periodic draining and inspection of treatment plant struc-
tures may
1.	Allow operators to take annual leave.
2.	Help prevent the discharge of improperly treated
effluent into receiving waters.
3.	Help prevent unexpected and costly shutdowns.
4.	Reduce loadings on other treatment processes.
5.	Reveal a crack in the bottom of a clarifier.
Power couplings between driver and driven parts of a ma-
chine should be
1.	Kept in alignment.
2.	Kept in a sealed condition.
3.	Kept under power.
4.	Periodically drained and refilled.
5.	Periodically refaced.
The duties of a wastewater treatment plant operator may
include
1.	Keeping maintenance records.
2.	Maintaining equipment and buildings.
3.	Painting and cleaning plant buildings.
4.	Public relations.
5.	Regulation of plant treatment processes.
Equipment service cards and service record cards should
1.	Identify the piece of equipment that the record card
represents.
2.	Indicate the work done.
3.	Indicate the work to be done.
4.	Maintain selective service records.
5.	Record sick leave.
18. How can a chlorine leak be detected?
1.	By an explosiometer
2.	By checking the rotameter
3.	By waving an ammonia-soaked rag
4.	Green or reddish deposits on metal
5.	Smell
19. Flow records provide
1.	Data for calculating plant input and output.
2.	Data to control plant processes.
3.	Information about equipment design specifications.
4.	Information for regulatory agencies.
5.	Information required by the equipment warranty.
All pumps in a wastewater treatment plant are centrifugal
pumps.
1.	True
2.	False
Pumps in a wastewater treatment plant are driven only by
electric motors.
1.	True
2.	False
If a pump is going to be shut down for a long period of
time, the pump should be drained.
1.	True
2.	False
Anaerobic sludge digesters usually are drained and
cleaned once a year.
1.	True
2.	False

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Maintenance 325
20. If a flow meter appears to be operating improperly, the
operator should
1.	Check connections.
2.	Check need for lubrication of moving parts.
3.	Divert the flow to a different meter.
4.	Look for foreign objects in the system.
5.	Replace the meter scale.
27. If a pump will not start, check for
1.	Loose terminal connections.
2.	Nuts, bolts, scrap iron, wood, or plastic in the wrong
places.
3.	Shaft binding or sticking.
4.	Tripped circuit breakers.
5.	Water in the wet well.
21.	If a flow meter does not read properly, what items should
be checked as potential causes of error?
1.	All items listed in manufacturer's troubleshooting guide
2.	Blow the transmission lines out with high pressure air
3.	Installation of sensor and readout devices
4.	Power supply to instruments
5.	Restrictions in the sensor and transmitter
22.	Float and electrode switches should be checked at least
once a week to see that the
1.	Chlorine containers are not empty.
2.	Controls respond to changing water levels in the wet
well as expected.
3.	Floatable solids are floating.
4.	Pump motor starts and stops at the proper times and
wet well levels.
5.	Switches change the direction of flow.
23.	Level control systems in a wet well include
1.	Bubblers.
2.	Diaphragms.
3.	Electrodes.
4.	Floats.
5.	Hearts.
24.	What happens if you DO NOT periodically drain and in-
spect plant tanks and channels?
1.	An emergency situation may develop and force you to
discharge partially or improperly treated wastes into
receiving waters during critical conditions.
2.	Costly repairs could result
3.	Serious maintenance problems could develop
4.	The operator will not know if cracks are developing in
underground tanks and channels.
5.	The operator will stay out of trouble
25.	A reciprocating pump
1.	Has a piston that moves back and forth.
2.	Has a rotating impeller.
3.	Has two check valves.
4.	Is used to pump sludge.
5.	Must never be operated with the discharge valve
closed.
26.	Before starting, a pump should
1.	Be allowed to sit outside and become accustomed to
adverse conditions.
2.	Be checked to ensure that the shafts of the pump and
motor are aligned.
3.	Be property lubricated.
4.	Have its shaft turned by hand to see that it rotates
freely.
5.	Run in the shipping crate so it can be returned if it
doesn't work.
28.	Pump maintenance includes
1.	Checking operating temperature of bearings.
2.	Checking packing gland.
3.	Lubricating the impeller.
4.	Operating two or more pumps of the same size alter-
nately to equalize wear.
5.	Preventing all water seal leaks around packing glands.
29.	Reciprocating pumps should be operated when the
1.	Centrifugal pumps are being maintained.
2.	Suction and discharge line valves are closed.
3.	Suction and discharge line valves open.
4.	Suction line valve closed and discharge line valve
open.
5.	Suction line valve open and discharge line valve
closed.
30. Preventive maintenance of electric motors includes
1.	Checking temperature of motor.
2.	Frequently starting and stopping the motor to give it a
rest.
3.	Keeping motor free from dust, dirt and moisture.
4.	Keeping motor outdoors where it can stay cool.
5.	Lubricating bearings.
31. Maintenance of couplings between the driving and driven
elements includes
1.	Draining old oil in fast couplings.
2.	Keeping proper alignment.
3.	Keeping proper alignment even with flexible couplings.
4.	Keeping the electrodes free of scum and corrosion.
5.	Regular use of a crowbar to line them up.
32. Maintenance of gate valves includes
1.	Lubricating bearing.
2.	Lubricating with Prussian blue.
3.	Operating inactive valves to prevent sticking.
4.	Refacing leaky valve seats.
5.	Tightening or replacing the stem stuffing box packing.
33. Approximately how far down should the level in a wet well
be lowered in two minutes by a pump with a rated capacity
of 500 gpm? The wet well is ten feet wide and ten feet
long.
1.	0.7 ft
2.	1.1 ft
3.	1.3 ft
4.	5.3 ft
5.	10 ft

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326 Treatment Plants
REVIEW QUESTIONS
A trickling filter 90 feet in diameter and four feet deep re-
ceives a flow of 3.2 MGD with a BOD of 115 mg/L.
34. The hydraulic loading on the trickling filter is approximately 35. The organic loading on the trickling filter is approximately
1. 400 gpd/sq ft.
1.
95 lbs BOD/1000 cu ft.
2. 425 gpd/sq ft.
2.
100 lbs BOD/1000 cu ft.
3. 450 gpd/sq ft.
3.
105 lbs BOD/1000 cu ft.
4. 475 gpd/sq ft.
4.
110 lbs BOD/1000 cu ft.
5. 500 gpd/sq ft.
5.
120 lbs BOD/1000 cu ft.
rnoTl

issSSSS

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CHAPTER 16
James Paterson
revised by
James Sequeira




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328 Treatment Plants
TABLE OF CONTENTS
Chapter 16. Laboratory Procedures and Chemistry
Page
OBJECTIVES	332
16.0	Importance of Laboratory Procedures	333
16.00	Should You Start This Lesson Now?	333
16.01	Material in This Lesson	333
16.02	References 	333
16.03	Acknowledgments 	334
LESSON 1
16.1	Basic Laboratory Terms, Equipment, and Techniques	335
16.10	Glossary of Laboratory Terms	335
16.11	The Metric System	339
16.12	Chemical Names and Formulas 	339
16.13	Laboratory Equipment	340
16.14	Use of Laboratory Glassware 	346
16.15	Solutions 	348
16.16	Titrations 	348
16.17	Use of a Spectrophotometer	348
16.18	Laboratory Work Sheets and Notebooks	350
16.19	Acknowledgment 	350
LESSON 2
16.2	Safety and Hygiene in the Laboratory		
16.20	Laboratory Hazards	353
16.200	Infectious Materials	353
16.201	Corrosive Chemicals	354
16.202	Toxic Materials	354
16.203	Explosive or Inflammable Materials	354
16.21	Personal Safety and Hygiene 	354
16.210	Laboratory Safety	354
16.211	Personal Hygiene	354

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Laboratory 329
16.22	Prevention of Laboratory Accidents	355
16.220 Chemical Storage 		355
16.211 Movement of Chemicals	355
16.222	Proper Laboratory Techniques 	356
16.223	Accident Prevention	356
Electrical shock 	356
Cuts 	356
Burns 	356
Toxic fumes	356
Waste disposal	357
Fire	357
16.23	Acknowledgment 	357
16.24	Additional Reading	357
LESSON 3
16.3	Sampling 	359
16.30	Importance	359
16.31	Representative Sampling	359
16.32	Time of Sampling	359
16.33	Types of Samples 	360
16.34	Sludge Sampling 	361
16.35	Sampling Devices 	361
16.36	Preservation of Samples	361
16.37	Quality Control in the Wastewater Laboratory	361
16.38	Summary	363
16.39	Additional Reading	363
LESSON 4
16.4	Laboratory Procedures for Plant Control	364
16.40	Clarity	364
16.41	Hydrogen Sulfide	364
16.410	H2S in the Atmosphere	364
16.411	HZS in Wastewater 	366
16.42	Settleable Solids	366
16.43	Suspended Solids 	367
16.44	Total Sludge Solids (Volatile and Fixed)	371

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330 Treatment Plants
LESSON 5
16.45	Tests for Activated Sludge Control	377
16.450	Settleability	377
16.451	Sludge Volume Index (SVI)	378
16.452	Sludge Density Index (SDI)	378
16.453	Sludge Age	378
16.454	Dissolved Oxygen in Aerator	379
16.455	Suspended Solids in Aerator	380
16.456	Mean Cell Residence Time	382
16.46	Tests for Digestion Control	383
16.460	Volatile Acids 	383
16.461	Total Alkalinity 	387
16.462	Carbon Dioxide (C02) in Digester Gas	389
16.463	Sludge (Digested) Dewatering Characteristics	391
16.464	Supernatant Graduate Evaluation	394
16.465	Temperature	395
16.47	Lime Analysis	395
LESSON 6
16.5 Laboratory Procedures For NPDES Monitoring	398
16.50	Need for Approved Procedures	398
16.51	Test Procedures	398
1.	Acidity	398
2.	Alkalinity, Total 	399
3.	Chemical Oxygen Demand (COD)	401
4.	Chloride 	403
5.	Chlorine Residual (Total) 	405
LESSON 7
6.	Coliform Group Bacteria	409
LESSON 8
7.	Dissolved Oxygen (DO) and Biochemical Oxygen Demand (BOD)	424
LESSON 9
8.	Hydrogen Ion (pH)
9.	Metals	
10. Nitrogen	
Ammonia	
432
433
433
433

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Laboratory 331
Total Kjeldahl Nitrogen (TKN) 	436
Nitrite 	438
Nitrate and Nitrite Nitrogen	441
11.	Oil and Grease	445
12.	Phosphorus	447
13.	Total Solids (Residue)	451
14.	Specific Conductance	453
15.	Sulfate 	455
16.	Surfactants	455
17.	Temperature 	455
18.	Total Organic Carbon 	456
19.	Turbidity	456

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332 Treatment Plants
OBJECTIVES
Chapter 16. LABORATORY PROCEDURES AND
CHEMISTRY
Following completion of Chapter 16, you should be able to
do the following:
1.	Work safely in a laboratory,
2.	Operate laboratory equipment,
3.	Collect representative samples of influents to and effluents
from a treatment process as well as sample the process,
4.	Prepare samples for analysis,
5.	Perform plant control tests,
6.	Analyze plant effluent in accordance with NPDES permit
requirements,
7.	Recognize shortcomings or precautions for the plant control
and NPDES tests, and
8.	Record laboratory test results.

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Laboratory 333
CHAPTER 16. LABORATORY PROCEDURES AND CHEMISTRY
16.0 IMPORTANCE OF LABORATORY PROCEDURES
Laboratory control tests are the means by which we control
the efficiency of our wastewater treatment process. By relating
laboratory results to operations, the plant operator can select
the most effective operational procedures, determine the effi-
ciency of treatment unit processes, and identify developing
treatment problems before they seriously affect effluent qual-
ity. For these reasons, a clear understanding of laboratory pro-
cedures is a must to any operator.
16.00 Should You Start This Chapter Now?
This chapter may be started whenever you wish. When you
read the lessons on treatment processes, you should begin to
wonder how certain tests are performed that are essential for
proper plant operation. At this time you may refer to this chap-
ter for a general discussion and a description of the laboratory
procedure.
You might wish to complete this lesson first in order to better
understand the operational aspects of the treatment process
lessons. Many operators and potential operators who are in-
terested in this profession have taken this course. Most of
them have said that they wanted to learn about the treatment
processes first and then learn how to apply the lab procedures
to plant operations. Many potential operators experienced dif-
ficulty with the terminology when they tried to work this chapter
before completing the lessons on the treatment processes. If
you are an experienced operator, are anxious to learn more
chemistry, and want to obtain a better understanding of lab
procedures, you may decide to try this lesson first.
Past experience has indicated that most operators prefer to
use this section as a reference while studying the lessons on
treatment processes. You are the operator who wants to learn
more about tretament plant operation, and you are encouraged
to use this material in any manner that you feel best fits your
particular situation and professional goals. Now is the time for
you to decide whether you are going to:
1.	Thumb through this lesson, proceed through the chapters
on treatment processes, and then complete this lesson;
2.	Complete the lessons on treatment processes, referring to
this lesson when interested, and then complete this lesson;
3.	Complete this lesson and then the lessons on treatment
processes; or
4.	Follow your own plan.
16.01	Material in This Lesson
A few of the lab procedures outlined in this chapter are not
"Standard Methods" (4)1, but are used by many operators be-
cause they are simple and easy to perform. Some of these
procedures are not accurate enough for scientific investiga-
tions, but are satisfactory for successful plant control and op-
eration. When lab data must be submitted to regulatory agen-
cies for monitoring and enforcement purposes, you must use
approved test procedures (see Section 16.5).
Each test section contains the following information.
1.	Discussion of test.
2.	What is tested?
3.	Apparatus.
4.	Reagents.
5.	Procedures.
6.	Precautions.
7.	Examples.
8.	Calculations.
If you would like to read an introductory discussion on labo-
ratory equipment and analysis, the Water Pollution Control
Federation has a good publication entitled "Simplified Labora-
tory Procedures" (3).
Good discussions of analytical equipment and their uses
may be found in "Basic Laboratory Techniques" (8).
16.02	References
1.	LABORATORY PROCEDURES FOR OPERATORS OF
WATER POLLUTION CONTROL PLANTS, by Joe Nagano.
Obtain from Secretary-Treasurer, California Water Pollu-
tion Control Association, 4876 Paseo de Vega, Irvine,
California 92715. Price $5.30 to members of CWPCA;
$9.54 to others.
2.	METHODS FOR CHEMICAL ANALYSIS OF WATER AND
WASTES, Center for Environmental Research Information,
U.S. Environmental Protection Agency, 26 West St. Clair
Street, Cincinnati, Ohio 45268.
3.	SIMPLIFIED LABORATORY PROCEDURES FOR
WASTEWATER EXAMINATION, WPCF Publication No.
M0018, 1976. $4.00 to WPCF members; $8.00 to others.
4.	STANDARD METHODS FOR EXAMINATION OF WATER
AND WASTEWATER, 14th Edition, 1976. $28 to WPCF
members; $35 to others.
5.	HANDBOOK FOR ANALYTICAL QUAUTY CONTROL IN
WATER AND WASTEWATER LABORATORIES, Center for
Environmental Research Information, U.S. Environmental
Protection Agency, 26 West St. Clair Street, Cincinnati
Ohio 45268.
1 Numbers In parentheses refer to references in Section 16.02.

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334 Treatment Plants
6.	HANDBOOK FOR EVALUATING WATER BACTERIOLOG-
ICAL LABORATORIES, U.S. Environmental Protection
Agency, EPA-670/9-75-006, August 1975. Available
through the National Technical Information Service,
Springfield, Virginia 22151. Order No. PB247 145/LL. Price
$12.00.
7.	"Guidelines Establishing Test Procedures for the Analysis
of Pollutants," FEDERAL REGISTER, Volume 41, No. 232,
pages 52780 to 52786, December 1, 1976.
8.	BASIC LABORATORY TECHNIQUES FOR THE NA-
TIONAL POLLUTANT DISCHARGE ELIMINATION SYS-
TEM, Department of Environmental Systems Engineering,
Clemson University, Clemson, South Carolina 29631. Price
$15.00.
Both References 3 and 4 may be obtained by writing:
Water Pollution Control Federation
2626 Pennsylvania Avenue, N.W.
Washington, D.C. 20037
Order forms may be found in the JOURNAL OF THE WATER
POLLUTION CONTROL FEDERATION.
16.03 Acknowledgments
Many of the illustrated laboratory procedures were provided
by Mr. Joe Nagano, Laboratory Director, Hyperion Treatment
Plant, City of Los Angeles, California. These procedures origi-
nally appeared in LABORATORY PROCEDURES FOR
OPERATORS OF WATER POLLUTION CONTROL PLANTS,
prepared by Mr. Nagano and published by the California Water
Pollution Control Association.

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Laboratory 335
CHAPTER 16. LABORATORY PROCEDURES AND CHEMISTRY
(Lesson 1 of 9 Lessons)
16.1 BASIC LABORATORY TERMS, EQUIPMENT, AND TECHNIQUES
16.10 Glossary of Terms
> GREATER THAN
DO > 5 mgIL, would be read as DO GREATER THAN 5 mgIL.
< LESS THAN
DO < 5 mg/L, would be read as DO LESS THAN 5 mg/L
ALIQUOT (AL-li-kowt)
Portion of a sample.
AMBIENT TEMPERATURE
(AM-bee-ent)
Temperature of the surroundings.
AMPEROMETRIC (am-PURR-o-MET-rick)	AMPEROMETRIC
A method of measurement that records electric current flowing or generated, rather than recording voltage. Amperometric titration is
a means of measuring concentrations of certain substances in water.
ANAEROBIC ENVIRONMENT (AN-air-O-bick)	ANAEROBIC ENVIRONMENT
A condition in which "free" or dissolved oxygen is NOT present in the aquatic environment.
ASEPTIC (a-SEP-tick)	ASEPTIC
Free from the living germs of disease, fermentation or putrefaction. Sterile.
BLANK	BLANK
A bottle containing only dilution water or distilled water, but the sample being tested is not added. Tests are frequently run on a
SAMPLE and a BLANK and the differences compared.
BUFFER	BUFFER
A solution or liquid whose chemical makeup neutralizes acids or bases without a great change in pH.
BUFFER CAPACITY	BUFFER CAPACITY
A measure of the capacity of a solution or liquid to neutralize acids or bases. This is a measure of the capacity of water or
wastewater for offering a resistance to changes in pH.
COLORIMETRIC MEASUREMENT
COLORIMETRIC MEASUREMENT
A means of measuring unknown concentrations of water quality indicators in a sample by MEASURING THE SAMPLE'S COLOR
INTENSITY. The color of the sample after the addition of specific chemicals (reagents) is compared with colors of known concentra-
tions.

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336 Treatment Plants
COMPOSITE (PROPORTIONAL) SAMPLES	COMPOSITE (PROPORTIONAL) SAMPLES
(com-POZ-it)
A composite sample is a collection of individual samples obtained at regular intervals, ususally every one or two hours during a
24-hour time span. Each individual sample is combined with the others in proportion to the flow when the sample was collected. The
resulting mixture (composite sample) forms a representative sample and is analyzed to determine the average conditions during the
sampling period.
COMPOUND	COMPOUND
A pure substance composed of two or more elements whose composition is constant. For example, table salt (sodium chloride -
NaCI) is a compound.
DESICCATOR (DESS-i-KAY-tor)	DESICCATOR
A closed container into which heated weighing or drying dishes are placed to cool in a dry environment. The dishes may be empty or
they may contain a sample. Desiccators contain a substance, such as anhydrous calcium chloride, which absorbs moisture and
keeps the relative humidity near zero so that the dish or sample will not gain weight from absorbed moisture.
DISTILLATE (DIS-tuh-late)	DISTILLATE
In the distillation of a sample, a portion is evaporated; the part that is condensed afterwards is the distillate.
ELEMENT	ELEMENT
A substance which cannot be separated into substances of other kinds by ordinary chemical means. For example, sodium (Na) is an
element.
END POINT	END POINT
Samples are titrated to the end point. This means that a chemical is added, drop by drop, to a sample until a certain color change
(blue to clear, for example) occurs which is called the END POINT of the titration. In addition to a color change, an end point may be
reached by the formation of a precipitate or the reaching of a specified pH. An end point may be detected by the use of an electronic
device such as a pH meter.
FACULTATIVE (FACK-ul-TAY-tive)	FACULTATIVE
Facultative bacteria can use either molecular (dissolved) oxygen or oxygen obtained from food material such as sulfate or nitrate
ions. In other words, facultative bacteria can live under aerobic or anaerobic conditions.
FLAME POLISHED	FLAME POLISHED
Melted by a flame to smooth out irregularities. Sharp or broken edges of glass (such as the end of a glass tube) are rotated in a
flame until the edge melts slightly and becomes smooth.
GRAB SAMPLE	GRAB SAMPLE
A single sample of wastewater taken at neither a set time nor flow.
GRAVIMETRIC	GRAVIMETRIC
A means of measuring/unknown concentrations of water quality indicators in a sample by WEIGHING a precipitate or residue of the
sample.
INDICATOR (CHEMICAL)	INDICATOR (CHEMICAL)
A substance that gives a visible change, usually of color, at a desired point in a chemical reaction, generally at a specified end point.
M OR MOLAR	M OR MOLAR
A molar solution consists of one gram molecular weight of a compound dissolved in enough water to make one liter of solution. A
gram molecular weight is the molecular weight of a compound in grams. For example, the molecular weight of sulfuric acid (H,S04)
is 98. A 1 M solution of sulfuric acid would consist of 98 grams of H2S04 dissolved in enough distilled water to make one liter of
solution.
MPN (EM-PEA-EN)	MPN
MPN is the Most Probable Number of coliform-group organisms per unit volume. Expressed as a density or population of organisms
per 100 ml.

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Laboratory 337
MENISCUS (meh-NIS-cuss)	MENISCUS
The curved top of a column of liquid (water, oil, mercury) in a small tube. When the liquid wets the sides of the container (as with
water), the curve forms a valley. When the confining sides are not wetted (as with mercury), the curve forms a hill or upward bulge.
WATER
Read
Bottom
lOi
MERCURY
Read
Top
Q

MOLECULAR WEIGHT	MOLECULAR WEIGHT
The molecular weight of a compound in grams is the sum of the atomic weights of the elements in the compound. The molecular
weight of sulfuric acid (H2S04) in grams is 98.
Element
H
S
O
Atomic Weight
1
32
16
Number of Atoms
2
1
4
Molecular Weight
2
32
64
98
MOLECULE (MOLL-uh-kule)
MOLECULE
A molecule is the smallest portion of an element or compound that still retains or exhibits all the properties of the substance.
N OR NORMAL	N OR NORMAL
A normal solution contains one gram equivalent weight of reactant (compound) per liter of solution. The equivalent weight of an acid
is that weight which contains one gram atom of ionizable hydrogen or its chemical equivalent. For example, the equivalent weight of
sulfuric acid (H2S04) is 49 (98 divided by 2 because there are two replaceable hydrogen ions). A 1 N solution of sulfuric acid would
consist of 49 grams of H2S04 dissolved in enough water to make one liter of solution.
OXIDATION (ox-i-DAY-shun)	OXIDATION
Oxidation is the addition of oxygen, removal of hydrogen, or the removal of electrons from an element or compound. In wastewater
treatment, organic matter is oxidized to more stable substances. The opposite of REDUCTION.
OXIDATION-REDUCTION POTENTIAL	OXIDATION-REDUCTION POTENTIAL
The electrical potential required to transfer electrons from one compound or element (the oxidant) to another compound or element
(the reductant) and used as a qualitative measure of the state of oxidation in wastewater treatment systems.
PERCENT SATURATION	PERCENT SATURATION
The amount of a substance that is dissolved in a solution compared with the amount that could be dissolved in the solution,
expressed as a percent.
Percent Saturation, %
Amount of Substance
That is Dissolved
Amount That Could Be
Dissolved in Solution
x 100%
pH (PEA-A-ch)
PH
pH is an expression of the intensity of the alkaline or acid condition of a water. Mathematically, pH is the logarithm (base 10) of the
reciprocal of the hydrogen ion concentration.
pH = Log
1
(H+)
The pH may range from 0 to 14, where 0 is most acid, 14 most alkaline, and 7 neutral. Natural waters usually have a pH between 6.5
and 8.5.
PLUG FLOW	PLUG FLOW
A type of flow that occurs in tanks, basins or reactors when a slug of wastewater moves through a tank without ever dispersing or
mixing with the rest of the wastewater flowing through the tank.
DIRECTION
OF FLOW
PLUG FLOW

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338 Treatment Plants
PRECIPITATE (pre-SIP-i-TATE)	PRECIPITATE
To separate (a substance) out in solid form from a solution, as by the use of a reagent. The substance precipitated.
REAGENT (re-A-gent)	REAGENT
A substance which takes part in a chemical reaction and is used to measure, detect, or examine other substances.
REDUCTION (re-DUCK-shun)	REDUCTION
Reduction is the addition of hydrogen, removal of oxygen, or the addition of electrons to an element or compound. Under anaerobic
conditions in wastewater, sulfate compounds or elemental sulfur are reduced to odor-producing hydrogen sulfide (H2S) or the
sulfide ion (S 2). The opposite of OXIDATION.
REPRESENTATIVE SAMPLE	REPRESENTATIVE SAMPLE
A portion of material or water identical in content to that in the larger body of material or water being sampled.
SOLUTION	SOLUTION
A liquid mixture of dissolved substances. In a solution it is impossible to see all the separate parts.
STANDARD SOLUTION	STANDARD SOLUTION
A solution in which the exact concentration of a chemical or compound is known.
STANDARDIZE	STANDARDIZE
(1)	To compare with a standard. In wet chemistry, to find out the exact strength of a solution by comparing with a standard of known
strength. This information is used to adjust the strength by adding more water or more of the substance dissolved.
(2)	To compare an instrument or device with a standard. This helps you to adjust the instrument so that it reads accurately or to
prepare a scale, graph or chart that is accurate.
SURFACTANT	SURFACTANT
Abbreviation for surface-active agent. The active agent in detergents that possesses a high cleaning ability.
TITRATE (TIE-trate)	TITRATE
To TITRATE a sample, a chemical solution of known strength is added on a drop-by-drop basis until a color change, precipitate, or
pH change in the sample is observed (end point). Titration is the process of adding the chemical solution to completion of the
reaction as signaled by the end point.
TURBIDITY UNITS	TURBIDITY UNITS
Turbidity units, if measured by a nephelometric (reflected light) instrumental procedure, are expressed in nephelometric turbidity
units (NTU). Those turbidity units obtained by other instrumental methods or visual methods are expressed in Jackson Turbidity
Units (JTU) and sometimes as Formazin Turbidity Units (FTU). The FTU nomenclature comes from the Formazin polymer used to
prepare the turbidity standards for instrument calibration. Turbidity units are a measure of the cloudiness of water.
VOLATILE (VOL-a-til)	VOLATILE
A volatile substance is one that is capable of being evaporated or changed to a vapor at relatively low temperatures.
VOLATILE ACIDS	VOLATILE ACIDS
Acids produced during digestion. Fatty acids which are soluble in water and can be steam-distilled at atmospheric pressure. Also
called "organic acids." Volatile acids are commonly reported as equivalent to acetic acid.
VOLATILE LIQUIDS	VOLATILE LIQUIDS
Liquids which easily vaporize or evaporate at room temperatures.
VOLATILE SOLIDS	VOLATILE SOLIDS
Those solids in water, wastewater, or other liquids that are lost on ignition of the dry solids at 550°C.
VOLUMETRIC	VOLUMETRIC
A means of measuring unknown concentrations of water quality indicators in a sample BY DETERMINING THE VOLUME of titrant or
liquid reagent needed to complete particular reactions.

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Laboratory 339
16.11 The Metric System
The metric system is based on the decimal system. All units
of length, volume, and weight (mass) use factors of 10 to ex-
press larger or smaller quantities of these units. The metric
system is used exclusively in the wastewater plant laboratory.
Below is a summary of metric and English unit names and
abbreviations.
Type of	English
Measurement System
Length
Volume
Weight
inch
feet
yard
quart
gallon
ounce
pound
Temperature Fahrenheit
Time	second
Metric
Name
meter
liter
gram
Celsius
second
Metric
Abbreviation
m
°C
sec
In the laboratory we sometimes use smaller amounts than a
meter, a liter, or a gram. To express these smaller amounts,
prefixes are added to the names of the metric units. There are
many prefixes in use; however, we commonly use two prefixes
more than any others in the laboratory.
Prefix
milli-
centi-
Abbreviation
m
c
Meaning
1/1000 of, OR 0.001 times
1/100 of, OR 0.01 times
One milliliter (ml) is 1/1000 of a liter and likewise one centi-
meter (cm) is 1/100 of a meter.
EXAMPLE
(1)	Convert 2 grams into milligrams.
1 milligram ^ 1 mg = 1/1000 g
therefore, 1 gram = 1000 milligrams
2 grams x 1000 mg/gram = 2000 mg
(2)	Convert 500 ml to liters.
1 ml = 1/1000 liter
therefore, 1 liter = 1000 ml
500 ml x 1 liter/1000 ml = 0.500 liters
The Celsius (or centrigrade) temperature scale is used in the
laboratory rather than the more familiar Fahrenheit scale.
Boiling point of water
Freezing point of water
Fahrenheit (°F) Celsius (°C)
212	100
32	0
To convert Fahrenheit to Celsius you can use the following
formula:
Temperature, °C = Jt (°F - 32)
EXAMPLE: Convert 68°F to °C.
Temperature, °C = JL (°F - 32)
Temperature, °C = ^ (68°F - 32)
9
Temperature, °C = 5 (36)
9
= 20°C
16.12 Chemical Names and Formulas
Chemical symbols are "shorthand" for the names of the
elements. Names and symbols for some of these elements are
listed below.
Chemical Name
Calcium
Carbon
Chlorine
Hydrogen
Iron
Oxygen
Potassium
Sodium
Sulfur
Symbol
Ca
C
CI
H
Fe
O
K
Na
S
Many different compounds can be made from the same two
or three elements, therefore you must read the formula and
name carefully to prevent errors and accidents. A chemical
formula is a "shorthand" or abbreviated way, to write the name
of a compound. For example, the name sodium chloride (table
salt) can be written "NaCI." Table 16.1 lists commonly used
chemicals found in the wastewater plant laboratory.
The following procedures are given to show the use of some
of the chemicals whose names and formulas you will see in
wastewater tests:
Dissolved Oxygen Procedure
". . . To 300 milliliter (ml) sample placed in a BOD bottle,
add 2 ml of manganous sulfate solution. Now add 2 ml of
alkaline iodine-sodium azide solution. Shake well and add 2
ml of concentrated sulfuric acid. Titrate with sodium thiosul-
fate solution until . .

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340 Treatment Plants
Preparation of Manganous Sulfate Solution
.. Weigh 480 grams (g) MnS04 • HzO and dissolve in
distilled water. Dilute to 1 liter..
BEAKERS. Beakers are the most common pieces of laboratory
equipment. They come in sizes from 1 ml to 4000 ml.
They are used mainly for mixing chemicals and to
measure approximate volumes.
Table 16.1 NAMES AND FORMULAS OF CHEMICALS
COMMONLY USED IN WASTEWATER
ANALYSES
Chemical Name
Ammonium chloride
Calcium chloride
(heptahydrate)*
Chloroform
Dipotassium hydrogen phosphate
Disodium hydrogen phosphate
(heptahydrate)*
Ferric chloride
Magnesium sulfate (heptahydrate)*
Manganous sulfate (tetrahydrate)*
Phenylarsine oxide
Potassium iodide
Sodium azide
Sodium chloride
Sodium hydroxide
Sodium iodide
Sodium thiosulfate (pentahydrate)*
Sulfuric acid
* Note that: tetra = 4, penta = 5, and hepta
7 H20
Chemical Formula
NH4CI
7 H20
CaCI2
CHCI3
K2HP04
NajHP04 • 7 H20
FeClj
MgS04 • 7 HjO
MnS04 • 4 H20
C6H5AsO
Kl
NaN,
NaCI
NaOH
Nal
Na2S203 5 H20
h2so4o
: 7, thus heptahydrate =
fh=^f
— «AML
RWLS--W
Beaker
GRADUATED CYLINDERS. Graduated cylinders also are
basic to any laboratory and come in sizes from 5 ml to
4000 ml. They are used to measure volumes more
accurately than beakers.
Cylinder,
Graduated
Poor results and safety hazards are often caused by using a
chemical from the shelf that is NOT the same chemical called
for in the procedure. This mistake usually occurs when the
chemicals have similar names or formulas. This problem can
be eliminated if you use BOTH the chemical name and formula
as a double check. As you can see in the table of chemical
names, the spellings of many chemicals are very similar.
These slight differences are critical because the chemicals do
not behave alike. For example, the chemicals potassium nit-
rate (KNO3) and potassium nitr/te (KNOz) are just as different
in meaning chemically as the words Mt and f/t are to your
doctor.
16.13 Laboratory Equipment
The equipment in a wastewater laboratory is the technician's
"tools-of-the-trade." In any laboratory there are certain pieces
of equipment that are used routinely to perform chemical tests
such as those in wastewater analyses. The pictures and
names of these are given with a statement concerning the use
of each piece.
PIPETS. Pipets are used to deliver accurate volumes and
range in size from 0.1 ml to 100 ml.
Pipet
(PIE-pet)
Volumetric
Pipet, Serological

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Laboratory 341
BURETS. Burets are also used to deliver accurate volumes.
They are especialy useful in a procedure called "titra-
tion." Burets come in sizes from 10 to 1000 ml.
FLASKS. Flasks are used for containing and mixing chemicals.
There are many different sizes and shapes.

0
Support, Buret
& Buret Clamp
Buret
(bur-RET)
Automatic
Buret
Flask,
Erlenmeyer
(ER-len-MY-er)
Wide Mouth
Flask,
Boiling
Round Bottom
Short Neck
l'-J
Flask,
Volumetric
I
55
Flask,
Boiling
Flat Bottom
Flask,
Filtering
Flask,
Distilling
Kjeldahl Flask
(Kell-doll)

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342 Treatment Plants
BOTTLES. Bottles are used to store chemicals, to collect sam-
ples for testing purposes, and to dispense liquids.
Separatory funnels are used to separate one chemi-
cal mixture from another. The separted chemical
usually is dissolved in one of two layers of liquid.
s

I
Bottle,
Reagent
w
v •/
101
Bottle,
BOD
Separatory Funnel
FUNNELS. A funnel is used for pouring solutions or transfer-
ring solid chemicals. This funnel also can be used
with filter paper to remove solids from a solution.
TUBES. Test tubes are used for mixing small quantities of
chemicals. They are also used as containers for
bacterial testing (culture tubes).
Funnel
J
-JJ
A Buchner funnel is used to separate solids from a
mixture. It is used with a filter flask and a vacuum.
Test Tube
Culture Tube
Without Lip
//
Funnel,
Buchner
With
Perforated Plate
Color Comparison
Tubes, Nessler

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Laboratory 343
IMHOFF CONE. The Imhoff cone is used for the settleable
solids testing of wastewater.
Cone,
Imhoff
(IM-hoff)
Cone Support
Hot Plate
OTHER LABWARE AND EQUIPMENT.


Condenser
^ bottom t K'K^ J'
Dish, Petri
Oven, Mechanical Convection
4.
¦¦¦ J
Desiccator
(DESS-i-KAY-tor)
Thermometer, Dial
Muffle Furnace, Electric

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344 Treatment Plants
Clamp, Dish,
Safety Tongs
Clamp
Clamp, Utility
Clamp, Beaker,
Safety Tongs
Tripod, Concentric
Ring
Burner, Bunsen
Clamp Holder
Triangle
Fused

-------
apcrs
Laboratory 345
Crucible,
Porcelain
Crucible,
Gooch
(GOO-ch)
Porcelain
Dish,
Evaporating
Test Paper, pH 1-11
Dissolved Oxygen Meter
Fume Hood
pH Meter	Pump, Air Pressure & Vacuum

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346 Treatment Plants
•:Mo
BOD Incubator

16.14 Use of Laboratory Glassware
BURETS
A buret is used to give accurate measurements of liquid
volumes. The stopcock controls the amount of liquid which will
flow from the buret. A glass stopcock must be lubricated (stop-
cock grease) and should not be used with alkaline solutions. A
teflon stopcock never needs to be lubricated.

stopcock
BURET
Burets come in several sizes, with those holding 10 or 25
milliliters used most frequently.
When a buret is filled with liquid, the surface of the liquid is
curved. This curve of the surface is called the meniscus (me-
NIS-cuss). Depending on the liquid, the curve may be up, as
with mercury, or down as with water. Since most solutions
used in the laboratory are water-based, always read the bot-
tom of the meniscus with your eye at the same level (Fig. 16.1).
If you have the meniscus at eye level, the closest marks that go
all the way around the buret will appear as straight lines, not
circles.

1
ill
I
Weight = 95.5580 gm.
• »-
•' Mi
H
Balance, Analytical
GRADUATED CYLINDERS
The graduated cylinder or "graduate" is one of the most
often used pieces of laboratory equipment. This cylinder is
made either of glass or of plastic and ranges in size from 10 ml
to 4 liters. The graduate is used to measure volumes of liquid
with an accuracy LESS than burets but GREATER than beak-
ers or flasks. Graduated cylinders should never be heated in
an open flame because they will break.

-------
Laboratory 347
pitopg? me.
dF VI^I4N






-------
348 Treatment Plants
FLASKS AND BEAKERS
Beakers and flasks are used for mixing, heating, and weigh-
ing chemicals. Most beakers and flasks are NOT calibrated
with exact volume lines; however, they are sometimes marked
with approximate volumes and can be used to estimate vol-
umes.
Flask
VOLUMETRIC FLASKS
Beaker
Volumetric flasks are used to prepare solutions and come in
sizes from 10 to 2000 ml. Volumetric flasks should NEVER be
heated. Rather than store liquid chemicals in volumetric flasks,
the chemicals should be transferred to a storage bottle.
PIPETS
Pipets are used for accurate volume measurements and
transfer. There are three types of pipets commonly used in the
laboratory — volumetric pipets, graduated or Mohr pipets, and
serological pipets.

Volumetric Pipet
—Inm	S.J/IQ
Graduated Pipet
Serological Pipet

Volumetric pipets are available in sizes such as 1, 10, 25,
50, and 100 ml. They are used to deliver a single volume.
Measuring and serological pipets, however, will deliver frac-
tions of the total volume indicated on the pipet.
In emptying volumetric pipets, they should be held in a verti-
cal position and the outflow should be unrestricted. The tip
should be touched to the wet surface of the receiving vessel
and kept in contact with it until the emptying is complete. Under
no circumstance should the small amount remaining in the tip
be blown out.
Measuring and serological pipets should be held in the verti-
cal position. After outflow has stopped, the tip should be
touched to the wet surface of the receiving vessel. No drainage
period is allowed. Where the small amount remaining in the tip
is to be blown out and added, indication is made by a frosted
band near the top of the pipet.
16.15 Solutions
Many laboratory procedures do not give the concentrations
of standard solutions in grams/liter or mg/liter. Instead, the
concentrations are given usually in normality (N).
EXAMPLES:
0.025 N H2S04 means a 0.025 normal solution of sulfuric
acid
2 N NaOH means that the normality of the sodium
hydroxide solution is 2
The LARGER the number in front of the N, the MORE con-
centrated the solution. For example, 1 N NaOH solution is
more concentrated than a 0.2 N NaOH solution.
When the exact concentration of a chemical or compound in
a solution is known, it is referred to as a "standard solution."
Many times standard solutions can be ordered already pre-
pared. Once a standard has been prepared, it can then be
used to standardize other solutions. To standardize a solution
means to determine its concentration accurately, thereby mak-
ing it a standard solution. "Standardization" is the process of
using one solution of known concentration to determine the
concentration of another solution and often involves a proce-
dure called a "titration."
16.16	Titrations
A titration involves the addition of one solution which is gen-
erally in a buret to another solution in a flask or beaker. The
solution in the buret is referred to as the "titrant" and is added
to the other solution until there is a measurable change in the
solution in the flask or beaker. This change is frequently a color
change as a result of the addition of a special chemical called
an "indicator" to the solution in the flask before the titration
begins. The solution in the buret is added slowly to the flask
until the change, which is called the "end point," is reached.
The entire process is a "titration."
16.17	Use of a Spectrophotometer
In the field of wastewater analysis, many determinations
such as phosphorus, nitrite and nitrate are based on measur-
ing the intensity of color at a particular wave length. The color
is formed in the sample by adding a specific developing rea-
gent to it. The intensity of the color formed is directly related to
the amount of material (such as phosphorus) in the sample.
For the analysis of phosphorus present in wastewater, for
example, ammonium molybdate reagent is added as the
developing reagent and if there is phosphorus present a blue
color developes. The more phosphorus there is, the deeper
and darker the blue color.

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Laboratory 349
The human eye can detect some differences in color inten-
sity; however, for very precise measurements an instrument
called a spectrophotometer is used.
THE SPECTROPHOTOMETER. A spectrophotometer is an
instrument generally used to measure the color intensity of a
chemical solution. A spectrophotometer in its simplest form
consists of a light source which is focused on a prism or other
suitable light dispersion device to separate the light into its
separate bands of energy. Each different wave length or color
may be selectively focused through a narrow slit. This beam of
light then passes through the sample to be measured. The
sample is usually contained in a glass tube called a cuvette
(QUE-vet). Most cuvettes are standardized to have a 1.0 cm
light path length, however many other sizes are available.
After the selected beam of light has passed through the
sample, it emerges and strikes a photoelectric cell. If the solu-
tion in the sample cell has absorbed any of the light, the total
energy content will be reduced. If the solution in the sample
cell does not absorb the light, then there will be no change in
energy. When the transmitted light beam strikes the photoelec-
tric tube, it generates an electric current that is proportional to
the intensity of light energy striking it. By connecting the photo-
electric tube to a galvanometer (a device for measuring electric
current) with a graduated scale, a means of measuring the
intensity of the transmitted beam is achieved.
The diagram below illustrates the working parts of a spec-
trophotometer.
Refracting
prism
White
light source
Sample	,
cuvette pn°to- _
electric
Exit	tube
slit


Galvanometer
The operator should always follow the working instructions
provided with the instrument.
UNITS OF SPECTROSCOPIC MEASUREMENT. The scale
on spectrophotometers is generally graduated in two ways:
(1)	in units of percent transmittance (%T), an arithmetic
scale with units graded from 0 to 100%; and
(2)	in units of absorbance (A), a logarithmic scale of non-
equal divisions graduated from 0.0 to 2.0.
Both the units percent transmittance and absorbance are
associated with the words color intensity. That is, a sample
which has a low color intensity will have a high percent trans-
mittance but a low absorbance.
TRANSMITTANCE
Absorbance
As illustrated above, the absorbance scale is ordinarily cali-
brated on the same scale as percent transmittance on spec-
trophotometers. The chief usefulness of absorbance lies in the
fact that it is a logarithmic function rather than linear (arithme-,
tic) and a law known as Beer's Law states that the concentra-
tion of a light absorbing colored solution is directly proportional
to absorbance over a given range of concentrations. If one
were to plot a graph showing %T or percent transmittance
versus concentration on straight graph or line paper and
another showing absorbance versus concentration on the
same paper, the following curves (graphs) would result:
k
O
c
m
€
o
n
<
.
-------
350 Treatment Plants
color developed by the unknown and locate it on the vertical
axis. Then a straight line is drawn to the right on the graph until
it intersects with the experimental standard curve. A line is then
dropped to the horizontal axis and this value identifies the
concentration of your unknown water quality indicator.
1.0
0.8
0.6
0.4
0.2
0.0
0.75
0.25
0.50
Concentration, mg/L
In this example, an absorbance reading of 0.32 was read on
the unknown solution or sample, which indicates a concentra-
tion of about 0.37 mgIL.
16.18 Laboratory Work Sheets and Notebooks
The plant operator has two goals in using a laboratory
notebook and worksheets: (1) to record data, and (2) to ar-
range data in an orderly manner. Often days of work can be
wasted if data are written down on a scrap of paper which is
usually misplaced or thrown away. Work sheets and
notebooks help prevent error and provide a record of the work.
The routine use of work sheets and notebooks is the only way
an operator can be sure that all important information for a test
is properly recorded.
There is no standard laboratory form. Most treatment plants
usually develop their own data sheets for recording laboratory
results and other important plant data. The data sheets are
prepared in a manner that makes it easy for you to record the
data, review it, and recover it when necessary. Each plant may
have different needs for collecting and recording data and
many plants may use from five to eight different data sheets.
Figures 16.2 and 16.3 illustrate typical laboratory work sheets
(sometimes called bench sheets).
Laboratory work sheets provide an organized method for
recording data. They are used to review effluent quality, iden-
tify problems and search for the cause of problems. These
sheets provide the information needed to complete NPDES
permit reporting forms.
16.19 Acknowledgment
Pictures of laboratory glassware and equipment in this man-
ual are reproduced with the permission of VWR Scientific, San
Francisco, California.
QUESTIONS
Write your answers in a notebook and then compare your
answers with those on page 458.
16.1 A For each of the items listed below, describe the item
and its use or purpose.
1.	Beakers
2.	Graduated Cylinders
3.	Pipets
4.	Burets
16.1B Why should graduated cylinders never be heated in an
open flame?
16.1C What is a bench sheet?
6KJP OF L6660M1 OF 91&660U4
ON
LAgOBAXoW
Work the discussion and review questions before continuing
with Lesson 2.

-------
PLANT
Laboratory 351
DATE 	
SUSPENDED SOLIDS & DISSOLVED SOLIDS
SAMPLE



Crucible
Sample, ml
Wt Dry & Dish, gm
Wt Dish, gm
Wt Dry, gm
mgii = Dfy. gm x 1,000,000
Sample, ml
Wt Dish & Dry, gm
Wt Dish & Ash, gm
Wt Volatile, gm
%Vnl = wtVo1 x inn%
Wt Dry




















































BOD
# Blank
SAMPLE			
DO Sample
Bottle #		
% Sample		
Blank or adj blank
DO after incubation
Depletion, 5 days		
Dep %
SETTLEABLE SOUDS
Sample, ml
Direct mlIL
COD
Sample
Blank Titration
Sample Titration
Depletion
_ Dep x N FAS x 8000
Sample, ml
Fig 16.2 Typical laboratory work sheet

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352 Treatment Plants
TOTAL SOLIDS
SAMPLE		
Dish No.
Wt Dish & Wet, gm
Wt Dish, gm
Wt. Wet, gm
Wt Dish + Dry, gm
Wt Dry, gm
% Solids = Wt Dry x 100%
Wt Wet			
Wt Dish + Dry, gm
Wt Dish + Ash, gm
Wt Volatile, gm
% Volatile = Wt Vo' x 100%
Wt Dry			
PH		
Vol. Acid, mgIL
Alkalinity as CaC03, mg/i.
Grease
Sample
Sample, ml
Wt Flask + Grease, mg
Wt Flask, mg		
Wt Grease, mg		
„ Wt Grease, mg x 1,000
mgIL =	
Sample, ml		
Fig. 16.3 Typical laboratory work sheet (continued)

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Laboratory 353
DISCUSSION AND REVIEW QUESTIONS
Chapter 16. LABORATORY PROCEDURES AND CHEMISTRY
(Lesson 1 of 9 Lessons)
At the end of each lesson in this chapter you will find some
discussion and review questions that you should answer be-
fore continuing. The purpose of these questions is to indicate
to you how well you understand the material in this lesson.
1.	Why must chemicals be properly labeled?
2.	How are pipets emptied or drained? Why is this procedure
important?
3.	How would you titrate a solution?
CHAPTER 16. LABORATORY PROCEDURES AND CHEMISTRY
(Lesson 2 of 9 Lessons)
16.2 SAFETY AND HYGIENE IN THE LABORATORY
Safety is just as important in the laboratory as in the rest of
the treatment plant. State laws and the Occupational Safety
and Health Act (OSHA) demand proper safety procedures to
be exercised in the laboratory at all times. OSHA specifically
deals with "safety at the place of work." The Act requires that
"each employer has the general duty to furnish all employees,
employment free from recognized hazards causing, or likely to
cause death or serious physical harm."
Personnel working in a wastewater treatment plant labora-
tory must realize that a number of hazardous materials and
conditions exist. Be alert and careful. Be aware of potential
dangers at all times. Safe practice in the laboratory requires
hardly any more effort than unsafe practice, and the important
results are prevention of injury or bodily damage.
On specific questions of safety, consult your state's General
Industrial Safety Orders or OSHA regulations.
16.20 Laboratory Hazards
Working with chemicals and other materials in the wastewa-
ter treatment plant laboratory can be dangerous. Dangers in-
clude:
Do not pipet wastewater or polluted samples by mouth. Pipet
both samples by mechanical means to avoid taking a chance
on severe illness or death.
Infectious Materials
Poisons
Explosions
Cuts and Bruises
Electrical Shock
Toxic Fumes
Fire
Burns
The above dangers to yourself and others can be minimized,
however, by using proper techniques and equipment.
16.200 Infectious Materials
Wastewater and sludge contain millions of biological or-
ganisms. Some of these are infectious and dangerous and can
cause diseases such as tetanus, typhoid, dysentery, and
hepatitis. Personnel handling these materials should thor-
oughly wash their hands with soap and water, particularly be-
fore handling food or smoking.
DON'T PIPET HAZARDOUS LIQUIDS
BY MOUTH.
Never drink from a beaker or other laboratory glassware. A
beaker left "specifically" for drinking is a menace to the labora-
tory.
Though not mandatory, inoculations by your local Health
Department are recommended for each employee.

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354 Treatment Plants
16.201	Corrosive chemicals
Acids
(1)	Examples: Sulfuric (H2S04), hydrochloric or muriatic (HCI),
nitric (NH03), glacial acetic (H4C202), and chromic acid.
(2)	Acids are extremely corrosive to human tissue, metals,
clothing, wood, cement, stone, and concrete.
(3)	Commercially available spill clean-up materials should be
kept on hand to neutralize acid in the event of an acciden-
tal spill.
Bases
(1)	Examples'. Sodium hydroxide (caustic soda or lye —
NaOH), potassium hydroxide (KOH), alkaline iodine —
sodium azide solution (used in the dissolved oxygen test).
(2)	Bases are extremely corrosive to skin, clothing, and
leather.
(3)	Commercially available spill clean-up materials should be
kept on hand for use in the event of an accidental spill.
Miscellaneous
(1) Examples: Chlorine, ferric salts (ferric chloride), and other
strong oxidants.
16.202	Toxic Materials
A.	Solids: Cyanide, chromium, orthotolidine, cadmium, and
other heavy metals.
B.	Liquids: Carbon tetrachloride, chloroform, ammonium
hydroxide, nitric acid, bromine, chlorine water, aniline
dyes, formaldehyde, and carbon disulfide. Carbon tet-
rachloride is absorbed into the skin on contact; its vapors
will damage the lungs; and it will build up in your body to a
dangerous level.
C.	Gases: Hydrogen sulfide, chlorine, ammonia, and sulfur
dioxide.
16.203	Explosive or Inflammable Materials
A.	Liquids: Carbon disulfide, benzene, ethyl ether, petroleum
ether, acetone, and gasoline.
B.	Gases: Acetylene apd hydrogen.
16.21 Personal Safety and Hygiene
16.210 Laboratory Safety
Laboratory work can be dangerous if proper precautions and
techniques are not taken. ALWAYS follow these basic rules:
1.	NEVER work alone in the laboratory. Someone should al-
ways be available to help you in case you should have an
accident which blinds you, leaves you unconscious, or
starts a fire you can't handle.
2.	Always wear protective goggles or eye glasses at all times
in the laboratory. Contact lenses should not be worn even
under safety goggles because fumes can seep between the
lens and the eyeball and irritate the eye.
3.	A face shield should be worn if there is any danger of a hot
liquid erupting from a container or flying pieces of
glassware from an exploded apparatus. If in doubt as to its
need — wear it!
4.	Always wear a lab coat or apron in the laboratory to protect
your skin and clothes.
5.	Protective gloves should be worn when handling hot
equipment or very cold objects, or when handling liquids or
solids which are skin irritants.
6.	Never eat or smoke in the laboratory. Never use laboratory
glassware for serving food or drinks.
7.	Don't keep your lunch in a refrigerator that is used for sam-
ple or chemical storage.
8.	Good housekeeping is the best way to prevent accidents.
16.211 Personal Hygiene
Although it is highly unlikely that personnel will contact dis-
eases by working in wastewater treatment plants, such a pos-
sibility does exist with certain diseases.
1. Some diseases are contracted through breaks in skin, cuts,
or puncture wounds. In such cases the bacteria causing the
disease may be covered over and trapped by flesh, creating
a suitable ANAEROBIC ENVIRONMENT2 in which the bac-
teria may thrive and spread throughout the body.
For protection against diseases contracted through
breaks in the skin, cuts, or puncture wounds, everyone
working in or around wastewater must receive immuniza-
tion from tetanus. Immunization must be received BEFORE
the infection occurs. To prevent diseases from entering
open wounds, care must be taken to keep wounds pro-
tected either with band aids or, if necessary, with rubber
gloves or waterproof protective clothing.
2 Anaerobic Environment (AN-air-O-bick). A condition in which "free" or dissolved oxygen is NOT present.

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Laboratory 355
2.	Diseases that may be contracted through the gastrointes-
tinal system or through the mouth are typhoid, cholera,
dysentery, amebiasis, worms, salmonella, infectious
hepatitis, and polio virus. These diseases are transmitted
when the infected wastewater materials are ingested or
swallowed by careless persons. The best protection against
those diseases is furnished by THOROUGH CLEANSING.
Hands, face, and body should be thoroughly washed with
soap and water, particularly the hands, in order to prevent
the transfer of any unsanitary materials or germs to the
mouth while eating.
A change of working clothes into street clothes before
leaving work is highly recommended to prevent carrying
unsanitary materials to your home. Personal hygiene, thor-
ough cleansing, and washing of the hands are effective
means of protection.
Immunization is provided for typhoid and polio. Little is
known about infectious hepatitis except that it can be
transmitted by wastewater. Hepatitis is frequently as-
sociated with gross wastewater pollution.
3.	Diseases that may be contracted by breathing contami-
nated air include tuberculosis, infectious hepatitis, and San
Joaquin fever. There has been no past evidence to indicate
the transmission of tuberculosis through the air at wastewa-
ter treatment plants. However, there was one case of tuber-
culosis being contracted by an employee who fell into
wastewater and, while swimming, inhaled wastewater into
his lungs. San Joaquin fever is caused by a fungus which
may be present in wastewater. However, there is no record
of operators contracting the disease while on the job.
The best insurance against these diseases is proper per-
sonal hygiene and immunization. Your plant should have an
immunization program against (1) tetanus, (2) typhoid, (3)
polio, and (4) smallpox (although smallpox is not related to
wastewater). The immunizations should be provided to protect
you. Check with your local or state health department for rec-
ommendations regarding immunization.
In the washing of hands, the kind of soap is less important
than the thorough use of the soap. (Special disinfectant soaps
are not essential.)
The use of protective clothing is very important, particularly
gloves and boots. The protection of wounds and cuts is also
important. Report injuries and take care of them.
The responsibility rests upon YOU.
There is no absolute insurance against contraction of dis-
ease in a wastewater treatment plant. However, the likelihood
of transmission is practically negligible. There appears to be no
special risk in working at treatment plants. In fact, operators
may develop a natural immunity by working in this environ-
ment.
16.22 Prevention of Laboratory Accidents
16.220 Chemical Storage
An adequate storeroom is essential for safety in the waste-
water laboratory. The storeroom should be properly ventilated
and lighted and be laid out to segregate incompatible chemi-
cals. Order and cleanliness must be maintained. All chemicals
and bottles or reagents should be clearly labeled and dated.
Never handle chemicals with bare hands. Use a spoon,
spatula, or tongs.
Heavy items should be stored on or as near to the floor as
possible. VOLATILE LIQUIDS3 which may escape as a gas,
such as ether, must be kept away from heat sources, sunlight,
and electrical switches.
CLAMPS, RAISED SHELF EDGES
AND PROPER ARRANGEMENT
PREVENT STOCKROOM FALLOUT.
Cylinders of gas in storage should also be capped and se-
cured to prevent rolling or tipping. They should also be placed
away from any possible sources of heat or open flames.
The usual common sense rules of storage should be fol-
lowed. Good housekeeping is a most significant contribution
toward an active safety campaign.
16.221 Movement of Chemicals
The next area of concern is the transfer of chemicals, ap-
paratus, gases, or other hazardous materials from the
storeroom to the laboratory for use. To facilitate handling, car-
boys or other larger chemical vessels, cradles or titters should
be used.
Drum Titter
In transporting cylinders of compressed gases, a trussed
handtruck should be used. Never roll a cylinder by its valve.
Immediately after they are positioned for use, cylinders should
be clamped securely into place to prevent shifting or toppling.
Flammable liquids should be carried in safety cans or, in the
case of reagent-grade chemicals, the bottle should be pro-
tected by a carrier. Protective gloves, safety shoes, and rubber
aprons should be worn in case of accidental spilling of chemi-
cal containers.
3 Volatile Liquids (VOL-a-till). Liquids which easily vaporize or evaporate at room temperatures.

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356 Treatment Plants
16.222	Proper Laboratory Techniques
Faulty technique is one of the chief causes of accidents and,
because it involves the human element, is one of the most
difficult to correct.
Because of their nature and prevalence in the laboratory,
acids and other corrosive materials constitute a series of
hazards ranging from poisoning, burning, and gasing through
explosion. Always flush the outsides of acid bottles before
opening them. Don't lay the stopper down on the counter top
where a person might lay a hand or rest an arm on it. Keep all
acids tightly stoppered when not in use and make sure no
spilled acid remains on the floor, table, or bottle after use. To
avoid splashing, don't pour water into acid; ALWAYS POUR
ACID INTO WATER.
Mercury requires special care. Even a small amount in the
bottom of a drawer can poison the atmosphere in a room. After
an accident involving mercury, the area should be gone over
carefully until there are no globules remaining. All mercury
containers should be kept well-stoppered.
16.223	Accident Prevention
ELECTRICAL SHOCK. Wherever thpre are electrical outlets,
plugs, and wiring connections, there is a danger of electrical
shock. The usual "do's" and "don'ts" of protection against
shock in the home are equally applicable in the laboratory.
Don't use worn or frayed wires. Replace connections when
there is any sign of thinning insulation. Ground all apparatus
using either three-prong plugs or pigtail adapters. Don't con-
tinue to run a motor after liquid has spilled on it. Turn it off
immediately and clean and dry the inside thoroughly before
attempting to use it again.
Electrical units which are operated in an area exposed to
flammable vapors should be explosion proof. All permanent
wiring should be installed by an electrician with proper conduit
or BX cable to eliminate any danger of circuit overloading.
CUTS. Some of the pieces of glass used in the laboratory,
such as glass tubing, thermometers, and funnels, must be in-
serted through rubber stoppers. If the glass is forced through
the hole in the stopper by applying a lot of pressure, the glass
usually breaks. This is one of the most common sources of
cuts in the laboratory.
Use care in making rubber-to-glass connections. Lengths of
glass tubing should be supported while they are being inserted
into rubber. The ends of the glass should be FLAME
POLISHED4 and either wetted or covered with a lubricating
jelly for ease in joining connections. Never use oil or grease.
Gloves should be worn when making such connections, and
the tubing should be held as close to the end being inserted as
possible to prevent bending or breaking.
Never try to force rubber tubing or stoppers from glassware.
Cut off the rubber or material.
A FIRST-AID kit must be available in the laboratory.
BURNS. All glassware and porcelain look cold after the red
from heating has disappeared. The red is gone in seconds but
the glass is hot enough to burn for several minutes. After heat-
ing a piece of glass, put it out of the way until cool.
Spattering from acids, caustic materials, and strong oxi-
dizing solutions should be washed off immediately with large
quantities of water. Every worker in the wastewater laboratory
should have access to a sink and an emergency deluge
shower.
Many safeguards against burns are available. Asbestos
gloves, safety tongs, aprons, and emergency deluge showers
are but a few examples. Never decide it is too much trouble to
put on a pair of gloves or use a pair of tongs to handle a dish or
flask that has been heated.
USE TONGS-DON'T IUGGLE
HOT CONTAINERS.
Perhaps the most harmful and painful chemical burn occurs
when small objects, chemicals or fumes get into your eye. You
should immediately flood your eyes with water or a special
"eye wash" solution from a safety kit or from an eyewash
station or fountain.
TOXIC FUMES. Use a fumehood for routine reagent prepa-
ration. Pick a hood that has adequate air displacement and
4 Flame Polished. Melted by a flame to smooth out irregularities. Sharp or broken edges of glass (such as the end of a glass tube) are rotated
in a flame until the edge melts slightly and becomes smooth.

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Laboratory 357
expels harmful vapors and gases at their source. An annual
check should be made of the entire laboratory building. Some-
times noxious fumes are spread by the heating and cooling
system of the building.
When working with chlorine and other toxic substances, al-
ways wear a self-contained breathing apparatus. If possible,
try to clear the atmosphere with adequate ventilation BEFORE
entry.
WASTE DISPOSAL. A good safety program requires con-
stant care in disposal of laboratory waste. Corrosive materials
should never be poured down a sink or drain. These sub-
stances can corrode away the drain pipe and/or trap. Corrosive
acids should be poured down corrosion resistant sinks and
sewers using large quantities of water to dilute and flush the
acid.
To protect maintenance personnel, separate covered con-
tainers should be used to dispose of broken glass.
U
DON'T POUR VOLATILE LIQUIDS
INTO THE SINK.
FIRE. The laboratory should be equipped with a fire blanket.
The fire blanket is used to smother clothing fires. Small fires
which occur in an evaporating dish or beaker may be put out by
covering the container with a glass plate, wet towel, or wet
blanket. For larger fires, or ones which may spread rapidly,
promptly use a fire extinguisher. Do not use a fire extinguisher
on small beaker fires because the force of the spray will knock
over the beaker and spread the fire. You should be familiar
with the operation and use of your fire extinguishers.
The use of the proper type extinguisher for each class of fire
will give the best control of the situation and avoid compound-
ing the problem. The class of fires given here is based on the
type of material being consumed.
Class A Fires: (For wood, paper, textiles, and similar materi-
als.) Use foam, water, carbon dioxide gas or almost any
kind of extinguisher.
CHOOSE AN EXTINGUISHER BY
CLASS OF FIRE DON'T GUESS.
Class B Fires: (For grease, oil, paint, and related materials.)
Use foam, dry chemical or vaporizing liquid extinguishers.
Class C Fires: (All fires in electrical equipment and in areas
where live electricity is present.) Use carbon dioxide, dry
chemical, or vaporizing liquid extinguishers only.
Class D Fires: (Fires involving sodium, zinc, magnesium, and
other elements.) These fires should be smothered with fine
dry soda ash, sand, or graphite.
16.23 Acknowledgments
Portions of this section were taken from material written by
A.E. Greenberg, "Safety and Hygiene," which appeared in the
California Water Pollution Control Association's OPERATORS'
LABORATORY MANUAL. Also some of the ideas and material
came from the FISHER SAFETY MANUAL
16.24 Additional Reading
1.	FISHER SAFETY MANUAL. Available from Fisher Scientific
Company, 711 Forbes Avenue, Pittsburgh, PA 15210. Price
$6.00.
2.	SAFETY IN THE CHEMICAL LABORATORY. Edited by
Norman V. Steere. 3 Volumes. Price $21.90. Order from
Journal of Chemical Education, Office of Publications
Coordinator, 238 Kent Road, Springfield, PA 19064.
3.	GENERAL INDUSTRY, OSHA SAFETY AND HEALTH
STANDARDS (29 CFR 1910), OSHA 2206, revised Janu-
ary 1976. Obtain from the Superintendent of Documents,
U.S. Government Printing Office, Washington, D.C. 20402.
Stock Number 029-015-00054-6. Price $6.50.

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358 Treatment Plants
QUESTIONS
Write your answers in a notebook and then compare your
answers with those on page 458.
16.2A Why should you always use a rubber bulb to pipei
wastewater or polluted water?
16.2B Why are inoculations against disease recommended
for people working around wastewater?
16.2C What would you do if you spilled a concentrated acid
on your hand?
16.2D True or False: You may ADD ACID to water, but never
water to acid.
6KJP OF LW'SOM 2 OF 9
ON
iA$?i?Af0Gv pQoceputeGuPtMm
Work the next portion of the discussion and review questions
before continuing with Lesson 3.
DISCUSSION AND REVIEW QUESTIONS
Chapter 16. LABORATORY PROCEDURES AND CHEMISTRY
(Lesson 2 of 9 Lessons)
Write the answers to these questions in your notebook. The	5. Why should work with certain chemicals be conducted
question numbering continues from Lesson 1. under a ventilated laboratory hood?
4. What precautions should you take to protect yourself from
diseases when working in a wastewater treatment plant?	6. Discuss the basic rules for working in a laboratory.

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Laboratory 359
CHAPTER 16. LABORATORY PROCEDURES AND CHEMISTRY
(Lesson 3 of 9 Lessons)
16.3 SAMPLING
16.30	Importance
The basis for any plant monitoring program rests upon in-
formation obtained by sampling. Decisions based upon incor-
rect data may be made if sampling is performed in a careless
and thoughtless manner. Obtaining good results will depend to
a great extent upon the following factors:
1.	Ensuring that the sample taken is truly representative of the
wastestream,
2.	Using proper sampling techniques, and
3.	Protecting and preserving the samples until they are
analyzed.
THE GREATEST ERRORS PRODUCED IN LABORATORY
TESTS ARE USUALLY CAUSED BY IMPROPER SAMPLING,
POOR PRESERVATION, OR LACK OF ENOUGH MIXING
DURING COMPOSITING5 AND TESTING.
16.31	Representative Sampling
You must always remember that wastewater flows can vary
widely in quantity and composition over a 24-hour period. Also,
composition can vary within a given stream at any single time
due to partial settling of solids or floating of light materials.
Samples should therefore be taken from the wastestream
where it is well mixed. Obtaining a representative sample
should be of major concern in any sampling and monitoring
program.
Laboratory equipment, in itself, is generally quite accurate.
Analytical balances weigh to 0.1 milligram. Graduated cylin-
ders, pipets, and burets usually measure to 1 percent accu-
racy, so that the errors introduced by these items should total
less than 5 percent, and under the worst possible conditions
only 10 percent. Under ideal conditions let us assume that a
test of raw wastewater for suspended solids should run about
300 mgIL. Because of the previously mentioned equipment or
apparatus variables, the value may actually range from 270 to
330 mg/L. Results in this range are reasonable for operation.
Other less obvious factors are usually present which make it
quite possible to obtain results which are 25, 50, or even 100
percent in error, unless certain precautions are taken. The
following example will illustrate how these errors areproduced.
The Dumpmore Wastewater Treatment Plant is a secondary
treatment facility with a flow of 8 million gallons per day. The
plant has an aerated grit basin, two circular primary clarifiers of
750,000 gallon capacity, two digesters, two aeration basins,
two secondary clarifiers, four chlorinators, and two chlorine
contact basins.
Monthly summary calculations based upon the suspended
solids test showed that about 8,000 pounds of suspended sol-
ids were being captured per day during primary sedimentation,
assuming 200 mg/L for the influent and 100 mg/L for the
effluent. However, it also appeared that 12,000 pounds per day
of raw sludge solids were being pumped out of the primary
clarifiers and to the digester. Obviously, if sampling and
analyses had been perfect, these weights would have been
balanced, provided the waste activated sludge was not re-
turned to the primary clarifiers. The capture should equal the
removal of solids. A study was made to determine why the
variance in these values was so great. It would seem logical to
expect that the problem could be due to (1) incorrect testing
procedures, (2) poor sampling, (3) incorrect metering of the
wastewater or sludge flow, or (4) any combination of the three
or all of them.
In the first case, the equipment was in excellent condition.
The operator was a conscientious and able person who was
found to have carried out the laboratory procedures carefully
and who had previously run successful tests on comparative
samples. It was concluded that the equipment and test proce-
dures were completely satisfactory.
A survey was then made to determine if sampling stations
were in need of relocation. By using Imhoff cones and running
settleable solids tests along the influent channel and the aer-
ated grit chamber, one could quickly recognize that the best
mixed and most representative samples were to be taken from
the aerated grit chamber rather than the influent channel.
The settleable solids ran 13 ml/L in the aerated grit chamber
against 10 ml/L in the channel. By the simple process of de-
termining the best sampling station, the suspended solids
value in the influent was corrected from 200 mg/L to the more
representative 300 mg/L. Calculations, using the correct fig-
ures, changed the solids capture from 8,000 pounds to 12,000
pounds per day and a balance was obtained.
This example clearly illustrates the importance of selecting a
good sampling point in securing a truly representative sample.
It emphasizes the point that EVEN THOUGH A TEST IS AC-
CURATELY PERFORMED, THE RESULTS MAY BE EN-
TIRELY ERRONEOUS AND MEANINGLESS INSOFAR AS
USE FOR PROCESS CONTROL IS CONCERNED, UNLESS
A GOOD REPRESENTATIVE SAMPLE IS TAKEN. FUR-
THERMORE, A GOOD SAMPLE IS HIGHLY DEPENDENT
UPON THE SAMPUNG STATION. Whenever possible, select
a place where mixing is thorough and the wastewater quality is
uniform. As the solids concentration increases, above about
200 mg/L, mixing becomes even more significant because the
wastewater solids will tend to separate rapidly with the heavier
solids settling toward the bottom, the lighter solids in the mid-
dle, and the floatables rising toward the surface. If, as is usual,
a one-gallon portion is taken as representative of a million-
gallon flow, the job of sample location and sampling must be
taken seriously.
16.32 Time of Sampling
Let us consider next the time and frequency of sampling. In
carrying out a testing program, particularly where personnel
and time are limited due to the press of operational respon-
sibilities, testing may necessarily be restricted to about one
test day per week. If you decide to start your tests early in the
5 Composite (Proportional) Samples (com-POZ-it). A composite sample is a collection of individual samples obtained at regular intervals,
usually every one or two hours during a 24-hour time span. Each individual sample is combined with the others in proportion to the flow when
the sample was collected. The resulting mixture (composite sample) forms a representative sample and is analyzed to determine the average
conditions during the sampling period.

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360 Treatment Plants
week by taking samples early on Monday morning, you may
wind up with some very odd results.
One such incident will be cited. During a test for SURFAC-
TANTS,6 samples were taken early on Monday morning and
rushed into the laboratory for testing. Due to the detention time
in the sewers, these wastewater samples actually represented
Sunday flow on the graveyard shift, the weakest wastewater
obtainable. The surfactant content was only 1 mgIL, whereas it
would usually run 8 to 10 mgIL. So, the time and day of sam-
pling is quite important. Samples should be taken to represent
typical weekdays or even varied from day to day within the
week for a good indication of the characteristics of the waste-
water.
16.33 Types of Samples
The two types of samples collected in treatment plants are
known as (1) grab samples, and (2) composite samples, and
either may be obtained manually or automatically.
GRAB SAMPLES
A grab sample is a single sample of wastewater taken at
neither a set time nor flow. The grab samples show the waste
characteristics at the time the sample fs taken. A grab sample
may be preferred over a composite sample when:
1.	The wastewater to be sampled does not flow on a continu-
ous basis,
2.	The wastewater characteristics are relatively constant,
3.	You wish to determine whether or not a composite sample
obscures extreme conditions of the waste, and
4.	The wastewater is to be analyzed for dissolved gases (DO),
coliforms, residual chlorine, temperature, and pH. (NOTE:
Grab samples for these water quality indicators may be
collected at set times or specific time intervals.)
COMPOSITE SAMPLES
Since the wastewater quality changes from moment to mo-
ment and hour to hour, the best results would be obtained by
using some sort of continuous sampler-analyzer. However,
since operators are usually the sampler-analyzer, continuous
analysis would leave little time for anything but sampling and
testing. Except for tests which cannot wait due to rapid chemi-
cal or biological change of the sample, such as tests for dis-
solved oxygen and sulfide, a fair compromise may be reached
by taking samples throughout the day at hourly or two-hour
intervals.
When the samples are taken, they should be refrigerated
immediately to preserve them from continued bacterial de-
composition. When all of the samples have been collected for
a 24-hour period, the samples from a specific location should
be combined or composited together according to flow to form
a single 24-hour composite sample.
To prepare a composite sample, (1) the rate of wastewater
flow must be known and (2) each grab sample must then be
taken and measured out in direct proportion to the volume of
flow at that time. For example, Table 16.2 illustrates the hourly
flow and sample volume to be measured out for a 12-hour
proportional composite sample.
Large wastewater solids should be excluded from a sample,
particularly those greater than one-quarter inch (6 mm) in di-
ameter.
A very important point should be emphasized. DURING
COMPOSITING AND AT THE EXACT MOMENT OF TESTING,
THE SAMPLES MUST BE VIGOROUSLY REMIXED7 SO
THAT THEY WILL BE OF THE SAME COMPOSITION AND AS
WELL MIXED AS WHEN THEY WERE ORIGINALLY SAM-
PLED. Sometimes such remixing may become lax, so that all
the solids are not uniformly suspended. Lack of mixing can
cause low results in samples of solids that settle out rapidly,
such as those in activated sludge or raw wastewater. Samples
must therefore be mixed thoroughly and poured quickly before
any settling occurs. If this is not done, errors of 25 to 50 per-
cent may easily occur. For example, on the same mixed liquor
sample, one person may find 3,000 mg/L suspended solids
while another person may determine that there are only 2,000
mg/L due to poor mixing. When such a composite sample is
tested, a reasonably accurate measurement of the quality of
the day's flow can be made.
If a 24-hour sampling program is not possible, perhaps due
to insufficient personnel or the absence of a night shift, single
representative samples should be taken at a time when typical
characteristic qualities are present in the wastewater. The
samples should be taken in accordance with the detention time
required for treatment. For example, this period may exist be-
tween 10 AM and 5 PM for the sampling of raw influent. If a
sample is taken at 12 Noon, other samples should be taken in
accordance with the detention periods of the serial processes
of treatment in order to follow this slug of wastewater or PLUG
FLOW.6 In primary settling, if the detention time in the pri-
maries is two hours, the primary effluent should be sampled at
2 PM. If the detention time in the succeeding secondary treat-
ment process required three hours, this sample should be
taken at 5 PM.
TABLE 16.2 DATA COLLECTED TO PREPARE PROPORTIONAL COMPOSITE SAMPLE

Flow



Flow


Time
MGD
Factor
Sample Vol
Time
MGD
Factor
Sample Vol
6 AM
0.2
100
20
12 N
1.5
100
150
7 AM
0.4
100
40
1 PM
1.2
100
120
a AM
0.6
100
60
2 PM
1.0
100
100
9 AM
1.0
100
100
3 PM
1.0
100
100
10 AM
1.2
100
120
4 PM
1.0
100
100
11 AM
1.4
100
140
5 PM
0.9
100
90
1140
A sample composited in this manner would total 1140 ml.
* Surfactant. Abbreviation for surface-active agent. The active agent In detergents that possesses a high cleaning ability.
7	NOTE: If the sample has a low buffer capacity and the real pH is 6.5 or less, vigorous shaking can cause a significant change in pH level.
8	Plug Flow. A type of flow that occurs in tanks, basins or reactors when a slug of wastewater moves through a tank without ever dispersing or
mixing with the rest of the wastewater flowing through the tank.

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Laboratory 361
16.34 Sludge Sampling
In sampling raw sludge and feeding a digester, a few impor-
tant points should be kept in mind as shown in the following
illustrative table.
For raw sludge pumped from a primary clarifier, the sludge
solids vary considerably with pumping time as shown by sam-
ples withdrawn every one-half minute in Table 16.3.
TABLE 16.3 DECREASE IN PERCENT TOTAL SOLIDS
DURING PUMPING


Cumulative
Pumping Time
Total Solids
Solids
In Minutes
Percent
Average
0.5
7.0
7.0
1.0
7.1
7.1
1.5
7.4
7.2
2.0
7.3
7.2
2.5
6.7
7.1
3.0
5.3
6.B
3 5
4.0
6.4
4.0
2.3
5.9
4.5
2.0
5.5
5.0
1.5
5.1
a.	Table 16.3 shows that the solids were heavy during the
first 2.5 minutes, and thereafter rapidly became thinner
and watery. Since sludge solids should be fed to a digester
with solids as heavy as possible and a minimum of water,
the pumping should probably have been stopped at about
3 minutes. After 3 minutes, the water content did become
greater than desirable.
b.	In sampling this sludge, the sample should be taken as a
composite by mixing small equal portions taken every 0.5
minutes during pumping. If only a single portion of sludge
is taken for the sample, there is a chance that the sludge
sample may be too thick or too thin, depending upon the
moment the sample is taken. A composite sample will pre-
vent this possibility.
c.	Remember that as a sludge sample stands, the solids and
liquid separate due to gasification and flotation or settling
of the solids, and that it is absolutely necessary to thor-
oughly remix the sample back into its original form as a
mixture before pouring it for a test.
d.	When individual samples are taken at regular intervals in
this manner, they should be carefully preserved to prevent
sample deterioration by bacterial action. Refrigeration is
an excellent method of preservation and is generally pref-
erable to chemicals. Chemicals may interfere with tests
such as biochemical oxygen demand (BOD) and chemical
oxygen demand (COD).
16.35 Sampling Devices
Automatic sampling devices are wonderful timesavers and
should be used where possible. However, as with anything
automatic, problems do arise and the operator should be
aware of potential difficulties. Sample lines to auto-samplers
may build up growths which may periodically slough off and
contaminate the sample with a high solids content. Very regu-
lar cleanout of the intake line is required.
Manual sampling equipment includes dippers, weighted bot-
tles, hand-operated pumps, and cross-section samplers. Dip-
pers consist of wide-mouth corrosion-resistant containers
(such as cans or jars) on long handles that collect a sample for
testing. A weighted bottle is a collection container which is
lowered to a desired depth. At this location a cord or wire
removes the bottle stopper so the bottle can be filled. Sampling
pumps allow the inlet to the suction hose to be lowered to the
sampling depth. Cross-sectional samplers are used to sample
where the wastewater and sludge may be in layers, such as in
a digester or clarifier. The sampler consists of a tube, open at
both ends, that is lowered at the sampling location. When the
tube is at the proper depth, the ends of the tube are closed and
a sample is obtained from different layers.
Many operators build their own sampler (Fig. 16.4) using the
material described below:
1.	SAMPLING BUCKET. A coffee can attached to an eight-
foot length of Vi-inch electrical conduit or a wooden broom
handle with a 1/4-inch diameter spring in a four-inch loop.
2.	SAMPLING BOTTLE. Plastic bottle with rubber stopper
equipped with two %-inch glass tubes, one ending near the
bottom of bottle to allow sample to enter and the other
ending at the bottom of the stopper to allow the air in the
bottle to escape while the sample is filling the bottle.
For sample containers, wide-mouth plastic bottles are rec-
ommended. Plastic bottles, though somewhat expensive ini-
tially, not only greatly reduce the problem of breakage and
metal contamination, but are much safer to use. The wide-
mouth bottles ease the washing problem. For regular samples,
sets of plastic bottles bearing identification labels should be
used.
16.36	Preservation of Samples
Sample deterioration starts immediately after collection for
most wastewaters. The shorter the time that elapses between
collection and analysis, the more reliable will be the analytical
results.
In many instances, however, laboratory analysis cannot be
started immediately due to the remoteness of the laboratory or
workload. A summary of acceptable EPA (U.S. Environmental
Protection Agency) methods of preservation appear in Table
16.4.
16.37	Quality Control in the Wastewater Laboratory
Having good equipment and using the correct methods are
not enough to ensure correct analytical results. Each operator
must be constantly alert to factors in the plant which can cause
poor data quality. Such factors include: sloppy laboratory tech-
nique, deteriorated reagents, poorly operating instruments,
and calculation mistakes.

-------
Treatment Plants
V2" Conduit
Length to Suit

Ji
V4" Spring to Retain Sample Bottle
Coffee Can
Quart
Plastic
Bottle
A
Rubber Stopper
J3	,
\l ;;/
Glass Tube Vent
tr
Glass Tube — Cut to
fit V2" from
bottom of bottle
Fig. 16.4 Dissolved oxygen sampling bottle

-------
Laboratory 363
TABLE 16.4 U.S. EPA RECOMMENDED PRESERVATION
METHODS FOR WATER AND WASTEWATER SAMPLES
Test
Acidity/Alkalinity
Preservation Method
Store at 4°C
Max. Recommended
Holding Time
24 hours


Ammonia
Add H2S04 to pH <2
Store at 4°C
24 hours
BOD
Store at 4°C
6 hours
COD
Add H2S04 to pH <2
7 days
Chloride
None required
7 days
Chlorine, residual
Det. on site
No holding
Cyanide
Add NaOH to pH >12
Store at 4°C
24 hours
Dissolved Oxygen
Det. on site
No holding
Fluoride
Store at 4°C
7 days
Mercury
Add HNO, to pH <2
38 days (in glass)
13 days (in plastic)
Metals
Add HN03 to pH <2
6 months
Nitrate
Add H2S04 to pH <2
Store at 4°C
24 hours
Nitrite
Store at 4°C
24 hours
Oil & Grease
Add H2S04 to pH<2
24 hours
Organic Carbon
Add H2S04 to pH <2
Store at 4°C
24 hours
pH
Store at 4°C
6 hours
Phenolics
Add H.PO. to pH <4
& 1.0 g CuSO*IL
Store at 4°C
24 hours
Phosphorus, ortho
Filter on site
24 hours
Phosphorus, total
Store at 4°C
24 hours
Solids
Store at 4°C
7 days
Specific Conductivity
Store at 4°C
24 hours
Sulfate
Store at 4°C
7 days
Sulfide
Add 2 mM M zinc
acetate & 1 ml 1 N
NaOH IL
Store at 4°C
24 hours
Temperature
Det. on site
No holding
T. KJeldahl Nitrogen
Add H2S04 to pH <2
Store at 4°C
24 hours
Turbidity
Store at 4°C
7 days
16.38	Summary
1.	Representative samples must be taken before any tests are
made.
2.	Select a good sampling location.
3.	Collect samples and, if necessary, properly preserve them.
4.	Mix samples thoroughly before compositing and at time of
test.
16.39	Additional Reading
1.	HANDBOOK FOR MONITORING INDUSTRIAL WASTE-
WATER, Center for Environmental Research Information,
U.S. Environmental Protection Agency, 26 West St. Clair
Street, Cincinnati, Ohio 45268.
2.	HANDBOOK FOR ANALYTICAL QUALITY CONTROL IN
WATER AND WASTEWATER LABORATORIES, Center for
Environmental Research Information, U.S. Environmental
Protection Agency, 26 West St. Clair Street, Cincinnati,
Ohio 45268.
QUESTIONS
Write your answers in a notebook and then compare your
answers with those on page 458.
16.3A What are the largest sources of errors found in labora-
tory results?
16.3B Why must a representative sample be collected?
16.3C How would you prepare a proportional composite
sample?
ewp 0F1B660W 3op 9 izzzowb
ON
exroGv pqocb pu eez
Work the next portion of the discussion and review questions
before continuing with Lesson 4.
DISCUSSION AND REVIEW QUESTIONS
Chapter 16. LABORATORY PROCEDURES AND CHEMISTRY
(Lesson 3 of 9 Lessons)
Write the answers to these questions in your notebook. The 8. How would you obtain a representative sample?
question numbering continues from Lesson 2.	„ ,, J
9. Under what conditions and why would you preserve a sam-
7. What is meant by representative sample?	pie?

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364 Treatment Plants
CHAPTER 16. LABORATORY PROCEDURES AND CHEMISTRY
(Lesson 4 of 9 Lessons)
16.4 LABORATORY PROCEDURES FOR PLANT
CONTROL
16.40 Clarity
A. DISCUSSION
All plant effluents should have a clarity reading taken at high
noon or some other specific time in order to compare results.
This test is based on how far you can see through your plant
effluent under similar conditions at the same time every day.
The objective of the test is to indicate the clearness or clarity of
the plant effluent. The test can be performed either in the lab
by looking down through the effluent in a graduated cylinder, or
in the field by looking down through the effluent in a clarifier or
chlorine contact basin. Sometimes this test is referred to as a
turbidity measurement, but you are interested in the clarity of
your effluent (also see Section 16.5, Procedure 19, "Turbidity
Test").
B.	WHAT IS TESTED?
Sample
Secondary Clarifiers:
Trickling Filter
Activated Sludge
Activated Sludge Blanket
in Secondary Clarifier
Chlorine Contact Basins
C.	APPARATUS
Common Range
(Field Test)
Poor Good
1 ft
3 ft
1 ft
3ft
3ft
6ft
4ft
6ft
1.	One clarity unit (Secchi (SECK-key) Disc) and attached
rope marked in one-foot units
2.	One 1000 ml graduated cylinder
D. REAGENTS
None
E.	PROCEDURES
1.	FIELD TEST. Tie end of marked rope to handrail where
tests will be run, for example, in final sedimentation
unit. Always take tests at the same time each day for
comparable results. Lower disc slowly until you just
lose sight of it. Stop. Bring up slowly until just visible.
Stop. Look at the marks on the rope to see the depth of
water that you can see the disc through. Bring up disc,
clean and store. RECORD RESULTS.
2.	LAB TEST. Use a clean 1000 ml graduate. Fill with a
well-mixed sample up to the 1000 ml mark. During
every test the same lighting conditions in the lab should
be maintained. Look down through the liquid in the cyl-
inder and read the last visible number etched on the
side of the graduate and RECORD RESULTS.
Whether you use one or both of these tests, you should run
each test at the same time every day and under similar condi-
tions for comparable results.
F.	TEST RESULTS
1.	Each foot of depth is better clarity with Secchi disc.
2.	Each 100 ml mark seen in depth is better clarity.
QUESTIONS
Write your answers in a notebook and then compare your
answers with those on page 459.
16.4A What does the clarity test tell you about the quality of
effluent?
16.4B What happens when you attempt to measure clarity
under different conditions, such as lighting and clarifier
loadings?
16.41 Hydrogen Sulfide (H2S)
The major portion of the sulfide content in wastewater is
produced in the conversion of sulfate (S04~2) to sulfide (S-z)
by bacteria found in the wastewater. Oxygen-reducing bac-
teria will use any available sulfur-containing compound as
food. This process can produce odorous reduced-sulfur
compounds, including hydrogen sulfide (H2S).
H2S production in wastewater can be controlled by up-
sewer maintenance which reduces H?S formation and, in
some cases, by the application of chemicals such as chlorine,
oxygen or hydrogen peroxide.
16.410 HjS In the Atmosphere
A. DISCUSSION
The rate of corrosion in the sewer collection system and
treatment plant is often directly related to the rate of HZS
production or the amount of H2S in the atmosphere. In addi-
tion, hydrogen sulfide gas is toxic to your respiratory system
and is both flammable and explosive under certain condi-
tions. The parts per milion (ppm) concentration of hydrogen

-------
Laboratory 365
sulfide in the sewer atmosphere is quite different from that IN
wastewater. A concentration of 1 mg/L (ppm) in turbulent
wastewater can quickly produce a concentration of 300 ppm
in an unventilated enclosed atmospheric space. The
minimum concentration of H2S in the atmosphere known to
cause death is 300 ppm.
B.	METHODS
Two examples of the methods available for testing H2S in
the atmosphere are listed below. The first method, using
paper tape or tiles with lead acetate will give a rough estimate
of H2S. The second method is a faster and more accurate
instrumental measurement of a hazardous level or of the ac-
tual concentration of sulfide present.
C.	WHAT IS TESTED?
Sample
Atmosphere in sewers,
outlets from force mains,
wet pits, pumping stations,
and influent areas to
treatment plant.
Common Range
1.	Lead Acetate Method
Not black in 24 hours =
Good, 24+ hr
Black in less than 1 hour
Bad, <1 hour
2.	H2S Detector Method
< 3 ppm = good
>10 ppm = toxic
D. APPARATUS
Method 1: Lead acetate paper or unglazed tile soaked in
lead acetate solution
Method 2: H2S Detectors or H2S Detector Tubes
These devices are available in three types:
(1)	Personal. Attach to your belt. These have
an alarm signal, but no meter or indicator
of level of H2S.
(2)	Portable. Carry by hand and place near
work site. These have an alarm signal and
meter indicating level of H2S.
(3)	Stationary. Install permanently in lift sta-
tions, gas compressor rooms and other
potentially dangerous areas. These have
an alarm signal and may have a meter
indicating level of HZS.
See Table 16.5 for a summary of manufactur-
ers of H2S detection devices and their
addresses.
E. REAGENTS
Method 1: Lead Acetate Solution, saturated. Dissolve 50
grams lead acetate in 80 ml distilled water.
F.
Method 2: No reagents are required.
PROCEDURE:
Method 1:
1.	Obtain pieces of unglazed tile or use lead acetate paper.
Cut tile with hacksaw into Vfe inch strips.
2.	Soak strips of tile or paper in lead acetate solution.
TABLE 16.5
Personal*
Dynamation
Lumldor
Bacharach
Enmet
(H2S)
TYPES AND MANUFACTURERS OF HjS
DETECTION DEVICES
Portable11
Ecolyzer
Gastech
Bacharach
BioMarine
Stationary6
Ecolyzer
Dictaphone
Bacharach
¦Attach to your belt. These have an alarm signal, but no meter or
indicator of level of H2S.
b Carry by hand and place near work site. These have an alarm
signal and meter indicating level of H.S.
c Stationary. Install permanently in lift stations, gas compressor
rooms and other potentially dangerous areas. These have an alarm
signal and may have a meter indicating level of H2S.
Bacharach Instrument Co.
2300 Leghorn Street
Mountain View, CA 94043
(415) 967-7221
BioMarine
45 Great Valley Corp. Center
Malvern, PA 19355
(215) 647-7200
Dictaphone
475 Ellis Street
Mountain View, CA 94043
(415) 968-8389
Dynamation
P.O. Box 2253
Ann Arbor, Michigan 48106
(313) 769-0573
Ecolyzer
Energetics Science Inc.
85 Executive Blvd.
Elmsford, New York 10523
(914) 592-3010
Enmet
2308 S. Industrial Highway
Ann Arbor, Michigan 48104
(313) 761-1270
GasTech
331 Fairchild Drive
Mountain View, CA 94043
(415) 967-6794
Lumidor
5364 NW 167th Street
Miami, Florida 33014
(305) 625-6511
3.	Dry tile in drying oven or air dry.
4.	An open manhole or any point where wastewater is ex-
posed to the atmosphere is a good test site. Drive a nail
between metal crown ring of manhole, concrete, or other
convenient place. Tie paper or tile with cotton string to nail.
Replace manhole cover and return in half an hour or less. If
tile is not black or substantially colored, return periodically
until black. If H,S is present as indicated by a color change,
then measure flow, temperature, pH, and BOD for further
evaluation of problem.
Method 2: The instructions are included with instrument.
G. CALCULATIONS
Method 1: None required.
Method 2: The instructions are included with instrument.

-------
366 Treatment Plants
(H2S)
16.411 HJS in Wastewater
A.	DISCUSSION
In sewers, when there is no longer any dissolved oxygen,
H2S tests are run to determine the rate of H2S increase as the
wastewater travels to a pumping station or treatment plant. If
the wastewater is exposed to the atmosphere, H2S will be
released and a typical rotten egg odor will be detected.
Anaerobic bacteria found in wastewater can liberate H2S from
the solids. When the gas leaves the wastewater stream, some
of it dissolves in the condensed moisture in the concrete.
Sulfur-oxidizing bacteria convert the hydrogen sulfide to sul-
furic acid which is very corrosive to concrete.
Not all odors in wastewater are from H2S, and there is no
correlation between H2S and other odors. The total H2S proce-
dure is good up to 18 mgIL, and higher concentrations must be
diluted before testing. H2S production can be controlled by
up-sewer maintenance which reduces H2S formation in the
wastewater and protects the collection system. In some severe
cases chemicals are applied to flows in the collection system
for H2S control. Chemicals used include chlorine, oxygen, or
hydrogen peroxide.
B.	WHAT IS TESTED?
F.	EXAMPLE
The instructions are in the kits.
G.	CALCULATIONS
The instructions are in the kits.
H.	ADDITIONAL READING
I.	STANDARD METHODS FOR THE EXAMINATION OF
WATER AND WASTEWATER, 14th Edition, 1976. Water
Pollution Control Federation, 2626 Pennsylvania Avenue,
N.W., Washington, D.C., 20037. See page 505. Price
$28.00 to WPCF members; $35.00 to others.
2. OPERATION AND MAINTENANCE OF WASTEWATER
COLLECTION SYSTEMS, prepared by Department of Civil
Engineering, California State University, Sacramento, 6000
J Street, Sacramento, California 95819. Price $30.00.
QUESTION
Write your answer in a notebook and then compare your
answer with the one on page 459.
Sample Wastewater From
the Following Locations
H,S Concentrations
Possible Results, mg IL
Good Bad
16.4C Why would you measure the H2S concentration
1. Wastewater?
Sewers
0.1
1
2. The atmosphere?
Outlets from force mains
0.1
1

Wet pits, pumping stations
0.1
0.5
16.42 Settleable Solids
Influents to treatment plants
0
0.5
A. DISCUSSION
All of the above locations should be sampled, if pertinent,
when using upstream H2S control in the collection system.
C.	APPARATUS
1. LaMotte-Pomeroy Sulfide Testing Kit to test:
a.	Total Sulfide
b.	Dissolved Sulfide
c.	Hydrogen Sulfide in Solution
Obtain from LaMotte Chemical Products Company.
Order by Code #46^30, $33, FOB, Post Office Box 329,
Chestertown, Maryland 21620.
2 OR Hach Hydrogen Sulfide Test Kit
Obtain from HACH Chemical Company. Order by Code
#2238-00, $41, Post Office Box 389, Loveland, Colorado
80537.
D.	REAGENTS
The reagents are included in the kits.
E.	PROCEDURE
The instructions are in the kits.
The settleable solids test measures the volume of settleable
solids in one liter of sample that will settle to the bottom of an
Imhoff Cone during a specific time period. The test is an indica-
tion of the volume of solids removed by sedimentation in
sedimentation tanks, clarifiers, or ponds. The results are read
directly in milliliters from the Imhoff Cone.
B.	WHAT IS TESTED?
Sample
Influent
Primary Effluent
Secondary Effluent
C.	APPARATUS
Common Ranges Found
8 mlIL weak wastewater
12 mlIL medium wastewater
20 mlIL strong wastewater
0.1 mlIL - 3 ml IL
Over 3 ml/L poor
Trace — 0.5 mlIL
Over 0.5 ml/L poor
1.	Imhoff Cones
2.	Rack for holding Imhoff Cones
3.	Glass stirring rod, or wire
4.	Time clock or watch

-------
Laboratory 367
D. Procedure
OUTLINE OF PROCEDURE
Gently Stir
Sides
Mix well and
pour 1 liter
into Imhoff
Cone.
1 Liter
Read
Sludge
Volume
Settle
45 Minutes
Settle
15 Minutes
1.	Thoroughly mix the wastewater sample by shaking and
immediately fill an Imhoff Cone to the liter mark.
2.	Record the time of day that the cone was filled. T =	
3.	Allow the waste sample to settle for 45 minutes.
4.	Gently stir sides of the cone to facilitate settling of material
adhering to the side of the cone.
5.	After one hour, record the number of milliliters of settieable
solids in the Imhoff Cone. Make allowance for voids among
the settled material. For example, if you read a sludge vol-
ume of 3.0 ml and voids or spaces in the sludge occupy
approximately 0.2 ml, record a sludge volume of 2.8 ml.
6.	Record the settieable solids as mlIL or milliliters per liter.
Settieable Solids, Influent = 	ml/L
Settieable Solids, Effluent = __	 ml//
Settieable Solids, Removal = 	mlIL
E. EXAMPLE
Samples were collected from the influent and effluent of a
primary clarifier. After one hour, the following results were re-
corded:
Influent
Effluent
F. CALCULATIONS
Settieable Solids, ml/L
12.0
0.2
1. Calculate the efficiency or percent removal of the above
primary clarifier in removing settieable solids.
% Removal
of Set Sol
(Infl. Set Sol, mlIL - Effl. Set Sol, ml/L)
Influent Set Sol, mlIL
12 ml/L - 0.2 ml/L vinMt
x 100%
11.6
12
98%
12 ml/L
x 100%
12.0
-0.2
11.8

12)11.8
108
1 00
96
(Settieable Solids)
2. Estimate the gallons per day of sludge pumped to a digest-
er from the above primary clarifier if the flow is 1 MGD (1
million gallons per day). In your plant, the Imhoff Cone may
not measure or indicate the exact performance of your
clarifier or sedimentation tank, but with some experience
you should be able to relate or compare your lab tests with
actual performance.
Sludge Removed by Clarifier, ml/L
= Influent Set Sol, ml/L - Effluent Set Sol, ml/L
= 12 ml/L - 0.2 ml/L
= 11.8 ml/L
To estimate the gpd (gallons per day) of sludge pumped to a
digester, use the following formula:
Sludge to Digester, gpd
= Total Set Sol Removed, ml/L x 1000 x Flow, MGD
_ 11 Q ml x 1000 mg x 1 M gal
M mg ml	day
= 11,800 gpd
This value may be reduced by 30 to 75 percent due to com-
paction of the sludge in the clarifier.
If you figure sludge removed as a percentage (1.18%), the
sludge pumped to the digester would be calculated as follows:
1.18%
100%
Sludge to Digester, gpd
Sludge to Digester, gpd
Flow of 1,000,000 gpd
1.18% x 1,000,000 gpd
100%
40
= 11,800 gpd
G. CLINICAL CENTRIFUGE
Settieable solids may also be measured by a small clinical
centrifuge. This method, however, should be used for plant
control only and not for NPDES monitoring. A mixed sample is
placed in 15 ml graduated centrifuge tubes and spun for 15
minutes. The solid deposition in the tip of the tube is compared
with a curve prepared by plotting settieable solids vs. cen-
trifuge solid deposition. This test provides a quick estimate of
the settieable solids.
QUESTION
Write your answer in a notebook and then compare your
answer with the one on page 459.
16.4D Estimate the volume of solids pumped to a digester in
gallons per day (gpd) if the flow is 1 MGD, the influent
settieable solids is 10 ml/L, and the effluent settieable
solids is 0.4 mlIL for a primary clarifier.
16.43 Suspended Solids
A. DISCUSSION
One of the tests run on wastewater is used to determine the
amount of material suspended within the sample. The result
obtained from the suspended solids test does not mean that all
of the suspended solids settle out in the primary clarifier or, for
that matter, in the final clarifier. Some of the particles are of
such size and weight that they will not settle without additional
treatment. Therefore, suspended solids are a combination of
settieable solids and those solids that remain in suspension.

-------
368 Treatment Plants
(Suspended Solids)
B. WHAT IS TESTED?
Sample
Influent
Primary Effluent
Secondary Effluent
Activated Sludge Tests
Mixed Liquor
Return or Waste Sludge
Digester Tests:
Supernatant
Common Ranges, mg/L
Weak 150 - 400+ Strong
Weak 60 - 150+ Strong
Good 10- 60+Bad
Depending on Type of Process
1000 - < 5,000
2000 - <12,000
3000 - <10,000
When supernatant suspended solids are greater than
10,000 mg/L, the total solids test is usually performed.
C.	APPARATUS
1.	Glass-fiber filter discs, 2.2 cm, Reeve Angel 394A, 984 H;
Gelman A, or Whatman GF/C
2.	Filter holder, Gooch crucible adapter
3.	Flask, suction
4.	Gooch crucibles, 25 ml
5.	Vacuum source
6.	Drying oven, 103 to 105°C
7.	Desiccator
8.	Analytical balance
D.	PROCEDURE
Preparation of Gooch Crucible
1.	Insert a 2.2 cm glass-fiber filter into 25 ml Gooch crucible
and center it.
2.	Apply suction. Wash filter with 100 ml of distilled water to
seat filter properly.
3.	Dry at 103°C for one hour. If volatile suspended solids are
to be determined, ignite crucible in muffle furnace for one
hour at 550°C.
4.	Cool in desiccator.
5.	Weigh crucible and record weight. (This is known as "tare
weight.")
Sample Analysis
6.	Depending on the suspended solids content, measure out
a 25, 50, or 100 ml portion of a WELL MIXED sample into a
graduated cylinder. Use 25 ml if sample filters slowly. Use
larger volumes of sample if sample filters easily, such as
secondary effluent. Try to limit filtration time to about 15
minutes or less. Wet prepared Gooch crucible with dis-
tilled water and apply suction.
7.	Filter sample through the Gooch crucible.
8.	Wash out dissolved solids on the filter with about 20 ml of
distilled water. (Use two 10 ml portions.)
9.	Dry crucible at 103°C for at least one hour. Some samples
may require up to three hours to dry if the residue is thick.
10.	Cook in desiccator for 20 to 30 minutes.
11.	Weigh crucible plus suspended solids.
12.	Repeat drying cycle until constant weight is attained or
until weight loss is less than 0.5 mg.
13.	Record weight:
Total weight	= ___	
Tare Weight	= 		
Solids Weight	= _____	
E. PRECAUTIONS
1.	Check and regulate the oven temperature at 103° to 105°C.
2.	Observe crucible and glass fiber for any possible leaks. A
leak will cause solids to pass through and give low results.
The glass-fiber filter may become unseated and leaky when
the crucible is placed on the filter flask. The filter should be
reseated by adding distilled water to the filter in the crucible
and applying vacuum before filtering the sample.
3.	Mix the sample thoroughly so that it is completely uniform in
suspended solids when measured into a graduated cylinder
BEFORE SAMPLE CAN SETTLE OUT. This is especially
true of samples heavy in suspended solids, such as raw
wastewater and mixed liquor in activated sludge which set-
tle rapidly. The test can be no better than the mix.
4.	A good practice is to prepare a number of extra Gooch
crucibles for additional tests if the need arises. If a test
result appears faulty or questionable, the test should be
repeated. Check filtration rate and clarity of water passing
through the filter.
F. EXAMPLE AND CALCULATIONS
This section is provided to show you the detailed calcula-
tions. After some practice, most operators use the lab work
sheet as shown at the end of the calculations.
CALCULATIONS FOR SUSPENDED SOLIDS TEST
(Or use lab work sheet at end of calculations)
EXAMPLE: Assume the following data.
Volume of sample = 50 ml
Recorded Weights
Crucible weight	21.6329 g
Crucible plus dry solids	21.6531 g
Crucible plus ash9	21.6360 g
1. Compute total suspended solids.
21.6531 g Weight of Crucible plus Dry Solids, grams
- 21.6329 g - Weight of Crucible, grams
= 0.0202 g = Weight of Dry Solids, grams
or
= 20.2 mg
1000 milligrams (mg) = 1 gram (g)
or
20.2 mg = 0.0202 g
Total
Suspended = Weight of Dry Solids, mg x 1000 mVL
Sample Volume, ml 4Q4
= 20.2 mg x
= 404 mg/L
1000 mlIL
50 ml
50)20200.
200
200
200
• Obtained by placing the crucible plus dry solids in a muffle furnace at 550°C for one hour. The crucible plus remaining aah are cooled and
weighed.

-------
Laboratory 369
(Suspended Solids)
OUTLINE OF PROCEDURE
fi'/.V.-.;.;
1. Insert
glass-
fiber
filter.
Filtering Flask
2. Seat filter by add-
ing distilled water
and applying vacuum.

n n n
3. Dry crucibles in oven
at 103°C.
6. Pour
measured
volume of
sample in
Gooch
crucible.
nnn,
4. Cool in desiccator.
nnn
7. Filter out suspended
solids with vacuum.
8. Wash graduate, crucible,
and filter with distilled
water to complete solids
transfer.
5. Weigh crucible just prior to using.
9. Dry crucibles plus
suspended solids
at 103°C.
11. Weigh crucible
plus suspended
solids.
nnn
10. Cool.

-------
370 Treatment Plants
(Suspended Solids)
2. Compute volatile or organic suspended solids.
21.6531 g
21.6360 g
0.0171 g
or
17.1 mg
Weight of Crucible plus Dry Solids, g
- Weight of Crucible plus Ash, g
= Weight of Volatile Solids, g
Volatile
Suspended = Weight of Volatile Solids, mg x 1000 mlIL
Sample Volume, ml
= 17.1 mg x 1000 ml /L
50 ml
= 342 mg IL
3. Compute the percent volatile solids.
(Weight Volatile, mg) 100%
342
50)17100
150
210
200
100
100
Volatile
Solids, %
Weight Total Dry Solids, mg
171 m9 x 100%
20.2 mg
84,7%
.8465
20.2)17.10
1616
940
808
1320
1212
1080
1010
The above calculations are also performed on a Laboratory
Work Sheet (Fig. 16.5, page 372) to illustrate the use of the
work sheet.
4. Compute fixed or inorganic suspended solids.
21.6360 g Weight of Crucible plus Ash, g
- 21.6329 g - Weight of Crucible, g
= 0.0031 g = Weight of Fixed Solids, g
or
= 3.1 mg
Fixed
Suspended _ Weight of Fixed Solids, mg x 1000 ml/L
Solids,	Sample Volume, ml
mg/L
3.1 mg x 1000 ml/L
50 ml
= 62 mgIL
To check your work:
Fixed Susp. Solids = Total Susp. Solids, mgIL - Volatile Susp.
Solids, mgIL
= 404 mg/Z. - 342 mgIL
= 62 mgIL (check)
5. Compute the percent fixed solids.
Fixed Solids, % = (Weight Fixed, mg) x 100%
Weight Total, mg
= 3-1 x 100%
20.2 mg
= 15.3%
404
-342
62
CALCULATIONS FOR OVERALL PLANT REMOVAL OF
SUSPENDED SOLIDS IN PERCENT
EXAMPLE: Assume the following data.
Influent suspended solids	202 mgIL
Primary Effluent suspended solids	110 mgIL
Secondary Effluent suspended solids	52 mgIL
Final Effluent suspended solids	12 mgIL
To calculate the percent removal or treatment efficiency for a
particular process or the overall plant, use the following for-
mula:
Removal, %
(Ln-out) x 100%
In
Compute percentage removed between influent and primary
effluent:
Removal, %
*ln " °ut> x 100%
In
(202 m9/l -110 mg/L) x 100%
202 mgIL
92
x 100%
202
= 45.5%
202
-110
92
Compute percentage removed between influent and sec-
ondary effluent:
Removal, %
= (|n ' 0ut> x 100%
In
= (202 mgIL - 52 mgIL) x 1(X)%
202 mgIL
= 150 x 100%	-74
202	202) 150.00
= 74%	Ull
860
808
202
-52
150
52
Compute percentage removed between influent and final
effluent (overall plant percentage removed):
Removal, %
= (|n ' 0ut) x 100%
In
. (202 mg/L • 12 mg/L) y ifVWL
202 mgIL
_ 190
x 100%
202
= 94.1% removal for the plant in suspended
solids
CALCULATIONS FOR POUNDS SUSPENDED SOLIDS
REMOVED PER DAY
EXAMPLE: Assume the following data.
Influent suspended solids = 200 mg/L
Effluent suspended solids = 10 mg/L
Flow in million gallons/day = 2 MGD
1 gallon of water weighs = 8.34 lbs

-------
Laboratory 371
Compute pounds suspended solids removed:
The general formula for computing pounds removed is
Material	(Concentration In, mg/L -
Removed, =	Concentration Out, mg/L)
lbs/day	x Flow, MGD x 8.34 lb/gal
= (200 mg/L - 10 mg/L) x 2 MGD x 8.34 lb/gal
= 190 x 2 x 8.34
= 3169 lbs/day of suspended
solids removed by plant
8.34
380
000
6672
2502
3169.20
DERIVATION
This section is not essential to efficient plant operation, but is
provided to furnish you with a better understanding of the cal-
culation if you are interested. For practical purposes,
1 mg/L
or
Therefore:
lbs
day
1 ppm or 1 part per million
1 mg/million mg, because 1 liter
1,000,000 mg
mg
M mg
lbs/day
M gal
day
lbs
gal
QUESTIONS
Write your answers in a notebook and then compare your
answers with those on pages 459 and 460.
16.4E Why does some of the suspended material in waste-
water fail to be removed by settling or flotation within
one hour?
16.4F Given the following data:
100 ml of sample
Crucible weight	19.3241 g
Crucible plus dry solids	19.3902 g
Crucible plus ash	19.3469 g
Compute
a.	Total suspended solids, mg/L
b.	Volatile suspended solids, mg/L
c.	Volatile solids, %
d.	Fixed suspended solids, mg/L
e.	Fixed solids, %
16.4G Suspended solids data from a wastewater treatment
plant are given below:
Influent suspended solids
Primary effluent SS
= 221 mg/L
= 159 mg/L
Final effluent SS
(Suspended Solids)
= 33 mg/L
Compute the percent removal of suspended solids by
the
a.	Primary clarifier,
b.	Secondary process (removal between primary
effluent and secondary effluent), and
c.	Overall plant.
16.4H If the data in problem 16.4G is from a 1.5 MGD plant,
calculate the pounds of suspended solids removed by
the
a.	Primary unit,
b.	Secondary unit, and
c.	Overall plant.
16.44 Total Sludge Solids (Volatile and Fixed)
A. DISCUSSION
Total solids are the combined amounts of suspended and
dissolved materials in the sample.
This test is used for wastewater sludges or where the solids
can be expressed in percentages by weight. The weight can be
measured on an inexpensive beam balance to the nearest .01
of a gram. The total solids are composed of two components,
volatile and fixed solids. Volatile solids are composed of or-
ganic compounds which are of either plant or animal origin.
Volatile solids in a treatment plant indicate the waste material
that may be treated by biological processes. Fixed solids are
inorganic compounds such as sand, gravel, minerals, or salts.
COMMON RANGE, % BY WEIGHT
Total Volatile Fixed
6% to 9%
2% to 5% 80% 20% ± 5%
1.5% to 3% 75% 25% ±5%
B. WHAT IS TESTED?
Sample
Raw Sludge
Raw Sludge plus Waste
Activated Sludge
Recirculated Sludge
Supernatant:
Good Quality, has
Suspended Solids
Poor Quality
Digested Sludge
to Air Dry
C. APPARATUS
1.	Evaporating dish
2.	Analytical balance
3.	Drying oven, 103° to 105°C
4.	Measuring device — graduated cylinder
5.	Muffle furnace, 550°C
75% 25% ± 6%
<1%
50%
50%

10%
>5%
50%
50%

10%
3% too Thin




to <8%
50%
50%

10%

-------
372 Treatment Plants
(Suspended Solids)
PLANT clean water		
DATE 		
SUSPENDED SOLIDS & DISSOLVED SOLIDS
SAMPLE
INFL.



Crucible
Sample, ml
Wt Dry & Dish, gm
Wt Dish, gm
Wt Dry, gm
mg/l = W Dry, gm x 1,000,000
Sample, ml
Wt Dish & Dry, gm
Wt Dish & Ash, gm
Wt Volatile, gm
% Vol = W Vo1 * irw/„
Wt Dry
#015






50






21.6531
21.6329






0.0202






404 mgIL




21.6531
21.6360






0.0171






84.7%






SAMPLE
DO Sample
Bottle #
% Sample
Blank or adj blank
DO after incubation
Depletion, 5 days
Dep %
SETTLEABLE SOUDS
Sample, ml
Direct mlIL
COD
Sample
Blank Titration
Sample Titration
Depletion
mg/i = Pep x A/ FAS x 8000
Sample, ml
BOD
* Rlnnk

















































Fig. 16.5 Calculation of solids content
on Laboratory Work Sheet

-------
Laboratory 373
(Total Sludge Solids —
Volatile and Fixed)
D. PROCEDURE
OUTLINE OF PROCEDURE
f
2. Cool
1. Ignite empty dish
in muffle furnace
3. Weigh
dish
7. Weigh dish
+ residue
4. Measure out
sludge
5. Evaporate water at
103-105°C
6. Cool dish
+ residue
1.	Dry the dish by ignition in a muffle furnace at 550°C for one
hour. Cool dish in desiccator.
2.	Tare the evaporating dish to the nearest 10 milligrams, or
0.01 g on a single pan balance. Record the weight as Tare
Weight =	gms.
3.	Weigh dish plus 50 to 100 ml of WELL MIXED sludge sam-
ple. Record total weight to nearest 0.01 gram as Gross
Weight =	gms.
4.	Evaporate the sludge sample to dryness in the 103°C dry-
ing oven.
5.	Weigh the dried residue in the evaporating dish to the
nearest 10 milligrams, or 0.01 g. Record the weight as Dry
Sample and Dish = 			 gms.
6.	Compute the net weight of the residue by subtracting the
tare weight of the dish from the dry sample and dish.

-------
374 Treatment Plants
(Total Sludge Solids —
Volatile and Fixed)
E. PRECAUTIONS
1.	BE SURE THAT THE SAMPLE IS THOROUGHLY MIXED
and is representative of the sludge being pumped. Gener-
ally, where sludge pumping is intermittent, sludge is much
heavier at the beginning and is less dense toward the end
of pumping. Take several equal portions of sludge at regu-
lar intervals and mix for a good sample.
2.	Take a large enough sample. Measuring a 50 or 100 ml
sample which is closely equal to 50 or 100 grams is rec-
ommended. Since this material is so heterogeneous (non-
uniform), it is difficult to obtain a good representative sam-
ple with less volume. Smaller volumes will show greater
variations in answers, due to the uneven and lumpy nature
of the material.
F. PROCEDURE FOR VOLATILE SOLIDS
(continue from total solids test)
3.	Control oven temperature closely at 103° to 105°C. Some
solids are lost at any drying temperature. Close control of
oven temperature is necessary because higher tempera-
tures increase the losses of volatile solids in addition to the
evaporated water.
4.	Heat dish long enough to insure evaporation of water, usu-
ally about 3 to 4 hours. If heat drying and weighing are
repeated, stop when the weight change becomes small per
unit of drying time. The oxidation, dehydration, and degra-
dation of the volatile fraction won't completely stabilize until
it is carbonized or becomes ash.
5.	Since sludge is so non-uniform, weighing on the analytical
balance should probably be made only to the nearest 0.01
grams or 10 milligrams.
OUTLINE OF PROCEDURE
JZZZ
I
2. Cool
1. Ignite dried solids
at 550°C
3. Weigh fixed solids
1.	Determine the total solids as previously described in Sec- 3. Cool in desiccator for about 30 minutes,
tion D.
2.	Ignite the dish and residue from total solids test at 550°C for
one hour or until a white ash remains.
4. Weigh and record weight of Dish Plus Ash = _____ g.

-------
Laboratory 375
G.	EXAMPLE
Weight of Dish (Tare)
Weight of Dish plus
Wet Solids (Gross)
Weight of Dish plus
Dry Solids
Weight of Dish plus Ash
H.	CALCULATIONS
= 20.31 g
= 70.31 g
= 22.81 g
= 20.93 g
See Laboratory Work Sheet (Fig. 16.6) or calculations
shown below.
1.	Find weight of sample.
Weight of Dish plus Wet Solids (Gross)
Weight of Dish (Tare)
Weight of Sample
2.	Find weight of total solids..
Weight of Dish plus Dry Solids
Weight of Dish (Tare)
Weight of Total Solids
= 70.31 g
= 20.31 g
= 50.00 g
= 22.81 g
= 20.31 g
2.50 g
TOTAL SOLIDS
(Total Sludge Solids —
Volatile and Fixed)
3. Find percent sludge.
Solids, %
= (Weight of Solids, g) 100%
Weight of Sample, g
= (2.50 g) 100%
50.00 g
= 5%
4. Find weight of volatile solids.
Weight of Dish plus Dry Solids
Weight of Dish plus Ash
Weight of Volatile Solids
= 22.81 g
= 20.93 g
= 1.88 g
Find percent volatile solids.
Volatile Solids, % = _ (Wei9ht of Volatile Solids' 1000/0
Weight of Total Solids, g
(1.88 g) 100%
2.50 g
= 76%
SAMPLE
Dish No.
Wt Dish & Wet, gm
Wt Dish, gm
Wt. Wet, gm
Wt Dish + Dry, gm
Wt Dish, gm
Wt Dry, gm
% Solids = m Pry x 100%
Wt Wet
Wt Dish + Dry, gm
Wt Dish + Ash, gm
Wt Volatile, gm
% Volatile = WtVolx_100%
Wt Dry
pH
Vol. Acid, mgIL
Alkalinity as CaCO,, mg/L
Grease
Sample
Sample, ml
Wt Flask + Grease, mg
Wt Flask, mg
Wt Grease, mg
mg/L = Wt Greasa' m9 * 1.000
Sample, ml
Fig. 16.6 Calculation of total solids on Laboratory Work Sheet
RAW





7





70.31
20.31





50.00





22.81
20.31





2.50





5.0%





22.81
20.93





1.88





76%
























-------
376 Treatment Plants
QUESTIONS	16.41 What is the origin of the volatile solids found in a diges-
ter?
Write your answers in a notebook and then compare your	x .
answers with those on page 460.	16.4J What is the significance of volatile solids in a treatment
plant?
BMP OF LB640N 4 OF 910660^4
ON
LAgoeAfoev peocepu&WMeMWM
Work the next portion of the discussion and review questions
before continuing with Lesson 5.
DISCUSSION AND REVIEW QUESTIONS
Chapter 16. LABORATORY PROCEDURES AND CHEMISTRY
(Lesson 4 of 9 Lessons)
Write the answers to these questions in your notebook. The
question numbering continues from Lesson 3.
10. Why must the clarity test always be run under the same
conditions?
11. Hydrogen sulfide is measured because it causes
12. What causes H2S formation in sewers?
13. Calculate the efficiency or percent removal by a primary
clarifier when the influent settleable solids are 10 ml/L and
the effluent settleable solids are 0.3 ml/L.
14. Why does the actual volume of sludge pumped from a
clarifier not agree exactly with calculations based on the
settleable solids test?
15.	Given the following data:
100 ml of sample
Crucible weight	19.9850 g
Crucible plus dry solids	20.0503 g
Crucible plus ash	20.0068 g
Compute:
1.	Total suspended solids
2.	Volatile suspended solids
3.	Percent volatile solids
16.	Estimate the pounds of solids removed per day by a pri-
mary clarifier if the influent suspended solids is 200 mgIL
and the effluent suspended solids is 120 mgIL when the
flow is 1.5 MGD.
17.	Why are solids only weighted to the nearest 0.01 gram
when determining the total volatile solids content of diges-
ters?

-------
Laboratory 377
CHAPTER 16. LABORATORY PROCEDURES AND CHEMISTRY
(Lesson 5 of 9 Lessons)
16.45 Tests for Activated Sludge Control
16.450 Settleability
A. DISCUSSION
This test is run on mixed liquor or return sludge and the
results are plotted on a graph (Fig 16.7). All pertinent informa-
tion is filled in for process control of aerators.
Time, minutes
Fig. 16.7 Settleabillty of activated sludge solids
Settleability is important in determining the ability of the sol-
ids to separate from the liquid in the final clarifier. The activated
sludge solids should be returned to the aeration tank, and the
quality of the effluent is dependent upon the absence of solids
flowing over the effluent weir.
The suspended solids test should be run on the same sam-
ple of mixed liquor that is used for the settleability test. This will
allow you to calculate the Sludge Volume Index (SVI) or the
Sludge Density Index (SDI) which are explained in the follow-
ing sections.
The 2000 ml graduate that is filled with mixed liquor in the
settleability test is supposed to indicate what will happen to the
mixed liquor in the final clarifier — the rate of sludge settling,
turbidity, color, and volume of sludge at the end of 60 minutes.
B. WHAT IS TESTED?
Sample
Mixed Liquor
Working Range
Depends on desirable mixed
liquor concentration
C.	APPARATUS
2000 ml graduated cylinder10
D.	REAGENTS
None
E. PROCEDURE
1. Mix sample and pour
into 2000 ml graduate.
OUTLINE OF PROCEDURE
2. Record settleable solids, %, at 5-minute intervals.
Sample
2000
ml or
100%
Time,
min.
1.	Collect a sample of mixed liquor or return sludge.
2.	Carefully mix sample and pour into 2000 ml graduate. Vig-
orous shaking or mixing tends to break up floe and pro-
duces slower settling or poorer separation.
3.	Record settleable solids, %, at regular intervals.
27%
60
™Mallory Direct Reading Settlometer (a 2 liter graduated cylinder approximately 5 inches (12.5 cm) in diameter and 7 inches (17.5 cm) high).
Obtain from SGA Scientific, Inc., 735 Broad Street, Bloomfleld, New Jersey 07003. Catalog No. JS-1035. Price $46.19 each.

-------
378 Treatment Plants
(Settleability - SVI)
F. EXAMPLE AND CALCULATION
The percent settling rate can be compared for the various
days of the week and with other measurements — suspended
solids, SVI, percent sludge solids returned, aeration rate, and
plant inflow. A very slow-settling mixed liquor usually requires
air and solids adjustment to encourage increased stabilization
during aeration. Both very rapidly settling and very slowly set-
tling mixed liquors can give poor effluent clarification.
16.451 Sludge Volume Index (SVI)
A. DISCUSSION
The Sludge Volume Index (SVI) is used to indicate the condi-
tion of sludge (aeration solids or suspended solids) for settlea-
bility in a secondary or final clarifier. The SVI is the VOLUME in
ml occupied by one gram of mixed liquor suspended solids
after 30 minutes of settling. It is a useful test to indicate
changes in sludge characteristics. The proper SVI range for
your plant is determined at the time your final effluent is in the
BEST condition regarding solids and BOD removals and clar-
ity.
B.	WHAT IS TESTED?
Sample
Aerator Solids or
Suspended Solids
C.	APPARATUS
Preferable Range, SVI
50 ml/gm -150 ml/gm
See Section 16.45, "Tests for Activated Sludge Solids,"
16.450, "Settleability," and Section 16.43, "Suspended Sol-
ids."
D.	REAGENTS
None
E.	PROCEDURE
See Sections on "Settleability" and "Suspended Solids."
F.	EXAMPLE
30-minute settleable solids test = 360 ml in 2000 ml
graduate or 18%
Mixed liquor suspended solids = 1500 mg/L
G. CALCULATIONS
Sludge Volume
Index, SVI
% Settleable Solids x 1000 mg/gm x 1000 ml/L
Mixed Liquor Suspended Solids, mg/L x 100%
% Settleable Solids x 10,000
Mixed Liquor Suspended Solids, mg/L
18 x 10,000
120
= 120 ml/gm
15)1800
15
30
30
16.452 Sludge Density Index (SDI)
A. DISCUSSION
The Sludge Density Index (SDI) is used in a way similar to
the SVI to indicate the settleability of a sludge in a secondary
clarifier or effluent. The calculation of the SDI requires the
same information as the SVI test.
SDI = m9^" of susPendecl solids in mixed liquor
mlIL of settled mixed liquor solids x 10
or
SDI
= 100/SVI
B.
WHAT IS TESTED?
Sample
Aerator Solids or
Suspended Solids
C. THROUGH G.
Preferable Range, SOI
0.6 gm/ml - 2.0 gm/ml
These items are not included because of their similarity to
the SVI test.
QUESTIONS
Write your answers in a notebook and then compare your
answers with those on page 460.
16.4K Why should you run settleability tests on mixed liquor?
16.4L What is the Sludge Volume Index (SVI)?
16.4M Why is the SVI test run?
16.4N What is the relationship between the Sludge Density
Index (SDI) and SVI?
16.453 Sludge Age
A. DISCUSSION
"Sludge age" is a control guide that is widely used and is a
rough indicator of the length of time a pound of solids is main-
tained under aeration in the system. The basis for calculating
the sludge age is weight of suspended solids in the mixed
liquor in the aeration tank divided by weight of suspended
solids added per day to the aerator.
Sludge Age,
days
Suspended Solids in Mixed Liquor, mg/L
x Aerator Volume in MG x 8.34 lbs/gal
SS in Primary Effluent, mgIL'
x Daily Flow, MGD x 8.34 lbs/gal
Any significant additional loading placed on the aerator by
the digester supernatant liquor must be added to the above
loadings by considering the additional flow (MGD) and concen-
tration (mg/L). The selection of the method of determining
sludge age is discussed in Chapters 8 and 11, "Activated
Sludge." Since this method is based on suspended solids, it.
should not be used if the soluble organic (BOD) portion of the
wastewater is more than 50 percent of the total organic (BOD)
component.
* NOTE: Sludge age is calculated by three different methods:
1.	Suspended solids in primary effluent, mg/L
2.	Suspended solids removed from primary effluent, mg/L, or pri-
mary effluent, suspended solids, mg/L - final effluent, suspended
solids, mg/L
3.	BOD or COD in primary effluent, mg/L

-------
Laboratory 379
(Sludge Age)
B. WHAT IS TESTED?
Sample
Suspended solids in aerator
and BOD or suspended solids
in primary effluent
Sludge age
Common Range, mg/L
Depends on process
Conventional process,
2.5 - 6 days
C.	APPARATUS
See Section 16.43, "Suspended Solids Test."
D.	REAGENTS
None
E.	PROCEDURE
See Section 16.43, "Suspended Solids Test."
F.	EXAMPLE
Suspended Solids in Mixed Liquor = 1500 mg/L
Aeration Tank Volume	= 0.50 MG
Suspended Solids in Primary Effl.	= 100 mg/L
Daily Flow	= 2.0 MGD
G.	CALCULATIONS
Susp. Solids in Mixed Liquor, mg/L
Sludge Age, = x Aerator VqI- mg x 8.34 lbs/gal
days Susp. Solids in Primary Effl., mg/L
x Flow, MGD x 8.34 lbs/gal
= Mixed Liquor Susp. Solids, lbs
Primary Effluent SS, lbs/day
= 1500 mg/L x 0.50 MG x 8.34 lbs/gal
100 mg/L x 2.0 MGD x 8.34 lbs/gal
= 1500 x 0.50
100 x 2.0
_ 7.5
2.0
= 3.75 days
QUESTION
Write your answer in a notebook and then compare your
answer with the one on page 460.
16.40 Determine the sludge age in an activated sludge pro-
cess if the volume of the aeration tank is 200,600 gal-
lons and the suspended solids in the mixed liquor
equals 2000 mg/L. The primary effluent SS is 115
mg/L, and the average daily flow is 1.8 MGD.
16.454 Dissolved Oxygen in Aerator
A. DISCUSSION
This modification is used for biological floes that have high
oxygen utilization rates in the activated sludge process, and
when a DO probe is not available. It is very important that
some oxygen be present in aeration tanks at all times to main-
tain aerobic conditions.
This test is similar to the regular DO test (Section 16.5,
Procedure 7) except that copper sulfate is added to kill
oxygen-consuming organisms, and sulfamic acid is added to
combat nitrite before the regular DO test is run.
NOTE: IF THE RESULTS INDICATE A DO OF LESS THAN 1
MGIL, IT IS POSSIBLE THAT THE DO IN THE AER-
ATION TANK IS ZERO! When the DO in the aeration
tank is near zero, considerable DO from the surround-
ing atmosphere can mix with the sample when it is
collected, when the inhibitor is added, while the solids
are settling, and when the sample is transferred to a
BOD bottle for the DO test. If you use this test, use a
deep container and avoid stirring. See article by
Hughes and Reynolds, JWPCF, Vol. 41, pg. 184,
January 1969, for a discussion of the shortcomings of
this test.
B. WHAT IS TESTED?
Sample
Aerator Mixed Liquor
Common DO Range, mg/L
0.1 - 3.0
C.	APPARATUS
1.	One tall bottle, approximately 1000 ml
2.	Regular DO apparatus
D.	REAGENTS
1.	Copper sulfate-sulfamic acid inhibitor solution. Dissolve 32
g technical grade sulfamic acid (NH2SOzOH) without heat
in 475 ml distilled water. Dissolve 50 g copper sulfate,
CuS04 • 5 H20, in 500 ml water. Mix the two solutions
together and add 25 ml concentrated acetic acid.
2.	Regular DO reagents (See Section 16.5, Procedure 7).

-------
380 Treatment Plants
(DO in Aerator)
E. PROCEDURE
OUTLINE OF PROCEDURE
1.
Add 10 ml of
inhibitor to
DO sampling
bottle (Fig.
16.4, page
362).
2.
Dip into mixed
liquor and let
sampling bottle
fill. Stopper
bottle.
Remove glass
tube and
stopper and
allow floe
to settle.
Siphon over
300 ml of
sample into
BOD bottle.

5. Test
1.	Add at least 10 ml of inhibitor (5 ml copper sulfate and 5 ml
sulfamic acid) to any TALL bottle (1-quart milk bottle) with
an approximate volume of 1000 ml. Place filling tube near
the bottom. An emptying tube is placed approximately 1/4
inch from the top of the bottle cork. Attach bottle to rod or
aluminum conduit and lower into aeration tank. See Figure
16.4 on page 362.
2.	Submerge bottle 1.5 to 2.0 feet (0.45 to 0.60 m) below the
surface of the aerator and allow bottle to fill with mixed
liquor. Remove bottle from aeration tank.
3.	Remove glass tube and stopper from bottle. Insert lid in
bottle. Allow bottle to stand until solids (floe) settles and
leaves a clear supernatant liquor. Siphon the supernatant
liquor into a 300 ml BOD bottle. Do not aerate in transfer.
4.	Perform regular DO test.
F. and G. EXAMPLE AND CALCULATIONS
Same as regular DO test (see Section 16.5, page 426).
QUESTION
Write your answer in a notebook and then compare your
answer with the one on page 460.
16.4P What are the limitations of the copper sulfate-sulfamic
acid procedure for measuring DO in the aeration tank
when the DO in the tank is very low?
16.455 Suspended Solids In Aerator
Centrifuge Method
A. DISCUSSION
This procedure is frequently used in plants as a quick and
easy method to estimate the suspended solids concentration
of the mixed liquor in the aeration tank instead of the regular
suspended solids test. Many operators control the solids in
their aerator on the basis of centrifuge readings. Others prefer
to control solids using Fig. 16.8. In either case, the operator
should periodically compare centrifuge readings with values
obtained from suspended solids tests. If the solids are in a
good settling condition, a one percent centrifuge solids reading
could have a suspended solids concentration of 1000 mg/L.
However, if the sludge is feathery, a one percent centrifuge
solids reading could have a suspended solids concentration of
600 mg/L
The centrifuge reading versus mg/L suspended solids chart
(Fig. 16.8) must be developed for each plant by comparing
centrifuge readings with suspended solids determined by the
regular Gooch crucible method. The points are plotted and a
line of best fit is drawn as shown in Fig. 16.8. This line must be
periodically checked by comparing centrifuge readings with
regular suspended solids tests because of the large number of
variables influencing the relationship, such as characteristics
of influent waste, mixing in aerator, and organisms in aerator. If
you don't have a centrifuge or if your solids content is over
1500 mg/L, determine suspended solids by the regular
method.
B.	WHAT IS TESTED?
Sample
Suspended Solids in
Aeration Tanks
C.	APPARATUS
1.	Centrifuge
2.	Graduated centrifuge tubes, 15 ml
D.	REAGENTS
None
Common Range
800 - 5000 mg/L

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200
300
400
500	600	700
Suspended Solids (mg/1)
800
900'
1000
Fig. 16.8 Plant control by centrifuge solids in aeration tank, centrifuge speed, 1750 RPM

-------
382 Treatment Plants
(Suspended Solids - Centrifuge)
E.	PROCEDURE
1.	Collect sample in regular sampling can.
2.	Mix sample well and fill each centrifuge tube to the 15 ml
line with sample.
3.	Place filled sample tubes in centrifuge holders.
4.	Crank centrifuge at fast speed as you count slowly to 60. Be
sure to count and crank at the same speed for all tests. It is
extremely important to perform each step exactly the same
every time.
5.	Remove one tube and read the amount of suspended solids
concentrated in the bottom of the tube. This reading will be
1/10 of ml. Results in other tubes should be compared.
6.	Refer to the conversion curve to determine suspended sol-
ids in mg/L.
NOTE: The reason for filling tubes to the 15 ml mark is that
the curve (Fig. 16.8) is computed for samples of this
size. This curve was developed for a specific mechan-
ically aerated activated sludge plant. Seven hundred
to nine hundred mg/L MLSS is the best range for this
plant. Each plant must develop its own curve based
on actual data.
F.	EXAMPLE
Suspended solids concentration on bottom of centrifuge
tube is 0.4 ml.
G.	CALCULATIONS
From Fig. 16.8, find 0.4 ml on centrifuge reading side and
follow line horizontally on line on chart. Drop downward from
line on chart to mg/L suspended solids and read result of 900
mg/L.
If the suspended solids concentration is above or below the
desired range, then you should make the proper changes in
the pumping rate of the waste and return sludge. For details on
controlling the solids concentration, refer to Chapters 8 and 11,
"Activated Sludge."
H.	DEVELOPMENT OF FIG. 16.8
To develop Fig. 16.8, take a sample from the aeration tank
and measure suspended solids and also centrifuge a portion of
the sample to obtain the centrifuge sludge reading in ml of
sludge at the bottom of the tube. Obtain other samples of
different solids concentrations to obtain the points on the
graph. Draw a line of best fit through the points. Periodically
the points should be checked because the influent characteris-
tics and conditions in the aeration tank change.
I.	PRECAUTIONS
This test works best for low mixed-liquor suspended solids
(MLSS) concentrations below 1500 mg/L. Above 1500 mg/L
the centrifuge results might not allow an accurate estimate of
the MLSS.
QUESTION
Write your answer in a notebook and then compare your
answer with the one on page 460.
16.4Q What is the advantage of the centrifuge test for deter-
mining suspended solids in an aeration tank in com-
parison with other methods of measuring suspended
solids?
16.456 Mean Cell Residence Time (MCRT)
A. DISCUSSION
The mean cell residence time (MCRT) is in a sense a much
more precise "sludge age" calculation. MCRT describes the
mean (average) residence time of an activated sludge particle
in the activated sludge system and is a true measure of the age
of the activated sludge. MCRT considers the solids removed
from the process by wasting and the solids in the effluent and
also the solids in the system. To use MCRT for the control of
an activated sludge process, several measurements are re-
quired. Representative composite samples of mixed liquor,
suspended solids, effluent suspended solids, and waste
sludge suspended solids, are essential. Also measure influent
and waste sludge flows.
B. WHAT IS TESTED?
Sample	Common Range, Days
Mean Cell Residence Time	5 to 15 days
(MCRT)
C. APPARATUS AND REAGENTS
See Section 16.43 for volatile suspended solids test proce-
dures.
D. PROCEDURE
To calculate MCRT the following data are required:
1.	Influent flow, MGD
2.	Waste sludge flow, MGD
3.	Volume of aeration basins in million gallons
4.	Mixed liquor volatile suspended solids concentration in
mg/L
5.	Effluent volatile suspended solids in mg/L
6.	Waste sludge volatile suspended solids in mg/L
E. EXAMPLE
Influent Flow, Q
= 3 MGD
Waste Sludge Flow, W
= 0.040 MGD
Volume of Aeration Basins, V
= 1.0 MG
Mixed Liquor Suspended Solids

Concentration, X,
= 1600 mg/L
Effluent Suspended Solids, X2
= 0 mg/L
Waste Sludge Suspended Solids, Xw
= 4700 mg/L
F. CALCULATIONS
Mean Cell Residence _	(V, MG) (X,, mg/L)
Time' day®	(Q, MOD) (X2, mg/L) + (W, MGD) (Xw, mg/i.)
MCRT, days	=	(1.0 MG) (1600 mg/L)
(3 MGD) (8 mg/L) + (0.040 MGD) (4700 m(jIL)
1600
24 + 186
= 7.5 days

-------
Laboratory 383
NOTE: The mixed liquor, effluent and waste sludge VOL-
ATILE suspended solids may be used instead of
suspended solids to calculate the MCRT. See Chap-
ter 11, "Activated Sludge," Section 11.73, "Mean
Cell Residence Time (MCRT)" for a discussion of
ways to calculate MCRT.
QUESTION
Write your answer in a notebook and then compare your
answer with the one on page 460.
16.4R What measurements are required in order to calcu-
late the Mean Cell Residence Time (MCRT)?
16.46 Tests for Digestion Control
16.460 Volatile Acids
A. DISCUSSION
Volatile acid levels are determined on sludge samples from
the digesters. Most modern digesters have sampling pipes
where you can draw a sample from various levels of the tank.
Be sure to allow the sludge in the line to run for a few minutes
in order to obtain a representative sample of the digester
contents. Samples also may be collected from supernatant
draw-off tubes, or THIEF HOLES.11
Increased concentrations of volatile acids and decreased
alkalinity are the first measurable changes that take place
when the process of digestion is becoming upset. The volatile
acid/alkalinity relationship can vary from 0.1 to about 0.5
without significant changes in digester performance. When
the relationship starts to increase, this is a warning that un-
desirable changes will occur unless the increase is stopped.
If the relationship increases above 0.5, the composition of the
gas produced can change very rapidly, followed by changes
in the rate of gas production, and finally pH.
In a healthy and properly functioning digester, the pro-
cesses or biological action taking place inside the digester
are in equilibrium. When fresh sludge is pumped into a diges-
ter, some of the organisms in the digester convert this mate-
rial to volatile (organic) acids. In a properly operated digester,
other organisms feed on the newly produced volatile acids
and eventually convert the acids to methane (CH4) gas,
which is burnable, and carbon dioxide (C02). If too much raw
sludge is pumped to the digester or the digester is not func-
tioning properly, an excess of volatile acids is produced. If
excessive amounts of volatile acids are produced, an acid
environment unsuitable for some of the organisms in the di-
gester will develop and the digester may cease to function
properly unless the alkalinity increases too.
Routine volatile acids and alkalinity determinations during
the start-up process for a new digester are a must in bringing
the digester to a state of satisfactory digestion.
Routine volatile acids and alkalinity determinations during
digestion are important in providing the information which will
enable the operator to determine the health of the digester.
(Volatile Acids)
For digester control purposes, the volatile acid/alkalinity
relationship should be determined. When the volatile acid/
alkalinity relationship is from less than 0.1/1.0 to 0.5/1.0, the
loading and seed retention of the digester are under control.
When the relationship starts increasing and becomes greater
than 0.5/1.0, the digester is out of control and will become
"stuck" unless effective corrective action is taken.
B.	WHAT IS TESTED?
Sample	Desirable Range
Recirculated Sludge	150 - 600 mg/L
(expect trouble if alka-
linity less than two times
volatile acids)
METHOD A
(Silicic Acid Method)
C.	APPARATUS
1.	Centrifuge or filtering apparatus
2.	Graduated cylinders, 50 and 100 ml
3.	Two medicine droppers
4.	Crucibles, Gooch or fritted glass
5.	Filter flask
6.	Vacuum source
7.	One 50 ml beaker
8.	Two 5 ml pipets
9.	Buret
D.	REAGENTS
1.	Silicic acid, solids, 100-mesh. Wash the solid portion of
acid to remove fines (impurities) by slurrying (sloshing)
the acid in distilled water. Allow mixture to settle for 15
minutes and remove supernatant. Repeat the process
several times. Dry the washed acid solids in an oven at
103°C and then store in a desiccator.
2.	Chloroform-butanol reagent. Mix 300 ml chloroform, 100
ml n-butanol, and 80 ml 0.5 N H2S04 in separatory funnel
and allow the water and organic layers to separate. Drain
off the lower organic layer through filter paper into a dry
bottle.
3.	Thymol blue indicator solution. Dissolve 80 mg thymol
blue In 100 ml absolute methanol.
4.	Phenolphthalein indicator solution. Dissolve 80 mg
phenolphthalein in 100 ml absolute methanol.
5.	Sulfuric acid, concentrated.
6.	Standard sodium hydroxide reagent, 0.02 N. Prepare in
absolute methanol from concentrated NaOH stock solu-
tion in water.
11 Thief Hole. A digester sampling well.

-------
384 Treatment Plants
(Volatile Acids)
E. PROCEDURE
OUTLINE OF PROCEDURE
/"~S

1. Separate solids by
centrifuging or
filtering sample.
3. Add a
few drops
of thymol
blue
2. Measure 10-15 ml
of sample into
beaker.
Add
concentrated
H?S04 drop-
wise until
\/
turns
red.
5. Place 10 g silicic
acid in crucible
and apply suction.
7. Add 50 ml
chloroform-butanol
Apply suction until
all of reagent has
entered solid acid
column.
Add 5 ml
acidified
sample.
9. Remove filter flask.
10. Add a few
drops of
phenolphthalein.
11. Titrate with
0.02 N NaOH.

-------
Laboratory 385
1.	Centrifuge or filter enough sludge to obtain a sample of 10
to 15 ml. This SAME SAMPLE and filtrate should be used
for both the volatile acids test and the total alkalinity test
(Section 16.461).
2.	Measure volume (10 to 15 ml) of sample and place in a
beaker.
Volume of sample, B =	ml.
3.	Add a few drops of thymol indicator solution.
4.	Add concentrated H2S04, dropwise, until sample definitely
turns red in color (pH = 1 to 1.2).
5.	Place 10 grams of silicic acid (solid acid) in crucible and
apply suction. This will pack the acid material and the
packed material is sometimes called a column.
6.	With a pipet, distribute 5.0 ml acidified sample (from step
4) as uniformly as possible over the column. Apply suction
briefly to draw the acidified sample into the silicic acid
column. Release the vacuum as soon as the sample en-
ters the column.
7.	Quickly add 65 ml chloroform-butanol reagent to the col-
umn.
8.	Apply suction and stop just before the last of the reagent
enters the column.
9.	Remove the filter flask from the crucible.
10.	Add a few drops of phenolphthalein indicator solution to
the liquid in the filter flask.
11.	Titrate with 0.02 N NaOH titrant in absolute methanol,
taking care to avoid aerating the sample. Nitrogen gas or
C02 - free air delivered through a small glass tube may be
used both to mix the sample and to prevent contact with
atmospheric C02 during titration (C02 - free air may be
obtained by passing air through ascarite or equivalent).
Volume of NaOH used in sample titration, a =	ml.
12.	Repeat the above procedure using a blank of distilled wa-
ter.
Volume of NaOH used in blank titration, b =	ml.
F. PRECAUTIONS
1.	The sludge sample must be representative of the digester.
The sample line should be allowed to run for a few minutes
before the sample is taken. The sample temperature should
be as warm as the digester itself.
2.	The sample for the volatile acids test should not be taken
immediately after charging the digester with raw sludge.
Should this be done, the raw sludge may short-circuit to the
withdrawal point and result in the withdrawal of raw sludge
rather than digested sludge. Therefore, after the raw sludge
has been fed into the tank, the tank should be well mixed by
recirculation or other means before a sample is taken.
(Volatile Acids)
3. If a digester is performing well with low volatile acids and
then if one sample should unexpectedly and suddenly give
a high value, say over 1000 mgIL of volatile acids, do not
become alarmed. The high result may be caused by a poor,
nonrepresentative sample of raw sludge instead of digested
sludge. Resample and retest. The second test may give a
more typical value. When increasing volatile acids and de-
creasing alkalinity are observed, this is a definite warning of
approaching control problems. Corrective action should be
taken immediately, such as reducing the feed rate, reseed-
ing from another digester, maintaining optimum tempera-
tures, improving digester mixing, decreasing sludge with-
drawal rate, or cleaning the tank of grit and scum.
G.	EXAMPLE
Equivalent Weight of Acetic Acid, A	=60 mg/ml
Volume of Sample, B	= 10 ml
Normality of NaOH titrant, N	= 0.02 N
Volume of NaOH used in sample titration, a = 2.3 ml
Volume of NaOH used in blank titration, b = 0.5 ml
H.	CALCULATION
Volatile _ A x 1000 ml/l xN(a-b)
Acids,	b
mgIL
(as acetic = 60 mg/ml x 1000 mlIL x 0.02 (2.3 ml - 0.5 ml)
acid)	10 ml
= 216 mg/i.
METHOD B
(Nonstandard Titration Method)
C.	APPARATUS
I.	One pH meter
2.	One adjustable hot plate
3.	Two burets and stand
4.	One 100 ml beaker
D.	REAGENTS
1.	pH 7.0 buffer solution
2.	pH 4.0 buffer solution
3.	Standard acid
4.	Standard base

-------
386 Treatment Plants
(Volatile Acids)
E. PROCEDURE
OUTLINE OF PROCEDURE
1. Separate solids by
centrifuging or re-
moving water above
settled sample.
2. Measure
50 ml &
place in
beaker.



m
<>T; Qin
	^


mi
Titrate with
sulfuric acid
to a pH of
4.0
Note acid used
and continue
titrating to
pH 3.5 to 3.3
J
5. Lightly boil
sample for
3 minutes.
6. Cool in water bath

1
1.	Buffer the pH meter at 7.0 and check pH before treatment of
sample to remove the solids. Filtration is not necessary.
Decanting (removing water solids above settled material) or
centrifuging sample is satisfactory. Do not add any coagu-
lant aids.
2.	Titrate 50 ml of the sample in a 100 ml beaker to pH 4.0 with
the appropriate strength sulfuric acid (depends on alkalin-
ity), note acid used, and continue to pH 3.5 to 3.3. A mag-
netic mixer is extremely useful for this titration.
3.	Carefully buffer pH meter at 4.00 while lightly boiling the
sample a minimum of three minutes. Cool in cold water bath
to original temperature.
4.	Titrate sample with standard 0.050 N sodium hydroxide up
to pH 4.00, and note buret reading. Complete the titration at
pH 7.0. (If this titration consistently takes more than 10 ml of
the standard hydroxide, use 0.100 N NaOH.)
5.	Calculate volatile acid alkalinity (alkalinity between pH 4.0
and 7.0).
Volatile Acid = m' 0.050 N NaOH x 2500
Alkalinity, mgIL	ml Sample
For a 50 ml sample the volatile acid alkalinity equals 50 x
ml 0.050 N NaOH.
7. Titrate to pH of 4.0,
with 0.05 N NaOH, note
buret reading, and com-
plete titration to a pH
of 7.0.
A
(S3
O a o
6. Calculate volatile acids.
Case 1: >180 mgIL volatile acid alkalinity.
Volatile Acids = Volatile Acid Alkalinity x 1.50
Case 2: <180 mgIL volatile acid alkalinity.
Volatile Acids = Volatile Acid Alkalinity x 1.00
Steps 1 and 2 will give the analyst the pH and total alkalinity,
two control tests normally run on digesters. The difference
between the total and the volatile acid alkalinity is bicarbonate
alkalinity. The time required for Steps 3 and 4 is about ten
minutes.
This is an acceptable method for digester control to deter-
mine the volatile acid/alkalinity relationship, but not of sufficient
accuracy for research work.
For details regarding this test see DeLallo, R., and Al-
bertson, O.E., "Volatile Acids by Direct Titration," JOURNAL
WATER POLLUTION CONTROL FEDERATION, Vol. 33, No.
4, pp. 356-365, April 1961. The procedure is reproduced from
the article.

-------
Laboratory 387
F. EXAMPLE AND CALCULATION
Titration of pH 4.0 to 7.0 of a 50 ml sample required 8 ml of
0.05 N NaOH.
STEP 5 - Calculate volatile acid alkalinity (alkalinity between
pH 4.0 and 7.0).
Volatile Acid Alkalinity, mg/L = ml 0 05 N Na0H x 2500
ml Sample
_ 8 ml x 2500
50 ml
= 400 mg/L
STEP 6 - Calculate volatile acids.
Case 1: 400 mg/L > 180 mg/L. Therefore,
Volatile Acids, mg/L = Volatile Acid Alkalinity x 1.50
= 400 mg/L x 1.50
= 600 mg/L
QUESTION
Write your answer in a notebook and then compare your
answer with the one on page 461.
16.4S What is the volatile acid concentration in a digester if a
50 ml sample required 5 ml of 0.05 N NaOH for a
titration from a pH of 4.0 to 7.0?
16.461 Total Alkalinity
A. DISCUSSION
Tests for total alkalinity of digesters are normally run on
settled supernatant samples. The alkalinity of the recirculated
sludge is a measure of the buffer capacity in the digester.
When organic matter in a digester is decomposed anaerobi-
cally, organic acids are formed which could lower the pH if
buffering materials (buffer capacity) were not present. If the pH
drops too low, the organisms in the digester could become
inactive or die and the digester becomes upset (no longer
capable of decomposing organic matter).
(Total Alkalinity)
For digester control purposes, the volatile acid/alkalinity rela-
tionship should be determined. When the volatile acid/alkalinity
relationship is from less than 0.1/1.0 to 0.5/1.0, the loading and
seed retention of the digester are under control. When the
relationship starts increasing and becomes greater than 0.5/
1.0, the digester is out of control and will become stuck unless
effective corrective action is taken. The pH will not be out of
range as long as the volatile acid/alkalinity relationship is low.
This relationship gives a warning before trouble starts.
B. WHAT IS TESTED?
Sample	Common Range
Recirculated Sludge	2-10 Times Volatile Acids
C. APPARATUS
1.	Centrifuge and centrifuge tubes, or settling cylinders
2.	Graduated cylinders (25 ml and 100 ml)
3.	50 ml buret
4.	400 ml Erienmeyer flask or 400 ml beaker
5.	pH meter or a methyl orange chemical color indicator
may be used (see Procedure)
D. REAGENTS)
1.	Sulfuric Acid, 0.2 N. Cautiously add 30 ml of concentrated
sulfuric acid (H2S04) to 300 ml of distilled water. Dilute to 1
liter with boiled distilled water. Standardize against 0 02 N
sodium carbonate (Step 2).
2.	Sodium Carbonate, 0.02 N. Dry in oven before weighing.
Dissolve 1.06 g of anhydrous sodium carbonate (Na2C03)
in toiled distilled water and dilute to 1 liter with distilled
water.
3.	Methyl Orange Chemical Color Indicator. Dissolve 0.5 g
methyl orange in 1 liter of distilled water.

-------
388 Treatment Plants
(Total Alkalinity)
E. PROCEDURE
OUTLINE OF PROCEDURE
4. Titrate.
Sludge
Sample

1. Centrifuge
or settle
A
3. Place electrodes of
pH meter in beaker.

2. Add 190 ml of
distilled water
to 10 ml or less
of clear supernatant.
OOP VX


\
or 3. Add 2 drops of
methyl orange.
\

This procedure is followed to measure the alkalinity of a
sample and also the alkalinity of a distilled water blank.
1.	Take a clean 400 ml beaker and add 10 ml or less of clear
supernatant (in case of water or distilled water, use 200 ml
sample). Select a sample volume that will give a useable
titration volume. If the liquid will not separate from the
sludge by standing and a centrifuge is not available, use the
top portion of the sample. This SAME SAMPLE and filtrate
should be used for both the total alkalinity test and the
volatile acids test.
2.	Add 190 ml distilled water (in case of water or distilled water
determination, skip this step).
3.	Place the electrodes of pH meter into the 400 ml beaker
containing the sample.
4.	Titrate to a pH of 4.5 with 0.02 N sulfuric acid. (In case of a
lack of pH meter, add 2 drops of methyl orange indicator. In
this case, titrate to the first permanent change of color to a
red-orange color. Care must be exercised in determining
the change of color and your ability to detect the change will
improve with experience.)
5.	The alkalinity of the distilled water should be checked and if
significant, subtracted from the calculation.
6.	Calculate alkalinity.
A"wSS! m3™* = ml of 0 02 N H*S0< * 5*
Total Alkalinity, mg/i.= ml of 0.02 N H2S04 x 100*
- mgIL alkalinity of distilled H20
* Use 5 if measuring alkalinity of water or distilled water (200 ml
sample) and 100 if measuring alkalinity of sludge (10 ml sample).

-------
Laboratory 389
(C02)
F.	EXAMPLE
Results from alkalinity titrations on
1.	Distilled Water
2.	Recirculated Sludge
G.	CALCULATIONS
4 ml 0.02 N H2S04
19.8 ml 0.02 N H2S04
Alkalinity of
Distilled HjO, = ml of 0.02 N H2S04 x 5
mgIL	. ,
= 4 ml x 5
= 20 mgIL
Total Alkalinity,
mg IL of recir- = ml of 0.02 N H2S04 x 100 - mg/L alkalinity
culated sludge	of distilled H20
= 19.8 ml x 100 - 20 mg//.
= 1980 mg/L - 20 mg//.
= 1960 mgIL
QUESTIONS
Write your answers in a notebook and then compare your
answers with those on page 461.
16.4T Why would you run a total alkalinity test on recircu-
lated sludge?
16.4U What is meant by the buffer capacity in a digester?
16.4V If the total alkalinity in a digester is 2000 mg/L and the
volatile acids concentration is 300 mg/L per liter, what
is the volatile acid/alkalinity relationship?
16.462 Carbon Dioxide (CO,) In Digester Gas
A. DISCUSSION
Changes in the anaerobic sludge digestion process will be
observed in the gas quality and are usually noted after the
volatile acids or volatile acid/alkalinity relationship starts to in-
crease. The C02 content of a properly operating digester will
range from 30 percent to 40 percent by volume. If the percent
is above 44 percent, the gas will not burn. The easiest test
procedure for determining this change is with a COz analyzer.
B. WHAT IS TESTED?
Sample
C02 in Digester Gas
Preferred
30% to 35% by Volume
METHOD A
C.	APPARATUS
1.	One Bunsen burner
2.	Plastic tubing
3.	100 ml graduated cylinder
4.	250 ml beaker
D.	REAGENTS
C02 Absorbent (KOH). Add 500 g potassium hydroxide
(KOH) per liter of water.
Fig. 16.9 C02 measurement using inverted graduated
cylinder

-------
390 Treatment Plants



v
y
0
0
a
O
s y
r ^

y





6. Read volume of
gas remaining to
nearest ml.
PRECAUTIONS
1.	Avoid any open flames near the digester.
2.	Work in a well ventilated area to avoid the formation of
explosive mixtures of methane gas.
3.	If your gas sampling outlet is on top of your digester, turn on
outlet and vent the gas to the atmosphere for several min-
utes to clear the line of old gas. Start with step 2, displace
air in graduated cylinder. NEVER ALLOW ANY SMOKING
OR FLAMES NEAR THE DIGESTER AT ANY TIME.

-------
Laboratory 391
1.	Measure total volume of a 100 ml graduate by filling it to
the top with water (approximately 125 ml). Record this
volume.
2.	Pour approximately 125 ml of C02 absorbent in a 250 ml
beaker.
CAUTION: Do not get any of this chemical on your skin or
clothes. Wash immediately with running water until slip-
pery feeling is gone or severe burns can occur.
3.	Collect a representative sample of gas from the gas dome
on the digester, a hot water heater using digester gas to
heat the sludge, or any other gas outlet. Before collecting
the sample for the test, attach one end of a gas hose to the
gas outlet and the other end to a Bunsen burner. Turn on
the gas, ignite the burner, and allow it to burn digester gas
for a sufficient length of time to insure collecting a repre-
sentative gas sample.
4.	With gas running through hose from gas sampling outlet,
place hose inside inverted calibrated graduated cylinder
and allow digester gas to displace air in graduate. Turn off
gas.
CAUTION: The proper mixture of digester gas and air is
explosive when exposed to a flame.
5.	Place graduate full of digester gas upside down in beaker
containing C02 absorbent.
6.	Insert gas hose inside upside down graduate.
7.	Turn on gas, but DO NOT BLOW OUT LIQUID. Run gas
for at least 60 seconds.
8.	Carefully remove hose from graduate with gas still run-
ning.
9.	IMMEDIATELY TURN OFF GAS.
10.	Wait for ten minutes and shake gently. If liquid continues
to rise, wait until it stops.
11.	Read gas remaining in graduate to nearest ml. (Fig. 16.9,
page 389).
F. EXAMPLE
Total Volume of Graduate = 126 ml
Gas Remaining in Graduate - 80 ml
g. Calculation
CO % = (Total Vo,ume> ml ~ Gas Remaining, ml) x 100%
Total Volume, ml
126 ml -80 ml) x
46
126
37%
126 ml
x 100%
•365
126) 46.0
37 8
8 20
7 56
METHOD B
(ORSAT)
The Orsat gas analyzer can measure the concentration of
carbon dioxide, oxygen, and methane by volume in digester
gas. To analyze digester gas by the Orsat method, follow
equipment manufacturer's instructions. This procedure is not
recommended for the inexperienced operator.
QUESTIONS
Write your answers in a notebook and then compare your
answers with those on page 461.
16.4W What are the dangers involved in running the C02 test
on digester gas?
16.4X What is the percent COz in a digester gas if the total
volume of the graduated cylinder is 120 ml and the gas
remaining in the cylinder after the test is 73 ml?
16.463 Sludge (Digested) Dewatering Characteristics
A.	DISCUSSION
The dewatering characteristics of digested sludge are very
important. The better the dewatering characteristics or draina-
bility of the sludge, the quicker it will dry and the less area will
be required for sludge drying beds.
B.	WHAT IS TESTED?
PREFERRED RANGE
Sample
Digested Sludge
Method A
Depends on
appearance
Method B
100-200 ml
per 500 ml
of sample
640
630
C.	APPARATUS
METHOD A
1000 ml graduated cylinder
METHOD B
1.	Imhoff cone with tip removed
2.	Sand from drying bed
3.	500 ml beaker
D.	REAGENTS
None.
E.	PROCEDURE
Two methods are presented in this section. Method A relies
on a visual observation and is quick and simple. The only
problem is that operators on different shifts might record the
same sludge draining characteristics differently. Method B re-
quires 24 hours, but the results are recorded by measuring the
volume of liquid that passed through the sand. Method B would
be indicative of what would happen if you had sand drying
beds.

-------
392 Treatment Plants
(Sludge Dewatering)
METHOD A
OUTLINE OF PROCEDURE
1. Add digested sludge	2. Pour sample from graduate	3. Watch solids
to 1000 ml graduate.	back into container.	adhere to
cylinder walls.
Sample
Container
1.	Add sample of digested sludge to 1000 ml graduate.
2.	Pour sample back into sample container. Set graduated
cylinder down.
3.	Watch graduate. If solids adhere to cylinder wall and water
leaves solids in form of rivulets, this is a GOOD dewatering
sludge on a sand drying bed (Fig. 16.10).
Fig. 16.10
Sludge on graduated
cylinder walls for
sludge dewatering
test

-------
Laboratory 393
(Sludge Dewatering)
METHOD B
OUTLINE OF PROCEDURE
1. Pour digested sludge
on top of sand in
Imhoff cone.
2. Place beaker under tip
and wait 24 hours.
3. Measure liquid
that has passed
through the sand.
Broken Tip
1.	Take a glass Imhoff cone that has tip removed and place a
glass wool plug in the end to hold the sand in the cone.
2.	Fill halfway with sand from drying bed.
3.	Fill remainder to 1 liter with digested sludge.
4.	Place 500 ml beaker under cone tip and wait 24 hours.
5.	Record liquid that has passed through sand in ml. If less
than 100 ml has passed through sand, you have poor
sludge drainability.
QUESTION
Write your answer in a notebook and then compare your
answer with the one on page 461.
16.4Y What are the differences in the use of (1) a graduated
cylinder and (2) an Imhoff cone, filled with sand, that
has the tip removed, to measure the dewatering
characteristics of digested sludge?

-------
394 Treatment Plants
(Supernatant)
16.464 Supernatant Graduate Evaluation
A.	DISCUSSION
The digester supernatant solids test measures the percent
of settleable solids being returned to the plant headworks. The
settleable solids falling to the bottom of a graduate should not
exceed the bottom 5 percent of the graduate in most second-
ary plants. When this happens, you are imposing a load on the
primary settling tanks that they were not designed to handle. If
the solids exceed 5 percent, you should run a total suspended
solids Gooch crucible test (Section 16.43) on the sample
originating from the digester and calculate the recycle load on
the plant.
B.	WHAT IS TESTED?
Sample	Common Values
Supernatant	% Solids should be <5%
C.	APPARATUS
100 ml graduated cylinder
D.	REAGENTS
None
E. PROCEDURE
OUTLINE OF PROCEDURE
1. Fill 100 ml graduate
with supernatant
2. After 60 minutes,
read ml of solids
at bottom.
7
7
Supernatant
Sample


*=:3T
10 ml
100 ml Graduate
1.	Fill a 100 ml graduated cylinder with supernatant sample.
2.	After 60 minutes, read the ml of solids that have settled to
the bottom.
3. Calculate supernatant solids, %.
Supernatant Solids, % = ml of Solids

-------
Laboratory 395
(Lime Analysis)
F.	EXAMPLE
Solids on bottom of cylinder, 10 ml.
G.	CALCULATIONS
Supernatant Solids, %	= ml of Solids
= 10 ml
= 10% Solids (High) by Volume
QUESTION
Write your answer in a notebook and then compare your
answer with the one on page 461.
16.4Z Why should the results of the supernatant solids test
be less than 5 percent solids?
16.465 Temperature
A.	DISCUSSION
The rate of sludge digestion in a digester is a function of the
digester temperature. The normal temperature range in a di-
gester is around 95 to 98°F (35 to 37°C). The temperature of a
digester should not be changed by more than 1°F (0.6°C) per
day because the helpful organisms in the digester are unable
to adjust to rapid temperature changes.
B.	APPARATUS AND PROCEDURE
See Section 16.5, "Procedure 17, Temperature."
16.47 Lime Analysis
A. DISCUSSION
Lime is a general term used in the water and wastewater
field to describe quicklime and hydrated lime. Quicklime con-
tains about 90 percent calcium oxide, CaO, and for this reason
is also called calcium oxide. Quicklime is also called unslaked
lime. Hydrated lime or slaked lime is a dry powder obtained by
a chemical reaction that occurs when sufficient water is added
to quicklime. This form of lime is also referred to as hydrated
lime or Ca(OH)2.
Lime has been used in wastewater treatment for many
years. Usually lime was used as a coagulant, especially in
treating industrial wastes. The development of advanced
wastewater treatment processes has brought new popularity to
lime treatment as a means of effectively removing phosphorus.
The selection of which type of lime to use in a particular
situation is influenced by a number of factors, such as trans-
portation costs, amount of lime required, and availability. Gen-
erally the cost of hydrated lime is greater than that of quicklime.
On the other hand, the capital cost of slaking equipment re-
quired when quicklime is used will tend to offset savings in
material costs.
The following method of lime analysis is taken from the
American Water Works Association's Standard B202-77 for
quicklime and hydrated lime. The operator can use this method
not only to evaluate newly purchased lime but also to analyze
lime recovered from lime sludge incineration.
B. WHAT IS TESTED?
Sample
Hydrated Lime
(Lime Analysis)
Common Range
82 to 98% Ca (OH)2
or 62 to 74% CaO
Recalcined Lime Sludge	60 to 90% CaO
Quicklime	70 to 96% CaO
C.	APPARATUS
1.	Analytical balance
2.	250 ml Erlenmeyer flask
3.	Hot plate
4.	Magnetic stirrer and stirring bar (optional)
5.	100 ml bucket
6.	Mortar and pestle
D.	REAGENTS
1.	0.1782 N Hydrochloric Acid Solution: Prepare a solution
containing 15.7 ml HCI (specific gravity 1.19) per liter. This
solution will be stronger than necessary. Standardize the
HCI solution against 0.85 grams of pure, dry sodium carbo-
nate, using methyl orange as an indicator. Titrate to a sal-
mon pink endpoint. Adjust the solution either by the addition
of C02-free distilled water if too strong or by the addition of
HCI if too weak, so that 0.85 g of sodium carbonate exactly
neutralizes 90 ml of the standard HCI solution. One milliliter
of the standard HCI solution is equivalent to 1.0 percent
CaO or 1.32 percent Ca (OH)2 when 0.5 grams of sample
are used.
2.	Phenolphthalein indicator: Four percent solution. Dissolve 4
grams of dry phenolphthalein in 100 ml of 95 percent
ethanol.
3.	Methyl Orange indicator: Dissolve 500 milligrams in distilled
water and dilute to 1 liter.
4.	C02-free Distilled Water: Prepare fresh as needed by boil-
ing distilled water for 15 minutes and cooling rapidly to room
temperature. Cap the flask or bottle in which the water has
been boiled with a slightly oversized inverted beaker to
minimize the entry of atmospheric carbon dioxide during the
cooling process. For best results, exclude C02 entry during
cooling by attaching a tube containing soda lime, Ascarite,
Caroxite, or equivalent.
5.	Cane Sugar.

-------
396 Treatment Plants
(Lime Analysis)
E. PROCEDURE FOR AVAILABLE CALCIUM OXIDE
OUTLINE OF PROCEDURE
1. Pulverize about 5 grams of sample
and weigh 0.5 grams.
2. Add 10 ml distilled water
to dry flask and then add
0.5 gram sample.
Place flask on hot plate and add
50 ml boiling distilled water.
Boil for 1 rtiinute. Remove from
heat and cool in cold water bath.
Add 50 ml distilled water,
then 15 to 17 grams sugar,
stopper flask, swirl, and
let stand for 15 minutes.
5. Remove stopper and add 4 to 5
drops phenolphthalein.
6. Titrate
with standard HCI solution.

-------
Laboratory 397
1.	Pulverize about 5 grams of sample with a mortar and pes-
tle.
2.	Weigh 0.5 grams of the pulverized sample and brush into a
250 ml Erlenmeyer flask containing 10 ml C02-free distilled
water, and immediately stopper the flask loosely with a rub-
ber stopper.
3.	Remove the stopper, place the flask on a hot plate, and
immediately add 50 ml of boiling C02-free distilled water.
Swirl the flask and boil actively for 1 minute for complete
slaking. Remove from hot plate, stopper the flask loosely,
and place in a cold water bath to cool to room temperature.
4.	Add about 50 ml of C02-free distilled water, and then ap-
proximately 15 to 17 grams of pure cane sugar. Stopper the
flask, swirl and let stand for 15 minutes to react. Swirl at 5
minute intervals during this period.
5.	Remove stopper, add 4 to 5 drops of phenolphthalein indi-
cator. Wash the stopper and the sides of the flask with
C02-free distilled water.
6.	Titrate with standard HCI solution.
F.	EXAMPLE
1.	Sample size	= 0.5 grams
2.	ml of titrant used, A = 94.5 ml
G.	CALCULATIONS
CaO, % = ml of HCI titrant used
= 94.5%
(Lime Analysis)
H.	NOTES AND PRECAUTIONS
I.	A magnetic stirrer may be used during the titration, if de-
sired. Adjust to stir as rapidly as possible without incurring
loss by spattering.
2. When titrating, first add, without shaking or stirring, about
90 percent of the acid requirement from the 100 ml buret.
Then shake or stir as vigorously as possible and finish the
titration more carefully, to the first complete disappearance
of pink color. Note the reading and ignore the return of
color. If the operator is not familiar with previous analyses of
the lime under test it is good practice to run a preliminary
test by slow titration to determine the proper amount of acid
to add without first shaking or stirring the flask.
I. PROCEDURE FOR HYDRATED LIME
1.	The procedure for determining hydrated lime, Ca (OH),, is
the same as for CaO except that cold COz - free distilled
water is used and the boiling and cooling procedures are
omitted.
2.	The number of milliliters of standard acid solution used
times 1.32 is the percentage of available calcium hydroxide,
Ca(OH)2, in the sample.
J. REFERENCE
AWWA Standard for Quicklime and Hydrated Lime, AWWA
B202-77, American Water Works Association, Denver, Col-
orado 80235
QUESTION
Write your answer in a notebook and then compare your
answer with the one on page 461.
16.4AA Lime is used in what types of treatment processes?
!&W OF LB660N 5 OF 9
ON
CAtdeAXoGv peo&epuzeGrfwe/wfM
Work the next portion of discussion and review questions
before continuing with Lesson 6.

-------
398 Treatment Plants
DISCUSSION AND REVIEW QUESTIONS
Chapter 16. LABORATORY PROCEDURES AND CHEMISTRY
(Lesson 5 of 9 Lessons)
Write the answers to these questions in your notebook. The
question numbering continues from Lesson 4.
18.	Calculate the SVI if the mixed liquor suspended solids are
2000 mgIL and the 30-minute settleable solids test is 500
ml in 2 liters or 25 percent.
19.	Calculate the SDI if the SVI is 125.
20.	What does sludge age measure?
21.	What is the difference between sludge age and MCRT?
22.	Why should the dewatering characteristics of digested
sludge be measured?
23.	What happens to the plant when the supernatant from the
digester is high in solids?
24.	What is a thief hole?
25.	What relationship is the critical control factor in digester
operation?
26.	How can you obtain a representative sample of digester
gas?
27.	Why should the temperature of a digester not be changed
by more than 1°F (0.6°C) per day?
CHAPTER 16. LABORATORY PROCEDURES AND CHEMISTRY
(Lesson 6 of 9 Lessons)
16.5 LABORATORY PROCEDURES FOR NPDES
MONITORING
16.50 Need for Approved Procedures
Tests in this section are designed for the treatment plant
operator or laboratory technician who is required to monitor
effluent discharges under a National Pollutant Discharge
Elimination System (NPDES) permit. Principal tests include
Biochemical Oxygen Demand (BOD), pH, Fecal Coliform, Re-
sidual Chlorine, and Suspended Solids. These and other tests
included in this section are listed below.
Test
1.	Acidity
2.	Alkalinity, Total
Biochemical Oxygen Demand (BOD) (See Dissolved
Oxygen)
3.	Chemical Oxygen Demand (COD)
4.	Chloride
5.	Chlorine, Total Residual
6.	Coliform, Fecal
7.	Dissolved Oxygen (DO) and Biochemical Oxygen De-
mand (BOD)
8.	Hydrogen Ion (pH)
9.	Metals
10.	Nitrogen
11.	Oil and Grease
pH (see Hydrogen Ion)
12.	Phosphorus
13.	Solids, Total, Dissolved, and Suspended
14.	Specific Conductance
15.	Sulfate
16.	Surfactants
17.	Temperature
18.	Total Organic Carbon
19.	Turbidity
Remember that monitoring data required by an NPDES
permit MUST be obtained by using APPROVED test proce-
dures. A list of approved test procedures can be found in the
"Guidelines Establishing Test Procedures for the Analysis of
Pollutants," FEDERAL REGISTER, Volume 41, No. 232, pages
52780 to 52786, December 1, 1976.
16.51 Test Procedures
1. Acidity
A.	DISCUSSION
This procedure determines the mineral acidity of a sample.
Acidity results from carbon dioxide from the atmosphere, from
the biological oxidation of organic matter or from industrial
waste discharges.
The acidity of a water or wastewater sample is its quantita-
tive capacity to neutralize a strong base to a pH of 8.2. Titrating
with 0.02 N sodium hydroxide measures the concentration of
mineral acids (such as sulfuric acid), hydrolyzing salts, and
total acidity. The end point of the titration may be detected
using a pH meter or phenolphthalein indicator methods.
B.	WHAT IS TESTED?
Sample	Common Range, mg IL as CaCO,
Effluent	Depends on water supply
C.	APPARATUS, REAGENTS, AND PROCEDURE
See page 273, STANDARD METHODS, 14th Edition.

-------
Laboratory 399
D.	EXAMPLE
Sample of plant effluent collected and tested for acidity.
Acidity test results:
1.	Sample size, ml	= 50 ml
2.	NaOH normality, N	= 0.02 N
3.	ml NaOH titrant used, A = 8.9 ml
E.	CALCULATIONS
Acidity, mg/L as CaC03 =Ax«x 50,000
ml sample
= (8.9 ml) x (0.02 N) x 50,000
50 ml
= 178 mg/L as CaC03
QUESTION
Write your answer in a notebook and then compare your
answer with the one on page 461.
16.5A What are some sources of acidity in a treatment plant
influent?
2. Alkalinity, Total (Electrometric Method)
A.	DISCUSSION
The alkalinity of a water or wastewater is a measure of its
capacity to neutralize acids. The alkalinity of natural waters is
due primarily to the salts of weak acids, although weak or
strong bases may also contribute. Bicarbonate ions (HC03~)
represent the major form of alkalinity.
B.	WHAT IS TESTED?
Sample	Common Range, mg/L
Influent and Effluent	50-500
(Alkalinity, Total)
D. REAGENTS
(NOTE: Standardized solutions are commercially available.)
1.	Sodium carbonate (Na2C03) solution, approximately 0.05
N : Dry 3 to 5 grams (g) primary standard Na2C03 at 250°C
for 4 hours and cool in a desiccator. Weigh 2.5 ± 0.2 g.
Transfer to a 1 liter volumetric flask and fill to the mark with
distilled water.
2.	Sulfuric acid (H2S04), 0.1 N: Dilute 3.0 mis concentrated
H2S04 to 1 liter with distilled or deionized water. Stan-
dardize with the above sodium carbonate solution using the
following procedure:
Using 40.0 mis 0.05 N Na2C03 solution, add 60 mis distil-
led water and titrate (add sulfuric acid, 0.1 N using a buret
to a pH of about 5. Lift out the electrodes, rinse into the
same beaker, and boil gently for 3 to 5 minutes under glass
cover. Cool to room temperature, rinse cover glass into
beaker and finish titration to pH 4.5 and record the number
of milliliters (ml) used. Calculate the normality of sulfuric
acid according to the formula.
Normality, N = A * B
53 x C
where, A = grams Na2C03 weighed into 1 liter
B = ml NajCOj
C = ml HjS04 used
EXAMPLE:
Weighted 2.502 g Na2C03 = A
Used 40.0 ml NajC03 = B
Titrated using 18.9 ml =C
		,«y	9) *|40.0 ml)
53 x (18.9 ml)
= 0.10 N H2S04
3.	Standard sulfuric acid, 0.02 A/: Dilute 200 ml
0.10 N standard acid to 1 liter using a vol-
umetric flask. To determine the volume to be
diluted, use the following formula:
C. APPARATUS REQUIRED
pH meter	beaker (250 ml)
reference electrode	magnetic stirrer
glass electrode	flask, volumetric (1000 ml)
graduate cylinder (50 ml)	bottle, wash
buret (25 ml)	balance
buret support	desiccator
Volume dUM m! - W«l«d. 0.02 »0 * <10C0 mO
(Calculated Normality, 0.10 N)
= (0.02 N) x (1000 ml)
(0.10 AO
= 200 ml

-------
400 Treatment Plants
(Alkalinity, Total)
E. PROCEDURE
OUTLINE OF PROCEDURE
EZ3
• • •
1. Add 100 ml of
sample.
2. Place electrodes
of pH meter in
beaker.
3. Titrate to pH of
4.5
1.	Take a clean beaker and add 100 ml of sample (select a
sample volume that will give a useable titration volume not
greater than 50 ml).
2.	Place electrodes of pH meter into beaker containing sam-
ple.
3.	Stir sample slowly.
4.	Titrate to pH 4.5 with 0.02 N H2S04.
5.	Calculate Total Alkalinity.
F.	EXAMPLE
Results from alkalinity	titration on effluent sample:
1.	Sample size, ml	=100 ml
2.	ml of titrant used, A	= 20 ml
3.	Acid Normality, N	= 0.02 N H2S04
G.	CALCULATIONS
Total Alkalinity, mg/L as CaC03
A x N x 50,000
ml of sample
= (20 ml) x (0.02 N) x 50,000
100 ml
= 200 mg/Z.
H. PRECAUTIONS
1.	Soaps and oily matter may interfere with the test by coating
the pH electrodes and causing a sluggish response.
2.	The sample should be analyzed as soon as practical, within
a few hours after collection.
3.	The sample should not be filtered, diluted, concentrated, or
altered in any way.
I. REFERENCE
(See Page 278, STANDARD METHODS, 14th Edition.)

-------
Laboratory 401
QUESTION
Write your answer in a notebook and then compare your
answer with the one on page 461.
16.5B What ion represents the major form of alkalinity in
wastewater?
3. Chemical Oxygen Demand or COD
A. DISCUSSION
COD is a good estimate of the first-stage oxygen demand for
most municipal wastewaters. An advantage of the COD test
over the biochemical oxygen demand (BOD) test is that you do
not have to wait five days for the results. The COD test also is
used to measure the strength of wastes that are too toxic for
the BOD test. The COD is usually higher than the BOD, but the
amount will vary from waste to waste.
The COD test should be considered an independent meas-
urement of organic matter in a wastewater sample rather than
a substitute for the BOD test. COD analysis suffers from the
disadvantage that it does not measure the rate of biodegrada-
bility of matter and therefore it is difficult to predict the effects of
an effluent on the DO in receiving waters and the treatability of
a particular wastewater by biological processes.
The COD test method oxidizes organic substances in the
wastewater sample using potassium dichromate in 50 percent
sulfuric acid solution. Silver sulfate is used as a catalyst and
mercuric sulfate added to remove chloride interference. The
excess dichromate is titrated with standard ferrous ammonium
sulfate, using ferroin as an indicator. The method related here
is a quick (3 to 4 hours), effective measure of the strength of a
waste.
(COD)
B.	WHAT IS TESTED?
Sample	Common Range, mgIL
Influent	200 to 400
Effluent	10 to 80
Industrial Waste	200 to 4000
C.	APPARATUS REQUIRED
Two graduated cylinders, 50 ml
Volumetric pipet, 10 ml
Buret, 50 ml
Glass beads or boiling stones
Flasks, Erlenmeyer with ground glass joint, 250 ml
Reflux condenser
Hot plate
Magnetic stirrer
D.	REAGENTS
(Standardized solutions may be purchased from chemical
suppliers.)
1.	Standard potassium dichromate (K,Cr207) 0.250 N. Dis-
solve 12.259 g dried primary standard grade K2Cr207 in
distilled water and make up to 1 liter (at 103°C).
2.	Sulfuric acid-silver sulfate reagent. Add 22 g of silver sulfate
(Ag,S04) to a 9-pound bottle of concentrated sulfuric acid
(H2S04). Allow one to two days for the silver sulfate to
dissolve.
3.	Standard ferrous ammonium sulfate solution, 0.25 N. Dis-
solve 98 g Fe (NH4)2 • 6 H20 cool and dilute to 1 liter. This
solution is unstable and must be standardized daily.
4.	Ferroin Indicator. Dissolve 1.485 g of 1.10 phenanthroline
monohydrate (C12HfiN2 H20), together with 0.695 g ferrous
sulfate crystals (FeS04 • 7 HzO), in water and make up to
100 ml.
5.	Silver sulfate, reagent powder.
6.	Mercuric sulfate (HgS04) analytical grade crystals.

-------
402 Treatment Plants
(COD)
OUTLINE OF PROCEDURE
(For COD >50 mgIL)
5. Add 30 ml
H2S04-Ag2S04
Solution
4. Add 10 ml
0.25 N K2Cr207
3. Add 2 ml
conc. H2S04
Cooling Water
1. Add
20 ml
Sample
2. Add 0.4 g
HgS04
8. Add Ferroin
Indicator
7.
* Reflux condenser, Friedrichs
** Erlenmeyer flask
E. PROCEDURE (For COD >50 mgIL)
1.	Measure 20.0 ml of sample into a clean 250 ml Erlen-
meyer flask with a ground glass joint.
2.	Place 0.4 g mercuric sulfate into the flask containing the
sample.
3.	Slowly add 2.0 ml concentrated sulfuric acid (H2S04).
Swirl until contents are well mixed. Cool.
4.	Pi pet 10.0 ml standard 0.25 N potassium dichromate solu-
tion into the flask and carefully mix.
5.	Attach flask to condenser and start cooling water.
6.	Carefully add 30 ml sulfuric acid-silver sulfate reagent into
the flask while swirling the flask through open end of con-
denser. Use caution. Add several glass beads or boiling
stones. Make sure contents of the flask are thoroughly
mixed before heat is applied. The REFLUX12 mixture must
Reflux Two
Hours, Cool
& Wash Down
Titrate
to red
end point.
be thoroughly mixed before heat is applied. If this is not
done, local hot spots on bottom of flask may cause mixture
to be blown out of flask.
7.	Prepare a BUNK13 by repeating above steps and by sub-
stituting distilled water for the sample.
8.	Reflux samples and blank for two hours. (If sample mix-
ture turns completely green, the sample was too strong.
Dilute sample with distilled water and repeat above steps
substituting diluted sample.)
9.	While the samples and blank are refluxing, standardize
the ferrous ammonium sulfate (FAS) solution:
a.	Pipet 10.0 ml standard 0.25 N potassium dichromate
solution into a 250-ml Erlenmeyer flask. Add about 90
ml of water.
b.	Add 30 ml concentrated H2S04 with mixing. Let cool.
12 Reflux. Flow back. Sample is heated, evaporates, cools, condenses, and flows back to flask.
ia Blank. A bottle containing only dilution water or distilled water, but the sample being tested is not added. Tests are frequently run on a
SAMPLE and a BLANK and the differences compared.

-------
Laboratory 403
(COD)
Add 2 to 3 drops ferroin indicator, titrate with ferrous
ammoniuim sulfate (FAS) solution. Color change of
solution is from orange to greenish to red.
Ml FAS 	
Normality of FAS = 10 ml KgCr207 * 0.25	=
ml FAS		
10.	After refluxing mixture for two hours, wash down con-
denser. Let cool. Add distilled water to about 140 ml.
11.	Titrate reflux mixtures with standard FAS.
Blank	- ml FAS	
Sample	- ml FAS		
F.	PRECAUTIONS
1.	The wastewater sample should be well mixed. If large parti-
cles are present, the sample should be homogenized with a
blender or mixer.
2.	Flasks and condensers should be clean and free from
grease or other oxidizable materials, otherwise erratic re-
sults will be obtained.
3.	The standard ferrous ammonium sulfate solution is unsta-
ble and should be standardized daily.
4.	Use extreme caution and safety precautions when handling
the chemicals used for the test. Goggles, a rubberized ap-
ron, and asbestos gloves are essential equipment.
5.	Use a wide-tip pipet to insure a representative sample is
added.
6.	The solution must be well mixed before it is heated. If the
acid is not completely mixed in the solution when it is
heated, the mixture could spatter and some of it pass out
the vent, thus ruining the test.
7.	Mercuric sulfate is very toxic. Avoid skin contact and breath-
ing this chemical.
8.	The amount of mercuric sulfate added depends on the
chloride concentration; maintain a 10:1 ratio HgS04:CI.
9.	If the COD of the sample is less than 50 mg/L, follow the
above procedure but use 0.025 N standard potassium di-
chromate and back-titrate with 0.10 N FAS. Extreme care
must be taken because even a trace of organic matter on
the glassware may cause a gross error.
G.	EXAMPLE
1.	Standardization of FAS (ferrous ammonium sulfate).
ml 0.25 N K2Cr207 = 10.0
ml FAS	= 11.0
K,Cr,07 x 0.25
Normality FAS =	2 2 7	
ml FAS
= 100 * 0 25
11.0
= 0.227 N
2.	Sample Test.
Sample taken
A = ml FAS used for blank
B = ml FAS used for sample
H.	CALCULATION
COD, mg/L = (A'B) x N x 8000
ml sample
J10.0 - 3.0) x (0.227 N) x 8000
20 ml
= 635 mg/L
I.	REFERENCE
See page 550, STANDARD METHODS, 14th Edition.
QUESTIONS
Write your answers in a notebook and then compare your
answers with those on page 461.
16.5C What does the COD test measure?
16.5D What is an advantage of the COD test over the BOD
test?
4. Chloride (Silver Nitrate Method)
A.	DISCUSSION
Chloride (Cl~) is one of the major inorganic ions present in
water and wastewater. The chloride concentration is higher in
wastewater than raw water because sodium chloride (NaCI),
table salt, is a common article of diet and passes through the
human digestive system. Along the sea coast chloride may be
present in high concentrations because of infiltration of salt
water into the wastewater collection system. Chloride concen-
trations also may be increased by industrial process dis-
charges.
B.	WHAT IS TESTED?
Common Range, mg/L
Depends on chloride concentration
in raw water supply and industrial
discharges.
= 20.0 ml
= 10.0 ml
= 3.0 ml
Sample
Wastewater
C.	METHODS
Three methods are currently acceptable for NPDES chloride
monitoring. They are: Silver Nitrate, Mercuric Nitrate, and the
automated colorimetric Ferricyanide Methods. The first two are
similar in most respects, and selection is a matter of prefer-
ence. The third is an automated procedure requiring special
equipment.
D.	APPARATUS REQUIRED (Silver Nitrate Method)
Graduated cylinder, 100 ml
Buret, 50 ml
Ertenmeyer flask, 250 ml
Pipet, 10 ml
Magnetic stirring apparatus
E.	REAGENTS
{NOTE: Standard solutions may be purchased from chemi-
cal suppliers.)
1.	Chloride-free water — distilled or deionized water.
2.	Potassium chromate (K2Cr04) indicator solution: Dissolve
50 grams K,Cr04 in a little distilled water. Add silver nitrate
(AgNOj) sofution until a red precipitate is formed. Let stand
12 hours, filter, and dilute to 1 liter with distilled water.

-------
404 Treatment Plants
(Chloride)
3.	Standard Silver Nitrate Titrant, 0.0141 N: Dissolve 2.395
grams AgN03 in distilled water and dilute to 1 liter.
Standardize to 0.0141 N sodium chloride (NaCI) by pro-
cedure given below.
Store in brown bottle.
4.	Standard Sodium Chloride, 0.0141 N: Dissolve 0.8241
grams in chloride-free water and dilute to 1 liter.
F. PROCEDURE
1.	Place 100 ml or a suitable portion diluted to 100 ml in a 250
ml Erlenmeyer flask.
2.	Add 1.0 ml K2Cr04 indicator solution.
3.	Titrate with standard silver nitrate to a pinkish yellow end
point. Be consistent in end point recognition. Compare with
known standards of various chloride concentrations.
OUTLINE C
1. Place 100 ml or other
measured sample in flask.
G.	CALCULATION
Chloride (as CI), mg/L = (A-B) x N x 35,450
ml of sample
A = ml AgNOs used for titration of sample
B = ml AgNOa used for blank
N = normality of AgN03
H.	EXAMPLE
Sample size = 100 ml
A = ml AgN03 used for sample = 10.0 ml
B = ml AgNOj used for blank = 0.4 ml
N = normality of AgN03 = 0.0141 N
solution
Chloride, mg/L = (10 0 - 0-4) x (0.0141) x 35,450
100
= 48 mg/L
PROCEDURE
?
2. Add 1 ml chromate indicator.
-A-
7
3. Place flask on magnetic stirrer and
titrate with standard silver nitrate.

-------
Laboratory 405
I. SPECIAL NOTES
1.	Sulfide, thiosulfate, and sulfite ions interfere, but can be
removed by treatment with 1 ml of 30 percent hydrogen
peroxide (H202).
2.	Highly colored samples must be treated with an aluminum
hydroxide suspension and then filtered.
3.	Orthophosphate in excess of 25 mgIL and iron in excess of
10 mgIL also interfere.
4.	If the pH of the sample is not between 7 to 10, adjust with 1
N sulfuric acid or 1 N sodium hydroxide.
5.	Procedure for standardization of AgN03:
a.	Add 10 ml (1 mg CI) standard sodium chloride solution
to a clean 250 ml Erlenmeyer flask.
b.	Add 90 ml distilled water.
c.	Titrate as in Section F above.
Normality, N, _ ml NaCI standard x 0.0141
aQN03 ml AgNOs used in titration
EXAMPLE
10.0 ml NaCI standard used
10.0 ml AgNOs used in titration
0.0141 N = normality of NaCI standard
Normality, N, = 10.0 ml x 0.0141
AgN°3	icTml
= 0.0141
J. REFERENCE
See page 303, STANDARD METHODS, 14th Edition.
QUESTION
Write your answer in a notebook and then compare your
answer with the one on page 461.
16.5E What ions interfere with the chloride test and how are
they removed?
5. Chlorine Residual (Total)
A. DISCUSSION
The many uses of chlorination in wastewater treatment in-
clude disinfecting, reducing BOD, odor control, improving
scum and grease removal, controlling activated sludge bulk-
ing, foam control, and use as an aid in chemical coagulation.
The most important use of chlorine in the treatment of waste-
water is for disinfection. The amount of residual chlorine re-
maining in the treated wastewater after passing through a con-
tact basin or chamber may be related to the numbers of col-
iform bacteria allowed in the effluent by regulatory agencies. In
many cases the residual chlorine must be reduced (for most
practical purposes removed) before final discharge to a receiv-
ing stream for protection of fish and other aquatic life.
Chlorine reacts quickly (within minutes) and completely with
ammonia in wastewater to produce monochloramine and
dichloramine. Residual chlorine in the monochloramine or
dichloramine state is termed "combined residual chlorine."
With the amount of ammonia usually found in wastewater, the
chlorine residual will contain all combined chlorine and no free
chlorine. Because chlorine residual in wastewater is in a com-
(Chlorine Residual)
bined state, the determination of residual chlorine presents
special problems.
B.	WHAT IS TESTED?
Common Range, mg IL
Sample	(After 30 minutes)
Effluent	0.5 to 2.0 mgIL
C.	METHODS
The lodometric Method for measuring residual chlorine is
used for samples containing wastewater, such as plant
effluents or receiving waters. The DPD Titrimetric Method is
applicable to wastewaters which do not contain iodine-
reducing substances. This method also has the advantage that
it can be modified in order to determine free residual chlorine,
monochloramine and dichloramine. Colorimetric tests for re-
sidual chlorine have special limitations and should generally be
avoided in wastewater. The AMPEROMETRIC^* Titration
Method gives the best results, but the titrator instrument is
expensive.
D.	APPARATUS REQUIRED
lodometric Method
Graduated cylinder, 250 ml
Pipets, 5 and 10 ml
Erlenmeyer flask, 500 ml
Buret, 5 ml
Magnetic stirrer
DPD Titrimetric Method
Graduated cylinder, 100 ml
Pipets, 1 and 10 ml
Erlenmeyer flask, 250 ml
Buret, 10 ml
Magnetic stirrer
Amperometric Titration Method
See page 322, STANDARD METHODS, 14th Edition, and
manufacturer of amperometric titrator's instruction manual.
E.	REAGENTS
(Standardized solutions may be purchased from chemical
suppliers.)
lodometric Method
1.	Standard phenylarsine oxide (PAO) solution, 0.00564 N.
Dissolve approximately 0.8 g phenylarsine oxide powder in
150 ml 0.3 N NaOH solution. After settling, remove upper
110 ml of this solution into 800 ml distilled water and mix
thoroughly. Adjust pH up to between 6 and 7 with 6 N HCI
and dilute to 950 ml with distilled water. To standardize this
solution accurately, measure 5 to 10 ml of freshly stan-
dardized 0.0282 N iodine solution into a flask and add 1 ml
Kl solution. Titrate with phenylarsine oxide solution, using
starch solution as an indicator. Adjust to exactly 0.00564 N
and recheck against the standard iodine solution: 1.00 ml =
200 fig available chlorine. CAUTION: Toxic - avoid inges-
tion.
2.	Potassium iodide (Kl), crystals.
3.	Acetate buffer solution, pH 4.0. Dissolve 146 g anhydrous
14 Amperometric (am-PURR-o-MET-rick). A method of measurement that records electric current flowing or generated, rather than recording
voltage. Amperometric titration is a means of measuring concentrations of certain substances in water.

-------
406 Treatment Plants
(Chlorine Residual)
NaC2H302, or 243 g NaC2H302 • 3 H20, in 400 ml distilled
water, add 480 g concentrated acetic acid, and dilute to 1
liter with distilled water.
4.	Standard iodine titrant, 0.0282 N. Dissolve 25 g Kl in a little
distilled water in a 1-liter volumetric flask, add the proper
amount of 0.1 N iodine solution exactly standardized to
yield a 0.0282 N solution, and dilute to 1 liter. Store in
amber bottles or in the dark, protecting the solution from
direct sunlight at all times and keeping it from all contact
with rubber.
5.	Starch indicator. Make a thin paste of 6 g of potato starch in
a small quantity of distilled water. Pour this paste into one
liter of boiling, distilled water. Allow to boil for a few minutes,
then settle overnight. Remove the clear supernatant and
save; discard the rest. For preservation, add 1.25 grams
salicylic acid or 4 grams zinc chloride.
DPD Titrimetric Method
1.	1 + 3 H2S04: CARE FULL Y add 10 ml concentrated sulfuric
acid to 30 ml distilled water. Cool.
2.	Phosphate Buffer Solution: Dissolve 24 grams anhydrous
disodium hydrogen phosphate, Na2HP04, and 46 grams
anhydrous potassium dihydrogen phosphate, KH2P04, in
distilled water. Combine with 100 ml distilled water in which
0.800 grams (ethylenedinitrilo) tetraacetic acid, sodium salt,
have been dissolved. Dilute to 1 liter with distilled water and
add 0.02 grams mercuric chloride, HgCI2, as a preservative.
3.	DPD Indicator Solution: Dissolve 1 gram DPD Oxalate*, or
1.5 grams p-amino-N:N-diethylaniline sulfate in chlorine-
free distilled water containing 8 ml 1 +3 H2S04 and 0.2
grams (ethylenedinitrilo) tetraacetic acid, sodium salt. Make
up to 1 liter, store in brown glass-stopper bottle and discard
when discolored.
4. Standard Ferrous Ammonium Sulfate (FAS) Titrant,
0.00282 N: Dissolve 1.106 grams Fe (NH4)? (S04)2 • 6 H,0
in distilled water containing 1 ml of 1 +3 H2S04 and make
up to 1 liter with freshly boiled and cooled distilled water.
The normality can be checked using potassium dichromate
(see method under Procedure 9, COD Test).
F.	VOLUME OF SAMPLE
For residual chlorine concentrations of 10 mgIL or less, take
a 200 ml sample for titration. For residuals greater than 10
mg/L, use proportionately less sample.
G.	PROCEDURE
lodometric Method
1.	Pipet 5.00 ml 0.00564 N PAO solution into an Erlenmeyer
flask.
2.	Add excess Kl (approximately 1 g).
3.	Add 4 ml acetate buffer solution, or enough to lower the pH
to between 3.5 and 4.2.
4.	Pour in 200 ml of sample.
5.	Mix with magnetic stirrer.
6.	Add 1 ml starch solution just before titration.
7.	Titrate with 0.0282 N Iodine to the first appearance of blue
color which remains after complete mixing.
* Eastman Chemical No. 7102 or equivalent.

-------
lodometric Method
OUTLINE OF PROCEDURE
Laboratory 407
(Chlorine Residual)
1. Place 5.00 ml
phenylarsirie
oxide solution
in Erienmeyer
flask.
2.
Add excess
Kl
(approx 1 g).
3.
Add 4 ml
acetate buffer
solution.
Add 200 ml
sample.
5. Mix with
stirring
rod.
6. Add 1 ml
starch
solution.
Titrate until
blue color
first appears
and remains
after mixing.

-------
408 Treatment Plants
(Chlorine Residual)
DPD Titrimetric Method
1.	Place 5 ml each of buffer reagent and DPD indicator in a
250 ml flask and mix.
2.	Add 2 drops (0.1 ml) Kl solution and mix.
3.	Add 100 ml of sample and mix.
4.	Let stand for 2 minutes and then titrate with FAS titrant.
H. CALCULATIONS
lodometric Method
Total Residual Chlorine, mgIL = (A - 5B) x 200
C
A = ml 0.00564 N PAO
B = ml 0.0282 N l2
C = ml of sample used
EXAMPLE:
Titration of a 200 ml sample requires 0.3 ml l2 solution and 5
ml of PAO.	f
Total Residual Chlorine, _ (A - 5B) x 200
mgIL		^	
j5-(5x 0.3)} (200)
200 ml
= (5-1.5)
= 3.5 mgIL
DPD Titrimetric Method
For a 100 ml sample, 1.00 ml standard FAS titrant = 1.0
mgIL residual chlorine.
EXAMPLE:
100 ml of sample required 3.4 mgIL standard FAS titrant,
therefore
Total Residual Chlorine, = 3.4 mgIL
mgIL
I. REFERENCES
lodometric Method: See page 318, STANDARD METHODS,
14th Edition.
DPD Titrimetric Method: See page 329, STANDARD
METHODS, 14th Edition.
QUESTIONS
Write your answers in a notebook and then compare your
answers with those on page 461.
16.5F Why should plant effluents be chlorinated?
16.5G Discuss the important advantages and disadvantages
between the iodometric titration and amperometric ti-
tration methods of measuring chlorine residual.
ewp of Lessoff 6 of 9 ues-sofos
ON
LA0O(?AT6f?V PQOCeVUVeG^CMmitrfQV
Work the next portion of the discussion and review questions
before continuing with Lesson 7.
DISCUSSION AND REVIEW QUESTIONS
Chapter 16. LABORATORY PROCEDURES AND CHEMISTRY
(Lesson 6 of 9 Lessons)
Write the answers to these questions in your notebook. The
question numbering continues from Lesson 5.
28.	What precautions must be taken when conducting the
total alkalinity test?
29.	What safety precautions must be considered when per-
forming the COD test?
30.	Why is the COD test run?
31.	What are the sources of chloride in wastewater?
32.	Why is the effluent from a treatment plant chlorinated?

-------
Laboratory 409
CHAPTER 16. LABORATORY PROCEDURES AND CHEMISTRY
(Lesson "7 of 9 Lessons)
6. Coliform Group Bacteria
A.	DISCUSSION
Most probable numbers of coliform bacteria are estimated to
indicate the presence of bacteria originating from the intestines
of warm-blooded animals. High coliform counts indicate the
usefulness of water may have been impaired. Coliform bac-
teria are generally considered harmless, but their presence
may be indicative of the presence of disease-producing or-
ganisms that may be found with them.
The coliform group of bacteria comprises all the aerobic and
FACULTATIVE15 anaerobic gram negative, nonspore-forming
rod-shaped bacteria that ferment lactose (a sugar) within 48
hours at 35°C. In general, coliform bacteria can be divided into
a fecal and a non-fecal group. The fecal coliform can grow at a
higher temperature (45°C) than the non-fecal coliform.
B.	TEST METHODS
NPDES approved test procedures list two methods for Total
Coliform analysis. They are: The MPN (Most Probable
Number) Method and the Membrane Filter (MF) Method. Of
the two methods, the MPN procedure is most applicable for
wastewater.
MPN METHOD
The multiple tube coliform test has been a standard method
for determining coliform group bacteria since 1936. In this pro-
cedure tubes of lactose broth or lauryl tryptose broth are inocu-
lated with dilutions of a wastewater or water sample. The col-
iform density is then calculated from statistical probability for-
mulas that predict the most probable number (MPN) of col-
iforms necessary to produce certain combinations of gas-
positive and gas-negative tubes in the series of inoculated
tubes.
There are three distinct test stages of coliform testing using
the MPN method: the presumptive test, the confirmed test, and
the completed test.
MF METHOD
This method was introduced as a tentative method in 1955.
The basic procedure involves filtering a known volume of water
through a membrane filter of optimum pore size for full bacteria
retention. As the water passes through the pores, bacteria are
entrapped on the upper surface of the filter. The membrane
filter is then placed in contact with either a paper pad saturated
with liquid medium or directly over an agar medium to provide
nutrients for bacterial growth. Following incubation under pre-
scribed conditions of time, temperature, and humidity, the cul-
tures are examined for coliform colonies that are counted and
recorded as a density of coliforms per 100 ml of water sample.
There are certain important limitations to membrane filter
methods. Some types of samples cannot be filtered because of
turbidity, high non-coliform bacterial densities, or heavy metal
compounds.
C. WHAT IS TESTED?
Sample
Common Rang**, MPN/100 ml
Total Coliform Fecal Coliform
Effluents:
Primary
Chlorinated
Secondary
Receiving Waters
5,000 to 2,000,000 1,000 to 500,000
50 to 1,000
50 to 1,000,000
<2 to 200
<2 to 1,000
D. MATERIALS REQUIRED
1.	SAMPUNG BOTTLES
Bottles of glass or other material which are watertight, resis-
tant to the solvent action of water and capable of being
sterilized may be used for bacteriologic sampling. Plastic bot-
tles made of nontoxic materials have been found to be satisfac-
tory and eliminate the possibility of breakage during transport.
The bottles should hold a sufficient volume of sample for all
tests, permit proper washing, and maintain the samples uncon-
taminated until examinations are complete.
Before sterilization by autoclave, add 0.1 ml 10 percent
sodium thiosulfate per 4 ounce bottle (120 mis). This will neu-
tralize a sample containing about 15 mgIL residual chlorine. If
the residual chlorine is not neutralized, it would continue to be
toxic to the coliform organisms remaining in the sample and
give false results.
When filling bottles with sample, do not flush out sodium
thiosulfate or contaminate bottle or sample. Fill bottles approx-
imately three-quarters full and start test in laboratory within six
hours. If the samples cannot be processed within one hour,
they should be held below 10°C for not longer than six hours.
2.	MEDIA PREPARATION
Careful media preparation is necessary for meaningful bac-
teriological testing. Attention must be given to the quality, mix-
ing, and sterilization of the ingredients. The purpose of this
care is to assure that if the bacteria being tested for are indeed
present in the sample, every opportunity is presented for the
development and ultimate identification. Much bacteriological
identification is done by noting changes in the medium; con-
sequently, the composition of the medium must be stan-
dardized. Much of the tedium of media preparation can be
avoided by purchase of dehydrated media (Difco, BBL, or
equivalent) from local scientific supply houses. The operator is
advised to make use of these products; and, if only a limited
amount of testing is to be done, consider using tubed, pre-
pared media.
GLASSWARE
All glassware must be thoroughly cleansed using a suitable
detergent and hot water (160°F or 71 °C), rinsed with hot water
(180°F or 82°C) to remove all traces of residual detergent, and
finally rinsed with distilled or deionized water.
15 Facultative (FACK-ul-TAY-tive). Facultative bacteria can use either molecular (dissolved) oxygen or oxygen obtained from food materials
such as sulfate or nitrate ions. In other words, facultative bacteria can live under aerobic or anaerobic conditions.

-------
410 Treatment Plants
(Coliform)
WATER
Only distilled water or demineralized water which has been
tested and found free from traces of dissolved metals and
bactericidal and inhibitory compounds may be used for prepa-
ration of culture media.
BUFFERED16 DILUTION WATER
Prepare a stock solution by dissolving 34 grams of KH2P04
in 500 ml distilled water, adjusting the pH to 7.2 with 1 N NaOH
and dilute to one liter. Prepare dilution water by adding 1.25 ml
of the stock solution and 5.0 ml magnesium sulfate (50 grams
MgS04 • 7 H20 dissolved in one liter of water) to 1 liter distilled
water. This solution can be dispersed into various size dilution
blanks or used as a sterile rinse for the membrane filter test.
MEDIA - MPN (TOTAL AND FECAL COLIFORM)
1.	Lactose Broth or Lauryl Tryptose Broth
For the presumptive coliform test, dissolve the recom-
mended amount of the dehydrated medium in distilled wa-
ter. Dispense solution into fermentation tubes containing an
inverted glass vial (see illustration ®f tube with vial on page
413).
2.	Brilliant Green Bile Broth
For the confirmed coliform test, dissolve 40 grams of the
dehydrated medium in one liter of distilled water. Dispense
and sterilize as with Lactose Broth.
3.	EC Broth
For the fecal coliform test, dissolve 37 grams of the de-
hydrated medium in one liter of distilled water. Dispense
and sterilize as with Lactose Broth.
MEDIA - MEMBRANE FILTER METHOD (TOTAL AND FECAL
COLIFORM)
1.	M-Endo Broth
Prepare this medium by dissolving 48 grams of the de-
hydrated product in one liter of distilled water which con-
tains 20 ml of ethyl alcohol per liter. Heat solution to boiling
only - DO NOT AUTOCLAVE. Prepared media should be
stored in refrigerator and used within 96 hours.
2.	LES Endo Agar
Prepare this medium, used for the two-step procedure,
as per instructions found on the bottle.
3.	M-FC Media
Rehydrate in distilled water containing 10 ml of 1 percent
Rosolic Acid in 0.2 N NaOH. Heat just to boiling then cool to
below 45°C. DO NOT AUTOCLAVE. Prepared media stored
in the refrigerator should be used within 96 hours.
The Rosolic Acid solution should be stored in the dark
and discarded after 2 weeks.
AUTOCLAVING
Steam autoclaves are used for the sterilization of the liquid
media and associated apparatus. They sterilize (killing of all
organisms) at a relatively low temperature of 121°C within 15
minutes by utilizing moist heat.
Components of the media, particularly sugars such as lac-
tose, may decompose at higher temperatures or longer heat-
ing times. For this reason adherence to time and temperature
18 Buffer. A solution or liquid whose chemical makeup neutralizes
schedules is vital. The maximum elapsed time for exposure of
the medium to any heat (from the time the autoclave door is
closed to unloading) is 45 minutes. Preheating the autoclave
can reduce total heating time.
Autoclaves operate in a manner similar to the familiar
kitchen pressure cooker:
1.	Water is heated in a boiler to produce steam.
2.	The steam is vented to drive out air.
3.	The steam vent is closed when the air is gone.
4.	Continued heat raises the pressure to 15 Ibs/sq in (1.05
kg/sq cm) (at this pressure, pure steam has a temperature
of 121°C).
5.	The heat and pressure are maintained for 15 minutes.
6.	Turn off the heat.
7.	Open the steam vent and slowly vent the steam until
atmospheric pressure is reached. (Fast venting will cause
the liquids to boil and overflow tubes.)
8.	Sterile material is removed to cool.
In autoclaving fermentation tubes, a vacuum is formed in the
inner tubes. As the tubes cool, the inner tubes are filled with
sterile medium. Capture of gas in this inner tube from the cul-
ture of bacteria is the evidence of fermentation and is recorded
as a POSITIVE TEST.
MEDIA STORAGE
Culture media should be prepared in batches of such size
that the entire batch will be used in less than one week.
E. PROCEDURE FOR TESTING TOTAL COLIFORM
BACTERIA - MPN METHOD
1.	GENERAL DISCUSSION
The test for coliform bacteria is used to measure the suitabil-
ity of a water for human use. The test is not only useful in
determining the bacterial quality of a finished water, but it can
be used by the operator in the treatment plant as a guide to
achieving a desired degree of treatment.
Coliform bacteria are detected in water by placing portions of
a sample of the water in lactose broth. Lactrose broth is a
standard bacteriological medium containing lactose (milk)
sugar in tryptose broth. The coliform bacteria are those which
will grow in this medium at 35°C temperature and ferment and
produce gas from the sugar within 48 hours. Thus to detect
these bacteria the operator need only inspect fermentation
tubes for gas. In practice, multiple fermentation tubes are used
in dilutions for each sample. A schematic of the confirmed test
procedure is shown in Figure 16.11.
2.	MATERIALS NEEDED
a.	Fifteen sterile tubes of lactose or lauryl tryptose broth
are needed for each sample.
b.	Use five tubes for each dilution.
c.	Dilution tubes or blanks containing 99 ml of sterile buf-
fered distilled water.
d.	Quantity of 1 ml and 10 ml pipets.
e.	Incubator set at 35 ± 0.5 °C.
f.	Thermometer verified to be accurate by comparison
with National Bureau of Standards (NBS) certified
thermometer.
acids or bases without a great change in pH.

-------
Laboratory 411
(Coliform)
TOTAL COLIFORM
1. Presumptive Test
no gas
incubate 24 hrs more
no gas
no Coliform present
discard tubes
gas produced
continued with confirmed test
(and/or fecal test)
Inoculate in lactose or lauryl tryptose; incubate 24 ± 2 hrs
at 35°C ± 0.5°C
2. Confirmed Test
no gas
Coliform absent
gas produced
Coliform group confirmed
Calculate confirmed MPN
inoculate (with loop or applicator stick) brilliant green
bile broth. Incubate 48 hrs ± 3 hr at 35°C ± 0.5°C
FECAL COLIFORM
1.	Presumptive Test
(same as for TOTAL COLIFORM)
2.	Fecal Coliform Test
no gas
Fecal Coliform absent
gas produced
Fecal Coliform present
Calculate fecal MPN
Inoculate EC Broth; incubate 24 hrs at 44.5°C ± 0.2°C
Fig. 16.11 Schematic outline of procedure
for Total and Fecal Coliform - MPN Method

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412 Treatment Plants
(Coliform)
3. TECHNIQUE FOR INOCULATION ANDIOR DILUTION OF
SAMPLE (FIG. 16.12)
All inoculations and dilutions of wastewater specimens must
be accurate and should be made so that no contaminants from
the air, equipment, clothes or fingers reach the specimen,
either directly or by way of the contaminated pipet. Clean,
sterile pipets must be used for each separate sample.
a.	Shake the specimen bottle vigorously 20 times before
removing sample volumes.
b.	Pipet 1.0 ml of sample directly into the first five lactose
tubes. (It is important to realize that the sample volume
applied to the first five tubes will depend upon the type
of water being tested. The sample volume applied to
each tube can vary from 10 ml (or more) for high quality
waters to as low as 10"5 or 0.00001 ml (applied as 1 ml
of a diluted sample) for raw wastewater specimens.)
NOTE: When delivering the sample into the culture medium,
deliver sample portions of 1 ml or less down into the culture
tube near the surface of the medium. DO NOT deliver small
sample volumes at the top of the tube and allow them to run
down inside the tube; too much of the sample will fail to reach
the culture medium.
NOTE: Use 10 ml pipets for 10 ml sample portions, and 1 ml
pipets for portions of 1 ml or less. Handle sterile pipet only near
the mouthpiece, and protect the delivery end from external
contamination.
c.	Pipet 1/10 ml or 0.1 ml of raw sample into each of the
next five lactose broth tubes. This makes a 0.1 dilution.
d.	To make the 0.01 dilution, place 1 ml of well mixed raw
sample into 99 ml of sterile buffered dilution water. Mix
thoroughly by shaking. This bottle will be labeled Bottle
A.
e.	Into each of the next five lactose broth tubes place
directly 1 ml of the 0.01 dilution from bottle A.
At this point you have 15 tubes inoculated and can place
these three sets of tubes in the incubator; however, your sam-
ple specimen may show gas production in all fermentation
tubes. This means your sample was not diluted enough and
you have no usable results. To obtain usable results it is rec-
ommended that the first time a sample is anlayzed that thirty
tubes having a range of six dilutions be setup. In most cases
this will give usable results.

-------
Laboratory 413
(Coliform)
r\
WATER SAMHE


t al RAW SAMPLE
I0TTLI A
W al smut
BUFFERED
DILUTION
WATER
I I
1 ftl TO EACH TUBE
0
Q

(.1 al TO EACH TUBE
1	r
£
KZS
1 al TO EACH TUIE
T	1	1	1
6
0
n
$	^	^
0.1 III TO EACH TUIE
1	I	I	I
q q	fO	p
q	P	q	D
ni	nh	ini	iri
lyj	y;	iyJ	yi
rv 'r
Oj U
iH'
DIIUTHH
10 iiuitkm
0.1
o.tt
0.001
BOTH! I
Mai STERILE
BUFFERED
DILUTION
WATER
1	r
P £
Q C
| ry in
t al TO EACH IUIE
-i	1	r
P P p
if .
y y
o p
n in1
ill; !! !'
T

0.1 al TO EACH TUBE
I I I I
P	P
a	a
H: ini	iH!
[ijj
T
g
n|
J
(.0001
0.00001
MCUUIE All TUBES AT M* C 4 0.5*C FOI14 HOURS
6AS HI HMER VUl
IS A ~ TEST RESULT
P
P
Fig. 16.12 Conform bacteria test

-------
414 Treatment Plants
(Coliform)
f.	To make a 1/1000 or 0.001 dilution, add 0.1 mlfromthe
1/100 dilution bottle (Bottle A) directly into each tube of
five more lactose broth tubes.
g.	To make a 1/10000 or 0.0001 dilution, take 1 ml from
Bottle A and place this 1 ml into .99 ml of sterile buffered
dilution water. Mix diluted sample thoroughly by shak-
ing. This bottle will be called Bottle B.
h.	From the 0.0001 dilution (Bottle B), pipet 1.0 ml of
sample directly into each tube. Set up five tubes with
this dilution.
i.	Tomakea 1/100000 or 0.00001 dilution, pipet 0.1 ml of
sample directly into each tube. Set up five tubes with
this dilution.
The first time a sample is analyzed, thirty tubes of lactose
broth should be prepared. Once the appropriate dilutions are
established that give usable results for determining the MPN
Index, only fifteen tubes need be prepared for subsequent
samples to be analyzed.
4. INCUBATION (TOTAL COLIFORM)
a.	24-HOUR LACTOSE BROTH PRESUMPTIVE TEST
Place all inoculated lactose broth tubes in 35°C ±
0.5°C incubator. After 24 ± 2 hours have elapsed,
examine each tube for gas formation in inverted vial
(inner tube). Mark (+) on report form such as shown on
Figure 16.13 for all tubes that show presence of gas.
Mark (-) for all tubes showing no gas formation. Save
all positive (+) tubes for confirmation test. The negative
(-) tubes must be reincubated for an additional 24
hours.
b.	48-HOUR LACTOSE BROTH PRESUMPTIVE TEST
Record both positive and negative tubes at the end of
48 ± 3 hours. Save all positive tubes for confirmation
test.
c.	24-HOUR BRILLIANT GREEN BILE CONFIRMATION
TEST.
Confirm all presumptive tubes that show gas at 24 or
48 hours. Transfer, with the aid of a sterile 3 mm
platinum wire loop (or sterile wood applicator), one
loop-full of the broth from the lactose tubes showing
gas, and inoculate a corresponding tube of BGB (Bril-
liant Green Bile) broth by mixing the loop of broth in the
BGB broth. Discard all positive lactose broth tubes after
transfering is completed.
Always sterilize inoculation loops and needles in
flame immediately before transfer of culture; do not lay
loop down or touch it to any nonsterile object before
making the transfer. After sterilization in a flame, allow
sufficient time for cooling, in the air, to prevent the heat
of the loop from killing the bacterial cells being transfer-
red. Wooden sterile applicator sticks also are used to
transfer cultures, especially in the field where a flame is
not available for sterilization. If using hardwood
applicators, discard after use.
After 24 hours have elapsed, inspect each of the
BGB tubes for gas formation. Those with any amount of
gas are considered positive and are so recorded on the
data sheet. Negative BGB tubes are reincubated for an
additional 24 hours.
d. 48-HOUR BRILUANT GREEN BILE CONFIRMATION
TEST
1.	Examine tubes for gas at the end of the 48 ± 3 hour
period. Record both positive and negative tubes.
2.	Complete reports by determining MPN Index and
recording MPN on work sheets.
5.	RECORDING RESULTS
Results should be recorded on data sheets prepared espe-
cially for this test. An example is shown in Figure 16.13.
6.	METHOD OF CALCULATION OF THE MOST PROBABLE
NUMBER (MPN)
Select the highest dilution with all positive tubes, before a
negative tube occurs, plus the next two dilutions.
DATE NO. SOURCE
n
kmer/'&n
WW
ML
24
48
RESUMPTIVE
CONFIRMED
I o
1
O.I
ML

O
1
0.1
t
+

1
+
4-
+

—
+
-


-
-
24
+
4
—
-

t
+
—
—
—
—
	










+
f

+

-
-
-
48



4



-
—
-
-
—



MPN/lOOml
ML = ml of sample; 10 ml, 1 ml and 0.1 ml.
24 = results after 24 hours of incubation.
48 = results after 48 hours of incubation.
Number of Positive Tubes	5, 2, 0
Fig. 16.13 Recorded coliform test results

-------
Laboratory 415
(Coliform)
EXAMPLE NO. 1
16.14)
Dilutions
Readings
Read MPN as
Report Results as
Select the underlined dilutions (see Fig.
49 per 100 ml from Table 16.6
49,000/100 ml
We added three zeros to 49 because we started with the -2
dilution and Table 16.6 starts three dilution columns to the left
(-1 or 0.1 ml, 0 or 1 ml, and 1 or 10 ml).
EXAMPLE NO. 2 — Select the underlined dilutions
Dilutions
Readings
Read MPN as
Report MPN as
0 -1 -2 -3 -4 -5
5 5 5 5 0 0
23 per 100 ml from Table 16.6
230,000 per 100 ml
If positive tubes extend beyond three chosen dilutions, in-
clude positives beyond chosen dilutions by moving them for-
ward.
EXAMPLE NO. 3

Dilutions
0
-1
-2
-3
-4
-5
3 -4 -5








Readings
5
1
0
1
0
0
2 0 0
This becomes
5
1
1
0
0
0
The MPN is
460 per 100 ml
When it is desired to summarize with a single MPN value the
results from a series of samples, the geometric mean, the
arithmetic mean, or the median may be used. See Chapter 17,
Section 17.4, "Mean and Median," for details on how to calcu-
late these values.
The MPN for combinations not appearing in the table given
or for other combinations of tubes or dilutions, may be esti-
mated by the formula:
MPN/100 ml =
V[
No. of positive tubes x 100
ml sample in
negative tubes
]-[
ml sample in
all tubes
]

-------
416 Treatment Plants
(Coliform)
DILUTION
o.
6AS
vrv
GAS
FOR EXAMPLE NO. 1
6AS GAS GAS
W
GAS
\z/
GAS
V3>
GAS
6AS
GAS
0.1
s
GAS
n
jj,
GAS
GAS
19
GAS
ti.
GAS
0.01
0.001
0.0001
0.00001
n
IU
GAS
NO GAS


§
R

n
I I



HO GAS NO GAS


0
n
i



L


-J
v_y
r
n
4
n


il
W
(O
NO GAS NO GAS NO GAS NO GAS NO GAS
RESULTS
S oil of S
5 onl of 5
5 out H 5
2 out of S
0 out of 5
0 oil of 5
Fig. 16.14 Results of coliform test

-------
Laboratory 417
TABLE 16.6	(Coliform)
MPN INDEX FOR VARIOUS COMBINATIONS OF POSITIVE AND NEGATIVE RESULTS
IN A PLANTING SERIES OF FIVE 10-ml, FIVE 1-ml AND
FIVE 0.1-ml PORTIONS OF SAMPLE

Number of tubes giving positive
MPN Index

reaction out of


Five 10-ml
Five 1-ml
Five 0.1 ml
(organisms
portions
portions
portions
per 100 ml)
0
0
0
<2
0
0
1
2
0
0
2
4
0
1
0
2
0
1
1
4
0
1
2
6
0
2
0
4
0
2
1
6
0
3
0
6
1
0
0
2
1
0
1
4
1
0
2
6
1
0
3
8
1
1
0
4,
1
1
1
6
1
1
2
8
1
2
0
6
1
2
1
8
1
2
2
10
1
3
0
8
1
3
1
10
1
4
0
11
2
0
1
5
2
0
1
7
2
0
2
9
2
0
3
12
2
1
0
7
2
1
1
9
2
1
2
12
2
2
0
9
2
2
1
12
2
2
2
14
2
3
0
12
2
3
1
14
2
4
0
15
3
0
0
8
3
0
1
11
3
0
2
13
3
1
0
11
3
1
1
14
3
1
2
17
3
1
3
20
3
2
0
14
3
2
1
17
3
2
2
20
3
3
0
17
3
3
1
21

-------
418 Treatment Plants
(Coliform)	TABLE 16.6 (Cont'd)
MPN INDEX FOR VARIOUS COMBINATIONS OF POSITIVE AND NEGATIVE RESULTS
IN A PLANTING SERIES OF FIVE 10-ml, FIVE 1-ml AND
FIVE 0.1-ml PORTIONS OF SAMPLE

Number of tubes giving positive
MPN Index

reaction out of


Five 10-ml
Five 1-ml
Five 0.1 ml
(organisms
portions
portions
portions
per 100 ml)
3
4
0
21
3
4
1
24
3
5
0
25
4
0
0
13
4
0
1
17
4
0
2
21
4
0
3
25
4
1
0
17
4
1
1
21
4
1
2
26
4
2
0
22
4
2
1
26
4
2
2
32
4
3
0
27
4
3
1
33
4
3
2
39
4
4
0
34
4
4
1
40
4
5
0
41
4
5
1
48
5
0
0
23
5
0
1
31
5
0
2
43
5
0
3
58
5
0
4
76
5
1
0
33
5
1
1
46
5
1
2
63
5
1
3
84
5
2
0
49
5
2
1
70
5
2
2
94
5
2
3
120
5
2
4
148
5
2
5
177
5
3
0
79
5
3
1
109
5
3
2
141
5
3
3
175
5
3
4
212
5
3
5
253
5
4
0
130
5
4
1
172
5
4
2
221
5
4
3
278

-------
Laboratory 419
TABLE 16.6 (Cont'd)	(Coliform)
MPN INDEX FOR VARIOUS COMBINATIONS OF POSITIVE AND NEGATIVE RESULTS
IN A PLANTING SERIES OF FIVE 10-ml, FIVE 1-ml AND
FIVE 0.1-ml PORTIONS OF SAMPLE

Number of tubes giving positive
MPN Index

reaction out of

|
Five 10-ml
Five 1-ml
Five 0.1 ml
(organisms
portions
portions
portions
per 100 ml)
5
4
4
345
5
4
5
426
5
5
0
240
5
5
1
348
5
5
2
542
5
5
3
920
5
5
4
1600
5
5
5
>2400
F. TEST FOR FECAL COUFORM BACTERIA - MPN
1.	GENERAL DISCUSSION
Many regulatory agencies are measuring the bacteriological
quality of water using the fecal coliform test. This test more
reliably indicates the potential presence of pathogenic or-
ganisms than do tests for total coliform group of organisms.
The procedure described is an ELEVATED TEMPERATURE
TEST FOR FECAL COUFORM BACTERIA.
2.	MATERIALS NEEDED
Equipment required for the tests are the same as those re-
quired for the 24-Hour Lactose Broth Presumptive Test, plus a
water bath set at 44.5 ± 0.2°C, EC Broth media, and a ther-
mometer certified against an NBS thermometer.
3.	PROCEDURE
a.	Run lactose broth or lauryl tryptose broth presumptive
test.
b.	After 24 hours temporarily retain all gas-positive tubes.
c.	Label a tube of EC broth to correspond with each gas-
positive tube of broth from presumptive test.
d.	Shake or mix positive presumptive tubes by rotating
them. Transfer one loop-full of culture from each gas-
positive culture in presumptive test to the corre-
spondingly labeled tube of EC broth.
e.	Incubate EC broth tubes 24 ± 2 hours at 44.5°C ±
0.2°C in a waterbath with water depth sufficient to come
up at least as high as the top of the culture medium in
the tubes. Place in waterbath AS SOON AS POSSIBLE
after inoculation and always within 30 minutes after in-
oculation.
f.	After 24 hours remove the rack of EC cultures from the
waterbath, shake gently, and record gas production for
each tube. Gas in any quantity is a positive test.
g.	As soon as results are recorded, discard all tubes. This
is a 24-hour test for EC broth inoculations and not a
48-hour test.
h.	Transfer any additional 48-hour gas-positive tubes from
the presumptive test to correspondingly labeled tubes
of EC broth. Incubate for 24 ± 2 hours at 44.5°C ±
0.2°C and record results on data sheet.
i.	Codify results using the same procedure as for total
conforms and determine MPN of fecal conforms per 100
ml of sample (Fig. 16.13).
EXAMPLE
ml portion	10 1 0.1
readings	5 2 1
Read MPN as	70 per 100 ml from Table 16.6
Reports results as MPN - 70 per 100 ml
of fecal conforms
G. MEMBRANE FILTER METHOD - TOTAL COUFORM
1.	GENERAL DISCUSSION
In addition to the fermentation tube test for coliform bacteria,
another test is used for these same bacteria in water analysis.
This test uses a cellulose ester filter, called a membrane filter,
the pore size of which can be manufactured to close toler-
ances. Not only can the pore size be made to selectively trap
bacteria from water filtered through the membrane, but nutri-
ents can be diffused up through the membrane to grow these
bacteria into colonies. These colonies are recognizable as col-
iform because the nutrients include fuchsin dye which pecul-
iarly colors the colony. Knowing the number of colonies and
the volume of water filtered, the operator can then compare the
water tested with water quality standards.
A two step pre-enrichment technique is included at the end
of this section for samples which have been chlorinated.
Chlorinated bacteria which are still living have had their en-
zyme systems damaged and require a 2-hour enrichment
media before contact with the selective M-Endo Media.
2.	MATERIALS NEEDED
a.	One sterile membrane filter having a 0.45m pore size
b.	One sterile 47 mm petri dish with lid

-------
420 Treatment Plants
(Coliform)
c.	One sterile funnel and support stand
d.	Two sterile pads
e.	One receiving flask (side-arm, 1000 ml)
f.	Vacuum pump, trap, suction or vacuum gage, connec-
tion sections of plastic tubing, glass "T" hose clamp to
adjust pressure bypass
g.	Forceps (round-tipped tweezers), alcohol, Bunsen
Burner, grease pencil
h.	Sterile buffered distilled water for rinsing
i.	M-Endo Media
j. Sterile pipets — two 5 ml graduated pipets and one, 1
ml pipetfor sample or one 10 ml pipetfor larger sample.
Quantity of one ml pipets if dilution of sample is neces-
sary. Also, quantity of dilution water blanks if dilution of
sample is necessary.
k. One moist incubator at 35°C; auxiliary incubator dish
with cover
I. Enrichment media — lauryl tryptose broth (for pre-
enrichment technique)
m. A binocular wide-field dissecting microscope is recom-
mended for counting. The light source should be a cool
white fluorescent lamp.
3. SELECTION OF SAMPLE SIZE
Size of the sample will be governed by the expected bacte-
rial density. An ideal quantity will result in the growth of about
50 coliform colonies, but not more than 200 bacterial colonies
of all types. The table below lists suggested sample volumes
for MF total coliform testing.
Quantities Filtered (ml)
100 10 1 0.1 0.01 0.001 0.0001
Lakes	x x	x
Rivers	x	x x
Secondary Effluent	x	x x x
Untreated Wastewater	x x x
When less than 20 ml of sample is to be filtered, a small
amount of sterile dilution water should be added to the funnel
before filtration. This increase in water volume aids in uniform
dispersion of the sample over the membrane filter.
4.	PREPARATION OF PETRI DISH FOR MEMBRANE
FILTER
a.	Sterlize forceps by dipping in alcohol and passing
quickly through Bunsen burner flame.
b.	Place sterile absorbent pad into sterile petri dish.
c.	Add 1.8 to 2.0 ml M-Endo Media to absorbent pad
using a sterile pipet.
5.	PROCEDURE FOR FILTRATION OF UNCHLORINATED
SAMPLE
All filtrations and dilutions of water specimens must be accu-
rate and should be made so that no contaminants from the air,
equipment, clothes or fingers reach the specimen either di-
rectly or by way of the contaminated pipet.
a.	Secure tubing from pump and bypass to receiving flask.
Place palm of hand on flask opening and start pump.
Adjust suction to Va atmosphere with hose clamp on
pressure bypass. Turn pump switch to OFF.
b.	Set sterile filter-support-stand and funnel on receiving
flask. Loosen wrapper. Rotate funnel counterclockwise
to disengage pin. Recover with wrapper.
c.	Place petri dish on bench with lid up. Write identification
on lid with grease pencil.
d.	Unwrap sterile pad container. Light Bunsen burner.
e.	Unwrap membrane filter container.
f.	Sterilize forceps by dipping in alcohol and passing
quickly through Bunsen burner.
g.	Center membrane filter on filter stand with forceps after
lifting funnel. Membrane filter with printed grid should
show grid uppermost (Fig. I, next page).
h.	Replace funnel and lock against pin (Fig. II).
i.	Shake sample or diluted sample. Measure proper
ALIQUOT'7 with sterile pipet and add to funnel.
j. Add a small amount of the sterile dilution water to fun-
nel. This will help check for leakage and also aid in
dispersing small volumes (Fig. III).
k. Now start vacuum pump.
17 Aliquot (AL-ll-kwot). Portion of sample.

-------
Laboratory 421
(Coliform)
OUTLINE OF PROCEDURE FOR INOCULATION OF MEMBRANE FILTER
1.
Fig. I
Center membrane filter on
filter holder. Handle mem-
brane only on outer 3/i6
inch with forceps sterilized
before use in ethyl or methyl
alcohol and passed lightly
through a flame.
2.
Fig. II
Place funnel
onto filter
holder.
Fig. Ill
Fig. IV
Fig. V
5
S
4.
3. Pour or pipet sample
aliquot into funnel.
Avoid spattering. After
suction is applied rinse
four times with sterile
buffered distilled water.
Remove membrane filter from
filter holder with sterile
forceps. Place membrane
on pad. Cover with petri
top.
5.	Incubate in
inverted
position for
22 ± 2 hours.
6.	Count colonies
on membrane.

-------
422 Treatment Plants
(Coliform)
I. Rinse filter with three 20 to 30 ml portions of sterile
dilution water.
m. When membrane filter appears barely moist, switch
pump to OFF.
n. Sterilize forceps as before.
o. Remove membrane filter with forceps after first remov-
ing funnel as before (Fig. I).
p. Center membrane filter on pad containing M-Endo
Media with a rolling motion to insure water seal. Inspect
membrane to insure no captured air bubbles are pre-
sent (Fig. IV).
q. Place inverted petri dish in incubator for 22 ± 2 hours.
6. PROCEDURE FOR COUNTING MEMBRANE FILTER
COLONIES
a.	Remove petri dish from incubator.
b.	Remove lid from petri dish.
c.	Turn so that your back is to window.
d.	Tilt membrane filter in base of petri dish so that green
and yellow-green colonies are most apparent. Direct
sunlight has too much red to facilitate counting.
e.	Count individual colonies utilizing an overhead fluores-
cent light. The typical colony has a pink to dark red
color with a metallic surface sheen. The sheen area
may vary from a small pin-head size to complete
coverage of the colony surface. Only those showing
this sheen should be counted.
f.	Report total number of "coliform colonies" on work
sheet. Use the membranes that show from 20 to 80
colonies and do not have more than 200 colonies of all
types (including non-sheen or, in other words, non-
conforms).
EXAMPLE:
A total of 42 colonies grew after filtering a 10 ml sample.
Bacteria/100 ml = No. of colonies counted x 100 ml
Sample volume filtered, ml x 100 ml
_ (42 colonies) (100 ml)
(10 ml) (100 ml)
= (4.2) (100 ml)
100 ml
= 420 per 100 ml
SPECIAL NOTE:
Inexperienced persons often have great difficulty with con-
nected colonies, with mirror reflections of fluorescent tubes
(which are confused with metallic sheen), and with water con-
densate and particulate matter which are occasionally mis-
taken for colonies. Thus there is a tendency for inexperienced
persons to make errors on the high side in MF counts. Techni-
cians who have not attained proficiency in coliform colony rec-
ognition should transfer questionable colonies to lactose (or
lauryl tryptose) broth tubes for verification as coliform or-
ganisms.
7. PROCEDURE FOR FILTRATION OF CHLORINATED
SAMPLES USING ENRICHMENT TECHNIQUE
a.	Place a sterile absorbent pad in the upper half of a
sterile petri dish and pipet 1.8 to 2.0 ml sterile lauryl
tryptose broth. Carefully remove any surplus liquid.
b.	ASEPTICALLY18 place the membrane filter through
which the sample has been passed on the pad.
c.	Incubate the filter, without inverting the dish, for 1 Vi to 2
hours at 35°C in an atmosphere of 90 percent humidity
(damp paper towels added to a plastic container with a
snap-on lid can be used).
d.	The enrichment culture is then removed from the in-
cubator. A fresh sterile absorbent pad is placed in the
bottom half of the petri dish and saturated with 1.8 to
2.0 ml M-Endo Broth.
e.	The membrane filter is transferred to the new pad. The
used pad of lactose or lauryl tryptose may be dis-
carded.
f.	Invert the dish and incubate for 20 to 22 hours at 35 ±
0.5°C.
g.	Count colonies as in previous method.
H.	MEMBRANE FILTER METHOD - FECAL COUFORM
The membrane filter procedure for fecal coliform uses an
enriched lactose medium (M-FC Broth) that depends on an
incubation temperature of 44.5 ± 0.2°C for its selectivity. Since
the temperature is CRITICAL, incubation takes place in a water
bath using watertight plastic bags.
I.	MATERIALS REQUIRED
a.	M-FC media
b.	Culture dishes should be tight fitting.
c.	Membrane filters
d.	Watertight plastic bags
e.	Waterbath set at 44.5± 0.2°C. The thermometer must
be checked against an NBS thermometer to insure the
accuracy of the waterbath temperature.
f.	Sample size must be chosen to yield 20 to 60 fecal
colonies on a filter. Suggested sample volumes are
shown below:
Volume to be filtered in milliliters
100 10 1 0.1 0.01 0.0Q1
Raw Wastewater	x x x
Secondary Effluent	x x x
Receiving Streams x x x x
2.	PREPARATION OF CULTURE DISH
Place a sterile absorbent pad in each culture dish and pipet
(sterile) approximately 2 ml of M-FC medium to saturate the
pad. Carefully remove any surplus liquid.
3.	FILTRATION OF SAMPLE
Observe the procedure as prescribed for total coliform using
membrane filters.
4.	INCUBATION
Place the prepared culture dishes in waterproof plastic bags
18 Aseptic (a-SEP-tick). Free from the living germs of disease, fermentation, or putrefaction. Sterile.

-------
Laboratory 423
(Coliform)
and immerse in water bath set at 44.5 ± 0.2°C for 24 hours. All
culture dishes should be placed in the waterbath within 30
minutes after filtration.
5. COUNTING
Colonies produced by fecal coliform bacteria are blue. The
non-fecal coliform colonies are grey to cream colored. Nor-
mally, few non-fecal coliform colonies will be observed due to
the selective action of the elevated temperature and the addi-
tion of the resolic acid to the M-FC media.
Examine the cultures under a low-power magnification.
Count and calculate fecal coliform density per 100 ml.
Fecal Coliform/100 ml = Fecal colonies counted x 100 ml
Sample volume filtered, ml x 100 ml
EXAMPLE:
A total of 78 colonies grew after filtering a 10 ml sample.
Fecal Coliforms/100 ml = Fecal colonies counted x 100 ml
Sample volume filtered, ml x 100 ml
(78 colonies) (100 ml)
(10 ml) (100 ml)
= (7.8) (100)
100 ml
= 780 per 100 ml
QUESTIONS
Write your answers in a notebook and then compare your
answers with those on page 16-266.
16.5H Why should sodium thiosulfate crystals be added to
sample bottles for coliform tests before sterilization?
16.51 Steam autoclaves effect sterilization (killing of all or-
ganisms) at a relatively low temperature (	°C)
within	minutes by utilizing moist heat.
16.5J Estimate the Most Probable Number (MPN) of col-
iform group bacteria from the following test results:
Dilutions	0 -1-2-3-4 -5
Readings (+ tubes) 5 5 5 1 2 0
16.5K How is the number of conforms estimated by the
membrane filter method?
6WP OF LB660M 7 OF 9)L56SOf06
ON l
LAtoeAXOQV
Work the next portion of the discussion and review questions
before continuing with Lesson 8.
DISCUSSION AND REVIEW QUESTIONS
Chapter 16. LABORATORY PROCEDURES AND CHEMISTRY
(Lesson 7 of 9 Lessons)
Write the answers to these questions in your notebook. The
question numbering continues from Lesson 6.
33.	What is the purpose of the coliform group bacteria test?
34.	What does MPN mean?
35.	How would you determine the number of dilutions for an
MPN test?
36.	What factors can cause errors when counting colonies on
membrane filters?
37.	How can questionable colonies on membrane filters be
verified as coliform colonies?

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424 Treatment Plants
CHAPTER 16. LABORATORY PROCEDURES AND CHEMISTRY
(Lesson 8 of 9 Lessons)
7. Dissolved Oxygen (DO) and Biochemical Oxygen De-
mand (BOD)
A.	DISCUSSION
The dissolved oxygen (DO) test is, as the name implies, the
testing procedure to determine the amount of oxygen dis-
solved in samples of water or wastewater. The analysis for DO
is a key test in water pollution control activities and waste
treatment process control. There are various types of tests that
can be run to obtain the amount of dissolved oxygen. This
procedure is the Sodium Azide Modification of the Winkler
Method and is best suited for relatively clean waters. Interfer-
ing substances include color, organics, suspended solids, sul-
fide, chlorine, and ferrous and ferric iron. Nitrite will not inter-
fere with the test if fresh azide is used.
The generalized principle is that iodine will be released in
proportion to the amount of dissolved oxygen present in the
sample. By using sodium thiosulfate with starch as the indi-
cator, one can titrate the sample and determine the amount of
dissolved oxygen.
B.	WHAT IS TESTED?
Sample
Influent
Primary Clar. Effluent
Secondary Effluent
Oxidation Ponds
Activated Sludge —
Aeration Tank Outlet
(> means greater than)
(* supersaturated with oxygen)
C.	APPARATUS
METHOD A (Sodium Azide Modification of Winkler Method)
1.	Buret, graduated to 0.1 ml
2.	Three 300 ml glass-stoppered BOD bottles
3.	Wide-mouth Erlenmeyer flask, 600 ml
4.	One 10 ml measuring pipet
5.	One Miter reagent bottle to collect activated sludge
METHOD B (DO Probe)
Follow manufacturer's instructions. See Section H, DO
Probe, for Discussion, Calibration, and Precautions.
D.	REAGENTS
(Standardized solutions may be purchased from chemical
suppliers.)
1. Manganous sulfate solution. Dissolve 480 g manganous
sulfate crystals (MnS04 • 4 H20) in 400 to 600 ml distilled
water. Filter through filter paper, then add distilled water to
the filtered liquid to make a 1-liter volume.
2.	Alkaline iodide-sodium azide solution. Dissolve 500 g
sodium hydroxide (NaOH) in 500 to 600 ml distilled water;
dissolve 150 g potassium iodide (Kl) in 200 to 300 ml dis-
tilled water in a separate container. Exercise caution. Mix
chemicals in pyrex glass bottles using a magnetic stirrer.
Add the chemicals to the distilled water slowly and cau-
tiously. Avoid breathing the fumes and body contact with
the solution. Heat is produced when the water is added,
and the solution is very caustic. Place an inverted beaker
over the top of the mixing container and allow the container
to cool at room temperature.
Mix both solutions when they are cool.
Dissolve 10 g sodium azide (NaN3) in 40 ml of distilled water.
Exercise caution again. This solution is poisonous.
Add the sodium azide solution with constant stirring to the
cooled solution of alkaline iodide; then add distilled water to the
mixture to make a 1-liter volume. Sodium azide will decom-
pose in time and is no good after three months.
3.	Sulfuric Acid. Use concentrated reagent-grade acid
(H2S04). Handle carefully, since this material will burn
hands and clothes. Rinse affected parts with tap water to
prevent injury.
CAUTION: When working with alkaline azide and sulfuric
acid, keep a nearby water faucet running for
frequent hand rinsing.
4.	0.025 N Phenylarsine Oxide (PAO) solution. This solution is
available and standardized from commercial sources.
5.	0.025 N Sodium Thiosulfate solution. Dissolve exactly
6.206 grams sodium thiosulfate crystals (Na^Oj - 5 HzO)
in freshly boiled and cooled water and make up to 1 liter.
For preservation, add 0.4 g or 1 pellet of sodium hydroxide
(NaOH). Solutions of "thio" should be used within two
weeks to avoid loss of accuracy due to decomposition of
solution.
6.	Starch solution. Make a thin paste of 6 g of potato starch in
a small quantity of distilled water. Pour this paste into one
liter of boiling, distilled water, allow to boil for a few minutes,
then settle overnight. Remove the clear supernatant and
save; discard the rest. For preservation, add two drops tol-
uene (CeHsCH3) or use 1.25 grams salicylic acid.
SODIUM AZIDE MODIFICATION OF THE WINKLER
METHOD
NOTE: The sodium azide destroys nitrate which will interfere
with this test.
Common Range, mgIL
Usually 0,>1 is very good.
Usually 0, Recirculated from
filters > 2 is good.
50% to 95% Saturation, 3 to
> 8 is good.
1 to 25+'
>2 desirable

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Laboratory 425
(DO and BOD)
E. PROCEDURE
1. Take
300 ml
sample.
OUTLINE OF PROCEDURE
Add
2 ml
MnS04
below
surface.
White floe;
no DO.
4. Mix by
inverting.

3. Add
2 ml
Kl +
NaOH
below
surface.
A
(% O g\
O • 1
0 0
0 0
i» * 0
0 0
&
o o
0 o
• o •
0 o
0 0
Brown floe;
DO present.
5. Add
2 ml
H2S04.
A
Reddish-
brown
iodine
solution.
Titration of Iodine Solution:
1. Pour 203 ml
into flask.
Reddish-
Brown
2. Titrate
with PAO or
Sodium
Thiosulfate.
The reagents are to be added in the quantities, order, and
methods as follows:
1.	Collect a sample to be tested in 300 ml (BOD) bottle taking
special care to avoid aeration of the liquid being collected.
Fill bottle completely and add cap.
2.	Remove cap and add 2 ml of manganous sulfate solution
below surface of the liquid.
3.	Add 2 ml of alkaline-iodide-sodium azide solution below
the surface of the liquid.
4.	Replace the stopper, avoid trapping air bubbles, and
Pale
Yellow
I
Blue
Clear
3. Add Starch
Indicator.
End Point
shake well by inverting the bottle several times. Repeat
this shaking after the floe has settled halfway. Allow the
floe to settle halfway a second time.
5.	Acidify with 2 ml of concentrated sulfuric acid by allowing
the acid to run down the neck of the bottle above the
surface of the liquid.
6.	Restopper and shake well until the precipitate has dis-
solved. The solution will then be ready to titrate. Handle
the bottle carefully to avoid acid burns.
7.	Pour 203 ml from bottle into an Erlenmeyer flask.

-------
426 Treatment Plants
(DO and BOD)
8.	If the solution is brown in color, titrate with 0.025 N PAO
until the solution is pale yellow color. Add a small quantity
of starch indicator and proceed to Step 10. (Note: Either
PAO and 0.025 N sodium thiosulfate can be used.)
9.	If the solution has no brown color, or is only slightly col-
ored, add a small quantity of starch indicator. If no blue
color develops, there is zero Dissolved Oxygen. If a blue
color does develop, proceed to Step 10.
10.	Titrate to the first disappearance of the blue color. Record
the number of ml of PAO used.
11.	The amount of oxygen dissolved in the original solution
will be equal to the number of ml of PAO used in the
titration provided significant interfering substances are not
present.
mg1L DO = ml PAO
F.	EXAMPLE
The DO titration of a 200 ml sample requires 5.0 ml of 0.025
N PAO. Therefore, the dissolved oxygen concentration in the
sample is 5 mg/L.	*
G.	CALCULATION
You will want to find the percent saturation of DO in the
effluent of your secondary plant. The DO is 5.0 mg/L and the
temperature is 20°C. At 20°C, 100 percent DO saturation is 9.2
mg/L.
The dissolved oxygen saturation values are given in Table
16.7. Note that as the temperature of water increases, the DO
saturation value (100% Saturation Column) decreases. Table
16.7 gives 100 percent DO saturation values for temperatures
in °C and °F.
DO Saturation, %, - DO of SamP'e- m&L x 100%
DO at 100% Saturation, mg/L	-54
9.2)5.0 0
_ 5.0 mg/L x 10QO/o	4 6 0
9.2 mg/L	4 oo
= .54 x 100%	368
32
= 54%
H.	DO PROBE
I.	DISCUSSION
Measurement of the dissolved oxygen (DO) concentration
with a probe and electronic readout meter is a satisfactory
substitute for the Sodium Azide Modification of the Winkler
Method under many circumstances. The probe is recom-
mended when samples contain substances which interfere
with the Modified Winkler procedure, such as sulfite, thiosul-
fate, polythionate, mercaptans, free chlorine or hypochlorite,
organic substances readily hydrolyzed in alkaline solutions,
free iodine, intense color or turbidity, and biological floes. A
continuous record of the dissolved oxygen content of aeration
tanks and receiving waters may be obtained using a probe. In
determining the BOD of samples, a probe may be used to
determine the DO initially and after the five-day incubation
period of the blanks and sample dilutions.
2.	PROCEDURE
Follow manufacturer's instructions.
3.	CALIBRATION
To be assured that the DO probe reading provides the dis-
TABLE 16.7 EFFECT OF TEMPERATURE ON OXYGEN
SATURATION FOR A CHLORIDE
	CONCENTRATION OF ZERO mg/L


mg/L DO at
°c
T
Saturation
0
32.0
14.6
1
33.8
14.2
2
35.6
13.8
3
37.4
13.5
4
39.2
13.1
5
41.0
12.8
6
42.8
12.5
7
44.6
12.2
8
46.4
11.9
9
48.2
11.6
10
50.0
11.3
11
51.8
11.1
12
53.6
10.8
13
55.4
10.6
14
57.2
10.4
15
60.0
10.2
16
61.8
10.0
17
63.6
9.7
18
65.4
9.5
19
67.2
9.4
20
68.0
9.2
21
69.8
9.0
22
71.6
8.8
23
73.4
8.7
24
75.2
8.5
25
77.0
8.4
solved oxygen content of the sample, the probe must be calib-
rated. Take a sample that does not contain substances that
interfere with either the probe reading or the Modified Winkler
procedure. Split the sample. Measure the DO in one portion of
the sample using the Modified Winkler procedure and compare
this result with the DO probe reading on the other portion of the
sample. Adjust the probe reading to agree with the results from
the Modified Winkler procedure.
When calibrating the probe in an aeration tank of the acti-
vated sludge process, do not attempt to measure the dissolved
oxygen in the aerator and then adjust the probe. The biological
floes in the aerator will interfere with the Modified Winkler pro-
cedure, and the copper sulfate-sulfamic acid procedure is not
sufficiently accurate to calibrate the probe. An aeration tank
probe may be calibrated by splitting an effluent sample,
measuring the DO by the Modified Winkler procedure, and
comparing results with the probe readings. Always keep the
membrane in the tip of the probe from drying because the
probe can lose its accuracy until reconditioned.
4. PRECAUTIONS
a.	Periodically check the calibration of the probe.
b.	Keep the membrane in the tip of the probe from drying
out.
c.	Dissolved inorganic salts, such as found in sea water,
can influence the readings from a probe.
d.	Reactive compounds, such as reactive gases and sul-
fur compounds, can interfere with the output of a probe.
e.	Don't place the probe directly over a diffuser because
you want to measure the dissolved oxygen in the water
being treated, not the oxygen in the air supply to the
aerator.

-------
Laboratory 427
QUESTIONS
Write your answers in a notebook and then compare your
answers with those on pages 461 and 462.
16.5L Calculate the percent dissolved oxygen saturation if
the receiving water DO is 7.9 mgIL and the tempera-
ture is 10°C.
16.5M How would you calibrate the DO probe in an aeration
tank?
BIOCHEMICAL OXYGEN DEMAND OR BOD
A.	DISCUSSION
The BOD test gives the amount of oxygen used by mi-
croorganisms to utilize the substrate (food) in wastewater
when placed in a controlled temperature for five days. The DO
(dissolved oxygen) is measured at the beginning and re-
corded. During the five-day period, microorganisms in the
sample break down complex organic matter in the sample,
using up oxygen in the process. After the five-day dark incuba-
tion period, the DO is again determined. The BOD is then
calculated on the basis of the reduction of DO and the size of
sample. This test is an estimate of the availability of food in the
sample (food or organisms that take up oxygen) expressed in
terms of oxygen use. Results of a BOD test indicate the rate of
oxidation and provide an indirect estimate of the availability to
organisms or concentration of the waste.
Actual environmental conditions of temperature, organisms
population, water movement, sunlight and oxygen concentra-
tion cannot be accurately reproduced in the laboratory. Results
obtained from this test must take into account these factors
when relating BOD results to receiving water oxygen de-
mands.
Samples are incubated for a standard period of five days
because a fraction of the total BOD will be exerted during this
period. The ultimate or total BOD is normally never run for
plant control. A disadvantage of the BOD test is that the results
are not available until five days after the sample was collected.
B.	WHAT IS TESTED?
Sample
Influent
Primary Effluent
Secondary Effluent
Digester Supernatant
Industrial Wastes
Common Range, mg IL
150 - 400
60 - 160
5 - 60
1000 - 4000+
100 - 3000+
C.	APPARATUS
1.	300 ml BOD bottles with ground glass stoppers
2.	Incubator, 20°C ± 1°C
3.	Pipets, 10 ml graduated, 1/32 to 1/16-inch diameter tip
4.	Buret and stand
5.	Erlenmeyer flask, 500 ml
D.	REAGENTS
See Section D, page 424, under DO portion of this proce-
dure for the preparation of manganous sulfate, alkaline
iodide-sodium azide, sulfuric acid, sodium thiosulfate, and
starch solutions.
1. Distilled water. Water used for solutions and for preparation
of the solution water must be of highest quality. It must
(DO and BOD)
contain no copper or decomposable organic matter. Ordi-
nary distilled water for your car's battery is not good
enough.
2.	Phosphate buffer solution. Dissolve 8.5 g monobasic
potassium phosphate (KH2P04), 21.75 g dibasic potassium
phosphate (K^HPOJ, 33.4 g dibasic sodium phosphate
crystals (Na?HP04 • 7 HzO), and 1.7 g ammonium chloride
(NH4CI) in distilled water and make up to 1 liter. The pH of
this buffer should be 7.3 and should be checked with a pH
meter. Discard this reagent if there is any sign of biological
growth.
3.	Magnesium sulfate solution. Dissolve 22.5 g magnesium
sulfate crystals (MgS04 - 7 H20) in distilled water and
make up to 1 liter.
4.	Calcium chloride solution. Dissolve 27.5 g anhydrous cal-
cium chloride (CaCI2) in distilled water and make up to 1
liter.
5.	Ferric chloride solution. Dissolve 0.25 g ferric chloride
(FeCI3 - 6 H20) in distilled water and make up to 1 liter.
6.	Dilution water. Add 1 ml each of phosphate buffer (Step 2),
magnesium sulfate (Step 3), calcium chloride (Step 4), and
ferric chloride solutions (Step 5) for each liter of distilled
water. Store at a temperature as close to 20°C as possible
for at least 24 hours to allow the water to become stabilized.
This water should not show a drop in DO of more than 0.2
mgIL on incubation for five days.
Many plants do not prepare reagents. Small plants and
plants that do not run many tests find it quicker and easier to
purchase commercially prepared reagents. These reagents
may be available in the desired strength or they may consist of
dry PILLOWS19 which are added to the sample, rather than the
liquid reagent. Check with your chemical supplier for these
reagents.
E. PROCEDURE FOR UNCHLORINATED SAMPLES
The test is made by measuring the oxygen used or depleted
during a five-day period at 20°C by a measured quantity of
wastewater sample seeded into a reservoir of dilution water
saturated with oxygen. This is compared to an unseeded or
blank reservoir of dilution water by subtracting the difference
and multiplying by a factor for dilution.
PROCEDURE
1.	BOD bottles should be of 300 ml capacity with ground glass
stoppers and numbers. To clean the bottles, carefully rinse
with tap water followed by distilled water.
2.	Fill two bottles completely with dilution water and insert the
stopper tightly so that no air is trapped beneath the stopper.
Siphon dilution water from its container when filling BOD
bottles.
3.	Set up one or more dilutions of the sample to cover the
estimated range of BOD values. From the estimated BOD,
calculate the volume of raw sample to be added to the BOD
bottle based on the fact that:
The most valid DO depletion is 4 mgIL. Therefore,
ml of sample added = (4 mgIL) (300 ml)
per 300 ml	Estimated BOD, mgIL
1200
Estimated BOD, mg/L
1* Pillows. Plastic tubes shaped like pillows that contain chemicals or reagents. Cut open the pillow, pour the reagents into the sample being
tested, mix thoroughly and follow test procedures.

-------
428 Treatment Plants
(DO and BOD)
OUTLINE OF PROCEDURE
1. Fill 2 BOD bottles
with BOD dilution
water; insert
stoppers.
2. Place sample in
2 BOD bottles;
fill with dilution
water; insert
stoppers.
A
3. Test
for DO.
4. Incubate 5 days.
5. Test for DO.
6. Add
2 ml MnS04
below
surface.
7. Add 2 ml
alkaline Kl
below
surface.
3. Test
for DO.
8. Add 2 ml
H2S04.
0.025 N
Na^Oj
orPAO
9. Transfer
203 ml
to flask.
10. Titrate
with PAO
(or thiosulfate).

-------
Laboratory 429
EXAMPLES:
a. Estimated BOD
= 400 mgIL
1200
ml of sample added =
to BOD bottle	400
= 3 ml
b. Estimated BOD = 200 mgIL: use 6 ml
100 mg/L: use 12 ml
20 mg/L: use 60 ml
When the BOD is unknown, select more than one sample
size. For example, place several samples — 1 ml, 3 ml, 6 ml,
and 12 ml — into four BOD bottles.
For samples with very high BOD values, it may be difficult to
accurately measure small volumes or to get a truly representa-
tive sample. In such a case, initial dilution should first be made
on the sample. A dilution of 1:10 is convenient.
4.	To perform the BOD test, first fill two BOD bottles with BOD
dilution water (blanks). Nos. (1) and (2) in illustration, page
428.
5.	Next, for each sample to be tested, carefully measure out
the two portions of sample and place them into two new
BOD bottles, Nos. (3) and (4). Add dilution water until the
bottles are completely filled. Insert the stoppers. Avoid en-
trapping air bubbles. Be sure that there are water seals on
the stoppers.
6.	On bottles (2) and (4) immediately determine the initial dis-
solved oxygen.
7.	Incubate the remaining dilution water blank and diluted
sample in the dark at 20°C for five days. These are bottles
(1) and (3).
8.	At the end of exactly five days (± 3 hours), test bottles (1)
and (3) for their DISSOLVED OXYGEN by using the sodium
azide modification of the Winkler method or a DO probe. At
the end of five days, the oxygen content should be at least 1
mg/L. Also, a depletion of 2 mg/L or more is desirable.
Bottles (1) and (2) (blanks) are only used to check the dilu-
tion water quality. Their difference should be less than 0.2
mg/L if the quality is good and free of impurities. The differ-
ence in blank readings is not used as a blank correction, but
merely as a check on the quality of dilution water. Differ-
ences of greater than 0.2 mg/L could possibly be due to
contamination and/or dirty BOD bottles.
F. PRECAUTIONS
1.	The temperature of the incubator must be at 20°C. Other
temperatures will change the rate of oxygen used.
2.	The dilution water must be made according to STANDARD
METHODS (as outlined on page 427, Section D, 6) for the
most favorable growth rate of the bacteria. This water must
be free of copper which is often present when copper stills
are used by commercial dealers. Use all glass or stainless
steel stills or demineralized water.
3.	The wastewater must also be free of toxic wastes, such as
hexavalent chromium.
4.	If you use a cleaning solution to wash BOD bottles, be sure
to rinse the bottles several times. Cleaning agents are toxic
and If any residue remains in a BOD bottle, a BOD test
could be ruined.
5.	Unchlorinated wastewater normally contains an ample
(DO and BOD)
supply of seed bacteria; therefore seeding is usually not
necessary.
6. Since this is a bioassay (BUY-o-ass-SAY), that is, living
organisms are used for the test, environmental conditions
must be quite exact.
G. EXAMPLE
BOD Bottle Volume
Sample Volume
Initial DO of Diluted
Sample
DO of Sample and Dilution
After 5-day Incubation
= 300 ml
= 15 ml
8.0 mg/L
= 4.0 mg/L
H. CALCULATIONS
BOD,
[
Initial DO of
DO of Diluted
Sample After
J J" BOD Bottle Vol., ml
[300 ml "1
15 ml J
mg/L = I Diluted Sam- + 5-Day Incuba- I L Sample Volume, ml
pie, mg/L tion, mg/L J
]
= (8.0 mg/L - 4.0 mg/L)
(4.0) (300)
15
= 80 mg/L
For acceptable results, the percent depletion of oxygen in
the BOD test should range from 30 percent to 80 percent de-
pletion.
DO of Diluted Sample, mg/L
% Depletion = - DO After 5 Days, mg/L y 10n%
DO of Diluted Sample, mg/L
= (8.0 mg/L - 4.0 mg/L) x 100%
8.0 mg/L
= 1 x 100%
8
= 50%
I. PROCEDURE FOR CHLORINATED SAMPLES
Dechlorination of Samples
Whenever chlorinated wastewater samples are collected for
BOD analysis, sufficient dechlorinating agent must be added to
destroy the residual chlorine. The following procedure should
be followed:
1.	Using the procedure given for residual chlorine analysis on
page 406, test the sample for chlorine.
2.	If there is no residual chlorine, proceed with test procedures
below. If residual chlorine is present, add sufficient 0.025 N
sodium sulfite until residual chlorine is absent. If a chlorine
residual is present, the BOD results will be low. if too much
sodium sulfite is added, the BOD results will be high. Pre-
pare 0.025 N sodium sulfite by dissolving 1.575 grams of
anhydrous Na^Oa in 1000 ml of distilled water. This solu-
tion is not stable and must be prepared daily.
Seeding of Sample
When a sample contains very few microorganisms as a re-
sult, for example, of chlorination or extreme pH, microorgan-
isms must be added to the sample.
1. Collect about one liter of unchlorinated raw wastewater or
primary effluent about 24 hours prior to the time you wish to
start the BOD test. Let sample settle at 20°C for 24 to 36

-------
Treatment Plants
D and BOD)
OUTLINE OF BOD PROCEDURE (Chlorinated Samples)
1. Test for chlorine
& dechlorinate if
necessary.
A
M

2 '



2. Fill two bottles
with BOD dilution
water.
& R
3. Add sample being
tested to two BOD
bottles.
& R
z
U2I

4. Add seed material
to sample bottles.
& M
szzzt mm
5. Add seed material
to two BOD bottles
7. Test duplicate bottles
(1,3,5) for initial DO.
A








6. Fill sample and
seed bottles with
dilution water.
9. Test for D.O. (final)
AAA
8. Incubate at 20 C
for 5 days
0.025 N
6. Add
2 ml MnS04
below
surface.
7. Add 2 ml
Alkaline Kl
below
surface.
8. Add 2 ml
H2S04.
9. Transfer
200 ml
to flask.
10. Titrate.

-------
Laboratory 431
hours. Filter through glass wool to remove large particles
and grease clumps. Use the filtered sample for "seed."
2.	Fill two 300 ml BOD bottles with dilution water (see page
430) and insert stopper tightly so no air bubbles are trap-
ped.
3.	Set up one or more dilutions of samples In duplicate as
shown on page 430.
4.	Add 1 ml seed from Step 1 to each BOD bottle containing a
dechlorinated sample.
5.	Set up samples of seed material to determine the amount of
oxygen depletion that will be due to the added seed mate-
rial. Use 3, 6, and 9 ml of seed and determine the five-day
oxygen depletion due to 1 ml of seed. Seed material should
produce a correction of at least 0.6 mgIL per ml of seed.
Make these samples also in duplicate.
6.	Determine initial DO on one set of duplicate bottles.
7.	Incubate dilution water blank, diluted samples, and seed
sample at 20°C for five days.
8.	At the end of five days, test bottles for dissolved oxygen.
9.	Calculate five-day BOD.
EXAMPLE

Bottle 2
Bottle 4
Bottle 6
Sample
blank
effluent
seed
Sample volume
—
10 ml
0
Seed volume
—
1 ml
3 ml
Initial DO
9.2 mg/L
9.2 mg/L
9.2 mgIL
DO after 5 days
9.2 mg/L
5.1 mg/L
7.1 mg/L
Depletion
0.0 mg/L
4.1 mg/L
2.1 mg/L
CALCULATION
For seed correction:
mgIL DO depletion caused = 5 day depletion of seed sample
by 1 ml of seed	ml of seed
9.2 mgIL - 7.1 mgIL
3 ml
= 0.7 mg/L/ml
5-day BOD:
BOD mg/L =	~ DC* after 5 days)-(seed correction)] x 300
ml of sample volume
[(9.2 mg/L - 5.1 mg/L)-(0.7 mg/Lfmi) (1 ml)] x 300 ml
10 ml
(4.1 mg/L - 0.7 mg/L) 300 ml
10 ml
= 102 mg/L
J. PRECAUTIONS
1. On effluent samples where the DO is run on the sample and
the blue bounces back on the end point titration, this indi-
cates nitrite interference and can cause the BOD to be
higher than actual by as much as 10 to 15 percent of the
answer. This fact should be considered in interpreting your
results. The end point also may waver because of decom-
position of azide in an old reagent or resuspension of sam-
ple solids. To correct a wavering end point, try preparing a
new alkaline-azide solution or more of the old solution
should be used because it may be decomposing.
(DO and BOD)
mg/L and residual DO's of greater than 2 mg/L after five
days of incubation at 20°C.
3.	Samples should be WELL MIXED before dilutions are
made. A wide-tip pipet should be used for making dilutions.
The wide tip will not clog with suspended solids.
4.	Wastewaters that have been partially nitrified may produce
high BOD results. This increased oxygen demand results
from the oxidation of ammonia to nitrate. The use of chemi-
cals such as altythiourea or other commercially available
nitrification inhibitors in the dilution water will inhibit the nitri-
fiers and alleviate this problem.
K. PROCEDURE FOR INDUSTRIAL WASTE SAMPLES
Some industrial waste samples may require special seeding
because of a low microbial population or because the wastes
contain organic compounds that are not readily oxidized by
domestic wastewater seed. To obtain the necessary spe-
cialized seed material (microorganisms) adapted or acclimated
to the industrial organic compounds, collect a sample of
adapted seed from the effluent of a biological treatment pro-
cess (activated sludge aeration tank) treating the industrial
waste. When this source of adapted seed is not available,
develop the adapted seed in the laboratory by continuously
aerating a large sample of water and feeding it with small daily
portions of the particular waste, together with soil or settled
domestic wastewater, until a satisfactory microbial population
has developed.
Once a satisfactory adapted seed is available, follow the
procedures in the previous Section I, "Procedure for Chlorin-
ated Samples, Seeding of Sample." Start with Step 2, "fill two
300 ml BOD bottles with dilution water," and follow the steps
except use the industrial waste sample instead of the dechlo-
rinated sample.
L. REFERENCE
See page 543, STANDARD METHODS, 14th Edition.
QUESTIONS
Write your answers in a notebook and then compare your
answers with those on page 462.
16.5N How would you determine the amount of organic ma-
terial in wastewater?
16.50 How would you prepare dilutions to measure the BOD
of cannery waste having an expected BOD of 2,000
mg/L?
16.5P What is the BOD of a sample of wastewater if a 2 ml
sample in a 300 ml BOD bottle had an initial DO of 7.5
mg/L and a final DO of 3.9 mg/L?
16.5Q Why should samples for the BOD test be collected
before chlorination?
16.5R Why should opened bottles of "Thio" be used or re-
standardized within two weeks?
ewp OF LB660M 80FQ
ON	* 0
LAtoeAfOQV PQOCePUtt&oiteCMmVfM
2. A minimum of two dilutions per sample should be used. Use
only analyses with oxygen depletions of greater than 2
Work the next portion of the discussion and review questions
before continuing with Lesson 9.

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432 Treatment Plants
DISCUSSION AND REVIEW QUESTIONS
Chapter 16. LABORATORY PROCEDURES AND CHEMISTRY
(Lesson 8 of 9 Lessons)
Write the answers to these questions in your notebook. The
problem numbering continues from Lesson 7.
38.	What is the formula for calculating the percent saturation
of DO?
39.	What precautions should be exercised when using a DO
probe?
40.	What is a blank, as referred to in laboratory procedures?
41. What is a limitation of the BOD test?
42. What precautions should be taken when running a BOD
test?
43. Calculate the BOD of a 5 ml sample if the initial DO of the
diluted sample was 7.5 mg/L and the DO of diluted sample
after five-day incubation was 3.0 mg/L.
CHAPTER 16. LABORATORY PROCEDURES AND CHEMISTRY
(Lesson 9 of 9 Lessons)
8. Hydrogen Ion (pH)
A. DISCUSSION
The intensity of the alkaline or acid strength of water is ex-
pressed by its pH.
Mathematically, pH is the logarithm of the reciprocal of the
hydrogen ion concentration, or the negative logarithm of the
hydrogen ion concentration.
pH = log _L = -log (H+)
(H+)
FOR EXAMPLE
If a wastewater has a pH of 1, then the hydrogen ion concen-
tration (H+) = 10~1 = 0.1.
If pH = 7, then (H+) = 10-7 = 0.0000001.
, pH Scale
0 increasing acidity — 7 — increasing alkalinity	14
/X 8
Neutral
10-» 11 — 12—13
6 through 8
In a solution, both hydrogen ions (H+) and the hydroxyl ions
(OH-) are always present. At a pH of 7, the concentration of
both hydrogen and hydroxyl ions equals 10-7 moles per liter.
When the pH is less than 7, the concentration of hydrogen ions
is greater than the hydroxyl ions. The hydroxyl ion concentra-
tion is greater than the hydrogen ions in solutions with a pH
greater than 7.
The pH test indicates whether a treatment process may con-
tinue to function properly at the pH measured. Each process in
the plant has its own favorable range of pH which must be
checked routinely. Generally a pH value from 6 to 8 is accept-
able for best organism activity. Most wastewater contains
many dissolved solids and buffers which tend to minimize pH
changes.
B WHAT IS TESTED?
Wastewater	Common Range
Influent or Raw Wastewater (domestic)	6.8 to 8.0
Raw Sludge (domestic)	5.6 to 7.0
Digester Recirculated Sludge or Supernatant 6.8 to 7.2
Plant Effluent Depending on Type
of Treatment	6.8 to 8.0
C.	MINIMUM APPARATUS UST
1.	pH meter
2.	Glass electrode
3.	Reference electrode
4.	Magnetic stirrer (optional)
D.	REAGENTS
1.	Buffer tablets of various pH values
2.	Distilled water
E.	PROCEDURE
1.	Due to the difference between the various makes and mod-
els of pH meters commercially available, specific instruc-
tions cannot be provided for the correct operation of all
instruments. In each case, follow the manufacturer's in-
structions for preparing the electrodes and operating the
instrument.
2.	Standardize the instrument against a buffer solution with a
pH approaching that of the sample.
3.	Rinse electrodes thoroughly with distilled water after re-
moval from buffer solution.
4.	Place electrodes in sample and measure pH.
5.	Remove electrodes from sample, rinse thoroughly with dis-
tilled water.

-------
Laboratory 433
6.	Immerse electrode ends in beaker of pH 7 buffer solution.
7.	Shut off meter.
F. PRECAUTIONS
1.	To avoid faulty instrument calibration, prepare fresh buffer
solutions as needed, once per week, from commercially
available buffer tablets.
2.	pH meter, buffer solution, and samples should all be at the
same temperature (constant) because temperature varia-
tions will give erroneous results.
3.	Watch for erratic results arising from electrodes, faulty con-
nections, or fouling of electrodes with oily or precipitated
matter.
QUESTION
Write your answer in a notebook and then compare your
answer with the one on page 462.
14.5S What precautions should be exercised when using a
pH meter?
9. Metals
A. DISCUSSION
The presence of metals in wastewater can be a matter of
serious concern because of the toxic properties of these mate-
rials which may adversely affect wastewater treatment sys-
tems.
Metals in wastewater may be determined in most cases by
atomic absorption spectroscopy or colorimetric methods. The
term "metals" would include the following elements:
Aluminum
Cobalt
Potassium
Antimony
Copper
Selenium
Arsenic
Iron
Silver
Barium
Lead
Sodium
Berryllium
Magnesium
Thallium
Cadmium
Mercury
Tin
Calcium
Molybdenum
Titanium
Chromium
Nickel
Vanadium

Manganese
Zinc
B. REFERENCES
For materials and procedures see:
1.	Page 148, STANDARD METHODS, 14th Edition.
2.	Page 78, MANUAL OF METHODS FOR CHEMICAL
ANALYSIS OF WATER AND WASTES, Center for En-
vironmental Research Information, U.S. Environmental
Protection Agency, 26 West St. Clair Street, Cincinnati,
Ohio 45268.
(Nitrogen-Ammonia)
QUESTION
Write your answer in a notebook and then compare your
answer with the one on page 462.
16.5T Why would an operator test for metals in wastewater?
10. Nitrogen
A.	DISCUSSION
The compounds of nitrogen are of interest to the wastewater
treatment plant operator because of the importance of nitrogen
in the life processes of all plants and animals. The chemistry of
nitrogen is complex because of the several forms that nitrogen
can assume. Ammonia, organic, nitrate, and nitrite are the
most important nitrogen forms in wastewater treatment. The
term Kjeldahl (KELL-doll) nitrogen refers to organic plus am-
monia nitrogen.
Ammonia nitrogen in domestic wastewater is generally be-
tween 10 and 40 mgIL. Primary treatment may increase the
ammonia nitrogen content slightly due to the decomposition of
some protein compounds during treatment. In secondary
treatment processes, ammonia may be oxidized to nitrite then
to nitrate in varying degrees depending on factors such as
wastewater temperature, residence time of the mi-
croorganisms, and amounts of oxygen. Significant water qual-
ity problems relating to ammonia are high chlorine demands,
fish toxicity, and high oxygen demand on receiving waters.
Nitrite (N02~~) is an intermediate oxidation state of nitrogen
between ammonia and nitrate nitrogen. Nitrite is very unstable
but can be used to monitor how well nitrification is progressing
in the treatment process. Effluents containing nitrite require a
dose of 5 mgIL of chlorine for every mgIL of nitrite to satisfy the
nitrite chlorine requirement.
Nitrate (N03~) is seldom found in raw wastewater or primary
effluent. In the biological treatment process, the ammonia ni-
trogen can be oxidized by bacteria to nitrite and then to nitrate.
Secondary effluent may contain from 0 to 50 mgIL nitrate de-
pending on the total nitrogen content in the raw wastewater.
B.	WHAT IS TESTED?
Sample Form of Nitrogen, as N
Secondary	ammonia
Effluent	Kjeldahl
nitrate
nitrite
I . Procedure for Ammonia
A.	APPARATUS
1.	Balance, analytical
2.	Balance, triple beam
3.	pH meter
4.	Kjeldahl flasks, 800 ml
5.	An all glass distilling apparatus
6.	Erlenmeyer flasks, 500 ml (these flasks should be marked
at the 350 and 500 ml volumes)
7.	Pipet, volumetric, 10 ml
8.	Beakers, 500 ml
9.	Graduated cylinder, 500 ml and 100 ml
10.	Buret, 25 ml
11.	Glass beads
B.	REAGENTS
1. Distilled water free of ammonia. All solutions must be
made with ammonia-free water. An ion exchange system
Common Range, mg/L
5 to 20
5 to 30
0 to 50
Oto 1

-------
434 Treatment Plants
(Nitrogen-Ammonia)
in conjunction with a suitable water still to insure high qual-
ity water is the best system. An anion-cation exchange
resin should be used.
2.	Ammonium chloride, stock solution. 1.0 ml = 1.0 mg
NH3-N. Dissolve 3.819 g NH4CI in distilled water and bring
to volume in a one liter volumetric flask.
3.	Ammonium chloride, standard solution. 1.0 ml = 0.01 mg.
Dilute 10.0 ml stock solution of ammonium chloride (rea-
gent 2) to volume in a one liter volumetric flask.
4.	Borate buffer. Add 88 ml of 0.1 N NaOH solution to 500 ml
of 0.025 M sodium tetraborate solution (5 g anhydrous
NajB407 or 9.5 g Na^Oy • 10 HzO per liter) and dilute to
one liter.
5.	Boric acid solution 20 glL. Dissolve 20 g H3B03 in distilled
water and dilute to one liter.
6.	0.2% methyl red solution. Dissolve 0.2 g methyl red in 100
ml of 95% ethyl alcohol (ethanol).
7.	0.2% methylene blue solution. Dissolve 0.2 g methylene
blue in 100 ml of 95% ethyl alcohol.
8.	Mixed indicator solution. Mix 2 volumes of 0.2% methyl
red solution with one volume of 0.2% methylene blue solu-
tion. This solution should be prepared fresh every 30 days.
9.	Sulfuric Acid, standard solution 0.02 N. 1 ml = 0.28 mg
NH3-N.
10.	Sodium hydroxide, 1 N. Dissolve 40 g NaOH in ammonia-
free water and dilute to one liter.
11.	Sodium hydroxide, 0.1 N. Dilute 10.0 ml 1 N sodium hy-
droxide solution to 100 ml in 100 ml volumetric flask.
12.	Dechlorinating reagent, sodium thiosulfate, 1/70 N. Dis-
solve 3.5 g Na2S203 - 5 H20 in distilled water and dilute to
one liter. One ml of this solution will remove 1 mgIL of
residual chlorine in 500 ml sample.
C. PROCEDURE
1.	Preparation of equipment. Add 500 ml of distilled water to
an 800 ml Kjeldahl flask and some glass beads and steam
out the distillation apparatus until 250 mis have been dis-
tilled. The distillate should be checked to insure that it is
ammonia-free. The Nessler reagent is used for this pur-
pose. Add 1 ml of Nessler reagent to determine if the
distillation apparatus is not contaminated with ammonia. If
the distillate turns yellow, there is ammonia present. More
water should then be distilled and the test with Nessler
reagent repeated.
2.	Sample preparation. Remove any residual chlorine by
adding dechlorinating agent equivalent to the chlorine re-
sidual (see page 429). To 400 ml of sample add 1N NaOH
solution until the pH is 9.5, checking the pH during addi-
tion with a pH meter or by use of a short range pH indi-
cator paper.
3.	Transfer 280 ml of the sample, the pH of which has been
adjusted to 9.5, to an 800 ml Kjeldahl flask, add some
glass beads, and then add 25 ml of the borate buffer.
Distill 300 ml at the rate of 6 to 10 ml per minute into 50 ml
of 2 percent boric acid contained in a 500 ml Erlenmeyer
flask.
The condenser tip or an extension of the condenser tip
must extend below the level of the boric acid solution.
Dilute the distillate to 500 ml with distilled water.
4.	Add three drops of the mixed indicator solution to the distil-
late and titrate the ammonia with the 0.02 N H2S04,
matching the end point against a blank containing the
sample volume of distilled water and H3B03 solution. The
color change during titration is from green to a purple end
point. Record volume 0.02 N H2S04 required.
5.	Calculate ammonia concentration.
D.	EXAMPLE
Results from test for ammonia in a wastewater plant effluent
were as follows:
ml of sample used	= 280
ml of 0.02 N H2S04 used	= 16.0
E.	CALCULATION
mgIL NH3-N = A x 280
S
where:
A = ml 0.02 N HjS04 used
S = sample volume distilled
From example above:
ml of 0.02 N H2S04 used, A = 16.0
ml of sample volume distilled, S = 280
mgIL NH3-N = A * 280
= 16.0 x 280
280
= 16.0 x 1
= 16.0 mgIL
F.	NOTES
1.	All standards do not have to be distilled in the same man-
ner. However, at least two standards (a high and a low)
should be distilled and titrated. If these standards do not
agree with known values, the operator should find the
cause of the apparent error.
2.	This procedure is good only for samples that contain
greater than 1.0 mgIL NH3-N.
G.	REFERENCE
See page 350.2-1 EPA's METHODS FOR CHEMICAL
ANALYSIS OF WATER AND WASTES, March 1979.

-------
1. Add 500 ml distilled
water to Kjeldahl flask
and distill 250 ml to
purge equipment.
4. Transfer 280 ml (or other
aliquot) to 800 ml Kjeldahl
flask.
O
V
7. Add 3 drops mixed
indicator.
Laboratory 435
(Nitrogen-Ammonia)
OUTLINE OF PROCEDURE
Ml
© O
/
2. Collect 400 ml of sample
and remove any trace of
residual chlorine.
3. Adjust pH to 9.5
with 1 N NaOH.
5. Add 25 ml borate
buffer.
6. Distill 300 ml into
50 ml Erlenmeyer
containing 50 ml
2% boric acid.
8. Titrate with 0.02 N HgS04.
Record amount of actd
required.
9. Calculate ammonia
concentration.

-------
436 Treatment Plants
(Nitrogen - TKN)
II. Procedures for Total Kjeldahl Nitrogen (TKN)
A.	APPARATUS
1.	Digestion apparatus. A Kjeldahl digestion apparatus with
800 ml flasks and suction takeoff to remove S03 fumes and
water.
2.	Apparatus required for ammonia determination.
B.	REAGENTS
1.	Mercuric sulfate solution. Dissolve 8 g red mercuric oxide
(HgO) in 50 ml of 1:4 sulfuric acid (10 ml concentrated
H2S04 into 40 ml distilled water - BE CAREFUL!) and dilute
to 100 ml with distilled water.
2.	Sulfuric acid - mercuric sulfate - potassium sulfate solution.
Dissolve 267 g K,S04 in 1300 ml distilled water and 400 ml
concentrated HzS04. Add 50 ml mercuric sulfate solution
and dilute to one liter.
3.	Sodium hydroxide - sodium thiosulfate solution. Dissolve
500 g NaOH and 25 g Na2S203 *5 H20 in distilled water
and dilute to one liter.
4.	All reagents required for ammonia determination except bo-
rate buffer and sodium hydroxide solutions.
C.	PROCEDURE
1.	Measure a sample into an 800 ml Kjeldahl flask. The sam-
ple size can be determined from the following table:
Kjeldahl Nitrogen	Sample Size,
in Sample, mgIL	ml
0-5	500
5- 10	250
10-20	100
20 - 50	50
50 - 500	25
Dilute the sample, if required, to 500 ml with distilled water.
Also prepare a distilled water blank by adding 500 ml distilled
water to an 800 ml Kjeldahl flask.
2.	Add 100 ml sulfuric acid - mercuric sulfate - potassium
sulfate solution to both flasks.
3.	Add several glass beads to prevent bumping in the flasks.
4.	Place the flasks on digeston apparatus and evaporate the
mixtures until sulfur trioxide (S03) fumes are given off.
S03 fumes will be indicated when white smoke begins
rising from the solution. Sulfur trioxide is toxic; therefore
observe extreme caution. Continue heating for 30 addi-
tional minutes.
5.	Cool the residues and then add 300 mis of distilled water
to each flask.
6.	Prepare distillation apparatus as described under am-
monia procedure.
7.	Add 50 ml of 2 percent boric acid to each 500 ml Erlen-
meyer receiving flask. Position the Erlenmeyer flasks
under distillation apparatus so that the tip of the condenser
or an extension is below the level of the boric acid solution
in receiving flask.
8.	Tilt each digested Kjeldahl flask and carefully add 100 ml
of sodium hydroxide - thiosulfate solution to form an al-
kaline layer at the bottom of the flask.
Do not agitate flask until it is connected to distillation ap-
paratus since free ammonia may be liberated too soon.
9. Connect the Kjeldahl flasks to the condenser and mix con-
tents of each flask.
10.	Distill 300 ml from each flask at the rate of 6 to 10 ml per
minute, into 50 ml of 2 percent boric acid.
11.	Dilute the distillate to 500 ml in the flasks.
12.	Add three drops of mixed indicator to the blank sample
and titrate with 0.02 N H2S04. The color change is from
green to a purple end point. Record volume used.
13.	Add three drops of the mixed indicator and titrate the sam-
ple flask with 0.02 N H2S04 to an end point that matches
against the blank. Record volume of 0.02 N H2S04 used.
14.	Calculate Total Kjeldahl Nitrogen (TKN) concentration.
D.	EXAMPLE
Results from a test for TKN on a wastewater treatment plant
effluent.
ml ot sample used	= 50 ml
ml 0.02 N H2S04 used to titrate sample = 4.2 ml
ml of 0.02 N H2S04 used to titrate blank = 0.3 ml
E.	CALCULATION
mgIL TKN = (A-B) x 280
S
Where:
A = ml 0.02 N H2S04 used to titrate sample
B = ml 0.02 N H2S04 used to titrate blank
S = ml of sample digested
From example above:
ml 0.02 N H2S04 used to titrate sample	= 4.2 ml
ml 0.02 N H2S04 used to titrate blank	= 0.3 ml
ml of sample digested	= 50 ml
mgIL TKN = (A"B) x 280
S
= (4.2-0.3) x 280
50
= (3.9) x 280
50
= 1092
50
= 21.8 mgIL
F.	NOTES
1.	In this procedure high and low standards as prepared under
the ammonia procedure should be digested, distilled, and
titrated as a check on the accuracy of the operator's tech-
nique.
2.	This procedure is good only for samples that contain
greater than 1.0 mg/L TKN.
G.	REFERENCE
See page 351.3-1 EPA's METHODS FOR CHEMICAL
ANALYSIS OF WATER AND WASTES, March 1979.

-------
Laboratory 437
(Nitrogen-TKN)
OUTLINE OF PROCEDURE
1. Measure sample into
Kjeldahl flask.
2. Add 100 ml sulfuric acid
mixture.
Kjeldahl
flask
Sodium hydroxide-
sodium thiosulfate
solution
4.
Cool flask. Add
300 ml distilled
water.
Alkaline layer
5. Add 100 ml
NaOH solution.
3. Digest.
Kjeldahl
spray trap
800 ml
Kjeldahl
flask
Condenser
500 ml
[tt| Erlenmeyer
J I receiving
Atesk
6. Connect flask to distillation
apparatus, mix and distill
300 ml into boric acid from
receiving flask.
7. Dilute distillate
to 500 ml. Add 3
drops mixed indi-
cator.
8. Titrate with
0.02 N H2S04.
Calculate TKN.

-------
438 Treatment Plants
(Nitrogen-Organic N)
III.	Procedure for Organic Nitrogen Calculation
A.	APPARATUS
Apparatus as listed for ammonia and TKN procedures.
B.	REAGENTS
Reagents as listed for ammonia and TKN procedures.
C.	PROCEDURE
1.	Determine ammonia concentration in sample.
2.	Determine TKN concentration in sample.
D.	EXAMPLE
A wastewater plant effluent contains an ammonia concentra-
tion of 16 mgIL and a TKN concentration of 22 mgIL.
E.	CALCULATION
Organic Nitrogen, mg IL = TKN, mg IL - Ammonia, mgIL
Using the example:
Organic Nitrogen, mg IL = TKN, mg/Z. «- Ammonia, mgIL
= 22 mg/Z. - 16 mg IL
= 6 mg/L
IV.	Procedure for Nitrite
A.	APPARATUS
1.	Spectrophotometer equipped with 1 cm or larger cells for
use at 540 nm wave length.
2.	Flasks, volumetric, 50 ml
3.	pH meter
4.	0.45 micron pore size filter and holder assembly
5.	Graduated cylinder, 50 ml
6.	Pipets, measuring, 10 ml
7.	Flask, filter
8.	Flasks, Erlenmeyer, 125 ml
B.	REAGENTS
1.	Distilled water free of nitrite and nitrate.
2.	Buffer-color reagent. To 250 ml of distilled water, add 105
ml concentrated hydrochloric acid, 5.0 g sulfanilamide and
0.5 g N- (1-naphthyl) ethylenediamine dihydrochloride. Stir
until dissolved. Add 136 g of sodium acetate (CH3COONa •
3 H20) and again stir until dissolved. Dilute to 500 ml with
distilled water. This solution is stable for several weeks if
stored in the dark.
3.	Nitrite stock solution. 1.0 ml = 0.1 mg NOz-N. Dissolve
0.4926 g dried anhydrous sodium nitrite (24 hours in desic-
cator) in distilled water and dilute to 1000 ml. Preserve with
2 ml chloroform per liter.
4.	Nitrite standard solution. 1.0 ml = 0.001 mg NOz-N. Dilute
10.0 ml ol the nitrite stock solution (reagent 3) to 1000 ml.
C.	PROCEDURE
1.	Check pH and alkalinity of sample. If pH is greater than 10
or alkalinity is in excess of 600 mgIL, adjust pH to approxi-
mately 6 with 1:3 HCI.
2.	If necessary remove turbidity by filtering 75 ml of sample
through a 0.45 micron pore size filter using the first portion
of filtrate to rinse the filter flask.
3.	Place 50 ml of sample, or an aliquot diluted to 50 ml in a 125
ml Erlenmeyer flask. Hold until preparation of standards is
complete.
4.	Add 2 ml of buffer-color reagent to each standard and sam-
ple. Mix and allow color to develop for at least 15 minutes.
5.	Read the color intensity in the spectrophotometer at 540 nm
wave length against the blank.
6.	Determine amount of nitrite-nitrogen from a standard calib-
ration graph.
D.	CONSTRUCTION OF STANDARD CALIBRATION
GRAPH
1.	Using the nitrite standard solution, prepare the following
series of nitrite standards in 50 ml volumetric llasks:
ml of Standard Solution Concentration diluted to
1.0 ml = 0.001 mg N02-N 50 ml In mg IL N02 -N
0.0	0. (Blank)
1.0	0.02
2.0	0.04
4.0	0.08
5.0	0.10
2.	Transfer this series of standards diluted to 50 ml to 125 ml
Erlenmeyer flasks.
3.	Determine the amount of nitrite-nitrogen as outlined above.
4.	Plot on a sheet of graph paper absorbance versus concen-
tration.
E.	EXAMPLE
A sample of a wastewater plant effluent and a series of nitrite
standards were analyzed with the following results:
50 ml of sample and standards
Sample	Absorbance
plant effluent	0.052
Blank	0.00
0.02 mgIL N02-N standard	0.040
0.04 mgIL N02-N standard	0.081
0.08 mg/Z. N02-N standard	0.165
0.10 mg/Z. N02-N standard	0.205
F.	CALCULATION
1.	Plot curve of concentration N02-N standards versus absor-
bance on graph paper. For example, from the above data
the following graph can be constructed.
2.	See graph on page 440.
3.	Correct (if necessary) for samples of less than 50 ml by
using the following formula:
N0 -n = nig/Z. from graph x 50 ml
ml sample used
G.	NOTE
Samples should be analyzed as soon as possible following
collection although they may be stored for 24 to 48 hours at
40°C.
H.	REFERENCE
See page 354.1-1 of EPA's METHODS FOR CHEMICAL
ANALYSIS OF WATER AND WASTES, March 1979.
20 nm. Nanometers or 0.000 000 001 meters.

-------
Laboratory 439
(Nitrogen-Nitrite)
OUTLINE OF PROCEDURE
1. Check pH and
alkalinity of
sample.
2. Remove turbidity
if necessary.
3. Place 50 ml in
flask.
4. Add 2 ml buffer-color
reagent. Mix. Allow
to stand 15 minutes.
5. Measure color intensity at
540 nm with spectrophotometer.
6. Determine nitrite concentration in unknown
sample by comparison to absorbance values of
known N02-N concentrations by use of standard
curve.

-------
440 Treatment Plants
(Nitrogen-Nitrite)
0.200
0.150
(0
¦e
i
0.100
0.050








































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_L /























































































































































































































































































































.01 .02 .03 .04 .05 .06 .07 .08 .09 .10
mg/L Nitrite as N
2. Read concentration of N02-N in plant effluent directly from graph.
.200
.150
.100
.050
01 .02 .03 .04 .05 .06 .07 .08 .09 .10
mg/L Nitrite as N

-------
Laboratory 441
V. Procedure for Nitrate — Nitrite Nitrogen
This procedure measures the amount of both nitrate and
nitrite nitrogen present in a sample by reducing all nitrate to
nitrite through the use of a copper-cadmium column. The nitrite
(that is originally present plus the reduced nitrate) is then mea-
sured colorimetrically.
A. APPARATUS
1.	Reduction column. The column in Figure 16.15 was con-
structed from a 100 ml volumetric pipet by removing the
top portion. This column may also be constructed from two
pieces of tubing joined end to end. A10 mm length of 3 cm
I.D. tubing is joined to a 25 cm length of 3.5 mm I.D.
tubing. A column may be purchased from HACH Chemical
Company. Order by Code No. 14563-00, $34.00, Post Of-
fice Box 389, Loveland, Colorado 80537.
2.	Spectrophotometer for use at 540 nm, providing a light
path of 1 cm or longer.
3.	Beakers, 125 ml.
4.	Glass wool.
5.	Glass fiber filter or 0.45 micron membrane filter.
6.	Filter holder assembly.
7.	Filter flask.
8.	pH meter.
9.	Separatory funnel, 250 ml.
10.	Pipets, volumetric 1, 2, 5, and 10 ml.
B. REAGENTS
1.	Granulated cadmium. 40 to 60 mesh (available from: EM
Laboratories, Inc., 500 Executive Boulevard, Elmsford,
New York 10523, Catalog No. 2001 Cadmium, Coarse
Powder).
2.	Copper-Cadmium. The cadmium granules (new or used)
are cleaned with 6 N HCI and copperized with 2 percent
solution of copper sulfate in the following manner:
a.	Wash the cadmium with 6 N HCI and rinse with dis-
tilled water. The color of the cadmium should be silver.
b.	Swirl 25 g cadmium in 100 ml portions of a 2 percent
solution of copper sulfate for 5 minutes or until the
blue color partially fades, decant and repeat with fresh
copper until a brown precipitate forms.
c.	Wash the copper-cadmium with distilled water at least
10 times to remove all the precipitated copper. The
color of the cadmium should now be black.
3. Preparation of reaction column. Insert a glass wool plug
into the bottom of the reduction column and fill with dis-
tilled water. Add sufficient copper-cadmium granules to
produce a column 18.5 cm in length. Maintain a level of
distilled water above the copper-cadmium granules to
eliminate entrapment of air. Wash the column with 200 ml
of dilute ammonium chloride — EDTA solution (reagent 5).
The column is then activated by passing through the col-
umn 100 ml of a solution composed of 25 ml of a 1.0 mgIL
N02-N standard and 75 ml of concentrated ammonium
chloride — EDTA solution. Use a flow rate of 7 to 10 ml per
minute. Collect the reduced standard until the level of solu-
tion is 0.5 cm above the top of the granules. Close the
screw clamp to stop flow. Discard the reduced standard.
(Nitrogen-Nitrate & Nitrite)
4.	Measure about 40 ml of concentrated ammonium chloride
— EDTA and pass through column at 7 to 10 ml per min-
ute to wash nitrate standard off column. Always leave at
least 0.5 cm of liquid above top of granules. The column is
now ready for use.
5.	Dilute ammonium chloride — EDTA solution. Dilute 300 ml
of concentrated ammonium chloride — EDTA solution
(reagent 4) to 500 ml with distilled water.
6.	Color reagent. Dissolve 10 g sulfanilamide and 1 g N (1-
naphthyl)-ethylenediamine dihydrochloride in a mixture of
100 ml concentrated phosphoric acid and 800 ml of dis-
tilled water and dilute to 1 liter with distilled water.
7.	Zinc sulfate solution. Dissolve 100 g ZnS04 ¦ 7 H20 in
distilled water and dilute to 1 liter.
8.	Sodium hydroxide, 6 N. Dissolve 240 g NaOH in 500 ml
distilled water, cool and dilute to 1 liter.
9.	Ammonium hydroxide, concentrated.
10.	Hydrochloric acid, 6 N. Dilute 50 ml concentrated HCI to
100 ml with distilled water.
11.	Copper sulfate solution, 2 percent. Dissolve 20 g of
CuS04 - 5 HjO in 500 ml of distilled water and dilute to 1
liter.
12.	Nitrate stock solution. 1.0 ml = 1.00 mg N03-N. Dissolve
7.218 g KNOs in distilled water and dilute to 1000 ml.
Preserve with 2 ml of chloroform per liter. This solution is
stable for at least six months.
13.	Nitrate standard solution. 1.0 ml = 0.01 mg N03-N. Dilute
10.0 ml of nitrate stock solution (reagent 12) to 1000 ml
with distilled water.
14.	Chloroform.
C. PROCEDURE
Removal of Interferences (if necessary).
1.	Turbidity removal. Use one of the following methods to re-
move suspended matter that can clog the reduction col-
umn.
a.	Filter sample through a glass fiber or a 0.45 micron
pore size filter.
b.	Add 1 ml zinc solution (reagent 7) to 100 ml of sample
and mix thoroughly. Add enough (usually 8 to 10 drops)
sodium hydroxide solution (reagent 8) to obtain a pH of
10.5. Let treated sample stand a few minutes to allow
the heavy flocculent precipitate to settle. Clarify by filter-
ing through a glass fiber filter or a 0.45 micron mem-
brane filter.
2.	Oil and grease removal.
a.	Adjust pH of 100 ml of filtered sample (step 1) to a pH of
2 by dropwise addition of concentrated HCI.
b.	Place sample in 250 ml separatory funnel.
c.	Add 25 ml chloroform.
d.	Stopper and shake separatory funnel gently to extract
the oils and grease into the chloroform. Carefully re-
lease the pressure after shaking so that no sample is
lost. This can be accomplished by inverting the
separatory funnel and slowly opening the stopcock
away from your face and other people.
e.	Unstopper and allow the separatory funnel to stand
until all of the chloroform settles to the bottom.

-------
442 Treatment Plants
(Nitrogen-Nitrate & Nitrite)
T
10 CM
80-85 mi
4^3 CM I iD .
3.5 MM I.D,
18,5 cm

100 MI
VOLUMETRIC
PIPET
GLASS WOOL PLUG
CLAMP
TYGON TUBING
- Cut
\)
Figure 16.15 Reduction column

-------
Laboratory 443
Open the stopcock and allow the bottom chloroform
layer to pass into a beaker and discard.
Repeat steps c,
chloroform.
d, e, and f with 25 ml of fresh
Reduction of Nitrate to Nitrite.
1.	Using a pH meter adjust the pH of sample (or standard) to
between 5 and 9 either with concentrated HCI or concen-
trated NH4OH.
2.	To 25 ml of sample (or standard) or aliquot diluted to 25 ml,
add 75 ml of concentrated ammonium chloride — EDTA
solution and mix.
3.	Pour sample into column and collect reduced sample at a
rate of 7 to 10 ml per minute.
4.	Discard the first 25 ml. Collect the rest of the sample (ap-
proximately 70 ml) in the original sample flask. Reduced
samples should not be allowed to stand longer than 15
minutes before addition of color reagent.
5.	Add 2.0 ml of color reagent to 50 ml of sample. Allow 10
minutes for color development. Within two hours measure
the absorbance at 540 nm against a reagent blank (50 ml
distilled water to which 2.0 ml color reagent has been add-
ed). (Go to top of right column.)
(Nitrogen-Nitrate & Nitrite)
Construction of Standard Calibration Graph
1. Prepare working standards by pipeting the following vol-
umes of nitrate standard solution into each of five 100 ml
volumetric flasks.
Add this volume of Nitrate
Standard Solution to 100 ml flask
0.0
1.0
2.0
5.0
10.0
Concentration of
NOj-N In mgIL
0.00
0.10
0.20
0.50
1.00
Dilute each to 100 ml with distilled water and mix.
2.	Determine the amount of nitrate-nitrite nitrogen as outlined
above in the procedure for reduction of nitrate to nitrite.
3.	Plot on a sheet of graph paper the absorbance versus con-
centration.
D. EXAMPLE
Results from the analyses of samples and working stan-
dards for nitrate-nitrite were as follows:
Flask No.
1
2
3
4
5
6
Plant Effluent
Blank (distilled water)
0.10 mgIL NOa-N
0.20 mgIL N03-N
0.50 mgIL NO,-N
1.00 mgIL N03-N
Volume
Absorbance
25 ml
0.440
25 ml
0.00
25 ml
0.075
25 ml
0.142
25 ml
0.355
25 ml
0.700
E. CALCULATION
1. Using graph paper, plot the absorbance values of working standards versus their known concentra-
tions. For example, from the above data the following graph can be constructed:
0.800
0.700
0.600
8 0.500
0.400
0.300
0.200
0.100'
















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.10 .20 .30 .40 .50 .60 .70 .80 .90
mgIL Nitrate & Nitrite-Nitrogen
1.0

-------
444 Treatment Plants
(Nitrogen-Nitrate & Nitrite)
2. Read concentration of N03~ + NO" nitrogen in plant effluent directly from graph.
0.800
0.700
-+•
0.600
g 0.500
c

-------
Laboratory 445
F.	NOTES
1.	If concentration of nitrate in the sample is greater than 1
mgIL, then the sample must be diluted.
2.	Cadmium metal is highly toxic thus caution must be exer-
cised in its use. Rubber gloves should be used whenever it
is handled.
G.	REFERENCE
See page 353.3-1 EPA's METHODS FOR CHEMICAL
ANALYSIS OF WATER AND WASTES, March 1979.
QUESTION
Write your answer in a notebook and then compare your
answer with the one on page 462.
16.5U Kjeldahl nitrogen refers to	
11. Oil and Grease
A.	DISCUSSION
This procedure measures gasoline, heavy fuel, lubricating
oil, asphalt, soaps, fats, waxes, and any other material that is
extracted by the solvent (freon) used in the test. The determi-
nation of oil and grease in a wastewater plant is helpful in
determining plant efficiencies and for diagnosis of in-plant
problems such as difficulties digesting or dewatering sludges.
B.	WHAT IS TESTED?
Sample	Common Range, mg/i.
Influent and Effluent	<5 to 50
C.	APPARATUS REQUIRED
Filter paper, Whatman No. 40, 11 cm
Balance, analytical
Funnel, separatory (2000 ml) with teflon stopcock
Flask, distilling 125 ml
Hot plate
Hot water bath
Vacuum source
Funnel, glass
D.	REAGENTS
1. Hydrochloric acid 1+1: Carefully, with stirring, add 25 ml
concentrated hydrochloric acid, HCI, to 25 ml distilled wa-
ter.
(Oil and Grease)
2.	Freon (1,1,2-trichloro -1,2,2-trifluoroethane) boiling point
47°C.
3.	Sodium sulfate, Na2S04, anhydrous crystal.
E. PROCEDURE
1.	Dry in oven (at 103°C) a clean distilling flask. Cool in des-
iccator. Weigh and record weight. Store in desiccator until
needed.
2.	Collect 1000 ml of sample in a glass container.
3.	Add 5 ml 1 +1 HCI to the sample.
4.	Transfer the liter sample to a 2000 ml separatory funnel.
5.	Carefully rinse the sample bottle with 30 ml freon. Add
these washings to the separatory funnel.
6.	Stopper and shake the separatory funnel vigorously for 2
minutes. Allow the two layers (water and freon) to sepa-
rate.
7.	Drain freon layer through funnel containing freon-
moistened filter paper into the tared (weighed) flask pre-
pared in Step 1. If the solvent layer is not clear, add 1
gram NajSC^ to the filter paper cone and slowly drain the
emulsified solvent onto the crystals. Add more Na2S04 if
necessary.
8.	Extract twice more with 30 ml freon, but first rinse sample
container with each solvent portion. Combine the extracts
in the tared flask and wash filter paper with 10 to 20 ml
freon.
9.	Distill freon from the extract flask in a water bath at 70°C.
Place the flask in a warm steam bath for 15 minutes and
draw air through the flask by means of a vacuum for the
final 1 minute.
10. Cool in desiccator for exactly 30 minutes and weigh.
F. EXAMPLE
Results from an effluent sample:
1.	1000 ml of sample
2.	Empty flask weighed 26.1024 grams
3.	Flask with residue weighed 26.1164 grams

-------
446 Treatment Plants
(Oil and Grease)
OUTLINE OF PROCEDURE
1. Dry flask in oven
at 103°C.
2. Cool in desiccator.
3. Weigh and store
until needed.
4. Collect 1000 ml of
sample and add 5 ml
1 + 1 HCI.
7. Extract twice with
30 ml freon.
to vacuum
¦ separatory
funnel
5. Transfer sample to
2000 ml separatory
funnel.
8. Distill freon from flask
in 70°C water bath.

water
layer
freon
Jj) layer
funnel
6. Drain freon layer
into weighed flask.
9. Draw air through
flask while on
steam bath.
10. Cool in desiccator
for 30 minutes.
11. Weigh and calculate
mgIL of oil and grease.

-------
Laboratory 447
G. CALCULATION
1. Oil and Grease, mg/L =
(A-B) x 1000
ml of sample
(Phosphorus)
B. WHAT IS TESTED?
where A = wei9ht of flask and resi-
due, mg
g _ weight of empty, dry flask,
mg
2. From example,
Oil = (A-B) x 1000
and	ml of sample
Grease
mg/L ' = (26,116.4 mg - 26,102.4 mg) (1000 ml/L)
(1000 ml/L)
14 mg/L
H. COMMENTS
1.	If oil and grease analysis is performed on sludge, then
another method must be used (see page 513, STANDARD
METHODS, 14th Edition).
2.	The collection of a composite sample is impractical be-
cause losses of grease will occur on sampling equipment.
I. REFERENCE
See page 515, STANDARD METHODS, 14th Edition.
12. Phosphorus
A. DISCUSSION
Wastewater is relatively rich in phosphorus compounds. The
forms of phosphorus found in wastewater are commonly clas-
sified into orthophosphate, condensed phosphate, and organi-
cally bound phosphate. Phosphorus is essential to the growth
of organisms found not only in a wastewater treatment plant,
but also in other bodies of water such as rivers, lakes, and
oceans. The discharge of wastewater containing phosphorus
may stimulate nuisance quantities of algal growths in receiving
waters.
In the past raw domestic wastewaters typically contained
approximately 10 mg/L of phosphorus. Phosphorus bans or
limitations in synthetic detergents or changes in detergent for-
mulas by the manufacturers have served to reduce this historic
level by varying amounts throughout the United States. Sec-
ondary biological treatment processes usually will reduce the
influent phosphorus concentrations by two to three mg/L.
'Greater removals may be obtained by the use of metal ion
coagulants such as alum (aluminum sulfate) or ferric chloride.
Other removal processes involve pH adjustment with lime.
Orthophosphate is the amount of inorganic phosphorus
(P04-3) in the sample of wastewater as measured by the di-
rect colorimetric analysis procedure. Total phosphorus is the
amount of all the phosphorus present in the sample regardless
of form, as measured by the persulfate digestion procedure
followed by colorimetric analysis. These are the two most
commonly measured forms in wastewater.
Sample
Influent
Effluent
Ortho Phosphate (P) Total Phosphorus (P)
Common Range, mg/L Common Range, mg/L
2 to 8
1 to 6
4 to 12
2 to 10
C.	APPARATUS
1.	Photometer — a spectrophotometer or filter photometer
suitable for measurements at 650 or 880 nanometers (nm)
wave length with a light path of 1 cm or longer. Follow
manufacturer's directions for operation.
2.	Balance, analytical, capable of weighing to 0.1 milligram.
3.	Balance, triple beam, capable of weighing to 0.1 gram.
4.	Desiccator.
5.	Hot plate or autoclave.
6.	Oven, drying for use at 105°C.
7.	pH meter.
8.	150 ml beakers or Erlenmeyer flasks.
9.	50 ml graduated cylinder.
10.	Pipets, measuring, 10 ml.
11.	Flasks, volumetric, 1000 ml and 100 ml.
D.	REAGENTS
1.	Ammonium molybdate—antimony potassium tartrate solu-
tion. Dissolve 8 grams of ammonium molybdate and 0.2
grams antimony potassium tartrate in 800 ml of distilled
water and dilute to one liter.
2.	Ascorbic acid solution. Dissolve 60 grams of ascorbic acid
in 800 ml of distilled water and dilute to one liter. Add 2 ml of
acetone. This solution is stable for two weeks.
3.	Sulfuric acid, 11 N. Slowly add 310 ml of concentrated sul-
furic acid to approximately 600 ml distilled water. Cool and
dilute to one liter.
4.	Ammonium persulfate.
5.	Stock phosphorus solution. Dissolve 0.4393 grams of pre-
dried (105°C for one hour) KH2P04 in a 1000 ml volumetric
flask containing distilled water. Dilute to 1000 ml. 1.0 ml of
this solution contains 0.1 mg phosphorus.
6.	Standard phosphorus solution. Dilute 100 ml of stock phos-
phorus solution to 1000 ml with distilled water. 1.0 ml of this
solution contains 0.01 mg P.
E.	PROCEDURE
For Orthophosphate:
1.	Place 50 ml of sample (or an aliquot diluted to 50 ml) and/or
standards in a 150 ml beaker or Erlenmeyer flask (see note
on glassware, page 451).
2.	Add 1 ml of 11 N sulfuric acid and 4 ml of ammonium
molybdate — antimony potassium tartrate and mix. (If sam-
ple has been digested for Total Phosphorus, do not add
acid.)
3.	Add 2 ml of ascorbic acid solution and mix.
4.	After 5 minutes, measure the absorbance at 650 nm with a
spectrophotometer and determine the amount of phos-
phorus from the standard curve. The color is stable for at
least one hour. Report results as P, mg/L.

-------
448 Treatment Plants
(Phosphorus)
OUTLINE OF PROCEDURE
FOR ORTHOPHOSPHATE
1. Place 50 ml or aliquot diluted
to 50 ml in flask.
2. Add 1 ml 11 N H2SO< and
4 ml ammonium molybdate
solution.

a

O
3. Add 2 ml ascorbic acid solution.
Mix. Let stand 5 minutes.
4. Measure absorbance at 650 nm
with spectrophotometer.
FOR TOTAL PHOSPHORUS
1. Place 50 ml or aliquot
diluted to 50 ml in
flask.
2. Add 1 ml 11 N H2S04 and
0.4 g of ammonium per-
sulfate. Mix.
3. Boil (or autoclave)
for 30 to 40 minutes.
4. Cool. Dilute to 50 ml. Determine amount
of phosphorus as outlined above.

-------
Laboratory 449
For Total Phosphorus:
1.	Place 50 ml of sample or an aliquot diluted to 50 ml into a
125 ml Erlenmeyer flask and add 1 ml of 11 N sulfuric acid.
2.	Add 0.4 grams ammonium persulfate, mix and boil gently
for approximately 30 to 40 minutes or until a final volume of
about 10 ml is reached. Alternatively heat for 30 minutes in
an autoclave at 121°C (15 to 20 psi or 1.0 to 1.4 kg/sq cm).
Cool and dilute to 50 ml.
3.	Determine amount of phosphorus as outlined above in or-
thophosphate.
Construction of Standard Calibration Curve:
1. Using the standard solution, prepare the following stan-
dards in 100 ml volumetric flasks.
ml of Standard Phosphorus Solution Phosphorus
Placed In 100 ml Volumetric Flask Concentration, mg/t
0
0
2.0
0.2
4.0
0.4
6.0
0.6
8.0
0.8
10.0
1.0
2.	Dilute flasks to 100 ml.
3.	Transfer 50 ml to 125 ml Erlenmeyer flask.
(Phosphorus)
4.	Determine amount of phosphorus as outlined previously in
orthophosphate.
5.	Prepare a standard curve by plotting the absorbance values
of standards versus the corresponding phosphorus concen-
trations.
F. EXAMPLE
Results from a series of tests for orthophosphate were as
follows:
Flask #
Sample
Volume
Absorbance
1
Plant Influent
5 ml
0.180
2
Plant Effluent
5 ml
0.122
3
Distilled Water
50 ml
0.000
4
0.2 mgIL P Standard
50 ml
0.075
5
0.4 mgIL P Standard
50 ml
0.152
6
0.6 mgIL P Standard
50 ml
0.230
7
0.6 mgIL P Standard
50 ml
0.300
G. CALCULATION
1. Prepare a standard curve by using data from prepared
standards. From the above example:
Concentration Phosphorus,
mg IL	Absorbance
0.0	0.000
0.2	0.075
0.4	0.152
0.6	0.230
0.8	0.300
The graph below is the result of plotting concentration of stan-
dards versus their corresponding absorbance.
.40
.30
.20
.10
.20 .30 .40 .50 .60
.10
.70
.80 .90 1.0
mgIL Phosphorus

-------
450 Treatment Plants
(Phosphorus)
2. Obtain concentration of unknown influent and effluent sam-
ples from curves.
•1 -2 .3 .4 .5 .6 .7 .8 .9 1.0
mgIL Phosphorus
3. Correct (if necessary) for samples of less than 50 ml by
using the following formula:
Phosphorus, mgIL P = mg/i. x 50
ml of sample used
Using data from example:
Sample	Concentration
Volume Absorbance from Graph
Plant Influent 5 ml	0.180	0.48 mgIL
Phosphorus, mgIL P =	x 50	
ml of sample used
= 0.48 x 50
5
¦ 4.8 mgIL P
Sample	Concentration
Volume Absorbance from Graph
Plant Effluent 5 ml	0.122	0.32 mgIL
Phosphorus, mgIL P = —rT^L x 50	
ml of sample used
= 0.32 x 50
5
= 0.32 x 10
= 3.2 mfl/L P

-------
Laboratory 451
H.	NOTES
I.	All glassware used should be washed with hot 1:1 HCI and
rinsed with distilled water. The acid-washed glassware
should be filled with distilled water and treated with all the
reagents to remove the last traces of phosphorus that might
be absorbed on the glassware. This glassware should be
used only for the determination of phosphorus and after use
it should be rinsed with distilled water and kept covered until
needed again. Commercial detergents should never be
used.
I. REFERENCE
See page 365.3-1 EPA's METHODS FOR CHEMICAL
ANALYSIS OF WATER AND WASTES, March 1979.
QUESTIONS
Write your answers in a notebook and then compare your
answers with those on page 462.
16.5V What forms of phosphorus are commonly found in
wastewater?
16.5W What can happen when phosphorus is discharged into
receiving waters?
13. Total Solids (Residue)
The term "solids" or "residue" refers to the matter sus-
pended and dissolved in wastewater or water.
I. Total Solids
A.	DISCUSSION
"Total solids" is the term applied to material left in the con-
tainer after evaporation of a sample in an oven at 103° to
105°C.
B.	WHAT IS TESTED?
Sample	Common Range, mgIL
Influent and Effluent	300 to 1200
C.	APPARATUS REQUIRED
Evaporating dishes (100 ml capacity)
Drying oven
Desiccator
Analytical balance
Muffle furnace
(Total Solids)
D.	PROCEDURE
Preparation of evaporating dish.
1.	Ignite a clean evaporating dish at 550 ± 50°C for one hour
in a muffle furnace.
2.	Cool in desiccator, weigh, and record weight. Store in des-
iccator until ready for use.
Sample analysis.
1.	Shake sample vigorously and transfer a measured amount
of sample to the pre-weighed dish and evaporate to dry-
ness in a drying oven at 103° to 105°C. Choose a sample
volume that will yield a minimum residue of 25 milligrams to
250 milligrams. If necessary add additional portions of
sample to the same dish.
2.	Dry the evaporated sample for at least one hour at 103° to
105°C.
3.	Cool the dish in a desiccator. Weigh and record weight.
Repeat the drying cycle until a constant weight is obtained
or until weight loss is less than 0.5 milligrams.
E.	EXAMPLE
Results from an effluent sample were:
Weight of clean dish = 80.1526 grams
Weight of residue and dish = 80.1732 grams
Sample volume	= 100 ml
F.	CALCULATIONS
1.	Total Solids, mgIL = (A-B) x 1000
ml of sample
where, A = Weight of dish and residue in milligrams
B = weight of dish in milligrams
2.	From example,
Total Solids, mg/L = (A-B) x 1000
ml of sample
= (80,173.2 mg - 80,152.6 mg) (1000 ml/L)
100 ml
= 206 mg/L
G.	REFERENCE
See page 91, STANDARD METHODS, 14th Edition.

-------
452 Treatment Plants
(Total Solids)
OUTLINE OF PROCEDURE FOR TOTAL SOLIDS
1. Ignite dish at 550°C.
2. Cool in desiccator.
3. Weigh dish.
4. Pour measured volume in dish.
5. Dry dish plus sample at
103°C to dryness.
£2.
w
6. Cool in desiccator.
7. Weigh dish plus total solids.

-------
Laboratory 453
II. Total Dissolved (Filterable) Solids
A.	DISCUSSION
"Total dissolved solids" (TDS) refers to material that passes
through a standard glass-fiber filter disc and remains after
evaporation at 180°C.
B.	WHAT IS TESTED?
Sample	Common Range, mg/L
Influent and Effluent	150 to 600
C.	APPARATUS REQUIRED
Glass-fiber filter discs (Reeve Angel Type 934A, 984H; or
Gelman Type A/E)
Flask, suction 500 ml
Filter holder or Gooch crucible adapter
Gooch crucibles (25 ml if 2.2 cm filter used)
Evaporating dishes, 100 ml
Drying oven, 180°C
Steam bath
Vacuum source
Desiccator
Analytical balance
Muffle furnace, 550°C
D.	PROCEDURE
Preparation of Dish
1.	Ignite a clean evaporating dish at 550 ± 50°C for one hour
in muffle furnace.
2.	Cool in desiccator then weigh and record weight. Store in
desiccator until needed.
Preparation of Glass-fiber Filter Disc
1. Place the disc on the filter apparatus or insert into the bot-
tom of a suitable Gooch crucible. While vacuum is applied,
wash the filter disc with three successive 20 ml volumes of
distilled water. Continue the suction to remove all traces of
water from the disc and discard the washings.
Sample Analysis
1.	Shake the sample vigorously and transfer 125 to 150 ml to
the funnel or Gooch crucible by means of a 150 ml
graduated cylinder.
2.	Filter the sample through the glass-fiber filter and continue
to apply vacuum for about three minutes after filtration is
complete to remove as much water as possible.
3.	Transfer 100 ml of the filtrate to the weighed evaporating
dish and evaporate to dryness on a steam bath.
4.	Dry the evaporated sample for at least one hour at 180°C.
Cool in desiccator and weigh. Repeat drying cycle until
constant weight is obtained or until weight loss is less than
0.5 mg.
E.	EXAMPLE
(Total Solids)
F.	CALCULATIONS
1.	Total Dissolved Solids, mg/L = —(A-B) x 1000	
ml sample volume
where, A = weight of dish and dissolved
material in milligrams (mg)
B = weight of clean dish in milli-
grams (mg)
2.	From example,
Total Dissolved _ (A-B) x 1000
Solids, mg/L m| sample volume
(47,045.3 mg - 47,002.8 mg) (1000 ml/L)
100 ml
= 425 mg/L
G.	COMMENTS
Because excessive residue in the evaporating dish may
form a water-entrapping crust, use a sample that yields no
more than 200 mg of residue.
H.	REFERENCE
See page 92, STANDARD METHODS, 14th Edition.
III. Suspended Solids
See Section 16.43 for procedure to measure Suspended
Solids.
QUESTION
Write your answer in a notebook and then compare your
answer with the one on page 462.
16.5X Determine the total solids (residue) and total dissolved
(filterable) solids from the following lab test results.
Weight of empty dish	=	64,328.9 mg
Weight of dish and residue	=	64,381.2 mg
Weight of dish and dissolved material	= 64,351.2 mg
Sample volume	= 100 ml
14. Specific Conductance
A.	DISCUSSION
Specific conductance or conductivity is a numerical expres-
sion (expressed in micromhos per centimeter) of the ability of a
water or wastewater to conduct or carry an electrical current.
This number depends on the total concentration of the miner-
als dissolved in the sample and the temperature. The conduc-
tivity of wastewater reflects to a degree the characteristics of
the water supply servicing the area.
Specific conductance is measured by the use of a conductiv-
ity meter.
B.	WHAT IS TESTED?
8amp<*	Common Range,
mleromhos/cm
Results from weighings were:
Clean dish	= 47.0028 grams (47,002.8 mg)
Dissolved residue + dish - 47.0453 grams (47,045.3 mg)
Sample volume	= 100 ml
Influent and Effluent	200 to 1000
C. MATERIALS AND PROCEDURE
See page 71, STANDARD METHODS, 14th Edition.

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454 Treatment Plants
(Total Solids)
OUTLINE OF PROCEDURE FOR TOTAL DISSOLVED SOLIDS
n
1. Ignite dish at 550°C
for 1 hour in muffle
furnace.
2. Cool
3. Weigh and store
in desiccator.

4. Place glass-fiber
disc in crucible.
7. Filter out suspended
material. Transfer 100 ml
of filtrate to weighed dish.
5. Wash filter-crucible
with distilled water.
u
9. Evaporate to
dryness on
steambath.
6. Pour 100 ml sample
into Gooch crucible.
10. Dry evaporated sample
for 1 hour
11. Cool in desiccator.
12. Weigh.

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Laboratory 455
QUESTION
Write your answer in a notebook and then compare your
answer with the one on page 462.
16.5Y What property of wastewater is measured by the spe-
cific conductance test?
15. Sulfate
A.	DISCUSSION
Sulfate ions are widely distributed in wastewaters in concen-
trations ranging from a few to several thousand milligrams per
liter. Sulfate is of considerable concern in wastewater because
sulfate ions are indirectly responsible for two serious problems:
odor and sewer corrosion problems. These problems are a
result of the bacterial reduction of sulfate to hydrogen sulfide.
Also, hydrogen sulfide is a toxic gas which is flammable and
explosive.
B.	WHAT IS TESTED?
(Temperature)
rapidly. Always leave the thermometer in the liquid while read-
ing the temperature. Record temperature on a suitable work
sheet, including time, location, and sampler's name.
Thermometers are calibrated for either total immersion or
partial immersion. A thermometer calibrated for total immer-
sion must be completely immersed in the wastewater sample
to give a correct reading, while a partial immersion thermome-
ter must be immersed in the sample to the depth of the etched
circle around the stem for a correct reading.
B. WHAT IS TESTED?
Sample
Influent21
Effluent21
Sample
Effluent
Common Range
Depends on water supply
and industrial discharges.
Common Range
65°F to 85°F22
(18°C to 29°C)
60°F to 95°F
(16°C to 35°C)
or higher from ponds
60°F (16°C) to
ambient temperature23
60°F to 100 °F
(16°C to 38°C)
C. MATERIALS AND PROCEDURE
See page 493, STANDARD METHODS, 14th Edition.
16.	Surfactants
A.	DISCUSSION
The single most widely used surfactant (surface active
agent) in detergents is LAS. LAS is short for linear alkylate
sulfonate. LAS is used as the standard compound in surfactant
analysis.
The test for surfactants consists of adding a methylene blue
dye to the wastewater sample. Methylene blue dye reacts with
surfactants, such as LAS, to form a blue-colored salt. This blue
salt is extracted with chloroform and the intensity of the blue
color measured.
B.	WHAT IS TESTED?
Sample	Common Range, mg/L
Secondary Effluent	0.1 to 1
C.	MATERIALS AND PROCEDURE
See page 600, STANDARD METHODS, 14th Edition.
17.	Temperature
A. DISCUSSION
Temperature is one of the most important factors affecting
biological growth. Temperature measurements can be helpful
in detecting changes in raw wastewater quality. For example,
an influent temperature drop may indicate large volumes of
cold water from infiltration. An increase in temperature may
indicate that hot water discharges by industry are reaching
your plant.
Temperature is one of the most frequently taken tests. One
of the many uses is to calculate the percent saturation of dis-
solved oxygen in the DO test.
A temperature measurement should be taken where sam-
ples are collected for other tests. This test is always im-
mediately performed on a grab sample because it changes so
21	H dissolved oxygen (DO) measurements are performed on any samples, the temperature should be measured and recorded.
22	Depends on season, location, and temperature of water supply.
23	Ambient Temperature (Am-bee-ent). Temperature of the surroundings.
Receiving Water
Digester (Recirculated
Sludge before Heat
Exchanger and Supernatant)
C.	APPARATUS
1.	One NBS (National Bureau of Standards) thermometer for
calibration of the other thermometers
2.	One Fahrenheit mercury-filled, 1° subdivided thermometer
3.	One Celsius (formerly called Centigrade) mercury-filled, 1°
subdivided thermometer
4.	One metal case to fit each thermometer
There are three types of thermometers and two scales.
SCALES
1.	Fahrenheit, marked °F
2.	Celsius, marked °C (formerly Centigrade)
THERMOMETERS
1.	Total immersion. This type of thermometer must be totally
immersed when read. This will change most rapidly when
removed from the liquid to be recorded.
2.	Partial immersion. This type thermometer will have a solid
line around the stem below the point where the scale starts.
3.	Dial. This type has a dial that can be easily read while the
thermometer is still immersed. Dial thermometer readings
should be checked (calibrated) against the NBS thermome-
ter. Some dial thermometers can be recalibrated (adjusted)
to read the correct temperature of the NBS thermometer.
D.	REAGENTS
None
E.	PROCEDURES
Use a large volume of sample, preferably at least a 2-pound
coffee can or equivalent volume. The temperature will have
less chance to change in a large volume than in a small con-
tainer. Collect sample in container and immediately measure
and record temperature. Do not touch the bottom or sides of
the sample container with the thermometer. To avoid breaking
or damaging a glass thermometer, store it in a shielded metal

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456 Treatment Plants
(TOC)
case. Check your thermometer accuracy against the NBS cer-
tified thermometer by measuring the temperature of a sample
with both thermometers simultaneously. Some of the poorer
quality thermometers are substantially inaccurate (off as much
as 6°F or 3°C).
F.	EXAMPLE
To measure influent temperature, obtain sample in large cof-
fee can, immediately immerse thermometer in can, and record
temperature when reading becomes constant. For example,
72°F or 22°C.
G.	CALCULATIONS
Normally, we measure and record temperatures using a
thermometer with the proper scale. However, we could mea-
sure a temperature in °F and convert to °C, or we might mea-
sure a temperature in °C and convert to °F. The following for-
mulas are used to convert temperatures from one scale to the
other.
1.	Measure in 8F, want °C:	°C = 5/9(°F - 32°)
2.	Measure in °C, want °F:	°F = 9/5(°C) + 32°
3.	Example Calculation;
The measured influent temperature was 77°F. What was
the temperature in °C?
°C = 5/9(°F - 32°) yy
= 5/9(77° - 32°) -32
= 5/9(45°)	45	5
= 25°	9)45	5
x_5
25
QUESTIONS
Write your answers in a notebook and then compare your
answers with those on page 462.
16.5Z What could a change in influent temperature indi-
cate?
16.5AA Why should the thermometer remain immersed in
the liquid while being read?
16.5BB Why should thermometers be calibrated against an
accurate NBS certified thermometer?
18. Total Organic Carlson (TOC)
A. DISCUSSION
The carbon analyzer measures all carbon in a sample. Be-
cause of the various properties of carbon-containing com-
pounds in wastewater samples, preliminaiy treatment of the
sample prior to analysis dictates the definition of the carbon
measured. Such forms include soluble, insoluble, volatile,
non-volatile, and particulate carbon.
The value of the total carbon measurement is found in the
fact that it is a more direct expression of organic chemical
content of wastewater than either the chemical oxygen de-
mand (COD) or the biochemical oxygen demand (BOD).
Therefore the TOC test can be used to monitor wastewater
treatment processes.
B.	WHAT IS TESTED?
Sample	Common Range, mgIL
Influent	100 - 300
Effluent	10-100
C.	MATERIALS AND PROCEDURES
See page 532, STANDARD METHODS, 14th Edition.
19. Turbidity
A.	DISCUSSION
The term turbidity is simply an expression of the physical
clarity of water or wastewater. Turbidity can be caused by the
presence of suspended matter such as mud, finely divided
organic and inorganic matter, and microscopic organisms such
as algae.
The turbidity measurement is useful for plant effluent
monitoring; however problems can be encountered when one
instrument's readings are compared with those of another.
Commercial turbidimeters come in many shapes and sizes.
They each can read different turbidity values on the same
sample even though they have been calibrated using the pro-
cedure given later in this section. The operator should simply
be aware of this shortcoming.
The accepted used to measure turbidity is called
nephelometric. The nephelometric turbidimeter is designed to
measure particle reflected light at an angle of 90 degrees. The
greater the intensity of the scattered light, the higher the turbid-
ity.
B.	WHAT IS TESTED?
Sample	Common Range, NTU
Effluent	10-50
C.	APPARATUS
1.	Turbidimeter: The turbidimeter should consist ot a
nephelometer with a light source illuminating the samples
and one or more photo-electric detectors with a readout
device to indicate the intensity of scattered light. Tur-
bidimeters used to test plant effluents should be approved
by the U.S. Environmental Protection Agency.
2.	Sample tubes
D.	REAGENTS
1.	Turbidity-free water: Pass distilled water through a mem-
brane filter having a pore size no greater than 100 microns.
Discard the first 200 ml collected. If filtration does not re-
duce turbidity, use distilled water.
2.	Stock Formazin turbidity suspension:
a.	Solution I. Dissolve 1.000 g hydrazine sulfate in distilled
water and dilute to 100 ml in a volumetric flask.
b.	Soluton II. Dissolve 10.00 g hexamethylenetetramine in
distilled water and dilute to 100 ml in a volumetric flask.
c.	In a 100 ml volumetric flask, add (using 5 ml volumetric
pipets) 5.0 ml Solution I and 5.0 ml of Solution II. Mix
and allow to stand 24 hours at 25°C. Then dilute to the
mark and mix. The turbidity of this suspension is 400
NTU.
d.	Prepare solutions and suspensions monthly.

-------
Laboratory 457
(Turbidity)
3.	Standard turbidity suspensions. Dilute 10.00 ml stock tur-
bidity suspension to 100 ml with turbidity-free water. Pre-
pare weekly. The turbidity of this suspension is defined as
40 NTU.
4.	Dilute turbidity standards. Dilute portions of the standard
turbidity suspension with turbidity-free water as required.
Prepare weekly.
E.	PROCEDURE
1.	Turbidimeter calibration. The manufacturer's operating in-
structions should be followed. Measure standards on the
turbidimeter covering the range of interest. If the instrument
is already calibrated in standard TURBIDITY UNITS24, this
procedure will check the accuracy of the calibration scales.
At least one standard should be run in each instrument
range to be used. Some instruments permit adjustments of
sensitivity so that scale values will correspond to turbidities.
Reliance on a manufacturer's solid scattering standard for
setting overall instrument sensitivity for all ranges is not an
acceptable practice unless the turbidimeter has been
shown to be free of drift on all ranges. If a pre-calibrated
scale is not supplied, then calibration curves should be pre-
pared for each range of the instrument.
2.	Turbidities less than 40 units: Shake the sample to thor-
oughly disperse the solids. Wait until air bubbles disappear,
then pour the sample into the turbidimeter tube. Read the
turbidity directly from the instrument scale or from the ap-
propriate calibration curve.
3.	Turbidities exceeding 40 units: Dilute the sample with one
or more volumes of turbidity-free water until the turbidity
falls below 40 units. The turbidity of the original sample is
then computed from the turbidity of the diluted sample and
the dilution factor.
F.	EXAMPLE
If 5 volumes of turbidity-free water were added to 1 volume
of sample, and the diluted sample showed a turbidity of 20
units, then the turbidity of the original sample was 100 units.
G. CALCULATIONS
Sample reading x dilution
Report results as follows:
NTU
0.0 - 1.0
1 - 10
10 -40
40 -100
100 - 400
400 - 1000
>1000
H. NOTES AND PRECAUTIONS
actual turbidity.
Record to Nearest:
0.05
0.01
1
5
10
50
100
1.	A commercially available polymer standard that requires no
preparation is also approved for use. This standard is iden-
tified as AMCO-AEPA-1 available from Amco Standard In-
ternational, Inc., 230 Polaris Avenue #C, Mountain View,
CA 94043.
2.	Sample tubes must be kept scrupulously clean, both inside
and out. Discard them when they become scratched or
etched. Never handle them where the light strikes them.
3.	Fill the tubes with samples and standards that have been
agitated thoroughly, and allow sufficient time for bubbles to
escape.
I . REFERENCE
See page 132, STANDARD METHODS, 14th Edition.
QUESTION
Write your answer in a notebook and then compare your
answer with the one on page 462.
16.5CC What causes turbidity in wastewater?
6KJP OF L&6-SdN 9 OF 9 Le
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458 Treatment Plants
DISCUSSION AND REVIEW QUESTIONS
Chapter 16. LABORATORY PROCEDURES AND CHEMISTRY
(Lesson 9 of 9 Lessons)
Write the answers to these questions in your notebook. The
question numbering continues from Lesson 8.
44.	What are the most important forms of nitrogen in wastewa-
ter treatment?
45.	What water quality problems are related to ammonia?
46.	The oil and grease test measures what kinds of materials?
47.	How can phosphorus be removed from wastewater?
48.	What does the total solids (residue) test measure?
49.	Why is sulfate of concern in wastewater?
50.	What is the main advantage of the total organic carbon
(TOC) test?
51.	What is the ambient temperature?
52.	Convert a temperature reading of 50°F to degrees Celsius.
PLEASE WORK THE OBJECTIVE TEST NEXT.
SUGGESTED ANSWERS
Chapter 16. LABORATORY PROCEDURES AND CHEMISTRY
Answers to questions on page 350.
16.1A Descriptions of laboratory items and their use or pur-
pose.
Item	Description	Use or Purpose
1.	Beakers Short, wide cylinders Mixing chemicals.
in sizes from 1ml to
4000 ml.
2.	Graduated Long, narrow cylin- Measuring volumes.
Cylinders ders in sizes from 5 ml
to 4000 ml.
Delivering accurate
volumes.
3.	Pipets Very thin tubes with a
pointed tip in sizes
from 0.1 ml to 100 ml.
4.	Burets Long tubes with Delivering and
graduated walls and a measuring accurate
stop-cock in sizes volumes used in "titra-
from 10 to 1000 ml. tions."
16.1 B Never heat graduated cylinders in an open flame be-
cause they will break.
16.1C A BENCH SHEET is used to record data and arrange
data in an orderly manner. Bench sheets also are
called LABORATORY WORK SHEETS.
END OF ANSWERS TO QUESTIONS IN LESSON 1
Answers to questions on page 358.
16.2A A bulb should always be used to pipet wastewater or
polluted water to prevent infectious materials from en-
tering your mouth.
16.2B Inoculations are recommended to reduce the possibil-
ity of contracting diseases.
16.2C Immediately wash area where acid spilled with water
and neutralize the acid with sodium carbonate or
bicarbonate.
16.2D True. You may add acid to water, but never reverse.
END OF ANSWERS TO QUESTIONS IN LESSON 2
Answers to questions on page 363.
16.3A The largest sources of errors found in laboratory re-
sults are usually caused by improper sampling; poor
preservation; and lack of sufficient mixing, composit-
ing, and testing.
16.3B A representative sample must be collected or the test
results will not have any significant meaning. To effi-
ciently operate a wastewater treatment plant, the
operator must rely on test results to indicate what is
happening in the treatment process.
16.3C A proportional composite sample may be prepared by
collecting a sample every hour. The size of this sam-
ple is proportional to the flow when the sample is col-
lected. All of these proportional samples are mixed
together to produce a proportional composite sample.
If an equal volume of sample was collected each hour
and mixed, this would simply be a composite sample.
END OF ANSWERS TO QUESTIONS IN LESSON 3

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Laboratory 459
Answers to questions on page 364.
16.4A The clarity test indicates the relative change of depth
you can see down in the final clarifier or contact basin.
This reflects a visual comparison of color, solids, and
turbidity from one test to the next. OR Indication of
quality of effluent.
16.4B When clarity is measured under different conditions
the results cannot be compared. You won't be able to
tell whether your plant performance is improving, stay-
ing the same, or deteriorating.
Answer to question on page 366.
16.4C (1) You would measure the H2S in the wastewater to
know the strength of H2S and to provide an indica-
tion of the corrosion taking place on the concrete.
(2) H2S in the atmosphere produces a rotten egg
odor. It is indicative of anaerobic decomposition of
organics in wastewater which occurs in the ab-
sence of oxygen. High levels of H2S are toxic to
your respiratory system and can create flammable
and explosive conditions.
Answer to question on page 367.
16.4D Sludge to
Digester, = (Total SS Removed, ml/Z.)(1000)(Flow, MGD)
gpd
= (10 mlIL - 0.4 ml/t)(1000 mg/ml)(1 M Gal/day)
9.6 ml x 100 mg x 1 M gal
ml	day
M mg
= 9600 gpd
This value may be reduced by 30 to 75 percent due to
compaction of the sludge in the clarifier.
Answers to questions on page 371.
16.4E The specific gravity is very near that of water and is
not light enough to float nor heavy enough to settle.
16.4F Solids calculations will be shown in detail here to illus-
trate the computational approach and the units in-
volved. After you understand this approach, use of the
laboratory work sheet is more convenient.
a. Total Suspended Solids
Volume of Sample, ml = 100 ml
Weight of Dried Sample & Dish, grams = 19.3902 g
Weight of Dish (Tare Weight), grams	= 19.3241 g
Dry Weight = 0.0661 g
or = 66.1 mg
Total
Suspended
Solids, mg//.
_ Weight of Solids, mg x 1000 mlIL
Volume of Sample, ml
= 66.1 mg x 1000 ml/Z.
100 ml
= 661 mgIL
b. Volatile Suspended Solids
Weight of Dried Sample & Dish, grams
Weight of Ash & Dish, grams
Weight Volatile, grams
= 19.3902 g
= 19.3469 g
= 0.0433 g
or = 43.3 mg
Volatile _ Weight of Volatile, mg x 100 ml IL
Suspended
Solids, mgIL
Volume of Sample, ml
= (43.3 mg)(1000 ml IL)
100 ml
= 433 mgIL
c. Percent Volatile Solids
% Volatile Solids = Weight Volatile, mg x 100%
Weight Dry, mg
= 43.3 mg x 100<,/o
66.1 mg	.655
= 65.5%	661 )433.0
d.	Fixed Solids
Total Suspended Solids, mgIL = 661 mgIL
Volatile Suspended Solids, mgIL = 433 mgIL
Fixed Solids, mgIL	= 226 mgIL
e.	Percent Fixed Solids
Total Solids, % = 100.00%
Volatile Solids, % = 65.50%
Fixed Solids, % = 34.5 %
or
% Fixed = Fixed- mg x 100%
Total, mg
= 22 8 m9 x 100%
66.1 mg
= 34.5% (Check)
16.4G Calculate Percent Reduction through Primary:
In = Influent to plant
or unit
Out = What is leaving
plant or unit
% Removal = (ln ' 0ut) x 100%
In
= (221 mgIL -159 mg/L)y 1Q0%
221 mgIL
= 62 x 100%
396 6
36 40
33 05
3 350
3 305
221
= 28% reduction
through primary
.28
221)62.0
442
1780
1768

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460 Treatment Plants
Calculate Percent Removal by Secondary System:
In =159 mg/L SS in	.79
primary effluent	159)126.0
Out = 33 mg/L SS in	1113
final effluent	14 70
1431
% Removal = (ln ' °ut) x 100%
In
_ (159 mg/L - 33 mg/L) ^ 00O/o
159 mg/L
= 79% removal from primary
effluent to final effluent
Calculate Overall Plant Efficiency:
In = 221 mg/L SS in
plant influent
Out = 33 mg/L SS in
plant effluent
% Removal = (|n ' °ut) x 100%
In
= (221 m9/L ' 33 m9/L> x 100%
221 mg/L
= 188 x 100%
221
= 85.5% overall plant removal
16.4H Calculate the pounds of solids removed per day by
each unit:
Amount
Removed, = Cone. Red., mg/L x Flow, MGD x 8.34 lb/gal
lb/day
where MGD = million gallons per day
A.	Influent, mg/L	= 221 mg/L
Primary Effluent, mg/L	= 159 mg/L
Primary Removal, mg/L	= 62 mg/L
Amount Removed,
lb/day (Primary) = (62 mg/L) (1.5 MGD)(8.34 lb/gal)
= 775.6 lbs/day removed
by primary
B.	Primary Effluent, mg/L	= 159 mg/L
Final Effluent, mg/L	= 33 mg/L
Secondary Removal, mg/L =126 mg/L
Amount Removed,
lb/day (Secondary) = (126 mg/L)(1.5 MGD)(8.34 lb/gal)
= 1576 lb/day removed
by secondary
C. Influent, mg/L	= 221 mg/L
Final Effluent, mg/L	= 33 mg/L
Overall Removal, mg/L	= 188 mg/L
Amount Removed,
lb/day	= (188 mg/L)(1.5 MGD)(8.34 lb/gal)
= 2351 lbs/day removed by plant
= Primary Removal, lb/day +
Secondary, lb/day
or = 775 + 1576
= 2351 (Check)
Answers to questions on page 376.
16.41 Volatile solids found in a digester are organic com-
pounds of either plant or animal origin.
16.4J Volatile solids in a treatment plant indicate the portion
of material that may be treated by biological pro-
cesses.
END OF ANSWERS TO QUESTIONS IN LESSON 4
Answers to questions on page 378.
16.4K Settleability tests should be run on the mixed liquor to
determine the settling characteristics of the sludge floe
at regular intervals for 60 minutes. The results are
used in the SVI and SDI determinations.
16.4L The SVI is the VOLUME in ml occupied by one gram of
mixed liquor suspended solids after 30 minutes of
settling.
16.4M The SVI test is used to indicate changes in sludge
characteristics.
16.4N Sludge Density Index (SDI) = 100/SVI.
Answer to question on page 379.
16.40 The sludge age of 200,000 gallon aeration tank that
has 2000 mg//L mixed liquor suspended solids, a pri-
mary effluent of 115 mg/L SS, and an average flow of
1.8 MGD:
Sludge _ Vol of Aeration Tank, .2 MG x Sus Solids, 2000 mg/L
Age, days	Flow, MGD, 1.8 x Primary Effluent, 115 mgIL
_ 0.2 MG x 2000 mg/L
1.8 MGD x 115 mg/L
= 1.93 days
Answer to question on page 380.
16.4P When the DO in the aeration tank is very low, the
copper sulfate-sulfamic acid procedure can give high
results. The results are high because oxygen enters
the sample from the air when the sample is collected,
when the copper sulfate-sulfamic acid inhibitor is add-
ed, while the solids are settling, and when the sample
is transferred to a BOD bottle for the DO test.
Answer to question on page 382.
16.4Q The advantages of the centrifuge over the regular
suspended solids test are:
(1)	Speed of answer! Not as accurate as other
methods, but results are sufficiently close.
(2)	Answers very acceptable if suspended solids con-
centration is below 1500 mg/L.
DISADVANTAGE: Small plants cannot always afford
the $500 or more cost of the centrifuge.
Answer to question on page 383.
16.4R In order to calculate the Mean Cell Residence Time
(MCRT), measure representative composite samples
of mixed liquor suspended solids, effluent suspended
solids, and waste sludge suspended solids. Also mea-
sure influent and waste sludge flows.

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Laboratory 461
Answer to question on page 387.
16.4S Volatile Acid _ ml 0.05 N NaOH x 2500
Alkalinity, mg/L
ml Sample
5 ml x 2500
50 ml
= 250 mgIL
Since 250 mgIL > 180 mgIL,
Volatile Acids,
mgIL	= Volatile Acid Alkalinity x 1.50
= 250 mgIL x 1.50
= 375 mgIL
Answers to questions on page 389.
16.4T The alkalinity test is run to determine the buffer capac-
ity and the volatile acids/alkalinity relationship in a di-
gester.
16.4U The buffer capacity in a digester as measured by the
total alkalinity tests indicates the capacity of the diges-
ter to resist changes in pH.
16.4V Volatile Acid = 300 mgIL
Alkalinity
2000 mg IL
= 0.15
Answers to questions on page 391.
16.4W The dangers encountered in running the C02 test on
digester gas include:
1.	Digester gas contains methane, which is explosive
when mixed with air.
2.	The COz gas absorbent is harmful to your skin.
% CO = (Total Volume, ml - Gas Remaining, ml) x 100%
Total Volume, ml
= (128 ml - 73 ml) x 100% 128
128 ml
= 	 x 100%
128	43
128)55.0
16.4X
55
= 43%
51 2
380
384
Answer to question on page 393.
16.4Y (1) Results from the graduated cylinder are available
immediately, but different operators may interpret
the results differently.
(2) Results are not available until the next day, but
different operators will record the same results.
Answer to question on page 395.
16.4Z If the supernatant solids test is greater than 5 percent,
the supernatant could be placing a heavy solids load
on the plant and the appropriate operational adjust-
ments should be made.
Answer to question on page 397.
16.4AA Lime is used as a coagulant in treating industrial
wastes and as a means of removing phosphorus.
END OF ANSWERS TO QUESTIONS IN LESSON 5
Answer to question on page 399.
16.5A Some sources of acidity in a treatment plant influent
include carbon dioxide from the atmosphere, from the
biological oxidation of organic matter or from indus-
trial waste discharges.
Answer to question on page 401.
16.5B Bicarbonate ions (HC03~) represent the major form
of alkalinity in wastewater.
Answers to questions on page 403.
16.5C The COD test is a measure of the strength of a waste
in terms of its chemical oxygen demand. It is a good
estimate of the first-stage oxygen demand. (Either
answer is acceptable.)
16.5D The advantage of the COD test over the BOD test is
that you don't have to wait five days for the resutls.
Answer to question on page 405.
16.5E Sulfide, thiosulfate, and sulfite ions interfere with the
chloride test, but can be removed by treatment with 1
ml of 30 percent hydrogen peroxide (H202).
Answers to questions on page 408.
16.5F Plart effluents should be chlorinated for disinfection
purposes to protect the bacteriological quality of the
receiving waters.
16.5G The iodometric method gives good results with sam-
ples containing wastewater, such as plant effluent or
receiving waters. Amperometric titration gives satis-
factory results, but the equipment is expensive.
END OF ANSWERS TO QUESTIONS IN LESSON 6
Answers to questions on page 423.
16.5H Sodium thiosulfate crystals should be added to sam-
ple bottles for coliform bacteria tests before steriliza-
tion to neutralize any chlorine that may be present
when the sample is collected. Care must be taken not
to wash the bottles out when a sample is collected.
16.51 121°C within 15 minutes.
16.5J Dilutions	-2 -3 -4 -5
Readings	5 12 0
MPN = 63,000/100 ml
16.5K The number of coliforms is estimated by counting the
number of colonies grown on the membrane filter.
END OF ANSWERS TO QUESTIONS IN LESSON 7
Answers to questions on page 427.
16.5L
DO Saturation. % = DO of Sample, mgIL x 100%
DO at Saturation, mgIL
_ (7.9 mgIL) 100%
11.3 mg/t
= 70%
.699
11.3)7.90
6 78
1 120
1 017
1030
1017

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462 Treatment Plants
16.5M To calibrate the DO probe in an aeration tank, a sam-
ple of the effluent can be collected and split. The DO
of the effluent is measured by the Modified Winkler
procedure, and the probe DO reading is adjusted to
agree with the Winkler results.
Answers to questions on page 431.
16.5N BOD test or volatile solids test.
16.50 To prepare dilutions for a cannery waste with an ex-
pected BOD of 2000 mg/L, take 10 ml of sample and
add 90 ml of dilution water to obtain a new sample
with an estimated BOD of 200 mg/L (10 to 1 dilution):
16.5P
BOD Dilution, ml =
1200
Estimated BOD, mg/L
1200
200
= 6 ml
BOD Bottle Vol., ml
[ 300 ml "I
2 ml J
[Initial DO DO of Diluted"!
of Diluted . Sample After I | j	
Sample, mg/L 5-Day Incuba- I I sample Volume, ml
tion, mg/L J
= (7.5 mg/L - 3.9 mg/L)
= (3.6 mg/L)(150)
= 540 mg/L
16.5Q Samples for the BOD test should be collected before
chlorination because chlorine interferes with the or-
ganisms in the test. It is difficult to obtain accurate
results with dechlorinated samples.
16.5R A solution of sodium thiosulfate at 0.025 N is very
weak and unstable and will not remain accurate over
two weeks.
END OF ANSWERS TO QUESTIONS IN LESSON 8
Answers to questions on page 451.
16.5V Forms of phosphorus commonly found in wastewa-
ter include orthophosphate, condensed phosphate,
and organically bound phosphate.
16.5W The dischrage of wastewater containing phosphorus
may stimulate nuisance quantities of algal growths
in receiving waters.
Answer to question on page 453.
16.5X
Known
Empty dish
Dish and residue
Dish and dissolved
solids
Sample volume
= 64,328.9 mg
= 64,381.2 mg
=64,351.2 mg
= 100 ml
Unknown
1.	Total Solids, mg/L
2.	Dissolved solids,
mg/L
1. Calculate Total Solids (Residue)
Total Solids,
mg/L
(A-B) 1000
ml of sample
(64,381.2 mg - 64,328.9 mg) (1000 ml/L)
100 ml
= 523 mg/L
2. Calculate Total Dissolved Solids (Filterable)
Total Dis. _ (A-B) 1000
Solids, mg/L m| of samp|e
_ (64,351.2 mg - 64,328.9 mg) (1000 ml/L)
100 ml
= 223 mg/L
Answer to question on page 455.
16.5Y Specific conductance measures the ability of waste-
water to conduct or carry an electric current. This abil-
ity depends on the total concentration of minerals dis-
solved in the wastewater and the temperature.
Answer to question on page 433.
16.5S Precautions to be exercised when using a pH meter
include:
(1)	Prepare fresh buffer solution weekly for calibra-
tion purposes.
(2)	pH meter, samples, and buffer solutions should
all be at the same temperature.
(3)	Watch for erratic results arising from faulty op-
eration of pH meter or fouling of electrodes with
interfering matter.
Answer to question on page 433.
16.5T Operators test for metals in wastewater because of
the toxic properties of metals.
Answer to question on page 445.
16.5U Kjeldahl nitrogen refers to ORGANIC PLUS AM-
MONIA NITROGEN.
Answers to questions on page 456.
16.5Z Changes in influent temperature could indicate a
new influent source. A drop in temperature could be
caused by cold water from infiltration, and an in-
crease in temperature could be caused by an indus-
trial waste discharge.
16.5AA The thermometer should remain immersed in the
liquid while being read for accurate results. When
removed from the liquid, the reading will change.
16.5BB All thermometers should be calibrated against an
accurate National Bureau of Standards thermometer
because some thermometers that are substantially
inaccurate (off as much as 6°F) can be purchased.
Answer to question on page 457.
16.5CC Turbidity in wastewater is caused by the presence of
suspended matter such as clay, silt, finely divided
organic and inorganic matter and microscopic or-
ganisms.
END OF ANSWERS TO QUESTIONS IN LESSON 9

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Laboratory 463
OBJECTIVE TEST
Chapter 16. LABORATORY PROCEDURES AND CHEMISTRY
Please write your name and mark the correct answers on the
answer sheet as directed at the end of Chapter 1. There may
be more than one correct answer to each question.
1.	Ambient means a portion of a sample.
1.	True
2.	False
2.	Effluent dissolved oxygen samples should be collected by
the use of a composite sample.
1.	True
2.	False
3.	Effluent temperature samples should be collected by the
use of grab samples.
1.	True
2.	False
4.	Effluent suspended solids samples may be collected any
place in the effluent channel.
1.	True
2.	False
5.	When preparing a composite sample, the individual sam-
ples must be vigorously mixed before the portion for the
composite is withdrawn and then the entire composite
sample should be vigorously mixed.
1.	True
2.	False
6.	The time of day when a sample is collected will affect the
lab results.
1.	True
2.	False
7.	A "Wank" is used in lab tests for comparison purposes.
1.	True
2.	False
8.	DO can be measured by the use of probes connected to
an instrument.
1.	True
2.	False
9.	The treatment plant superintendent is the only person re-
sponsible for lab safety.
1.	True
2.	False
10.	Always wear safety glasses or goggles whenever any
possible danger to your eyes exists.
1.	True
2.	False
11.	Acids can injure you but not bases (hydroxides).
1.	True
2.	False
12.	In the washing of hands after working with wastewater, the
kind of soap is less important than the thorough use of
soap.
1.	True
2.	False
13.	A rubber bulb should be used to pipet wastewater or pol-
luted water.
1.	True
2.	False
14.	Acid may be added to water, but not the reverse.
1.	True
2.	False
15.	The pH scale may range from 0 to 14, with 7 being a
neutral solution.
1.	True
2.	False
16.	A wastewater with a pH of 8.3 is acid.
1.	True
2.	False
17.	End point titration is based on a color change.
1.	True
2.	False
18.	All bottles of chemicals should be clearly labeled.
1.	True
2.	False
19.	If at all possible, samples for the BOD test should be col-
lected before chlorination.
1.	True
2.	False
20.	The COD test is a measure of the chemical oxygen de-
mand of wastewater.
1.	True
2.	False
21.	The BOD test is an indication of the organic content of
wastewater.
1.	True
2.	False
22.	The answers from the total solids and suspended solids
test are always the same.
1.	True
2.	False
23.	The saturation concentration of dissolved oxygen in water
does not vary with temperature.
1.	True
2.	False

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464 Treatment Plants
24.	Always wear safety goggles when conducting any experi-
ment in which there may be danger to the eyes.
1.	True
2.	False
25.	Smoking and eating should be avoided when working with
infectious material such as wastewater and sludge.
1.	True
2.	False
Possible definitions of the words listed below are given on
the right. For each word listed on the left, try to find its definition
on the right. Mark the number of the definition in the answer
column for each word. For example, if the definition of a word is
after the number 2, mark column 2 on your answer sheet after
the word.
Word	Definition
26.	Aliquot	1. Capacity to resist pH change
27.	Ambient	2. Inside
28.	Blank	3. Portion of a sample
29.	Buffer	4. Surrounding
5. Test run without sample
30.	Large errors in laboratory tests may be caused by
1.	Improper sampling.
2.	Lack of mixing during compositing.
3.	Large samples.
4.	Poor preservation.
5.	Poor quality effluent.
31.	A clarity test on plant effluent
1.	Is measured by a Secchi Disc.
2.	is measured by an amperometer.
3.	Should always be measured at the same time.
4.	Should always be measured under the same light con-
ditions.
5.	Tells if the effluent is safe to drink.
32.	Coliform group bacteria are
1.	Harmful to humans.
2.	Indicative of the potential presence of bacteria originat-
ing in the intestines of warm-blooded animals.
3.	Measured by the membrane filter method.
4.	Measured by the Modified Winkler procedure.
5.	Measured by the multiple fermentation technique.
33.	The COD test
1.	Estimates the nitrification oxygen demand only.
2.	Estimates the TOC.
3.	Measures the biochemical oxygen demand.
4.	Measures the carbon oxygen demand.
5.	Provides results quicker than the BOD test.
34. DO probes are commonly used to measure dissolved
oxygen in water in
1.	Aeration tanks.
2.	Anaerobic sludge digesters.
3.	BOD bottles.
4.	Manholes.
5.	Streams.
35.
Hydrogen sulfide
1.	Is formed under aerobic conditions.
2.
3.
Is sometimes written as H2S.
Reacts with moisture and oxygen to form a substance
corrosive to concrete.
4.	Should not be controlled in the collection system.
5.	Smells like rotten eggs.
36.	Hydrogen sulfide gas
1.	Can combine with moisture and be corrosive.
2.	Is flammable and explosive.
3.	Is produced under aerobic conditions.
4.	Is toxic to your respiratory system.
5.	Smells like rotten eggs.
37.	Results from the settleability test of activated sludge solids
may be used to
1.	Calculate mixed liquor suspended solids.
2.	Calculate SDI.
3.	Calculate SVI.
4.	Calculate sludge age.
5.	Determine ability of solids to separate from liquid in
final clarifier.
38.	A chlorine residual should be maintained in a plant effluent
1.	For disinfection purposes.
2.	For testing purposes.
3.	To keep the chlorinator working.
4.	To protect fish in the receiving waters.
5.	To protect the bacteriological quality of the receiving
waters.
39.	Precautions that must be observed in running the sus-
pended solids-Gooch crucible test include
1.	Collecting and testing a representative sample.
2.	Discarding any large chunks of material in sample.
3.	Lack of leaks around and through the glass fiber.
4.	Proper temperature level in oven at all times.
5.	Thoroughly mixing sample before testing.
40.	The most critical factor in controlling digester operation is
the
1.	C02
2.	Gas production.
3.	pH.
4.	Volatile acids/alkalinity relationship.
5.	Volatile solids.

-------
PLANT
Laboratory 465
DATE 	
SUSPENDED SOLIDS & DISSOLVED SOLIDS
SAMPLE




Crucible
Sample, ml
Wt Dry & Dish, gm
Wt Dish, gm
Wt Dry, gm
m0ii = m »y. 9m x 1.000,000
Sample, ml
Wt Dish & Dry, gm
Wt Dish & Ash, gm
Wt Volatile, gm
% Vol = m Vo1 y 100%
Wt Dry




















































BOD
# Blank
SAMPLE			
DO Sample
Bottle #		
% Sample		
Blank or adj blank
DO after incubation		
Depletion, 5 days		
Dep %	
SETTLEABLE SOUDS
Sample, ml		
Direct ml/1			
COD
Sample		
Blank Titration		
Sample Titration		
Depletion			
|r^ _ Dep x N FAS x 8000
Sample, ml		 	
Typical laboratory work sheet

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466 Treatment Plants
TOTAL SOLIDS
SAMPLE		
Dish No.		
Wt Dish & Wet, gm
Wt Dish, gm
Wt Wet, gm		
Wt Dish + Dry, gm
Wt Dish, gm
Wt Dry, gm
% Solids = Wt Dry x 100%
Wt Wet
Wt Dish + Dry, gm
Wt Dish + Ash, gm
Wt Volatile, gm
% Volatile = m VqI x 100%
Wt Dry
PH		
Vol. Acid, mgIL
Alkalinity as CaC03, mg/Z.
Grease
Sample
Sample, ml
Wt Flask + Grease, mg
Wt Flask, mg
Wt Grease, mg
= Wt Grease, mg x 1,000
Sample, ml
Typical laboratory work sheet (continued)

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CHAPTER 17
BASIC ARITHMETIC AND
TREATMENT PLANT PROBLEMS
William Crooks

-------
466 Treatment Plants
TABLE OF CONTENTS
Chapter 17. Basic Arithmetic and Treatment Plant Problems
Page
17.0	How to Study This Chapter	475
17.1	Whole Numbers and Decimals	475
17.10	Addition	475
17.11	Subtraction 	475
17.12	Multiplication	476
17.13	Division 	477
17.2	Fractions	478
17.20	General 	478
17.21	Improper Fractions	478
17.22	Reducing a Fraction to Lowest Terms	478
17.23	Adding and Subtracting 	478
17.24	Multiplication	479
17.25	Division 	479
17.26	Decimal Fractions 	479
17.27	Percentage 	479
17.28	Sample Problems Involving Percent 	480
17.29	Ratio and Proportion	480
17.3	Squares, Cubes, and Roots	481
17.30	Squares and Square Roots	481
17.31	Cubes and Cube Roots 	482
17.4	Mean and Median 	482
17.5	Areas	483
17.50	General 	483
17.51	Rectangle 	483
17.52	Triangle	483
17.53	Circle 	483
17.54	Cylinder	484
17.55	Cone		
17.56	Sphere	485

-------
Arithmetic 469
17.6	Volumes	485
17.60	Rectangle 	485
17.61	Prism 	485
17.62	Cylinder	485
17.63	Cone	485
17.64	Sphere	486
17.7	Metric System	486
17.70	Measures of Length	486
17.71	Measures of Capacity or Volume	486
17.72	Measures of Weight 	486
17.73	Temperature	487
17.74	Milligrams per Liter 	487
17.75	Example Problems	487
17.8	Weight-Volume Relations	488
17.9	Force, Pressure, and Head	488
17.10	Velocity and Flow Rate	489
17.100	Velocity 	489
17.101	Flow Rate 	490
17.11	Pumps 	490
17.110	General 	490
17.111	Work	491
17.112	Power	491
17.113	Horsepower	491
17.114	Head	491
17.115	Pump Characteristics 	492
17.116	Evaluation of Pump Performance	493
17.117	Pump Speed — Performance Relationship 	494
17.118	Friction or Energy Losses 	495
17.12	Steps in Solving Problems	495
17.120	Identification of Problem	495
17.121	Selection of Formula	495
17.122	Arrangment of Formula	498
17.123	Units and Dimensional Analysis	498
17.124	Calculations 	498
17.125	Significant Figures	498
17.126	Check Your Results 	499
17.13	Typical Treatment Plant Problems (English System) 	499
17.130	Grit Channels	499
17.131	Sedimentation Tanks and Clarifiers	499

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470 Treatment Plants
17.132	Trickling Filters	500
17.133	Activated Sludge 	500
17.134	Sludge Digestion 	501
17.135	Ponds	501
17.136	Chlorination	502
17.137	Laboratory Results 	502
17.138	Efficiency of Plant or Treatment Process	502
17.139	Blueprint Reading 	503
17.14	Typical Treatment Plant Problems (Metric System) 	503
17.140	Grit Channels	503
17.141	Sedimentation Tanks and Clarifiers	503
17.142	Trickling Filters	504
17.143	Activated Sludge 	504
17.144	Sludge Digestion 	505
17.145	Ponds	506
17.146	Chlorination	506
17.147	Laboratory Results 	506
17.148	Efficiency of Plant or Treatment Process	507
17.149	Blueprint Reading 	507
17.15	Summary of Formulas (English System)	507
17.150	Length of Clarifier Weir		507
17.151	Area	507
17.152	Volume	507
17.153	Velocity 	507
17.154	Sedimentation Tanks and Clarifiers	507
17.155	Trickling Filters	507
17.156	Activated Sludge	507
17.157	Sludge Digestion	508
17.158	Ponds	508
17.159	Other Formulas 	508
17.1590	Chlorination 	508
17.1591	Laboratory Results	508
17.1592	Efficiency of Plant or Treatment Process	508
17.1593	Pumps	508
17.16	Summary of Formulas (Metric System)	508
17.160	Length of Clarifier Weir	508
17.161	Area		
17.162	Volume		
17.163	Velocity 		

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Arithmetic 471
17.164	Sedimentation Tanks and Clarifiers	508
17.165	Trickling Filters	509
17.166	Activated Sludge 	509
17.167	Sludge Digestion 	509
17.168	Ponds	509
17.169	Other Formulas 	509
17.1690	Chlorination 	509
17.1691	Laboratory Results 	509
17.1692	Efficiency of Plant or Treatment Process	509
17.1693	Pumps	509
17.17	Conversion Tables	509
17.18	Additional Reading	510

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EXPLANATION OF PRE-TEST
This Pre-Test is designed to determine those areas of arith-
metic in which you may need additional help. We suggest that
you work all problems in the Pre-Test and compare your an-
swers with the answers provided. If you do not obtain the an-
swer written beside the problem, turn to the page number in
this chapter which appears directly beside the answer. On this
page you will find an explanation for solving that particular
problem.
If you obtain the correct answer for a problem, you may skip
that section in the chapter. If time is available, however, it may
be worthwhile to at least thumb through that particular section.
If you cannot obtain the given answer, ask a friend to help
you or notify your Program Director. Tell your Program Director
what you tried and what happened, and the Director will try to
help you.
You are not required to mail your calculations or answers for
the Pre-Test to your Program Director; however, if you would
like the Director to review any or all of your work, please mail it
to the Director.
Since the purpose of this chapter is to help you work arith-
metic problems, you are not expected to have memorized for-
mulas and conversion factors (7.5 gal = 1 cu ft). While working
the Pre-Test you may refer to Sections 17.15, Summary of
Formulas, and 17.17, Conversion Tables, for helpful informa-
tion. On many examinations you are expected to have
memorized certain basic formulas and conversion factors. By
working many problems you will gradually memorize this in-
formation.

-------
Arithmetic 473
PRE-TEST
Chapter 17. BASIC ARITHMETIC AND TREATMENT PLANT PROBLEMS
Answer	Page
1.	Add 349 and 75.	424	475
2.	Subtract 296 from 485.	189	475
3.	Multiply 24 x 17.	408	476
4.	Divide 1.25 by 0.045.	27.78	477
5.	Change 13/8 to a mixed number.	1 5/8	478
6.	Reduce 216/324 to its lowest terms.	2/3	478
7.	Add 1/3 + 1/4.	7/12	478
8.	Multiply 2 1/2 by 2/5.	1	479
9.	Divide 5/6 by 3/12.	3 1/3	479
10.	Express 5/6 as a decimal.	0.833	479
11.	Express 2/5 as a percent.	40%	479
12.	Express 0.4% as a fraction.	1/250	479
13.	What percent is 20 of 25?	80%	480
14.	Find 90% of 5.	4.5	480
15.	16 is 80% of what amount?	20	480
16.	Certain bolts cost 90* a dozen. How much would three bolts cost?	23*	480
17.	If three operators can do a certain job in 10 hours, how long would it take 5
operators to do the same job?	6 hrs	481
18.	Find the square root of 20.	4.47	482
19.	Find the cube root of 64.	4	482
20.	Find the arithmetic mean and median of 210, 180, 175, 215, 195, 155, and
200.	190 and 195	482
21.	If the area of a settling basin is 330 square feet and one side measures 15
feet, how long is the other side?	22 ft	483
22.	If the height of a triangle is five feet and the base is four feet, what is the area?	10 sq ft.	483
23.	What is the area of a 20 cm diameter circle?	3l4sqcm	484
24.	What is the total surface area (including side, top, and bottom) of a 60 ft
diameter tank 20 ft high?	9420 sq ft	484
25.	What is the total surface area of a cone with a diameter of 30 inches and
height of 20 inches?	1884 sq in	485
26.	What is the surface area of a 20-foot diameter sphere?	1256 sq ft	485
27.	Find the volume in cubic feet of a box two feet by 15 inches by 18 inches.	3 3/4 cu ft	485
28.	Find the volume of a 100-foot diameter tank, 12 feet deep.	94,200 cu ft	485
29.	Convert 20° centigrade (Celsius) to Fahrenheit.	68°F	487
30.	Convert-13°F to °C.	-25°C	487

-------
474 Treatment Plants
31.	Flow is 3.5 MGD with a BOD level of 200 mgIL. Calculate pounds of BOD per
day.
32.	Change 1000 cu ft of water to gallons.
33.	How many gallons of water weigh 750 lbs?
34.	What is the gage pressure under two feet of water?
35.	What is the force acting on a five feet long wall, four feet deep?
36.	Flow in a 2.5 foot wide channel is 1.4 ft deep and measures 11.2 cfs. What is
the average velocity?
37.	A flow of 500 gpm is pumped 100 ft by a pump with an efficiency of 70%. What
is the pump horsepower?
Answer	Page
5838 lb/day	487
7480 gal	488
90 gal	488
0.866 psi	488
2496 lbs	489
3.2 ft/sec	490
18.0 HP	491

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Arithmetic 475
CHAPTER 17. BASIC ARITHMETIC AND TREATMENT PLANT PROBLEMS
17.0	HOW TO STUDY THIS CHAPTER
This chapter may be worked early in your training program to
help you gain the greatest benefit from your efforts. Whether to
start this chapter early or wait until later is your decision. The
chapters on treatment processes were written in a manner
requiring very little background in arithmetic. You may wish to
concentrate your efforts on the treatment processes and refer
to this chapter when you need help. Some operators prefer to
complete this chapter early so they will not have to worry about
how to do the mathematical manipulations when they are
studying the treatment process lessons. You may try to work
this chapter early or refer to it while studying the other chap-
ters.
The intent of this chapter is to provide you with a quick
review of some basic arithmetic principles and examples of
typical plant problems. It is not intended to be a math textbook.
Some operators will be able to skip over the review of addition,
subtraction, multiplication, and division. Others may need
more help in these and other areas. If you need help in trying to
solve problems, read Section 17.12, "Steps in Solving Prob-
lems." Basic arithmetic textbooks are available at every local
library or bookstore and should be referred to if needed.
When possible, you may wish to perform multiplication and
division with the aid of a slide rule or pocket calculator. Hand-
books frequently have tables containing the square, square
root, and other valuable information which saves computa-
tional time. These methods also are good ways to CHECK
YOUR CALCULATIONS. After you have worked a problem
involving plant operations, you should check your calculations,
examine your answer to see if it appears reasonable, and if
possible have another operator check your work before mak-
ing any operational changes.
17.1	WHOLE NUMBERS AND DECIMALS
17.10 Addition
Not many people will make a mistake when adding 2 plus 2.
However, it is surprising how many cannot correctly add
pp ooo and 0.0022. The reason is they violate one of the main
rules of addition or subtraction, and that is:
1. KEEP ALL DECIMAL POINTS AND NUMBERS IN COL-
UMNS
When the rule is followed correctly, the above addition is
easily performed.
22.222
+ 0.0022
22.2242
Another common error is made in the following manner:
349
+ 75
414 (Wrong)
In this case another rule is violated.
2.	WRITE DOWN ALL CARRYOVER NUMBERS
If this rule is followed, the previous problem becomes:
11
349
+ 75
"424
Carryover numbers should be written lightly over the next
column to the left.
Many can remember a teacher saying to them, "You can't
add apples and oranges." This is our third rule of addition.
3.	ALL NUMBERS MUST BE IN THE SAME DIMENSIONAL
(ft, lb, sec) UNITS
If we needed a string 2 feet long and one 6 inches long, we
would either say:
2 ft + 1/2 ft = 2 1/2 ft of string, or
2 ft
1/2 ft
2 1/2 ft
or we might say:
24 inches + 6 inches = 30 inches of string, or
24 in
6 in
30 in
Two and one-half feet is the same length as 30 inches. We
must use the SAME dimensional units when we add any series
of numbers.
17.11 Subtraction
Since subtraction is simply the reverse of addition, the three
rules for addition generally apply to subtraction:
1. KEEP ALL DECIMAL POINTS AND NUMBERS IN COL-
UMNS
Example: Subtract 0.042 from 3.574.
3.574
-0.042
3.532

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476 Treatment Plants
Since subtraction is the reverse of addition, carryovers are
not made, but "borrowing" is sometimes necessary.
2. WRITE DOWN ALL BORROWED NUMBERS
Example: Subtract 296 from 485.
As before, the numbers should be grouped in columns.
COLUMN LABELS
Hun-


dreds
Tens
Units
4
8
5
1 \
-1
+ 10
3 \

15 ~

*+io_


17

-2
9
6 _
1
8
9
OR
>$5
-296
189
1 st Step — Borrow one from the eight (leaving seven) and
add ten to the five to get 15 — Subtract six from
15 and write down nine.
2nd Step — Borrow one from the four and add ten to the seven
to get 17 — subtract nine from 17 and write down
eight.
3rd Step — Subtract two from three and write down one.
The best way to check a subtraction is by addition. Thus, the
preceding problem can be checked by:
i i
189
+296
485 (Check)
The final rule of subtraction is the same as for addition.
3. ALL NUMBERS MUST BE IN THE SAME DIMENSIONAL
UNITS
17.12 Multiplication
Multiplication is simply a short-cut method of addition. In
other words, 3 x 4 is simply:
or
3 + 3 + 3 + 3 = 12
4 + 4+4 = 12
Thus, a multiplication problem can always be checked by
addition. In the interest of time, however, every operator
should memorize the multiplication table through 10.
Multiplication problems involving larger numbers can be
solved by addition also. For example, 24 x 17 can be solved
by adding a column of seventeen 24's or a column of twenty-
four 17's. This procedure, however, would take considerable
time, and therefore the simple multiplication steps are pre-
ferred.
>
24
xjT7
8
>
24
x 17
168
24
x 17
168
4
1 st Step — 4 x 7 = 28 — write down eight and carry
the two to the next column.
2nd Step — 2 (from 2 in 24) x 7 = 14; 14 + 2 (carried
2) = 16 — write down 16.
3rd Step — Erase all carryovers. 4x1 - 4 write
down four in second row, but ONE PLACE
TO LEFT.
24
x 17
168
24
24
x 17
168
24
408
4th Step — 2x1=2 — write down two.
5th Step — Add numbers.
Another approach to multiplication is the regrouping concept
we illustrated in the subtraction section by placing the number
in the appropriate hundreds (H), tens (T), and units (U) col-
umns. The idea behind this approach is that
10 ones or 10 units (U)
1 ten (T)
= 10
and
10 tens or 10 tens (T) = 1 hundred (H) = 100
PROBLEM: Multiply 24 x 17 or 24
x 17
1st Step 7x4 =
2nd Step 7x2 =
3rd Step 1x4 =
4th Step 1x2 =
5.	Add Columns
6.	Regroup
7.	Answer
H T
2
1 4
10
4 0
28 units or 2T + 8U
unit (7) times Ten (2) makes
right digit (4) go in T column
or 1H + 4T
T x U = the Tens column
T x T = the Hundreds col-
umn
Since 10T = 1H
To multiply numbers, you may use any method that you
understand. These methods are presented to show you differ-
ent approaches used by many operators which give the same
answers.
The first important rule to remember in multiplication is:
1. THE NUMBER OF DECIMAL PLACES IN THE ANSWER
IS EQUAL TO THE SUM OF DECIMAL PLACES IN THE
NUMBERS MULTIPLIED
Example:
14.032
1.03
42096
00000
14032
14.45296
3 decimal places
+ 2 decimal places
5 decimal places
Another way to determine the location of the decimal point is
to multiply the numbers without the numbers past the decimal
point. For example 14 x 1 = 14. Therefore, 14.032 x 1.03
must be equal to more than 14.
A basic difference between addition and multiplication is that
the multiplied numbers do not have to have similar dimensional
units.
2. NUMBERS DO NOT HAVE TO HAVE THE SAME DIMEN-
SIONAL UNITS
For this reason it is important to SPECIFY THE UNITS
THAT GO WITH THE NUMBERS and CARRY THEM
THROUGH to the answer.

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Arithmetic 477
Example: A 20-pound weight on the end of an 8-foot lever
would produce —
20 lbs x 8 ft = 160 ft-lbs
Example: Three operators working five hours each would
put in —
3 operators x 5 hours = 15 operator-hours of labor
The multiplication operation is indicated by several different
symbols. The most common, of course, is the multiplication
sign (x) or times sign. Multiplication also can be indicated by
parentheses ( ) or by brackets [ ] or simply with a dot •
Thus, the above example can be written four ways:
3 operators x 5 hours
(3 operators) (5 hours)
[3 operators] [5 hours]
3 operators - 5 hours
15 operator-hours
15 operator-hours
15 operator-hours
15 operator-hours
When solving a problem with parentheses or brackets, AL-
WAYS complete the indicated operation within the paren-
theses or brackets prior to performing the multiplication.
Example:
Example:
(25 - 4) (8 + 2) (3 • 2)
(21) (10) (6)
21 x 10 x 6
= 1,260
[ 15 -	(3 + 2)
[ 15 - (5)
[15	- 10
[	5
(4-2) ] [ 6 +
(2) ] [ 6 +
] [10
] [10
(7-3) ] =
(4) ] =
] =
] = 50
17.13 Division
Division offers a means of determining how many times one
number is contained in another. It is a series of subtractions.
For example, if we say divide 48 by 12, we are also saying,
how many times can we take 12 away from 48?
By subtraction:
48 - 12= 36 (one)
36 - 12 = 24 (two)
24 - 12 = 12 (three)
12 - 12 = 0 (four)
By division:
12J4S"
4
12)48"
48
1st Step —Twelve will not divide into four, but will
divide into 48 at least four times.
2nd Step — Multiply 4x12 and write answer under 48.
Remainder is zero. Answer is four even.
Division problems can be written in many ways:
2	10* _ ,
5ji6"	10 + 5 = 2 y	10/5 = 2
In each case,
5 = divisor
10 - dividend
2 = quotient
It is always easier to divide by a whole number.
1. MOVE THE DECIMAL POINT OF THE DIVISOR ALL THE
WAY TO THE RIGHT AND THE DECIMAL POINT OF THE
DIVIDEND THE SAME NUMBER OF PLACES TO THE
RIGHT
Example: Divide 1.25 by 0.045.
0.
.04£.JTHp~
45)1250.0
45) 1250.0
90
35
2 .
45)1250.0
90
350
27.
45)1250.0
90
350
27.
45)1250.0
90
1st Step — Move decimal point three places to
right in divisor and dividend. Mark
the decimal location above the divi-
sion sign.
2nd Step — Forty-five will not divide into one or
12, but will go into 125 about two
times.
3rd Step — Multiply 45 by 2 and subtract an-
swer from 125.
4th Step — Bring down zero.
5th Step — Forty-five will go into 350 about
seven times.
6th Step — Multiply 45 by 7 and subtract an-
swer from 350.
350
315
35
27.7
45)1250.0
90
350
315
7th Step — Bring down zero. Once again, 45
will go into 350 about 7 times.
350
If this problem is continued, sevens will continue to show
up in the answer. The answer, then, is 27.777, etc. In most
cases 27.78 will be sufficiently accurate. This is called
"rounding off' the numbers. The last number 7 was in-
creased to 8 because the number after it was 5 or higher.
When solving a division problem, complete the indicated
operations above and below the division line before dividing.
Example:
25 - (2) (3) + 18/2
19 " (3) (4)
25-6 + 9 , 36
(4) (9) _ 5 =
12
19 - 12
2S. + 3-!
7
4 + 3-5
12
* You will encounter this form in Section 17.2 as a fraction.

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478 Treatment Plants
17.2 FRACTIONS
17.20 General
A fraction in its most common form is a part of a whole. For
instance, if a pie is divided into two equal parts and one part is
eaten, only one half of the pie remains.
1/2 + 1/2=1
Thus it can be seen that a fraction is division that has not
been completed. As previously explained, in the fraction 1/2,
one is the dividend and two is the divisor. More commonly,
however, one is called the NUMERATOR and two is called the
DENOMINATOR.
If the pie were divided into eight equal pieces and five were
eaten, we would have less than one half a pie. We would have
3/8 of a pie remaining.
5/8 + 3/8 = 1
17.21 Improper Fractions
An improper fraction has a larger numerator than de-
nominator and is therefore greater than one. An improper frac-
tion may be reduced to a whole or mixed number by dividing
the denominator into the numerator.
Example:
13 (numerator)
8 (denominator)
The reverse of this operation would be changing a whole or
mixed number into a fraction. To accomplish this, the whole
number is multiplied by the denominator, the numerator is
added, and this total is written over the denominator.
Example:	4x2 + 1
2 1/4
4
NOTE: At this point it should be remembered that the
numerator and denominator can be divided or multi-
plied by the same number without changing the value
of the fraction.
Sometimes it will not be possible to reduce the fraction to its
lowest terms with the first trial division. In this case, division
continues until it can no longer be performed by a number
larger than one.
Example:
216 216 + 3
72
72+9
324 324 + 3 108 108 +9
8
12
8+4
12+4
In solving this problem all of these steps could have been
eliminated if we had realized that 108 will divide into the
numerator twice and into the denominator three times. This is
usually difficult to see, however, and smaller numbers must be
used as trial divisors. Again, remember that the numerator and
denominator can be divided or multiplied by the same number
without changing the value of the fraction.
17.23 Adding and Subtracting
Whenever fractions are added or subtracted it is necessary
that the DENOMINATORS BE THE SAME. In adding or sub-
tracting fractions, you simply add or subtract numerators.
Example:
Example:
_	+ _
5	5
7	_ 3
8	8
il
If the denominators are not the same, they must be made
the same before addition or subtraction takes place. In chang-
ing the form of a fraction, the numerator and denominator must
be multiplied by the same number.
Example: z_ + 5^ = 3(2) + 5_=B_+5_=111
5 10 5(2) 10 10 10 lo To
Example:	2(3) _4=6_4 = 2
3
3(3)
9 9
9
8 + 1
In some cases the denominators cannot be changed to one
of the problem's existing denominators. For instance, in adding
1/3 and 1/4, the 1/3 can't be changed to an even fourth, and
the 1/4 can't be changed to an even third. In this case, they
must both be changed to the LEAST COMMON DE-
NOMINATOR. The least common denominator is the smallest
number that each denominator will go into one or more times
without a remainder.
= 9
4
17.22 Reducing a Fraction to Lowest Terms
To change a fraction to its lowest terms, divide the
numerator and denominator by the largest number that will
divide evenly into both.
Example: ^5 _ 15 +15 _ 1_
45 45 + 15 3
Example:
+ _
The lowest number that both 3 and
4 will both go into is 12. Three will
go into twelve 4 times; four will go
into twelve 3 times.
Therefore, the least common denominator is 12. We ob-
tained 12 by multiplying 3x4.
1 x 4
3x4
1 x 3
4x3
12
12
~12

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Arithmetic 479
17.24 Multiplication
Multiply all of the numerators together for a new numerator,
and multiply all of the denominators together for a new de-
nominator. In multiplication, denominators need not be the
same.
Example:
5 + 6
Example:
1x1
10
28
5
14
Before multiplying mixed numbers, change the mixed num-
bers to improper fractions:
Example:
2I
5 x i
12.
10
In some cases a problem can be simplified by dividing (or
cancelling) prior to beginning the multiplication. This operation
also speeds up the process of reducing the answer to its
simplest form. To reduce numbers by cancellation, look for a
number in the numerator and denominator that can be divided
bv the same number.
/ /
Example: JL x A. x JL = J_ <2 goes int0 4 ~ 2 times)
3^ 4^ 5 10 (3 goes into 3 — 1 time)
Example — the same problem without cancellation:
0.833 • • ¦ • (not even)
"6)5.000
48
20
18
To change a decimal to a fraction, multiply the decimal by
10/10, 100/100, 1000/1000, etc. It should be noted that multi-
plying by these factors is multiplying by one (100/100 = 1) and
does not change the value of the answer.
Example: 0 25 x 100 - 25
Example:
0.375 x
100 100
1000 _ 375
1000
1000
15
40
6
60
1
10
Another example of cancellation:
9
f.
17.27 Percentage
Expressing a number in percentage is just another, and
sometimes simpler, way of writing a fraction or a decimal. It
can be thought of as parts per 100 parts, since the percentage
is the numerator of a fraction whose denominator is always
100. Twenty-five parts per 100 parts is more easily recognized
as 25/100 or 0.25. However, it is also 25%. In this case, the
symbol % takes the place of the 100 in the fraction and the
decimal point in the decimal fraction.
For the above example it can be seen that changing from a
fraction or a decimal to percent is not a difficult procedure.
3?
2*. 24.
S
15 (3 goes into 9 and 24) 1. To change a fraction to percent, multiply by 100%.
32 (7 goes into 28 and 35)
Example: _^x 100O/o . 200%
17.25 Division
To divide two fractions, INVERT THE DIVISOR AND MULTI-
PLY.
Example:
x 100% =
5
500%
40%
125%
Example:
Example:
1
JLxJL
1I
2
3
2 1 2
2
5
3
= 5 x nh
10 =
~6~
12
0 3
3
3I
2. To change percent to a fraction, divide by 100%.
1 15 =
100
.4 =
100% 100
Example: 15% + 100% = 15% x_
Example: 0.4% + 100% = 0.4% x_
3
20
4
1000
1
250
17.26 Decimal Fractions
Decimal fractions are fractions which have 10, 100, 1000,
etc., for denominators. They are usually called decimals.
In these examples note that the two percent signs cancel
each other.
Following is a table comparing common fractions, decimal
fractions, and percent to indicate their relationship to each
other:
5
10
15
100
375
= 0.5 = five-tenths
= 0.15 = fifteen-hundredths
1000
375.025
or
25 _ 371; = ,hree hundred seventy-five
and twenty-five thousandths
three hundred seventy-five
point zero two five
To change any fraction to a decimal, divide the numerator by
the denominator.
Example:
1=3 + 4
4
0.750
"4)3.000
28
20
20
Common Fraction
Decimal Fraction
Percent
285
2.85
285%
100


100
1.0
100%
100


20
0.20
20%
100


1
0.01
1%
100


1
0.001
0.1%
1000


1
0.000001
0.0001%
1.000,000



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480 Treatment Plants
17.28 Sample Problems Involving Percent
Problems involving percent are usually not complicated
since their solution consists of only one or two steps. The
principal error made is usually a misplaced decimal point. The
most common type percentage problem is finding:
1.	WHAT PERCENT ONE NUMBER IS OF ANOTHER
In this case, the problem is simply one of reading carefully
to determine the correct fraction and then converting to a
percentage.
Example: What percent is 20 of 25?
20=1= 0.8
25 5
0.8 x 100% = 80%
Example: Four is what percent of 14?
A =0.2857
14
0.2857 x 100%= 28.57%
Example: Influent BOD to a clarifier is 200 mgIL. Effluent
BOD is 140 mg IL. What is the percent removal in
the clarifier? (NOTE: 200-140 = the part re-
moved in the clarifier.)
200 - 140 _ 60 0.30 of the origi-
200 "200" nal ,oad is re"
moved
0.30 x 100% = 30% removal
Therefore % removal = (In - Out) x 1 qo%
In
Another type of percentage problem is finding:
2.	PERCENT OF A GIVEN NUMBER
In this case the percent is expressed as a decimal, and the
two numbers are multiplied together.
Example: Find 7% of 32.
0.07 x 32 = 2.24
Example: Find 90% of 5.
.90 x 5 = 4.5
Example: What is the weight of dry solids in a ton (2000 lbs)
of wastewater sludge containing 5% solids and
95% water?
NOTE: 5% solids means there are 5 lbs of dry
solids for every 100 lbs of wet sludge.
Therefore
2000 lbs x 0.05 = 100 lbs of solids
A variation of the preceding problem is:
3.	FINDING A NUMBER WHEN A GIVEN PERCENT OF IT IS
KNOWN
Since this problem is similar to the previous problem, the
solution is to convert to a decimal and divide by the decimal.
Example: If 5% of a number is 52, what is the number?
= 1040
0.05
A check calculation may now be performed —
what is 5% of 1040?
0.05 x 1040 = 52 (Check)
Example: 16 is 80% of what amount?
= 20
0.80
Example: Percent removal of BOD in a clarifier is 35%. If 70
mg IL are removed, what is the influent BOD?
Influent BOD = _70 = 200 mg/L
0.35
Check:
Original load x % removal = load removed
200 mgIL x 0.35 = 70 mg IL
17.29 Ratio and Proportion
RATIO is the comparison of two numbers of the same de-
nomination. For example, 1 inch compared to 3 inches, or 3
boxes compared to 7 boxes. Ratios are written either as frac-
tions, 1/3, or as 1:3 (which is read "the ratio of one to three").
PROPORTION is the equating of ratios. For example, 3/6 is
equal to 1/2. A proportion is usually written in the form a/b =
c/d, or a:b = c:d (which is read as a is to b as c is to d).
To solve the proportion a/b = c/d, we multiply diagonally
across:
Therefore, a x d = b x c. This procedure is sometimes
called CROSS multiplication.
This can be proved by substituting the previous example:
3 = 1
6 2
3x2=6x1
6 = 6
When one complete ratio is known and one term of the
second ratio is known, the proportion relationship indicates
what the unknown number should be.
For instance, if one number from the previous example were
missing, the number could be found by cross multiplying.
a _ 1
6 2
a x 2 = 6 xl
a x 2 .6x1	Divide both sides
2 2	of equation by 2.
2
= 6
2
= 3
A few example problems should indicate how to deal with
ratios and proportions.

-------
Arithmetic 481
Example: Certain bolts cost 90 cents a dozen. How much
would three bolts cost?
In setting up this proportion, we would say: 12 bolts
cost 90 cents; 3 bolts cost x cents. Therefore, the
proportion is written either as 12/3 = 90Ix or 12/90 =
3/x.
= _
90 x
12 x x = 90 x 3
x = 90 x 3*
V *
= ^9-
4
= 22 1/2 or 23< (to the nearest penny)
Example: If 3 lbs of salt are added to 10 gallons of water to
make a solution of a given strength, how many
pounds would be added to 129 gallons to make a
solution of the same concentration?
3 lbs = x
10 gal 129 gal
x (10 gal) = 3 lbs (129 gal)
x = 3 lbs (129 8*1)
10 gal
= 387 lbs
10
= 38.7 lbs
NOTE: Gallons in the numerator and gallons in the de-
nominator can be canceled without changing the value
of the solution.
Although proportions are usually not difficult to solve, some
care must be taken when using them. Some varying quantities
are INVERSELY PROPORTIONAL to each other. Their prod-
ucts, rather than their ratios, are constant. This can be easily
explained by an example.
Example: If three operators can do a certain job in 10 hours,
how long would it take five operators to do the same
job?
This problem is inversely proportional. If this fact
were not noticed, many would solve it by direct pro-
portion.
3 operators _ 5 operators
10 hours	x hrs
x = 5 0PflOX X 10 hrs
Z9W&W*
_ 50 hrs
3
= 16 2/3 hrs (Wrong)
The solution is wrong since INCREASING THE
OPERATORS should DECREASE THE TIME re-
quired to do the job. The problem is therefore in-
versely proportional and the products of the varying
quantities should be equated.
3 operators x 10 hours = 5 operators (x hrs)
x = 3 ppyntyg x 10 hrs
5 0p«itmm
= 6 hrs
It is important for the operator to remember that gas
pressure-volume problems are also inversely proportional. The
higher the pressure, the smaller the volume of gas.
Example: A vessel contains 100 cubic feet of gas at 5 lbs per
square inch pressure. What is the pressure if the
volume is reduced to 40 cubic feet?
100 cu ft x 5 psi = 40 cu ft (x psi)
_ 100 x Spsi
40 0*/#
_ 500 psi
40
= 12.5 psi
NOTE: In this problem the temperature was assumed to re-
main constant. Gas pressures are given in psi absolute
values (see Section 17.110 on page 490).
17.3 SQUARES, CUBES, AND ROOTS
17.30 Squares and Square Roots
Squaring a number simply means multiplying a number by
itself. For instance, in squaring two we obtain four (2x2 = 4).
In squaring three, the answer is nine. A short way of writing 2 x
2 is by using the superscript 2 in the following manner, 2^
Thus, if we were trying to indicate the squaring of numbers we
would write:
12 = 1
2* = 4
3* = 9
42 = 16
52 = 25, and so on
A reverse of this process is to take a number that has been
squared and find the number which was multiplied by itself to
form the square. This process is called finding the square root.
The sign V indicates square root. The square root of 4 is
written, V4~, and the answer is 2. The reverse of the previous
column would then be:
V~T = 1
V~4~ = 2
V~9~ = 3
V~16 = 4
V 25 = 5, and so on
A difficulty arises when the square root of a number does not
result in a whole number. Such is the case for V20. Since the
Vl6 is 4, and the V25 is 5, the answer is between 4 and 5.
Two solutions are available to the operator who does not pos-
sess a pocket calculator, slide rule, table of square roots, or a
logarithm table. One method is an exact method which is simi-
lar to a long division problem. For this method, the operator
must refer to a mathematical textbook or page 539 in Chapter
18. Quite frankly, this method is cumbersome and difficult to
remember if you do not work with it frequently.
The other method is a trial and error method. This method is
shown here because it is a method which will enable you to
find the solution of square root problems using only the knowl-
edge of multiplication.

-------
482 Treatment Plants
Example: Find the square root of 20.
As previously discussed, the answer is between 4
and 5. Therefore, simply guess a number and
square it.
Assume 4.3:
4.3 x 4.3 = 18.49
4.3
4.3
129
172
18.49
Next assume 4.4:
4.4 x 4.4 = 19.36
Since (4.4)2 is close to 20, next try 4.44 (these num-
bers are picked because they are quickly multiplied).
4.44 x 4.44 = 19.7136
Next assume 4.46:
4.46	X 4.46 = 19.8916
Next assume 4.47:
4.47	x 4.47 = 19.9809
For most purposes, 4.47 would be sufficiently close
to use as the answer.
For most numbers the trial and error solution takes more
time than the exact solution. Its advantage is that it requires no
memorized steps for solution, except multiplication.
17.31 Cubes and Cube Roots
Multiplying a number by itself twice results in the cube of the
number. For example, the cube of 2 is 2 x 2 x 2 = 23, or 8.
The cube of a number is indicated by a superscript 3.
13	=	1
23	=	8
33	=	27
43	=	64
53	=	125, and so on
The reverse of this process is to take the cube root of a
number
The sign ^ indicates cube root.
>Ti25 = 5
>T~64 = 4
>T"27 =
^8 =
>TF =
Cube roots can be found by methods similar to those dis-
cussed for square roots. The operator does not usually come
in contact with many problems involving cubes or cube roots.
A rather simple solution for square roots and cube roots is by
use of logarithms. The only mathematical step involved is divi-
sion by 2 or 3. The only disadvantage is that you must have a
logarithm table handy. Since logarithms also offer a quick
means of multiplying large numbers, it is suggested that the
operator become familiar with them and keep a "log" table
handy at your desk. Directions for using logarithms are found
in math textbooks and in Chapter 18, section 18.71,
"Logarithms," pages 523 and 524.
If at all possible, you should obtain a pocket calculator and
learn how to use it. This is the best way to solve these types of
problems.
17.4 MEAN AND MEDIAN
Computing an average from a set of data offers a way of
simplifying the data or comparing one set of data with another.
If an average value is computed by adding a series of items
and then dividing the total by the number of items, the result is
called an ARITHMETIC MEAN.
Example: Influent BODs at a treatment plant are determined
every day. The following composite values were ob-
tained during one week: 210, 180, 175, 215, 195,
155, and 200. What is the arithmetic mean for the
week?
Average = Sum of items or values
Number of items or values
_ 210+180+175+215+195+155+200
7
= 190 mgIL
210
180
175
215
195
155
200
1330
190
7)1330
7
63
_63
Weekly average or mean BOD = 190 mg/i.	^
Another arithmetic tool to analyze a set of data is the ME-
DIAN. The median in a set of data is the middle value. There
are just as many values above a median as there are below.
To determine the median, the data should be written in as-
cending or descending order and the middle value identified.
Example: What is the median BOD in the preceding problem?
215
210
200
195 — Median
180
175
155
Weekly median BOD = 195 mg/L
Median coliform numbers are sometimes used as a standard
by regulatory agencies to avoid allowing too much weight to
large coliform values.
Example: Five days of sampling resulted in most probable
number (MPN) of coliform group bacteria per 100 ml
of 23,5,2,2300, and 16. Find the mean and median
coliform content.
Mean
Sum of values
Number of values
Mean MPN/100 ml = 23 +5 +24,2300+16
5
= 2346
5
Mean MPN/100 ml = 469 conforms
Median MPN/100 ml = 16 conforms
2300
23
16
5
	2
2346

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Arithmetic 483
The above example indicates that the median value com-
pletely eliminates the effect of the one large sample, while the
mean value is affected a great deal. Most agencies feel that
the minimum and maximum values of a group of data should
always be stated along with a mean or median. The difference
between the maximum and minimum values is called the
range.
Chapter 18, "Analysis and Presentation of Data," contains
more information on how to calculate averages. Types of aver-
ages discussed include the arithmetic mean, median, mode,
and geometric mean.
17.5 AREAS
17.50	General
Areas are measured in two dimensions or in square units. In
the English system of measurement the most common units
are square inches, square feet, square yards, and square
miles. In the metric system the units are square millimeters,
square centimeters, square meters, and square kilometers.
17.51	Rectangle
The area of a rectangle is equal to its length (L) multiplied by
its width (W).
Example: Find the area of triangle ABC:
T
w
±
A = L X W
k-
Example: Find the area of a rectangle if the length is 5 feet
and the width is 3.5 feet.
Area, sq ft = Length, ft x Width, ft
= 5 ft x 3.5 ft
= 17.5 ft2
= 17.5 sq ft
Example: The surface area of a settling basin is 330 square
feet. One side measures 15 feet. How long is the
other side?
A = L x w
330 sq ft = L ft x 15 ft
L ft x 15 ft _ 330 ft2 Divide both sides of equation by 15 ft.
15ft
L ft =
15ft
330 ft2
15ft
22 ft
17.52 Triangle
The area of a triangle is equal to one half the base multiplied
by the height. This is true for any triangle.
A = V4B x H
NOTE: The area of ANY triangle is equal to Vt the area of the
rectangle that can be drawn around it. The area of the
rectangle is B x H. The area of the triangle is Vi B x H.
T
48 in.
A
The first step in the solution is to make all the units
the same. In this case, it is easier to change inches
to feet.
48 in = 48/I pi x 1	ft = 4 ft
12/ipi 12
NOTE: All conversions should be calculated in the above
manner. Since 1 ft/12 in is equal to unity, or one, multi-
plying by this factor changes the form of the answer
but not its value.
Area, sq ft = Vi (Base, ft) (Height, ft)
= Vi x 5ft x 4ft
= 10 sq ft
NOTE: Triangle ABC is one half the area of rectangle ABCD.
The triangle is a special form called a RIGHT
TRIANGLE since it contains a 90° angle at point B.
17.53 Circle
A square with sides of 2R can be drawn around a circle with
a radious of R.
I
The area of the square is: A = 2R x 2R = 4R2.
It has been found that the area of any circle inscribed within
a square is slightly more than % of the area of the square.
More precisely, the area of the preceding circle is:
A circle = 31R8 = 3.14 R2
7
The formula for the area of a circle is usually written:
A = 7rR2
The Greek letter w (pronounced pie) merely substitutes for
the value 3.1416.
Since the diameter of any circle is equal to twice the radius,
the formula for the area of a circle can be rewritten as follows:
A « jtR* = it x R x R
jt x 2 x 5 = £5L = Mi D* =
2 2 4 4
0.785 D2

-------
484 Treatment Plants
The type of problem and the magnitude of the numbers in a
problem will determine which of the two formulas will provide a
simpler solution. All of these formulas will give the same results
if you use the same number of digits to the right of the decimal
point.
Example: What is the area of a circle with a diameter of 20
centimeters?
In this case, the formula using a radius is more con-
venient since it takes advantage of multiplying by
10.
Area, sq cm = ir (R, cm)2
= 3.14 x 10 cm x 10 cm
= 314 sq cm
Example: What is the area of a trickling filter with a 50-foot
radius?
In this case, the formula using diameter is more
convenient.
Area, sq ft = 0.785 (Diameter, ft)2
= 0.785 x 100 ft x 100 ft
= 7850 sq ft
Occasionally the operator may be confronted with a problem
giving the area and requesting the radius or diameter. This
presents the special problem of finding the square root of the
number.
Example: The surface area of a circular clarifier is approxi-
mately 5000 square feet. What is the diameter?
A = 0.785 D2, or
Area, sq ft = 0.785 (Diameter, ft)2
5000 sq ft = 0.785 D2 — To solve, substitute given values in
equation.
0.785 D2 _ 5000 sq ft — Divide both sides by 0.785 to find D2.
0.785 0.785
Q2 _ 5000 sq ft
0.785
= 6369 sq ft. Therefore,
0 = square root of 6369 sq ft, or
Diameter, ft = V6369 sq ft
As previously mentioned, it is sometimes easier to use a trial
and error method of finding square roots. Since 80 x 80 =
6400, we know the answer is close to 80 feet.
Try 79 x 79 = 6241
Try 79.5 x 79.5 = 6320.25
Try 79.8 x 79.8 = 6368.04
The diameter is 79.8 ft, or approximately 80 feet.
17.54 Cylinder
With the formulas presented thus far, it would be a simple
matter to find the number of square feet in a room that was to
be painted. The length of each wall would be added together
and then multiplied by the height of the wall. This would give
the surface area of the walls (minus any area for doors and
windows). The ceiling area would be found by multiplying
length times width and the result added to the wall area gives
the total area.
The surface area of a circular cylinder, however, has not
been discussed. If we wanted to know how many square feet
of surface area are in a tank with a diameter of 60 feet and a
height of 20 feet, we could start with the top and bottom.
/

60 ft
J
20 ft
1
The area of the top and bottom ends are both v x R2
Area, sq ft = 2 ends (ir)(Radius, ft)2
= 2 x TT x (30 ft)2
= 5652 sq ft
The surface area of the wall must now be calculated. If we
made a vertical cut in the wall and unrolled it, the straightened
wall would be the same length as the circumference of the floor
and ceiling.
	(Circumference = n x~D|	
20 ft


This length has been found to always be it x D. In the
of the tank, the length of the wall would be:
Length, ft
Area would be:
A*, sqft
= (ir) (Diameter, ft)
= 3.14 x 60 ft
= 188.4 ft
= Length, ft x Height, ft
= 188.4 ft x 20 ft
= 3768 sq ft
Outside Surface Area
to Paint, sq ft	= Area of top and bottom, sq ft
+ Area of wall, sq ft
= 5652 sq ft + 3768 sq ft
= 9420 sq ft
A container has inside and outside surfaces and you may
need to paint both ol them.
17.55 Cone

-------
Arithmetic 485
The lateral area of a cone is equal to Vz of the slant height (S)
multiplied by the circumference of the base.
AL = 1/2Sx77xD = 7rxSxR
In the case the slant height is not given, it may be calculated
by:
S = VR2 + H2
Example: Find the entire outside area of a cone with a diame-
ter of 30 inches and a height of 20 inches.
Slant Height, in = V(Radius, in)2 + (Height, in)2
= V(15in)2 + (20 in)2
= V225 in2 + 400 in2
Area of
Cone, sq in
= V625 in2
= 25 in
= 77 (Slant Height, in) (Radius, in)
= 3.14 x 25 in x 15 in
= 1177.5 sq in
Since the entire area was asked for, the area of
the base must be added.
Area, sq in
Total Area,
sq in
17.56 Sphere
= 0.785 (Diameter, in)2
= 0.785 x 30 in x 30 in
= 706.5 sq in
=Area of Cone, sq in +
Area of Bottom, sq in
= 1177.5 sq in + 706.5 sq in
= 1884 sq in
The surface area of a sphere or
ball is equal to v multiplied by the
diameter squared.
As = wD2
If the radius is used, the formula
becomes:
Ag = 7tD2 = 7r x 2R x 2R = 4irR2
Example: What is the surface area of a sphere shaped
methane gas container 20 feet in diameter?
Area, sq ft = n (Diameter, ft)2
= 3.14 x 20 ft x 20 ft
= 1256 sq ft
17.6 VOLUMES
17.60 Rectangle
Volumes are measured in three dimensions or in cubic units.
To calculate the volume of a rectangle, the area of the base is
calculated in square units and then multiplied by the height.
The formula then becomes:
Example: The length of a box is two feet, the width is 15
inches, and the height is 18 inches. Find its volume.
Volume, cu ft = Length, ft x Width, ft x Height, ft
= 2ftx 1 JL ft x lift
4 2
= 2ftxiftx?_ft
4 2
= cu ft
4
= 3 1 cu ft
4
17.61 Prism
The same general rule that applies to a rectangle also
applies to a prism.
Volume = Area of Base x Height
Example: Find the volume of a prism with a base area of 10
square feet and a height of 5 feet. (Note that the
base of a prism is triangular in shape.)
Volume, cu ft = Area of Base, sq ft x Height, ft
= 10 sq ft x 5ft
= 50 cu ft
17.62 Cylinder
The volume of a cylinder is equal to the area of the base
multiplied by the height.
V = irR2 x H = 0.785 D2 x H
¦D-H
T
H
Example: A primary clarifier has a diameter of 100 feet and a
depth of 12 feet. Find the volume.
Volume, cu ft = 0.785 x (Diameter, ft)2 x Height, ft
= 0.785 x 100 ft x 100 ft x 12 ft
= 94,200 cu ft
17.63 Cone
The volume of a cone is equal to Vb the volume of a circular
cylinder of the same height and diameter.
v = I R» x H
3
U-R-J

-------
486 Treatment Plants
Example: Calculate the additional volume in the cone portion
of the clarifier in Section 17.62 if the depth at the
center of the clarifier is 16 ft. H = 16 ft - 12 ft.
Volume, cu ft = 2L x (Radius)2 x Height, ft
3
= Zx50ftx50ftx4ft
3
= 10,500 cu ft
17.64 Sphere
The volume of a sphere is equal to W6 times the diameter
cubed.
Example: How much gas can be stored in a sphere with a
diameter of 12 feet? (Assume atmospheric pres-
sure.)
Volume, cu ft = JL x (Diameter, ft)3
6
= 72 ft x 12 ft x 12 ft
0
= 904.32 cubic feet
17.7 METRIC SYSTEM
The two most common systems of weights and measures
are the English system and the Metric system. Of these two,
the Metric system is more popular with most of the nations of
the world. The reason for this is that the Metric system is based
on a system of tens and is therefore easier to remember and
easier to use than the English system. Even though the basic
system in the United States is the English system, the scientific
community uses the Metric system almost exclusively. Many
organizations have urged, for good reason, that the United
States switch to the Metric system. Today the Metric system is
gradually becoming the standard system of measurement in
the United States.
As the United States changes from the English to the Metric
system, some confusion and controversy has developed. For
example, which is the correct spelling of the following words:
1.	Liter or litre?
2.	Meter or metre?
The U.S. National Bureau of Standards, the Water Pollution
Control Federation, and the American Water Works Associa-
tion use litre and metre. The U.S. Government uses liter and
meter and accepts no deviations. Some people argue that
METRE should be used to measure LENGTH and that METER
should be used to measure FLOW RATES (like a water or
electric meter). Liter and meter are used in this manual be-
cause this is a publication of the U.S. Government.
One of the most frequent arguments heard against the U.S.
switching to the Metric system was that the costs of switching
manufacturing processes would be excessive. Pipe manufac-
turers have agreed upon the use of a "soft" metric conversion
system during the conversion to the Metric system. Past prac-
tice in the U.S. has identified some types of pipe by external
(outside) diameter while other types are classified by nominal
(existing only in name, not real or actual) bore. This means that
a six-inch pipe does not have a six-inch inside diameter. With
the strict or "hard" metric system, a six-inch pipe would be a
152.4 mm (6 in x 25.4 mm/in) pipe. In the "soft" metric system
a six-inch pipe is a 150 mm (6 in x 25 mm/in) pipe. Typical
customary and "soft" metric pipe-size designations are shown
below:
PIPE-SIZE DESIGNATIONS
Customary, in
"Soft" Metric, mm
Customary, in
"Soft" Metric, mm
2 4 6
50 100 150
8
200
10
250
12
300
15
375
18
450
24 30 36 42 48 60 72 84
600 750 900 1050 1200 1500 1800 2100
In order to study the Metric system, you must know the
meanings of the terminology used. Following is a list of Greek
and Latin prefixes used in the Metric system.
PREFIXES USED IN THE METRIC SYSTEM
Prefixes
Symbol
Meaning
Micro
M-
1/1 000 000 or 0.000 001
Milli
m
1/1000 or 0.001
Centi
c
1/100 or 0.01
Deci
d
1/10 or 0.1
Unit

1
Deka
da
10
Hecto
h
100
Kilo
k
1000
Mega
M
1 000 000
17.70 Measures of Length
The basic measure of length is the meter.
1 kilometer (km)
1 meter (m)
1 centimeter (cm)
1000 meters (m)
100 centimeters (cm)
10 millimeters (mm)
Kilometers are usually used in place of miles, meters are
used in place of feet and yards, centimeters are used in place
of inches, and millimeters are used for inches and fractions of
an inch.
LENGTH EQUIVALENTS
1 kilometer
1 meter
1 meter
1 centimeter
1 millimeter
0.621 mile
3.28 feet
39.37 inches
0.3937 inch
0.0394 inch
1	mile	=
1	foot	=
1	inch	=
1	inch	=
1	inch	=
1.64 kilometers
0.305 meter
0.0254 meter
2.54 centimeters
25.4 millimeters
NOTE: The above equivalents are reciprocals. If one equiva-
lent is given, the reverse can be obtained by division.
For instance, if one meter equals 3.28 feet, one foot
equals 1/3.28 meter, or 0.305 meter.
17.71	Measures of Capacity or Volume
The basic measure of capacity in the Metric system is the
liter. For measurement of large quantities the cubic meter is
sometimes used.
1 kiloliter (kl) = 1000 liters (L) = 1 cu meter (m3)
1 liter (L) = 1000 milliliters (ml)
Kiloliters, or cubic meters, are used to measure capacity of
large storage tanks or reservoirs in place of cubic feet or gal-
lons. Liters are used in place of gallons or quarts. Milliliters are
used in place of quarts, pints, or ounces.
CAPACITY EQUIVALENTS
1 kiloliter = 264.2 gallons	1 gallon = 0.003785 kiloliter
1 liter = 1.057 quarts
1 liter = 0.2642 gallon
1 milliliter ~ 0.0353 ounce
17.72	Measures of Weight
The basic unit of weight in the Metric system is the gram.
One cubic centimeter of water at maximum density weighs one
1 quart = 0.946 liter
1 gallon = 3.785 liters
1 ounce = 29.57 milliliters

-------
Arithmetic 487
gram, and thus there is a direct, simple relation between vol-
ume of water and weight in the Metric system.
1 kilogram (kg) = 1000 grams (gm)
1 gram (gm) = 1000 milligrams (mg)
1 milligram (mg) = 1000 micrograms (#tg)
Grams are usually used in place of ounces, and kilograms
are used in place of pounds.
WEIGHT EQUIVALENTS
1 pound = 0.4536 kilogram
1 pound = 453.6 grams
1 ounce = 28.35 grams
1 grain = 0.0648 gram
1 kilogram = 2.205 pounds
1 gram = 0.0022 pound
1 gram = 0.0353 ounce
1 gram =15.43 grains
17.73 Temperature
Just as the operator should become familiar with the Metric
system, you should also become familiar with the centigrade
(Celsius) scale for measuring temperature. There is nothing
magical about the centrigrade scale — it is simply a different
size than the Fahrenheit scale. The two scales compare as
follows:
Fahrenheit	Celsius
212°F
Water Boils
100°C
32°F
0°F
0
Water Freezes o°C
-17.8°C
o
The two scales are related in the following manner:
Fahrenheit
Celsius
(°C x 9/5) + 32°
(°F - 32°) x 5/9
Example: Convert 20° Celsius to Fahrenheit.
F = (°C x 9/5) + 32°
F = (20° x 9/5) + 32°
F = 180° + 32°
= 5
= 36° + 32°
= 68°F
Example: Convert -10°C to °F.
F = (-10° x 9/5) + 32°
F = -9075 + 32°
= -18° + 32°
= 14°F
Example: Convert -13°F to °C.
C = (°F - 32°) x 5
9
C = (-13° - 32°) x 1
9
C = -45° x .
9
C = -5° x 5
C = -25°C
17.74 Milligrams per Liter
Milligrams per liter (mgIL) is a unit of measurement used in
laboratory and scientific work to indicate very small concentra-
tions or dilutions. Since wastewater contains small concentra-
tions of dissolved substances and solids, and since small
amounts of chemical compounds are sometimes used in
wastewater treatment processes, the term milligrams per liter
is also common in treatment plants. It is a weight/volume rela-
tionship.
As previously discussed:
1000 liters = 1 cubic meter = 1,000,000 cubic centimeters
Therefore
1 liter = 1000 cubic centimeters
Since one cubic centimeter of water weighs one gram,
1 liter of water = 1000 grams or 1,000,000 milligrams
1 milligram _ 1 milligram _ 1 part _ 1 part per
liter 1,000,000 milligrams million parts m'"'on (PPm)
Milligrams per liter and parts per million (parts) may be used
interchangeably as long as the liquid density is 1.0 gm/cu cm
or 62.43 Ib/cu ft. A concentration of 1 milligram/liter (mgIL) or 1
ppm means that there is 1 part of substance by weight for
every 1 million parts of water. A concentration of 10 mgIL
would mean 10 parts of substance per million parts of water.
To get an idea of how small 1 mgIL is, divide the numerator
and denominator of the fraction by 10,000. This, of course,
does not change its value since, 10,000 + 10,000 is equal to
one.
1 mg
1 mg = 	 	 	
L 1,000,000 mg 1,000,000/10,000 mg 100 mg
1/10,000 mg = 0.0001 mg = q.0001%
Therefore, 1 mgIL is equal to one ten-thousandth of a per-
cent, or
1% is equal to 10,000 mgIL
To convert mg/L to %, move the decimal point four places or
numbers to the left.
Working problems using milligrams per liter or parts per mil-
lion is a part of everyday operation in most wastewater treat-
ment plants.
17.75 Example Problems
Example: A plant effluent flowing at a rate of five million
pounds per day contains 15 mgIL of solids. How
many pounds of solids will be discharged per day?
15 mg/L =
15 lbs solids
million lbs water
Solids
Discharged, = Concentration, Ibs/M lbs x Flow, lbs/day
lbs/day
: 15 lbs
75 lbs/day
5 tun
day
There is one thing that is unusual about the above problem
and that is the flow is reported in pounds per day. In most
treatment plants, flow is reported in terms of gallons per minute
or gallons per day. To convert these flow figures to weight, an
additional conversion factor is needed. It has been found that
one gallon of water (and wastewater, since it is almost all

-------
488 Treatment Plants
water) weighs 8.34 pounds. Using this factor, it is possible to
convert flow in gallons per day to flow in pounds per day.
Example: A plant influent of 3.5 million gallons per day (MGD)
contains 200 mg/L BOD. How many pounds of BOD
enter the plant per day?
Flow, lbs/day = Flow, M gal x
day
3.5 million gal
8.34 lb
gal
„ 8.34 lbs
day	gat
= 29.19 million lbs/day
j Loading, = Leve| mg//_ x Flow, M lb/day
lbs/day
= 200 mg' x
pWpfrng
= 5838 lbs/day
29.19 ptHMW lbs
day
In solving the above problem, a relation was used that is
most important to understand and commit to memory.
Lbs/day = Cone., mg/L x Flow, MGD x 8.34 lb/gal
Example: A chlorinator is set to feed 50 pounds of chlorine per
day to a flow of 0.8 MGD. What is the chlorine dose
in mg/L?
Cone, or Dose,
mg/L
lbs/day
MGD x 8.34 lb/gal
50 lb/day
0.80 MG/day x 8.34 lb/gal
50 lb
6.672 M lb
= 7.5 mg/Z., or 7.5 ppm
Example: Treated effluent is pumped to a spray disposal field
by a pump that delivers 500 gallons per minute.
Suspended solids in the effluent average 10 mg/L.
What is the total weight of suspended solids de-
posited on the spray field during a 24-hour day of
continuous pumping?
Flow, MGD
= Flow, gpm x 60 min/hr x 24 hr/day
= 500 gal y 60 nHp y 24 hr
nftffl Iv
720,000 gal/day
0.72 MGD
day
Weight of
Solids,
lbs/day
Cone.,mg/L x Flow.MGDx8.34 lb/gal
10 rug 0.72
	8.34 lb
M wg	day
= 60.248 lbs/day or about 60 lbs/day
17.8 WEIGHT-VOLUME RELATIONS
Another factor for the operator to remember, in addition to
the weight of a gallon of water, is the weight of a cubic foot of
water. One cubic foot of water weighs 62.4 lbs. If these two
weights are divided, it is possible to determine the number of
gallons in a cubic foot.
62.4 pOMPdg/cu ft = 7 48 ga|/cu ft
8.34 p00P(2l3/gal
* Remember that 1 mg _ 1 lb. They are identical ratios.
M mg M lb
Thus we have another very important relation to commit to
memory.
8.34 lb/gal x 7.48 gal/cu ft = 62.4 Ib/cu ft
It is only necessary to remember two of the above items
since the third may be found by calculation. For most prob-
lems, 8 1/3 lbs/gal and 7 1/2 gal/cu ft will provide sufficient
accuracy.
Example: Change 1000 cu ft of water to gallons.
1000 cu ft x 7.48 gal/cu ft = 7480 gallons
Example: What is the weight of three cubic feet of water?
62.4 Ib/cu ft x 3 cu ft = 187.2 lbs
Example: The net weight of a tank of water is 750 lbs. How
many gallons does it contain?
750^ = 750gal3gggaly 3 =Qnjfl|s
8 1/3/lb/gal 25/3	1 20,
17.9 FORCE, PRESSURE, AND HEAD
In order to study the forces and pressures involved in fluid
flow, it is first necessary to define the terms used.
FORCE: The push exerted by water on any surface being
used to confine it. Force is usually expressed in
pounds, tons, grams, or kilograms.
PRESSURE: The force per unit area. Pressure can be ex-
pressed in many ways, but the most common
term is pounds per square inch (psi).
HEAD: Vertical distance from the water surface to a ref-
erence point below the surface. Usually ex-
pressed in feet or meters.
An EXAMPLE should serve to illustrate these terms.
If water were poured into a one-foot cubical container, the
FORCE acting on the bottom of the container would be 62.4
pounds.
The PRESSURE acting on the bottom would be 62.4 pounds
per square foot. The area of the bottom is also 12 in x 12 in =
144 in . Therefore, the pressure may also be expressed as:
Pressure, psi	= ^ = 62.4 Ib/sq ft
sq ft 144 sq in/sq ft
= 0.433 Ib/sq in
= 0.433 psi
Since the height of the container is one foot, the HEAD
would be one foot.

-------
Arithmetic 489
The pressure in any vessel at one foot of depth or one foot of
head is 0.433 psi acting in any direction.
^7

o
t
1 ft
Y 0.433
psi

If the depth of water in the previous example were increased
to two feet, the pressure would be:
P =
2 (62.4 lb)
144 sq in
124.8 lb
144 sq in
= 0.866 psi
Therefore we can see that for every foot of head, the pres-
sure increases by 0.433 psi. Thus, the general formula for
pressure becomes:
H = feet of head
p = pounds per square INCH of
pressure
p, psi = 0.433 (H, ft)
P, Ib/sq ft = 62.4 (H, ft)
H = feet of head
P = pounds per square FOOT
of pressure
We can now draw a diagram of the pressure acting on the
side of a tank. Assume a four-foot deep tank. The pressures
shown on the tank are gage pressures. These pressures do
not include the atmospheric pressure acting on the surface of
the water.



0.4334)si_^

62K4 psf

/^ 12468 psf

1.299 DSi

187.2 psf
/
1.732 psi ,
249.6 psf
p° = 0.433 x 0 = 0.0 psi
p, = 0.433 x 1 = 0.433 psi
P2 = 0.433 x 2 = 0.866 psi
p3 = 0.433 x 3 = 1.299 psi
p« = 0.433 x 4 = 1.732 psi
Po = 62.4 x 0 = 0.0 Ib/sq ft
P. = 62.4 x 1 = 62.4 Ib/sq ft
Ps = 62.4 x 2 = 124.8 Ib/sq ft
P3 = 62.4 x 3 = 187.2 Ib/sq ft
P4 = 62.4 x 4 = 249.6 Ib/sq ft
The average PRESSURE acting on the tank wall is 1.732
psi/2 = 0.866 psi, or 249.6 psf/2 = 124.8 psf. We divided by
two to obtain the average pressure because there is zero pres-
sure at the top and 1.732 psi pressure on the bottom of the
wall.
If the wall were five feet long, the pressure would be acting
over the entire 20 square foot (5 ft x 4 ft) area of the wall. The
total force acting to push the wall would be:
F = 31.2 x Hz x L
Force, lb = (Pressure, Ib/sq ft) (Area, sq ft)
- 124.8 Ib/sq ft x 20 sq ft
= 2496 lbs
If the pressure in psi were used, the problem would be simi-
lar:
Force, lb = (Pressure, Ib/sq in) (Area, sq in)
= 0.866 psi x 48 in x 60 in
= 2494 lb*
The general formula, then, for finding the total force acting
on a side wall of a tank is:
F = force in pounds
H = head in feet
L = length of wall in feet
312= constant with units of Ibs/cu
ft and considers the fact that
the force results from H/2 or
half the depth of the water
which is the average depth.
The force is exerted at H/3
from the bottom.
Example: Find the force acting on a five-foot long wall in a
four-foot deep tank.
Force, lb = 31.2 (Head, ft)2 (Length, ft)
= 31.2 Ib/cu ft x (4 ft)2 x 5 ft
= 2496 lbs
Occasionally an operator is warned: NEVER EMPTY A
TANK DURING PERIODS OF HIGH GROUNDWATER. Why?
The pressure on the bottom of the tank caused by the water
surrounding the tank will tend to float the tank like a cork if the
upward force of the water is greater than the weight of the tank.
F = upward force in pounds
H = head of water on tank
bottom, in feet
A = area of bottom of tank
in square feet
62.4 = a constant with units of
Ibs/cu ft
F = 62.4 x H x A
This formula is approximately true if the tank doesn't crack,
leak, or start to float.
Example: Find the upward force on the bottom of an empty
tank caused by a groundwater depth of 8 feet above
the tank bottom. The tank is 20 ft wide and 40 ft long.
Force, lb = 62.4 (Head, ft) (Area, sq ft)
= 62.4 Ib/cu ftx8ftx20ftx40ft
= 399,400 lb
17.10 VELOCITY AND FLOW RATE
17.100 Velocity
The velocity of a particle or substance is the speed at which
it is moving. It is expressed by indicating the length of travel
and how long it takes to cover the distance. Velocity can be
expressed in almost any distance and time units. For instance,
a car may be traveling at a rate of 280 miles per five hours.
However, it is normal to express the distance traveled per unit
time. The above example would then become:
' Difference in answer due to rounding off of decimal points.

-------
490 Treatment Plants
Velocity, mi/hr
280 miles
5 hours
56 miles/hour
The velocity of water in a channel, pipe, or other conduit can
be expressed in the same way. If the particle of water travels
600 feet in five minutes, the velocity is:
Velocity, ft/min
distance, ft
time, minutes
= 600 ft
5 min
= 120 ft/min
If it is desired to express the velocity in feet per second,
multiply by 1 min/60 seconds.
NOTE:
1 minute
is like — and does not change the relative
60 seconds	1
value of the answer. It only changes the form of the answer.
Velocity, ft/sec	= (Velocity, ft/min) (1 min/60 sec)
= 120 f* x 1
ftffl 60 sec
= 120
60 sec
= 2 ft/sec
17.101 Flow Rate
If water in a one-foot wide channel is one foot deep, then the
cross sectional area of the channel is 1 ft x 1 ft = 1 sq ft.
If the velocity in this channel is 1 ft per second, then each
second a body of water 1 sq ft in area and 1 ft long will pass a
given point. The volume of this body of water would be 1 cubic
foot. Since one cubic foot of water would pass by every sec-
ond, the flow rate would be equal to 1 cubic foot per second, or
1 cfs.
To obtain the flow rate in the above example the velocity was
multiplied by the cross sectional area. This is another impor-
tant general formula.
Q = flow rate, cfs or
cu ft/sec
V = velocity, ft/sec
A = area, sq ft
V x A
Example: A rectangular channel 3 feet wide contains water 2
feet deep and flowing at a velocity of 1.5 feet per
second. What is the flow rate in cfs?
Q = V x A
Flow rate, cfs = Velocity, ft/sec x Area, sq ft
= 1.5 ft/sec x 3 ft x 2 ft
= 9 cu ft/sec
Example: Flow in a 2.5 foot wide channel is 1.4 ft deep and
measures 11.2 cfs. What is the average velocity?
In this problem we want to find the velocity.
Therefore, we must rearrange the general formula
to solve for velocity.
v = 9
A
Velocity, ft/sec
Flow Rate, cu ft/sec
Area, sq ft
= 11.2 CM ft/sec
2.5# x 1.4/ft
11.2 ft/sec
3^5
= 3.2 ft/sec
Example: Flow in an 8-inch pipe is 500 GPM. What is the
average velocity?
,>2
Area, sq ft
0.785 (Diameter, ft)
0.785 (8/12 ft)2
0.785 (2/3 ft)2
0.785 (2/3 ft) (2/3 ft)
0.785 (4/9 ft2)
0.35 sq ft
Flow, cfs
cu ft
1 min
= Flow, gal/min x.
7.48 gal 60 sec
cu ft v 1 n»in
7.48	60 sec
Velocity, ft/sec
= 500 gal y
win
_ 500 cu ft
448.8 sec
= 1.114 cfs
Flow, cu ft/sec
Area, sq ft
1.114 ft3/sec
0.35 ft2
3.18 ft/sec
17.11 PUMPS
17.110 General
Atmospheric pressure at sea level is approximately 14.7 psi.
This pressure acts in all directions and on all objects. If a tube
is placed upside down in a basin of water and a 1 psi partial
vacuum is drawn on the tube, the water in the tube will rise
2.31 feet.

-------
Arithmetic 491
r>=0
2.31 ft
13.7 psi absolute pressure
(-1 psi gage pressure)
14.7 psi absolute pressure
(0 psi gage pressure)
NOTE: 1 ft of water = 0.433 psi; therefore,
1 psi =
1
0.433
ft = 2.31 ft of water
The action of the partial vacuum is what gets water out of a
sump or well and up to a pump. It is not sucked up, but it is
pushed up by atmospheric pressure on the water surface in the
sump. If a complete vacuum could be drawn, the waver would
rise 2.31 x 14.7 = 33.9 feet; but this is impossible to achieve.
The practical limit of the suction lift of a positive displacement
pump is about 22 feet, and that of a centrifugal pump is 15 feet.
17.111 Work
Work can be expressed as lifting a weight a certain vertical
distance. It is usually defined in terms of foot-pounds.
Example: A 165-pound man runs up a flight of stairs 20 feet
high. How much work did he do?
Work, ft-lb = Weight, lb x Height, ft
= 165 lb x 20 ft
= 3300 ft-lb
17.112 Power
Power is a rate of doing work and is usually expressed in
foot-pounds per minute.
Example: If the man in the above example runs up the stairs in
three seconds, how much power has he exerted?
Power, ft-lbs/sec
Work, ft-lb
Time, sec
= 3300 ft-lbs y 60 W
3 vft minute
= 66,000 ft-lb/min
17.113 Horsepower
Horsepower is also a unit of power. One horsepower is de-
fined as 33,000 ft-lbs per minute or 746 watts.
Example: How much horsepower has the man in the previous
example exerted as he climbs the stairs?
Horsepower, = (power, ft-lb/min)
HP
(			)
V 33,000 ft-lb/min /
= 66,000 ft-lb/min x
= 2 HP
33,000 ft-lb/min
Horsepower
33,000 ft-lb/min
Work is also done by lifting water. If the flow from a pump is
converted to a weight of water and multiplied by the vertical
distance it is lifted, the amount of work or power can be ob-
tained.
Horse-
power,
HP
_ Flow, gal x ^ x 8.34 lb x Horsepower
min	gal 33,000 ft-lb/min
Solving the above relation, the amount of horsepower nec-
essary to lift the water is obtained. This is called water horse-
power.
Water, HP = (Flow, gpm) (H, ft)
3960*
However, since pumps are not 100% efficient (they cannot
transmit all the power put into them), the horsepower supplied
to a pump is greater than the water horsepower. Horsepower
supplied to the pump is called brake horsepower.
Ep = Efficiency of Pump
(Usual range 50-85%,
depending on type
and size of pump)
Brake, HP = Flow, gpm x H, ft
3960 x E„
Motors are also not 100% efficient; therefore, the power
supplied to the motor is greater than the motor transmits.
•m = Efficiency of motor
(Usual range 80-95%,
depending on type
and size of motor)
Motor, HP = F|0W- 9Pm x H'n
3960 x Ep x Em
The above formulas have been developed for the pumping
of water and wastewater which have a specific gravity of 1.0. If
other liquids are to be pumped, the formulas must be multiplied
by the specific gravity of the liquid.
Example: A flow of 500 gpm of water is to be pumped against
a total head of 100 feet by a pump with an efficiency
of 70%. What is the pump horsepower?
Brake, HP = Flow, gpm x H. ft
3960 x Ep
_ 500 x 100
3960 x 0.70
= 18 HP
Example: Find the horsepower required to pump gasoline
(specific gravity = 0.75) in the above problem.
Brake, HP = 500 x 100 * 0.75
3960 x 0.70
= 13.5 HP (gasoline is lighter and re-
quires less horsepower)
17.114 Head
Basically, the head that a pump must work against is deter-
mined by measuring the vertical distance between the two
water surfaces, or the distance the water must be lifted. This is
called the static head. Two typical conditions for lifting water
are shown on the next page.
~ 8.34 lb y HP = 1
gal 33,000 ft-lb/min 3960
1 gallon weighs 8.34 pounds and 1 horsepower is the same as
33,000 ft-lb/min.
H or Head In feet is the same as Lift in feet.

-------
492 Treatment Plants
If a pump were designed in the above examples to pump
only against head H, the water would never reach the intended
point. The reason for this is that the water encounters friction in
the pipelines. Friction depends on the roughness and length of
pipe, the pipe diameter, and the flow velocity. The turbulence
caused at the pipe entrance (point A); the pump (point B); the
pipe exit (point C); and at each elbow, bend, or transition also
adds to these friction losses. Tables and charts are available in
Section 17.118 for calculation of these friction losses so they
may be added to the measured or static head to obtain the total
head. For short runs of pipe which do not have high velocities,
the friction losses are generally less than 10 percent of the
static head.
Example: A pump is to be located eight feet above a wet well
and must lift 1.8 MGD another 50 feet to a storage
reservoir. If the pump has an efficiency of 75% and
the motor an efficiency of 90%, what is the cost of
the power consumed if one kilowatt hour costs 4
cents?
Since we are not given the length or size of pipe and
the number of elbows or bends, we will assume
friction to be 10% of static head.
Static Head, ft
Friction
Losses, ft
Total Dynamic
Head, ft
Flow, gpm
Motor, HP
Kilowatt-hrs
Cost
= Suction Lift, ft +
Discharge Head, ft
= 8 ft + 50 ft
= 58 ft
= 0.1 (Static Head, ft)
= 0.1 (58 ft)
= 5.8 ft
= Static Head, ft +
Friction Losses, ft
= 58 ft + 5.8 ft
= 63.8 ft
= 1,800,000 gal x day x 1 Iv
day	24 lv 60 min
= 1250 gpm (assuming pump runs
24 hours per day)
_ Flow, gpm x H, ft
3960 x Ep x Em
= 1250 x 63.8	
3960 x 0.75 x 0.9
= 30 HP
= 30 HF x 24 hrs/day x 0.746 kw/HP*
= 537 kilowatt-hrs/day
= KWH x $0.04/KWH
= 537 x 0.04
= $21.48/day
17.115 Pump Characteristics
The discharge of a centrifugal pump, unlike a positive dis-
placement pump, can be made to vary from zero to a
maximum capacity which depends on the speed, head, power,
and specific impeller design. The interrelation of capacity, effi-
ciency, head, and power is known as the characteristics of the
pump.
The first relation normally looked at when searching for a
pump is the head vs. capacity. The head of a centrifugal pump
normally rises as the capacity is reduced. If the values are
plotted on a graph they appear as follows:
Capacity
Another important characteristic is the pump efficiency. It
begins from zero at no discharge, increases to a maximum,
and then drops as the capacity is increased. Following is a
graph of efficiency vs. capacity:
Capacity
The last important characteristic is the brake horsepower or
the power input to the pump. The brake horsepower usually
increases with increasing capacity until it reaches a maximum,
then it normally reduces slightly.
o.
x
m
' See Conversion Tables — Section 17.17, "Work and Energy.
Capacity

-------
Arithmetic 493
These pump characteristic curves are quite important. Pump
sizes are normally picked from these curves rather than calcu-
lations. For ease of reading, the three characteristic curves are
normally plotted together. A typical graph of pump characteris-
tics is shown as follows:
HEAD
10 12 14 16
Capacity in 100 fcpp
The curves show that the maximum efficiency for the particu-
lar pump in question occurs at approximately 1475 gpm, a
head of 132 feet, and a brake horsepower of 58. Operating at
this point the pump has an efficiency of approximately 85%.
This can be verified by calculation:
BHP = F:'ow¦ 9pm x "
3960 x E
As previously explained, a number can be written over one
without changing its value:
BHP _ gpm x H
1
3960 x E
Since the formula is now in ratio form, it can be cross multi-
plied.
BHP x 3960 x E = gpm x H x 1
Solving for E,
E = gpm x H
3960 x BHP
E _ 1475 gpm x 132 ft
3960 x 58 HP
= 0.85 or 85% (Check)
The preceding is only a brief description of pumps to
familiarize the operator with their characteristics. The operator
does not normally specify the type and size of pump needed at
a plant. If a pump is needed, the operator should be able to
supply the information necessary for a pump supplier to pro-
vide the best possible pump for the lowest cost. Some of the
information needed includes:
1. Flow range desired
2 Head conditions
a.	Suction head or lift
b.	Pipe and fitting friction head
c.	Discharge head
3.	Type of fluid pumped and temperature
4.	Pump location
17.116 Evaluation of Pump Performance
1. Capacity
Sometimes it is necessary to determine the capacity of a
pump. This can be accomplished by determining the time it
takes a pump to fill or empty a portion of a wet well or diversion
box when all inflow is blocked off.
EXAMPLE:
a. Measure the size of the wet well.
Length = 10 ft
Width =10 ft
Depth = 5 ft
Volume, cu ft
(We will measure the time it takes
to lower the well a distance of
five feet)
= L, ft x W, ft x D, ft
= 10 ft x 10 ft x 5 ft
= 500cuft
b. Record time for water to drop five feet in wet well.
Time =10 minutes 30 seconds
= 10.5 minutes
c.
Calculate pumping rate or capacity.
Pumping Rate, gpm = Volume- 9a"ons
Time, minutes
_ (500 cu ft) (7.5 gal/cu ft)
10.5 min
_ 3750
10.5
= 357 gpm
If you know the total dynamic head and have the pump's
performance curves, you can determine if the pump is deliver-
ing at design capacity. If not, try to determine the cause (see
Chapter 15, "Maintenance"). After a pump overhaul, the
pump's actual performance (flow, head, power and efficiency)
should be compared with the pump manufacturer's perform-
ance curves. This procedure for calculating the rate of filling or
emptying of a wet well or diversion box can be used to calibrate
flow meters.
2. Efficiency
To estimate the efficiency of the pump in the previous exam-
ple, the total head must be known. This head may be esti-
mated by measuring the suction and discharge pressure. As-
sume these were measured as follows:
2 in. mercury
vacuum
I
Suction
side
UMF
I
20 psi
Discharge
side
flow
No additional information is necessary if we assume the
pressure gages are at the same height and the pipe diameters
are the same. Both pressure readings must be converted to
feet.

-------
494 Treatment Plants
Suction Lift, ft
= 2 in Mercury x
1.133 ft water*
1 in Mercury
= 2.27 ft
Discharge Head, ft = 20 psi x 2.31 ft/psi*
= 46.20 ft
Total Head, ft = Suction Lift, ft + Discharge Head, ft
= 2.27 ft + 46.20 ft
= 48.47 ft
Calculate the power output of the pump or water horse-
power:
Water Horsepower, _ (Flow, gpm) (Head, ft)
HP	3960
= (357 gpm) (48.47 ft)
3960
= 4.4 HP
To estimate the efficiency of the pump, measure the
kilowatts drawn by the pump motor. Assume the meter indi-
cates 8000 watts or 8 kilowatts. The manufacturer claims the
electric motor is 80% efficient.
Brake Horsepower,
HP
Pump
Efficiency, %
= (Power to elec. motor) (motor eff.)
= (8 kw) (0.80)
0.746 kw/HP
= 8.6 HP
_ Water Horsepower, HP x 100%
Brake Horsepower, HP
_ 4.4 HP x 100%
8.6 HP
= 51%
The following diagram may clarify the above problem:
Power Input
co Motor oi
Motor HP
	»
8 kw or
10.7 HP
Power Transmitted
to Water

to Pump or
Brake HP

or Water
Horsepower
MOTOR
6.U kw o r
8.6 HP
PUMP
3.3	kw
4.4	HP


Motor Loss
1,6 kw or

P ump Los s
3.1 kw or

2.1 IIP

4.2 HP

The wire to water efficiency is the efficiency of the power
input to produce water horsepower.
Wire to Water = Water Horsepower, HP x 1Q()%
Efficiency, %	Power Input, HP
= 4 4 HP x 100%
10.7 HP
= 41%
17.117 Pump Speed — Performance Relationships
Changing the velocity of a centrifugal pump will change its
operating characteristics. If the speed of a pump is changed,
the flow, head developed, and power requirements will
change. The operating characteristics of the pump will change
with speed approximately as follows:
Flow, Qn =
Head, Hn =
Power, P„ =

r = rated
now
N = pump speed
Actually, pump efficiency does vary with speed; therefore,
these formulas are»not quite correct. If speeds do not vary by
more than a factor of two (if the speeds are not doubled or cut
in half), the results are close enough. Other factors contributing
to changes in pump characteristic curves include impeller wear
and roughness in pipes.
Example: To illustrate these relationships, assume a pump has
a rated capacity of 600 gpm, develops 100 ft of
head, and has a power requirement of 15 HP when
operating at 1500 rpm. If the efficiency remains con-
stant, what will be the operating characteristics if the
speed drops to 1200 rpm?
Calculate new flow rate or capacity:
Flow, Qn = r N"
—- 1 Qr
Nr J
1200 rpm '
_ 1500 rpm
= ^ — J 600 9pm
= (4) (120 gpm)
= 480 gpm
600 gpm
Calculate new head:
2
Head, Hn
1200 rpm "1 100ft
L 1500 rpm J
(*)-¦
(£)
(100 ft)
= 16(4 ft)
= 64 ft
Calculate new power requirement:
Power, P„
/ 1200 rpm \3m
\ 1500 rpm /
(t)*,5HP
(£)
(-so-
HP
64
25
= 7.7 HP
(15 HP)
HP)
* See Conversion Tables — Section 17.17, Pressure.

-------
Arithmetic
495
17.118 Friction or Energy Losses
Whenever water flows through pipes, valves and fittings,
energy is lost due to pipe friction (resistance), friction in valves
and fittings, and the turbulence resulting from the flowing water
changing its direction. Figure 17.1 can be used to convert the
friction losses through valves and fittings to lengths of straight
pipe that would produce the same amount of friction losses. To
estimate the friction or energy losses resulting from water flow-
ing in a pipe system, we need to know:
1.	Water flow rate,
2.	Pipe size or diameter and length,
3.	Number, size and type of valve fittings.
An easy way to estimate friction or energy losses is to follow
the following steps:
1.	Determine the flow rate,
2.	Determine the diameter and length of pipe,
3.	Convert all valves and fittings to equivalent lengths of
straight pipe (see Figure 17.1),
4.	Add up total length of equivalent straight pipe,
5.	Estimate friction or energy losses by using Figure 17.2.
With the flow in GPM and diameter of pipe, find the friction
loss per 100 feet of pipe. Multiply this value by equivalent
length of straight pipe.
The procedure for using Figure 17.1 is very easy. Locate the
type of valve or fitting you wish to convert to an equivalent pipe
length; find its diameter on the right-hand scale; and draw a
straight line between these two points to locate the equivalent
length of straight pipe.
Example: Estimate the friction losses in the piping system of a
lift station when the flow is 1,000 GPM. The 8-inch
suction line is 10 feet long and contains a 90-degree
bend (long sweep elbow), a gate valve and an 8-inch
by 6-inch reducer at the inlet to the pump. The 6-inch
discharge line is 30 feet long and contains a check
valve, a gate valve, and three 90-degree bends
(medium sweep elbows):
SUCTION LINE (8-inch diameter)
Item
1.	Length of pipe
2.	90-degree bend
3.	Gate valve
4.	8-inch by 6-inch reducer
5.	Ordinary entrance
Total equivalent length
Friction loss (Fig. 17.2) = 1.76 ft/100 ft of pipe
Equivalent Length, It
10
14
4
17
J2
57 feet
Estimate the total friction losses in pumping system for a
flow of 1,000 GPM.
SUCTION
Loss = (1.76 ft/100 ft) (57 ft)	= 1.0 ft
DISCHARGE
Loss = (7.73 ft/100 ft) (115 ft)
Total friction losses, ft
= 8.8 ft
= 9.8 ft
17.12 STEPS IN SOLVING PROBLEMS
17.120 Identification of Problem
To solve any problem, you have to identify the problem,
determine what kind of answer is needed, and collect the in-
formation needed to solve the problem. A good approach to
this type of problem is to examine the problem and make a list
of KNOW and UNKNOWN information.
Example: Find the theoretical detention time in a rectangular
sedimentation tank 8 feet deep, 30 feet wide, and 60
feet long when the flow is 1.4 MGD.
Known
Depth = 8 ft
Width =30 ft
Length = 60 ft
Row =1.4 MGD
Unknown
Detention Time, hours
Sometimes a drawing or sketch will help to illustrate a prob-
lem and indicate the knowns, unknowns, and possibly addi-
tional information needed.
17.121. Selection of Formula
Most problems involving mathematics in wastewater treat-
ment plant operation can be solved by selecting the proper
formula, inserting the known information, and calculating the
unknown. In our example, we could look in Chapter 5,
"Sedimentation and Flotation," or in Section 17.15 of this chap-
ter, "Summary of Formulas," to find a formula for calculating
detention time. From Section 17.15:
Detention (Tank Volume, cu ft) (7.5 gal/cu ft) (24 hr/day)
Time, hrs
Flow, gal/day
To convert the known information to fit the terms in a formula
sometimes requires extra calculations. The next step is to find
the values of any terms in the formula that are not in the list of
known values.
Flow, gal/day = 1.4 MGD
= 1,400,000 gal/day
From Section 17.150:
Tank Volume, = (Length, ft) (Width, ft) (Height, ft)
cuft	=60ftx30ftx8ft
= 14,400 cu ft
DISCHARGE UNE (6-inch diameter)
Kern
1.	Length of pipe
2.	Check valve
3.	Gate valve
4.	Three 90-degree bends (3) (14)
Total equivalent length
Friction loss (Fig. 17.2) = 7.73 ft/100 ft of pipe
Equivalent Length, it
30
38
4
42
114 feet
Solution of Problem:
Detention _ (Tank Volume, cu ft) (7.S gal/cu ft) (24 hr/day)
Time' hrs	Flow, gal/day
= (14,400 cu ft) (7.5 gal/cu ft) (24 hr/day)
1,400,000 gal/day
= 1.9 hr
The remainder of this section discusses the details that must
be considered in solving this problem.

-------
496 Treatment Plants
Swing Check Valve,
Fully Open
Globe Valve, Open
Gate Valve
# Closed
V4 Closed
UCIosed
Fully Open
Angle Valve, Open
tfiLJCb
Standard Tea
Square Elbow
Borda Entrance
Close Return Bend
Standard Tee
Through Side Outlet
Ordinary Entrance
[-"i Sudden Contraction
\ V—d/D-H
V	d/D -Vl
N	d/D-^4
Medium Sweep Elbow or
run of Tee reduced H
45* Elbow
r--V°_
Sudden EnlargeBient-
I	d/D_ H
d/n- Vi
d/D-#
Standard Elbow or run of
Tee reduced V4
Long Sweep Elbow or
run of Standard Tee
Gpyrlght by Cram Co.
3000
2000
r1000
-500
300
200
rl00
s
50 i
£
*
Example
The dotted line shows that
the resistance of a 6-inch
Standard Elbow is equiva-
lent to approximately 16
feet of 6-incn Standard Pipe.
Nat*
For sudden enlargements or
sudden contractions, use the
smaller diameter, d, on the
pipe size scale.
48—
42-
36-
30-
22-
24—
20-
18-
16-
14-
i
E
•e
12—
10-
9 —
-20 f*	g 8	
O	1
10
: JS
¦5 S
5
1	I
2
-I
•0.5
0.3
0.2
-0.1
0	6
1	5H
5 4
I3fc~
3 —
2V4-
tu-
rn
H-
V4-
-50
-30
20
-10
-5
-3
-2
-1
L0.5
Fig. 17.1 Resistance of valves and fittings to flow of water.
(Reprinted by permission of Crane Co.)

-------
Arithmetic 497
U.I.
«FM
UbL
171 ta.
11a
tain.
Utah
tlm
Uln
VoL
FrM.
Vol
Mot
Vol
MM.
Vol
Mot
Vol
FrM.
Vol.
rtM.
Vol
FHA
10
10.56
95.9
6.02
23.0
3.71
6.86
2.15
1.77
158
83
.96
.25
.67
.11
21


12.0
K.l
7 42
25.1
4.20
6.34
3.15
2 94
1.91
.87
1.34
.36
N




11.1
54.6
6 44
13.6
4 73
6.26
2.87
IB
2.01
.75
40



. . . .
14.1
K.
I SI
23.5
6 30
10.79
3 82
3.10
2 68
1 28
60



....


10 7
360
7.88
16.4
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9.91
10.9
11.1
12.7
13.6
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1.17
2.02
3.10
4.40
5.93
7.71
9.73
11.9
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19.1
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2.04
2.55
3.06
3.57
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5.11
5.62
6.13
1.64
7.15
7.66
I.94
10.20
II.45
12.1
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1.03
1.31
1.71
2.24
2.74
3.21
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4.54
5.25
1.03
1.22
10.7
13.4
16.6
19.9
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1.28
1.60
1.92
2.25
2.57
2.19
311
3.53
3.85
417
4.49
4.11
5.1!
6.41
7.22
1.02
182
9.62
114
12.1
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1.20
1.31
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2.11
2.72
3.41
4.16
4.98
5.88
7.93
10.22
12.9
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1.13
1.36
1.59
I.12
2.04
2.27
2.50
2.72
2.95
3.18
3.40
3.97
4.54
5.11
5.67
6.24
6.11
7.94
9.08
10.2
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12.5
13.6
14.7
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2.84
3.87
5.06
6.34
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9.80
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No oHowonce Hot btM i*o4« for Ofo,
In dlamoter, or any olker
obnormal condition of Interior awrfec*.
Any Poctor of Safety mn) bo e«H-
mated from the local condition. and
•ho requtromont. of eocfc parttevtar
1.40
1.53
1.66
1.79
I.91
2.24
2.55
2.87
3.19
3.51
3.83
4.47
5.11
5.74
6.38
7.02
7.66
8.30
8.93
9.57
102
10.8
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12.1
12.8
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1.14
1.44
1.76
2.14
2.53
2.94
3.40
3.91
445
500
5.58
6.19
6.84
13% ha reasonable Factor of Safety.
1.84
2.04
2.25
2.45
2.86
3.27
3.68
4.09
4.49
4.90
531
5.72
6.13
654
(.94
7.35
7.76
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10.2
12.3
14.3
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1.09
1.25
1.42
1.60
1.78
1.97
2.1/
3.31
4.79
6.55
1.42
1.56
1.70
I.99
2.27
2.55
2.84
3.12
340
3.69
397
4.76
4.54
4.8?
511
5.39
5.67
7.10
8.51
9.93
II.3
12.8
14.2
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.07
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.22
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1.33
1.88
256
3.31
4.18
5.13
125
1.46
1.67
1.88
2.08
2.29
2.50
7.71
7.92
313
333
3.54
3.75
3.96
4.17
5.21
6.25
7.29
8.34
9.38
10.4
12.5
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17
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5.58
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4.41
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6.38
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4.59
7.98
1.17
6.30
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5.11
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1.66
7.56
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6.13
112
2.26
8.83
124
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12.8
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10.09
1.61
8.17
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373
11.3
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9.19


12.6
2.48
10.2
Fig. 17.2 Friction Loss for Water in Feet Per 100 Feet of Pipe
(Reprinted from the 10th Edition of the Standard* of the Hydraulic
Institute, 122 East 42nd Street, New York)

-------
498 Treatment Plants
17.122 Arrangement of Formula
Once the proper formula is selected, you may have to rear-
range the terms to solve for the unknown term. In Section
17.153, "Velocity," we have the formula:
Flow Rate, cu ft/sec
Velocity, ft/sec =
Cross-Sectional Area, sq ft
or
V =
Q
In this equation if Q and A were given, the equation could be
solved for V. If V and A were known, the equation would have
to be rearranged to solve for Q. To move terms from one side
of an equation to another, use the following rule:
When moving a term or number from one side of an equation
to the other, move from numerator (top) of one side to de-
nominator (bottom) of the other; or from the denominator (bot-
tom) of one side to the numerator (top) of the other.
V =
or Q = AV
or A = _9_
If the volume of a sedimentation tank and the desired deten-
tion time were given, the detention time formula could be rear-
ranged to calculate the design flow.
Detention _ (Tank Vol., cu ft) (7.5 gal/cu ft) (24 hr/day)
Time- hrs	Flow, gal/day
By rearranging the terms
Flow, _ (Tank Vol., cu ft) (7.5 gal/cu ft) (24 hr/day)
gal/day	Detention Time, hrs
17.123 Units and Dimensional Analysis
Each term in a formula or mathematical calculation must be
of the correct units. The area of a rectangular clarifier (Area, sq
ft = Length, ft x Width, ft) can't be calculated in square feet if
the width is given as 246 inches or 20 feet 6 inches. The width
must be converted to 20.5 feet. In the example problem, if the
tank volume were given in gallons, then the 7.5 gal/cu ft would
not be needed. THE UNITS IN A FORMULA MUST ALWAYS
BE CHECKED BEFORE ANY CALCULATIONS ARE PER-
FORMED TO AVOID TIME-CONSUMING MISTAKES.
Detention = (Tank Volume, cu ft) (7.5 gal/cu ft) (24 hr/day)
Time, hrs	Flow, gal/day

hr
MM *Vt
= hr (all other units cancel)
day
9#
NOTE: We have hours = hr. One should note that the hour
unit on both sides of the equation can be cancelled out,
and nothing would remain. This is one more check that
we have the correct units. By rearranging the detention
time formula, other unknowns could be determined.
If the design detention time and design flow were known, the
required capacity of the tank could be calculated.
Tank Volume, = (Detention Time, hr)(Flow, gal/day)
cu	(7.5 gal/cu ft) (24 hr/day)
If the tank volume and design detention time were known,
the design flow could be calculated.
Flow, = (Tank Volume, cu ft) (7.5 gal/cu ft) (24 hr/day)
gal/day	Detention time, hrs
Rearrangement of the detention time formula to find other
unknowns illustrates the need to always use the correct units.
17.124 Calculations
Sections 17.12, "Multiplication," and 17.13, "Division," out-
line the steps to follow in mathematical calculations. In general,
do the calculations inside parentheses ( ) first and brackets
[ ] next. Calculations should be done above and below the
division line before dividing.
Detention = [(Tank Volume, cu ft) (7.5 gal/cu ft) (24 hr/day)]
Ti^1e, hrs	Flow, gal/day
^ [(14,400 cu ft) (7.5 gal/cu ft) (24 hr/day)]
1,400,000 gal/day
2,592,000 gal-hr/day
1,400,000 gal/day
= 1.85, or
= 1.9 hr
24
14400
7.5
180
120
1152000
168
14400
180.0
2,595,000

1.85

1400)2592

1400
11920
11200
7200
7000
17.125 Significant Figures
In calculating the detention time in the previous section, the
answer is given as 1.9 hr. The answer could have been calcu-
lated:
Detention
Time, hrs
_ 2,592,000 gal-hr/day
1,400,000 gal/day
= 1.850428571428571428..
.hours
How does one know when to stop dividing? Common sense
and significant figures both help.
First, consider the meaning of detention time and the meas-
urements that were taken to determine the knowns in the for-
mula. Detention time in a tank is a theoretical value and as-
sumes that all particles of water throughout the tank move
through the tank at the same velocity. This assumption is not
correct; therefore, detention time can only be a representative
time for some of the water particles.
Will the flow of 1.4 MGD be constant throughout the 1.9
hours, and is the flow exactly 1.4 MGD, or could it be 1.35
MGD or 1.428 MGD? A carefully calibrated flow meter may
give a reading within 2% of the actual flow rate. Flows into a
tank fluctuate and flow meters do not measure flows extremely
accurately; so the detention time again appears to be a repre-
sentative or typical detention time.
Tank dimensions are probably satisfactory within 0.1 ft. A
flow meter reading of 1.4 MGD is less precise and it could be
1.3	or 1.5 MGD. A 0.1 MGD flow meter error when the flow is
1.4	MGD is (0.1/1.4) x 100% = 7% error. A detention time of
1.9 hours, based on a flow meter reading error of plus or minus
7%, also could have the same error or more, even if the flow
was constant. Therefore, the detention time error could be 1.9
hours x 0.07 = ±0.13 hours.
In most of the calculations in the operation of wastewater
treatment plants, the operator uses measurements determined
in the lab or read from charts, scales, or meters. The accuracy
of every measurement depends on the sample being meas-
ured, the equipment doing the measuring, and the operator
reading or measuring the results. Your estimate is no better
than the least precise measurement. Do not retain more than
one doubtful number.

-------
Arithmetic 499
To determine how many figures or numbers mean anything
in an answer, the approach called "significant figures" is used.
In the example the flow was given in two significant figures (1.4
MGD), and the tank dimensions could be considered accurate
to the nearest tenth of a foot (depth = 9.0 ft) or two significant
figures. Since all measurements and the constants contained
two significant figures, the results should be reported as two
significant figures or 1.9 hours. The calculations are normally
carried out to three significant figures (1.85 hours) and
rounded off to two significant figures (1.9 hours).
Decimal points require special attention when determining
the number of significant figures in a measurement.
Measurement Significant Figures
0.00325
11.078
21,000.
Example: The distance between two points was divided into
three sections, and each section was measured by a
different group. What is the distance between the
two points if each group reported the distance it
measured as follows:
Group Distance, ft Significant Figures
A
B
C
Total
Distance
11,300.
2,438.9
87.62
13,826.52
Group A reported the length of the section it
measured to three significant figures; therefore, the
distance between the two points should be reported
as 13,800 feet (3 significant figures).
When adding, subtracting, multiplying, or dividing, the
number of significant figures in the answer should not be more
than the term in the calculations with the least number of signif-
icant figures.
17.126 Check Your Results
After having completed your calculations, you should care-
fully examine your calculations and answer. Does the answer
seem reasonable? If possible, have another operator check
your calculations before making any operational changes.
1713 TYPICAL TREATMENT PLANT PROBLEMS
(ENGLISH SYSTEM)
17.130 Grit Channels
1. Grit Channel Velocity
Example: Estimate the velocity of wastewater flowing through
a grit channel if a stick travels 32 feet in 36 seconds.
Know
Distance = 32 ft
Time = 36 sec
Unknown
Velocity, ft/sec
Velocity, ft/sec = Distance Traveled, ft
Time, sec
= 32
36 sec
= 0.89 ft/sec
2. Volume of Grit Removed
Example: A grit channel removed 3.2 cu ft of grit during a
period when the total flow was 0.8 MG. How many
cu ft of grit are removed per MG?
Known
Vol. of Grit = 3.2 cu ft
Vol. of Flow = 0.8 MG
Grit Removed, = Volume of Grit, cu ft
cu ft/MG	Volume of Flow, MG
_ 3.2 cu ft
Unknown
Grit Removed,
cu ft /MG
0.8 MG
4.0 cu ft/MG
17.131 Sedimentation Tanks and Ciarifiers
Example: A circular clarifier handles a flow of 0.9 MGD. The
clarifier is 50 feet in diameter and 8 feet deep. Find
the detention time, surface loading rate, and weir
overflow rate.
Known	Unknown
Flow = 0.9 MGD Detention Time, hours
Diameter = 50 ft	Surface Loading, gpd/sq ft
Depth = 8 ft	Weir Overflow, gpd/ft
DETENTION TIME
Detention _ (Tank Volume, cu ft) (7.5 gal/cu ft) (24 hr/day)
Time, hrs
Tank
Volume,
cu ft
Flow, gal/day
= (Area, sq ft) (Depth, ft)
Clarifier
Area,
sq ft
Clarifier Area, sq ft
= 0.785 (Diameter, ft)
Tank Volume, cu ft =
0.785 (Diameter, ft)2
0.785 (50 ft)2
1962.5 sq ft, or
1960 sq ft
(Area, sq ft) (Depth, ft)
(1960 sq ft) (8 ft)
15,680 cu ft
Detention _ (Tank Volume, cu ft) (7.5 gal/cu ft) (24 hr/day)
Time' hre	Flow gal/day
= (15,680 cu ft) (7.5 gai/cu ft) (24 hr/day)
900,000 gal/day
. 2,820,000
900,000
= 3.1 hr
SURFACE LOADING RATE
Surface Loading, gpd/sq ft = F*ow' ^
Area, sq ft
900,000 gpd
1960 sq ft
459 gpd/sq ft

-------
500 Treatment Plants
WEIR OVERFLOW RATE
Weir Overflow, gpd/ft
Length of Weir, ft
Flow, gpd
Weir Overflow, gpd/ft =
Length of Weir, ft
= 3.14 (Diameter, ft)
= 3.14 (50 ft)
= 157 ft
Flow, gpd
Length of Weir, ft
900,000 gpd
157 ft
= 5730 gpd/ft
17.132 Trickling Filters
Example: A flow of 1.1 MGD is applied to a 50-ft diameter
trickling filter which is 4 feet deep. The BOD of the
wastewater is 120 mg/L. Calculate the hydraulic and
organic loadings on the filter.
Known
Flow
Diameter
Depth
BOD
= 1.1 MGD
= 50 ft
= 4 ft
= 120 mg/L
Unknown
Hydraulic Loading, gpd/sq ft
Organic Loading, lbs BOD/day
1000 cu ft
HYDRAULIC LOADING
Hydraulic Loading, gpd/sq ft
Surface Area, sq ft
Flow, gpd
Hydraulic Loading, gpd/sq ft =
Surface Area, sq ft
= 0.785 (Diameter, ft)2
= 0.785 (50 ft)2
= 1960 sq ft
Flow, gpd
ORGANIC LOADING
Organic Loading, '^BOD/day
Surface Area, sq ft
1,100,000 gpd
1960 sq ft
= 561 gpd/sq ft
BOD Applied, lbs/day
17.133 Activated Sludge
Example: Lab results and flow rate for an activated sludge
plant are listed below under the known column. In-
formation helpful to the operator in controlling the
process is listed in the unknown column. The
aerator or aeration tank volume is 0.50 MG.
1800 mg/L
76%
340 ml, or
17%
140 mg/L
110 mg/L
2.0 MGD
Known
Mixed Liquor Suspended Solids (MLSS)
Mixed Liquor Volatile Content
Thirty-Minute Settleable Solids Test*
Primary Effluent BOD
Primary Effluent Suspended Solids
Flow Rate
Unknown
Pounds of Solids in the Aerator
Sludge Volume Index, SVI
Pounds of BOD per Day Applied to Aerator
Sludge Age, days
POUNDS OF SOLIDS IN AERATOR
Aerator Solids, lbs = (MLSS, mg/L) (Tank Vol., MG) (8.34 lbs/gal)
= (1800 mg/L) (0.50 MG) (8.34 lbs/gal)
= 7500 lbs
SLUDGE VOLUME INDEX, SVI
SVI = (Settleable Solids, %) (10,000)
MLSS, mg/L
= (17) (10,000)
1800
= 94
1000 cu ft Volume of Media, 1000 cu ft
POUNDS OF BOD APPLIED PER DAY TO AERATOR
Aerator
Loading, = (Primary Effluent BOD, mg/L) (Flow, MGD) (8.34 lbs/gal)
lbs BOD/day = (140 mglL) (2 0 MGD) (8 34 ibs/gal)
= 2335 lbs BOD/day Applied to Aerator
BOD Applied,
lbs/day
Volume of Media,
1000 cu ft
= (BOD, mg/L) (Flow, MGD) (8.34 lb/gal)
= (Surface Area, sq ft) (Depth, ft)
BOD Applied,
lbs/day
= (BOD, mg/L) (Flow, MGD) (8.34 lb/gal)
= (120 mg/L) (1.1 MGD) (8.34 lb/gal)
= 1100 lbs BOD/day
SSSS- Media' = (Surface Area- sq
-------
Arithmetic 501
17.134 Sludge Digestion
1. C02 in Digester Gas
Example: The total volume of a 100 ml graduate used in the
C02 test is 127 ml. The volume of gas remaining in
the graduate after the C02 test was 82 ml. Find the
percent C02 in the digester gas.
Known	Unknown
Total Volume = 127 ml	Percent C02
Gas Remaining = 82 ml
%C02 = (Total Volume, ml - Gas Remaining, ml) 100%
Total Volume, ml
= (127 ml - 62 ml) 100%
127 ml
, 45 ml
127 ml
= 35%
100%
2. Volatile Acid/Alkalinity Relationship
Example: The volatile acids in a digester are 250 mgIL, and
the alkalinity is 1750 mgIL. Find the volatile acid/al-
kalinity relationship.
Known	Unknown
Volatile Acids = 250 mgIL	Volatile Acid/Alkalinity
Alkalinity = 1750 mg IL
Volatile Acid/ = Volatile Acid, mgIL
Alkalinity	Alkalinity, mg IL
= 250 mgIL
1750 mgIL
= .14
3.	Volume Per Stroke of a Piston Pump
Example: Calculate the volume (in gallons) pumped per
stroke (revolution) by a piston pump with a bore of 2
5/i2 inches and a stroke of 3 inches.
Known	Unknown
Dia. of Piston = 2 V12 in	Volume, gallons
Length of Stroke = 3 in
Cylinder Volume, = (Area, sq in) (Length, in)
C"ln	= (0.785) (2.417 in)2 (3 in)
= 13.75 cu in
= 13.75 cu in
231 cu in/gal
=0.06 gal, or volume pumped per stroke is
0.06 gal.
The actual volume pumped per stroke will be slightly below
0.06 gallon because the system is not 100% efficient.
4.	Percent reduction of Volatile Matter
Example: Find the percent reduction of volatile matter in a
digester if the percent volatile matter in the raw
sludge was 71 percent and the digested sludge was
composed of 53 percent volatile matter.
Known
In, % VM in Raw Sludge =71%
Out, % VM in Dig. Sludge = 53%
Unknown
P, % Reduction of VM
p_ | (In - Out) 1 -|00% See pages 143 and 144 for
L In - (In x Out) J	explanation of formula
= r (-71 - i
L .71 - (.71 X .53) J
-r—1
L.71 - .38 J
100 %
53)
100%
.18
x 100%
.33
= .55 x 100%
= 55%
5. Digester Loading
Example: A digester with a volume of 25,000 cu ft receives
2000 pounds of raw sludge per day with a volatile
content of 70%.
Unknown
Digester Loading,
lb VM/day/cu ft
Known
Digester Volume = 25,000 cu ft
Raw Sludge = 2000 pounds
Volatile Content = 70%
m£S lb/day' =  (Volatile' %)
= (2000 lbs/day) (0.70)
= 1400 lbs/day
Digester Loading, Volatile Matter Added, lb/day
lb VM/day/cu ft	Digester Volume, cu ft
= 1400 lbs/day
25,000 cu ft
= 0.056 lbs VM/day/cu ft
17.135 Ponds
Example: To calculate the different loadings on a pond, the
information listed under known must be available.
Known
Avg. Depth	= 4 ft
Avg. Width	= 400 ft
Avg. Length	= 600 ft
Flow	= 0.5 MGD
BOD	=150mgIL
Population	= 5000 persons
Unknown
Detention Time, days
Population Loading, persons/acre
Hydraulic Load, in/day
Organic Load, lbs BOD/day/acre
DETENTION TIME
Detention Time, days = Pond Volume' ac'ft
Flow Rate, ac-ft/day
Pond Area, acres = 
-------
502 Treatment Plants
Flow Rate, ac-ft/day =
(500,000 gal/day)
Detention Time, days =
(7.48 gal/cu ft)(43,560 sq ft/ac)
1.53 ac-ft-day
Pond Volume, ac/ft
Known
Dose = 10 mgIL
Flow = 0.37 MGD
Unknown
Chlorinator Setting, lbs/day
Flow Rate, ac-ft/day
22.0 ac-ft
Chlorine Feed
Rate, lbs/day
1.53 ac-ft/day
= 14.3 days
POPULATION LOADING
_ Population Served, persons
Pond Area, acres
_ 5000 persons
5.51 acres
= 907 persons/acre
Population Loading,
persons/ac
= (Dose, mg/L)(Flow, MGD)(8.34 lb/gal)
= (10 mg/L)(0.37 MGD)(8.34 lb/gal)
= 30.9, or
= 31 lbs/day
17.137 Laboratory Results
1. Dissolved Oxygen (DO) Saturation, Percent
Example: The dissolved oxygen in a receiving water was 10.3
mg/L when the temperature was 50°F (Saturation
DO = 11.3 mg/L). Determine the percent DO satura-
tion.
Known
DO of Sample = 10.3 mg/L
DO at 100% Sat. = 11.3 mg/L
Unknown
DO Saturation, %
HYDRAULIC LOADING
Hydraulic Loading,
in/day
Depth of Pond, inches
DO Satu-
ration, %
DO of Sample, mg/L
DO at 100% Saturation, mg/L
x 100%
ORGANIC LOADING
Organic Loading,
lb BOD/day/ac
Detention Time, days
= (4 ft)(12 in/ft)
14.3 days
= 3.36 in/day
= (Bod, mg/L)(Flow, MGD)(8.34 lb/gal)
Area, ac
= (150 mg/L)(0.5 MGD)(8.34 lb/gal)
5.51 ac
= 625.5 lb BOD/day
5.51 ac
= 114 lb BOD/day/ac
17.136 Chlorinatlon
1. Chlorine Demand
Example: Determine the chlorine demand* of an effluent if the
chlorine dose is 10.0 mg/L and the chlorine residual
is 1.1 mg/L.
Known	Unknown
Chlorine dose =10.0 mg/L Chlorine Demand, mg/L
Chlorine Residual =1.1 mg/L
= 10 3	x 100%
11.3 mg/L
= 91.2%
2. Biochemical Oxygen Demand (BOD)
Example: Laboratory results are listed under known.
Known
BOD Bottle Volume
Sample Volume
Initial DO of
Diluted Sample
DO of Sample and
Dilution After 5-Day
Incubation Period
= 300 ml
= 12 ml
= 8.0 mg/L
4.0 mg/L
Unknown
BOD, mg/L
BOD,
mg/L
r
DO of Diluted
LInitial DO of Sample After
Diluted Sample, - 5-Day Incuba-
mgIL	tion, mg/L
][
BOD Btl. Vol., m|
Sample Vol., mT
= (8.0 mg/L - 4.0 mg/L)
= 100 mg/L
[ 300 ml "I
12 ml J
Chlorine
Demand,
mg/L
Chlor. Dose, mg/L - Chlor. Residual, mg/L
10.0 mg/L -1.1 mg/L
= 8.9 mg/L
2. Chlorine Feed Rate
Example: To maintain a satisfactory chlorine residual in a
plant effluent, the chlorine dose must be 10 mg/L
when the fiow is 0.37 MGD. Determine the
chlorinator setting (feed rate) in pounds per day.
17.138 Efficiency of Plant or Treatment Process
Example: The influent BOD to a treatment plant is 200 mg/L,
and the effluent BOD is 20 mg/L. What is the BOD
removal efficiency of the plant?
Known
Influent BOD = 200 mg/L
Effluent BOD
Efficiency, %
= 20 mg/L
= (In - Out)
In
Unknown
Plant Efficiency, %
100%
* "Standard Methods" uses the term 'chlorine demand' when refer-
ring to stabilized water such as a domestic water supply and the
term 'chlorinatlon requirement' when referring to wastewater.
= (200 mg/L - 20 mg/L) 1Q0%
200 mg/L
_ 180mg/L_ 100%
200 mg/L
= 90%

-------
Arithmetic 503
17.139 Blueprint Reading
Example: A set of blueprints for a treatment plant has a scale
of 1/4 inch = 1 foot. On the prints, the laboratory
dimensions were measured and found to be 6
inches wide and 9 inches long. What is the floor
area of the laboratory?
Known	Unknown
Scale: 1/4 in = 1 ft Area, sq ft
Length = 9 in
Width = 6 in
Area, sq ft = (Length, ft) (Width, ft)
Find actual length and width in feet.
1/4 in
1 ft
Length, ft
1/4 in
_ 9 in
Length, ft
(9 in) j" 1 ft "I
L 1/4 in J
- O) (4)
= 36 ft
_ 6 in
1 ft
Width, ft
Width, ft
= (6 in) (1 ft)
17.140 Grit Channels
1.	Grit Channel Velocity
Example: Estimate the velocity of wastewater flowing through
a grit channel if a stick travels 16 meters in 40 sec-
onds.
Known	Unknown
Distance = 16 m Velocity, m/sec
Time = 40 sec
Velocity, m/sec = Distance Traveled, m
Time, sec
_ 16 m
40 sec
= 0.4 m/sec
2.	Volume of Grit Removed
Example: A grit channel removed 100 liters of grit during a
period when the total flow was 3,000 cubic meters.
How many liters of grit are removed per cubic me-
ter?
Unknown
(1/4 in)
= (6) (4)
= 24 ft
Area, sq ft = (Length, ft)(Width, ft)
= (36 ft) (24 ft)
= 864 sq ft
17.14 TYPICAL TREATMENT PLANT PROBLEMS
(METRIC SYSTEM)
This section contains the solutions to the problems in the
previous section using metric calculations. The conversion fac-
tors listed below will be helpful when switching from one sys-
tem to the other.
Known
Vol. of Grit = 100 liters
Vol. of Flow = 3,000 cu m
Volume of Grit, liters
Grit Removed,
liters/cu m
Grit Removed,
Lieu m
Volume of Flow, cu m
100 liters
3,000 cu m
= 0.033 Ucu m
17.141 Sedimentation Tanks and Clarifiers
Example: A circular clarifier handles a flow of 3,400 cu
m/day. The clarifier is 15 meters in diameter and
ft
X
0.3048
= m
loading rate, and weir overflow rate.
m
X
3.281
= ft
Known Unknown
lb
X
0.454
= kg
Flow = 3,400 cu m/day Detention Time, hours
kg

2.205
Diameter =15m Surface Loading,
X
= lb
cu m/day/sq m
gal
X
3.785
= liters
Depth = 2.5 m Weir Overflow,
liter
X
0.264
= gal
cu m/day/m
MGD
X
3,785
= cu m/day
DETENTION TIME
cu m/day
X
0.000264
= MGD
Detention Time, _ (Tank Volume, cu m)(24 hr/day)
GPM
X
0.063
= L/sec
',rs Flow, cu m/day
Usee
X
15.85
= GPM
Tank Volume, = (Area sq m)(Depth> m)
cu ft
X
0.02832
= cu m
Clarifer Area. = 0.785 (Diameter, m)2
sq m
cu m
X
35.315
= cu ft

1
kg
= 1 L
Clarifier Area, = 0 785 (Diameter, m)2

1
cu m
= 1,000 L
sq m = 0.785 (15 m)2

1
lb mass
= 0.4536 kg
= 176.7 sq m, or



= 180sq m

1
lb force
= 4.448 N

Tank Volume, cu m = (Area, sq m)(Depth, m)


Force
= (mass)(acceleration)
= (180 sq m)(2.5 m)

1
N
= (1 kg)(1 m/sec2)
= 450 cu m

-------
504 Treatment Plants
Detention Time,
hrs
_ (Tank Volume, cu m)(24 hr/day)
Flow, cu m/day
(450 cu m)(24 hr/day)
3,400 cu m/day
10,800
3,400
= 3.2 hr
SURFACE LOADING RATE
Surface Loading, cu m/day = Flow, cu m/day
sq m Area, sq m
= 3,400 cu m/day
180 sq m
= 18.9 cu m/day/sq m
WEIR OVERFLOW RATE
Weir Overflow, cu
m
Length of Weir, m
Weir Overflow. cu "***
m
Flow, cu m/day
Length of Weir, m
= 3.14 (Diameter, m)
= 3.14 (15 m)
= 47.1 m
_ Flow, cu m/day
Length of Weir, m
_ 3,400 cu m/day
47.1 m
= 72 cu m/day/m
17.142 Trickling Filters
Example: A flow of 4,300 cubic meters per day is applied to a
15-meter diameter trickling filter which is 1.2 meters
deep. The BOD of the wastewater applied to the
filter is 120 mg/L. Calculate the hydraulic and or-
ganic loadings on the filter.
Known
Flow = 4,300 cu m/day
Diameter = 15 m
Depth
BOD
= 1.2 m
= 120 mg/L
Unknown
Hydraulic Loading,
cu m/day/sq m
Organic Loading,
kg BOD/day
cu m
HYDRAUUC LOADING
Hydraulic Loading, cu = Flow, cu m/day
sq m Surface Area, sq m
Surface Area, sq m	= 0.785 (Diameter, m)2
= 0.785 (15 m)2
= 180 sq m
Hydraulic Loading, cu m/day _ Flow, cu m/day
sq m Surface Area, sq m
= 4,300 cu m/day
180 sq m
= 24 cu m/day/sq m
ORGANIC LOADING
Organic Loading, kg BOD/day
cu m
BOD Applied, kg/day
Volume of Media, cu m
BOD Applied,
kg/day
Volume of
Media, cu m
BOD Applied,
kg/day
= (BOD, ^)(Flow, cu m ) (1'°°° L) ( 1 kg )
L	day (1 cu m) (1,000,000 mg)
= (Surface Area, sq m)(Depth, m)
= (BOD, mg/L) (Flow, cu m ) t1-000 < 1 kg )
day (1 cu m) (1,000,000 mg)
= (120mg/L)(4,300J!iJ!L)il>C)00Al < 1 k9 )
Volume of
Media, cu m
day (1 cu m) (1,000,000 mg)
= 516 kg BOD/day
= (Surface Area, sq m)(Depth, m)
= (180 sq m)(1.2 m)
= 216 cu m
Organic Loading, k9 BOD/day = BOD Applied, kg/day
cu m Volume of Media, cu m
= 516 kg BOD/Day
216 cu m
= 2.4 kg BOD/day/cu m
17.143 Activated Sludge
Example: Lab results and flow rate for an activated sludge
plant are listed below under the known column. In-
formation helpful to the operator in controlling the
process is listed in the unknown column. The aerator
or aeration tank volume is 2,000 cu m.
Known
Mixed Liquor Suspended Solids (MLSS)
Mixed Liquor Volatile Content
Thirty-Minute Settleable Solids Test*
Primary Effluent BOD
Primary Effluent Suspended Solids
Flow Rate
Unknown
Kilograms of Solids in the Aerator
Sludge Volume Index, SVI
Kilograms of BOD Applied per Day to Aerator
Sludge Age, days
KILOGRAMS OF SOUDS IN AERATOR
Aerator = (MLSS, mg/L)(Tank Vol., cu m) (1,000L> < 1 k9 )
kg'	(1 cu m) (1,000,000 mg)
= (1800 mg/L) (2000 cu m) (1,00° L) L	Lk9 )
= 1,800 mg/L
= 76%
= 340 ml, or 17%
= 140 mg/L
= 110 mg/L
= 8,000 cu m/day
(1 cu m) (1,000,000 mg)
= 3,600 kg
SLUDGE VOLUME INDEX, SVI
sv, , (Settleable Solids, %) (10,000)
MLSS, mg/L
, (17)(10.000)
1,800
= 94
* Thirty-minute results obtained from 60-minute settleable solids test
using 2 liter cylinder.

-------
Arithmetic 505
KILOGRAMS OF BOD APPLIED PER DAY TO AERATOR
1 kg )
Aerator
Loading,
kg BOD/day
(P.E. BOD, mg'LXFlow,™!") <1'000L) L
day (1 cu m) (1,000,000 mg)
= (140 mg/L) (8,000 ^ J (1'000L) i	U5?	L
day (1 cu m) (1,000,000 mg)
= 1,120 kg BOD/day Applied to Aerator
SLUDGE AGE
Chapter 11, "Activated Sludge," and Chapter 16, "Labora-
tory Procedures and Chemistry," discuss the different methods
of calculating sludge age and the meaning of the results.
(MLSS, mgIL) (Tank Volume, cu m) O'QQQ O (	1^9	)_
Sludge = 	(1 cu m) (1,000,000 mg)
days (SS in P.E., mg/i_)(Flow. 9^_!IL) ^¦OOOL) 1
1 kg )
day (1 cu m) (1,000,000 mg)
Mixed Liquor Solids, kg (or Aerator Solids, kg)
Primary Effluent Solids, kg/day
3,600 kg
(110 mgIL) (8,000 ) (1,00° L) (
1 kg
day (1 cu m) (1,000,000 mg)
= 3,600 kg
880 kg/day
= 4.1 days
17.144 Sludge Digestion
1. C02 in Digester Gas
Example: The total volume of a 100 ml graduate used in the
C02 test is 127 ml. The volume of gas remaining in
the graduate after the C02 test was 82 ml. Find the
percent C02 in the digester gas.
Known
Total Volume
Gas Remaining
= 127 ml
= 82 ml
Unknown
Percent CO,
% CO = (Total Volume, ml - Gas Remaining, ml) inn%
Total Volume, ml
_ (127 ml - 82 ml)
127 ml
= 45 ml 100%
127 ml
= 35%
2. Volatile Acid/Alkalinity Relationship
Example: The volatile acids in a digester are 250 mgIL, and
the alkalinity is 1,750 mgIL. Find the volatile acidI
alkalinity relationship.
Known
Unknown
Volatile Acids = 250 mgIL Volatile AcidI
Alkalinity
Alkalinity	= 1750 mg/L
Volatile Acid/
Alkalinity
_ Volatile Acid, mgIL
Alkalinity, mg/L
_ 250 mg/L
1,750 mgIL
= .14
3. Volume Per Stroke of a Piston Pump
Example: Calculate the volume (in liters) pumped per stroke
(revolution) by a piston pump with a bore of 60 mil-
limeters and a stroke of 75 millimeters.
Known
Dia. of Piston
Length of Stroke
Cylinder Volume,
cu mm
Cylinder Volume,
liters
Unknown
= 60 mm Volume, liters
= 75 mm
= (Area, sq mm) (Length, mm)
= (0.785) (60 mm)2 (75 mm)
= 212,060 cu mm
212,060 cu mm (1,000 /./cu m)
(1,000 mm/m)3
- 0.21 liters, or volume pumped per
stroke is 0.21 liters.
The actual volume pumped per stroke will be slightly below
0.21 liters because the system is not 100 percent efficient.
4. Percent Reduction of Volatile Matter
Example: Find the percent reduction of volatile matter in a
digester if the percent volatile matter in the raw
sludge was 71 percent and the digested sludge was
composed of 53 percent volatile matter.
Unknown
Known
In, % VM in Raw Sludge
Out, % VM in Dig. Sludge
P =
(In - Out)
In - (In x Out) J
(.71 - .53)
.71 - (.71 x .53)
71%
53%
100%
P, % Reduction of VM
100%
.18
100%
.71 - .38
= — x 100%
.33
= .55 x 100%
= 55%
5. Digester Loading
Example: A digester with a volume of 700 cu m receives 900
kilograms of raw sludge per day with a volatile con-
tent of 70 percent.
Known
Unknown
Digester Volume = 700 cu m Digester Loading,
gm VM/day/cu m
Raw Sludge = 900 kg/day
Volatile Content = 70%
Volatile Matter
Added, kg/day
= (Raw Sludge, kg/day) (Volatile, %)
= (900 kg/day) (0.70)
= 630 kg/day
Digester Loading, = (Volatile Matter Added, kg/day) (1,000 gm)
gm VM/day/cu m
(Digester Volume, cu m) (1 kg)
„ (900 kg/day) (1,000 gm)
(700 cu m) (1 kg)
= 1,290 gm VM/day/cu m

-------
506 Treatment Plants
17.145 Ponds
Example: To calculate the different loadings on a pond, the
information listed under known must be available.
Known
Average Depth	= 1.2 m
Average Width	= 120 m
Average Length = 180 m
Flow	= 2,000 cu m/day
BOD	= 150 mgIL
Population	= 5,000 persons
Unknown
Detention time, days
Population Loading, persons/ sq m
Hydraulic Load, cm/day
Organic Load, gm BOD/day/sq m
DETENTION TIME
Detention Time, days
Pond Area, sq m
Pond Volume, cu m
Flow Rate, cu m/day
Detention Time, days
Pond Volume, cu m
Flow Rate, cu m/day
= (Average Width, m) (Average Length, m)
= (120 m) (180 m)
= 21,600 sq m
= (Area, sq m) (Depth, m)
= (21,600 sq m) (1.2 m)
= 25,920 cu m
= 2,000 cu m/day
Pond Volume, cu m
Flow Rate, cu m/day
_ 25,920 cu m
2,000 cu m/day
= 13.0 days
POPULATION LOADING
Population Loading, = Population Served, persons
persons/sq m	Pond Area, sq m
_ 5,000 persons
21,600 sq m
= 0.23 persons/sq m
HYDRAULIC LOADING
Hydraulic Loading, = Depth of Pond, m (100 cm/m)
cm/day	Detention Time, days
_ (1.2 m) (100 cm/m)
13.0 days
= 9.2 cm/day
ORGANIC LOADING
Organic Loading,
gm BOD/day/sq m
(BOD, mgIL) (Flow.f^L)	' 1 °m »
day (1cum) (1,000 mg)
Area, sq m
cu m. (1,000 L) ( 1 gm )
(150 mgIL) (2,000
day (1 cu m) (1,000 mg)
21.600 sq m
= 300,000 gm BOD/Day
21,600 sq m
= 13.9 gm BOD/day/sq m
17.146	Chlorination
1.	Chlorine Demand
Example: Determine the chlorine demand* of an effluent if the
chlorine dose is 10.0 mgIL and the chlorine residual
is 1.1 mg IL.
Known	Unknown
Chlorine Dose = 10.0 mg/L Chlorine Demand, mg/L
Chlorine Residual = 1.1 mg/L
Chlorine
Demand, = Chlor. Dose, mg/L - Chlor. Residual, mg/L
mg/L
= 10.0 mg/L -1.1 mg/L
= 8.9 mg/L
2.	Chlorine Feed Rate
Example: To maintain a satisfactory chlorine residual in a
plant effluent, the chlorine dose must be 10 mg/L
when the flow is 1,400 cu m/day. Determine the
chlorinator setting (feed rate) in kilograms per day.
Known	Unknown
Dose =10 mg/L	Chlorinator Setting, kg/day
Flow = 1,400 cu m/day
°RtoateekX - <*»•¦ (Flow,£!L!!l)	( 1* )
9/ y	day (1 cu m) (1,000,000 mfl)
= (10 mg/L) (i*nncu m) (1,000 L) < 1 k9 >
day (1 cu m) (1,000,000 mg)
= 14 kg/day
17.147	Laboratory Results
1.	Dissolved Oxygen (DO) Saturation, Percent
Example: The dissolved oxygen in a receiving water was 10.3
mg/L when the temperature was 10°C (Saturation
DO = 11.3 mg/L.). Determine the percent DO sat-
uration.
Known	Unknown
Do of Sample = 10.3 mg/L DO Saturation, %
Do at 100% Sat. = 11.3 mg/L
DO Satu- = DO of Sample, mg/L x 1Q0%
ra,ion' % DO at 100% Saturation, mg/L
= 10 3 m^L x 100%
11.3 mg/L
= 91.2%
2.	Biochemical Oxygen Demand (BOD)
Example: Laboratory results are listed under known.
Known	Unknown
Bod Bottle Volume = 300 ml BOD, mg/L
Sample Volume = 12 ml
Initial DO of
Diluted Sample = 8.0 mg/L
DO of Sample and
Dilution After 5-Day
Incubation Period = 4.0 mg/L
* "Standard Methods" uses the term chlorine demand' when refer-
ring to stabilized water such as a domestic water supply and the
term 'chlorination requirement' when referring to wastewater.

-------
Arithmetic 507
BOD, _ I Initial DO of
mgIL I Diluted Sample,
|_mg/i.
DO of Diluted
Sample After
5-Day Incuba-
tion, mgIL
= (8.0 mgIL - 4.0 mg IL) 1" 300 ml 1
L 12 ml J
]t
BOD Btl. Vol., ml
Sample Vol., ml
= 100 mgIL
17.148	Efficiency of Plant or Treatment Processes
Example: The influent BOD to a treatment plant is 200 mgIL,
and the effluent BOD Is 20 mgIL. What is the BOD
removal efficiency of the plant?
Known	Unknown
Influent BOD = 200 mgIL Plant Efficiency, %
Effluent BOD = 20 mgIL
Efficiency, % = (|n~0ut) iqq%
In
= (200 mgIL - 20 mgIL) 10Q%
200 mgIL
= 180 m^L 100%
200 mgIL
= 90%
17.149	Blueprint Reading
Example: A set of blueprints for a treatment plant has a scale
of 1:100. On the prints, the laboratory dimensions
were measured and found to be 70 mm wide and
100 mm long. What is the floor area of the labora-
tory?
Known	Unknown
Scale
Length
Width
= 1:100
= 100 mm
= 70 mm
Area, sq m
Area, sq m = (Length, m)(Width, m)
Find actual length and width in meters.
1	_ 100 mm
100
Length, m
Length, m = 100 mm
= 10 m
1	_ 70 mm
(100) (1 m)
(1) (1,000 mm)
100
Width, m
Width, m = (70 mm) (100)
o7
= 7 m
(1 m)
(1,000 mm)
Area, sq ft = (Length, m)(Width, m)
= (10 m)(7 m)
= 70 sq m
17.15 SUMMARY OF FORMULAS (ENGLISH SYSTEM)
17.150 Length
LENGTH OF CLARIFIER WEIR or circumference of a
circle:
Length, ft =3.14 (Diameter, ft)
17.151	Area
RECTANGLE:
Area, sq ft = (Length, ft)(Width, ft)
TRIANGLE:
Area, sq ft = (1/2)(Base, ft)(Height, ft)
CIRCLE:
Area, sq ft = 0.785 (Diameter, ft)2
CYLINDER (wall):
Area, sq ft =3.14 (Diameter, ft)(Height, ft)
SPHERE:
Area, sq ft = 3.14 (Diameter, ft)2
17.152	Volume
RECTANGLE:
Volume, cu ft = (Length, ft)(Width, ft)(Height, ft)
CYLINDER:
Volume, cu ft = 0.785 (Diameter, ft)2 (Height, ft)
SPHERE:
Volume, cu ft = 0.524 (Diameter, ft)3
17.153	Velocity
Velocity, _ Distance Traveled, ft
ft/sec
Time, sec
or
Velocity, _ Flow Rate, cu ft/sec
ft/sec
Cross-Sectional Area, sq ft
17.154	Sedimentation Tanks and Clarifiers
Detention _ (Tank Volume, cu ft)(7.5 gal/cu ft)(24 hr/day)
Time- hre	Flow, gal/day
Surface
Loading	_ Flow, gal/day
gJJsqft Area's^,t
Weir
Overflow	= Flow, gal/day
gpd/ft LenQth of Weir'
17.155	Trickling Filters
Hydraulic Loading, gpd/sq ft = ^toW| 9a^daV—
Surface Area, sq ft
Organic Loading, »>s BOO/day _ BOD Applied, lbs/day
1000 cu ft	Volume of Media, 1000 cu ft
17.156	Activated Sludge
Solids in	= (MLSS, mg/L)(Tank Vol., MG)(8.34 lb/gal)
Aerator, lbs
where MLSS = Mixed Liquor Suspended Solids
Aerator
Loading,	= (Primary Effl. BOD, mgIL)
lbs BOD/day	(Flow, MGD)(8.34 lb/gal)

-------
508 Treatment Plants
Sludge Volume Index (SVI)
(30-Minute Settleable Solids, %) (10,000)
MLSS, mgIL
30-Minute Settleable Solids, grams
100 ml
Sludge Density Index (SDI) =
100
svT
Sludge
Age,
days
(MLSS, mgIL) (Tank Vol., MG) (8.34 lb/gal)
(SS in Primary Effl., mgIL) (Flow, MGD) (8.34 lb/gal)
Mixed Liquor Solids, lbs, or Solids in Aerator, lbs
Primary Effluent Solids, lbs/day
NOTE: See Chapter 11, "Activated Sludge," or Chapter 16,
"Laboratory Procedures and Chemistry," for other
terms used instead of primary effluent solids.
17.157 Sludge Digestion
Digester
Gas, %
_ (Total Volume, ml - Gas Remaining, ml) 100o/o
Total Volume, ml
Reduction of Volatile Matter, %
[
In - Out
Digester, Loading,
lb VM/day/cu ft
17.158 Ponds
Detention
Time, days
In - In x Out
Volatile Matter Added, lb/day
Digester Volume, cu ft
Pond Volume, ac-ft
]
100%
Population
Loading,
persons/ac
Hydraulic
Loading,
in/day
Organic
Loading,
lb BOD/day/ac
Flow Rate, ac-ft/day
_ Population Served, persons
Pond Area, acres
= Depth of Pond, inches
Detention Time, days
(BOD, mg/L)(Flow, MGD)(8.34 lb/gal)
Area, acre
17.159 Other Formulas
17.1590 Chlorlnation
Chlorine Demand, mgIL
-- Chlorine - Chlorine
Dose, mg IL Residual, mgIL
Chlorine Feed
Rate, lbs/day
(Dose, mg/L)(Flow, MGD)(8.34 lb/gal)
17.1591 Laboratory Results
™ e . .• o/ DO of Sample, mgIL x 100%
DO Saturation, % =	--			—
DO at 100% Saturation, mgIL
BOD,
mgIL
[
Initltal DO of
Diluted Sample,
mg/L
DO of Diluted
Sample After
' 5-Day Incuba-
tion, mgIL
][
BOD Bottle Vol., ml
Sample Vol., ml
]
17.1592 Efficiency of Plant or Treatment Process
Efficiency, % = 
(3960)(Ep)
Motor, HP = 
-------
Arithmetic 509
Weir
Overflow _ Flow, m/day
Rate,
cu m/day
m
Length of Weir, m
17.165 Trickling Filters
Hydraulic Loading, cu m/day = Flow' cu m/day
sq m Surface Area, sq m
Organic | n^ing k9 BOD/day = BOD Applied, kg/day
cu m	Volume of Media, cu m
17.166 Activated Sludge
(MLSS, mg/L)(Tank Vol., cu m)
(1.0001.) ( 1 kg )
(1 cu m) (1,000,000 mg)
where MLSS = Mixed Liquor Suspended Solids
Solids in
Aerator, kg
Aerator
Loading,
kg BOD/day
(P.E. BOD, mg//.) (Flow,
cu m
day
Sludge Volume Index (SVI)
(1,000 L)( 1kg )
(1 cu m) (1,000,000 mg)
(30-Minute Settleable Solids, %) (10,000)
MLSS, mg/L
30-Minute Settleable Solids, grams
100 ml
Sludge Density Index (SDI)
100
svT
Sludge
Age.
days
(MLSS, mg/L)(Tank Vol., cu m)(1|OOOL) ( 1 kg
)
(1 cu m) (1,000,000 mg)
(SS in P.E., mg/L)
(Flow.f^Il)11'000 L) <
day
)
(1 cu m) (1,000,000 mg)
NOTE: See Chapter 11, "Activated Sludge," or Chapter 16,
"Laboratory Procedures and Chemistry," for other
terms used instead of primary effluent solids.
17.167 Sludge Digestion
(Total Volume, ml - Gas Remaining, ml)
COz in
Digester
Gas, %
Total Volume, ml
100%
Reduction of Volatile Matter, % = I 	iTl	2^!	 I 100%
L In-In x Out J
Digester,
Loading, _ (Volatile Matter Added, kg/day)(1,000 gm)
gm VM/ (Digester Volume, cu m)	(1 kg)
day/cu m
17.168 Ponds
Detention
Time, days
Population
Loading,
persons/sq m
Hydraulic
Loading,
cm/day
_ Pond Volume, cu m
Flow Rate, cu m/day
= Population Served, persons
Pond Area, sq m
_ Depth of Pond, m (100 cm/m)
Detention Time, days
= (BOD, mg/L) (Flow, cu m )
day
Organic
Loading,
gm BOD/
day/sq m
17.169 Other Formulas
17.1690 Chlorlnation
(1,000 L) ( 1 gm )
(1 cu m) (1,000 mg)
Area, sq m
Chlorine Demand, mg/L
Chlorine - Chlorine
Dose, mgIL Residual, mg/L
CRrnke;dr - <*>»¦ mg/L) (Flow, (ijOOj) ( 1*9 )
'	day (1 cu m) (1,000,000 mg)
17.1691 Laboratory Results
DO Saturation, % » DO of Sample, mg/L x 100%
DO at 100% Saturation, mg/L
BOD,
mg/L
G
DO of Diluted
Initial DO of Sample After
Diluted Sample," 5-Day Incuba-
mgIL	tion, mg/L
]I
BOD Bottle Vol., ml
Sample Vol., ml
17.1692 Efficiency of Plant or Treatment Process
Efficiency, %
(in - Out) 100%
In
17.1693 Pumps
In the Metric system, power calculations can be tricky be-
cause Force = Mass x Acceleration; or F, kg = Mass, kg x
9.807 where 9.807 is the force of gravity on the mass. In the
equations in this section, W means watts and is equal to 1 kg
force - meter per second.
Water, Watts = (Flow, liters/sec)(1.0 kg/L)(9.807)(H, m)
Brake, Watts = (Row. llters/sec)(1.0 kg/L)(9.807)(H, m)
Ep
Motor, watts = (Flow- llters^sec)(1.0 kg/L)(9.807)(H, m)
(Ep)(Em)
If the flow was given in cubic meters per day, use the follow-
ing procedure to convert the flow to liters per second.
Flow litefs = (Flow' cu m) (1,000 L)(1 day) (1 hr) (1 min)
sec	day (1 cu m)(24 hr)(60 mm)(60 sec)
_ Flow, cu m/day
8&4
17.17 CONVERSION TABLES
Tables in this section were taken from WATER AND
WASTEWATER ENGINEERING, Volume 1, WATER SUPPLY
AND WASTEWATER REMOVAL by G.M. Fair, J.C. Geyer,
and D.A. Okun, John Wiley & Sons, Inc., New York, 1966.
Price $19.95. The tables are also found in Volume 2, WATER
PURIFICATION AND WASTEWATER TREATMENT AND DIS-
POSAL, 1968. Price $22.00
The American and English weights and measures referred
to in this book are alike except for the gallon. The United States
gallon is employed. The United States billion, which equals
1000 million, is also employed.

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510 Treatment Plants
Miles
Yards
LENGTH
Feet
Inches
Centimeters
1
1760
5280
—
—
—
1
3
36
91.44
—
—
1
12
30.48
—
—
—
1
2.540

1 m = 100 cm = 3.281 ft
= 39.37 in

Square
Miles
Acres
AREA
Square
Feet
Square
Inches
Square
Centimeters
1
640
—
—
—
—
1
43,560
—
—
—
—
1
144
929.0
—
—
—
1
6.452

1
sq m = 10.76 sq ft

Cubic
Feet
Imperial
Gallons
VOLUME
U.S.
Gallons
Cubic
Inches
Liters
1
6.23
7.481
1728
28.32
—
1
1.2
277.4
4.536
—
—
1
231
3.785
—
—
—
57.75
0.946
—
—
—
61.02
1

1 cu m
= 35.31 cu ft =
264.2 gal

1 Imperial (UK) gal weighs 10 lb	1 US gal weighs 8.34 lb
1 cu ft of water weighs 62.43 lb	1 cu m weighs 2283 lb
1 cu m = 10 L and weighs 1000 kg
Miles per
Hour
VELOCITY
Feet per Inches per
Second Minute
Centimeters
per Second
Kilometers
per Hour
1
1.467 1056
—
1.609
—
1 720
30.48
—
—
— 1
0.423
—
Days
TIME
Hours Minutes
Seconds
1
24 1440
86,400
—
1
60
3.600
—
—
1
60
Tons
WEIGHT
Pounds Grams
Grains
Metric Tons
1
2000 —
—
0.9078
—
1 454
7000
—
—
— 1
15.43
—

1 long ton - 2240 lb


1 ppm = 1 mgIL = 8.34 lb per MG

DISCHARGE
Cubic Feat per Million Gallons
Second Daily
Gallons per
Minute
1
0.6463

448.8
1.547
1
1 In per hour per acre =
1 cu m/sec = 22.83 MGD
1.008 cfs
= 35.32 cfs
694.4
PRESSURE
Pounds per
Square Inch	Feet of Water	Inches of Mercury
1	2.307	2.056
0.4335	1	0.8825
0.4912	1.133	1
1 atm = 14.70 psia = 29.92 in. Hg =
33.93 ft water = 76.0 cm Hg

POWER

Kilowatts
Foot-Pounds
Horsepower per second
Kitogram-
Meters per
Second
1
1.341 737.6
102.0
0.7457
1 550
76.04

WORK AND ENERGY

Kilowatt-Hours
Horsepower-
Hours
British Thermal
Units
1
1.341
3412
0.7457
1
2544
TEMPERATURE
Degree Fahrenheit = 32 + .?. x Degrees Centigrade
5
0 5 10 15 20 25 30 35 40 45 50 55 60 C
32 41 50 59 68 77 86 95 104 113 122 131 140 F
DENSITY OF WATER
	 1 gram/cm3 = 62.43 Ib/cu ft
17.18 ADDITIONAL READING
1.	MOP 11, Appendix II,* "Conversion Factors for Units of
Measure."
2.	NEW YORK MANUAL, pages 183-190 and 215-219.
3.	TEXAS MANUAL, pages 588-608.
4.	MATHEMATICS FOR OPERATORS OF WATER POLLU-
TION CONTROL PLANTS. Obtain from Secretary-
Treasurer, California Water Pollution Control Association,
4876 Paseo de Vega, Irvine, California 92715. Price $5.30
to members of CWPCA; $9.54 to others.
* Depends on Edition

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Arithmetic 511
5.	MATHEMATICS FOR WATER AND WASTEWATER
TREATMENT PLANT OPERATORS, Book 1 — Fundamen-
tals and Book 2 — Advanced by Joanne Kirkpatrick, pub-
lished by Ann Arbor Science Publishers, Inc., P.O. Box
1425, Ann Arbor, Michigan 48106. Price $15.00 for each
book. $20.00 if you buy both books at once.
6.	STUDYBOOK FOR WASTEWATER OPERATOR CER-
TIFICATION, Water Pollution Control Federation, 2626
Pennsylvania Avenue, N.W., Washington, D.C. 20037.
Price $3.00 members, $6.00 to others.
7.	UNITS OF EXPRESSION FOR WASTEWATER TREAT-
MENT, Water Pollution Control Federation, 2626 Pennsyl-
vania Avenue, N.W., Washington, D.C. 20037. Price $2.00
members, $4.00 to others.
8.	AMERICAN NATIONAL STANDARD METRIC PRACTICE,
American National Standards Institute, 1430 Broadway,
New York, New York 10008. Price $4.00.
OBJECTIVE TEST PROCEDURE
1.	Work the problems in your notebook. Be neat and orderly
so that your work may be followed and checked.
2.	Mark your answers on the answer sheet.
3. Mail the answer sheet to your Program Director.
You may refer to the chapter for formulas and conversion
factors.
OBJECTIVE TEST
Chapter 17. BASIC ARITHMETIC AND TREATMENT
PLANT PROBLEMS
Please write your name and mark the correct answers on the
answer sheet as directed at the end of Chapter 1. There will be
only one answer to each question. If necessary, select the
closest answer.
1. Both English and Metric units are used to calculate the
loadings on wastewater treatment processes.
1.	True
2.	False
2.	Pressures at the suction and discharge of a pump are
commonly measured in feet of head.
1.	True
2.	False
3.	Static head is a measure of the flow velocity of water.
1.	True
2.

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512 Treatment Plants
4.	Never empty a tank during periods of high ground water.
1.	True
2.	False
5.	Surface loading is another name for pressure at the sur-
face.
1.	True
2.	False
6.	Significant figures refer to the number of zeros before or
after a number.
1.	True
2.	False
7.	One meter is shorter than one yard.
1.	True
2.	False
8.	One liter is smaller than one gallon.
1.	True
2.	False
9.	In the Metric system, the U.S. Government spells meter
this way and the Water Pollution Control Federation spells
metre this way.
1.	True
2.	False
10.	The Metric system requires the use of both the kilogram
force and the kilogram mass.
1.	True
2.	False
Use the following information to answer questions 11 and
12. A rectangular sedimentation tank is 30 feet wide, 75 feet
long, and 9 feet deep. The flow is 1.8 MGD.
11.	What is the detention time?
1.	0.5 hr
2.	1.0 hr
3.	2.0 hr
4.	2.5 hr
5.	3.5 hr
12.	What is the surface loading rate?
14. What is the organic loading?
1.	120 lb BOD/day/1000 cu ft
2.	150 lb BOD/day/1000 cu ft
3.	200 lb BOD/day/1000 cu ft
4.	400 lb BOD/day/1000 cu ft
5.	480 lb BOD/day/1000 cu ft
Use the following information about an activated sludge
plant to answer questions 15 and 16.
Mixed Liquor Suspended Solids (MLSS)
Mixed Liquor Volatile Content
Thirty-Minute Settleable Solids Test
Primary Effluent BOD
Primary Effluent Suspended Solids
Flow Rate
Aeration Tank Volume
*2 liter cylinder
= 2200 mg/L
= 71%
= 420 ml* or 21%
= 105 mg/L
= 135 mg/L
= 2.5 MGD
= 80,000 cu ft
15.
500 gpd/sq ft
600 gpd/sq ft
650 gpd/sq ft
750 gpd/sq ft
800 gpd/sq ft
Use the following information to answer questions 13 and
14. A 75-ft diameter trickling filter receives a flow of 2.2 MGD
with a BOD of 115 mg/L. The filter is 4 feet deep.
13. What is the hydraulic loading?
1.	500 gpd/sq ft
2.	600 gpd/sq ft
3.	750 gpd/sq ft
4.	800 gpd/sq ft
5.	1000 gpd/sq ft
How many pounds of solids are in the aeration tank?
1.	1,300 lbs
2.	1,600 lbs
3.	2,200 lbs
4.	9,200 lbs
5.	11,000 lbs
16. What is the aeration tank loading?
1.	1,300 lbs BOD/day
2.	1,600 lbs BOD/day
3.	2,200 lbs BOD/day
4.	9,200 lbs BOD/day
5.	11,000 lbs BOD/day
17. Raw sludge pumped to a digester was 74 percent volatile
matter, and the digester sludge was 52 percent volatile
matter. Calculate the percent reduction of volatile matter.
1.	50%
2.	55%
3.	59%
4.	60%
5.	62%
Use the following information to answer questions 18,19, 20
and 21. A waste treatment pond is 245 ft wide, 385 ft long, and
4.5 ft deep. The inflow is 0.108 MGD, has a BOD of 170 mg/L,
and serves a population of 975 people.
18.	What is the detention time of the pond?
1.	22 days
2.	25 days
3.	30 days
4.	35 days
5.	40 days
19.	What is the population loading on the pond?
1.	450 persons/acre
2.	600 persons/acre
3.	750 persons/acre
4.	800 persons/acre
5.	900 persons/acre

-------
Arithmetic 513
20.	What is the hydraulic loading?
1.	1.80 in/day
2.	2.00 in/day
3.	2.20 in/day
4.	2.50 in/day
5.	2.80 in/day
21.	What is the organic loading?
1.	50 lb BOD/day/ac
2.	70 lb BOD/day/ac
3.	80 lb BOD/day/ac
4.	90 lb BOD/day/ac
5.	95 lb BOD/day/ac
22.	Determine the chlorine feed rate for a chlorinator when the
dose is 14 mg/L and the flow is 0.275 MGD.
1.	25 lbs/day
2.	28 lbs/day
3.	30 lbs/day
4.	32 lbs/day
5.	35 lbs/day
23.	Calculate the BOD of a 3 ml sample in a 300 ml BOD
bottle if the initial DO of diluted sample was 8.3 mg/L and
the DO of sample and dilution was 3.4 mg/L after the
5-day incubation period.
1.	100 mg/L
2.	200 mg/L
3.	300 mg/L
4.	400 mg/L
5.	500 mg/L
24.	The influent suspended solids to an activated sludge plant
is 255 mg/L, and the effluent suspended solids is 13 mg/L.
What is the suspended solids removal efficiency for the
plant?
1.	85%
2.	90%
3.	93%
4.	95%
5.	98%
26. The discharge pressure gage on a pump reads 15 psi.
This is equivalent to how many feet of water or feet of
head?
1.	7ft
2.	10 ft
3.	25 ft
4.	35 ft
5.	50 ft
27.	100 mg/L is the same as:
1.	100%
2.	10%
3.	1%
4.	0.1%
5.	0.01%
28.	How many cubic meters are there in a 150 mm diameter
pipe that is 1.5 kilometers long?
1.	22.5 cum
2.	26.5 cu m
3.	596 cu m
4.	22,500 cu m
5.	26,500 cu m
29.	What is the power in kilowatts required to pump two cubic
meters per second against a TDH of 20 meters if the wire
to water efficiency is 50 percent?
1.	8.2 kW
2.	20.0 kW
3.	80.0 kW
4.	196.0 kW
5.	785.0 kW
30. In the "soft" metric system, a 12-inch diameter pipe is the
same as a	millimeter diameter pipe.
1.	47.2
2.	48
3.	240
4.	300
5.	304.8
25. A pump is capable of delivering 5 horsepower to water	END OF OBJECTIVE TEST
being pumped against a 40-ft head. Estimate the flow of
water being pumped.
1.	50 gpm
2.	100 gpm
3.	150 gpm
4.	300 gpm
5.	500 gpm

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CHAPTER 18
ANALYSIS AND PRESENTATION OF DATA
Kenneth Kerri

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516 Treatment Plants
TABLE OF CONTENTS
Chapter 18. Analysis and Presentation of Data
Page
OBJECTIVES	517
LESSON 1
18.0	Need for Analyzing and Presenting Data 	518
18.1	Causes of Variations in Results 	518
18.10	Water or Material Being Examined	518
18.11	Sampling 	518
18.12	Testing	518
18.2	Manometer and Gage Reading	519
18.3	Chart Reading	520
18.4	Average or Arithmetic Mean 	520
18.5	Range of Values	521
18.6	Median and Mode 	521
18.7	Geometric Mean	522
18.70	Log Probability Paper 	522
18.71	Logarithms	523
18.72	Electronic Calculators	524
18.73	Geometric Mean Table	524
18.74	Example Problem	525
18.8	Moving Averages	528
LESSON 2
18.9	Graphs and Charts 	530
18.90	Bar Graphs	530
18.91	Trends 	531
18.92	Summary	531
18.93	Chart Preparation	533
18.94	COD to BOD Curves	533
18.10	Variance and Standard Deviation	535
18.11	Metric Calculations 	539
18.12	Summary	539
18.13	Additional Reading	540

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Data Analysis 517
OBJECTIVES
Chapter 18. ANALYSIS AND PRESENTATION OF DATA
Following completion of Chapter 18, you should be able to:
1.	Identify causes of the variations in results.
2.	Read manometers, gages and charts.
3.	Analyze and present data using
a.	Charts and graphs
b.	Tables
c.	Numbers
4.	Calculate arithmetic mean, range, median, mode, geomet-
ric mean, moving average, variance and standard devia-
tion.

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518 Treatment Plants
CHAPTER 18. ANALYSIS AND PRESENTATION OF DATA
(Lesson 1 of 2 Lessons)
18.0	NEED FOR ANALYZING AND PRESENTING DATA
Collection of data without analysis, interpretation, and use of
results is a waste of time and money. This chapter will attempt
to provide you with simple, easy methods to analyze data. To
show you how to make the results of your testing meaningful
and easily interpreted, sections on DATA PRESENTATION
also are included. Many times your supervisor can understand
what is happening in your plant or why you need a budget
increase if you can show charts indicating trends or changes in
plant operation or treatment process efficiencies.
Whether samples are collected, analyzed, interpreted, and
used by the same person or a different person performs each
task, every job is equally important if the application of results
is to be effective. When running lab tests the samples must be
REPRESENTATIVE,1 Persons reviewing and interpreting lab
results assume the tests were performed in a careful, pre-
scribed manner and the results are accurate. Operators apply-
ing the interpretation of lab results to operational controls rely
on proper interpretation to insure effective adjustments in the
treatment processes.
All samples collected and analyzed must be needed by
someone. Numbers from test results provide an accurate de-
scription or indication of the quantity of work completed or to be
completed. Mathematical analysis of data is a means to esti-
mate how well your test results can be repeated on a given
sample (quality control) or how much a group of samples vary
(another form of quality control). Presentation of data in tables,
graphs, or charts makes the information more usable by illus-
trating trends, variations, and significant changes.
18.1	CAUSES OF VARIATIONS IN RESULTS
When you collect samples of wastewater or receiving water
and measure their characteristics (for instance, temperature,
pH, BOD), your results will be affected by several factors.
Three principal factors which must be taken into account, no
matter where the sample is taken — influent raw wastewater,
treatment process influent or effluent, receiving waters — are:
1.	Actual variations in the characteristics of the water or mate-
rial being examined,
2.	Sampling procedures, and
3.	Testing or analytical procedures.
18.10 Water or Material Being Examined
The properties or characteristics of the wastewater or receiv-
ing water are what you are attempting to measure, such as
temperature, pH, or BOD. These and many other water quality
indicators vary continuously depending on what is being dis-
charged into a wastewater collection system (sewerage sys-
tem), the effectiveness of treatment processes, and the re-
sponse of the receiving waters and THEIR changing charac-
teristics. Your objective is to describe the characteristics of the
wastewater or receiving water being sampled in terms of aver-
age values and also to give an indication of variation or spread
of results from the average values.
18.11 Sampling
Characteristics of a sample can vary if you do not always
sample at the same location or during the same time of day. If
you observe the flow of wastewater in a channel, you can see
the differences in characteristics at various depths, differences
between flow in the middle and edge of a pipe or channel, and
also differences above or below a bend.
After a sample has been collected in a sampling jar or bottle,
heavy material may settle to the bottom and the jar must be
mixed before the sample is tested. Also, if the sample is not
analyzed immediately, its characteristics can undergo chemi-
cal or biological changes unless the sample is treated and
stored properly following collection.
/
n

18.12 Testing
The results from two identical samples can differ depending
on the analyzing apparatus and the operator conducting the
measurement. Fluctuations in voltage can cause changes in
instrument readings, and different individuals may titrate to
1 Representative Sample. A portion of material or water Identical in content to that In the larger body ot material or water being sampled.

-------
Data Analysis 519
slightly different end points. Using reagents from different bot-
tles, filter paper from different packages, or different pieces of
equipment that were not calibrated identically or were not
warmed up during the same time period can cause differences
in test results. Variations in test results may be caused by
omitting a step in the lab procedure, and interfering substances
can cause testing errors.
Your objective is to reduce or eliminate sampling and testing
errors as much as possible so you can obtain an accurate
description of the water being sampled.
QUESTIONS
Write your answers in a notebook and then compare your
answers with those on page 541.
18.1	A What three major factors can cause variations in lab
test results?
18.1B Why should most samples be tested immediately by
the lab?
18.2	MANOMETER AND GAGE READING
Manometers and gages are installed in wastewater treat-
ment plants to measure pressures and pressure differences.
Both types of instruments should be calibrated and zeroed
before using. Calibration and zeroing of any instrument means
periodic checking of the instrument against a known standard
to be sure the installed instrument reads properly. Manometers
and gages can be zeroed in by making sure the instruments
read zero when no pressure is being applied to the manometer
or gage. If the reading is not zero, then the scales should be
adjusted according to manufacturer's recommendations.
To read a manometer, note the scale reading opposite the
MENISCUS.2 This reading may have to be converted from
inches of mercury to head in feet of water, pressure in psi, or
flow in GPM, depending on the use of the manometer.
QUESTIONS
Write your answers in a notebook and then compare your
answers with those on page 541.
18.2A Why must instruments be periodically calibrated and
zeroed?
18.2B If the gage shown on the right under TYPICAL GAGE
READINGS indicated a pressure of 2 psi, what would
be the pressure head in feet of water?
TYPICAL MANOMETER READINGS
MANOMETER A MANOMETER B
MANOMETER A
reads 3 inches
of water
MANOMETER B
reads 3 inches
of mercury
Gage readings are read directly rrom a scale oenina a gage
pointer and the units must be recorded. Sometimes a gage will
have two scales and care must be taken to be sure the proper
scale reading and units are recorded. Gage readings may
have to be converted to more convenient numbers.
TYPICAL GAGE READINGS
GAGE READS
6 ft of water
or
2.6 psi
Water (inches)
— 2
Mercury (inches)
-4

mf
m

2 Meniscus (meh-NIS-cuss). The curved top of a column of liquid (water, oil, mercury) in a small tube. When the liquid wets the sides of the
container (as with water), the curve forms a valley. When the confining sides are not wetted (as with mercury), the curve forms a hill or upward
bulge.
	MENISCUS		
Water	Mercury
(Read Bottom)	(Read Top)
tnn




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520 Treatment Plants
18.3 CHART READING
Before data can be analyzed and presented, frequently it
must be reduced to or tabulated in a usable form. Today, more
and more, data are being recorded on a continuous basis on
strip charts and circular charts.
For instance, flow data are sometimes recorded in depths of
flow in inches or feet through a Parshall flume. Some recorders
will also convert the depth to a flow rate, such as MGD. To
compile or tabulate data from continuous charts, select an ap-
propriate time interval, such as a few hours (Fig. 18.1). Pre-
pare a table (Table 18.1) with a column for (1) the time and (2)
the value you read from the chart. A third column (3) may be
necessary if you have to convert a depth of flow to a flow rate
(MGD). Conversion charts from depth of flow to flow rate in
MGD are provided by the manufacturer of a flow meter.
When reading manometers, gages, and charts, care must
be taken to be sure the correct number is read and properly
recorded.
J	l	I	I	I	' '
6 a.m. 8 a m 10 a.m. Noon
TIME. HR.
Fig. 18.1 Strip chart flow depth
TABLE 18.1 TABULATION OF DEPTHS AND FLOWS
FROM THE STRIP CHART (FIG. 18.1)
(1)
(2)
(3)
Time
Depth
Flow3

(in.)
(MGD)
6 AM
12
0.61
8 AM
12V2
0.65
10 AM
13V2
0.74
12 NOON
14V2
0.84
18.4 AVERAGE OR ARITHMETIC MEAN
The word average in general refers to the "central tendency"
of measurements. This is a method of grouping measurements
and describing the results by using a single number. The cen-
tral tendency may be described by any one of five methods,
arithmetic mean (Section 18.4), range (Section 18.5), median
and mode (Section 18.6), and geometric mean (Section 18.7).
When you collect representative samples from a plant in-
fluent and measure a particular water quality indicator, such as
BOD, the results are not always the same. For example, you
might measure the BOD of a trickling filter influent to determine
the organic loading and find the BOD varying considerably
during a 6-day period. To calculate an expected daily organic
loading, the average or arithmetic mean daily BOD must be
calculated.
EXAMPLE 1.
The results of six BOD tests on a trickling filter influent from
composite (proportional) samples collected at daily intervals
during a 6-day period indicated the BOD to be 150 mg/L, 200
mg/L, 250 mg/L, 200 mg/L, 100 mg/L, and 120 mg/L. What is
the mean daily BOD?
PROCEDURE:
Add the six measurements and divide by six, the number of
measurements.
Sum of All
Mean BOD, _ Measurements, mg/L
m9/£"	Number of	DAY	BOD
Measurements	<|	15Q
_ 1020 mg/L	2	200
					3	250
6	4	200
= 170 mg/L	5	100
6	120
Sum = 1020
You have calculated the mean BOD by adding all BOD
measurements and dividing by the number of measurements.
The mean value of any other characteristic is calculated the
same way. For example, if you wanted to calculate a month's
mean daily flow into a plant, you would add up the daily flows
for the month and divide by the number of days in the month.
Hint:
Frequently, plant flows are recorded on an integrator or
TOTALIZER.* The flow during a particular time period can
be determined by obtaining the difference between the to-
talizer readings at the beginning and end of the time period.
EXAMPLE 2:
At the beginning of a month, a plant totalizer reads
103,628,457 gallons, and 30 days later you record the totalizer
value as 114,789,321 gallons. Calculate the mean daily flow
for the month.
STEP 1:
Find the total monthly flow.
Reading at the end of time period = 114,789,321 gals
Reading at start of time period = 103,628,457 gals
Total flow during month	= 11,160,864 gals
3 These figures would be obtained from the manufacturer's "conversion chart" for the particular flume or flow meter.
* Totalizer. A device that continuously sums or adds the flow into a plant in gallons or million gallons or some other unit of measurement.

-------
Data Analysis 521
STEP 2:
Calculate the mean daily flow, gal/day:
Mean Daily Flow,
gal/day
Sum of Flows, gal
Number of Days
(measurements)
11,160,864 gals
30 Days
= 372,029 gals/day
or
372,029 gals/day
1,000,000 gals/MG
= 0.372 MGD
Note:
The mean daily flow for the month also could be calculated
by adding the 30 daily flows during the month and dividing by
30. This approach can be used to check the results obtained
using the difference in the totalizer readings as shown above.
18.5 RANGE OF VALUES
You have seen how to evaluate lab results in terms of arith-
metic mean values. This does not give any indication as to
whether all of the data were close to the mean value or if there
was a considerable spread or dispersion of data. A useful
method of indicating the spread in results is the RANGE. The
range is obtained by subtracting the smallest measurement
from the largest one.
Range = Largest Value - Smallest Value
PROCEDURE:
STEP 1: Rank data by arranging observations in ascending
(increasing) or descending (decreasing) order, using
the data from EXAMPLE 1: 250, 200,200,150,120,
100.
STEP 2: Subtract the smallest (100) from the largest (250).
Largest	250 mg/L
Smallest	-100 mgIL
Answer:
Range of BOD, mg//. = 150 mg/L
Try another example to review the calculations for the mean
value and range, then you will be ready to study other ways of
describing the dispersion of data and the idea of graphical
presentation using this problem.
EXAMPLE 3:
The mean daily BOD for two weeks is given below. Calculate
the mean 2-week BOD and the range for these measurements.
DATA: 160, 155, 160, 160, 180, 165, 155, 170, 160, 165,
160 mgIL
155
160
Mean BOD,
mg/L
155, 150, 145, 160.
_ Sum of All Measurements, mg/L
Number of Measurements
= 2240 mg/L
14
160 mg/L for two weeks
160
14)2240
14
84
84
00
160
180
165
155
170
160
165
155
150
145
160
Range of
BOD, mg/L
2240 mg/L
= Largest BOD, mg/L - Smallest BOD, mg/L
= 180 mg/L - 145 mg/L	1 gg
= 35 mg/L for two weeks	-145
35
QUESTIONS
Write your answers in a notebook and then compare your
answers with those on page 541.
Mixed liquor samples were collected at the beginning, mid-
dle, and end ol an aeration tank and the solids concentrations
were 2138 mg/L, 1863 mg/L, and 1921 mg/L.
18.4A Calculate the mean mixed liquor concentration.
18.5A What is the range of these measurements?
18.6 MEDIAN AND MODE
Sometimes the mean value and range calculations are not
the best way to describe or analyze data. For example, fre-
quently when running multiple-tube coliform bacteria tests you
will obtain some extremely high MPNs (most probable number
of coliform group bacteria), especially after a rain, equipment
failure, or chlorine dosage mishap.
EXAMPLE: 4
DATA: MPN/100 ml = 240, 220, 240, 230, 240, 7200, 260,
250, 270,300, 250. Calculate average
MPN.

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522 Treatment Plants
PROCEDURE:
Determine sum of measurements.
Mean
MPN/100 ml
Sum of Measurements, MPN/100 ml
= 9700
11
= 882
Number of Measurements
882
11)9700
88
90
88
20
240
220
240
230
240
7200
260
250
270
300
250
Sum = 9700
Mean MPN = 882 Coliform Bacteria/100 ml. Note that this
value is greater than all of our measurements except the
largest one. For this reason, multiple-tube coliform results are
sometimes reported as a MEDIAN VALUE.
The MEDIAN is defined as the middle measurement when
the measurements are ranked in order of magnitude (size).
To plot data on probability paper, the probability or plotting
point of each measurement must be determined. The plotting
point is calculated from the following formula:
P =
m
x 100%
n + 1
where:
P is the probability (%) the measurement will not be exceeded,
n is the number or sum of measurements, and
m is the rank when the measurements are arranged in ascending or
increasing order.
Calculate the probability for each measurement used in
EXAMPLE 4. Use n = 11 because we have 11 measurements.
For 220 MNP/100 ml, rank m is 1.
P =
m
n + 1
1
x 100%
x 100%
11+1
= 8.3%
PROCEDURE:
Rank data in ascending or descending order.
Measurement: 220 230 240 240 240 250 250 260 270 300 7200
Rank:	1 23456789 10 11
Median
Measurement 6 is our middle measurement. Therefore, the
MEDIAN MPN/100 ml = 250, which better describes the usual
value of the measurements.
If you had only ten measurements (eliminate #11 of 7200),
the MEDIAN would fall between measurements 5 and 6 (240
and 250) and would be 245.
Another useful value is the MODE. The MODE is the mea-
surement that occurs most frequently. In our example, the
measurement 240 occurs three times, which is more than any
other. Therefore: MODE MPN/100 ml = 240.
An examination of the data in EXAMPLE 4 indicates that the
median and mode do a better job of describing or predicting
the MPN value we would expect than the mean calculation. For
this reason these terms are sometimes used to report data.
QUESTION
Write your answer in a notebook and then compare your
answer with the one on page 541.
18.6A The results of the SVI (Sludge Volume Index) test for
an activated sludge plant for one week were as fol-
lows: 120, 115, 120, 120,125,110,115. What are the
median and mode values for the SVI data?
18.7 GEOMETRIC MEAN
18.70 Log Probability Paper
There are other ways of reporting the results of coliform tests
in addition to those mentioned above. The GEOMETRIC
MEAN is sometimes used because all measurements are used
in the calculations, but an extreme value has a lesser influence
on the result. The easiest way to find the geometric mean is to
plot the results on log probability paper and read the geometric
mean on the paper.
For 230 MPN/100 ml, rank m is 2.
P =	?	x 100%
11 +1
= 16.7%
Repeat this procedure for all eleven measurements.
For our example:
Rank
Measurement
Probability
m
MPN/100 ml
%
1
220
8.3
2
230
16.7
3
240
25.0
4
240
33.3
5
240
41.7
6
250
50.0
7
250
58.3
8
260
66.7
9
270
75.0
10
300
83.3
11
7200
91.7
Plot the data as shown on Figure 18.2. To plot the data,
obtain a sheet of log or geometric probability paper. On the left
side, determine the MPN per 100 ml scale (100,1000,10,000).
Start at the left with an MPN of 220. Move horizontally across
to the right until you meet the vertical line with a probability of
8.3 percent. Make an "*" on the paper at this point. Take the
next MPN value of 230 and move horizontally across to the
right until you meet the vertical line with a probability of 16.7
percent. Make an on the paper at this point. Repeat this
procedure until all of the MPN values have been plotted.
To estimate the geometric mean from the data plotted on
Figure 18.2:
1.	Draw a straight line of best fit through the data points (all of
the "*").
2.	Draw a vertical line down the 50 percent line to where it
intersects with the line of best fit.
3.	From the intersection of the 50 percent line and the line of
best fit, draw a horizontal line to the scale representing the
measurements.

-------
Data Analysis 523
4. Read the Geometric Mean MPN = 265/100 ml. This value
essentially ignores the one high value of 7200 per 100 ml
and will be lower than any computation which includes the
7200 value.
18.71 Logarithms
A problem with determining the geometric means by plotting
data is that different operators may draw different lines of best
fit through the data, thus giving different geometric means.
This problem can be overcome by mathematically calculating
the geometric mean. To calculate the geometric mean, all of
the measurements must be converted to logarithms, the mean
of the logarithms (or "logs") is then found, and finally, this
mean is converted to the geometric mean.
The logarithm of a measurement is the sum of its charac-
teristic and mantissa. The CHARACTERISTIC is based on the
number of digits before or after the decimal point where the
first significant number appears. To calculate the characteristic
of a number 1.0 or larger, count the total number of digits to the
left of the decimal point and subtract one. (For example, the
characteristic of 2,450 is 4 - 1 or 3. The characteristic of 2.45
is 1 - 1 or 0). For a number less than 1.0, count the number of
zeros after the decimal point and then add minus one. (The
characteristic of .245 is [-0] + [-1] or -1; .00245 is [-2] +
[-1] or -3.)
PERCENTAGE
Fig. 18.2 Determination of geometric mean
from tog probability paper

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524 Treatment Plants
The MANTISSA of a number is found by looking in log tables
in math books or handbooks and is the same no matter where
the decimal point in a measurement is located. Looking up the
mantissa of 245 in the log table shown below gives 3892. The
mantissa will be 3892 for 2,450, 24.5, or .245.
TABLE OF COMMON LOGARITHMS OF NUMBERS
N01234 56789
22	3424 3444
23	3617 3636
24	3802 3820 3838 3856 3874
25	3979
The logarithm of a number is the characteristic plus the man-
tissa.
EXAMPLES:
3892
3909 3927 3945 3962
Number
Characteristic
Mantissa
Logarithm
24,500
4
.3892
4.3892
2,450
3
.3892
3.3892
245
2
.3892
2.3892
24.5
1
.3892
1.3892
2.45
0
.3892
0.3892
.245
-1
.3892
1.3892
.0245
-2
.3892
"2.3892
.00245
-3
.3892
3.3892
.00245
-3
.3892
or 7.3892-10
Note that if the characteristic is negative, the logarithm is
written with the minus (-) sign over the characteristic (3.3892)
or the characteristic is subtracted from 10 and a -10 is placed
after the mantissa (7.3892-10).
EXAMPLE 5:
Calculate the geometric mean of the data used in the previ-
ous problem.
Measurement



MPN/100 ml
Characteristic
Mantissa
Logarithm
220
2
.3424
2.3424
230
2
.3617
2.3617
240
2
.3802
2.3802
240
2
.3802
2.3802
240
2
.3802
2.3802
250
2
.3979
2.3979
250
2
.3979
2.3979
260
2
.4150
2.4150
270
2
.4314
2.4314
300
2
.4771
2.4771
7200
3
.8573
3.8573

Sum of Logarithms =
27.8213
Moan of Logarithms =
Sum of Logarithms
Number of Measurements
27.8213
11
= 2.5292
To find the geometric mean, convert the mean of the
logarithms (2.5292) back to a number. The characteristic is 2
and the mantissa is 5292. First find the mantissa of 5292 in a
Table of Common Logarithms of Numbers and determine the
closest number as shown below.
TABLE OF COMMON LOGARITHMS OF NUMBERS
N01 23456789
32
33
34
The mantissa of 5292 falls between 5289 and 5302, but
closer to 5289. Therefore the number is 338. Since the mean
of the logarithms has a characteristic of 2, the
GEOMETRIC MEAN MPN = 338/100 ml
The geometric mean for this example is greater than all of
the other measurements except one. In many calculations of
the geometric mean, the results will be closer to the median.
18.72 Electronic Calculators
If you have an electronic calculator that can calculate the
powers of numbers, you can use the calculator to calculate the
geometric mean. Because the exact procedure will vary with
different calculators, check the instruction book provided with
your calculator to find the procedure for your calculator. To
determine if your calculator can determine the geometric
means, try the following example with the help of your cal-
culator's user's manual.
1.	Determine 34. The answer is 81.
2.	Determine 811/4 or 81° 25. The answer is 3.
If your calculator can find the powers of numbers less than
one (0.25), then the calculator should be able to determine the
geometric mean.
EXAMPLE 6:
Calculate the geometric mean of the data used in the previ-
ous problem.
Geometric Mean, _ ,v v Y v Y\i/n
MPN	( 1 2 "
= (220 x 230 x 240 x 240 x 240 x 250
x 250 x 260 x 270 x 300 x 7200)1'1'
= (6.629 109 429 x 1027)0 0909
= 338 per 100 ml
1. Multiply all values together. Multiply 220 times 230 times
240 times 240 times 240 times 250 and so on through the
last number, 7200. The answer you get should be 6.629
109 429 x 10"
,27
5051
5185 5198 5211 5224 5237 5250 5263 5276 5289 5302
5315 5328
2.	Determine the value for 1/n where n is the number of mea-
surements. Divide one by eleven and get 0.0909.
3.	Calculate the geometric mean. Using your pocket cal-
culator, find the 0.0909 power of 6.629 108 429 x 1027 or
(6.629 108 429 x l027)°-°909 = 338 or MPN = 338 per 100
ml.
18.73 Geometric Mean Table
If your calculator can't determine the 0.0909 power of a
number or similar numbers, you can use Table 18.2, the
Geometric Mean Table. Use the same procedure you used in
Section 18.72, "Electronic Calculators."
1.	Multiply all values together. Multiply 220 times 230 times
240 times 240 times 240 times 250 and so on through the
last number, 7200. Obtain 6.629 108 429 x 1027. Note that
in Section 18.71, "Logarithms," the "Sum of the
Logarithms" of the numbers is equal to 27.8213 which is the
same as 6.627 x 1027. You may wish to use logs rather
than multiply all of the numbers if you don't have a cal-
culator.
2.	After you have the number in scientific notation (6.629 x
10 ), refer to Table 18.2 (pages 526 and 527). Use the
column which corresponds to the number of measurements
or "number of samples used for determination." In our
example we used 11 measurements, so use column 11.

-------
Data Analysis 525
3. Look down column 11 until you find the number that is
CLOSEST to the number calculated. When you find the
number, look to the extreme left column to find the geomet-
ric mean value CLOSEST to the number calculated.
(1)
Column 11
Smaller Value
Calculated Value
Larger Value
(2)
Left Column
Geometric Mean = 325
= 4.272 x 10
= 6.629 x 10*'
= 9.654 x 10 Geometric Mean = 350
4. Since the calculated value is closer to 4.272 x 1027, report
the geometric mean as 325+. If the calculated value had
been closer to 9.654 x 1027, report the geometric mean as
350-.
5. This procedure can be used to determine the geometric
mean for the Most Probable Number (MPN) of either total or
fecal coliforms per 100 ml.
18.74 Example Problem
Calculate the geometric mean for the following fecal coliform
test results using the membrane filter method for a one month
period.
Test Number 1 2 3 4 5 6 7 8
MPN/100 ml 70 225 0 90 TNTC*<20 325 148
* TNTC means Too Numerous To Count. Whenever TNTC
appears, it cannot be used In the calculations. Report this
event on your monthly report form in the remarks area and
give the apparent reason for the high values.
1.	Arrange the MPN values you want to calculate the geomet-
ric mean for in increasing order of magnitude (size).
MPN Values 0 <20 70 90 148 225 325 TNTC
2.	Convert any MPN values that are zero to the number 1.
MPN Values 1 <20 70 90 148 225 325 TNTC
3.	If the MPN value is reported as less than (<) or greater than
(>), remove the < or > signs and use the values.
MPN Values 1 20 70 90 148 225 325 TNTC
4.	Drop all MPN values that are TNTC. See * above.
MPN Values 1 20 70 90 148 225 325
5.	Multiply all of the values together to get a number.
1 x 20 X 70 X 90 X 148 X 225 X 325 = 1 363 635 000 000
6.	Convert number from Step 5 to scientific notation.
a.	Place decimal to right of first number.
1.363 635 000 000
b.	Count the number of spaces or numbers to the right of
the decimal.
1.363 635 000 000
Count 1,2,3,4,5,6,7,8,9,10,11,12. There are 12 spaces
or numbers to the right of the decimal.
c.	Write the number as the first four numbers times 10 to
the power that equals the number of spaces or num-
bers to the right of the decimal.
1.363 xlO12
7.	After vou have the number in scientific notation (1.363
x101 ), refer to Table 18.2. Use the column which corre-
sponds to the number of measurements or "number of
samples used for determination." In this example we used
seven measurements, so use column 7. (While there were
eight measurements, measurement number 5 was too
numerous to count (TNTC), so it was not included in the
calculations.)
8.	Look down column 7 until you find the number that is
CLOSEST to the number calculated. When you find the
number, look to the extreme left column to find the geomet-
ric mean value CLOSEST to the number calculated.
(1)	(2)
Column 7	Left Column
Smaller Value = 7.812 x 1011	Geometric Mean = 50
Calculated Value = 1.363 x 101?
Larger Value
= 2.799 x 10 Geometric Mean = 60
9. Since the calculated value is closer to 7.812 x 1011, report
the geometric mean as 50+. If the calculated value had
been closer to 2.799 x 1012, report the geometric mean as
60-.
If you want to solve this problem by the use of an electronic
calculator, go back to step 5.
5.	Multiply all of the values together to get a number.
1 x 20 X 70 X 90 X 148 x 225 X 325 = 1 363 635 000 000
6.	Determine the value for 1/n where n is the number of MPN
values. Divide 1 by 7 and get 0.1429.
7.	Calculate the geometric mean. Using your pocket cal-
culator, find the 0.1429 power of 1.363 635 x 10 or
(1.363 635 x 1012)01429 = 54 or MPN = 54 per 100 ml
OR
Geometric Mean, = (1 x 20 x 70 x 90 x 148 x 225 x 325)1/7
MPN
= (1.363 635 x 1012)01429
= 54 per 100 ml
ACKNOWLEDGMENT
Portions of Sections 18.73 and 18.74 were prepared from a
paper, "Simplified Procedure for Calculating a Geometric
Mean for Fecal Coliform Values," by Roger Karn. The paper
appeared in the March 1977 issue of DEEDS & DATA and is
reproduced with the permission of the Water Pollution Control
Federation.
QUESTION
Write your answer in a notebook and then compare your
answer with the one on page 541.
18.7A Determine the geometric mean for the following
effluent fecal coliform test results:
Test Number 123456789
MPN/100 ml 43 12 8 14 63 11 23 17 49

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526 Treatment Plants
TABLE 18.2 GEOMETRIC MEAN TABLE
(FOR SELECTED FECAL COLIFORM VALUES FROM 10 TO 1,000)
NUMBER OF SAMPLES USED FOR DETERMINATION
1
10
20
30
40
50
60
70
80
90
100
110
120
130
140
150
160
170
180
190
200
225
250
275
300
325
350
375
400
450
500
600
750
1 000
10
20
30
40
50
60
70
80
90
100
110
120
130
140
150
160
170
180
190
200
225
250
275
300
325
350
375
400
450
500
600
750
1 000
100
400
900
1	600
2	500
3	600
4	900
6 400
8 100
10 000
12 100
14 400
16 900
19 600
22 500
25 600
28 900
32 400
36 100
40 000
50 625
62 500
75 625
90 000
105 625
122 500
140 625
160 000
202 500
250 000
360 000
562 500
1.000x10®
1 000
8 000
27 000
64 000
125 000
216 000
343 000
512 000
729 000
1.000x10s
1.331x10®
1.728x10®
2.197x10®
2.744x10®
3.375x10®
4.096x10®
4.913x10®
5.832x10®
6.859 x10s
8.000x10®
1.139x107
1.562X107
2.079 x107
2.700x107
3.432 x107
4.287X107
5.273x107
6.400x107
9.112X107
1.250 x10s
2.160x10®
4.218x10s
1.000x109
10 000
160 000
810 000
2.560x10®
6.250x10®
1.296x107
2.401 x107
4.096 x107
6.561 x107
1.000x10®
1.464x10®
2.073x10®
2.856x10®
3.841 x 10®
5.062x10®
6.553x10®
8.352x10®
1.049x10®
1.303x10®
1.600x10®
2.562x10®
3.906x10®
5.719x10®
8.100x10r
1.115x10'
1.500x10
1.977X101
2.560 x101
4.100x101
6.250x10'
1.296 x 101
3.164X101
1.000x101
9
,10
100 000
3.200x10®
2.430 x107
1.024x10®
3.125x10®
7.776x10®
1.680x10®
3.276x10®
5.904x10®
1.000x10'
1.610X101
2.488 X101
3.712x101
5.378 x101
7.593 x101
1.048 x 101
1.419X101
1.889X101
2.476 x101
3.200 X101
5.765 x101
9.765 x101
1.572X101
2.430 x101
3.625x10
5.252x10
7.415X101
1.024X101
1.845x10
3.125X101
7.776 x101
2.373 X101
1.000X101
12
13
1.000x10
6.400x107
7.290x10®
4.096x10®
1.562x101c
4.665x101t
1.176x1011
2.621 x1011
5.314X1011
1.000x10,!
1.771 x1015
2.985 xlO1
4.826x10'
7.529 X101
1.139x10'
1.677x10
2.413x10
3.401x10
4.704x10"
6.400x10'
1.297x10"
2.441x10"
4.325x10"
7.290x10"
1.178x10f
1.838x10
2.780x10"
4.096x10"
8.303x10'
1.562x10"
4.665x10'
,13
15
,15
16
1.000X107
1.280x10®
2.187x10
1.638x10
7.812x10
2.799x10
8.235x10
2.097x10
4.782x10
1.000x10
1.948x10
3.583x10
6.274x10
1.054x10
1.708x10
2.684x10
4.103x10
6.122x10
8.938x10
1.280x10
2.919x10
6.103x10
1.189x10
2.187x10
3.829x10
6.433x10
1.042x10
1.638x10
3.736x10
7.812x10
2.799x10
1.779x10 1.334x10
1.000x10
18
1.000x10'

-------
10
20
30
40
50
60
70
80
90
100
110
120
130
140
150
160
170
180
190
200
225
250
275
300
325
350
375
400
450
500
600
750
000
Data Analysis 527
TABLE 18.2 GEOMETRIC MEAN TABLE
(FOR SELECTED FECAL COLIFORM VALUES FROM 10 TO 1,000)
NUMBER OF SAMPLES USED FOR DETERMINATION
9	10	11	12
1.000x10®
2.560	x1010
6.561	x1011
6.553x10"
3.906 x1013
1.679X1014
5.764X1014
1.677X1015
4.304 X1015
1.000X1016
2.143X1016
4.299 X1016
8.157X1016
1.475X1017
2.562X1017
4.294 x1017
6.975 x1017
1.101 x1018
1.698x1018
2.560X1018
6.568x1018
1.525X1019
3.270 x1019
6.561 x1019
1.244x1020
2.251 X1020
3.91 OxIO20
6.553 x1020
1.681 X1021
3.906X1021
1.679x10"
1.001 x1023
1.000x1024
1.000X109
5.120x1011
1.968x1013
2.621 x1014
1.953x1015
1.007X1018
4.035 x1016
1.342x1017
3.874x10"
1.000x10
2.357 x1018
5.159X1018
1.060X1019
2.066 X1019
3.844 X1019
6.871 X1019
1.185X1020
1.983X1020
3.226 X1020
5.120X1020
1.477 x 1021
3.814x1021
8.994 x1021
1.968x1022
4.045 X1022
7.881 x1022
1.466x1023
2.621 x1023
7.566X1023
1.953X1024
1.007x10
7.508x10
1.000X1027
1.000X1010
1.024x10
5.904x1014
1.048X1016
9.765	x1016
6.046 x1017
2.824x1018
1.073X1019
3.486 x1019
1.000 x 10
2.593 x1020
6.191 x1020
1.378X1021
2.892 x1021
5.766	X1021
1.099X1022
2.015x1022
3.570 X1022
6.131 x1022
1.024X1023
3.325 x1023
9.536 x1023
2.473 x1024
5.904 x1024
1.314x10
2.758 x1025
5.499 xlO25
1.048x10
3.405 X1026
9.765 x1026
6.046 x1027
5.631 X1028
1.000x103°
1.000X1011
2.048	x1014
1.771 x1016
4.194X1017
4.882 x1018
3.627X1019
1.977X1020
8.589 x1020
3.138X1021
1.000 xlO22
2.853 x1022
7.430 x1022
1.792x10
4.049	x1023
8.649 x1023
1.759X1024
3.427 X1024
6.426x1024
1.164X1025
2.048 x1025
7.481 x102s
2.384 xlO26
6.802 x1026
1.771 x1027
4.272 X1027
9.654 x1027
2.062 x1028
4.194x10
1.532X1029
4.882 X1029
3.627 xlO30
4.223 x1031
1.000X1033
1.000x10
4.096X101*
5.314x10
1.677X1019
2.441 x1020
2.176x1021
1.384X1022
6.871 x1022
2.824 x1023
1.000 x 10
3.138x10
8.916 x102
2.329 x1025
5.669 x1025
1.297x10
2.814X1026
5.826 X1028
1.156x10
2.213x10
4.096 x1027
1.683x10
5.960 x1028
1.870x1029
5.314 x1029
1.388x103°
3.379 x103°
7.733 x103°
1.677x10
6.895 x103^
2.441 x1032
2.176x10
3.167x10
1.000x10
13
1.000x1013
8.192 x1016
1.594x1019
6.71 Ox 1020
1.220X1022
1.306x1023
9.688 x1023
5.497 x1024
2.541 x1025
1.000x1026
3.452 x1028
1.069x1027
3.028 X1027
7.937 xlO27
1.946X1028
4.503 x1028
9.904 x1028
2.082 x1029
4.205 x1029
8.192X1029
3.787 x1030
1.490X1031
5.144 x1031
1.594X1032
4.513x1032
1.182X1033
2.900 x1033
6.71 Ox 1033
3.102X1034
1.220 x 10
1.306x10
2.375 x1037
1.000x10
14
1.000X1014
1.638x10
4.782 x1020
2.684 x1022
6.103x1023
7.836 x1024
6.782 x1025
4.398 x1026
2.287 x1027
1.000x1028
3.797 x1028
1.283X1029
3.937 x1029
1.111 x1030
2.919x1030
7.205 x1030
1.683x10
3.748x1031
7.990 x1031
1.638x10
8.522 x1032
3.725 x1033
1.414X1034
4.782 x1034
1.466x1035
4.139X1035
1.087X1036
2.684 X1036
1.396x1037
6.103x1037
7.836 x1038
1.781 x1040
1.000x10

-------
528 Treatment Plants
18.8 MOVING AVERAGES
In Chapter 6, "Trickling Filters," Section 6.4, "Operational
Strategy," Figure 6.7 showed the use of moving averages.
Moving averages are an effective approach to revealing de-
teriorating trends in treatment processes. Figure 18.3 shows
plots of the effluent BOD from a trickling filter plant where both
the raw data and the moving average were plotted. Trends
may be difficult to detect when raw data are plotted because of
the fluctuation of the data. Plots of moving averages tend to
smooth out the data and reveal trends.
Moving averages are commonly seven-day moving aver-
ages which allow each day of the week to be included in the
average. At the example trickling filter plant, effluent BODs
were not collected on weekends. Therefore BOD values were
available only for Monday through Friday. Table 18.3 contains
the raw effluent BOD data and the calculated BOD moving
average values.
To calculate the moving average, simply find the mean for
the days being considered.
RAW DATA
20
10
0*-
1.
Date
Day
Effluent BOD, mg/L
3
M
5
4
T
9
5
W
5
6
T
6
7
F
6
Mean BOD,
mgIL
Sum = 31
Sum of All Measurements, mgIL
Number of Measurements
31 mg/L
= 6.2 mgIL which is moving average for Friday,
the 7th
2. Repeat the procedure by removing the oldest measurement
(Monday the 3rd) and adding the newest measurement
(Monday the 10th).
Date Day
4	T
5	W
6	T
F
M
7
10
Mean BOD,
mg/L
Effluent BOD, mg/L
9
5
6
6
5
Sum = 31
6.2 mg/L which is moving average for
Monday, the 10th.
20 -
10-
MOVING AVERAGE

—t
20
10
15
20
JANUARY
25
DAYS
30 31 1
10
15
FEBRUARY
Fig. 18.3 Plots of raw data and moving average for a trickling filter plant effluent BOD, mg/L

-------
Data Analysis 529
TABLE 18.3 TRICKUNG FILTER PLANT EFFLUENT BOD MOVING AVERAGE
MONTH

January
Effluent
Moving

February
Effluent
Moving
Date
Day
BOD, mgIL
Average
Date
Day
BOD, mgIL
Average
1
S


1
T
20
15.4
2
S


2
W
24
17.6
3
M
5

3
T
14
16.8
4
T
9

4
F
13
17.4
5
W
5

5
S


6
T
6

6
S


7
F
6
6.2
7
M
7
15.6
8
S


8
T
22
16.0
9
s


9
W
14
14.0
10
M
5
6.2
10
T
10
13.2
11
T
5
5.4
11
F
9
12.4
12
W
9
6.2
12
S


13
T
9
6.8
13
S


14
F
8
7.2
14
M
7
12.4
15
S


15
T
8
9.6
16
S


16
W
7
8.2
17
M
11
8.4
17
T
6
7.4
18
T
8
9.0
18
F
6
6.8
19
W
7
8.6
19
S


20
T
7
U.2
20
S


21
F
10
8.6
21
M


22
S


22
T


23
S


23
W


24
M
15
3.4
24
T


25
T
24
12.6
25
F


26
W
13
13.8
26
S


27
T
18
16.0
27
S


28
F
10
16.0
28
M


29
S






30
S






31
M
16
16.2




QUESTION
Date
5
6
7
10
11
Day	Effluent BOD, mgIL
W	5
T	6
F	6
M	5
T	_5
Sum = 27
Write your answer in a notebook and then compare your
answer with the one on page 541.
18.8A Calculate the seven-day moving average for the
effluent BOD from an activated sludge plant for the
second week.
Mean BOD, = 5.4 mgIL which is moving average for
mgIL	Wednesday, the 11 th
If you have an electronic calculator, you can subtract the
oldest measurement from the sum and add the newest meas-
urement. The best procedures depend on the type of cal-
culator.
WMkl







Date
7
8
9
10
11
12
13
Day
S
M
T
W
T
F
S
BOD
25
23
38
41
32
35
37
Week 2







Date
14
15
16
17
18
19
20
Day
S
M
T
W
T
F
S
BOD
29
23
31
24
17
19
24
END OF LESSON 1 of 2 LESSONS
on
ANALYSIS AND PRESENTATION OF DATA
Please answer the discussion and review questions before
continuing with Lesson 2.

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530 Treatment Plants
DISCUSSION AND REVIEW QUESTIONS
Chapter 18. ANALYSIS AND PRESENTATION OF DATA
(Lesson 1 of 2 Lessons)
At the end of each lesson in this chapter you will find some
discussion and review questions that you should work before
continuing. The purpose of these questions is to indicate to you
how well you understand the material in the lesson. Write the
answers to these questions in your notebook.
1.	Collection of data without	,	,
and	of results is a waste of time and money.
2.	Whether samples are collected, analyzed, interpreted, and
used by the same person or a different person performs
each task, every job is equally important if the application of
results is to be effective. True or False?
3.	What are the three principal factors that can cause varia-
tions in test results?
4.	How could errors occur when reading charts and gages?
The solids concentrations of sludge withdrawn from a pri-
mary clarifier during the past seven days are given below:
Day:	1 2 3 4 5 6 7
Solids, %: 6.0 6.5 6.0 5.0 6.5 7.5 8.0
5.	What is the arithmetic mean solids concentration?
6.	What is the range of solids concentration?
7.	What is the median solids concentration?
8.	What is the mode solids concentration?
9.	Determine the geometric mean for the following effluent
fecal coliform test results:
Week	12 3 4
MPN/100 ml 21 63 27 46
CHAPTER 18. ANALYSIS AND PRESENTATION OF DATA
(Lesson 2 of 2 Lessons)
18.9 GRAPHS AND CHARTS
18.90 Bar Graphs
Sometimes results can be illustrated by graphs to show the
characteristics (average value and dispersion) of data. Many
people, especially supervisors, can easily interpret data pre-
sented graphically and appreciate this approach.
EXAMPLE 7:
BOD tests for a two-week period provide the following
measurements, mg/L: 160, 155, 160, 160, 180, 165, 155,
170, 160, 165, 155, 150, 145, 160.
PROCEDURE:
1. Before actually plotting out a bar graph, you will need to
arrange the test results or other data in five to ten groups
of figures. Make a list of the test results in descending or
decreasing order. Next, estimate the spread between the
highest and lowest values in the main body of the list. (If
you find one or two figures either a great deal higher or
lower than the rest, you may ignore them for now.) If your
figures go from 180 to 145, for example, you have a differ-
ence of 35 between the high and low values. You want to
end up with five to ten equal groupings so you might de-
cide to make each group five units wide: 35 divided by 5
gives you seven groups. If your spread of data were 250,
you might choose to make the groups 25 units wide yield-
ing ten groups. Each group or class in the first example
will be five units (mgIL) wide. This is known as the width of
the class interval.
Once you have determined the width of the class interval,
you need to determine the range of the interval. That is!
exactly where each class or interval begins and ends. In
order to establish the class interval, however, you must keep
another factor in mind — class middlepoint.
2.	Class midpoint is the number that falls exactly in the mid-
dle of a class interval. The midpoint of a class 182.5 -
177.5 would be 180. To make graphing easier, it is helpful
to adjust the class intervals so that the midpoints are al-
ways numbers that are easy to work with such as: 2, 4, 6,
8, 10; or 5, 10, 15, 20, 25; or 10, 20, 30, 40, 50; or 25, 5o[
75, 100, 125.
Take another look at your highest reading (180 in this
example). This is a fairly easy number to work with when the
class is five units wide. The next midpoint would be 175,170,
and so on. If your highest number is 178, however, it would
be more awkward to graph as a midpoint so you could adjust
the midpoint to 180.
3.	You have now determined that the first class midpoint is
180 and that the width of the class interval is five (mgIL).
Add one-half of the interval (5 divided by 2 = 2.5) to the
first midpoint (180); the result is 182.5. This is the starting

-------
Data Analysis 531
point of the first class interval. Looking at column (a) be-
low, you will see that by continuing to subtract five from
this starting point you are able to create equal class inter-
vals. Continue subtracting until you pass your lowest test
result.
4.	Determine frequency. Count the number of test meas-
urements that fall within each class interval. This is usually
done by systematically going through your list of meas-
urements, placing a check or 1 (column (c) below) oppo-
site the appropriate class midpoint or class interval, and
then adding up the checks or 1's to obtain the frequency
(d).
5.	Plot the results as shown in the following bar graph.
Number of
Class Interval Class Midpoint Measurements Frequency
(a)
(b)
(c)
(d)
182.5- 177.5
180
1
1
177.5- 172.5
175

0
172.5- 167.5
170
1
1
167.5- 162.5
165
11
2
162.5- 157.5
160
1111
5
157.5- 152.5
155
111
3
152.5- 147.5
150
1
1
147.5- 142.5
145
1
1
indicate to supervisors or the public the increase in plant inflow
or decrease in the quality of plant effluent to justify increases in
budgets or plant expansion. To look for or show a trend, plot
the value you are interested in (for instance, flow, MGD, or
effluent BOD, mgIL) against time (day, week, month, year).
EXAMPLE 8:
Analysis of flow data (totalizer readings) provides the follow-
ing annual information:
Year:	1965 1966 1967 1968 1969 1970
Mean Daily Flow, MGD: 1.25 1.38 1.42 1.58 1.65 1.81
Plot the data:
PROJECTED
FUTURE
FLO*
II
10
YEAR .... 1975 1976 1977 1978 1979 1980 1981 1982
BAR GRAPH SHOWING DISTRIBUTION OF BOD
MEAN BOD 160 mgIL
RANGE OF BOD 35 mgIL
_L
-t-
X
HO 145 150 155 160 165 170 175 180
BOD. mg/l
Sometimes the plotting points on a bar graph are connected
to form a smooth curve. The resulting curve describes either a
NORMAL or a SKEWED distribution of the data, depending on
the shape of the curve. If the distribution is normal, the mean,
median, and mode values will be approximately the same. In
skewed distributions the mean, median, and mode are differ-
ent (Fig. 18.4).
QUESTION
Write your answer in a notebook and then compare your
answer with the one on page 542.
18.9A The results of the SVI (Sludge Volume Index) test for
an activated sludge plant for one week were as fol-
lows: 120, 115, 120, 120, 125, 110, 115.
a.	Calculate the arithmetic mean SVI.
b.	What is the range?
c.	Draw a bar graph showing the distribution
(spread) of SVI.
18.91 Trends
Plotting data on GRAPHS5 is very helpful to illustrate trends
in the operation of your plant. Occasionally plotting data will
reveal unexpected trends. This approach could be used to
INTERPRETATION OF DATA:
The graph shows a continuously increasing mean daily flow.
If your plant has a capacity of 2 MGD, the graph would clearly
show the need for expansion in the near future if past trends in
population growth or any industrial expansion continue. You
could extend the trend (dashed line) to project future flows and
predict when you expect to reach plant capacity (1981-1982).
APPUCATIONS:
Plotting data and looking for trends may be helpful to indi-
cate broken pipes and illegal connections or discharges. You
should always attempt to identify the cause of a trend. An
industry may clean up on Friday afternoon and dump a slug of
waste into the collection system that may reach your plant
Friday night. If you plot your data and note a reduction in the
quality of your effluent every Friday night or Saturday, you
might start looking for the cause of the problem.
Some operators record flows continuously on daily circular
charts. Every year they change the color of the ink, but use the
same chart on the same day for several years. This is a good
way to identify trends, too.
18.92 Summary
Two methods have been given in this section to present
data:
1.	Bar Graphs, and
2.	Line Graphs.
How does the operator determine which method to use?
BAR GRAPHS are used to SUMMARIZE DATA and indicate
number of times or frequency a given value was measured.
LINE GRAPHS illustrate TRENDS by showing how a particular
measurement changes with time. Section 18.75, "Moving Av-
erages," also describes a procedure used to reveal trends.
9 Qraph paper may be obtained at moat stationery stores. See graph paper at end of this chapter, pg. 545.

-------
532 Treatment Plants
o
cc
Li.
170
160
150
140
180
BOD rug/1
MEAN, MEDIAN AND MODE BOD VALUES
ALL EQUAL 160 mgIL
NORMAL DISTRIBUTION OF DATA
>-
O
z
UJ
=>
o
UJ
GC
U-
180 BOD mg/l
170
150
160
140
MODE MEDIAN MEAN
146 151 157 mg/L
SKEWED 01STRI BUT I ON OF DATA
Fig. 18.4 Normal and skewed distribution of data

-------
Data Analysis 533
QUESTION
Write your answer in a notebook and then compare your
answer with the one on page 542.
18.9B Weekly alkalinity tests on digester sludge are given
below:
Week
Alka-
linity,
mgIL
1 23456789 10
1730 1670 1690 1680 1630 1620 1590 1530 1480 1420
a.	Is a trend apparent?
b.	Should any action be taken by the operator?
18.93 Chart Preparation
Sometimes routine plant operational information can be
quickly and easily determined by the use of graphs or charts.
An example might be the measurement of the depth of sludge
in a digester. The depth can be used to calculate the volume of
sludge in gallons or in cubic feet. A quick way to convert depth
to volume and to reduce the chance of mathematical errors is
to prepare a chart of sludge depth against sludge volume.
EXAMPLE 9:
Prepare a chart of sludge depth against sludge volume for a
100-foot diameter digester.
Unknown
Volume of Digester
for Various Sludge
Depths, cu ft
Known
MEASURED
SLUDGE
DEPTHS
20 FT.-
PROCEDURE:
r
DIAMETER = 100 FT.
20 FT.
123 FT.
Calculate the sludge volume in the digester at three depths
(0,10 and 20 ft). This will provide us with three plotting points
on our chart. If the points are not on a straight line, we should
look for a possible error in our calculations.
1.	Calculate the volume of the bottom cone of the digester.
This will be the volume of sludge in the digester if the depth
of sludge was measured to be zero along the inside wall of
the digester.
Cone Volume, cu ft = JL(Radius, ft)2(Height, ft)
3
= JL(50 ft)2(12.5 ft)
3
= 32,725 cu ft
2.	Calculate the volume of sludge in the digester if the meas-
ured sludge depth is 10 feet.
/...« Volume from 0 to , Volume of Bottom
Volume, cu ft = 10 feet cu ft + cone.cuft
= JL(100 ft)2(10 ft) + 32,725 CU ft
4
= 78,540 cu ft + 32,725 cu ft
= 111,265 cu ft
Calculate the volume of sludge in the digester if the meas-
ured sludge depth is 20 feet.
Volume, cu ft =
Volume from 0 to
20 feet, cu ft
Volume of Bottom
Cone, cu ft
= _?1(100 ft)2(20 ft) + 32,725 cu ft
4
= 157,080 cu ft + 32,725 cu ft
= 189,805 CU ft
4. If sludge volumes were desired in gallons, the sludge vol-
umes in cubic feet could be multiplied by 7.5 gallons per
cubic foot.
5. Summarize plotting points.
Depth of
Sludge, ft
0
10
20
Volume of
Sludge, cu ft
32,725
111,265
189,805
Volume of
Sludge, M Gal
0.245
0.834
1.424
6.	Plot data as shown on Figure 18.5. Be sure to use a large
enough scale for both depth of sludge in feet and volume of
sludge in cubic feet to get accurate results. Draw a straight
line between the three plotting points.
7.	To prepare the million gallons scale, draw another line
below and parallel to the sludge volume, 1000 cubic feet
line.
a. Calculate the cubic feet In one million gallons.
1 M Gal = 1.000.000 98'
7.5 gal/cu ft
= 133,333 cu ft
OR
0.1 M Gal = 13,333 cu ft
b.
Prepare a table of the number of cubic feet in 0.1 M
Gal, 0.2 M Gal and so on up to 200,000 cubic feet.
1000 cu ft
M Gal
1000 cu ft
M Gal
13.3
0.1
120.0
0.9
26.6
0.2
133.3
1.0
40.0
0.3
146.7
1.1
53.3
0.4
160.0
1.2
66.7
0.5
173.3
1.3
80.0
0.6
186.7
1.4
93.3
0.7
200.0
1.5
106.7
0.8


c. Find 13.3 (1000 cubic feet) and drop down to the lower
parallel line and mark 0.1 M Gal. Find 26.7 (1000 cubic
feet), drop down to lower line and mark 0.2 M Gal.
Repeat procedure for remainder of table.
8. To use Figure 18.5, measure the depth of sludge in the
digester. For example, 8.5 feet. Find the depth on Figure
18.5 (point a). Move horizontally across to the diagonal line
(point b). Drop vertically down. Read the digester volume as
100,000 cubic feet (point c) or 0.75 million gallons (point d).
18.94 COD to BOD Curves
In Chapter 11, "Activated Sludge," Section 11.54, "Actual
Operation Under Abnormal Conditions," Figure 11.19 showed
how an operator used COD measurements to estimate effluent
BOD values and comply with NPDES permit monthly allowable
BOD discharges. To use this procedure you must compare
monthly effluent COD discharges in pounds per month with
monthly effluent BOD discharges in pounds per month. If the
values are similar on a month to month basis, or on a compari-

-------
SLUDGE VOLUME, 1000 CUBIC FEET
—'	1	1	'	1	1	1	I	1	1	1	1			i	i	' »
0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0& 1.0 1.1 1.2 1.3 1.4 15
SLUDGE VOLUME, MILLION GALLONS
Fig. 18.5 Chart to determine sludge volume in cubic feet or million gallons from depth of sludge

-------
Data Analysis 535
son of months on a year to year basis (September of this year
to September of last year), then this procedure may be used.
The relationship must be watched carefully during critical
months. Be sure that the conversion factor from COD to BOD
estimates the BOD slightly higher than the actual BOD in order
to be on the safe side.
PROCEDURE
1.	Determine the number of days in the month and the allowa-
ble NPDES permit effluent BOD in pounds per month. The
example in Figure 18.6 has 30 days in the month and an
allowable effluent BOD of 80,000 pounds per month.
2.	Prepare the horizontal scale in days and the vertical scale
in 1000 pounds of effluent BOD. Above 30 days plot the
point 80,000 pounds of effluent BOD. Draw the diagonal
line from the origin (0 days and 0 effluent BOD) to the
plotted point (30 days and 80,000 pounds of effluent BOD).
As long as the cumulative estimated BOD using the COD
values and the actual BOD values plot below the diagonal
line, you should be able to meet your monthly NPDES per-
mit BOD discharge requirement.
3.	Analyze monthly COD to BOD relationships. For our exam-
ple plant, the cumulative COD for last month was 473.2
pounds and the cumulative BOD was 76.66 pounds. Calcu-
late the COD to BOD factor.
COD to BOD factor = BOD, lbs/month
COD, lbs/month
= 76.66 lbs BOD/month
473.2 lbs COD/month
= 0.162
To be on the safe side, increase the factor slightly to 0.163
or 0.1633.
4.	Prepare a table like Table 18.4. Every day measure flow in
MGD, COD in mg/L and start the five-day BOD test. Esti-
mate the cumulative BOD in pounds per day and plot the
value every day. Five days later when the BOD results
become available, plot the actual cumulative pounds of
BOD.
a.	Calculate COD in 1000 pounds per day.
COD, 1000 lbs = (Row, MGD) (COD, mg/L) (8.34J^g)(1000)
day	gal (1000)
= (19.9 MGD) (60 mg/L) (8.34 j^)(100°)
gal (1000)
= 9958 (100°)
day (1000)
= 9.96 J5L(1000)
day
= 10.0 (1000 lbs COD/day)
b.	Determine cumulative COD in 1000 pounds per day.
Cum. COD, _ Today's COD, Yesterday's Cum. COD,
1000 lbs/day 1000 lbs/day	1000 lbs/day
= 13.0 + 10.0
= 23.0 (1000 lbs COD/day)
c.	Calculate BOD in 1000 pounds per day.
BOD,1000 lbs = (Flow, MGD) (BOD, mg/L) (8.34^5. )(1000)
day	gal (1000)
= (19.9 MGD) (9 mgIL) (8.34 /1000)
gal (1000)
= 1494 ^ (1000)
day (1000)
= 1.5 (1000 lbs BOD/day)
d.	Determine cumulative BOD in 1000 pounds per day.
Cum. BOD, _ Today's BOD, , Yesterday's Cum. BOD,
1000 lbs/day 1000 lbs/day	1000 lbs/day
= 1.5 + 2.3
= 3.8 (1000 lbs BOD/day)
e.	Calculate cumulative BOD estimated by cumulative
COD in 1000 pounds per day.
Est. Cum. BOD, = (Cum CQD 1000 ibs/day) (0.163)
1000 lbs/day
= (10.0) (0.163)
= 1.6
f.	NOTE: Values in Table 18.4 are rounded off for con-
venience and because greater accuracy is not
necessary.
18.10 VARIANCE AND STANDARD DEVIATION
Variance and standard deviation are terms frequently used
in professional journals that report the results of research find-
ings. Knowledge of this material is important in the field of
quality control because these terms describe the spread of
measurements or results.
In previous discussions, results have been described in
terms of a mean value and a range. The bar graphs below
show the results of three different tests, but they all have the
same mean value and range.
. 11 11 111111 I 11 11111111—
uo iso iso uo iso ieo
BOO. *i'l	BOD. me I
11	III
For all three cases, the mean value is 150 mg/L and the
range is 20 mg/L (160-140), using the midpoints for our calcu-
lations.
Another term (parameter) to describe the above results is
the variance, o , a measure of the DISPERSION or SPREAD
of the results. The variance is calculated by taking the differ-
ence between each measurement, X, and the mean value of
MO 150 160
BOD. Rg I
I

-------
536 Treatment Plants
~ EFFLUENT BOD
ESTIMATED USING COD
ACTUAL EFFLUENT BOD
NPDES PERMIT
EFFLUENT BOD = 80,000 LBS/MO
DAYS
Fig. 18.6 Estimated and actual effluent BOD

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Data Analysis 537
TABLE 18.4 ESTIMATION OF EFFLUENT BOD USING EFFLUENT COD MEASUREMENTS



Effluent

Cumulative

Cumulative
Cumulative BO


Flow,
COD,
BOD,
COD, 1000
COD, 1000
BOD, 1000
BOD, 1000
Estimated by C(
Date
Day
MGD
mg IL
mg IL
lbs/day
lbs/day
lbs/day
lbs/day
1000 lbs/day
1
M
19.9
60
9
10.0
10.0
1.5
1.5
1.6
2
T
22.6
69
12
13.0
23.0
2.3
3.8
3.8
3
W
22.7
62
10
11.7
34.7
1.9
5.7
5.7
4
T
23.5
69
11
13.5
48.2
2.1
7.8
7.9
5
F
23.8
65
7
12.9
61.1
1.4
9.2
10.0
6
S
21.7
131
20
23.7
84.8
3.6
12.8
13.8
7
S
22.0
100
16
18.3
103.1
2.9
15.7
16.8
8
M
23.3
102
18
19.9
123.0
3.5
19.2
20.0
9
T
23.8
110
16
21.8
144.8
3.2
22.4
23.6
10
W
23.8
97
11
19.3
164.1
2.2
24.6
26.8
11
T
24.0
82
20
16.4
180.5
4.0
28.6
29.5
12
F
23.2
71
15
13.7
194.2
2.9
31.5
31.7
13
S
22.5
140
20
26.3
220.5
3.8
35.3
36.0
14
S
22.1
100
18
18.4
238.9
3.3
38.6
39.0
15
M
24.0
130
27
26.0
264.9
5.4
44.0
43.3
16
T
25.6
280
65
59.8
327.7
13.9
57.9
53.5
17
W
19.5
170
26
27.6
352.3
4.2
62.1
57.5
18
T
16.6
89
8
12.4
364.7
1.1
63.2
59.6
19
F
17.2
77
10
11.0
375.7
1.4
64.6
61.4
20
S
17.7
71
9
10.5
386.2
1.4
66.0
63.1
21
S
17.1
69
8
9.8
396.0
1.1
67.1
64.7
22
M
19.9
69
10
11.5
407.5
1.7
68.8
66.5
23
T
20.3
63
9
10.7
408.2
1.5
70.3
68.3
24
W
21.0
79
10
13.8
432.0
1.7
72.0
70.5
25
T
21.1
53
10
9.3
441.3
1.8
73.8
72.1
26
F
21.3
51
7
9.1
450.4
1.2
75.0
73.6
27
S
18.0
58
3
8.7
459.1
0.5
75.5
75.0
28
S
18.0
76
5
11.4
470.5
0.7
76.2
76.8
29
M
21.9
56
8
10.2
480.7
1.5
77.7
78.5
30
T
22.4
60*
9*
11.2
491.9
1.7
79.4
80.3
* Since plant was close to violating NPDES permit BOD discharge requirement, all effluent was diverted to a holding pond and there
was no discharge on the last day of the month.

-------
538 Treatment Plants
all the measurements, X, squaring it, summing up the squared
differences, and dividing by the total number of differences, n,
minus one, as shown in the following formula.
Variance, S2
STEP 3.
Calculate the variance for the results shown in Bar Graph III.
Mean Value, X =
= 1 (X-X)2
Measurement, X
140
X-X (X-X)2
-10 100
Freq. (X
4
-X)2 Freq.
400
n-1
145
- 5 25
3
75
= Each Measurement
150
0 0
1
0
155
5 25
3
75
= IX
160
10 100
4
400
n

TOTAL n =
15 S(X-~X)2
= 950
n = Number of Measurements
1 - Summation of All Values
In the denominator, one is subtracted from n, because X in
the numerator is calculated from n measurements. X is influ-
enced by all of our measurements. By dividing by n-1 we
obtain a more conservative description of the actual disper-
sion. The larger n becomes, the more insignificant becomes
the "minus one" term. When analyzing plant data, the number
of measurements is usually small; therefore, the "minus one"
term is important.
STEP 1. Calculate the variance for the results shown in Bar
Graph I.
X, mgIL
x-x
(X-X)'
Fr#q.
(X-X) Fr*q.
140
145
150
155
160
140-150 = -10 (-10) (-10) - 100
145-150 =
150-150 =
155-150 =
160-150 -
(- 5) (- 5) = 25
( 0) ( 0) = 0
( 5) ( 5) = 25
100
(100) (2) = 200"
( 25) (3) = 75
( 0) (5) - 0
10 ( 10) ( 10)
TOTAL n
3 ( 25) (3) = 75
S2 = S (X-X)2
n-1
550
	(100) (2)
15 X (X-X)!
39.28
14)550
42
200
550 (mfl/i.)1'
(mg/L)
15-1
= 550
14
= 39.3 (mgIL)2
130
126
40
28
1 20
1 12
STEP 2.
Calculate the variance for the results shown in Bar Graph II.
Measurement, X X-X (X-X) Freq.
140
145
150
155
160
-10
- 5
0
5
10
100
25
0
25
100
(X-X)2 Freq.
300
75
0
75
300
2 _ 2 (X2,X)
TOTAL
2
S' =
n = 15 2 (X-X)' =750
53.57
14J750
70
50
42
= 53.6 (mg//.)
80
70
1 00
98
g! = 1 (X-X)
n-1
950
67.85
14)950
84
15-1
67.9 (mgIL)2
110
98
120
11 2
80
70
In comparing the variance of the three bar graphs, note that
as more and more measurements shift away from the mean
value, the value of the variance increases, thus indicating an
increase in the dispersion of our results.
The dispersion is frequently described in terms of S, the
standard deviation, which has the same units as the average
value, mgIL. The standard deviation, S, is the square root of
the variance, Sz. The square root of a number is one of two
equal numbers that when multiplied together give that number.
EXAMPLES:
The square root of 9	= 3
16	= 4
25	= 5
4=2
1	= 1
S2	= S
1.44	= 1.2
(mgIL)3	= mgIL
or V 9
\Zl6~
%/2T
V
4
VT
v^~
V1.44
or V (mg/i.)2
= 3 and (3) (3) = 9
= 4 and (4) (4) = 16
= 5 etc.
= 2
= 1
= S
= +-
= mgII
To obtain the square root of a number, there are several
potential methods listed below in order of ease of use.
1.	Use an electronic calculator.
2.	Look up the values in a table in a math book or handbook.
3.	Use a slide rule.
4.	Attempt a trial and error approach by multiplying a number
by itself.
5.	By direct calculation.
EXAMPLE 10:
Find the standard deviation, S, of the variance S2 = 39 3
(mg/Lf.
Use of a math book or handbook, a slide rule or an electronic
calculator are the quickest and easiest ways to find the square
root of a number. If these sources are not available, the square
root may be calculated.
* Units should be (mgIL)1. The term is meaningless, but is included
to maintain the proper units, For the first row. X is 140 mg/i.; X-X
is 140 mg/i.-150 mgIL = -10mgIL; (X-X) is (-10 mgIL) (-10
mgIL) = 100 (mglL)r\ and (X-X)2 Freq. is (100 [mg/i.]) (2) = 200
(mg//.)2.
** Instead of writing 140 twice, subtracting 140-150 twice, and
squaring (-10) (-10) twice, we performed our calculations once
on one line and then multiplied by the frequency, 2. We did the
same for the other measurements, X.

-------
Data Analysis 539
TRIAL AND ERROR:
First try Step 4, multiplying a number by itself.
Trial:
1
II
III
IV
6.0
6.5
6.3
6.2
6.0
6.5
6.3
6.2
36^00
325
189
124

390
378
372

42.25
39.69
38.44
Less
Greater
Greater
Less
than
than
than
than
39.3,
39.3,
39.3,
39.3,
too
too
too
too
small
large
large
small
Trial III is closest to 39.3. Therefore S = 6.3 mg/L.
DIRECT CALCULATION:
To calculate the square root directly, the following steps are
used.
1. Begin at the decimal point and separate the number in
groups of two, to the left, or right, or in both directions,
depending on the number, as shown below.
V39.30 oo
OTHER EXAMPLES6:
VTasT V0.66 20 V0.04 31
2. Select the largest number which, when squared, is equal to
or less than the number contained in the first number or pair
of numbers on the left.
6.	
V39.30
OTHER EXAMPLES:
1
8
vT28. V0.66 20 V0 04 31
3. Square this number, subtract it from the first number or pair
of numbers, and bring down the next pair of numbers.
V3ST30
36^
3.30
4. Double the 6, obtain 12, and estimate how many twelves
will go into 33. The answer is 2. Place 2 over 30 and to the
right of 12, obtaining 122. Multiply 122 by 2 to get 244.
Subtract 330-244 = 86 and bring down the next pair of
numbers (00).
6. 2
V39.30 00
36.	
122 V 3.30
2.44
86 00
5. Double 62, obtain 124, and estimate how many times 124
goes into 860. Try 7. Place 7 over 00 and to the right of 124
to obtain 1247. Multiply 1247 by 7 to get 8729. This is larger
than 8600. Reduce 7 to 6. Multiply 1246 by 6 to get 7476.
Subtract, 8600-7476 = 1124, and bring down the next pair
of numbers.
6. 2 6
V39.30 00
ae_
122 V 3 20
2 44
1246 V
86 00
74 76
11 24
Therefore, S = 6.26
or S = 6.3 mg/L
CHECKS
QUESTION
Write your answer in a notebook and then compare your
answer with the one on page 542.
18.1 OA Calculate the variance and standard deviation of the
SVI data given in Question 18.9A. SVI = 120, 115,
120, 120, 125, 110, 115.
S2 =
= 1 (X - X)2
18.11 METRIC CALCULATIONS
Metric calculations are not included in this chapter because
the procedures used to analyze and present data are the same
for both the English and Metric Systems. Use the same proce-
dures to analyze numbers, regardless of the system.
18.12 SUMMARY
1. AVERAGE OR MEAN VALUE
Sum of All Measurements
X =
IX
Number of Measurements
where X is each measurement or test result, and n is the
number of measurements or observations.
2.	RANGE
Range = Largest X
3.	MEDIAN
Smallest X
Median = Middle measurement when measurements are
ranked in order of magnitude (may fall between two
measurements)
4.	MODE
Mode = Measurement that occurs most frequently (may be
more than one mode)
5.	GEOMETRIC MEAN
Geo. Mean = (X, x x2 x X3 x .... Xn)1/n
8 These other examples are provided to Indicate how to determine the square root of other numbers.

-------
540 Treatment Plants
3. VARIANCE AND STANDARD DEVIATION
Variance, S
Standard
Deviation,
S
- £ (X-X)z
n-1

18.13 ADDITIONAL READING
1. "Basic Statistical Methods for Engineers and Scientists," by
J.B. Kennedy and A.M. Neville, Harper and Row Pub-
lishers, Inc., Keystone Industrial Park, Scranton, Pennsyl-
vania 18512. Price $19.95.
vs*
END OF LESSON 2 OF 2 LESSONS
on
ANALYSIS AND PRESENTATION OF DATA
Please answer the discussion and review questions before
working the Objective Test.
DISCUSSION AND REVIEW QUESTIONS
Chapter 18. ANALYSIS AND PRESENTATION OF DATA
(Lesson 2 of 2 Lessons)
Work these questions before continuing. Write your answers
in your notebook. The problem numbering continues from Les-
son 1.
The solids concentrations of sludge withdrawn from a pri-
mary clarifier during the past seven days are given below:
Day:	1 2 3 4 5 6 7
Solids, %: 6.0 6.5 6.0 5.0 6.5 7.5 8.0
10.	Draw a bar graph showing the distribution of data.
11.	Draw a line graph to illustrate if any trend is developing.
12.	Is a trend apparent?
13.	Calculate the variance, S2, for the solids data.
14.	Determine the standard deviation, S, for the solids data
using any method you prefer.
PLEASE WORK THE OBJECTIVE TEST NEXT.

-------
Data Analysis 541
SUGGESTED ANSWERS
Chapter 18. ANALYSIS AND PRESENTATION OF DATA
Answers to questions on page 519.
18.1 A Variations in test results may be caused by changes
in:
1.	Water or material (sludge) being examined,
2.	Sampling procedures, and
3.	Testing (analyst, procedure, reagents, equipment).
Many factors in each of these three categories also
can cause changes. For example, in sampling, varia-
tions could be caused by changing the location where
the sample was obtained and when the sample was
obtained.
18.1B Samples should be tested immediately by the lab be-
cause sometimes the items (BOD, DO) we wish to
measure will change with time due to biological or
chemical reactions taking place in the sample con-
tainer.
Answers to questions on page 519.
18.2A Instruments must be periodically calibrated and
zeroed before using to insure accurate results.
18.2B A gage reading of 2 psi also would give a reading of
4.6 feet of water.
Answers to questions on page 521.
18.4A Calculate the mean mixed liquor concentration in
mg/L.
Mean Concentra-
tion, mg/L
_ Sum of All Measurements, mg/L
Number of Measurements
5922 mg/L
= 1974 mg/L
18.5A Range of measurements.
Range, mg/L = Largest Value - Smallest Value
= 2138 mg/L - 1863 mg/L
= 275 mg/L
Answer to question on page 522.
18.6A Rank SVI Freq.
2138
1863
1921
5922
2138
-1863
275
1
2
3
4
5
6
7
125
120
120
120
115
115
110
Median SVI = 120 Half of the values
are larger and half
are smaller.
Mode SVI = 120 Value that occurs
most frequently
(three times).
Answer to question on page 525.
18.7A 1. Arrange the MPN values in increasing order of
magnitude (size).
8 11 12 14 17 23 43 49 63
2.	Multiply all of the numbers together to get a
number.
8 x 11 x 12 x 14 x 17 x 23 x 43 x 49 x 63 =
767 315 191 200
3.	Convert the number in Step 2 to scientific notation.
7.673 x 1011
4.	Find the Geometric Mean from Table 18.2.
(1)
Column 9
Smaller Value	= 5.120 x 10"
Calculated Value	= 7.673 x 10"
Large Value	= 1.968 x 10"
Geometric Mean	= 20+ MPN/100 ml
(2)
Left Column
Geometric Mean = 20
Geometric Mean = 30
5. If you have an electronic calculator, use the follow-
ing procedure.
Geometric = /8 x t1 x 12 X 14 x 17 X 23 x 43 x 49 x X 63)1
Mean
= (7.673 x 10'1)01111
= 21 MPN/100 ml
Answer to question on page 529.
18.8A Date Day Effluent BOD, mg/L Moving Average
7
S
25

8
M
23

9
T
38

10
W
41

11
T
32

12
F
35

13
S
37
33.0
14
S
29
33.6
15
M
23
33.6
16
T
31
32.6
17
W
24
30.1
18
T
17
28.0
19
F
19
25.7
20
S
24
23.9
END OF ANSWERS TO QUESTIONS IN LESSON 1

-------
542 Treatment Plants
Answer to question on page 531.
18.9A
SVI
Freq.
SVI x Freq. or
Sum of SVI
125
1
125
125



120
120
3
360
120



120
115
2
230
115



115
110
1
110
110
SUMS
7
825
825
a. Mean SVI
Sum of SVI
Number of SVI
825
7
118
7j
117.8
825
7	
12
7
55
49
Freq.
b. Range of SVI
c. Bar Graph.
60
56
= Largest SVI - Smallest SVI
= 125 - 110
= 15
110
15 120
SVI
125
Answer to question on page 533.
18.9B
ieoo
1700
1600
1300
HOC
1300
1200
1100
1000
4 5 6
WEEK
a.	Yes, a trend is apparent.
b.	Corrective action should be taken to prevent the
continued drop of alkalinity. See Chapter 12 on
Sludge Digestion and Handling.
Answer to question on page 539.
18.10A
X Freq. X Freq.
125	1	125
120	3	360
115	2	230
110	1	110
SUM
825
X-X

(X-X)2
(X-X)1 F.
125-118 =
7
49
49
120-118 =
2
4
12
115-118 =
-3
9
18
110-118 =
-8
64
64



143
1. Calculate mean SVI,~X.
= Sum Measurements
Sum Freq.
=
7
= 118
117.8
7)825
7	
12
7
55
49









«
•
•
,

60
56
2.	Determine X-X = X-118 = 125 - 118 = 7
3.	Determine (X -1()2 = (7)2 = 49
4.	Determine (X -l()z(Freq.) = 49 x 1 =49
5.	Calculate variance, S2
S2 = S (X - X)2
n - 1
143
7-1
= 24
23.8
6)143
12
23
18
50
48
6. Calculate standard deviation, S.
S = VW
= n/24"
= 4.9
4.9
V247
16
8916 00
8 01 Close enough ...
END OF ANSWERS TO QUESTIONS IN LESSON 2

-------
OBJECTIVE TEST
Chapter 18. ANALYSIS AND PRESENTATION OF DATA
Data Analysis 543
Please write your name and mark the correct answers on the
answer sheet as directed at the end of Chapter 1. There may
be more than one correct answer to each question.
1.	Different operators collecting effluent samples must follow
the same procedures in order to make the test results
useful.
1.	True
2.	False
2.	Presentation of data in tables, graphs, and charts makes it
more accurate.
1.	True
2.	False
3.	A graph shows test results better than a table of data.
1.	True
2.	False
4.	A variance value is a trend value.
1.	True
2.	False
5.	A steadily increasing SVI value could be called a "trend."
1.	True
2.	False
6.	Presentation of data in tables, graphs, and charts make it
more useable.
1.	True
2.	False
7.	Probability in percent is calculated the same way as the
geometric mean.
1.	True
2.	False
8.	A median value is calculated the same way as a mean
value.
1.	True
2.	False
9.	A "totalizer" is an averaging type of recorder.
1.	True
2.	False
10.	Instruments calibrated in the factory do not have to be
recalibrated after installation and use.
1.	True
2.	False
11.	The meniscus is part of a manometer scale.
1.	True
2.	False
12.	A representative sample
1.	Describes the overall situation.
2.	Represents the equipment manufacturers.
3.	Represents the people
13.	The characteristics of a sample may change between col-
lection and analysis due to
1.	Biological changes in the sample.
2.	Changes in the variance.
3.	Chemical changes in the sample.
4.	Nothing — the characteristics don't change.
5.	Temperature changes during transportation to the lab.
14.	Laboratory results of influent BOD at a particular plant
could vary due to
1.	Collecting samples in a different manner.
2.	Differences in the composition of the influent.
3.	Nothing — the results should not be different.
4.	Operators not following the exact same testing proce-
dure every time.
5.	Operators titrating to different end points.
15.	Data should be collected and (select best answer)
1.	Analyzed.
2.	Filed.
3.	Forgotten.
4.	Lost.
5.	Values placed in all columns on report sheet.
16.	At the beginning of a week a totalizer on the plant inflow
read 3,827,579 gallons. Seven days later, the totalizer
reads 4,623,691 gallons. What was the approximate mean
daily flow during the week?
1.	0.01 MGD
2.	0.11 MGD
3.	0.14 MGD
4.	0.80 MGD
5.	1.14 MGD
17.	Bar graphs can be used to show which of the following?
1.	Characteristics of data
2.	Dispersion of data
3.	Growth
4.	How neat you can draw
5.	Results of lab tests to your supervisor
18.	Plotting data on graph paper to show trends may be help-
ful to
1.	Describe the variance.
2.	Illustrate patterns of effluent quality.
3.	Illustrate the need to look for the cause of trend.
4.	Justify budget increases.
5.	Predict when expansion will be necessary.
Use the following information to answer questions 19 through
25. At 1:30 PM every day of the week, the dissolved oxygen in
the Number 1 pond of a wastewater treatment facility is meas-
ured and the results are summarized below in mgIL:
WEEK	DAY
1	9.1 9.4 10.8 9.9 9.7
2	9.3 8.8 8.5 8.0 7.4

-------
544 Treatment Plants
19.	What was the arithmetic mean DO in the pond over the
two-week period?
1.	8.5 mg/L
2.	8.8 mg/L
3.	8.9 mg/L
4.	9.0 mg/L
5.	9.1 mg/L
20.	What was the range ot DO?
1.	2.3 mg/L
2.	3.4 mg/L
3.	4.3 mg/L
4.	7.4 to 10.8 mg/L
5.	10.8 to 7.4 mg/L
21.	What was the median DO?
1.	8.6 mg/L
2.	9.0 mg/L
3.	9.1 mg/L
4.	9.2 mg/L
5.	9.3 mg/L
22.	Is there a trend in the DO concentration in the pond?
1.	Yes
2.	No
23.	What is the variance, S2, of the DO level in (mg/L)2?
1.	0.72
2.	0.85
3.	0.92
4.	0.95
5.	0.98
24.	What is the standard deviation, S, of the DO level in mg/L?
1.	0.72
2.	0.85
3.	0.92
4.	0.95
5.	0.98
25.	What is the geometric mean of the DO level in mg/L?
1.	8.5
2.	8.9
3.	9.0
4.	9.1
5.	9.2
REVIEW QUESTIONS:
Ponds receiving 0.3 MGD have overall dimensions of 600 ft by
800 ft with an average influent BOD of 170 mg/L. The average
water depth is 4.5 ft. Select the closest answer.
26.	What is the theoretical detention time in the ponds?
1.	35 days
2.	45 days
3.	55 days
4.	65 days
5.	75 days
27.	What is the organic loading?
1.	30 lb BOD/day/ac
2.	40 lb BOD/day/ac
3.	50 lb BOD/day/ac
4.	60 lb BOD/day/ac
5.	70 lb BOD/day/ac
END OF OBJECTIVE TEST

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Data Analysis 545
GRAPH PAPER

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CHAPTER 19
RECORDS AND REPORT WRITING
by
George Gribkoff
(with a supplement by John Brady)

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548 Treatment Plants
TABLE OF CONTENTS
Chapter 19. Records arid Report Writing
Page
OBJECTIVES	549
19.0	Need for Records and Report Writing	550
19.1	Records	550
19.10	Importance of Records	550
19.11	Type of Records	550
19.110	Operation Records	550
19.111	Physical Plant and Stock Inventory 	551
19.112	Maintenance Records	551
19.113	Financial or Cost Records	551
19.114	Personnel Records 	551
19.12	Frequency of Records	551
19.120	Daily Records	551
19.121	Monthly Records 	552
19.13	Keeping and Maintaining Monthly Records	552
19.14	Evaluation of Records	553
19.2	Report Writing	553
19.20	Importance of Reports	553
19.21	Major Principles of Report Writing 	553
19.22	Organization of the Report	554
19.23	Mechanics of Writing a Report 	554
19.24	Effective Writing	554
19.25	Types of Reports	555
19.250	Monthly Reports	555
19.251	Annual Reports	556
19.26	Obtain Reports by Other Operators	556
19.3	Typical Monthly Report	557
19.4	Emergency Planning		
19.5	Additional Reading	558

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Writing 549
OBJECTIVES
Chapter 19. RECORDS AND REPORT WRITING
Following completion of Chapter 19, you should be able to:
1.	Explain the importance of and need for records,
2.	Identify the different types of records,
3.	Evaluate records,
4.	Organize a report, and
5.	Write a report.

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550 Treatment Plants
CHAPTER 19. RECORDS AND REPORT WRITING
19.0 NEED FOR RECORDS AND REPORT WRITING
Most books on plant operation discuss record keeping
adequately but are very sketchy on their treatment of report
writing. However, report writing is the main means by which
those who have information communicate with those who need
it. Operators must communicate effectively with management
and the general public on the operation of their plant and on
requests for additional funds for improvements and personnel.
Any business transaction or operation requires records for
efficient management; this is also true for operation of waste
treatment facilities.
19.1 RECORDS
The administrator, superintendent, and operators of a
wastewater treatment facility should know the cost and effi-
ciency of their plant. Well-kept records will make the task of
writing treatment plant cost and efficiency reports much easier.
19.10 Importance of Records
Records are needed for the following reasons:
A.	Plant Operation. Review of operating records can indicate
the efficiency of the plant and its treatment units and past
and future problems.
B.	Records are needed to show type and frequency of main-
tenance of operating units and evaluation of the effective-
ness of maintenance programs. (See Chapter 15, "Main-
tenance.")
C.	Records can provide data upon which to base recom-
mendations for modifying plant operation and facilities.
D.	Records of past performance and operational procedures
are invaluable tools for the engineer in the evaluation of
present performance and serve as a basis for the design
of future treatment units.
E.	Records are used to support budget requests for person-
nel, additional facilities, or equipment.
F.	Records may be needed in damage suits brought against
your district or municipality. They can be especially helpful
to the operator if an accident occurs. As soon as possible
after an accident, someone should record the chain of
events leading to the accident, exactly what happened,
and any preventive or corrective action to be taken.
G.	Records are required in order to prepare NPDES reports.
Additional records containing water quality information
may be required by other public or private agencies.
H.	Records provide the actual data for the preparation of
weekly, monthly, or annual reports to administrative offi-
cials, the public, and regulatory agencies.
Records must be permanent, complete, and accurate. Write
entries clearly and neatly on data sheets in ink or with an
indelible pencil. A lead pencil should never be used because
notations can smudge and be altered or erased. False and
misleading records may actually do more harm than lack of
records.
Record keeping costs time and money, and only useful rec-
ords should be kept. Periodically records no longer useful
should be discarded. Lab analyses of receiving water quality
should be kept indefinitely. Some compromise is necessary
between collecting useless records and avoiding the frustra-
tions of not finding needed information. Keep your records neat
and organized. A record misfiled is a record lost, and a lost
record is worthless.
19.11 Type of Records
The type of records to be kept will depend on the size and
type of plant. A small primary plant may not require the number
or the variety of records required of large secondary or ad-
vanced wastewater treatment plants.
The specific records required will be determined by the size
and type of treatment processes in the plant and are discussed
more fully under respective chapters dealing with plant pro-
cesses. Typical data sheets are included at the ends of chap-
ters on Sedimentation and Flotation (Primary Plant), Trickling
Filters, Activated Sludge, Sludge Digestion and Handling, and
Ponds.
Records are generally separated into five classifications:
I.	Operation and performance records (including NPDES and
other regulatory records),
2.	Descriptive and inventory records of the physical plant and
stock,
3.	Maintenance records,
4.	Financial or cost record, and
5.	Personnel.
119.110 Operation Record*
The minimum amount of record keeping that may be re-
quired is as follows:
1. Daily records of flows into the plant,

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Writing 551
2.	Chemical, physical, and bacteriological characteristics of
influent and effluent,
3.	Amount of electrical power consumed,
4.	Amount of chlorine used, and
5.	Unusual happenings such as bypasses, floods, storms,
complaints, and other significant events. Any other unusual
event should be recorded if there is any possibility that a
record of these events may be needed in the future, either
for legal or administrative purposes. The main idea to keep
in mind is to record ONLY that data which may eventually
be used.
19.111	Physical Plant and Stock Inventory
As a minimum, the following records are essential for proper
evaluation of plant facilities and for making future recom-
mended modifications or additions.
1.	Contract and "as built" plans and specifications of waste
treatment facility. This includes detailed piping and wiring of
plant.
2.	Plans and operating instructions for plant equipment and
processes (plant O & M Manual).
3.	Costs of major equipment and unit items.
4.	A complete record and identification card for all major
equipment. The card should include name of manufacturer
and identifying code number.
5.	Lists of tools, materials, chemicals, lab reagents and
supplies, and office supplies.
6.	A record card for each industrial waste discharger contain-
ing information on type, quantity, characteristics, and times
of expected waste discharges.
19.112	Maintenance Records
See Chapter 15, "Maintenance."
19.113	Financial or Cost Records
Keep lists of purchases and expenses to date during fiscal
year. Comparisons should be made with budget allocation to
avoid excess purchases.
Public agencies and special districts usually have a purchas-
ing department that has the job of obtaining services, supplies
and equipment. This department must follow the laws of your
state and regulations of your agency. Operators must work
with purchasing departments and follow their procedures. If
your agency or organization does not have a purchasing de-
partment, you must develop procedures so you can obtain the
necessary services, supplies and equipment to keep your plant
performing properly.
When purchasing supplies, chemicals or other consumable
supplies, you first must locate a vendor (someone who will sell
you the supplies). Sometimes the "yellow pages" in the phone
book are the best place to start if you don't know a vendor or
where to begin. Once you've located what you want and com-
pared the prices and availability of the supplies of at least two
vendors, you must start the paper work to obtain the supplies.
Procedures vary with different agencies, but the purpose of
these procedures is to prevent dishonest people from cheating
the taxpaying public by fraudulent and illegal means.
Often the first step is for the operator to prepare a purchase
order (PO) which describes the supplies you wish to buy, the
cost and the name and address of the vendor. Keep one copy
for your files. Next, the PO goes to your purchasing depart-
ment to approve the purchase. The purchasing department
contacts the vendor and orders delivery of the suppplies. You
should be notified that the purchase is approved and that the
vendor has been notified to deliver the supplies. Once the
supplies have been delivered, you notify the auditor and au-
thorize payment to the vendor if you are satisfied with the
supplies delivered.
19.114 Personnel Records
Employee personnel records, including annual performance
ratings, should be maintained for each of the plant employees.
19.12 Frequency of Records
Records at most waste treatment facilities are kept daily and
on a monthly basis.
19.120 Dally Records
Data to be recorded will depend upon the type and size of
the plant. Specific record forms are contained at the end of
chapters pertaining to a particular type of treatment plant. One
of the most important daily records is a day-by-day diary or log
of events and operations during the day. A daily diary or log
should be maintained in every plant, and in large plants at each
section (such as lab, maintenance). The log may be a spiral
notebook or a standard daily diary made for that purpose.
The information entered in the plant log should be pertinent
only to plant functions. Log entries should include at the top of
the page the day of the week, the date, and the year. The
names of the operators working at the plant, and their arrival
and departure times, should also be included. Log entries
should be made during the day of various activities and prob-
lems as they develop. Do not wait until the end of the day to
write up the log as some items may be overlooked. If you will
take a few minutes to make log entries in the morning and
afternoon, you will develop a good log. Logs are beneficial to
you and to people who replace you during vacations, illnesses,
or leaves of absence. A well-kept log may prove very helpful to
the operating agency as legal evidence in certain court cases.
An example of one day's log entries in a small trickling filter
plant is outlined below:
Tuesday, June 10, 1979
J. Doakes, Operator. A Smith, Assistant Operator. G. Doe,
Maintenance Helper.
8:20 AM Made plant checkout, changed flow charts, No. 2
supernatant tube plugged on No. 2 digester,
cleared tube.
9 AM Started drawing sludge from bottom of No. 2 di-
gester to No. 1 sand bed.
9:15 AM Smith and Doe completed daily lubrication and
maintenance, put No. 2 filter recirculation pump
on, took No. 1 pump off.
10 AM Received three tons of chlorine, containers Nos.
1583,1296,495; returned two empty containers
Nos. 1891 and 1344. Replaced bad flex connec-
tor on No. 2 chlorine manifold header valve, and
connected container No. 495 on standby.
10.30 AM Collected and analyzed daily lab samples.
1:15 PM Pumped scum pit, 628 gallons to No. 1 digester.
1:30 PM Restored sludge pump No. 2 to operation by re-
moving plastic bottle cap from discharge ball
check.

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552 Treatment Plants
2:45 PM Smith and Doe hosed down filter distributor arms
and cleaned orifices. Doe smashed finger when
closing one of the end gates on filter arm. Sent
Doe to Dr. Jones, filled out accident report, and
notified Mr. Sharp of accident.
3:10 PM Stopped drawing sludge to No. 1 bed. Drew
18,000 gallons of sludge; sample in refrigerator
to be analyzed Wednesday.
3.20 PM Electrician from Delta Voltage Company in with
repaired motor for No. 2 effluent pump, Invoice
No. A-1824, motor installed and pump OK.
4:10 PM Doe back from doctor, stated he will lose finger-
nail, and required three stitches and tetanus
shot. Must go back next Thursday.
4:30 PM Plant checkout for tonight, put No. 2 chlorine con-
tainer on line, in case No. 1 should run empty
during the night.
HELPFUL TIP:
Many operators carry a pencil and pocket notebook with
them at all times on the job. During the day, they record all
events and items of importance and write the information in the
plant diary at the end of the day.
As an example, the minimum daily records kept at a fairly
large size treatment plant with digester tanks may include the
following items:
1.	Precipitation and weather temperature
2.	Raw wastewater flow (MGD from totalizer) (or cu m/day)
3.	Influent and effluent temperatures (°F) (or °C)
4.	pH of influent and effluent
5.	Grit (cu ft/mil gal) (or liters of grit per cu m of flow)
6.	Chlorine use (lbs) (or kg)
7.	Influent and effluent 5-day BOD, mgIL
8.	Influent and effluent suspended solids, mgIL
9.	Influent and and effluent settleable solids, mgIL
10.	Raw sludge (gal) (or liters or cu m)
pH
Total solids, %
Volatile solids, %
11.	Digested bottom sludge
Total solids, %
Volatile solids, %
pH
Volatile acids and alkalinity, mg IL
Temperature, °F (or °C)
12.	Gas produced (cu ft) (or cu m)
13.	Effluent chlorine residual (mg/L) and coliform count,
MPN/100 ml
14.	Any unusual influent characteristics such as appearance
or odors
19.121 Monthly Records
Monthly records should reflect the totals and averages of the
values recorded daily or at some other frequency. In some
cases, they should give maximum and minimum daily results,
such as maximum and minimum daily flows.
19.13 Keeping and Maintaining Monthly Records
WHEN RECORDING DATA, ALWAYS WRITE CLEARLY
AND NEATLY. Daily recorded data are usually written on
monthly data sheets. The monthly data sheet is designed to
meet the reporting needs of a particular plant and should have
all important data recorded that may be used later for prepara-
tion of monthly or annual reports. The NPDES reporting sheets
for regulatory agencies do not contain spaces for critical plant
operation information; therefore, they cannot be used as
monthly data sheets.
MONTHLY DATA SHEET (See Appendix)
The monthly data sheet may be a single 8V2 x 11 inch sheet
for a small plant with ponds, or it may be a number of sheets
pertinent to various treatment units in a secondary or ad-
vanced waste treatment plant.
Normally, every plant operator makes up a monthly data
sheet for the plant to record daily information. These sheets
are numbered down the left hand side to 31 to cover 31 days in
a month. Then from left to right across the sheet are marked off
different columns to record daily information. These columns
should contain the day of the week, weather conditions, plant
flow, influent and effluent temperature, pH, settleable solids,
BOD, raw sludge pumped, digester sludge drawn, gas produc-
tion, DO, and other pertinent information. A space for remarks
is helpful to record and explain unusual events.
Sometimes the operator may use two or three different
sheets to collect pertinent data. Since each plant is different,
the operator prepares the plant data sheet to record the data
needed for proper plant operation and for the requirements of
the agency and the regulatory agencies, including NPDES re-
port forms.
In addition to routine daily operation, maintenance and
wastewater characteristics, the monthly data sheet should con-
tain any unusual happenings that may affect interpretation of
results and preparation of a monthly report such as unusual
weather, floods, bypasses, breakdowns, or changes in opera-
tions or maintenance procedures.
A typical monthly data sheet (Appendix) and monthly report
(Section 19.3) for an activated sludge plant are at the end of
this chapter.

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Writing 553
19.14 Evaluation of Records
Records are not useful unless they are evaluated and used
as indicators of plant operation and maintenance. Records are
also useful as sources for reports to management or the public.
The recorded data should enable the operator to determine
how to operate and maintain the plant. The information shown
by the records should also indicate to you and your supervisor
the efficiency of each unit in the plant. Records kept on the
quality of the effluent and the receiving waters should be
analyzed for the discharge's effect on the receiving waters.
The importance of looking at and analyzing records FRE-
QUENTLY cannot be overemphasized.
Records should not only be analyzed item by item, but any
variation should be looked at carefully for its relation to another
source of data. For example, a sudden drop in temperature of
the influent might be accompanied by greatly increased flows.
This could indicate storm water inflows or infiltration of sewer
lines. Infiltration by storm waters also could influence the BOD
and suspended solids concentrations in the plant influent. Or,
one might observe a sudden increase in 5-day BOD levels in
the plant effluent. This may indicate a seasonal increase due to
beginning of cannery operations, or it may indicate a break-
down of industrial treatment facilities discharging untreated
wastes into the wastewater collection system.
Before any meaningful interpretation can be made of any
sudden variation in data, an expected range of values has to
be determined for the particular treatment unit under consid-
eration. This range of values will be based upon expected or
past performance.
For example, if average daily flows during weekdays were
around two million gallons per day and suddenly a flow of 1.5
million gallons per day was recorded, this may indicate mal-
functioning of metering equipment or a break in sewer lines or
a bypass ahead of the plant. Conversely, unusually high flows
may indicate storm water infiltration, surface water runoff flow-
ing into the system through manholes, or an unusual dump of
wastewater.
An excellent way to facilitate review of daily records and
detect sudden changes or trends is a prepared chart showing
values plotted against days. Unless results are plotted, slight
changes and trends can go undetected. The deviation from the
expected values may have been caused by unusual circum-
stances or an error in observation or analysis. Procedures for
plotting and interpreting data are provided in Chapter 18,
"Analysis and Presentation of Data."
QUESTIONS
Write your answers in a notebook and then compare your
answers with those on page 559.
19.1A Why is it important to keep records of plant operation?
19.1	B Why should unusual happenings be recorded and de-
scribed?
19.1C Why do many operators carry a pencil and pocket
notebook on the job?
19.1D Why should records frequently be reviewed and
analyzed?
19.2	REPORT WRITING
This section will cover the major principles and mechanics of
report writing, the type of report usually required of a plant
operator, and a discussion and example of effective writing.
To many, the thought of writing a report represents a task
that is to be approached with fear and with a sense of inade-
quacy. This need not be the case. Anyone who can read and is
willing to put forth the effort can prepare an adequate report.
The typical treatment plant operator may regard the writing of
reports as an unwelcome chore and thus may approach the
subject with a natural resistance.
You should approach the task of report writing as if your next
pay raise depended on a neat, organized, and brief report. One
operator's annual report was so well written that a local news-
paper used the report to develop a six-article series on the
treatment plant. The newspaper stories explained the opera-
tion of the plant and its effectiveness in protecting the fish life,
water supplies, and recreational uses of the receiving waters.
Shortly after the articles appeared in the newspaper the
operator received a substantial increase in salary.
19.20	Importance of Reports
A report serves many purposes. Reports can serve as the
basis of requests for additional budget and personnel, plant
additions, or changes in plant operation. A report also is a
means by which your ability, actions, and knowledge are
communicated to management and your supervisor. You
should consider a report as an opportunity to tell your story to
your supervisor, management, or the general public. Your abil-
ity to prepare and submit effective reports is one factor consid-
ered for advancement in your profession.
Furthermore, you and your plant operation are partially
judged by the information contained in your report, its style,
and its appearance. A poorly prepared report may result in an
impression that the plant is not operating efficiently; or, still
worse, it can result in little action on or rejection of recom-
mendations or requests.
You must do more than operate your plant efficiently; you
must demonstrate this to your supervisors, administrators, and
regulatory agencies in a clearly understandable and well-
prepared report.
The narrative type of report writing will be discussed first
because it is the non-routine part of a typical monthly, quar-
terly, or annual report.
19.21	Major Principles of Report Writing
Whatever the report or its size, there are some basic princi-
ples common to good report writing:
1.	Know the purpose and objective of your report.
2.	Tailor your report to the person or persons to whom it is
directed.
3.	Know your subject.
4.	Organize the report to present order of ideas in a logical
order.
5.	Use language in the report that will be understood by the
reader.
6.	Use facts and figures.
7.	Be as exact and brief as possible.
8.	Write effectively.
In starting to prepare a narrative report, the most important
questions are what is the purpose of this report and for whom
is it written? The next important step is the organization of the
ideas and subject matter in a logical order.

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554 Treatment Plants
19.22	Organization of the Report
There is no single way to organize a formal report. You must
remember that a written report does not necessarily organize
and present the material in the same order in which the infor-
mation was gathered. Organization means simply that the top-
ics in the report are set forth in logical sequence to tell the story
effectively.
Some reports may follow a general lormat such as:
A.	Brief statement of problem
B.	Summary
C.	Conclusions and recommendations
D.	Body of report
1.	Technical and administrative background
2.	Investigation details
3.	Any necessary supporting material to back up conclu-
sions and recommendations
4.	Appendix (if necessary) including detailed data and ta-
bles to support body of report
The conclusion and recommendation section of a report
should receive the most attention and review. Conclusions and
recommendations must be stated clearly and briefly and in
language that will be understood by your readers. Be sure that
your conclusions and recommendations are supported in the
body of your report.
A memorandum to a supervisor or a narrative portion in a
report should be checked for organization and content as fol-
lows:
1.	Is the material presented in an organized way?
2.	Is there duplication?
3.	Is there omission of an important item?
4.	Is the material presented really necessary to make your
point and support your conclusions or recommendations?
Unnecessary material in a communication or report only
serves to weaken your case by clouding the main issues.
The above list applies to almost any written communication
and can be summarized by the four Cs of good report writing:
Conciseness
Clearness
Completeness
Candor
19.23	Mechanics of Writing a Report
In the previous section, examples were given on organiza-
tional plans for formal reports; but what are the mechanics of
writing a memorandum, a short report, or a section in a larger
report?
Following are some guidelines for preparing a report:
A.	List ideas and topics you plan to cover in a report.
B.	Arrange the ideas in logical sequence.
C.	Gather supporting material needed to support the ideas to
be presented in the report.
D.	BEGIN WRITING — this is most important! Prepare a
rough draft of the report based on listed ideas and their
organization. At this stage of preparation, writing without
undue concern about sentence structure or grammar is
suggested. At this stage it is more important to record your
ideas. Later, when rewriting the preliminary draft, it is
much easier to eliminate unnecessary material than it is to
add to the report.
E.	Prepare conclusions and recommendations, if any, after
writing the main body of the report.
F.	Review preliminary draft for content, logical presentation
and organization, and eliminate any unnecessary informa-
tion. At this stage you can reorganize your order of pre-
sentation for a more effective report and check for simplic-
ity and understandability.
G.	Review report for sentence sense, spelling, grammar, and
briefness.
H.	Make another draft (if necessary).
I.	Have a colleague or supervisor review the draft if possi-
ble.
J. Finally, check your report for overall effectiveness:
1.	Will your initial statements create interest in the con-
tents of the report?
2.	Will the reader understand it?
3.	Is the presentation of ideas in logical order?
4.	Are major points emphasized?
5.	Has all irrelevant material been eliminated?
6.	Are the sentences direct and effective?
7.	Is the report neat and attractive?
8.	Does the report support your conclusions and recom-
mendations?
A report does not have to be a literary masterpiece. The
more factual and brief it is, the more likely it is to be favorably
considered.
19.24 Effective Writing
While the organization of a report and presentation of ideas
in a logical manner are the chief components of a good report,
effective writing is also necessary.

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Writing 555
Effective writing is simply the putting together of words in a
grammatically correct and brief manner, eliminating needless
words, expressions, and repetitions. A good technical report
impresses no one favorably if it is full of flowery and confusing
language.
If you wish to learn how to be a more effective writer, you
could enroll in an adult education class on effective writing.
Perhaps the teacher will allow you to bring your monthly re-
ports to class and will offer suggestions on how to improve
your writing. Another approach is to go to your local library and
borrow books on effective writing. Section 19.5, "Additional
Reading," lists several books that can help you develop and
improve your writing skills.
The next few paragraphs are provided to show you exam-
ples of different styles of writing.
Following are some examples of direct versus indirect writ-
ing and use of active voice as contrasted to the passive voice:
INDIRECT: This report which you requested in your letter of
December 15,1980, on the efficiency of the trickling filter units
is submitted for your approval. It is concerned with removal of
organic material and future operation using different size of
filter media.
DIRECT: As requested in your letter of December 15,1980,
the report on trickling filter efficiency for removal of organic
material and possible filter media size changes is submitted for
your approval.
Besides being more direct, we have used eleven words less,
or cut the sentence by 25 percent. Whenever possible, use
active sentence construction rather than passive.
PASSIVE: It is recommended that the monitoring of the
effluent be started immediately.
ACTIVE: Monitoring the effluent should start immediately.
Parallel sentence construction will make your sentence
clearer.
NON-PARALLEL The supervisor pointed out HOW Brown
opposed progress, HOW he encouraged the men to slow
down, THAT he never showed initiative, and THAT he could not
maintain the machines.
PARALLEL The supervisor pointed out THAT Brown op-
posed progress, THAT he encouraged the men to slow down,
THAT he never showed initiative, and THAT he could not main-
tain the machines.
19.25 Types of Reports
There are many types of reports ranging all the way from a
memorandum to an annual report to management.
Specifically, it may be (1) a monthly plant operation report,
(2) a report to a regulatory agency, such as a health depart-
ment, or (3) a quarterly or annual report to management or the
public.
19.250 Monthly Reports (See Section 19.3)
The monthly reports are used in the preparation of the an-
nual report. Preparation of the monthly report consists of the
following preliminary activities:
1.	Gathering daily records,
2.	Reviewing daily log sheets for any significant or unusual
events during the month, and
3.	Jotting down ideas that one wishes to include in the narra-
tive section of the report.
In small plants, a monthly report may consist mainly of data
sheets giving the pertinent facts on:
1.	Laboratory analyses and effectiveness of plant treatment
and its various units;
2.	Cost data on labor, chemicals and maintenance;
3.	Maintenance records;
4.	Remarks stating unusual significant events during the
month;
5.	Effect on receiving waters; and
6.	Conclusions and recommendations.
In some larger plants, a monthly report may be required in
addition to the monthly data sheets.
The monthly report is a brief summary of combined informa-
tion from the monthly data sheets and daily logs. The report is
put together in outline form with a dozen or so subheadings
required for a secondary plant. The reports are useful to
operators and supervisors to keep them informed of plant func-
tions and problem areas.
The subheadings may reflect the flow pattern through the
plant. The monthly report generally describes, in narrative
form, the physical characteristics, maintenance and operation
problems, and unusual events during the month.
MONTHLY REPORT
A.	Flow
1.	Total amount of flow passed through the plant for
month
2.	Maximum daily flow
3.	Minimum daily flow
4.	Average daily flow
5.	Flow meter problems
B.	Headworks
1.	Screening: shredding device, operation and mainte-
nance problems.
2.	Screen material removed, cu ft/MG (liters/cu m)
3.	Grit removed, cu ft/MG (liters/cu m)
4.	Unusual material in the wastewater, such as oil, silt,
odors
C.	Primary clarifiers
1.	Operation and maintenance problems
2.	Scum removal, note plugged scum lines
3.	Sludge pumped, solids concentration
4.	Influent and effluent characteristics
D.	Secondary treatment system
1.	Trickling filter
a.	Loading rates, average
b.	Recirculation rates, average
c.	Maintenance problems
d.	Removal efficiencies
2.	Activated sludge
a.	Loading rates, average
b.	Mixed liquor concentration, average
c.	Mixed liquor DO level
d.	Removal efficiencies
E.	Secondary clarifiers
1.	Operation and maintenance problems
2.	Sludge pumped, solids concentration
3.	Effluent characteristics

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556 Treatment Plants
F.	Chlorination
1.	Pounds (kg) of chlorine used/month
2.	Pounds (kg) of chlorine used/day, average
3.	Chlorine residuals
4.	Chlorinator problems
5.	Average dosage, mg/L
G.	Dechlorination
1.	Pounds (kg) of sulfur dioxide used/month
2.	Pounds (kg) of sulfur dioxide used/day, average
3.	Chlorine residuals before and after dechlorination
4.	Sulfur dioxide equipment problems
5.	Average dosage, mg/L
H.	Outfall
1.	Effluent characteristics
2.	General appearance and condition around plant dis-
charge
3.	Condition of receiving system
I.	Raw sludge pumps
1. Problems and maintenance
J. Digesters
1.	Raw sludge pumped to digesters, gallons (liters) and
percent solids
2.	Gas production (cu ft or cu m)
3.	Temperature, pH, volatile acids, alkalinity, volatile sol-
ids
4.	Operation problems and maintenance performed
5.	Volatile solids destruction
K. Sludge drying beds
1.	Gallons (liters) of sludge drawn
2.	Yards (cu m) of dry cake removed
3.	Moisture content of cake or pounds (kg) of dry solids
4.	Maintenance or cleaning problems
L. Gas system and boilers
1. Operation and maintenance
M. General
1.	Power failures
2.	Accidents
3.	Visitors
4.	Grounds and building maintenance
5.	Plant cost
a.	Operator-hours worked
b.	Equipment parts
c.	Power and fuel
d.	Chemicals
e.	Miscellaneous
19.251 Annual Reports
The annual report receives wider distribution and is the re-
port more likely to be reviewed by the public, management,
and other governmental agencies.
The annual report is, in part, a compilation of data obtained
in the monthly reports. This report summarizes the plant's
yearly efficiency and cost data. The report also contains an
analysis of plant operation costs and recommendations for
next year's operations.
In addition, an annual report should contain a short introduc-
tion to provide a background to the reader, giving a brief history
and reason for the report.
The body of the report should contain schematic drawings,
pictures, and other attractive graphs whenever possible, and
should include at least the following items:
a.	A letter of transmittal
b.	Conclusions and recommendations
c.	A brief description and schematic diagram of the system
d.	An organization chart showing the various functional divi-
sions and their chiefs
e.	A statistical summary of general plant data such as:
(1)	Population served,
(2)	Wastewater flows (maximum, average, minimum),
and
(3)	Plant unit data, percent removal and efficiency of vari-
ous units.
f. Body of report which includes a brief description and sup-
porting tables, graphs, or charts needed to back up final
recommended actions or requests on such topics as:
(1)	Wastewater quality,
(2)	Chlorination,
(3)	Screening,
(4)	Pumping,
(5)	Sludge digestion,
(6)	Receiving water quality (maps — summary data),
(7)	Maintenance and repair, and
(8)	Financial data such as assets, liabilities, revenue.
g. Appendix which includes summary data by month for the
annual report year giving minimum, maximum, and aver-
age values for:
(1)	General plant data,
(2)	Treatment unit data,
(3)	Loadings and efficiency of treatment,
(4)	Chemical, physical, and bacteriological data on in-
fluent and effluent, and
(5)	Chemical, physical, and bacteriological data on receiv-
ing waters.
Report writing can seem like a difficult task, especially for an
operator not experienced in report writing. But with guidelines
provided here, a review of effective writing, and some real
effort, anyone who can read can produce an effective report.
19.26 Obtain Reports by Other Operators
A very helpful guide to writing a report is to obtain a report
written by another operator. Usually a report may be obtained
by writing a nearby city or operator and asking for a copy. If you
explain that you are an operator and would appreciate a copy
of their report, your request will probably be granted. A REP-
RESENTATIVE OF A REGULATORY AGENCY OR YOUR
PLANT CONSULTING ENGINEER SHOULD BE ABLE TO
RECOMMEND TO YOU EXAMPLES OF WELL-WRITTEN RE-
PORTS.

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Writing 557
QUESTIONS
Write your answers in a notebook and then compare your
answers with those on page 559.
19.2A What is the purpose of writing monthly and annual
reports?
19.2B How could you obtain a copy of a report from another
plant?
19.3 TYPICAL MONTHLY REPORT
CLEANWATER TREATMENT PLANT
MONTHLY REPORT FOR JUNE 1980
by John Brady
FLOW: Cleanwater treated a total raw wastewater flow of
68.497 million gallons this month, with a daily average of 2.283
MG. There were no unusual flow conditions during the month.
GRIT CHANNEL: The grit channel was cleaned on 6/23, with
1.5 cubic yards of grit removed, consisting mainly of eggshells
and sand.
SCREENING: The top bearing of barminutor No. 1 travel
motor was replaced on 6/4 and a spring on the micro switch
was also replaced. A broken comb was replaced on the No. 2
barminutor on 6/15 and all combs on that unit were reset to
0.006 inch clearance.
RAW WASTEWATER PUMPS: No problems with No. 1 and
No. 3 pumps. No. 2 pump was repacked on 6/9.
PRIMARY CLARIFIERS: On 6/21 the No. 2 primary clarifier
was dewatered for annual inspection. The mechanism was in
good condition and only required resetting the clearance of the
brass plow squeegees to their original Va inch. The tank weirs
and scum baffle were wire brushed and repainted with 395-A.
The tank was returned to service on 6/26. While the No. 2
primary was out of service, the No. 1 primary carried the full
plant load without any detrimental effect on the efficiency of the
plant.
AERATOR: No problems. The aerator loading was main-
tained at 25 pounds of BOD per day per 100 pounds of mixed
liquor suspended solids, and a constant return sludge rate of
30%.
FINAL CLARIFIER AND RETURN SLUDGE PUMPS: No
operational problems with the final clarifier. The No. 2 return
sludge pump was returned from J & M Machine Shop on 6/1
and re-installed. J & M replaced the shaft sleeve and both shaft
bearings at a cost of $182.36 (Invoice No. 34475). However,
the pump was not ready for service unitl 6/2 as J & M had
packed the pump bearings with an all-purpose medium indus-
trial lubricant rather than the F.M. oil film low temperature
grease of -65° to 100°F, as specified.
CHLORINATION: No problems. Used 9950 pounds of
chlorine at an average rate of 335 pounds per day. One
hundred twenty-five pounds per day were used for post-
chlorination maintaining an average chlorine residual of 4.4
mgIL. Two hundred ten pounds per day were used for pre-
chlorination for odor control.
OUTFALL Other than the foam build up around the outfall
and the foam drift downstream for approximately 500 yards,
the receiving stream was in good condition. The stream sam-
pling below the outfall remained at 8.9 mg IL DO, 2.0 mgIL
BOD, and average temperature of 58°F.
RAW SLUDGE PUMP: On 6/9 and 6/30, the raw sludge
pump was plugged with a piece of plastic and a wooden stick
under the discharge ball check. In each case, the pump was
restored to service during the 8 AM shift.
DIGESTERS: Digester No. 1 was operated as the primary
and No.2 as the secondary. The temperature in the No. 1 tank
was raised from 91 °F to 94°F. During the month, the tank was
continuously mixed. The recirculated sludge contained an av-
erage volatile acids content of 150 mg/L, with the alkalinity at
2550 mg/L (volatile acid/alkalinity relationship of 0.06).
SLUDGE DRYING: Supernatant from the No. 2 digester be-
came heavy on 6/12 with the settleable solids ranging from 9 to
15% by volume. On 6/17, 28,000 gallons of digested sludge
was drawn from the No. 2 digester to the No. 3 drying bed to
reduce supernatant load. The drawn sludge contained 8.3%
solids with a volatile content of 52.6%.
The No. 1 and No. 4 drying beds were cleaned, yielding a
total of 63 cubic yards of dry sludge.
GAS SYSTEM AND BOILER: On 6/7 it was found that low
gas production was recorded for 6/6. The No. 2 digester pres-
sure relief was found to be venting at various times. The entire
gas system piping units were cleaned and inspected with the
problem location found on 6/13 in the gas meter itself. The
condensate and residue had gummed up the gear train from
the bellows slide arms. The unit was cleaned with kerosene,
relubricated with molly cote, and returned to service with no
further problems.
POWER SUPPLY: There were two power outages this
month, on 6/24 and 6/27, with the plant being out of service 40
to 45 minutes each time. The cause of the outages was due to
a service fuse dropping on one phase at the utility pole by the
main gate, leaving only the two phases from which to operate.
Each time, the main power board was shut down to protect
plant equipment.

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558 Treatment Plants
GENERAL
6/3 Replaced broken hinge on main gate.
6/6 Mosquito abatement personnel moved their oil storage
tank from the plant grounds.
6/15 Left main gate barricade chopped down by vandals.
6/17 Replaced left main gate barricade.
6/19 State Water Pollution Control engineer visited plant and
collected effluent samples.
6/24 Received 400 return sludge meter charts (Invoice No.
111323).
6/25 Flame-Out Fire Equipment Supply Company representa-
tive in and made yearly check on plant fire extinguishers.
Submitted: Is/ John J. Smith
Chief Operator
19.4 EMERGENCY PLANNING
Emergency planning is one more item that must be consid-
ered in order to insure that your treatment plant performs as
well as possible under all conditions. Your plant should have
written procedures that serve as a guide for operators on duty
when a disaster occurs. Potential disasters include:
1.	Hazardous spills reaching collection system,
2.	Storms and floods,
3.	Earthquakes,
4.	Nuclear attacks or accidents,
5.	Work stoppages,
6.	Physical injuries,
7.	Chlorine leaks,
8.	Fires, and
9.	Power failures.
Try to list the potential disasters that could occur at your
treatment plant. After you have listed the disasters, prepare
procedures for the operators to follow to overcome and correct
the situation.
These procedures should outline, on a step-by-step basis,
the items that should be considered.
1.	How to evaluate the seriousness of the problem,
2.	Who to notify regarding the disaster,
3.	What information will be needed by the persons notified,
4.	Where the necessary emergency, safety and repair equip-
ment and vehicles are located,
5.	How to obtain outside assistance if necessary,
6.	Sources of outside assistance, and
7.	Procedures to follow to repair or correct the situation.
How to respond to hazardous spills and chlorine leaks has
been discussed in appropriate chapters throughout this man-
ual. Also see Chapter 15, "Maintenance," Section 15.042,
"Emergencies." Your procedures should be short, easy to un-
derstand and practical.
QUESTION
Write your answer in a notebook and then compare your
answer with the one on page 559.
19.4A List five potential disasters that could occur at a
wastewater treatment plant.
19.5 ADDITIONAL READING
1.	MOP 11, pages 463-478*.
2.	NEW YORK MANUAL, pages 119-156.
3.	Stockwell, Richard E., THE STOCKWELL GUIDE FOR
TECHNICAL AND VOCATIONAL WRITING, The Cum-
mings Publishing Company, Inc., 2727 Sand Hill Road,
Menlo Park, California 94025. Price $6.25. Accompanying
Workbook. Price $2.95.
4.	Ulman, J., TECHNICAL REPORTING, 3rd Edition, Holt,
Rinehart and Winston, Inc., 383 Madison Avenue, New
York, New York 10017. Price $10.95.
5.	Glorfeld, L.E., Lauerman, D.A., and Stageberg, N.C., A
CONCISE GUIDE FOR WRITERS, 5th Edition, Holt,
Rinehart and Winston, Inc., 383 Madison Avenue, New
York, New York 10017. Price $5.95.
6.	"The Life and Times of Dan D. Water — Operator and
Author," DEEDS & DATA, Water Pollution Control Federa-
tion, 2626 Pennsylvania Ave., NW, Washington, D.C.
20037.
Part I. The Decision to Write. July 1978.
Part II. Prewriting Planning. August 1978.
Part III. Writing the Paper. September 1978,
Part IV. Reviewing the Paper. October 1978.
* Depends on edition

-------
Writing 559
SUGGESTED ANSWERS
Chapter 19. RECORDS AND REPORT WRITING
Answers to questions on page 553.
19.1 A Records are important to:
a.	Document plant performance, efficiency, and
problems,
b.	Justify budget requests,
c.	Provide design criteria for remodeling, expansion,
and new processes,
d.	Verify observations of plant operation,
e.	Help if legal action is threatened,
f.	Document quality of receiving waters,
g.	Report preparation for supervisors and regulatory
agencies,
h.	Identify significant departures from normal values
and take corrective action, and
i.	Show type and frequency of maintenance of
operating units.
If you recognized the importance of keeping records to
document plant performance and justify budgets, you
have identified the important concepts. See Section
19.10, "Importance of Records."
19.1B Unusual happenings should be recorded and de-
scribed because they have an important influence on
the interpretation of laboratory analyses describing
the operation and efficiency of your plant and the con-
dition of the receiving water. Also, they could prove
very helpful to the operator in case of an accident. See
Section 19.11, "Type of Records."
19.1C Many operators carry a pencil and pocket notebook on
the job to record all important events as they occur
during the day. See Section 19.12, "Frequency of
Records."
19.1 D Records should frequently be evaluated to determine
if your plant is operating properly and to identify any
developing difficulties before they can become serious
problems. See Section 19.14, "Evaluation of Rec-
ords."
Answers to questions on page 557.
19.2A The purpose of monthly and annual reports is to pro-
vide a brief description of the operation of your plant
for the benefit of management and regulatory agen-
cies. See Section 19.20, "Importance of Reports."
19.2B Write a letter to another operator or city and ask for a
copy of one of their reports. See Section 19.26, "Ob-
tain Reports by Other Operators."
Answer to question on page 558.
19.4A Potential disasters that could occur at a wastewater
treatment plant include:
1.	Hazardous spills,
2.	Storms and floods,
3.	Earthquakes,
4.	Nuclear attacks or accidents,
5.	Work stoppages,
6.	Physical injuries,
7.	Chlorine leaks,
8.	Fires, and
9.	Power failure.
Listing any five of these potential disasters will be
satisfactory. You may include a disaster that could
occur at your plant that we have overlooked. See sec-
tion 19.4, "Emergency Planning."

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560 Treatment Plants
OBJECTIVE TEST
(No Discussion and Review Questions)
Chapter 19. RECORDS AND REPORT WRITING
Please write your name and mark the correct answers on the
answer sheet as directed at the end of Chapter 1. There may
be more than one correct answer to each question.
1.	Well-kept records will make the task of writing reports
much easier.
1.	True
2.	False
2.	Entries on data sheets should be written in ink, because
lead pencil entries may smudge and can be altered or
erased.
1.	True
2.	False
3.	Rain is not related to the operation of wastewater treat-
ment plants.
1.	True
2.	False
4.	Unusual happenings should be logged.
1.	True
2.	False
5.	Usually complaints do not have to be logged.
1.	True
2.	False
6.	Operation records are the same as maintenance records.
1.	True
2.	False
7.	Inventory information is part of record keeping.
1.	True
2.	False
8.	Information about personnel is part of record keeping.
1.	True
2.	False
9.	Records can indicate the efficiency of a wastewater treat-
ment plant operation.
1.	True
2.	False
10.	Records represent legal information in a wastewater
treatment plant.
1.	True
2.	False
11.	Financial information is part of record keeping.
1.	True
2.	False
12.	Records are used to show when equipment maintenance
is needed.
1.	True
2.	False
13.	All wastewater treatment plants require the same types of
records.
1.	True
2.	False
14.	The style and appearance of a report can affect a reader's
judgment of the report.
1.	True
2.	False
15.	Reports are written only for regulatory agencies.
1.	True
2.	False
16.	The heavier or thicker a report, the better it is.
1.	True
2.	False
17.	A poorly prepared report could indicate that the author
doesn't know how to operate a wastewater treatment
plant.
1.	True
2.	False
18.	A report should be written for the expected readers.
1.	True
2.	False
19.	A good report would never contain a schematic drawing of
a system.
1.	True
2.	False
20.	Reports should be complete, but as concise as possible.
1.	True
2.	False
21.	The BEST source of information for a report on the opera-
tion of a wastewater treatment plant is
1.	Interviews with operators.
2.	Interviews with people living near the plant.
3.	Last year's report.
4.	Newspaper articles.
5.	Plant records.

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Writing 561
22.
1.	As a basis for design of a future plant.
2.	As a basis for firing an operator.
3.	For writing a newspaper article.
4.	In a court legal action.
5.	None of the above.
23.	Records are not useful unless they are
1.	Compiled in tables.
2.	Evaluated.
3.	Included in the annual report.
4.	Reduced to statistical parameters.
5.	Used as indicators of plant operation and maintenance.
24.	Which of the following entries should be made in the plant
log?
1.	Dates of future pollution control association meetings
2.	Heavy thunderstorm hit north end of town around 3 PM
and lasted for approximately 15 minutes
3.	Mayor Charles visited plant and discussed some re-
cent odor complaints by plant neighbors
4.	Smith cleaned clarifier weirs today
5.	Switched chlorine feed from No. 2 cylinder to No.1
25.	What types of plant records should be kept by an
operator?
1.	Complaints
2.	Income tax
3.	Inventory
4.	Maintenance
5.	Operation
26.	Plant records are important because they
1.	Help obtain NPDES permits.
2.	Keep equipment properly maintained.
3.	Provide data required by regulatory agencies.
4.	Provide essential information when a plant is modified
or expanded.
5.	Show type and frequency of maintenance of operating
units.
27.	Well written plant reports are important because they
1.	Can serve to justify a plant budget.
2.	Communicate to management the accomplishments of
you and your plant.
3.	Explain to the public the operation and function of your
plant.
4.	Improve effluent quality.
5.	Keep the operator from maintaining the equipment.
Books on report writing may be
1.	Borrowed from the plant engineer.
2.	Found in most homes.
3.	Obtained by writing the publisher.
4.	Obtained from a library.
5.	Of no use to an operator.
29.	Reports written by other operators are very helpful in pre-
paring a report. These reports may be obtained
1.	By asking another operator for a copy of one of his
reports.
2.	By asking your plant consulting engineer to help you
find a report.
3.	By buying one.
4.	By requesting a representative from a regulatory
agency to assist in finding a report.
5.	From an effective writing textbook.
30.	Effective writing means
1.	Avoiding repetitive statements.
2.	Determining the effectiveness of your plant.
3.	Eliminating needless words.
4.	Putting words together in a brief manner.
5.	Using correct grammar.
31.	Some of the basic principles of good report writing include
1.	Ability to read.
2.	Completion of an English course.
3.	Knowledge of the subject.
4.	Organizing the report to present ideas in a logical fash-
ion.
5.	Using facts and figures.
32.	A poorly prepared report may
1.	Convince the public that they shouldn't spend any
more money on the plant.
2.	Indicate that the operator doesn't care about the job.
3.	Indicate to management that you don't know what you
are doing.
4.	Indicate to the regulatory agency that the plant is not
operating efficiently.
5.	Prevent the operator from getting a pay raise.
Records are never used	28.

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562 Treatment Plants
REVIEW QUESTIONS
33.	Estimate the pounds of solids in a 440,000-gallon aeration
tank if the suspended solids concentration is 1600 mg/L.
1.	600
2.	700
3.	4000
4.	4100
5.	5900
34.	Calculate the percent reduction in volatile matter during
digestion if the raw sludge was 72% volatile matter and the
digested sludge is 51%.
1.	50%
2.	55%
3.	60%
4.	65%
5.	70%
35.	Determine the organic loading on a pond in pounds of
BOD per acre per day if the inflow is 1.0 MGD with a BOD
of 145 mg/L and the pond area is 24 acres.
1.	50 lbs BOD/day/ac
2.	55 lbs BOD/day/ac
3.	60 lbs BOD/day/ac
4.	65 lbs BOD/day/ac
5.	70 lbs BOD/day/ac
36.	Lab tests indicate a chlorine dose of 12 mg/L is necessary
for adequate disinfection of the plant effluent for a flow of
0.8 MGD. What should be the feed setting on the
chlorinator?
8 lbs/24 hr
10 lbs/24 hr
50 lbs/24 hr
80 lbs/24 hr
100 lbs/24 hr
END OF OBJECTIVE TEST
CONGRATULATIONS
You've worked hard and completed a very difficult program.

-------
MONTHLY RECORD
19	
CLE AN WATER, U.S. A.
WATER POLLUTION CONTROL PLANT
OPERATOR I
| 31VQ
DAY
WEATHER
n———————
FLOW - M6D
|rAW WASTEWATER
PRIM. EFF.
FINAL EFFLUENT
AERATION SYSTEM
SUMMARY DATA
TEMP.
X
a.
SETT SOLIDS
B.O.D.
1
I
B.O.D.
SUSRSOUDS
o
o*
X
a.
d
C>
ai
SUSP SOLIDS
D.O.
(0
Id
X
2


f*
66
0.1
<5-1
16
5
OA
3.5
7161
2180


tl
1.7
6412
0.7P6
68
4770

s
cum
tsa
79
7.3
7
I7C
102
117
60
05
6-1
14
6
0.5
3.1
7852


Z3C

1.0
7117
am
66
3217
TOTAL
13,740.31
30|
M
cum
IW
7^
7.3
13


107
73
0-2
6.8
8
8
1.6
3.S
7688
2335

22C
14
2.1
TJ35
0.713
70
4SI5


fn


















L


	.
1
	i



x~

MM
7T
TT
18
sn
170
156

Ofl
eh
¦a
IS

m

2541
7»
m
121
EH
iSBa

0?
5225
OPER. COST/MG TREATED
S 54.C2
H
1
	
1.782
13B
74
77
7.1
7±
7
12
ihj itij m %aa kxj ¦] ism mso g k^Si' it-u mr-1 e&j .
ir.MltLllll IIili!Hif4:llk«l[*»II1EE!r>':'tf:ll-^>4ir<
o
65
0
35li
OPER. COST/CAPITA/MO.
| 0.158
FLOW METER:
l AQT 22204-C
¦«» '53541
totaC3HH2Z
.M6
ELECTRIC METER:
I AST 7836
5670
TOTAL 2I69	
Mill T 40 Y VM .
RAW SLUDOE:
LAST	-MB 32.*
1st 4321B4
STROKES i£5M£_
Tfvrai atsMo y i.o , aesXo r.*i g
OAS METER:
LAST *»"">
1st
TOTAL JiaSS—FI8
RETURN SLU08E:
i »«rr CTtKOW
|„ CTBUgOO
TOTAL _S55*	MG
WASTE SLUD0E:
1 AST 134m
I »t 132560
TOTAL 1161 x WOO MG

-------
FINAL EXAMINATION
AND
SUGGESTED ANSWERS
FOR
VOLUME II

-------
566 Treatment Plants
FINAL EXAMINATION
VOLUME II
This final examination was prepared TO HELP YOU review
the material in Volume II. The questions are divided into four
types:
1.	True-false,
2.	Multiple choice,
3.	Short answers, and
4.	Problems.
To work this examination:
1.	Write the answer to each question in your notebook.
2.	After you have worked a group of questions (you decide
how many), check your answers with the suggested an-
swers at the end of this exam, and
3.	If you missed a question and don't understand why, reread
the material in the manual.
You may wish to use this examination for review purposes
when preparing for civil service and certification examinations.
Since you have already completed this course, you do not
have to send your answers to California State University, Sac-
ramento.
True-False
1.	Threaded diffusers should be tightened with a wrench to
prevent air leaks.
1.	True
2.	False
2.	If an activated sludge plant becomes upset, the first action
before making any changes is to check the plant data for
at least three previous weeks.
1.	True
2.	False
3.	Denitrification is most common when the sludge age is too
low.
1.	True
2.	False
4.	Microorganisms in anaerobic digesters obtain oxygen for
respiration (breathing) from air.
1.	True
2.	False
5.	Anaerobic digestion produces more gas per pound of vol-
atile matter added than per pound of volatile matter de-
stroyed.
1.	True
2.	False
6. Results from the pH test of digester contents is a better
test for controlling digester operation than the volatile
acid/alkalinity relationship.
1.	True
2.	False
7. All sludge digesters operate in an anaerobic condition.
1.	True
2.	False
8. Sludge will dry faster if it is put onto a sand drying bed
before it is completely digested.
1.	True
2.	False
9. Receiving water measurements are as important as the
in-plant measurements.
1.	True
2.	False
10. Water quality characteristics In receiving waters can vary
from place to place and from time to time at each place
1.	True
2.	False
11. Remote sampling locations are best for a river.
1.	True
2.	False
12. Everyone working in a wastewater treatment plant has the
responsibility of protecting themselves and other plant vis-
itors by establishing safety procedures and then by seeing
that they are followed.
1.	True
2.	False
13.	One operator may be assigned the job of correcting a
malfunctioning flow meter located in a manhole at the en-
trance to a treatment plant.
1.	True
2.	False
14.	You should wear gloves when cleaning pump casings to
protect your hands from dangerous sharp objects.
1.	True
2.	False

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Final Exam 567
15.	Do not allow open flames or smoking inside enclosed
spaces until after the area has been checked for explosive
atmospheres, toxic gases and oxygen deficiency and de-
termined satisfactory.
1.	True
2.	False
16.	Methane gas produced by anaerobic conditions is explo-
sive when mixed with the proper proportion of air.
1.	True
2.	False
17.	Always use a new approved type gasket when making
connections in a chlorine gas system.
1.	True
2.	False
18.	Glassware or equipment may be held in your bare hands
while heating in order to accurately control the rate of
heating.
1.	True
2.	False
19.	Pump and motor flanges must be parallel vertically and
axially.
1.	True
2.	False
20.	When shutting down a pump for a long period, open all
valves on suction, discharge, priming and water-seal lines.
1.	True
2.	False
21.	Test tubes are used for the settleable solids test.
1.	True
2.	False
22.	Do not pipet wastewater or polluted samples by mouth.
1.	True
2.	False
23.	The greatest errors produced in laboratory tests are usu-
ally caused by improper sampling, poor preservation, or
lack of enough mixing during compositing and testing.
1.	True
2.	False
24.	Hydrogen sulfide gas in the atmosphere is toxic to your
respiratory system, is both flammable and explosive under
certain conditions, and can cause corrosion.
1.	True
2.	False
25.	The settleability test is used to determine the ability of
trickling filter solids to separate from wastewater in the
final clarifier,
1.	True
2.	False
26.	If the results from the dissolved oxygen test in an aeration
tank indicate a DO of 0.8 mgIL, the actual DO in the aera-
tion tank could be almost zero.
1.	True
2.	False
27.	Increased alkalinity and decreased concentrations of vol-
atile acids are the first measurable changes that take
place when the process of anaerobic digestion is becom-
ing upset.
1.	True
2.	False
28.	The COD test is used to measure the strength of wastes
that are too toxic for the BOD test.
1.	True
2.	False
29.	One yard is longer than one meter.
1.	True
2.	False
30.	Report writing is the main means by which those who have
information communicate with those who need it.
1.	True
2.	False
Multiple Choice
1.	Collection system variables that could upset an activated
sludge process include
1.	Activities of collection system maintenance crews.
2.	Chlorination of return sludge flows.
3.	Cleaning operations by industries discharging into col-
lection systems.
4.	Increases in influent flows caused by storms.
5.	Recycling of digester supernatant.
2.	Which of the following precautions must be taken before
attempting to maintain or repair a surface aerator?
1.	Drain the aeration tank
2.	Lock out and tag the main power breaker
3.	Secure the header assembly before starting to work
4.	Shut down aerator
5.	Test the atmosphere for toxic and explosive gases
3.	To prevent sludge bulking from occurring, which of the
following items should be carefully controlled in an acti-
vated sludge plant?
1.	Aeration tank DO
2.	Filamentous growth
3.	Length of aeration time
4.	Return sludge rate
5.	Sludge age
4.	The effectiveness of the organisms in the aeration tank
depends on the
1.	Characteristics of the food supply.
2.	pH.
3.	Presence of inhibiting substances.
4.	Temperature.
5.	Time available for the reaction.
5.	Which of the following items are objectives of digester
mixing?
1.	Distribution of heat evenly throughout digester con-
tents
2.	Inoculation of raw sludge with microorganisms
3.	Prevention of formation of scum blanket
4.	Release of hydrogen sulfide gas
5.	Use of waste gas to run mixers

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568 Treatment Plants
6. Sludge should be pumped from the primary clarifier to the
digester several times a day to
1.	Keep the pump from becoming clogged.
2.	Maintain better conditions in the clarifier.
3.	Permit thicker sludge pumping.
4.	Prevent coning.
5.	Prevent temporary overloading of the digester.
7. Sludge should be withdrawn slowly from a digester to pre-
vent
8. Two types of measurements required in connection with
operating a treatment plant are
1.	Effluent and downstream.
2.	In-plant and receiving water.
3.	Temperature and dissolved oxygen.
4.	Temperature and receiving water.
5.	Upstream and downstream.
9. When working in an empty digester, an operator should
1.	Test for explosive gas mixtures.
2.	Test for hydrogen sulfide gas.
3.	Use explosion-proof lights.
4.	Ventilate the digester.
5.	Wear nonspark-causing shoes.
10. Which of the following are possible reasons why a pump
won't start?
1.	Air leaks in suction line
2.	Discharge head too high
3.	Loose connections
4.	Pump not primed
5.	Tripped circuit breakers
11. The frequency of a particular line plugging depends on the
1.	Number of bends, elbows and valves in the line.
2.	Pipe material.
3.	Routine maintenance performed on the line.
4.	Type of material passing through the line.
5.	Type of pump used to move the material.
12.	Level control systems in a wet well include
1.	Bubblers.
2.	Diaphragms.
3.	Electrodes.
4.	Floats.
5.	Hearts.
13.	If a flow meter appears to be operating improperly, the
operator should
1.	Check connections.
2.	Check need for lubrication of moving parts.
3.	Divert the flow to a different meter.
4.	Look for foreign objects in the system.
5.	Replace the meter scale.
14. Which of the following are basic laboratory safety rules?
1.	Always wear a lab coat or apron in the laboratory to
protect your skin and clothes.
2.	Always wear protective goggles or eye glasses at all
times in the laboratory.
3.	Good housekeeping is the best way to prevent acci-
dents.
4.	Never eat or smoke in the laboratory.
5.	Never work alone in the laboratory.
Obtaining good test results depends on which of the fol-
lowing factors?
1.	Collect samples when convenient
2.	Collect representative samples
3.	Preserve samples until they are analyzed
4.	Properly store samples for pH test
5.	Use proper sampling techniques
16. The COD test
1.	Estimates the nitrification oxygen demand only.
2.	Estimates the total oxygen consumed.
3.	Measures the biochemical oxygen demand.
4.	Measures the carbon oxygen demand.
5.	Provides results quicker than the BOD test.
17. Results from the settleability test of activated sludge solids
may be used to
1.	Calculate mixed liquor suspended solids.
2.	Calculate SDI.
3.	Calculate SVI.
4.	Calculate sludge age.
5.	Determine ability of solids to separate from liquid in
final clarifier.
18. Bar graphs can be used to show which of the following?
1.	Characteristics of data
2.	Dispersion of data
3.	Growth
4.	How to select proper data intervals
5.	Results of lab tests
19. A poorly prepared report may
1.	Convince the public that they shouldn't spend any
more money on the plant.
2.	Indicate that the operator doesn't care about the job.
3.	Indicate to management that you don't know what you
are doing.
4.	Indicate to the regulatory agency that the plant is not
operating efficiently.
5.	Prevent the operator from getting a pay raise.
20. Effective writing means
1.	Avoiding repetitive statements.
2.	Determining the effectiveness of your plant.
3.	Eliminating needless words.
4.	Putting words together in a brief manner.
5.	Using correct grammar.
1.	Coning.
2.	Forming a vacuum in the digester.
3.	Supernatant from overloading the plant.
4.	The possibility of an explosive gas mixture developing
in the digester.
5.	The possibility of the digester cover collapsing.

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Final Exam 569
Short Answers
1.	Define the following terms:
a.	Activated sludge
b.	Mixed liquor
c.	Absorption
d.	Bulking sludge
e.	Filamentous bacteria
f.	Biomass
g.	Nitrification
h.	Polymer
2.	Why is the COD test recommended instead of the BOD
test for operational control of the activated sludge pro-
cess?
3.	Effectiveness of the activated sludge treatment in treating
wastewater depends on what factors?
4.	Define the following terms:
a.	Anaerobic digestion
b.	Dewaterable
c.	Liquefaction
d.	Mesophilic bacteria
5.	What is the objective of good digester operation?
6.	Why should thin sludge not be pumped to a digester?
7.	Why is temperature measured in a digester?
8.	How would you operate a digester under normal operating
conditions?
9.	Define the following terms:
a.	Composite sample
b.	NPDES permit
10.	What toxic and harmful chemicals may be encountered by
operators?
11.	Why should you not depend on your nose to detect hydro-
gen sulfide gas over long periods of time?
12.	Define the term "cross connection."
13.	What is a "service record card?"
14.	Why should sprockets be replaced when replacing a chain
in a chain-drive unit?
15.	Define the following terms:
a.	Aliquot
b.	Amperometric
c.	Blank
d.	End point
e.	Reagent
16.	What are the most important forms of nitrogen in wastewa-
ter treatment?
17.	What three major factors can cause variations in lab test
results?
18.	Define the following terms:
a.	Arithmetic mean
b.	Median
c.	Geometric mean
19.	How would you analyze digester data in order to control
the operation of an anaerobic sludge digester?
20.	Why is it important to keep records of plant operation?
Problems
1.	An activated sludge plant treats a flow of 2.0 MGD with a
primary effluent suspended solids of 160 mgIL. The aera-
tion tank has a capacity of 60,000 cu ft and a mixed liquor
suspended solids concentration of 2100 mgIL. What is the
sludge age?
2.	An activated sludge plant is currently wasting sludge at a
rate of 20 GPM. What should be the new wasting rate in
GPM if an additional 1000 pounds of solids must be
wasted per day when the return sludge solids concentra-
tion is 5800 mg/L?
3.	What is the reduction in volatile solids in a digester if the
percent volatile entering the digester is 68 percent and the
percent leaving is 51 percent?
Given the following data:
100 ml sample
Crucible weight
Crucible plus dry solids
Crucible plus ash
Compute:
a.	Total suspended solids, mg/L
b.	Volatile suspended solids, mg/L
c.	Volatile solids, %
d.	Fixed suspended solids, mg/L
e.	Fixed solids, %
Given the following data:
Crucible weight
Crucible plus dry solids
Crucible plus wet solids
Compute percent sludge solids.
19.9138 g
20.0071 g
19.9432 g
19.91 g
22.49 g
68.34 g
6.	Results from the BOD test of a plant influent sample are as
follows:
Initial DO of Diluted Sample, mg/L	= 8.7 mg/L
DO of Diluted Sample After
5-Day Incubation, mg/L	= 3.2 mg/L
Sample Volume, ml	= 5 ml
Estimate the BOD in mg/L.
7.	If the total solids in a sample are 200 mg/L, what is the
percent solids?
Use the following information regarding an activated sludge
plant to answer questions 8 and 9.
Mixed Liquor Suspended Solids (MLSS)	= 2400 mg/L
Primary Effluent BOD, mg/L	=115 mg/L
Flow Rate, MGD	= 2.3 MGD
Aeration Tank Volume, cu ft	= 75,000 cu ft
8.	How many pounds of solids are in the aeration tank?
9.	What is the aeration tank loading in pounds of BOD per
day?


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570 Treatment Plants
10.	A pump is capable of delivering 6 horsepower to water
being pumped against a 25-ft head. Estimate the flow of
water being pumped in gallons per minute.
11.	A wet well 6 feet wide and 12 feet long is used to measure
the capacity of a pump. No flow is allowed to enter the wet
well during the test and the pump lowers the wet well 3.6
feet in 10 minutes. What is the pumping rate in gallons per
minute?
12.	What is the cost per day to operate a pump that pumps 1.5
MGD against a total dynamic head of 40 feet? The pump
has an efficiency of 60 percent and the motor an efficiency
of 90 percent. Assume one kilowatt hour costs 6 cents.
13.	Estimate the power required in kilowatts for a pump that
pumps 100 liters per second against a total dynamic head
of 10 meters. The pump has an efficiency of 60 percent
and the motor an efficiency of 90 percent.
14. How many cubic meters are there in a 50 mm diameter
pipe 0.8 kilometers long?
15. Given the effluent BOD for one week from an activated
sludge plant.
Day	S M T W T F S
BOD, mgIL	5 5 9 5 6 8 14
Determine:
a.
Arithmetic mean,
b.
Range,
c.
Median,
d.
Mode,
e.
Geometric mean, and
f.
Standard deviation.
SUGGESTED ANSWERS FOR FINAL EXAMINATION
VOLUME II
True-False
1.	False Threaded diffusers should be hand tightened so
they can be easily removed for maintenance.
2.	True If an activated sludge plant becomes upset, check
the plant data for the three previous weeks.
3.	False Denitrification is most common when the sludge
age is too high (extended aeration).
4.	False Anaerobic bacteria obtain their oxygen supply by
breaking down chemical compounds which con-
tain oxygen, such as sulfate. Explosive conditions
can develop in mixtures of air and gases produced
by anaerobic decomposition.
5.	False Anaerobic digestion produces more gas per pound
of volatile matter destroyed than per pound of vol-
atile matter added to the digester.
6.	False Results from the volatile acid/alkalinity relationship
of digester contents are the best method for con-
trolling digester operation, not pH.
7.	False Sludge digesters can be either aerobic or
anaerobic.
8.	False The better sludge is digested, the faster it will dry
in a drying bed.
9.	True Receiving water measurements are as important
as inplant measurements. In-plant measurements
are used to control processes and receiving water
measurements indicate the impact of the effluent
on receiving waters.
10. True Water quality characteristics in receiving waters
can vary from place to place (each sampling loca-
tion), and from time to time at each place.
11.	False Sampling locations should be easily accessible for
ease in maintaining sampling program and en-
couraging accurate sampling. Protection against
vandals must be provided.
12.	True Everyone is responsible for protecting themselves
and other plant visitors by establishing safety pro-
cedures and then seeing that they are followed.
13.	False Never allow one person to enter a manhole for any
reason without help present and available for res-
cue purposes.
14.	True Always wear gloves when cleaning pump casings
to protect your hands from dangerous sharp ob-
jects.
15.	True Open flames should not be allowed inside an en-
closed space until the atmosphere has been
checked for explosive atmospheres, toxic gases
and oxygen deficiency. The atmosphere must be
continuously ventilated and monitored while any-
body is working in the area.
16.	True Methane gas produced by anaerobic conditions is
explosive when mixed with the proper proportion
of air.
17.	True Always use a new approved type gasket when
making connections in a chlorine gas system,
18.	False Never hold any piece of glassware or equipment in
your bare hands while heating because you could
burn yourself.
19.	True Pump and motor flanges must be parallel vertically
and axially.

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Final Exam 571
20.	False When shutting down a pump for a long period,
SHUT all valves and drain pump completely by
removing vent and drain plugs to protect pump
against corrosion, sedimentation and freezing.
21.	False Test tubes are used for mixing small quantities of
chemicals. Imhoff cones are used for the settle-
able solids test.
22.	True Do not pipet wastewater or polluted samples by
mouth. Pipet both samples by mechanical means
to avoid taking a chance on severe illness or
death.
23.	True Errors in laboratory tests are usually caused by
improper sampling, poor preservation, and lack of
enough mixing during compositing and testing.
24.	True Hydrogen sulfide gas is toxic, flammable, explo-
sive and can cause corrosion.
25.	False The settleability test is used to determine the abil-
ity of activated sludge solids to separate from
wastewater in the final clarifier.
26.	True If results from a dissolved oxygen test indicate a
DO of less than 1.0 mgIL, the actual DO could be
almost zero. Considerable DO from the surround-
ing atmosphere could mix with the sample when it
is collected, when the inhibitor is added, while the
solids are settling, and when the sample is trans-
ferred to a BOD bottle for the DO test.
27.	False Increased concentrations of volatile acids and de-
creased alkalinity are the first measurable
changes that take place when the process of
anaerobic digestion is becoming upset.
28.	True The COD test is used to measure the strength of
wastes that are too toxic for the BOD test.
29.	False One meter is longer than one yard.
30.	True Report writing is the main means by which those
who have information communicate with those
who need it.
Multiple Choice
1 1,3,4 Collection system variables include ac-
tivities of maintenance crews, cleaning op-
erations by industry, and increased flows
caused by storms. Chlorination of return
sludge and recycling of supernatant are
plant variables.
2.	2, 4	Before starting work on a surface aerator,
shut down aerator and lock out and tag the
main power breaker.
3.	1, 2, 3, 4 All items are important to prevent sludge
bulking with the exception of the return
sludge rate which is important for controlling
septic sludge.
4.	1,2, 3, 4, 5 All five factors influence the effectiveness of
the organisms in the aeration tank.
5.	1,2,3 Objectives of digester mixing include even
distribution of food, organisms, heat and
prevention of scum blanket.
6.	2, 3, 4, 5 Sludge should be pumped to the digester to
improve conditions in clarifier, permit pump-
ing of thicker sludge, prevent coning and
prevent temporary overloading of digester.
Withdraw sludge from digester slowly to
prevent coning, forming a vacuum, develop-
ing explosive conditions and collapsing of
digester cover.
In-plant and receiving water are the two
types of measurements required in connec-
tion with operating a treatment plant.
All answers listed are important safety pre-
cautions when working in an empty digester.
Loose connections and tripped circuit
breakers are reasons why a pump will not
start.
All items listed influence the frequency of a
particular line plugging.
Level control systems in a wet well include
bubblers, diaphragms, electrodes and
floats.
If a flow meter appears to be operating im-
properly, check connections, need for lubri-
cation, and foreign objects in the system.
All items listed are basic laboratory safety
rules that must be observed at all times.
For good test results, collect representative
samples, preserve samples (that can be
preserved) until analyzed, and use proper
sampling techniques. Samples must be col-
lected at the proper time (not when conven-
ient) and pH tests must be run immediately
(samples for pH tests cannot be preserved).
The COD test provides results quicker than
the BOD test.
Results from the settleability test may be
used to calculate SVI and SDI and also to
determine ability of solids to separate from
liquid in final clarifier.
Bar graphs can be used to show characteris-
tics of data, dispersion of data, and results of
lab tests. Growth should be shown on trend
charts and selection of data intervals is not
the purpose of bar graphs.
19. 1, 2, 3, 4, 5 All of the items indicate problems that could
occur for the operator as a result of a poorly
prepared report.
7.	1,2,4,5
8.	2
9.	1, 2, 3, 4, 5
10.	3, 5
11.	1, 2, 3, 4, 5
12.	1,2,3,4
13.	1, 2, 4
14.	1, 2, 3,4, 5
15.	2, 3, 4
16.	5
17.	2, 3, 5
18.	1, 2, 5
20. 1, 3, 4, 5
Effective writing means avoiding repetitive
statements, eliminating needless words,
putting words together in a brief manner,
and using correct grammar.
Short Answers
1. Definitions.
ACTIVATED SLUDGE. Sludge particles produced in
raw or settled wastewater (primary effluent) by the
growth of organisms (including zoogleal bacteria) in
aeration tanks in the presence of dissolved oxygen.
The term "activated" comes from the fact that the par-
ticles are teeming with bacteria, fungi, and protozoa.
Activated sludge is different from primary sludge in
that the sludge particles contain many living or-
ganisms which can feed on the incoming wastewater.

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572 Treatment Plants
b.	MIXED LIQUOR. When activated sludge in an aera-
tion tank is mixed with primary effluent or the raw
wastewater and return sludge, this mixture is then re-
ferred to as mixed liquor as long as it is in the aeration
tank. When the mixed liquor flows from the aeration
tank it goes into the secondary clarifiers or final
sedimentation tanks. Mixed liquor also may refer to
the contents of mixed aerobic or anaerobic digesters.
c.	ABSORPTION. Taking in or soaking up of one sub-
stance into the body of another by molecular or chem-
ical action (as tree roots absorb dissolved nutrients in
the soil).
d.	BULKING SLUDGE. Clouds of billowing sludge that
occur throughout secondary clarifiers and sludge
thickeners when the sludge becomes too light and will
not settle properly.
e.	FILAMENTOUS BACTERIA. Organisms that grow in a
thread or filamentous form. Common types are thio-
thrix and actinomyces.
f.	BIOMASS. A mass or clump of living organisms feed-
ing on the wastes in wastewater, dead organisms and
other debris. This mass may be formed for, or function
as, the protection against predators and storage of
food supplies.
g.	NITRIFICATION. A process in which bacteria change
the ammonia and organic nitrogen in wastewater into
oxidized nitrogen (usually nitrate). The second-stage
BOD is sometimes referred to as the "nitrification
stage" (first-stage BOD is called the "carbonaceous
stage").
h.	POLYMER. A high-molecular-weight substance that is
formed by either a natural or synthetic process. Natu-
ral polymers may be of biological origin or derived
from starch products, cellulose derivatives, and alig-
nates. Synthetic polymers consist of simple sub-
stances that have been made into complex, high-
molecular-weight substances.
2. The COD test is recommended instead of the BOD test for
operational control because the results are available
within four hours instead of five days.
3. Effectiveness of the activated sludge treatment process in
treating wastewater depends on the AMOUNT OF ACTI-
VATED SLUDGE SOLIDS IN THE SYSTEM and the
HEALTH OF THE ORGANISMS which are a part of the
solids. To successfully maintain control of the solids and
health of the organisms requires continuous (seven days a
week) observation and checking by the plant operators.
4. Definitions.
a.	ANAEROBIC DIGESTION. Wastewater solids and
water (about 5% solids, 95% water) are placed in a
large tank where bacteria decompose the solids in the
absence of dissolved oxygen. At least two general
groups of bacteria act in balance: (1) SAPROPHYTIC
BACTERIA break down the complex solids to volatile
acids; and (2) METHANE FERMENTERS break down
the acids to methane, carbon dioxide, and water.
b.	DEWA TERABLE. This is a property of a sludge related
to the ability to separate the liquid portion from the
solid, with or without chemical conditioning. A material
is considered dewaterable if water will readily drain
from it.
c.	LIQUEFACTION. The conversion of large solid parti-
cles of sludge into very fine particles which either dis-
solve or remain suspended in water.
d.	MESOPHILIC BACTERIA. Medium temperature bac-
teria. A group of bacteria that grow and thrive in a
moderate temperature range between 68°F (20°C)
and 113°F (45°C). The optimum temperature range for
these bacteria in anaerobic digestion is 85°F (30°C) to
100°F (38°C).
5.	The objective of good digester operation is to maintain
suitable conditions in the digester for the microorganisms
that are reducing the volatile (organic) solids content of the
sludge.
6.	Reasons for not pumping a thin sludge include:
1.	Excess water requires more heat than may be avail-
able,
2.	Excess water reduces holding time of the sludge in the
digester, and
3.	Excess water forces seed sludge and alkalinity from
the digester.
7.	Temperature is measured in a digester to insure that the
optimum temperature is maintained for the mi-
croorganisms digesting the sludge.
8.	Normal operation of a digester requires proper:
1.	Feeding sludge to the digester,
2.	Maintaining the proper temperature,
3.	Keeping the contents of the digester mixed,
4.	Removing supernatant, and
5.	Withdrawing sludge.
9.	Definitions.
a.	COMPOSITE SAMPLE. A composite sample is a col-
lection of individual samples obtained at regular inter-
vals, usually every one or two hours during a 24-hour
time span. Each individual sample is combined with
the others in proportion to the flow when the sample
was collected. The resulting mixture (composite sam-
ple) forms a representative sample and is analyzed to
determine the average conditions during the sampling
period.
b.	NPDES PERMIT. National Pollutant Discharge Elimi-
nation System permit is the regulatory agency docu-
ment designed to control all discharges of pollutants
from point sources into U.S. waterways. NPDES per-
mits regulate discharges into navigable waters from
all point sources of pollution, including industries,
municipal treatment plants, large agricultural feed lots
and return irrigation flows.
10. Toxic and harmful chemicals that may be encountered by
operators include strong acids, bases and liquid mercury.
11 Do not rely on your nose to detect hydrogen sulfide gas
because your nose gets tired of the odor and quits detect-
ing the hydrogen sulfide.
12.	A cross connection is a connection between drinking (pot-
able) water and an unsafe water supply.
13.	The "service record card" should have the date and work
done, listed by item number and signed by the operator
who performed the service.

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Final Exam 573
14.	Always replace sprockets when replacing a chain because
old, out-of-pitch sprockets cause as much wear in a few
hours as years of normal operation.
15.	Definitions.
a.	ALIQUOT. Portion of a sample.
b.	AMPEROMETRIC. A method of measurement that
records electric current flowing or generated, rather
than recording voltage. Amperometric titration is a
means of measuring concentrations of certain sub-
stances in water.
c.	BLANK. A bottle containing only dilution water or dis-
tilled water, but the sample being tested is not added.
Tests are frequently run on a SAMPLE and a BLANK
and the differences compared.
d.	END POINT. Samples are titrated to the end point.
This means that a chemical is added, drop by drop, to
a sample until a certain color change (blue to clear, for
example) occurs which is called the END POINT of the
titration. In addition to a color change, an end point
may be reached by the formation of a precipitate or
the reaching of a specified pH. An end point may be
detected by the use of an electronic device such as a
pH meter.
e.	REAGENT. A substance which takes part in a chemi-
cal reaction and is used to measure, detect, or
examine other substances.
16.	The most important forms of nitrogen in wastewater treat-
ment are ammonia, organic, nitrate and nitrite.
17.	Variations in test results may be caused by changes in:
1.	Water or material (sludge) being examined,
2.	Sampling procedures, and
3.	Testing (analyst, procedure, reagents, equipment).
18.	Definitions.
a.	ARITHMETIC MEAN
Arithmetic Mean, X = Sum of All Measurements
Number of Measurements
b.	MEDIAN.
Median = Middle measurement when measurements
are ranked in order of magnitude (may fall
between two measurements).
C. GEOMETRIC MEAN.
1/n
Geometric Mean = (X, x X2 x - ¦ - XJ
19.	In order to analyze digester data and control digester op-
eration, calculate the volatile acid/alkalinity relationship.
This relationship should be plotted as soon as the lab
results are available. After every plot, the results should be
examined for any indication of an increasing trend. If an
increasing trend is detected, corrective action must be
taken.
20.	Records are important to:
a.	Document plant performance, efficiency and prob-
lems,
b.	Justify budget requests,
c.	Provide design criteria for remodeling, expansion, and
new processes,
d.	Verify observations of plant operation,
e.	Help if legal action is threatened,
f.	Document quality of receiving waters,
g.	Report preparation for supervisors and regulatory
agencies,
h.	Identify significant departures from normal values and
take corrective action, and
i.	Show type and frequency of maintenance of operating
units.
Problems
1.
Known
Flow, MGD
P.E. SS, mgIL
Tank, cu ft
MLSS, mgIL
= 2.0 MGD
= 160 mg/L
= 60,000 cu ft
= 2100 mgIL
Unknown
Sludge Age, days
Determine the pounds of suspended solids under aeration.
Aeration -
SS. lbs
(Tank Vol., MG)(MLSS, mg/L)(8.34 lbs/gal)
(60,000 cu ft)(7.48 gal/cu ft)(2100 mg/i)(8.34 lbs/gal)
1,000,000/M
- 7860 lbs SS
Determine the pounds of suspended solids added per day.
SS Added, = (Flow, MGD)(P.E. SS, mg/L)(8.34 lbs/gal)
lbs/day _ (2 0 MGD)(160 mg/L)(8.34 lbs/gal)
= 2670 lbs SS/day
Calculate the sludge age in days.
Sludge Age,
days
Suspended Solids Under Aeration, lbs
Suspended Solids Added, lbs/day
7860 lbs SS
2670 lbs SS/day
2.9 days
2.
Unknown
New Wasting Rate,
GPM
Known
Current Waste = 20 GPM
Rate, GPM
Additional Waste, = 1000 lbs/day
lbs/day
Return Sludge, = 5800 mg/i.
mgIL
Determine increase in wasting rate in GPM.
Increase in	Solids to be Wasted, lbs/day
(Return Sludge Cone., mg/L)(8.34 lbs/gal)
1000 lbs/day
(5800 mg/L)(8.34 lbs/gal)
-= 0.021 MGD
Calculate the new wasting rate in gallons per minute.
. Current
Wasting Rate,
MGD
New Wasting
Rate, GPM
_ Increase in
Wasting, GPM
= 21,000 gal/day
1440 min/day
= 14.6 GPM + 20 GPM
= 34.6 GPM
or try 35 GPM
Wasting, GPM
+ 20 GPM

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574 Treatment Plants
3.
Known	Unknown
VM In, % = 68% Reduction in Volatile Solids, %
VM Out, % = 51%
Calculate the percent reduction in volatile solids.
Reduction, % =
In - Out
x 100%
In - (In x Out)
(0.66 - 0.51) x 10qO/o
0.68 - (0.68)(0.51)
0.17
0.68 - 0.35
= 52%
x 100%
a.
Known
Sample size, ml	=100 ml
Crucible wt, g	= 19.9138
Crucible + dry sol, g	= 20.0071
Crucible + ash, g	= 19.9432
Total Suspended Solids
Determine dry weight of solids
Weight of Dried Sample & Dish, g
Weight of Dish (Tare Weight), g
Dry Weight, g
Unknown

a.
Total SS, mg/L
g
b.
Volatile SS, mg/L
g
c.
Volatile, %
g
d.
Fixed SS, mg/L

e.
Fixed, %
20.0071 g
19.9138 g
or
= 0.0933 g
=93.3 mg
Calculate total suspended solids in mg/L.
(Weight of Solids, mg) (1000 mlIL)
Total
Suspended
Solids, mgIL
Volume of Sample, ml
= <933 rng)(1000 ml IL)
100 rr»i
= 933 mg/L
b. Volatile Suspended Solids
Determine weight of volatile solids.
Weight of Dried Sample & Dish, g	= 20.0071 g
Weight of Ash & Dish, g	= 19.9432 g
Volatile Weight, g = 0.0639 g
or = 63.9 mg
Calculate volatile suspended solids in mg/L.
Volatile
Suspended (Weight of Volatile, mg)(1000 ml IL)
Solids, mg/L	Volume of Sample, ml
= (63.9 mg)(1000 ml IL)
100 ml
= 639 mg/L
c.	Percent Volatile Solids
Calculate the percent volatile solids.
Volatile _ (Weight Volatile, mg)(100%)
Solids, %	Weight Dry. mg
= (63-9 mg)(100%)
93.3 mg
= 68.5%
d.	Fixed Solids
Calculate the fixed solids in mg/L
Total Suspended Solids, mg/L
Volatile Suspended Solids, mg/L
Fixed Solids, mg/L
e.	Percent Fixed Solids
Calculate the percent fixed solids.
Fixed	_ (Weight Fixed, mg)(100%)
Solids, %	Weight Dry, mg
= (93.3 mg - 63.9) (100o/o)
93.3 mg
= 29 4 m9 100%
93.3 mg
= 31.5%
= 933 mg/L
= 639 mg/L
= 294 mg/L
Known
Crucible weight, g	= 19.91 g
Crucible plus dry solids, g= 22.49 g
Crucible plus wet solids, g = 68.34 g
Find weight of sample.
Weight of Dish plus Wet Solids, g
Weight of Dish, g
Weight of Sample, g
Find weight of total solids.
Weight of Dish plus Dry Solids, g
Weight of Dish, g
Weight of Total Solids, g
Calculate percent sludge solids.
Solids, % = 
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Final Exam 575
6.
11.
Known	Unknown
Initial DO, mgIL	= 8.7 mgIL BOD, mg/L
DO After 5 days, mg/L - 3.2 mg//.
Sample Volume, ml = 5 ml
Estimate the BOD of the influent sample.
r Initial DO After 1 f Bottle Vo1' ml.
BOD, mg/L
	ml "1
DO, mg/L 5 Days, mg/L J [_ Sample Vol, ml J
= (8.7 mg/L - 3.2 mg/L) f 300 ml "I
L 5 ml J
= 330 mg/L
7.
Known	Unknown
Total Solids, mg/L = 200 mg/L Total Solids, %
Convert total solids in mg/L into percent total solids.
Total Solids, % = 
Em, %
Calculate the power required in kilowatts.
Power
Required, = (Flow, L/sec)(1.0 kg/L)(9.807)(TDH, m)
KW	(Ep)(En)(1000 Watts/Kilowatt)
= (100 L/sec)(1.0 kg/L)(9.807)(10 m)
(0.60)(0.90)( 1000 W/KW)
= 18.2 KW


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576 Treatment Plants
14.
Pipe Volume,
cubic meters
Known	Unknown
Pipe Diameter, mm = 50 mm
Pipe Length, km = 0.8 km
Calculate the pipe volume in cubic meters.
Pipe Volume, cu m = !L (Diameter, m)J(Length, m)
4
-(0.8 km)(1000 m/km)
(50 mm)
15.
4 (1000 mm/m)
=	1.57 cu m
Known	Unknown
Effluent	a. Arithmetic Mean, mgIL
Day BOD, mg IL	b Range, mg/L
® ®	c. Median, mg IL
M O
T 9	d. Mode, mg/L
W 5	e. Geometric Mean, mg/L
T 6
p g	f. Standard Deviation, mg/L
S 14
= 7.4 mg/L
b. Calculate the range, mgIL
Range, mg/L = Largest Value - Smallest Value
= 14 mg/L - 5 mg/L
» 9 mg/L
c.	Determine the median.
Arrange the data in ascending (increasing) order.
Rank	1 2 3 4 5 6 7
Value, mg/L 5 5 5 6 8 9 14
Select the Median.
Median, mg/L = Middle measurement when measurements
ranked in order of magnitude
= 6 mg/L
d.	Determine the mode.
Mode, mg/L = Measurement that occurs most frequently
= 5 mg/L
e.	Determine the geometric mean.
Geo. Mean, = (X, x X2 x X3 Xn)1/n
mglL = (5x5x5x6x8x9x 14)17
= (756,000)°
=» 6.9 mg/L
,0.143
f. Determine the standard deviation.
Calculate the arithmetic mean, mg/L.
X
f
(X-X)
a
X
f(X-X)'
Arithmetic Mean, Sum of All Measurements
5
3
5-7.4
5.76
17.28
mg/L Number of Measurements
6
1
6-7.4
1.96
1.96
5 + 5 + 9+ 5 + 6 + 8+-14
8
1
8 - 7.4
0.36
0.36
7
9
1
9 - 7.4
2.56
2.56

14
1
14 - 7.4
43.56
43.56
7



Sf(X -~X)2
- 65.72
Std. Dev., mg/L = £f(X ' X)' j
-rfr
1/2
3.3 mg/L

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GLOSSARY
A Summary of the Words Defined
in
OPERATION OF WASTEWATER TREATMENT PLANTS

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578 Treatment Plants
Project Pronunciation Key
by Warren L. Prentice
The Project Pronunciation Key is designed to aid you in the
pronunciation of new words. White this key is based primarily
on familiar sounds, it does not attempt to follow any particular
pronunciation guide. This key is designed solely to aid
operators in this program.
You may find it helpful to refer to other available sources for
pronunciation help. Each current standard dictionary contains
a guide to its own pronunciation key. Each key will be different
from each other and from this key. Examples of the difference
between the key used in this program and the Webster's NEW
WORLD DICTIONARY "Key"1 are shown below.
In using this key, you should accent (say louder) the syllable
which appears in capital letters. The following chart is pre-
sented to give examples of how to pronounce words using the
Project Key.
SYLLABLE
WORD	1st 2nd
acid	AS	id
coagulant	co AGG
biological	BUY	o
The first word, ACID, has its first syllable accented. The
second word, COAGULANT, has its second syllable ac-
cented. The third word, BIOLOGICAL, has its first and third
syllables accented.
We hope you will find the key useful in unlocking the pro-
nunciation of any new word.
3rd
you
LODGE
4th
lent
ik
5th
cull
Ter m
Project Key
Webs ter Key
acid
A S-i d
as ad
co I i f o r m
CO A L-i -f o r m
ko-la-f o r m
biological
BUY-o-LODGE-ik-cull
bi-a-la j-i-kat
1 The Webster's NEW WORLD DICTIONARY, College Edition, 1968, was chosen rather than an unabridged dictionary because of its
availability to the operator.

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Glossary 579
GLOSSARY
ABS	ABS
Alkyl Benzene Sulfonate. A type of surfactant, or surface active agent, present in synthetic detergents in the United States before
1965. ABS was especially troublesome because it caused foaming and resisted breakdown by biological treatment processes. ABS
has been replaced in detergents by linear alkyl sulfonate (LAS) which is biodegradable.
ABSORPTION (ab-SORP-shun)	ABSORPTION
Taking in or soaking up of one substance into the body of another by molecular or chemical action (as tree roots absorb dissolved
nutrients in the soil).
ACID	ACID
(1) A substance that tends to lose a proton. (2) A substance that dissolves in water with the formation of hydrogen ions. (3) A
substance containing hydrogen which may be replaced by metals to form salts.
ACIDITY	ACIDITY
The capacity of water or wastewater to neutralize bases. Acidity is expressed in milligrams per liter of equivalent calcium carbonate.
Acidity is not the same as pH because water does not have to be strongly acidic (low pH) to have a high acidity. Acidity is a measure
of how much base can be added to a liquid without causing a great change in pH.
ACTIVATED SLUDGE (ACK-ta-VATE-ed sluj)	ACTIVATED SLUDGE
Sludge particles produced in raw or settled wastewater (primary effluent) by the growth of organisms (including zoogleal bacteria) in
aeration tanks in the presence of dissolved oxygen. The term "activated" comes from the fact that the particles are teeming with
bacteria, fungi, and protozoa. Activated sludge is different from primary sludge in that the sludge particles contain many living
organisms which can feed on the incoming wastewater.
ACTIVATED SLUDGE PROCESS (ACK-ta-VATE-ed sluj)	ACTIVATED SLUDGE PROCESS
A biological wastewater treatment process which speeds up the decomposition of wastes in the wastewater being treated. Activated
sludge is added to wastewater and the mixture (mixed liquor) is aerated and agitated. After some time in the aeration tank, the
activated sludge is allowed to settle out by sedimentation and is disposed of (wasted) or reused (returned to the aeration tank) as
needed. The remaining wastewater then undergoes more treatment.
ADSORPTION (add-SORP-shun)	ADSORPTION
The gathering of a gas, liquid, or dissolved substance on the surface or interface zone of another substance.
ADVANCED WASTE TREATMENT	ADVANCED WASTE TREATMENT
Any process of water renovation that upgrades treated wastewater to meet specific reuse requirements. May include general
cleanup of water or removal of specific parts of wastes insufficiently removed by conventional treatment processes. Typical
processes include chemical treatment and pressure filtration. Also called TERTIARY TREATMENT.
AERATION (air-A-shun)	AERATION
The process of adding air. In wastewater treatment, air is added to freshen wastewater and to keep solids in suspension. With
mixtures of wastewater and activated sludge, adding air provides mixing and oxygen for the microorganisms treating the wastewa-
ter.
AERATION LIQUOR (air-A-shun)	AERATION LIQUOR
Mixed liquor. The contents of the aeration tank including living organisms and material carried into the tank by either untreated
wastewater or primary effluent.
AERATION TANK (air-A-shun)	AERATION TANK
The tank where raw or settled wastewater is mixed with return sludge and aerated. The same as aeration bay, aerator, or reactor.

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580 Treatment Plants
AEROBES	AEROBES
Bacteria that must have molecular (dissolved) oxygen (DO) to survive.
AEROBIC (AIR-O-bick)	AEROBIC
A condition in which "free" or dissolved oxygen is present in the aquatic environment.
AEROBIC BACTERIA (AIR-O-bick back-TEAR-e-ah)	AEROBIC BACTERIA
Bacteria which will live and reproduce only in an environment containing oxygen which is available for their respiration (breathing),
namely atmospheric oxygen or oxygen dissolved in water. Oxygen combined chemically, such as in water molecules (H20), cannot
be used for respiration by aerobic bacteria.
AEROBIC DECOMPOSITION (AIR-O-bick)	AEROBIC DECOMPOSITION
The decay or breaking down of organic material in the presence of "free" or dissolved oxygen.
AEROBIC DIGESTION (AIR-O-bick)	AEROBIC DIGESTION
The breakdown of wastes by microorganisms in the presence of dissolved oxygen. Waste sludge is placed in a large aerated tank
where aerobic microorganisms decompose the organic matter in the sludge. This is an extension of the activated sludge process.
AEROBIC PROCESS (AIR-O-bick)	AEROBIC PROCESS
A waste treatment process conducted under aerobic (in the presence of "free" or dissolved oxygen) conditions.
AGGLOMERATION (a-GLOM-er-A-shun)	AGGLOMERATION
The growing or coming together of small scattered particles into larger floes or particles which settle rapidly. Also see FLOC.
AIR BINDING	AIR BINDING
The clogging of a filter, pipe or pump due to the presence of air released from water.
AIR GAP
AIR GAP	'	AIR GAP
(MIIMKIMO	nin
DAIMKIMO
WATER
An open vertical drop, or vertical empty space, between a drinking (potable) water	^
supply and the point of use in a wastewater treatment plant. This gap prevents	* ll,
back siphonage because there is no way wastewater can reach the drinking water.
OWN
TANK
IPiM*J"~
AIR LIFT	AIR LIFT
A special type of pump. This device consists of a vertical riser pipe submerged in the wastewater or sludge to be pumped.
Compressed air is injected into a tail piece at the bottom of the pipe. Fine air bubbles mix with the wastewater or sludge to form a
mixture lighter than the surrounding water which causes the mixture to rise in the discharge pipe to the outlet. An air-lift pump works
similar to the center stand in a percolator coffee pot.
AIR PADDING	AIR PADDING
Pumping dry air into a container to assist with the withdrawal of a liquid or to force a liquid gas such as chlorine or sulfur dioxide out
of a container.
ALGAE (AL-gee)	ALGAE
Microscopic plants which contain chlorophyll and float or are suspended and live in water. They also may be attached to structures,
rocks, or other similar substances.
ALIQUOT (AL-li-kwot)	ALIQUOT
Portion of a sample.
ALKALI	ALKALI
Any of certain soluble salts, principally of sodium, potassium, magnesium, and calcium, that have the property of combining with
acids to form neutral salts and may be used in chemical processes such as water or wastewater treatment.
ALKALINITY (AL-ka-LIN-ity)	ALKALINITY
The capacity of water or wastewater to neutralize acids. This capacity is caused by the water s content of carbonate, bicarbonate,
hydroxide, and occasionally borate, silicate, and phosphate. Alkalinity is expressed in milligrams per liter of equivalent calcium
carbonate. Alkalinity is not the same as pH because water does not have to be strongly basic (high pH) to have a high alkalinity.
Alkalinity is a measure of how much acid can be added to a liquid without causing a great change in pH.

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Glossary 581
AMBIENT TEMPERATURE (AM-bee-ent)	AMBIENT TEMPERATURE
Temperature of the surroundings.
AMPEROMETRIC (am-PURR-o-MET-rick)	AMPEROMETRIC
A method of measurement that records electric current flowing or generated, rather than recording voltage. Amperometric titration is
a means of measuring concentrations of certain substances in water.
ANAEROBES	ANAEROBES
Bacteria that do not need molecular (dissolved) oxygen (DO) to survive.
ANAEROBIC (AN-air-O-bick)	ANAEROBIC
A condition in which "free" or dissolved oxygen is NOT present in the aquatic environment.
ANAEROBIC BACTERIA (AN-air-O-bick back-TEAR-e-ah)	ANAEROBIC BACTERIA
Bacteria that live and reproduce in an environment containing no "free" or dissolved oxygen. Anaerobic bacteria obtain their oxygen
supply by breaking down chemical compounds which contain oxygen, such as sulfate (S04).
ANAEROBIC DECOMPOSITION (AN-air-O-bick)	ANAEROBIC DECOMPOSITION
The decay or breaking down of organic material in an environment containing no "free" or dissolved oxygen.
ANAEROBIC DIGESTION (AN-air-O-bick)	ANAEROBIC DIGESTION
Wastewater solids and water (about 5% solids, 95% water) are placed in a large tank where bacteria decompose the solids in the
absence of dissolved oxygen. At least two general groups of bacteria act in balance: (1) SAPROPHYTIC bacteria break down
complex solids to volatile acids, and (2) METHANE FERMENTERS break down the acids to methane, carbon dioxide, and water.
ANHYDROUS (an-HI-drous)	ANHYDROUS
Very dry. No water or dampness is present.
ANION	ANION
A negatively charged ion in an electrolyte solution, attracted to the anode under the influence of electric potential.
ASEPTIC (a-SEP-tick)	ASEPTIC
Free from the living germs of disease, fermentation or putrefaction. Sterile.
ASPIRATE (ASS-per-RATE)	ASPIRATE
Use of a hydraulic device (aspirator or eductor) to create a negative pressure (suction) by forcing a liquid through a restriction, such
as a Venturi. An aspirator (the hydraulic device) may be used in the laboratory in place of a vacuum pump; sometimes used instead
of a sump pump.
BOD (BEE-OH-DEE)	BOD
Biochemical Oxygen Demand. The rate at which microorganisms use the oxygen in water or wastewater while stabilizing decom-
posable organic matter under aerobic conditions. In decomposition, organic matter serves as food for the bacteria and energy
results from its oxidation.
BTU (BEE-TEA-YOU)	BTU
British Thermal Unit. The amount of heat required to raise the temperature of one pound of water one degree Fahrenheit.
BACTERIA (back-TEAR-e-ah)	BACTERIA
Bacteria are living organisms, microscopic in size, which consist of a single cell. Most bacteria utilize organic matter for their food
and produce waste products as the result of their life processes.
BACTERIAL CULTURE (back-TEAR-e-al)	BACTERIAL CULTURE
In the case of activated sludge, the bacterial culture refers to the group of bacteria classed as AEROBES, and facultative organisms,
which covers a wide range of organisms. Most treatment processes in the United States grow facultative organisms which utilize the
carbonaceous (carbon compounds) BOD. Facultative organisms can live when oxygen resources are low. When "nitrification" is
required, the nitrifying organisms are OBLIGATE AEROBES (require oxygen) and must have at least 0.5 mg/L of dissolved oxygen
throughout the whole system to function properly.
BAFFLE	BAFFLE
A flat board or plate, deflector, guide or similar device constructed or placed in flowing water, wastewater, or slurry systems to cause
more uniform flow velocities, to absorb energy, and to divert, guide, or agitate liquids.

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582 Treatment Plants
BASE	BASE
A compound which dissociates in aqueous solution to yield hydroxyl ions.
BATCH PROCESS	BATCH PROCESS
A treatment process in which a tank or reactor is filled, the water is treated, and the tank is emptied. The tank may then be filled and
the process repeated.
BIOASSAY (BUY-o-ass-SAY)	BIOASSAY
(1) A way of showing or measuring the effect of biological treatment on a particular substance or waste, or (2) a method of
determining toxic effects of industrial wastes or other wastes by using live organisms such as fish for test organisms.
BIOCHEMICAL OXYGEN DEMAND (BOD)	BIOCHEMICAL OXYGEN DEMAND (BOD)
The rate at which microorganisms use the oxygen in water or wastewater while stabilizing decomposable organic matter under
aerobic conditions. In decomposition, organic matter serves as food for the bacteria and energy results from its oxidation.
BIOCHEMICAL OXYGEN DEMAND (BOD) TEST	BIOCHEMICAL OXYGEN DEMAND (BOD) TEST
A procedure that measures the rate of oxygen use under controlled conditions of time and temperature. Standard test conditions
include dark incubation at 20°C for a specified time (usually five days).
BIODEGRADABLE (BUY-o-dee-GRADE-able)	BIODEGRADABLE
Organic matter that can be broken down by bacteria to more stable forms which will not create a nuisance or give off foul odors.
BIODEGRADATION (BUY-o-de-grah-DAY-shun)	BIODEGRADATION
The breakdown of organic matter by bacteria to more stable forms which will not create a nuisance or give off foul odors.
BIOFLOCCULATION (BUY-o-flock-u-LAY-shun)	BIOFLOCCULATION
The clumping together of fine, dispersed organic particles by the action of certain bacteria and algae. This results in faster and more
complete settling of the organic solids in wastewater.
BIOMASS (BUY-o-MASS)	BIOMASS
A mass or clump of living organisms feeding on the wastes in wastewater, dead organisms and other debris. This mass may be
formed for, or function as, the protection against predators and storage of food supplies. Also see ZOOGLEAL MASS.
BLANK	BLANK
A bottle containing only dilution water or distilled water, but the sample being tested is not added. Tests are frequently run on a
SAMPLE and a BLANK and the differences compared.
BLINDING	BLINDING
The clogging of the filtering medium of a microscreen or a vacuum filter when the holes or spaces in the media become sealed off
due to a buildup of grease or the material being filtered.
BOUND WATER	BOUND WATER
Water contained within the cell mass of sludges or strongly held on the surface of colloidal particles.
BREAKOUT OF CHLORINE	BREAKOUT OF CHLORINE
A point at which chlorine leaves solution as a gas because the chlorine feed rate is too high. The solution is saturated and cannot
dissolve any more chlorine.
BREAKPOINT CHLORINATION	BREAKPOINT CHLORINATION
Addition of chlorine to water or wastewater until the chlorine demand has been satisfied and further additions of chlorine result in a
residual that is directly proportional to the amount added beyond the breakpoint.
BUFFER	BUFFER
A solution or liquid whose chemical makeup neutralizes acids or bases without a great change in pH.
BUFFER ACTION	BUFFER ACTION
The action of certain ions in solution in opposing a change in hydrogen-ion concentration.
BUFFER CAPACITY	BUFFER CAPACITY
A measure of the capacity of a solution or liquid to neutralize acids or bases. This is a measure of the capacity of water or
wastewater for offering a resistance to changes in pH.

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Glossary 583
BUFFER SOLUTION	BUFFER SOLUTION
A solution containing two or more substances which, in combination, resist any marked change in pH following addition of moderate
amounts of either strong acid or base.
BULKING (BULK-ing)	BULKING
Clouds of billowing sludge that occur throughout secondary clarifiers and sludge thickeners when the sludge becomes too light and
will not settle properly.
CALORIE (KAL-o-ree)	CALORIE
The amount of heat required to raise the temperature of one gram of water one degree Celsius.
CARBONACEOUS STAGE (car-bun-NAY-shus)	CARBONACEOUS
A stage of decomposition that occurs in biological treatment processes when aerobic bacteria, using dissolved oxygen, change
carbon compounds to carbon dioxide. Sometimes referred to as "first-stage BOD" because the microorganisms attack organic or
carbon compounds first and nitrogen compounds later. Also see NITRIFICATION STAGE.
CATHODIC PROTECTION (ca-THOD-ick)	CATHODIC PROTECTION
An electrical system for prevention of rust, corrosion, and pitting of steel and iron surfaces in contact with water, wastewater or soil.
CATION EXCHANGE CAPACITY	CATION EXCHANGE CAPACITY
The ability of a soil or other solid to exchange cations (positive ions such as calcium, Ca+2) with a liquid.
CAVITATION (CAV-i-TAY-shun)	CAVITATION
The formation and collapse of a gas pocket or bubble on the blade of an impeller. The collapse of this gas pocket or bubble drives
water into the impeller with a terrific force that can cause pitting on the impeller surface.
CENTRATE	CENTRATE
The water leaving a centrifuge after most of the solids have been removed.
CENTRIFUGE	CENTRIFUGE
A mechanical device that uses centrifugal or rotational forces to separate solids from liquids.
CHEMICAL EQUIVALENT	CHEMICAL EQUIVALENT
The weight in grams of a substance that combines with or displaces one gram of hydrogen. Chemical equivalents usually are found
by dividing the formula weight by its valence.
CHEMICAL OXYGEN DEMAND or COD	CHEMICAL OXYGEN DEMAND or COD
A measure of the oxygen-consuming capacity of inorganic and organic matter present in wastewater. COD is expressed as the
amount of oxygen consumed from a chemical oxidant in mg/L during a specific test. Results are not necessarily related to the
biochemical oxygen demand because the chemical oxidant may react with substances that bacteria do not stabilize.
CHEMICAL PRECIPITATION	CHEMICAL PRECIPITATION
(1) Precipitation induced by addition of chemicals. (2) The process of softening water by the addition of lime or lime and soda ash as
the precipitants.
CHLORAMINES (KLOR-a-means)	CHLORAMINES
Chloramines are compounds formed by the reaction of chlorine with ammonia.
CHLORINATION (KLOR-i-NAY-shun)	CHLORINATION
The application of chlorine to water or wastewater, generally for the purpose of disinfection, but frequently for accomplishing other
biological or chemical results.
CHLORINE DEMAND	CHLORINE DEMAND
Chlorine demand is the difference between the amount of chlorine added to wastewater and the amount of residual chlorine
remaining after a given contact time. Chlorine demand may change with dosage, time, temperature, pH, and nature and amount of
the impurities in the water.
Chlorine Demand, mg/L = Chlorine Applied, mg/L - Chlorine Residual, mg/L
CHLORINE REQUIREMENT	CHLORINE REQUIREMENT
The amount of chlorine which is needed for a particular purpose. Some reasons for adding chlorine are reducing the number of
coliform bacteria (Most Probable Number), obtaining a particular chlorine residual, or destroying some chemical in the water. In
each case a definite dosage of chlorine will be necessary. This dosage is the chlorine requirement.

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584 Treatment Plants
CHLORORGANIC (chloro-or-GAN-nick)	CHLORORGANIC
Chlororganic compounds are organic compounds combined with chlorine. These compounds generally originate from, or are
associated with, living or dead organic materials.
CILIATES (SILLY-ates)	CILIATES
A class of protozoans distinguished by short hairs on all or part of their bodies.
CLARIFICATION (KLAIR-i-fi-KAY-shun)	CLARIFICATION
Any process or combination of processes the main purpose of which is to reduce the concentration of suspended matter in a liquid.
CLARIFIER (KLAIR-i-fire)	CLARIFIER
Settling Tank, Sedimentation Basin. A tank or basin in which wastewater is held for a period of time, during which the heavier solids
settle to the bottom and the lighter material will float to the water surface.
COAGULANT AID	COAGULANT AID
Any chemical or substance used to assist or modify coagulation.
COAGULANTS (co-AGG-you-lents)	COAGULANTS
Chemicals that cause very fine particles to clump together into larger particles. This makes it easier to separate the solids from the
liquids by settling, skimming, draining or filtering.
COAGULATION (co-AGG-you-LAY-shun)	COAGULATION
The use of chemicals that cause very fine particles to clump together into larger particles. This makes it easier to separate the solids
from the liquids by settling, skimming, draining or filtering.
COLIFORM (COAL-i-form)	COLIFORM
One type of bacteria. The presence of coliform-group bacteria is an indication of possible pathogenic bacterial contamination. The
human intestinal tract is one of the main habitats of coliform bacteria. They may also be found in the intestinal tracts of warm-
blooded animals, and in plants, soil, air, and the aquatic environment. Fecal coliforms are those conforms found in the feces of
various warm-blooded animals; whereas the term "coliform" also includes other environmental sources.
COLLOIDS (KOL-loids)	COLLOIDS
Very small, finely divided solids (particles that do not dissolve) that remain dispersed in a iiquid for a long time due to their small size
and electrical charge.
COLORIMETRIC MEASUREMENT	COLORIMETRIC MEASUREMENT
A means of measuring unknown concentrations of water quality indicators in a sample by measuring the sample s color intensity.
The color of the sample after the addition of specific chemicals (reagents) is compared with colors of known concentrations.
COMBINED AVAILABLE CHLORINE	COMBINED AVAILABLE CHLORINE
The concentration of chlorine which is combined with ammonia (NH3) as chloramine or as other chloro derivatives, yet is still
available to oxidize organic matter.
COMBINED AVAILABLE RESIDUAL CHLORINE	COMBINED AVAILABLE RESIDUAL CHLORINE
That portion of the total residual chlorine which remains in water or wastewater at the end of a specified contact period and reacts
chemically and biologically as chloramines or organic chloramines.
COMBINED RESIDUAL CHLORINATION	COMBINED RESIDUAL CHLORINATION
The application of chlorine to water or wastewater to produce a combined chlorine residual. The residual may consist of chlorine
compounds formed by the reaction of chlorine with natural or added ammonia (NH3) or with certain organic nitrogen compounds.
COMBINED SEWER	COMBINED SEWER
A sewer designed to carry both sanitary wastewaters and storm- or surface-water runoff.
COMMINUTION (com-mi-NEW-shun)	COMMINUTION
Shredding. A mechanical treatment process which cuts large pieces of wastes into smaller pieces so they won't plug pipes or
damage equipment. COMMINUTION and SHREDDING usually mean the same thing.
COMMINUTOR (com-mi-NEW-ter)	COMMINUTOR
A device to reduce the size of the solid chunks in wastewater by shredding (comminuting). The shredding action is like many
scissors cutting or chopping to shreds all the large influent solids material.

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Glossary 585
COMPOSITE (PROPORTIONAL) SAMPLE (com-POZ-it)	COMPOSITE (PROPORTIONAL) SAMPLE
A composite sample is a collection of individual samples obtained at regular intervals, usually every one or two hours during a
24-hour time span. Each individual sample is combined with the others in proportion to the flow when the sample was collected. The
resulting mixture (composite sample) forms a representative sample and is analyzed to determine the average conditions during the
sampling period.
COMPOUND	COMPOUND
A pure substance composed of two or more elements whose composition is constant. For example, table salt (sodium chloride - Na
CI) is a compound.
CONING (CONE-ing)	CONING
Development of a cone-shaped flow of liquid, like a whirlpool, through sludge. This can occur in a sludge hopper during sludge
withdrawal when the sludge becomes too thick. Part of the sludge remains in place while liquid rather than sludge flows out of the
hopper. Also called "coring."
CONTACT STABILIZATION	CONTACT STABILIZATION
Contact stabilization is a modification of the conventional activated sludge process. In contact stabilization, two aeration tanks are
used. One tank is for separate re-aeration of the return sludge for at least four hours before it is permitted to flow into the other
aeration tank to be mixed with the primary effluent requiring treatment.
CONTINUOUS PROCESS	CONTINUOUS PROCESS
A treatment process in which water is treated continuously in a tank or reactor. The water being treated continuously flows into the
tank at one end, is treated as it flows through the tank, and flows out the opposite end as treated water.
CONVENTIONAL TREATMENT	CONVENTIONAL TREATMENT
The pretreatment, sedimentation, flotation, trickling filter, activated sludge and chlorination wastewater treatment processes.
CROSS CONNECTION	CROSS CONNECTION
A connection between drinking (potable) water and an unsafe water supply. For example, if you have a pump moving nonpotable
water and hook into the drinking water system to supply water for the pump seal, a cross connection or mixing between the two
water systems can occur. This mixing may lead to contamination of the drinking water.
CRYOGENIC (cry-o-JEN-nick)	CRYOGENIC
Low temperature.
DO (DEE-OH)	DO
Abbreviation of Dissolved Oxygen. DO is the atmospheric oxygen dissolved in water or wastewater.
DATEOMETER (day-TOM-uh-ter)	DATEOMETER
A small calendar disc attached to motors and equipment to indicate the year in which the last maintenance service was performed.
DECHLORINATION (dee-KLOR-i-NAY-shun)	DECHLORINATION
The removal of chlorine from the effluent of a treatment plant.
DECIBEL	DECIBEL
A unit for expressing the relative intensity of sounds on a scale from zero for the average least perceptible sound to about 130 for the
average pain level.
DECOMPOSITION, DECAY	DECOMPOSITION, DECAY
Processes that convert unstable materials into more stable forms by chemical or biological action. Waste treatment encourages
decay in a controlled situation so that material may be disposed of in a stable form. When organic matter decays under anaerobic
conditions (putrefaction), undesirable odors are produced. The aerobic processes in common use for wastewater treatment produce
much less objectional odors.
DEGRADATION (de-grah-DAY-shun)	DEGRADATION
The conversion of a substance to simpler compounds.
DENITRIFICATION	DENITRIFICATION
A condition that occurs when nitrite or nitrate ions are reduced to nitrogen gas and bubbles are formed as a result of this process.
The bubbles attach to the biological floes and float the floes to the surface of the secondary clarifiers. This condition is often the
cause of rising sludge observed in secondary clarifiers or gravity thickeners.

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586 Treatment Plants
DENSITY (DEN-sit-tee)	DENSITY
A measure of how heavy a substance (solid, liquid or gas) is for its size. Density is expressed in terms of weight per unit volume, that
is, grams per cubic centimeter or pounds per cubic foot. The density of water (at 4"C or 39"F) is 1.0 gram per cubic centimeter or
about 62.4 pounds per cubic foot.
DESICCATOR (DESS-i-KAY-tor)	DESICCATOR
A closed container into which heated weighing or drying dishes are placed to cool in a dry environment. The dishes may be empty or
they may contain a sample. Desiccators contain a substance, such as anhydrous calcium chloride, which absorbs moisture and
keeps the relative humidity near zero so that the dish or sample will not gain weight from absorbed moisture.
DETENTION TIME	DETENTION TIME
The time required to fill a tank at a given flow or the theoretical time required for a given flow of wastewater to pass through a tank.
DETRITUS (dee-TRI-tus)	DETRITUS
The heavy, coarse mixture of grit and organic material carried by wastewater.
DEW POINT	DEW POINT
The temperature to which air with a given quantity of water vapor must be cooled to cause condensation of the vapor in the air.
DEWATER	DEWATER
To remove or separate a portion of the water present in a sludge or slurry.
DEWATERABLE	DEWATERABLE
This is a property of a sludge related to the ability to separate the liquid portion from the solid, with or without chemical conditioning.
A material is considered dewaterable if water will readily drain from it.
DIAPHRAGM PUMP	DIAPHRAGM PUMP
The pump in which a flexible diaphragm, generally of rubber or equally flexible material, is the operating part. It is fastened at the
edges in a vertical cylinder. When the diaphragm is raised suction is exerted, and when it is depressed, the liquid is forced through a
discharge valve.
DIFFUSED-AIR AERATION	DIFFUSED-AIR AERATION
A diffused air activated sludge plant takes air, compresses it, and then discharges the air below the water surface of the aerator
through some type of air diffusion device.
DIFFUSER	DIFFUSER
A device (porous plate, tube, bag) used to break the air stream from the blower system into fine bubbles in an aeration tank or
reactor.
DIGESTER (die-JEST-er)	DIGESTER
A tank in which sludge is placed to allow decomposition by microorganisms. Digestion may occur under anaerobic (more common)
or aerobic conditions.
DISCHARGE HEAD	DISCHARGE HEAD
The pressure (in feet (meters) or pounds per square inch (kilograms per square centimeter)) on the discharge side of a pump. The
pressure can be measured from the center line of the pump to the hydraulic grade line of the water in the discharge pipe.
DISINFECTION (dis-in-FECT-shun)	DISINFECTION
The process designed to kill most microorganisms in wastewater, including essentially all pathogenic (disease-causing) bacteria.
There are several ways to disinfect, with chlorine being most frequently used in water and wastewater treatment plants Compare
with STERILIZATION.
DISSOLVED OXYGEN	DISSOLVED OXYGEN
Molecular oxygen dissolved in water or wastewater, usually abbreviated DO.
DISTILLATE (DIS-tuh-late)	DISTILLATE
In the distillation of a sample, a portion is evaporated; the part that is condensed afterwards is the distillate.
DISTRIBUTOR	DISTRIBUTOR
The rotating mechanism that distributes the wastewater evenly over the surface of a trickling filter or other process unit. Also see
FIXED SPRAY NOZZLE.

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Glossary 587
DOCTOR BLADE	DOCTOR BLADE
A blade used to remove any excess solids that may cling to the outside of a rotating screen.
DROOP	DROOP
The difference between the actual value and the desired value (or set point) characteristics of proportional controllers that do not
incorporate reset action. Also called OFFSET.
DYNAMIC HEAD	DYNAMIC HEAD
When a pump is operating, the vertical distance (in feet or meters) from a point to the energy grade lines. Also see TOTAL
DYNAMIC HEAD and STATIC HEAD.
EDUCTOR (e-DUCK-tor)	EDUCTOR
A hydraulic device used to create a negative pressure (suction) by forcing a liquid through a restriction, such as a Venturi. An
eductor or aspirator (the hydraulic device) may be used in the laboratory in place of a vacuum pump; sometimes usqd instead of a
suction pump.
EFFLORESCENCE (EF-low-RESS-ense)	EFFLORESCENCE
The powder or crust formed on a substance when moisture is given off upon exposure to the atmosphere.
EFFLUENT (EF-lu-ent)	EFFLUENT
Wastewater or other liquid — raw, partially or completely treated — flowing FROM a basin, treatment process, or treatment plant.
ELECTRO-CHEMICAL PROCESS	ELECTRO-CHEMICAL PROCESS
A process that causes the deposition or formation of a seal or coating of a chemical element or compound by the use of electricity.
ELECTRO-MAGNETIC FORCES	ELECTRO-MAGNETIC FORCES
Forces resulting from electrical charges that either attract or repel particles. Particles with opposite charges are attracted to each
other. For example, a particle with positive charges is attracted to a particle with negative charges. Particles with similar charges
repel each other. A particle with positive charges is repelled by a particle with positive charges and a particle with negative charges
is repelled by another particle with negative charges.
ELECTROLYSIS (ELECT-TROLLEY-sis)	ELECTROLYSIS
The decomposition of material by an electric current.
ELECTROLYTE (ELECT-tro-LIGHT)	ELECTROLYTE
A substance which dissociates (separates) into two or more ions when it is dissolved in water.
ELECTROLYTIC PROCESS (ELECT-tro-LIT-ick)	ELECTROLYTIC PROCESS
A process that causes the decomposition of a chemical compound by the use of electricity.
ELECTRON	ELECTRON
An extremely small (microscopic), negatively charged particle. An electron is much too small to be seen with a microscope.
ELEMENT	ELEMENT
A substance which cannot be separated into substances of other kinds by ordinary chemical means. For example, sodium (Na) is an
element.
ELUTRIATION (e-LOO-tree-A-shun)	ELUTRIATION
The washing of digested sludge in plant effluent. The objective is to remove (wash out) fine particulates and/or alkalinity in sludge.
This process reduces the demand for conditioning chemicals and improves settling or filtering characteristics of the solids.
EMULSION (e-MULL-shun)	EMULSION
A liquid mixture of two or more liquid substances not normally dissolved in one another, but one liquid held in suspension in the
other.
END POINT	END POINT
Samples are titrated to the end point. This means that a chemical is added, drop by drop, to a sample until a certain color change
(blue to clear, for example) occurs which is called the END POINT of the titration. In addition to a color change, an end point may be
reached by the formation of a precipitate or the reaching of a specified pH. An end point may be detected by the use of an electronic
device such as a pH meter.


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588 Treatment Plants
ENDOGENOUS (en-DODGE-en-us)	ENDOGENOUS
A reduced level of respiration (breathing) in which organisms break down compounds within their own cells to produce the oxygen
they need.
ENERGY GRADE LINE (EGL)	ENERGY GRADE LINE (EGL)
A line that represents the elevation of energy head (in feet) of water flowing in a pipe, conduit or channel. The line is drawn above the
hydraulic grade line a distance equal to the velocity head of the water flowing at each section or point along the pipe or channel.
ENTERIC	ENTERIC
Intestinal.
ENZYMES (EN-zimes)	ENZYMES
Enzymes are organic substances which are produced by living organisms and speed up chemical changes.
EQUALIZING BASIN	EQUALIZING BASIN
A holding basin in which variations in flow and composition of liquid are averaged. Such basins are used to provide a flow of
reasonably uniform volume and composition to a treatment unit. Also called a balancing reservoir.
ESTUARIES (ES-chew-wear-eez)	ESTUARIES
Bodies of water which are located at the lower end of a river and are subject to tidal fluctuations.
EVAPOTRANSPIRATION (e-VAP-o-trans-spi-RAY-shun)	EVAPOTRANSPIRATION
The total water removed from an area by transpiration (plants) and by evaporation from soil, snow and water surfaces.
EXPLOSIMETER	EXPLOSIMETER
An instrument used to detect explosive atmospheres. When the Lower Explosive Limit (L.E.L.) of an atmosphere is exceeded, an
alarm signal on the instrument is activated.
F/M RATIO	F/M RATIO
Food to microorganism ratio. A measure of food provided to bacteria in an aeration tank.
	Food 		 BOD, lbs/day
Microorganisms MLVSS, lbs
= Flow, MGD x BOD, mgJL x 8.34 lbs/gal
Volume, MG x MLVSS, mgIL x 8.34 lbs/gal
: BOD, kg/day
or
MLVSS, kg
FACULTATIVE (FACK-ul-TAY-tive)	FACULTATIVE
Facultative bacteria can use either molecular (dissolved) oxygen or oxygen obtained from food materials such as sulfate or nitrate
ions. In other words, facultative bacteria can live under aerobic or anaerobic conditions.
FACULTATIVE POND (FACK-ul-TAY-tive)	FACULTATIVE POND
The most common type of pond in current use. The upper portion (supernatant) is aerobic, while the bottom layer is anaerobic
Algae supply most of the oxygen to the supernatant.
FILAMENTOUS BACTERIA (FILL-a-MEN-tuss)	FILAMENTOUS BACTERIA
Organisms that grow in a thread or filamentous form. Common types are thiothrix and actinomyces.
FILTER AID	FILTER AID
A chemical (usually a polymer) added to water to help remove fine colloidal suspended solids.
FIXED	FIXED
A sample is "fixed" in the field by adding chemicals that prevent the water quality indicators of interest in the sample from changing
before final measurements are performed later in the lab.
FIXED SPRAY NOZZLE	FIXED SPRAY NOZZLE
Cone-shaped spray nozzle used to distribute wastewater over the filter media, similar to a lawn sprinkling system. A deflector or
steel ball is mounted within the cone to spread the flow of wastewater through the cone, thus causing a spraying action. Also see
DISTRIBUTOR.

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Glossary 589
FLAME POLISHED	FLAME POLISHED
Melted by a flame to smooth out irregularities. Sharp or broken edges of glass (such as the end of a glass tube) are rotated in a
flame until the edge melts slightly and becomes smooth.
FLIGHTS	FLIGHTS
Scraper boards, made from redwood or other rot-resistant woods or plastic, used to collect and move settled sludge or floating
scum.
FLOC	FLOC
Groups or clumps of bacteria and particles that have come together and formed a cluster. Found in aeration tanks and secondary
clarifiers.
FLOCCULATION (FLOCK-you-LAY-shun)	FLOCCULATION
The gathering together of fine particles to form larger particles.
FLOW-EQUALIZATION SYSTEM	FLOW-EQUALIZATION SYSTEM
A device or tank designed to hold back or store a portion of peak flows for release during low-flow periods.
FOOD/MICROORGANISM RATIO	FOOD/MICROORGANISM RATIO
Food to microorganism ratio. A measure of food provided to bacteria in an aeration tank.
	Food 	= BOD, lbs/day
Microorganisms MLVSS, lbs
Flow, MGD x BOD, mgIL x 8.34 lbs/gal
or
Volume, MG x MLVSS, mgIL x 8.34 lbs/gal
BOD, kg/day
MLVSS, kg
Commonly abbreviated F/M Ratio.
FORCE MAIN	FORCE MAIN
A pipe that conveys wastewater under pressure from the discharge side of a pump to a point of gravity flow.
FREE AVAILABLE CHLORINE	FREE AVAILABLE CHLORINE
The amount of chlorine available in water. This chlorine may be in the form of dissolved gas (Cl2), hypochlorous acid (HOCI), or
hypochlorite ion (OCI~), but does not include chlorine combined with an amine (ammonia or nitrogen) or other organic compound.
FREE AVAILABLE RESIDUAL CHLORINE	FREE AVAILABLE RESIDUAL CHLORINE
That portion of the total residual chlorine remaining in water or wastewater at the end of a specified contact period. Residual chlorine
will react chemically and biologically as hypochlorous acid (HOCI) or hypochlorite ion (OCh).
FREE CHLORINE	FREE CHLORINE
Free chlorine is chlorine (Cl2) in a liquid or gaseous form. Free chlorine combines with water to form hypochlorous (HOCI) and
hydrochloric (HCI) acids. In wastewater free chlorine usually combines with an amine (ammonia or nitrogen) or other organic
compounds to form combined chlorine compounds.
FREE OXYGEN	FREE OXYGEN
Molecular oxygen available for respiration by organisms. Molecular oxygen is the oxygen molecule, 02, that is not combined with
another element to form a compound.
FREE RESIDUAL CHLORINATION	FREE RESIDUAL CHLORINATION
The application of chlorine or chlorine compounds to water or wastewater to produce a free available chlorine residual directly or
through the destruction of ammonia (NH3) or certain organic nitrogenous compounds.
FREEBOARD	FREEBOARD
The vertical distance from the normal water surface to the top of the confining wall. -j	FREEBOARD
L*	v
/ 1
WATER DEPTH
FRICTION LOSS	FRICTION LOSS
The head lost by water flowing in a stream or conduit as the result of the disturbances set up by the contact between the moving
water and its containing conduit and by intermolecular friction.

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590 Treatment Plants
GASIFICATION (GAS-i-fi-KAY-shun)	GASIFICATION
The conversion of soluble and suspended organic materials into gas during anaerobic decomposition. In clarifiers the resulting gas
bubbles can become attached to the settled sludge and cause large clumps of sludge to rise and float on the water surface. In
anaerobic sludge digesters, this gas is collected for fuel or disposed of using the waste gas burner.
GRAB SAMPLE
A single sample of wastewater taken at neither a set time nor flow.
GRAB SAMPLE
GRAVIMETRIC	GRAVIMETRIC
A means of measuring unknown concentrations of water quality indicators in a sample by WEIGHING a precipitate or residue of the
sample.
GRIT	GRIT
The heavy mineral material present in wastewater, such as sand, eggshells, gravel, and cinders.
GRIT REMOVAL	GRIT REMOVAL
Grit removal is accomplished by providing an enlarged channel or chamber which causes the flow velocity to be reduced and allows
the heavier grit to settle to the bottom of the channel where it can be removed.
GROWTH RATE	GROWTH RATE
An experimentally determined constant to estimate the unit growth rate of bacteria while degrading organic wastes.
HEAD	HEAD
A term used to describe the height or energy of water above a point. A head of water may be measured in either height (feet or
meters) or pressure (pounds per square inch or kilograms per square centimeter). Also see DISCHARGE HEAD, DYNAMIC HEAD
STATIC HEAD, SUCTION HEAD, SUCTION LIFT and VELOCITY HEAD.
J
!_L
VKJ
HEAD LOSS
HEAD LOSS
L
HEADER
HEAD LOSS
An indirect measure of loss of energy or pressure. Flowing water will lose some of
its energy when it passes through a pipe, bar screen, comminutor, filter or other
obstruction. The amount of energy or pressure lost is called "head loss." Head loss
is measured as the difference in elevation between the upstream water surface
and the downstream water surface and may be expressed in feet or meters.
HEADER
A large pipe to which the ends of a series of smaller pipes are connected. Also called a "manifold."
HEADWORKS	HEADWORKS
The facilities where wastewater enters a wastewater treatment plant. The headworks may consist of bar screens, comminutors, a
wet well and pumps.
HEPATITIS	HEPATITIS
Hepatitis is an acute viral infection of the liver. Yellow jaundice is one symptom of hepatitis.
HUMUS SLUDGE	HUMUS SLUDGE
The sloughed particles of biomass from trickling filter media that are removed from the water being treated in secondary clarifiers.
HYDRAULIC GRADE LINE (HGL)	HYDRAULIC GRADE LINE (HGL)
The surface or profile of water flowing in an open channel or a pipe flowing partially full. If a pipe is under pressure, the hydraulic
grade line is at the level water would rise to in a small tube connected to the pipe. To reduce the release of odors from wastewater,
the water surface should be kept as smooth as possible.
HYDRAULIC LOADING	HYDRAULIC LOADING
Hydraulic loading refers to the flows (MGD or cu m/day) to a treatment plant or treatment process. Detention times, surface loadings
and weir overflow rates are directly influenced by flows.
HYDROGEN ION CONCENTRATION (H+)	HYDROGEN ION CONCENTRATION (H+)
The weight of hydrogen ion in moles per liter of solution. Commonly expressed as the pH value, which is the logarithm of the
reciprocal of the hydrogen-ion concentration.
1
PH
log
(H+)

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Glossary 591
HYDROGEN SULFIDE (H2S)	HYDROGEN SULFIDE (H2S)
Hydrogen sulfide is a gas with a rotten egg odor. This gas is produced under anaerobic conditions. Hydrogen sulfide is particularly
dangerous because it dulls your sense of smell so that you don't notice it after you have been around it for a while and because the
odor is not noticeable in high concentrations. The gas is very poisonous to your respiratory system, explosive, flammable and
colorless.
HYDROLOGIC CYCLE (Hl-dro-loj-ic)	HYDROLOGIC CYCLE
The process of evaporation of water into the air and its return to earth by precipitation (rain or snow). This process also includes
transpiration from plants, groundwater movement and runoff into rivers, streams and the ocean.
HYDROLYSIS (hi-DROL-e-sis)	HYDROLYSIS
The addition of water to the molecule to break down complex substances into simpler ones.
HYDROSTATIC SYSTEM	HYDROSTATIC SYSTEM
In a hydrostatic sludge removal system, the surface of the water in the clarifier is higher than the surface of the water in the sludge
well or hopper. This difference in pressure head forces sludge from the bottom of the clarifier to flow through pipes to the sludge well
or hopper.
HYGROSCOPIC (Hl-grow-SKOP-ic)	HYGROSCOPIC
A substance that absorbs or attracts moisture from the air.
HYPOCHLORINATION (hi-po-KLOR-i-NAY-shun)	HYPOCHLORINATION
The application of hypochlorite compounds to water or wastewater for the purpose of disinfection.
HYPOCHLORINATORS (hi-poe-KLOR-i-NAY-tors)	HYPOCHLORINATORS
Chlorine pumps or devices used to feed chlorine solutions made from hypochlorites such as bleach (sodium hypochlorite) or
calcium hypochlorite.
HYPOCHLORITE (hi-po-KLOR-ite)	HYPOCHLORITE
Hypochlorite compounds contain chlorine and are used for disinfection. They are available as liquids or solids (powder, granules,
and pellets) in barrels, drums, and cans.
IMHOFF CONE	i	i IMHOFF CONE
A clear, cone-shaped container marked with graduations. The cone is used to
measure the volume of settleable solids in a specific volume of wastewater.
IMPELLER	'	IMPELLER
A rotating set of vanes designed to impel rotation of a mass of fluid.
IMPELLER PUMP	IMPELLER PUMP
Any pump in which the water is moved by the continuous application of power from some mechanical source.
INCINERATION	INCINERATION
The conversion of dewatered sludge cake by combustion (burning) to ash, carbon dioxide and water vapor.
INDICATOR (CHEMICAL)	INDICATOR (CHEMICAL)
A substance that gives a visible change, usually of color, at a desired point in a chemical reaction, generally at a specified end point.
INDOLE (IN-dole)	INDOLE
An organic compound (C8H7N) containing nitrogen which has an ammonia odor.
INFILTRATION (IN-fill-TRAY-shun)	INFILTRATION
The seepage of groundwater into a sewer system, including service connections. Seepage frequently occurs through defective or
cracked pipes, pipe joints, connections or manhole walls.
INFLOW	INFLOW
Water discharged into the sewer system from sources other than regular connections. This includes flow from yard drains,
foundation drains and around manhole covers. Inflow differs from infiltration in that it is a direct discharge into the sewer rather than
a leak in the sewer itself.
INFLUENT (IN-flu-ent)	INFLUENT
Wastewater or other liquid — raw or partially treated — flowing INTO a reservoir, basin, treatment process, or treatment plant.

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592 Treatment Plants
INHIBITORY SUBSTANCES	INHIBITORY SUBSTANCES
Materials that kill or restrict the ability of organisms to treat wastes.
INOCULATE (in-NOCK-you-late)	INOCULATE
To introduce a seed culture into a system.
INORGANIC WASTE	INORGANIC WASTE
Waste material such as sand, salt, iron, calcium, and other mineral materials which are only slightly affected by the action of
organisms. Inorganic wastes are chemical substances of mineral origin; whereas organic wastes are chemical substances usually
of animal or vegetable origin. Also see NONVOLATILE MATTER.
INTERFACE	INTERFACE
The common boundary layer between two fluids such as a gas (air) and a liquid (water) or a liquid (water) and another liquid (oil).
IONIC CONCENTRATION	IONIC CONCENTRATION
The concentration of any ion in solution, generally expressed in moles per liter.
IONIZATION	IONIZATION
The process of adding electrons to, or removing electrons from, atoms or molecules, thereby creating ions. High temperatures,
electrical discharges, and nuclear radiation can cause ionization.
JAR TEST	JAR TEST
A laboratory procedure that simulates coagulation/flocculation with differing chemical doses. The purpose of the procedure is to
ESTIMATE the minimum coagulant dose required to achieve certain water quality goals. Samples of water to be treated are placed
in six jars. Various amounts of chemicals are added to each jar, stirred and the settling of solids is observed. The lowest dose of
chemicals that provides satisfactory settling is the dose used to treat the water.
JOULE (jewel)	JOULE
A measure of energy, work or quantity of heat. One joule is the work done when the point of application of a force of one newton is
displaced a distance of one meter in the direction of the force.
KJELDAHL NITROGEN (KELL-doll)	KJELDAHL NITROGEN
Organic and ammonia nitrogen.
LAUNDERS (LAWN-ders)	LAUNDERS
Sedimentation tank effluent troughs.
LIMIT SWITCH	LIMIT SWITCH
A device that regulates or controls the travel distance of a chain or cable.
LINEAL (LIN-e-al)	LINEAL
The length in one direction of a line. For example, a board 12 feet long has 12 lineal feet in its length.
LIQUEFACTION (LICK-we-FACK-shun)	LIQUEFACTION
The conversion of large solid particles of sludge into very fine particles which either dissolve or remain suspended in wastewater.
LOADING	LOADING
Quantity of material applied to a device at one time.
M or MOLAR	M or MOLAR
A molar solution consists of one gram molecular weight of a compound dissolved in enough water to make one liter of solution. A
gram molecular weight is the molecular weight of a compound in grams. For example, the molecular weight of sulfuric acid (H,SO„)
is 98. A 1M solution of sulfuric acid would consist of 98 grams of H2S04 dissolved in enough distilled water to make one liter of
solution.
MBAS	MBAS
Methylene Blue Active Substance. Another name for surfactants, or surface active agents, is methylene blue active substances.
The determination of surfactants is accomplished by measuring the color change in a standard solution of methylene blue dye.
MPN (EM-PEA-EN)	MPN
MPN is the Most Probable Number of coliform-group organisms per unit volume. Expressed as a density or population of organisms
per 100 ml.

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Glossary 593
MANIFOLD
A large pipe to which the ends of a series of smaller pipes are connected. Also called a "header."
MANIFOLD
MANOMETER
MANOMETER (man-NAH-met-ter)
An instrument for measuring pressure. Usually a glass tube filled with a liquid and used to measure the difference in pressure across
a flow-measuring device such as an orifice or Venturi meter. The instrument used to measure blood pressure is a type of
manometer.
VENTURI METER
£
MANOMETER
MASKING AGENTS
MASKING AGENTS
Substances used to cover up or disguise unpleasant odors. Liquid masking agents are dripped into the wastewater, sprayed into the
air, or evaporated (using heat) with the unpleasant fumes or odors and then discharged into the air by blowers to make an
undesirable odor less noticeable.
MEAN CELL RESIDENCE TIME (MCRT)	MEAN CELL RESIDENCE TIME (MCRT)
An expression of the average time that a microorganism will spend in the activated sludge process.
MCRT days = Solids in Activated Sludge Process, lbs
Solids Removed from Process, lbs/day
MECHANICAL AERATION	MECHANICAL AERATION
The use of machinery to mix air and water so that oxygen can be absorbed into the water. Some examples are: paddle wheels,
mixers, or rotating brushes to agitate the surface of an aeration tank; pumps to create fountains; and pumps to discharge water
down a series of steps forming falls or cascades.
MEDIA	MEDIA
The material in a trickling filter on which slime organisms grow. As settled wastewater trickles over the media, slime organisms
remove certain types of wastes thereby partially treating the wastewater. Also the material in a rotating biological contactor or in a
gravity or pressure filter.
MEDIAN	MEDIAN
The middle measurement or value. When several measurements are ranked by magnitude (largest to smallest), half of the
measurements will be larger and half will be smaller.
MENISCUS (meh-NIS-cuss)	MENISCUS
The curved top of a column of liquid (water, oil, mercury) in a small tube. When the liquid wets the sides of the container (as with
water), the curve forms a valley. When the confining sides are not wetted (as with mercury), the curve forms a hill or upward bulge.
WATER
MERCURY
(READ
BOTTOM)
,i'W:
V*
(READ
TOP)
MERCAPTANS (mer-CAP-tans)
Compounds containing sulfur which have an extremely offensive skunk odor.
MESOPHILIC BACTERIA (mess-O-FILL-lick)
MERCAPTANS
MESOPHILIC BACTERIA
Medium temperature bacteria. A group of bacteria that grow and thrive in a moderate temperature range between 68°F (20°C) and
113°F (45°C). The optimum temperature range for these bacteria in anaerobic digestion is 85°F (30°C) to 100°F (38°C).

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594 Treatment Plants
MICRON (MY-kron)	MICRON
A unit of length. One millionth of a meter or one thousandth of a millimeter. One micron equals 0.00004 of an inch.
MICROORGANISMS (micro-ORGAN-is-sums)	MICROORGANISMS
Very small organisms that can be seen only through a microscope. Some microorganisms use the wastes in wastewater for food
and thus remove or alter much of the undesirable matter.
MICROSCREEN	MICROSCREEN
A device with a fabric straining media with openings usually between 20 and 60 microns. The fabric is wrapped around the outside of
a rotating drum. Wastewater enters the open end of the drum and flows out through the rotating screen cloth. At the highest point of
the drum the collected solids are backwashed by high-pressure water jets into a trough located within the drum.
MILLIGRAMS PER LITER, mgIL (MILL-i-GRAMS per LEET-er)	MILLIGRAMS PER LITER, mg/L
A measure of the concentration by weight of a substance per unit volume. For practical purposes, one mg/L is equal to one part per
million parts (ppm). Thus a liter of water with a specific gravity of 1.0 weighs one million milligrams; and if it contains 10
milligrams of dissolved oxygen, the concentration is 10 milligrams per million milligrams, or 10 milligrams per liter (10 mg/L), or 10
parts of oxygen per million parts of water, or 10 parts per million (10 ppm).
MILLIMICRON (MILL-e-MY-cron)	MILLIMICRON
One thousandth of a micron or a millionth of a millimeter.
MIXED LIQUOR	MIXED LIQUOR
When the activated sludge in an aeration tank is mixed with primary effluent or the raw wastewater and return sludge, this mixture is
then referred to as mixed liquor as long as it is in the aeration tank. Mixed liquor also may refer to the contents of mixed aerobic or
anaerobic digesters.
MIXED LIQUOR SUSPENDED SOLIDS (MLSS)	MIXED LIQUOR SUSPENDED SOLIDS(MLSS)
Suspended solids in the mixed liquor of an aeration tank.
MIXED LIQUOR VOLATILE SUSPENDED	MIXED LIQUOR VOLATILE SUSPENDED
SOLIDS iMLVSS)	SOLIDS (MLVSS)
The organic or volatile suspended solids in the mixed liquor of an aeration tank.
MOLECULAR OXYGEN	MOLECULAR OXYGEN
The oxygen molecule, Oz, that is not combined with another element to form a compound.
MOLECULAR WEIGHT	MOLECULAR WEIGHT
The molecular weight of a compound in grams is the sum of the atomic weights of the elements in the compound. The molecular
weight of sulfuric acid (H2S04) in grams is 98.
Atomic	Number	Molecular
Element Weight	of Atoms	Weight
H 1	2	2
S 32	1	32
0 16	4	64
98
MOLECULE (MOLL-uh-kule)	MOLECULE
A molecule is the smallest portion of an element or compound that still retains or exhibits all the properties of the substance.
MOTILE (MO-till)	MOTILE
Motile organisms exhibit or are capable of movement.
MOVING AVERAGE	MOVING AVERAGE
To calculate the moving average for the last 7 days, add up the values for the last 7 days and divide by 7. Each day add the most
recent day to the sum of values and subtract the oldest value. By using the 7-day moving average, each day of the week is always
represented in the calculations.
MUFFLE FURNACE	MUFFLE FURNACE
A small oven capable of reaching temperatures up to 600°C. Muffle furnaces are used in laboratories for burning or incinerating
samples to determine the amounts of volatile solids and/or fixed solids in samples of wastewater.
MULTI-STAGE PUMP	MULTI-STAGE PUMP
A pump that has more than one impeller. A single-stage pump has one impeller.

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Glossary 595
N or NORMAL	N or NORMAL
A normal solution contains one gram equivalent weight of a reactant (compound) per liter of solution. The equivalent weight of an
acid is that weight which contains one gram atom of ionizable hydrogen or its chemical equivalent. For example, the equivalent
weight of sulfuric acid (H2S04) is 49 (98 divided by 2 because there are two replaceable hydrogen ions). A 1 N solution of sulfuric
acid would consist of 49 grams of H2S04 dissolved in enough water to make one liter of solution.
NPDES PERMIT	NPDES PERMIT
National Pollutant Discharge Elimination System permit is the regulatory agency document designed to control all discharges of
pollutants from point sources into U.S. waterways. NPDES permits regulate discharges into navigable waters from all point sources
of pollution, including industries, municipal treatment plants, large agricultural feed lots and return irrigation flows.
NEUTRALIZATION (new-trall-i-ZAY-shun)	NEUTRALIZATION
Addition of an acid or alkali (base) to a liquid to cause the pH of the liquid to move towards a neutral pH of 7.0.
NITRIFICATION (NYE-tri-fi-KAY-shun)	NITRIFICATION
A process in which bacteria change the ammonia and organic nitrogen in wastewater into oxidized nitrogen (usually nitrate). The
second-stage BOD is sometimes referred to as the "nitrification stage" (first-stage BOD is called the "carbonaceous stage").
NITRIFYING BACTERIA	NITRIFYING BACTERIA
Bacteria that change the ammonia and organic nitrogen in wastewater into oxidized nitrogen (usually nitrate).
NITROGENOUS (nye-TROG-en-ous)	NITROGENOUS
Nitrogenous compounds contain nitrogen.
NOMOGRAM	NOMOGRAM
A chart or diagram containing three or more scales used to solve problems with three or more variables instead of using mathemati-
cal formulas.
NONCORRODIBLE	NONCORRODIBLE
A material that resists corrosion and will not be eaten away by wastewater or chemicals in wastewater.
NONSPARKING TOOLS	NONSPARKING TOOLS
These tools will not produce a spark during use.
NONVOLATILE MATTER	NONVOLATILE MATTER
Material such as sand, salt, iron, calcium, and other mineral materials which are only slightly affected by the action of organisms.
Volatile materials are chemical substances usually of animal or vegetable origin. Also see INORGANIC WASTE.
NUTRIENT CYCLE	NUTRIENT CYCLE
The transformation or change of a nutrient from one form to another until the nutrient has returned to the original form, thus
completing the cycle. The cycle may take place under either aerobic or anaerobic conditions.
NUTRIENTS	NUTRIENTS
Substances which are required to support living plants and organisms. Major nutrients are carbon, hydrogen, oxygen, sulfur,
nitrogen and phosphorus. Nitrogen and phosphorus are difficult to remove from wastewater by conventional treatment processes
because they are water soluble and tend to recycle. Also see NUTRIENT CYCLE.
O & M MANUAL (Operation and Maintenance Manual)	O & M MANUAL
A manual which outlines procedures for operators to follow to operate and maintain a specific wastewater treatment plant and the
equipment in the plant.
OSHA	OSHA
The Williams-Steiger Occupational Safety and Health Act of 1980 (OSHA) is a law designed to protect the health and safety of
industrial workers and treatment plant operators. It regulates the design, construction, operation and maintenance of industrial
plants and wastewater treatment plants. The Act does not apply directly to municipalities at present (1980), EXCEPT in those states
that have approved plans and have asserted jurisdiction under Section 18 of the OSHA Act. However, wastewater treatment plants
have come under stricter regulation in all phases of activity as a result of OSHA standards.
OBLIGATE AEROBES	OBLIGATE AEROBES
Bacteria that must have molecular (dissolved) oxygen (DO) to reproduce.
ODOR PANEL	ODOR PANEL
A group of people used to measure odors.

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596 Treatment Plants
OFFSET	OFFSET
The difference between the actual value and the desired value (or set point) characteristic of proportional controllers that do not
incorporate reset action. Also called DROOP.
OLFACTOMETER (ol-FACT-tom-meter)	OLFACTOMETER
A device used to measure odors in the field by diluting odors with odor-free air.
ORGANIC WASTE	ORGANIC WASTE
Waste material which comes mainly from animal or vegetable sources. Organic waste generally can be consumed by bacteria and
other small organisms. Inorganic wastes are chemical substances of mineral origin.
ORGANISM	ORGANISM
Any form of animal or plant life. Also see BACTERIA.
ORIFICE (OR-uh-fiss)	ORIFICE
An opening in a plate, wall or partition. In a trickling filter distributor, the wastewater passes through an orifice to the surface of the
filter media. An orifice flange set in a pipe consists of a slot or hole smaller than the pipe diameter. The difference in pressure in the
pipe above and below the orifice may be related to flow in the pipe.
ORTHOTOLIDINE (or-tho-TOL-i-dine)	ORTHOTOLIDINE
Orthotolidine is a colorimetric indicator of chlorine residual. If chlorine is present, a yellow-colored compound is produced. This
method is no longer approved for tests of effluent chlorine residual.
OVERFLOW RATE	OVERFLOW RATE
One of the guidelines for the design of settling tanks and clarifiers in treatment plants.
Overflow Rate, gpd/sq ft = Flow, gallons/day
Surface Area, sq ft
OXIDATION (ox-i-DAY-shun)	OXIDATION
Oxidation is the addition of oxygen, removal of hydrogen, or the removal of electrons from an element or compound. In wastewater
treatment, organic matter is oxidized to more stable substances. The opposite of REDUCTION.
OXIDATION-REDUCTION POTENTIAL	OXIDATION-REDUCTION POTENTIAL
The electrical potential required to transfer electrons from one compound or element (the oxidant) to another compound or element
(the reductant) and used as a qualitative measure of the state of oxidation in wastewater treatment systems.
OXIDIZED ORGANICS	OXIDIZED ORGANICS
Organic materials that have been broken down in a biological process. Examples of these materials are carbohydrates and proteins
that are broken down to simple sugars.
OXIDIZING AGENT	OXIDIZING AGENT
An oxidizing agent is any substance, such as oxygen (02) and chlorine (Cl2), that can add (take on) electrons. When oxygen or
chlorine is added to wastewater, organic substances are oxidized. These oxidized organic substances are more stable and less
likely to give off odors or to contain disease bacteria. The opposite of REDUCING AGENT.
OZONIZATION (O-zoe-nie-ZAY-shun)	OZONIZATION
The application of ozone to water, wastewater, or air, generally for the purposes of disinfection or odor control.
PACKAGE TREATMENT PLANT	PACKAGE TREATMENT PLANT
A small wastewater treatment plant often fabricated at the manufacturer's factory, hauled to the site, and installed as one facility.
The package may be either a small primary or a secondary wastewater treatment plant.
PARALLEL OPERATION	PARALLEL OPERATION
When wastewater being treated is split and a portion flows to one treatment unit while the remainder flows to another similar
treatment unit. Also see SERIES OPERATION.
PARASITIC BACTERIA (PAIR-a-SIT-tick)	PARASITIC BACTERIA
Parasitic bacteria are those bacteria which normally live off another living organism, known as the "host."

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Glossary 597
PATHOGENIC BACTERIA (path-o-JEN-nick)	PATHOGENIC BACTERIA
Bacteria, viruses or cysts which can cause disease (typhoid, cholera, dysentery). There are many types of bacteria which do NOT
cause disease and which are NOT called pathogenic. Many beneficial bacteria are found in wastewater treatment processes
actively cleaning up organic wastes.
PERCENT SATURATION	PERCENT SATURATION
The amount of a substance that is dissolved in a solution compared with the amount that could be dissolved in the solution,
expressed as a percent.
Amount of Sub. that is Dissolved x 100%
Percent Saturation, %
Amount that Could be Dissolved in Solution
PERCOLATION (PURR-ko-LAY-shun)	PERCOLATION
The movement or flow of water through soil or rocks.
PERISTALTIC PUMP (peri-STALL-tick)	PERISTALTIC PUMP
A type of positive displacement pump.
pH (PEA-A-ch)	pH
pH is an expression of the intensity of the alkaline or acid condition of a liquid. Mathematically, pH is the logarithm (base 10) of the
reciprocal of the hydrogen ion concentration.
pH = Log 1
(H+)
The pH may range from 0 to 14, where 0 is most acid, 14 most alkaline, and 7 is neutral. Natural waters usually have a pH between
6.5 and 8.5.
PHENOL (FEE-noll)	PHENOL
An organic compound that is a derivative of benzene.
PHENOLPHTHALEIN ALKALINITY	PHENOLPHTHALEIN ALKALINITY
A measure of the hydroxide ions plus one half of the normal carbonate ions in aqueous suspension. Measured by the amount of
sulfuric acid required to bring the water to a pH value of 8.3, as indicated by a change in color of phenolphthalein. It is expressed in
milligrams per liter of calcium carbonate.
PHOTOSYNTHESIS (foto-SIN-the-sis)	PHOTOSYNTHESIS
A process in which organisms with the aid of chlorophyll (green plant enzyme) convert carbon dioxide and inorganic substances to
oxygen and additional plant material, utilizing sunlight for energy. All green plants grow by this process.
PHYSICAL WASTE TREATMENT PROCESS	PHYSICAL WASTE TREATMENT PROCESS
Physical waste treatment processes include use of racks, screens, comminutors, and clarifiers (sedimentation and flotation).
Chemical or biological reactions are not an important part of a physical treatment process.
PLUG FLOW	PLUG FLOW
A type of flow that occurs in tanks, basins or reactors when a slug of wastewater moves through a tank without ever dispersing or
mixing with the rest of the wastewater flowing through the tank.
DIRECTION
OF FLOW
PLUG FLOW
POLLUTION	POLLUTION
Any change in the natural state of water which interferes with its beneficial reuse or causes failure to meet water-quality require-
ments.
POLYELECTROLYTE (POLY-electro-light)	POLYELECTROLYTE
A high-molecular-weight substance that is formed by either a natural or synthetic process. Natural polyelectrolytes may be of
biological origin or derived from starch products, cellulose derivatives, and alignates. Synthetic polyelectrolytes consist of simple
substances that have been made into complex, high-molecular-weight substances. Often called a "polymer."

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598 Treatment Plants
POLYMER (POLY-mer)	POLYMER
A high-molecular-weight substance that is formed by either a natural or synthetic process. Natural polymers may be of biological
origin or derived from starch products, cellulose derivatives, and alignates. Synthetic polymers consist of simple substances that
have been made into complex, high-molecular-weight substances. Often called a "polyelectrolyte."
POLYSACCHARIDE (polly-SAC-a-ride)	POLYSACCHARIDE
A carbohydrate such as starch, insulin or cellulose.
PONDING	PONDING
A condition occurring on trickling filters when the hollow spaces (voids) become plugged to the extent that water passage through
the filter is inadequate. Ponding may be the result of excessive slime growths, trash, or media breakdown.
POPULATION EQUIVALENT	POPULATION EQUIVALENT
A means of expressing the strength of organic material in wastewater. In a domestic wastewater system, microorganisms use up
about 0.2 pounds of oxygen per day for each person using the system (as measured by the standard BOD test).
Pop Equiv = 'r|ow' x BOD, mgJL x 8.34 lbs/gal
persons	0.2 lbs BOD/day/person
POSTCHLORINATION	POSTCHLORINATION
The addition of chlorine to the plant discharge or effluent, FOLLOWING plant treatment, for disinfection purposes.
POTABLE WATER (POE-ta-bl)	POTABLE WATER
Water that does not contain objectionable pollution, contamination, minerals, or infective agents and is considered safe for domestic
consumption.
PRE-AERATION	PRE-AERATION
The addition of air at the initial stages of treatment to freshen the wastewater, remove gases, add oxygen, promote flotation of
grease, and aid coagulation.
PRECHLORINATION	PRECHLORINATION
The addition of chlorine at the headworks of the plant PRIOR TO other treatment processes mainly for odor and corrosion control.
Also applied to aid disinfection, to reduce plant BOD load, to aid in settling, to control foaming in Imhoff units and to help remove oil.
PRECIPITATE (pre-SIP-i-TATE)	PRECIPITATE
To separate (a substance) out in solid form from a solution, as by the use of a reagent. The substance precipitated.
PRECOAT	PRECOAT
Application of a free-draining, non-cohesive material such as diatomaceous earth to a filtering media. Precoating reduces the
frequency of media washing and facilitates cake discharge.
PRETREATMENT	PRETREATMENT
The removal of metal, rocks, rags, sand, eggshells, and similar materials which may hinder the operation of a treatment plant.
Pretreatment is accomplished by using equipment such as racks, bar screens, comminutors, and grit removal systems.
PRIMARY TREATMENT	PRIMARY TREATMENT
A wastewater treatment process that takes place in a rectangular or circular tank and allows those substances in wastewater that
readily settle or float to be separated from the water being treated.
PROCESS VARIABLE	PROCESS VARIABLE
A physical or chemical quantity which is usually measured and controlled.
PROTEINACEOUS (PRO-ten-NAY-shus)	PROTEINACEOUS
Materials containing proteins which are organic compounds containing nitrogen.
PROTOZOA (pro-toe-ZOE-ah)	PROTOZOA
A group of microscopic animals (usually single-celled) that sometimes cluster into colonies.
PRUSSIAN BLUE	PRUSSIAN BLUE
A paste or liquid used to show a contact area. Used to determine if gate valve seats fit properly.
PSYCHROPHILIC BACTERIA (sy-kro-FILL-lick)	PSYCHROPHILIC BACTERIA
Cold temperature bacteria. A group of bacteria that grow and thrive in temperatures below 68°F (20°C).

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Glossary 599
PURGE	PURGE
To remove a gas or vapor from a vessel, reactor or confined space.
PUTREFACTION (PEW-tree-FACK-shun)	PUTREFACTION
Biological decomposition of organic matter with the production of ill-smelling products associated with anaerobic conditions.
PUTRESCIBLE (pew-TRES-uh-bull)	PUTRESCIBLE
Material that will decompose under anaerobic conditions and produce nuisance odors.
PYROMETER (pie-ROM-uh-ter)	PYROMETER
An apparatus used to measure high temperatures.
RACK	RACK
Evenly spaced parallel metal bars or rods located in the influent channel to remove rags, rocks, and cans from wastewater.
RAW WASTEWATER	RAW WASTEWATER
Plant influent or wastewater before any treatment.
REAGENT (re-A-gent)	REAGENT
A substance which takes part in a chemical reaction and is used to measure, detect, or examine other substances.
RECALCINE (re-CAL-seen)	RECALCINE
A lime-recovery process in which the calcium carbonate in sludge is converted to lime by heating at 1800°F (980°C).
RECARBONATION (re-CAR-bun-NAY-shun)	RECARBONATION
A process in which carbon dioxide is bubbled through the water being treated to lower the pH.
RECEIVING WATER	RECEIVING WATER
A stream, river, lake or ocean into which treated or untreated wastewater is discharged.
RECHARGE RATE	RECHARGE RATE
Rate at which water is added beneath the ground surface to replenish or recharge groundwater.
RECIRCULATION	RECIRCULATION
The return of part of the effluent from a treatment process to the incoming flow.
REDUCING AGENT	REDUCING AGENT
A reducing agent is any substance, such as the chloride ion (CI-) and sulfide ion (S-2), that can give up electrons. The opposite of
OXIDIZING AGENT.
REDUCTION (re-DUCK-shun)	REDUCTION
Reduction is the addition of hydrogen, removal of oxygen, or the addition of electrons to an element or compound. Under anaerobic
conditions in wastewater, sulfate compounds or elemental sulfur are reduced to odor-producing hydrogen sulfide (H2S) or the
sulfide ion (S~2). The opposite of OXIDATION.
RELIQUEFACTION (re-LICK-we-FACK-shun)	RELIQUEFACTION
The return of a gas to a liquid. For example, a condensation of chlorine gas returning to the liquid form.
REFRACTORY MATERIALS (re-FRACK-tory)	REFRACTORY MATERIALS
Material difficult to remove entirely from wastewater such as nutrients, color, taste- and odor-producing substances and some toxic
materials.
REPRESENTATIVE SAMPLE	REPRESENTATIVE SAMPLE
A portion of material or water identical in content to that in the larger body of material or water being sampled.
RESIDUAL CHLORINE	RESIDUAL CHLORINE
Residual chlorine is the amount of chlorine remaining after a given contact time and under specific conditions.
RESPIRATION	RESPIRATION
The process in which an organism uses oxygen for its life processes and gives off carbon dioxide.

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600 Treatment Plants
RETENTION TIME	RETENTION TIME
The time water, sludge or solids are retained or held in a clarifier or sedimentation tank. See DETENTION TIME.
RIPRAP	RIPRAP
Broken stones, boulders, or other materials placed compactly or irregularly on levees or dikes for the protection of earth surfaces
against the erosive action of waves.
RISING SLUDGE	RISING SLUDGE
Rising sludge occurs in the secondary clarifiers of activated sludge plants when the sludge settles to the bottom of the clarifier, is
compacted, and then starts to rise to the surface, usually as a result of denitrification.
ROTAMETER	ROTAMETER
A device used to measure the flow rate of gases and liquids. The gas or liquid being measured flows vertically up a calibrated tube.
Inside the tube is a small ball or a bullet-shaped float (it may rotate) that rises or falls depending on the flow rate. The flow rate may
be read on a scale behind the middle of the ball or the top of the float.
ROTARY PUMP	ROTARY PUMP
A type of displacement pump consisting essentially of elements rotating in a pump case which they closely fit. The rotation of these
elements alternately draws in and discharges the water being pumped. Such pumps act with neither suction nor discharge valves,
operate at almost any speed, and do not depend on centrifugal forces to lift the water.
ROTIFERS (ROE-ti-fers)	ROTIFERS
Microscopic animals characterized by short hairs on their front end.
SAR (Sodium Adsorption Ratio)	SAR
This ratio expresses the relative activity of sodium ions in the exchange reactions with soil. The ratio is defined as follows:
SAR =	Na
[1/2 (Ca + Mg) ]V4
where Na, Ca, and Mg are concentrations of the respective ions in milliequivalents per liter of water.
Na, meqIL = Na, mg/L	Qa meq/^ _ Ca, mgIL
23.0 mg/meq	20.0 mg/meq
Mg, meqIL = Mg, mg/L
12.15 mg/meq
SCFM	SCFM
Cubic Feet of air per Minute at Standard conditions of temperature, pressure and humidity.
SVI (Sludge Volume Index)	SVI
This is a test used to indicate the settling ability of activated sludge (aerated solids) in the secondary clarifier. The test is a measure
of the volume of sludge compared with its weight. Allow the sludge sample from the aeration tank to settle for 30 minutes. Then
calculate SVI by dividing the volume (ml) of wet settled sludge by the weight (mg) of that sludge after it has been dried. Sludge with
an SVI of one hundred or greater will not settle as readily as desirable because it is as light as or lighter than water.
SVI = ^et Settled Sludge, ml x 1000
Dried Sludge Solids, mg
SANITARY SEWER (SAN-eh-tare-ee SUE-er)	SANITARY SEWER
A sewer intended to carry wastewater from homes, businesses, and industries. Storm water runoff should be collected and
transported in a separate system of pipes.
SAPROPHYTIC ORGANISMS (SAP-pro-FIT-tik)	SAPROPHYTIC ORGANISMS
Organisms living on dead or decaying organic matter. They help natural decomposition of the organic solids in wastewater.
SCREEN	SCREEN
A device used to retain or remove suspended or floating objects in wastewater. The screen has openings that are generally uniform
in size. It retains or removes objects larger than the openings. A screen may consist of bars, rods, wires, gratings, wire mesh, or
perforated plates.
SEALING WATER	SEALING WATER
Water used to prevent wastewater or dirt from reaching moving parts. Sealing water is at a higher pressure than the wastewater it is
keeping out of a mechanical device.

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Glossary 601
SECCHI DISC (SECK-key)	SECCHI DISC
A flat, white disc lowered into the water by a rope until it is just barely visible. At this point, the depth of the disc from the water
surface is the recorded secchi disc reading.
SECONDARY TREATMENT	SECONDARY TREATMENT
A wastewater treatment process used to convert dissolved or suspended materials into a form more readily separated from the
water being treated. Usually the process follows primary treatment by sedimentation. The process commonly is a type of biological
treatment process followed by secondary clarifiers that allow the solids to settle out from the water being treated.
SEED SLUDGE	SEED SLUDGE
In wastewater treatment, seed, seed culture or seed sludge refers to a mass of sludge which contains very concentrated populations
of microorganisms. When a seed sludge is mixed with the wastewater or sludge being treated, the process of biological decomposi-
tion takes place more rapidly.
SEIZING	SEIZING
Seizing occurs when an engine overheats and a component expands so the engine will not run. Also called "freezing."
SEPTIC (SEP-tick)	SEPTIC
This condition is produced by anaerobic bacteria. If severe, the wastewater turns black, gives off foul odors, contains little or no
dissolved oxygen and creates a heavy oxygen demand.
SEPTICITY (sep-TIS-it-tee)	SEPTICITY
Septicity is the condition in which organic matter decomposes to form foul-smelling products associated with the absence of free
oxygen. If severe, the wastewater turns black, gives off foul odors, contains little or no dissolved oxygen and creates a heavy oxygen
demand.
SERIES OPERATION	SERIES OPERATION
When wastewater being treated flows through one treatment unit and then flows through another similar treatment unit. Also see
PARALLEL OPERATION.
SET POINT	SET POINT
The position at which the control or controller is set. This is the same as the desired value of the process variable.
SEWAGE	SEWAGE
The used water and solids from homes that flow to a treatment plant. The preferred term is wastewater.
SHEAR PIN	SHEAR PIN
A straight pin with a groove around the middle that will weaken the pin and cause it to fail when a certain load or stress is exceeded.
The purpose of the pin is to protect equipment from damage due to excessive loads or stresses.
SHOCK LOAD	SHOCK LOAD
The arrival at a plant of a waste which is toxic to organisms in sufficient quantity or strength to cause operating problems. Possible
problems include odors and sloughing off of the growth or slime on the trickling-filter media. Organic or hydraulic overloads also can
cause a shock load.
SHORT-CIRCUITING	SHORT-CIRCUITING
A condition that occurs in tanks or ponds when some of the water or wastewater travels faster than the rest of the flowing water.
SHREDDING	SHREDDING
Comminution. A mechanical treatment process which cuts large pieces of wastes into smaller pieces so they won't plug pipes or
damage equipment. SHREDDING and COMMINUTION usually mean the same thing.
SIDESTREAM	SIDESTREAM
Wastewater flows that develop from other storage or treatment facilities. This wastewater may or may not need additional treatment.
SIGNIFICANT FIGURE	SIGNIFICANT FIGURE
The number of accurate numbers in a measurement. If the distance between two points is measured to the nearest hundredth and
recorded as 238.41 feet, the measurement has five significant figures.
SINGLE-STAGE PUMP	SINGLE-STAGE PUMP
A pump that has only one impeller. A multi-stage pump has more than one impeller.

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602 Treatment Plants
SKATOLE (SKATE-tole)	SKATOLE
An organic compound (C9H9N) containing nitrogen which has a fecal odor.
SLAKE	SLAKE
To become mixed with water so that a true chemical reaction takes place, such as in the slaking of lime.
SLOUGHINGS (SLUFF-ings)	SLOUGHINGS
Trickling-filter slimes that have been washed off the filter media. They are generally quite high in BOD and will lower effluent quality
unless removed.
SLUDGE (sluj)	SLUDGE
The settleable solids separated from liquids during processing or the deposits of foreign materials on the bottoms of streams or
other bodies of water.
SLUDGE AGE	SLUDGE AGE
A measure of the length of time a particle of suspended solids has been undergoing aeration in the activated sludge process.
Sludge Age days = Suspended Solids Under Aeration, lbs or kg
Suspended Solids Added, lbs/day or kg/day
SLUDGE DENSITY INDEX (SDI)	SLUDGE DENSITY INDEX (SDI)
This test is used in a way similar to the Sludge Volume Index (SVI) to indicate the settleability of a sludge in a secondary clarifier or
effluent. SDI = 100/SVI. Also see SLUDGE VOLUME INDEX (SVI).
SLUDGE DIGESTION	SLUDGE DIGESTION
The process of changing organic matter in sludge into a gas or a liquid or a more stable solid form. These changes take place as
microorganisms feed on sludge in anaerobic (more common) or aerobic digesters.
SLUDGE GASIFICATION	SLUDGE GASIFICATION
A process in which soluble and suspended organic matter are converted into gas by anaerobic decomposition. The resulting gas
bubbles can become attached to the settled sludge and cause large clumps of sludge to rise and float on the water surface.
SLUDGE VOLUME INDEX (SVI)	SLUDGE VOLUME INDEX (SVI)
This is a test used to indicate the settling ability of activated sludge (aerated solids) in the secondary clarifier. The test is a measure
of the volume of sludge compared with its weight. Allow the sludge sample from the aeration tank to settle for 30 minutes. Then
calculate SVI by dividing the volume (ml) of wet settled sludge by the weight (mg) of that sludge after it has been dried. Sludge with
an SVI of one hundred or greater will not settle as readily as desirable because it is as light as or lighter than water.
gyi _ Wet Settled Sludge, ml x 1000
Dried Sludge Solids, mg
SLUDGE-VOLUME RATIO (SVR)	SLUDGE-VOLUME RATIO (SVR)
The volume of sludge blanket divided by the daily volume of sludge pumped from the thickener.
SLUGS	SLUGS
Intermittent releases or discharges of industrial wastes.
SLURRY (SLUR-e)	SLURRY
A thin watery mud or any substance resembling it (such as a grit slurry or a lime slurry).
SODIUM ADSORPTION RATIO (SAR)	SODIUM ABSORPTION RATIO (SAR)
This ratio expresses the relative activity of sodium ions in the exchange reactions with soil. The ratio is defined as follows:
SAR =	—	
IV2 (Ca + Mg)]*
where Na, Ca, and Mg are concentrations of the respective ions in milliequivalents per liter of water.
Na,meqIL = 	Na' m9/L		Ca, meq/L = 	Ca' m9/L	
23.0 mg/meq	20.0 mg/meq
Mg, meq/L = 	Mg' mg/L	
12.15 mg/meq
SOLUBLE BOD	SOLUBLE BOD
Soluble BOD is the BOD of water that has been filtered in the standard suspended solids test.

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Glossary 603
SOLUTE	SOLUTE
The substance dissolved in a solution. A solution is made up of the solvent and the solute.
SOLUTION	SOLUTION
A liquid mixture of dissolved substances. In a solution it is impossible to see all the separate parts.
SPECIFIC GRAVITY	SPECIFIC GRAVITY
Weight of a particle or substance in relation to the weight of water. Water has a specific gravity of 1.000 at 4°C (or 39°F). Wastewater
particles usually have a specific gravity of 0.5 to 2.5.
SPLASH PAD	SPLASH PAD
A structure made of concrete or other durable material to protect bare soil from erosion by splashing or falling water.
STABILIZE	STABILIZE
To convert to a form that resists change. Organic material is stabilized by bacteria which convert the material to gases and other
relatively inert substances. Stabilized organic material generally will not give off obnoxious odors.
STABILIZED WASTE	STABILIZED WASTE
A waste that has been treated or decomposed to the extent that, if discharged or released, its rate and state of decomposition would
be such that the waste would not cause a nuisance or odors.
STANDARD SOLUTION	STANDARD SOLUTION
A solution in which the exact concentration of a chemical or compound is known.
STANDARDIZE	STANDARDIZE
(1) To compare with a standard. In wet chemistry, to find out the exact strength of a solution by comparing with a standard of known
strength. This information is used to adjust the strength by adding more water or more of the substance dissolved. (2) To compare
an instrument or device with a standard. This helps you to adjust the instrument so that it reads accurately or to prepare a scale,
graph or chart that is accurate.
STASIS (STAY-sis)	STASIS
Stagnation or inactivity of the life processes within organisms.
STATIC HEAD	STATIC HEAD
When water is not moving, the distance (in feet or meters) from a point to the water surface.
STATOR	STATOR
That portion of a machine which contains the stationary (non-moving) parts that surround the moving parts.
STEP-FEED AERATION	STEP-FEED AERATION
Step-feed aeration is a modification of the conventional activated sludge process. In step aeration, primary effluent enters the
aeration tank at several points along the length of the tank, rather than all of the primary effluent entering at the beginning or head of
the tank and flowing through the entire tank.
STERILIZATION (star-uh-luh-ZAY-shun)	STERILIZATION
The removal or destruction of all living microorganisms, including pathogenic and saprophytic bacteria, vegetative forms and
spores. Compare with DISINFECTION.
STETHOSCOPE	STETHOSCOPE
An instrument used to magnify sounds and convey them to the ear.
STOP LOG	STOP LOG
A log or board in an outlet box or device used to control the water level in ponds.
STORM SEWER	STORM SEWER
A separate sewer that carries runoff from storms, surface drainage, and street wash, but does not include domestic and industrial
wastes.
STRIPPED GASES	STRIPPED GASES
Gases that are released from a liquid by bubbling air through the liquid or by allowing the liquid to be sprayed or tumbled over media.

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604 Treatment Plants
STRIPPED ODORS	STRIPPED ODORS
Odors that are released from a liquid by bubbling air through the liquid or by allowing the liquid to be sprayed and/or tumbled over
media.
STUCK	STUCK
Not working. A stuck digester does not decompose organic matter properly. The digester is characterized by low gas production,
high volatile acid to alkalinity relationship, and poor liquid-solids separation. A digester in a stuck condition is sometimes called a
"sour" or "upset" digester.
SUCTION HEAD	SUCTION HEAD
The pressure (in feet (meters) or pounds per square inch (kilograms per square centimeter)) on the suction side of a pump. The
pressure can be measured from the center line of the pump UP TO the elevation of the hydraulic grade line on the suction side of the
pump.
SUCTION LIFT	SUCTION LIFT
The NEGATIVE pressure (in feet (meters) or inches (centimeters) of mercury vacuum) on the suction side of the pump. The pressure
can be measured from the center line of the pump DOWN to the elevation of the hydraulic grade line on the suction side of the pump.
SUPERNATANT (sue-per-NAY-tent)	SUPERNATANT
Liquid removed from settled sludge. Supernatant commonly refers to the liquid between the sludge on the bottom and the scum on
the surface of an anaerobic digester. This liquid is usually returned to the influent wet well or to the primary clarifier.
SURFACE LOADING	SURFACE LOADING
Surface loading is calculated by dividing the flow into a sedimentation tank or a clarifier by the surface area of the unit.
Surface Loading, gpd/sq ft = Flow, gpd
Surface Area, sq ft
SURFACTANT	SURFACTANT
Abbreviation for surface-active agent. The active agent in detergents that possesses a high cleaning ability.
SUSPENDED SOLIDS	SUSPENDED SOLIDS
(1) Solids that either float on the surface of, or are in suspension in, water, wastewater, or other liquids, and which are largely
removable by laboratory filtering. (2) The quantity of material removed from wastewater in a laboratory test, as prescribed in
STANDARD METHODS FOR THE EXAMINATION OF WATER AND WASTEWATER and referred to as nonfilterable residue.
TOC	TOC
Total Organic Carbon. TOC measures the amount of organic carbon in water.
TERTIARY TREATMENT (TER-she-AIR-ee)	TERTIARY TREATMENT
Any process of water renovation that upgrades treated wastewater to meet specific reuse requirements. May include general
cleanup of water or removal of specific parts of wastes insufficiently removed by conventional treatment processes. Typical
processes include chemical treatment and pressure filtration. Also called ADVANCED WASTE TREATMENT.
THERMOPHILIC BACTERIA (thermo-FILL-lick)	THERMOPHILIC BACTERIA
Hot temperature bacteria. A group of bacteria that grow and thrive in temperatures above 113°F (45°C). The optimum temperature
range for these bacteria in anaerobic decomposition is 120°F (49°C) to 135°F (57°C).
THIEF HOLE	THIEF HOLE
A digester sampling well.
THRESHOLD ODOR	THRESHOLD ODOR
The minimum odor of a sample (gas or water) that can just be detected after successive odorless (gas or water) dilutions.
TIME LAG	TIME LAG
The time required for processes and control systems to respond to a signal or to reach a desired level.
TITRATE (TIE-trate)	TITRATE
To TITRATE a sample, a chemical solution of known strength is added on a drop-by-drop basis until a color change, precipitate, or
pH change in the sample is observed (end point). Titration is the process of adding the chemical solution to completion of the
reaction as signaled by the end point.

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Glossary 605
TOTAL DYNAMIC HEAD (TDH)	TOTAL DYNAMIC HEAD (TDH)
When a pump is lifting or pumping water, the vertical distance (in feet or meters) from the elevation of the energy grade line on the
suction side of the pump to the elevation of the energy grade line on the discharge side of the pump.
TOTAL RESIDUAL CHLORINE	TOTAL RESIDUAL CHLORINE
The amount of chlorine remaining after a given contact time. The sum of the combined available residual chlorine and the free
available residual chlorine. Also see RESIDUAL CHLORINE.
TOTALIZER	TOTALIZER
A device that continuously sums or adds the flow into a plant in gallons or million gallons or some other unit of measurement.
TOXIC (TOX-ick)	TOXIC
Poisonous.
TOXICITY (tox-IS-it-tee)	TOXICITY
A condition which may exist in wastes and will inhibit or destroy the growth or function of certain organisms.
TRANSPIRATION (TRAN-spear-RAY-shun)	TRANSPIRATION
The process by which water vapor is lost to the atmosphere from living plants.
TRICKLING FILTER	TRICKLING FILTER
A treatment process in which the wastewater trickles over media that provide the opportunity for the formation of slimes or biomass
which contain organisms that feed upon and remove wastes from the water treated.
TRICKLING-FILTER MEDIA	TRICKLING-FILTER MEDIA
Rocks or other durable materials that make up the body of the filter. Synthetic (manufactured) media have been used successfully.
TRUNK SEWER	TRUNK SEWER
A sewer that receives wastewater from many tributary branches or sewers and serves a large territory and contributing population.
TURBID	TURBID
Having a cloudy or muddy appearance.
TURBIDITY METER	TURBIDITY METER
An instrument for measuring the amount of particles suspended in water. Precise measurements are made by measuring how light
is scattered by the suspended particles. The normal measuring range is 0 to 100 and is expressed as Nephelometric Turbidity Units
(NTU's).
TURBIDITY UNITS	TURBIDITY UNITS
Turbidity units, if measured by a nephelometric (reflected light) instrumental procedure, are expressed in nephelometric turbidity
units (NTU). Those turbidity units obtained by other instrumental methods or visual methods are expressed in Jackson Turbidity
Units (JTU) and sometimes as Formazin Turbidity Units (FTU). The FTU nomenclature comes from the Formazin polymer used to
prepare the turbidity standards for instrument calibration. Turbidity units are a measure of the cloudiness of water.
TWO-STAGE FILTERS	TWO-STAGE FILTERS
Two filters are used. Effluent from the first filter goes to the second filter, either directly or after passing through a clarifier.
ULTRAFILTRATION	ULTRAFILTRATION
A membrane filtration process used for the removal of organic compounds in an aqueous (watery) solution.
UPSET	UPSET
An upset digester does not decompose organic matter properly. The digester is characterized by low gas production, high volatile
acid/alkalinity relationship, and poor liquid-solids separation. A digester in an upset condition is sometimes called a "sour" or "stuck"
digester.
VELOCITY HEAD	VELOCITY HEAD
A vertical height (in feet or meters) equal to the square of the velocity of flowing water divided by twice the acceleration due to gravity
(V*/2g).
VOLATILE (VOL-a-til)	VOLATILE
A volatile substance is one that is capable of being evaporated or changed to a vapor at relatively low temperatures.

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606 Treatment Plants
VOLATILE ACIDS	VOLATILE ACIDS
Acids produced during digestion. Fatty acids which are soluble in water and can be steam-distilled at atmospheric pressure. Also
called "organic acids." Volatile acids are commonly reported as equivalent to acetic acid.
VOLATILE LIQUIDS	VOLATILE LIQUIDS
Liquids which easily vaporize or evaporate at room temperature.
VOLATILE SOLIDS	VOLATILE SOLIDS
Those solids in water, wastewater, or other liquids that are lost on ignition of the dry solids at 550°C.
VOLUMETRIC	VOLUMETRIC
A means of measuring unknown concentrations of water quality indicators in a sample BY DETERMINING THE VOLUME of titrant or
liquid reagent needed to complete particular reactions.
VOLUTE (vol-LOOT)	VOLUTE
The spiral-shaped casing which surrounds a pump, blower, or turbine impeller and collects the liquid or gas discharged by the
impeller.
WASTEWATER	WASTEWATER
The used water and solids from a community that flow to a treatment plant. Storm water, surface water, and groundwater infiltration
also may be included in the wastewater that enters a plant. The term "sewage" usually refers to household wastes, but this word is
being replaced by the term "wastewater."
WATER HAMMER	WATER HAMMER
The sound like someone hammering on a pipe that occurs when a valve is opened or closed very rapidly. When a valve position is
changed quickly, the water pressure in a pipe will increase and decrease back and forth very quickly. This rise and fall in pressures
can do serious damage to the system.
WEIR (weer)	WEIR
(1) A wall or plate placed in an open channel and used to measure the flow. The depth of the flow over the weir can be used to
calculate the flow rate, or a chart or conversion table may be used. (2) A wall or obstruction used to control flow (from clarifiers) to
assure uniform flow and avoid short-circuiting.
WEIR DIAMETER (weer)	WEIR DIAMETER
Many circular clarifiers have a circular weir within the outside edge of		
the clarifier. All the water leaving the clarifier flows over this weir. The	7
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Index 607
SUBJECT INDEX
VOLUME II
A
Abnormal operation
activated sludge, 54, 57, 64
aerobic digestion, 161
anaerobic digestion, 138, 139
effluent disposal, 191
Absorbance, light, 349
Accident
form, 231
frequency, 209
investigation, 230
operators, 209, 230
prevention, 356
record, 231
reports, 550
Accidental spills, 13
Acid formers, 98, 100, 136
Acidity test, 363, 398
Acids, 210, 354
Activated sludge
also see Volume I, Chapter 8
and Volume III, Chapter 21
abnormal operation, 54, 57, 64
actual operation, 50, 54
aeration methods, 16, 20
aeration tank, 15, 20, 28, 35, 36, 37, 43, 49, 50, 62, 221
aerobic digestion, 159
also see Volume III, Chapter 22
air system, see Air systems
ammonia removal, see Volume III, Chapter 21
BOD. 15, 54
blowers, 22, 35, 39, 41, 64, 66, 70
brown foam, 49, 60
bulking, 59, 66, 75
COD, 15, 54
canning season, 54, 58, 72
chemical addition, 43, 54, 59
clarifiers, 15, 28, 41, 50, 60, 75
collection system, 13
complete mix, 50, 75, 77
compressors, see Blowers
contact stabilization, 50, 72, 73
contact time, 20, 43, 50, 58, 59, 75, 78
control of process, 46, 62
control tests, 377
conventional activated sludge, 16,19,43, 46,47, 57, 62,72,
75
daily observations, 15
dark foam, 49, 60
denitrification, 60, 75
description, 36
design variables, 16, 19, 60
detention time, see contact time
diffusers, 18, 20, 28, 35, 40, 64, 66, 71
dissolved oxygen, 15, 43, 44, 49, 50, 59, 60, 75
efficiency of process, 13, 51, 53
effluent, 13, 16, 19, 38, 43, 46, 50, 52, 54, 57, 59, 60, 75
emergency procedures, 54
energy use, 15
equipment, 16, 22, 28, 57, 63, 64, 65, 66, 67, 68, 69, 70, 71
extended aeration, 19, 49, 60, 62
F/M ratio, 15, 19, 59, 60, 62
filamentous growths, 50, 51, 53, 59, 60, 75
filters (air), 22, 23, 35, 38
foam, 38, 43, 50, 60
food/microorganism ratio, 15, 19, 59, 60, 6?
formulas, 507, 509
high-rate, 19, 47, 62, 75, 78
housekeeping, 35, 40
hydraulic loading, 13, 51, 53, 58
influent, 13, 49, 52, 57, 58, 60, 75
industrial waste treatment, 13, 51, 54, 58, 75
also see Volume III, Chapters 21 and 28
inspecting new facilities, 36
Kraus process, 59, 72, 74
lab results, 13, 16
layout, 48, 73, 74
loadings, 62
MCRT, 15, 62, 63
MLSS, 19, 44, 50, 57, 58, 59, 60, 62, 75
MLVSS, 19, 50, 58, 62
maintenance, 61, 63, 64, 66
mean cell residence time, 15, 62, 63
mechanical aeration, 16,17, 20, 21, 64
metric, 79
microorganisms, 43, 47, 49, 57, 58, 59, 60, 62, 72
microscopic examination, 50
mixed liquor suspended solids, 19,44, 50,57, 58,59,60,62,
75
mixed liquor volatile suspended solids, 19, 50, 58, 62
mixing, 43, 49, 60
modifications, 19, 72
modified aeration, 75, 78
nitrification
see Volume III, Chapter 21
nitrogen requirements, 59, 72, 75
normal operation, 46, 50
nutrient requirements, 59, 72, 75
objectives, 6
odors, 15, 60
operation, 13, 46, 50, 62, 63
operational strategy, 49, 50, 51
organic loading, 13
organisms, 43, 47, 49, 58, 59, 60, 62, 72
oxidation, 58, 59
oxidation ditch
see Volume I, Chapter 8
oxygen requirements, 43, 44, 49, 50, 58
oxygen transfer, 20, 28
package plants
see Volume I, Chapter 8

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608 Treatment Plants
pH, 15, 59
plans and specifications
see Volume I, Chapter 8
problems, 57, 64
problems (arithmetic), 500, 504
pumps, 41, 250
pure oxygen, 20
also see Volume III, Chapter 21
purpose, 6, 20, 72
RAS, 13, 16, 41, 44, 45, 50, 59, 60, 75
re-aeration, 72, 73, 74, 75
record keeping, 13, 15, 36, 41, 42, 50, 57
return sludge, 13, 16, 41, 44, 45, 50, 59, 60, 75
rising sludge, 60, 75
SDI, 378
SVI, 50, 51, 53, 378
safety, 29, 35, 41, 61
sampling, 15
secondary clarifiers, 15, 28, 41, 50, 60, 75
seed organisms, 43, 44
septic sludge, 45, 60
settleability tests, 44, 45, 50, 60
settlometer, 44, 377
shock loads, 13, 57, 75
short-circuiting, 38
shutdown, 63, 64
sludge age, 15, 16, 46, 58, 59, 60, 62, 378
sludge blanket, 50, 57, 59, 60, 75
sludge bulking, 59, 66, 75
sludge density index, 378
sludge pumps, 41, 50
sludge return, 13, 16, 41, 44, 45, 50
sludge volume index, 50, 51, 53, 378
sludge wasting, 13, 41, 46, 47, 48, 49, 50
solids, 13, 15, 38, 43, 44, 45, 47, 58, 60, 62, 75
Start up, 43, 63
step-feed aeration, 38, 49, 75, 76
storm flows, 13, 51, 52, 58, 72, 75
supernatant return, 13, 57, 58, 60, 72, 75
surface aerators, 17, 21, 35, 64, 65, 66
surfactants, 60
TOC, 15
temperature, 13, 15, 46, 58
thick foam, 49
toxic wastes, 58, 60, 72
trend chart, 50
troubleshooting, 57, 64
types of processes, 72
upset, 15
variables, 13, 19, 72
visual inspection, 15, 50
WAS, 13, 41, 46, 47, 49, 50, 136
wasting sludge, 13, 41, 46, 47, 48, 49, 50, 136
white foam, 38, 49
Activated sludge control tests, 377
Addition, 475
Advanced waste treatment
See Volume III
Aeration tanks, activated sludge, 15, 20, 28,35,36,37, 43,49,
50, 62, 221
Aerobes, 43
Aerobic sludge digestions
also see Volume III, Chapter 22
abnormal operation, 161
aeration equipment, 161
aerobic, 159, 160
bacteria, 98
comparison with anaerobic, 159, 160
costs, 160
covers, 160
decomposition of solids, 159
description, 160
detention time, 160
dewatering, 160, 161
diffusers, 161
disposal of solids, 161
dissolved oxygen, 160, 161
drying beds, 161
effluent, 160
endogenous, 160
energy, 159, 160
equipment, 160, 161
extended aeration, 160
floating sludge, 161
food, 160, 161
maintenance, 161
mechanical dewatering, 161
metric, 170
microorganisms, 98, 161
nitrogen removal, 160
normal operation, 160
odors, 159, 160, 161
operation, 160
organisms, 161
oxygen demand, 161
primary sludge, 160
problems, 161
process description, 160
pumping sludge, 160
purpose, 98
raw sludge, 160, 161
record keeping, 161
scum, 161
secondary sludge, 160, 161
shock load, 161
sludge, 160, 161
solids, 159, 160, 161
stabilization, 160
start-up, 160
supernatant, 160, 161
temperature, 160
toxic wastes, 161
troubleshooting, 161
volatile material, 159, 160, 161
withdrawal of sludge, 161
Air chamber, pump, 283, 284
Air-gap device, 227, 228, 308
Air strainer, ejectors, 285
Air systems, activated sludge
aeration methods, 16
aeration systems, 20, 57
blowers, 22, 35, 39, 64, 66, 67, 70
coarse bubble diffusers, 28, 33
compressors, see blowers
condensate traps, 28
diffused air, 20, 64
diffusers, 18, 28, 31, 32, 35, 36, 50, 64, 66, 70, 71
distribution system, 28, 29, 35, 64, 66, 68, 71
filters, 22, 23, 35, 38, 64, 66
fine bubble diffusers, 28, 32
headers, 20, 28, 30, 31, 35, 36, 40, 64, 66, 69, 71
hoists, 28, 35
inspecting new facilities, 38
leveling header, 28
mechanical, 16, 17, 20
metering, 28, 39
methods, 16, 17, 18

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Index 609
odorous air, 22
orifice, 28, 39
parts, 28, 29, 30, 31
process systems, 22
purpose, 20
safety, 28, 35
sources of air, 22
start-up, 38
surface aerators, 20, 35, 64, 65, 66
systems, 20, 22
testing, 41
types, 20
Alignment, pumps, 254, 270, 278, 293, 294
Aliquot, 420
Alkalinity, 98, 101, 137, 138, 142, 151
Alkalinity tests, 363, 387, 399
Ambient, 455
Amebiasis, 355
Amines, 224
Ammeter, 274
Ammonia test, 363, 433
Amperometric, 405
Anaerobic environment, 354
Anaerobic sludge digestion
also see Volume III, Chapter 22
abnormal operation, 138, 139
acid formers, 98, 100, 136
actual operation, 155, 156
alkalinity, 98, 101, 137, 138, 142, 151
anaerobic, 98, 106
bacteria, 98, 100, 101, 136
boiler, 127, 149, 154
buffer, 101, 137, 138, 141, 142
carbon dioxide, 107, 136, 142, 143, 144, 145, 146, 151, 154,
160
centrifuge, 138, 166
cleaning, pipelines and digesters, 101, 102, 135, 150, 155,
157, 158
comparison with aerobic, 159, 160
computations, 145
condensate traps, 102, 105, 108, 117, 118, 119, 149
coning, 137
control of process, 101, 142
corbels, 103, 132, 133
costs, 160
covers, 103, 132
definition, 98
description, 98
digested sludge disposal, 161
digested sludge removal, 103
digestion time, 98, 101, 155
dissolved air flotation, 138
drip traps, 108, 117, 118, 119, 149
drying beds, 103, 161
energy, 107, 139, 160
enzymes, 139, 141
equipment, 102, 103, 107, 117, 129, 132
explosion, 109, 112
feed, 101, 135, 137, 139, 142, 150, 153
fixed cover, 103, 104, 132
flame arresters, 102, 105, 108, 109, 113, 114, 115, 116
floating cover, 103, 132, 150
flow diagram, 99
foam, 136, 139
food supply, 98
formulas, 508, 509
gas, 139, 142, 145
gas dome, 107
gas meter, 108, 117, 145, 149
gas mixing, 129
gas production, 107, 139, 142, 145, 148, 151, 155
gas system, 102, 105, 107, 154
heat value of gas, 107
heating, 117, 127, 128, 149, 154
high-rate, 98, 101
inlet, 103, 104, 142
inspecting new facilities, 102, 107, 117, 129
lab results, 101, 142, 155
lime, 138
liquid-solids separation, 101, 141
loadings, 145, 148, 153, 154
maintenance, 101, 102, 109, 117, 132, 148, 149, 150, 169
mechanical dewatering, 164
mechanical mixing, 129, 130, 131
mesophilic bacteria, 101, 142
methane fermenters, 98, 100, 136
methane gas, 98, 107, 136, 143, 144, 160
metric, 170
microorganisms, 98, 100, 101, 136
mixing, 98, 129, 130, 131, 139, 153, 154, 155
neutralizing, 138, 153
normal operation, 135, 142, 153
objectives, 95, 98
odors, 139, 149, 157
operation, 98, 101, 135, 142, 148, 153
operational strategy, 148
organisms, 98, 100, 101, 136
pH, 98, 136, 138, 142, 151
pipelines, 102
plans and specifications, 169
pressure regulators, 108, 117, 120, 121, 122, 123
pressure relief valves, 102, 105, 108, 109, 110, 111, 115,
116
problems, 136
problems (arithmetic), 501, 505
psychrophilic bacteria, 101
pumping sludge, 137, 143, 149, 153, 154
purpose, 95, 98, 102
putrefaction, 160
raw sludge, 103, 135, 143, 149, 150
reactions, 98, 100
recirculated sludge, 143
record keeping, 101, 148, 150, 153, 155
reduction in volatile solids, 143, 154
review of plans and specifications, 169
safety, 102, 103, 107, 109, 112, 134, 137, 141, 157
sampling, 142, 150
sampling well, 117, 125, 126
scum, 132, 135, 150
secondary digested sludge, 144
secondary digestion, 101
sediment traps, 102, 105, 108, 117, 118, 119, 149
seed organisms, 101, 103, 136, 137, 141, 145
septic sludge, 142, 149
shock loads, 142
shutdown, 155, 157
sludge, 137, 143, 149
sludge draw-off lines, 103
sludge drying beds, 161
sludge pumps, 143, 149, 154
sludge withdrawal, 141, 142
solids, 135, 137, 138, 139, 142, 143, 145, 146
solids balance, 146, 151
sour, 135, 136, 138, 142
stabilize, 139, 160
standard rate, 98
start-up, 136

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610 Treatment Plants
stuck, 135, 136, 138, 142
supernatant, 101, 103, 137, 139, 143, 144, 145, 151, 153,
156
supernatant tubes, 103, 104, 106 149, 150
temperature, 98, 101, 142, 148, 151, 153, 155
thermal valves, 108, 109
thermophilic bacteria, 101
thief hole, 117, 125, 126
thin sludge, 137
time for digestion, 98, 101
toxic wastes, 153, 154, 155
traps, 117
trend chart, 142, 148, 150
troubleshooting, 153
upset, 135, 136, 138, 142
use of gas, 107, 139
vacuum filters, 166
vacuum relief valves, 102, 105, 108, 109, 110, 111
valves, 102, 109, 149, 150
visual inspection, 148, 149
volatile acid/alkalinity, 98,138,142,145,148,151,153,154,
155
volatile solids, 98, 138, 143, 151, 154, 155
waste activated sludge, 135
waste gas burner, 108, 117, 150
water seal, 102, 105, 139, 150
withdrawal of sludge, 141, 142, 153
Analysis of data
see Data analysis and presentation
Analytical balance, 346
Annual operating reports, 556
Applying protective coatings, 223
Areas
circle, 483
cone, 484
cylinder, 484
formulas (English System), 507
formulas (Metric System), 508
rectangle, 483
sphere, 485
triangle, 483
Arithmetic
addition, 475
areas, 483
average, 520, 528
cancellation, 479
cross multiplication, 480
cubes, 482
decimal fractions, 479
decimals, 475
denominator, 478
dimensions, 475, 476, 498
dividend, 477
division, 477
divisor, 477
fractions, 478
geometric mean, 522
improper fractions, 478
least common denominator, 478
logarithms, 523
mean, 482, 520
median, 482, 521
metric system, 486, 539
mode, 521
moving averages, 528
multiplication, 476
numerator, 478
percentage, 479
proportion, 480
quotient, 477
range of values, 521
ratio, 480
reducing fractions, 478
roots, 481, 482, 539
rounding off numbers, 477, 498
squares, 481
subtraction, 475
variance, 533
volumes, 485
weight-volume relations, 488
whole numbers, 475
Arithmetic mean, 520
Arrangement of formula, 498
As built plans and specs, 551
Aseptic, 422
Autoclave, 410
Automatic samplers, 361
Average, 520, 528
Axial flow pumps, 257, 263
B
BOD bottle, 342
BOD incubator, 346
BOD test, 363, 427
BOD test, chlorinated samples, 429
BOD test, industrial wastes, 431
BTU, 107
Backflow prevention, 227
Balance, analytical, 346
Ball valves, 283, 284
Bar graphs, 530
Bar screens
also see Volume I, Chapter 4
safety, 215
Bases, 210, 354
Beakers, 340, 348
Bearings, electric motor, 287
Bearings, pump, 250, 253, 258, 259, 265, 269, 273, 278, 285
Beer's Law, 349
Belt drives, pump maintenance, 270, 290, 291
Bench sheets, 350
Bioassay, 420
Biocatalysts, 130
Biochemical oxygen demand test, 363, 427
Biocides, 224
Blacktop drying beds
cleanout, 164
depth of sludge, 164
description, 164, 165
drain channel, 164, 165
drying time, 164
maintenance, 164
operation, 164
purpose, 164
sampling, 164
time for drying, 164
Blank sample, 349, 402
Blowdown receiver, ejectors, 285
Blowers
abnormal conditions, 66, 67
air compressors, 22
air discharge silencer, 22
bearings, 22
centrifugal, 22, 27, 64
ear protective devices, 22
filters, 22, 23, 35, 64, 66
inspecting new facilities, 39
lubrication, 22, 28

-------
maintenance, 22, 28, 70
manufacturer's manual, 39
metering, 28
orifice, 28
output, 22
performance, 22, 24, 25, 26
positive displacement, 22, 64
process air compressors, 22
safety, 22, 35, 210, 210, 308
silencer, 22
start-up, 39
testing, 41
troubleshooting, 66, 67
ventilation, 308
vibration, 22
Blueprint reading, 503, 507
Boiler, 127, 149, 154, 221
Boiling flask, 341
Bonnet valve, 301, 303
Bottle, BOD, 342
Bottle, reagent, 342
Breathing apparatus, self-contained, 222, 357
Brown foam, activated sludge, 38, 49, 60
Bubbler-type controls, 269
Buchner funnel, 342
Buffer, 101, 137, 138, 141, 142, 410
Buildings, maintenance, 247
Bulking
activated sludge, 59, 66, 75
filamentous growth, 50, 59
Bunsen burner, 344
Burets, 341, 346
Burner, Bunsen, 344
Burns, 356
C
COD test, 363, 401
COD to BOD curves, 533
Calculation of square root, 539
Calculations, 498
Calibration curves, 349
Calibration, flow meters, 318, 493
Calibration, gas detectors, 308
Cancellation of numbers, 479
Capacity, pump, 256, 278
Carbon absorption, physical chemical treatment
see Volume III, Chapter 28
Carbon analyzer, 456
Carbon dioxide, 107, 136, 142, 148, 151, 154, 160, 383
Carbon dioxide test, 389
Carbon measurement, 456
Carbon tetrachloride, 290, 354
Carcinogens, 224
Casing, pump, 250, 254, 258, 259
Causes of data variations, 518
Cavitation, 256
Centrate, 168
Centrifugal pumps
description, 250, 257, 258, 259
maintenance, 276
Centrifugation
also see Volume III, Chapter 22
cake, 169
conditioning, 166
description, 166, 168
operation, 166, 169
sludge, 166
sludge dewatering, 138, 141, 166
use, 166
Index 611
Centrifuge, clinical, 367, 380
Chain drives, 290
Change oil, pump, 283
Channels (flow), maintenance, 247
Characteristics of wastewater
see Wastewater characteristics
Chart, recording, 316, 317, 318
Charts, 520, 530, 531, 533
Check valves, 271, 278, 285, 299, 300
Chemical formulas, 339
Chemical names, 335, 339
Chemical oxygen demand
compared with BOD, 401
concentration in wastewater, 401
preservation, 363
test, 401
Chemical storage, 225, 342, 355
Chemicals, 354
Chemicals, safety, 225
Chemicals, toxic, 210
Chemistry
see Laboratory procedures
CHEMTREC, 249
phone (800) 424-9300
Chlorinated samples, BOD, 429
Chlorination
see Volume I, Chapter 10
formulas, 508, 509
problems (arithmetic), 502, 506
Chloride, test, 403
Chlorinators
emergencies, 249
leak detection, 248
maintenance, 248
safety, 249
Chlorine detector, 210
Chlorine leaks, 558
Chlorine residual test, 405
Chlorine safety, 216, 222
Cholera, 355
Circle, 483
Cipoletti weir, 313, 316
Circuit breakers, 270
Clamps, 341, 344
Clarifiers, safety, 219
also see Sedimentation
Clarity test, 364
Cleaning digesters, 155, 157, 158
Cleaning pipelines, 102, 311, 312
Cleaning pumps, 276
Clearing plugged pipes, pumps and valves
costs, 311
cutting tools, 312
digested sludge lines, 311
equipment, 311, 312
high velocity pressure units, 312
methods of clearing, 311, 312
pipes, 311
pressure clearing methods, 311
pumps, 312
scum lines, 311
sludge lines, 311
valves, 312
Climate, sludge dewatering, 163
Clinical centrifuge, 367, 380
Closed impeller, 260
Coagulation, 59
Coliform group bacteria test, 409
Collecting data, lab, 350

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612 Treatment Plants
Collection of samples, 199
Collection system, 13, 212, 223
Collection systems, safety, 212, 223
Combustible gas indicator, 211
Comminution, safety, 216
Completely mixed system, activated sludge, 50, 75, 77
Composite sample, 190, 359, 360
Condensate drain, 102, 105, 108, 117, 119, 149
Condenser, 343
Conditioning sludge, 166
Conductivity, 453
Cone, Imhoff, 343, 366
Confined spaces, 157, 210, 212, 214, 215,219, 221, 308, 365
Coning, 137
Connecting rods, 283, 284
Constant differential flow meter, 313, 316
Contact stabilization, activated sludge, 50, 72, 73
Contract service, flow meters, 318
Controllers, flow, 316, 317
Controls, level, 269, 276
Conventional activated sludge, 16, 19, 43, 46, 47, 57, 62, 72,
75
Conversion instruments, 318
Conversion units, 509
also see Metric conversion factors
Corbels, 103, 132, 133
Coring, 137
Corrosion, 364, 366, 455
Corrosive chemicals, 354
Costs
aerobic digestion, 160
anaerobic digestion, 160
preventive maintenance, 245
records, 551
repair, 245
safety, 230
unplugging pipelines, 311
Couplings, 254, 265, 270, 293, 294
Covers, anaerobic digester, 103, 132
Cross connections, 227, 276
Cross multiplication, 480
Crucible, Gooch, 345
Crucible, porcelain, 345
Cube root, 482
Cubes, 482
Cumulative curves, 536
Cuts, skin, 356
Cutting tools, plugged pipes, 312
Cuvette, 349
Cyclone grit separators
see Volume I, Chapter 4
Cylinder, 484, 485
Cylinders, graduated, 340, 346
D
DO, 196
DO meter, 345
DO profile, 196, 198
DO test, 363, 424
Daily records, 551, 563
Dark foam, activated sludge, 49, 60
Data analysis and presentation
arithmetic mean, 520
average, 520, 528
bar graphs, 530
COD to BOD curves, 533
calculation of square root, 539
causes of data variations, 518
charts, 520, 530, 531, 533
electronic calculators, 524
geometric mean, 522
geometric mean table, 524
graphs, 530
importance, 518
log probability paper, 522
logarithms, 523
mean, 520
median, 521
metric calculations, 539
mode, 521
moving averages, 528
preparation of charts, 533
range of values, 521
square root, 539
trend charts, 531
variance, 533
variations in data, causes, 518
Dateometer, 287
Dechlorination
see Volume I, Chapter 10
Decibel, 22
Decimal fractions, 479
Decimals, 475
Deep well injections, 187
Dehumidifiers, 308
Denitrification, 60
Denominator, 478
Desiccator, 343
Detention time, 499, 501, 503, 506, 507, 508, 509
Dewatering sludge, 98, 164
Dial indicators, alignment, 293, 294
Dial thermometer, 343
Diaphragm bulb, level measurement, 269
Diaphragm flow meter, 313, 315, 316
Differential head flow meter, 313, 315, 316
Diffuser, activated sludge, 18, 20, 28, 35, 40, 64, 66, 71
Digested sludge handling
also see Volume III, Chapter 22,
Solids Handling and Disposal
aerobic digester, 161
anaerobic digester, 98, 161
blacktop drying beds, 164, 165
centrifuge, 166, 169
disposal on land, 164
drying beds, 161, 162, 163, 164, 165
lagoons, 164
land disposal, 164
mechanical dewatering, 164, 166
sludge drying beds, 161, 162, 163, 164, 165
sludge lagoons, 164
unplugging pipelines, 311
vacuum filters, 166, 167, 168
withdrawal to land, 164
Digested sludge pumps, 250
Digester cleaning, maintenance, 155
Digester control tests, 383
Digester explosion, 109, 112
Digester heating
boiler temperatures, 117
circulation, 117
heat exchanger, 117, 127, 128
methods, 117
steam, 117, 129
Digester mixing
draft tube propeller mixers, 129, 131
gas mixing, 129
maintenance, 132
mechanical mixing, 129, 130, 131

-------
propeller mixers, 129, 130, 131
pumps, 132
purpose, 98, 129
scum blanket, 132
Digestion
aerobic, 159, 160, 161
anaerobic, 98
equipment safety, 219
Digital receivers, 317
Dilution, 187
Dilution water, 410
Dimensional analysis, 475, 476, 498
Direct reuse, effluent, 187
Discharge permits, 54, 187
Discharge, pump, 251, 270, 271, 272, 274, 285
Dish, evaporating, 345
Dish, Petri, 343
Disinfection
See Volume I, Chapter 10
Displacement flow meter, 313, 315, 316
Disposal
effluent, 187
sludge, 98
solids, 98
supernatant, 145
Dissolved air flotation
also see Volume III, Chapters 22, and 28
sludge, 138
Dissolved oxygen
measurement, 424
meter, 345
saturation, 502, 506, 508, 509
test, 363, 424
test in aerator, 379
Dissolved solids, in wastewater, test, 453
Distilling flask, 341
Dividend, 477
Division, 477
Divisor, 477
Dogs, 36
Domestic wastewater, characteristics
see Wastewater characteristics
Drain of pump, 273, 283
Drain pumps, 269
Drinking water, 189, 308
Drip traps, 108, 117, 118, 119, 149, 221
Drum filter, 355
Drying beds, 161, 164
Drying, sludge, 161, 164
Dumps, industrial, 13
Dysentery, 209, 353, 355
E
Ear protecting devices, 210
Earthquakes, 558
Eccentric
pipe, 254
pump, 283
Effective writing, 554
Efficiency
formulas, 508, 509
problems, 502, 507
process, activated sludge, 13, 51, 53
pump, 278, 493
treatment, 187
wire to water, 494
Effluent disposal by dilution
also see Volume III, Chapter 25
Wastewater Reclamation
Index 613
control, 190
disposal requirements, 187, 188
effluent sampling, 191
emergency procedures, 191
frequency of sampling, 200
importance, 187
labeling of samples, 200
maintenance, 200
mixing, 196, 197
monitoring, 191
objectives, 185
operating procedures, 191
operational strategy, 191
power outage, 191
receiving water monitoring, 191
review of plans and specifications, 201
safety, 200
sampling and analysis, 199
shutdown, 191
size of sample, 200
start-up, 191
stream survey, 191
temperature, 193
treatment requirements, 187
troubleshooting, 191, 192, 193
visual observation, 190, 191
water quality survey, 191
Effluent pumps, 250
Ejectors, 285
Electric motors, 256, 269, 287, 288, 289
Electrical controls, 269
Electrical safety, 210
Electrical shock, 356
Electrode switches, 269, 285
Electronic calculators, 524
Elevated temperature test, 419
Elutriation, sludge, 166
Emergency planning, 558
Emergency procedures
activated sludge, 54
CHEMTREC, 249
phone (800) 424-9300
chlorinators, 249
disasters, 249, 319
effluent disposal, 191
planning, 230, 319, 558
storage lagoons, 190
Emergency team, 249
Energy
activated sludge, 15
aerobic digestion, 159, 160
anaerobic sludge digestion, 107, 139, 160
general, 107, 139, 160
Energy losses (friction), 495
Energy requirements
aerobic digestion, 160
pumps, 270
Enzymes, 139, 141
Equipment records, 245
Equipment sevice card, 245, 246
Erlenmeyer flask, 341
Errors, sampling, 359
Estuary, 187
Evaluation of records, 553
Evaporating dish, 345
Excavations, 214
Explosimeter, 223
Explosion, 109, 112
Explosive gases, 109, 112, 210, 223, 364

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614 Treatment Plants
Explosive materials, 354
Extended aeration
activated sludge, 19, 49, 60, 62
aerobic digestion, 160
F
F/M ratio, 15, 19, 59, 60, 62
Face shield, 222, 354
Facultative bacteria, 409
Fecal coliform test, 419, 422
Feeding anaerobic digesters, 101, 135, 137
Feeler gage, alignment, 254, 293
Figures, sigificant, 498
Filamentous growth, 50, 51, 53, 59, 60, 75
Filter press
see Volume III, Chapter 22
Filtering flask, 341
Financial records, 551
Fire, 210, 226, 357, 558
Fire blanket, 357
Fire control, safety, 226, 227
Fire extinguishers, 215, 227, 308, 357
Fire drills, 230
First aid kit, 229, 308, 356
Fish, 189, 195
Fixed-cover digesters, 103, 104, 132
Fixed sample, 200
Flame polished, 225, 356
Flame trap, anaerobic digester, 102, 105, 108, 109, 113, 114,
115,116,221
Flammable materials, 354
Flasks, 341, 348
Float control, 269
Float mechanism, level measurement, 276
Float switches, 285
Floating cover, anaerobic digester
access hatches, 133, 134
advantages, 103
annular space, 132, 133
ballast blocks, 132, 133
blocks, 132, 133
corbels, 132, 133
corrosion, 150
cover indicators, 133, 134
description, 103
flotation chamber, 132, 133, 150
gas piping, 133, 134
parts, 132
purpose, 132
roller guides, 132, 133
safety, 134
skirts, 133, 134
types, 132
Floating sludge, aerobic digesters, 161
Flocculation, 59
Floods, 558
Flow diagram
activated sludge, 14
anaerobic sludge digestion, 99
Flow formula, 312
Flow measurement, 312
Flow meters
accuracy, 313
calibration, 318, 493
chart, recording, 316, 317, 318
Cipoletti weir, 313, 316
constant differential, 313, 316
contract service, 318
controllers, 315, 316
conversion instruments and controls, 315, 316
diaphragm, 313, 315, 316
differential head, 313, 315, 316
displacement, 313, 315, 316
flow formula, 312
flow measurement, 312, 313, 314, 315
flow nozzles, 313, 315, 316
flumes, 313, 314, 315, 316
gases, 313, 315, 316
general, 190, 312, 313, 314, 315, 316
good housekeeping, 316, 318
head area, 313, 314, 315, 316
importance, 313
indicating receiver, 316
level measurement, 269
liquids, 313, 314, 315, 316
location, 315
magnetic, 313, 315, 316
magnetic flow transmitter, 316
maintenance, 312, 316
maintenance contract service, 318
manufacturer responsibility, 318
mechanical, 315
multipurpose receiver, 316
nozzles, 313, 316
operator responsibility, 313
orifice, 313, 315, 316
Palmer-Bowlus flume, 313, 314, 316
Parshall flume, 313, 315, 316
pen, recorder, 316
performance, 318
piston, 313, 315, 316
propeller, 313, 315, 316
proportional weir, 313, 316
rate, flow, 489
readout instruments and controls, 315, 318
receivers, 315, 316, 318
recorders, 315, 317, 318
recording pen, 316
recording receiver, 316, 317
rectangular weir, 313, 314, 316
responsibility, 313, 318
rotameter, 314, 316
sensors, 316, 318
shuntflow, 315, 316, 317
summators, 315, 316, 317
totalizers, 315, 316, 317
totalizing receiver, 316, 317
transmitters, 315
troubleshooting, 319
types, 313
use, 312
V-notch weir, 313, 315, 316
velocity meter, 313, 315, 316
weirs, 313, 314, 316
Flow nozzles, 313, 315, 316
Flow proportioning, sampling, 190, 359, 360
Flow rate, 489
Flumes, 313, 314, 315, 316
Foam control
activated sludge, 38, 43, 60
anaerobic digestion, 139
surface-active agents, 224
Foaming
anaerobic digestion, 136, 139
safety hazard, 224
Food/Microorganism ratio, 15, 19, 59, 60, 62
Food, activated sludge, 15, 19, 59, 60, 62
Food, anaerobic digester, 101, 135, 137

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Index 615
Foot valves, 278
Force (hydraulic), 488
Formazin turbidity units, 457
Formulas (English System)
activated sludge, 507
area, 507
chemical, 339
chlorination, 508
clarifiers, 507
detention time, 499, 501, 507, 508
dissolved oxygen saturation, 502, 508
efficiency, 508
hydraulic loading, 500, 502, 507, 508
laboratory results, 508
organic loading, 500, 502, 507, 508
ponds, 508
population loading, 502, 508
pumps, 508
sedimentation, 507
sludge digestion, 508
surface loading rate, 499, 507
trickling filters, 507
velocity, 507
volatile acid/alkalinity, 501
volume, 507
weir overflow rate, 500, 507
weirs, 507
Formulas (Metric System)
activated sludge, 509
area, 508
chemical, 339
chlorination, 509
clarifiers, 508
detention time, 503, 506, 509
dissolved oxygen saturation, 506, 509
efficiency, 509
hydraulic loading, 504, 506, 509
laboratory results, 509
organic loading, 504, 506, 509
ponds, 509
population loading, 506, 509
pumps, 509
sedimentation, 508
sludge digestion, 509
surface loading, 504, 508
trickling filters, 509
velocity, 508
volatile acid/alkalinity, 505
volume, 508
weir overflow, 504, 509
weirs, 508
Fractions, 478
Frequency of records, 551
Friction losses, 495
Fuels, safety, 223
Fume hood, 345
Funnels, 342
Fuses, 270
G
Gage reading, 519
Gas
digester, 139, 142, 145
meters, 108, 117
system, 107, 108, 109, 117
use, 107
Gas analysis, anaerobic digester, 389
Gas detection, 211, 308
Gas meters, 117, 313, 315, 316
Gas piping, 102, 105, 107, 108
Gas pressure-volume problems, 481
Gas production, anaerobic digestion, 139
condensate traps, 108, 117
dome, 107
drip traps, 108, 117
flame arresters, 108, 109
gas meters, 108, 117
manometers, 117
piping, 134
pressure regulators, 108, 117
pressure relief valves, 108, 109
sediment traps, 108, 117
thermal valves, 109
traps, 108, 117
troubleshooting, 154
use of gas, 107
vacuum relief valves, 108, 109
valves, 108, 109, 150
waste gas burner, 108, 117, 124
Gases
anaerobic digestion, 107, 136, 143, 144, 160
characteristics, 211
explosive, 109, 112, 210
explosive range, 211
safe exposure, 211
toxic, 210, 211, 223, 226
Gasket, pump, 283
Gasoline vapors, 210
Gate valves, 296, 297, 298, 299
Gear reducer, 283
Geiger counter, 210
Generators, 319
Geometric mean, 522
Geometric mean table, 524
Gland
pump, 255, 270, 272
valve, 299
Glossary of terms, 577
Gooch crucible, 345
Good housekeeping
management responsibilities, 209, 230
safety, 215, 216, 219, 223, 354.
sensors, 316, 318
Grab sample, 190, 360
Graduated cylinders, 340, 346
Graphs, 530, 531
Grease, test, 363, 445
Greasing, pump, 285
Green sludge, 163
Grit, channels, 219
also see Volume I, Chapter 4
problems (arithmetic), 499, 503
Grit, pumps, 250
Grounds, maintenance, 248
Groundwater recharge, wastewater, 187
H
Harness, safety, 212
Hazardous spills, 558
Hazards
see Safety hazards
Head area, flow meter, 313, 314, 315, 316
Head (hydraulics), 488, 491
Headworks, 215
Health, 187
Heat exchanger, anaerobic digester, 117, 127, 128, 149, 154
155, 219, 221
Heat value of gas, 107

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616 Treatment Plants
Heating, anaerobic digester, 117, 127, 128
Heavy metals, test, 433
Hepatitis, 209, 353, 355
High rate, activated sludge, 19, 47, 62, 75, 78
High velocity pressure units, 312
Hood, fume, 345
Horsepower, 491
Hot plate, 343
Housekeeping
management responsibilities, 209, 230
safety, 215, 216, 219, 223, 354
sensors, 316, 318
Hydraulic loading, 500, 502, 504, 506, 507, 508, 509
Hydraulics
energy losses, 495
flow rate, 489
force, 488
friction losses, 495, 496, 497
head, 488, 491
horsepower, 491
pipe friction losses, 495, 496, 497
power, 491
pressure, 488
pump characteristics, 492
pump performance, 493
pump speed, 494
pumps, 490
valve friction losses, 495, 496, 497
velocity, 489
weight-volume relations, 488
work, 491
Hydrogen ion (pH), 432
Hydrogen peroxide, odor control
see Volume III, Chapter 20
Hydrogen sulfide (H2S)
analyzer, 211
digester gas, 157
safety hazard, 100, 157, 210, 215, 216, 219, 223, 354, 364,
455
tests, 363, 364
Hygiene, safety considerations, 354
Hypochlorination
See Volume I, Chapter 10
I
Identification of problem, 495
Imhoff cone, 343, 366
Impact of discharges, 190, 193
Impellers, 250, 251, 253, 257, 258, 259, 260, 263, 270, 272,
273, 278
Importance of data analysis and presentation, 518
Importance of record keeping, 550
Importance of record writing, 553
Improper fractions, 478
Incline screw pumps, 257, 265
Incubator, BOD, 346
Indicating receiver, 316
Indirect reuse, effluent, 187
Industrial spills, 13, 51, 53
Industrial waste treatment, activated sludge, 13,51,54,58,75
Industrial waste treatment, safety, 223
Industrial wastes, BOD, test, 431
Infections, 209, 353
Infectious diseases, 209
Infiltration-percolation basins, 187
Inflammable materials, 354
Inoculation, 129, 353
Inspecting new facilities
activated sludge, 36
aeration tank, 36
air filters, 38
air headers, 40
air mains, 40
air system, 38
anaerobic digesters, 102, 107, 117, 129
blowers, 39, 41
compressors, 39
control gates, 36
corrosion protection, 38
diffusers, 40
metering devices, 40
movable gates, 38
orifice plate, 40
pumps, 41
return sludge pumps, 41
rust protection, 38
secondary clarifiers, 41
waste sludge pumps, 41
water sprays, 38
weirs, 38
Inspection of facilities, 247
Inventory, records, 551
Ionization chamber, 210
Irrigation
wastewater, 187
water quality criteria, 189
J
Jackson Turbidity Units, 457
Joule, 107
K
Kjeldahl flask, 341
Kraus process, activated sludge, 59, 72, 74
L
LAS, 455
Labels
chemicals, 225
samples, 200
Laboratory apparatus, for tests
acidity, 398
activated sludge control tests, 377
alkalinity, total, 387, 399
ammonia, 433
biochemical oxygen demand (BOD), 427
carbon dioxide (C02), 389
chemical oxygen demand (COD), 401
chloride, 403
chlorine residual, total, 405
clarity, 364
coliform group bacteria, 409
digester control tests, 383
dissolved oxygen (DO), 424
dissolved oxygen in aerator, 379
grease, 445
hydrogen ion (pH), 432
hydrogen sulfide (H2S), 365
lime analysis, 395
MPN method, 409
mean cell residence time, 382
membrane filter method, 419
metals, 433
nitrogen, 433
ammonia, 433
nitrate, 438
nitrate and nitrite, 441
nitrite, 438

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Index 617
organic nitrogen, 438
total Kjeldahl nitrogen (TKN), 436
oil and grease, 445
pH,432
phosphorus, 447
plant control tests, 364
settleability, 377
settleable solids, 366
sludge age, 379
sludge (digested) dewatering characteristics, 391
sludge density index (SDI), 378
sludge solids (volatile and fixed), 371
sludge volume index (SVI), 378
solids, total (residue), 451
specific conductance, 453
sulfate, 455
supernatant, 394
surfactants, 455
suspended solids, 368
suspended solids in aerator, 380
temperature, 395, 455
total organic carbon (TOC), 456
turbidity, 456
volatile acids, 383
Laboratory equipment
analytical balance, 346
BOD bottle, 342
BOD incubator, 346
balance, analytical, 346
beakers, 340, 348
boiling flask, 341
bottle, BOD, 342
bottle, reagent, 342
breathing apparatus, self-contained, 222, 357
Buchner funnel, 342
Bunsen burner, 344
burets, 341, 346
burner, Bunsen, 344
carbon analyzer, 456
clamps, 341, 344
condenser, 343
cone, Imhoff, 343
crucible, Gooch, 345
crucible, porcelain, 345
cuvette, 349
cylinders, graduated, 340, 346
DO meter, 345
desiccator, 343
dial thermometer, 343
dish, evaporating, 345
dish, Petri, 343
dissolved oxygen meter, 345
distilling flask, 341
drum tilter, 355
Erlenmeyer flask, 341
evaporating dish, 345
face shield, 222, 354
filtering flask, 341
fire blanket, 357
fire extinguisher, 357
first aid kit, 356
flasks, 341, 348
fume hood, 345
funnels, 342
gloves, 354
Gooch crucible, 345
graduated cylinders, 340, 346
hood, fume, 345
hot plate, 343
Imhoff cone, 343
incubator, BOD, 346
Kjeldahl flask, 341
lab coat, 354
Mallory settlometer, 44, 377
Mohr pipets, 348
muffle furnace, electric, 343
Nessler tubes, 342
oven, mechanical convection, 343
Petri dish, 343
pH meter, 345
pH paper, 345
pipets, 340, 348
porcelain crucible, 345
protective clothing, 355
pump, air pressure & vacuum, 345
reagent bottle, 342
safety glasses, 354
safety tongs, 344
self-contained breathing apparatus, 222, 357
separatory funnel, 342
serological pipets, 340, 348
settlometer, Mallory, 44, 377
test tubes, 342
thermometer, 343
tongs, safety, 344
triangle, lab, 344
tripod, lab, 344
use of lab glassware, 348
vacuum pump, 345
volumetric flask, 341, 348
volumetric pipets, 340, 348
Laboratory, general
absorbance, 349
Beer's Law, 349
bench sheets, 350
blank, 349
calibration curves, 349
chemical formulas, 339
chemical names, 335, 339
collecting data, 350
importance, 333
laboratory work sheets, 350
metric system, 339
normality, 348
notebooks, 350
objectives, 332
procedures, 327
quality control, 361, 518, 535
recording data, 350
safety rules, 354
sampling, 359
solutions, 348
spectrophotometer, 348
standard solution, 348, 349
storage, 355
techniques, 356
terms, 335
titrations, 348
transmittance, percent, 349
use of lab glassware, 346
work sheets, 350
Laboratory glassware
BOD bottle, 342
beakers, 340, 348
boiling flask, 341
bottle, BOD, 342
bottle, reagent, 342
Buchner funnel, 342

-------
618 Treatment Plants
condenser, 343
cone, Imhoff, 343
crucible, Gooch, 345
crucible, porcelain, 345
cylinders, graduated, 340, 346
desiccator, 343
dish, evaporating, 345
dish, Petri, 343
distilling flask, 341
Erlenmeyer flask, 341, 348
evaporating dish, 345
filtering flask, 341
flasks, 341, 348
funnels, 342
Gooch crucible, 345
graduated cylinders, 340, 346
Imhoff cone, 343
Kjeldahl flask, 341
Mohr pipets, 348
Nessler tubes, 342
Petri dish, 343
pipets, 340, 348
porcelain crucible, 345
reagent bottle, 342
separotory funnel, 342
serological pipets, 340, 348
test tubes, 342
use of lab glassware, 348
volumetric flask, 341, 348
volumetric pipets, 340, 348
Laboratory hazards
acids, 354
bases, 354
burns, 356
carbon tetrachloride, 290, 354
chemicals, 354
corrosive chemicals, 354
cuts, 356
dysentery, 353
electrical shock, 356
explosive materials, 354
fire, 357
flammable materials, 354
hepatitis, 353
hydrogen sulfide, 100, 157, 210, 215, 216, 219, 223, 354
infectious materials, 353
inflammable materials, 354
mercury, 210, 356
tetanus, 353
toxic fumes, 356
toxic materials, 354
typhoid, 353
waste disposal, 357
Laboratory precautions, running tests
alkalinity, 400
ammonia, 434
biochemical oxygen demand (BOD), 429, 431
carbon dioxide, 390
chemical oxygen demand, 403
chloride, 405
dissolved oxygen (DO), 424, 426
hydrogen ion (pH), 433
lime analysis, 397
membrane filter, 422
nitrogen, ammonia, 433
pH, 433
suspended solids, 368
suspended solids, centrifuge, 382
turbidity, 456, 457
volatile acids, 385
Laboratory procedures
acidity, 363, 398
activated sludge control tests, 377
alkalinity, total, 363, 387, 399
ammonia, 353, 433
biochemical oxygen demand (BOD), 363, 427
biochemical oxygen demand, chlorinated samples, 429
biochemical oxygen demand, industrial wastes, 431
carbon dioxide (C02), 389
chemical oxygen demand (COD), 363, 401
chloride, 353, 403
chlorine residual, total, 353, 405
clarity, 364
coliform group bacteria, 409
digester control tests, 383
dissolved oxygen (DO), 363, 424
dissolved oxygen in aerator, 379
fecal coliform bacteria, 419, 422
grease, 353, 445
hydrogen ion (pH), 432
hydrogen sulfide (H2S), 363, 364
lime analysis, 395
MPN method, 409
mean cell residence time, 382
membrane filter method, 419
metals, 433
most probable number (MPN), 409
multiple tube fermentation, 409
nitrogen, 433
ammonia, 363, 433
nitrate, 363, 438
nitrate and nitrite, 363, 441
nitrite, 363, 438
organic nitrogen, 438
total Kjeldahl nitrogen (TKN), 363, 436
oil and grease, 363, 445
pH, 363, 432
phosphorus, 363, 447
plant control tests, 364
settleability, 377
settleable solids, 366
sludge age, 378
sludge (digested) dewatering characteristics, 391
sludge density index (SDI), 378
sludge solids (volatile and fixed), 371
sludge volume index (SVI), 378
solids, total (residue), 363, 451
specific conductance, 363, 453
sulfate, 363, 455
supernatant, 394
surfactants, 455
suspended solids, 367
suspended solids in aerator, 380
temperature, 363, 395, 455
total organic carbon (TOC), 363, 456
turbidity, 363, 456
volatile acids, 383
Laboratory reagents
acidity, 398
activated sludge control tests, 377
alkalinity, total 387, 399
ammonia, 433
biochemical oxygen demand (BOD), 427
carbon dioxide (C02), 389
chemical oxygen demand (COD), 401
chloride, 403
chlorine residual, total, 405
coliform group bacteria, 409

-------
Index 619
digester control tests, 383
dissolved oxygen (DO), 424
dissolved oxygen in aerator, 379
grease, 445
hydrogen ion (pH), 432
hydrogen sulfide (H2S), 365
lime analysis, 395
MPN method, 409
mean cell residence time, 382
membrane filter method, 419
metals, 433
nitrogen, 433
ammonia, 433
nitrate, 438
nitrate and nitrite, 441
nitrite, 438
organic nitrogen, 438
total Kjeldahl nitrogen (TKN), 436
oil and grease, 445
pH, 432
phosphorus, 447
plant control tests, 364
sulfate, 455
total organic carbon (TOC), 456
turbidity, 456
volatile acids, 383
Laboratory records, 350
Laboratory results
activated sludge, 16
anaerobic digestion, 101, 142, 155
formulas, 508, 509
problems (arithmetic), 502, 506
supernatant, 145
Laboratory safety
accident prevention, 356
burns, 356
chemical storage, 355
chemicals, 354
corrosive chemicals, 354
cuts, 356
dysentery, 353
electrical shock, 356
explosive materials, 354
face shield, 222, 354
fire, 357
flammable materials, 354
gloves, 354
good housekeeping, 354
hazards, 353
hepatitis, 353
infectious materials, 353
inflammable materials, 354
movement of chemicals, 355
personal hygiene, 354
rules, 354
safety glasses, 354
storage, 355
techniques, 356
tetanus, 209, 353, 354
toxic fumes, 356
toxic materials, 354
typhoid, 353
waste disposal, 357
Lagoons
also see Volume I, Chapter 9
safety, 222
sludge, 145, 164
Land disposal
effluent, 187
precautions, 164
sludge, 164
Landfill, sludge, disposal, 164
Landscaping, 248
Lantern ring, 278, 279
Lead acetate, 365
Least common denominator, 478
Legal action, 550, 551
Let's Build a Pump, 253
Library, plant, 249
Life line, 212
Lift stations, 215, 319
Lifting, safe practices, 212, 213
Lime, 138, 163
Lime analysis, 395
Liquid flow measurement, 313, 314, 315, 316
Living filter, 187
Loadings, anaerobic sludge digestion, 145, 148, 153, 154
Location of sampling, 104, 197, 199, 359
Lock-out tag, 216, 217, 218, 277
Log book, records, 551
Log probability paper, 522
Logarithms, 523
Lubrication, 254, 269, 270, 278, 285, 287, 289, 291
M
MCRT, 15, 62, 63, 382
MLSS, 19, 44, 50, 57, 58, 59, 60, 62, 75
MLVSS, 19, 50, 58, 62
MPN test, 409, 414
Magnetic flow meters, 313, 315, 316
Magnetic flow transmitter, 316
Maintenance
activated sludge, 61, 63, 66
aerobic digestion, 161
air distribution system, 71
air filters, 66
air headers, 64, 71
anaerobic digesters, 101,102,109,117,132,148,149,150,
169
blacktop drying beds, 164
blowers, 22, 28, 64, 70
diffusers, 64, 71
effluent disposal, 187
flow meters, 312
records, 551
seizing, 68, 70
shutdown procedures, 64
sludge drying beds, 163
surface aerators, 35, 64, 66
valves, 149
Maintenance contracts, flow meters, 318
Maintenance program, pumps, 276
Maintenance reports, 551
Maintenance, sensors, 316
Mallory settlometer, 44, 377
Manhole hooks, 212
Manholes, 212
Manometer reading, 519
Mean, 482, 520
Mean cell residence time, 15, 62, 63
Mean cell residence time, test, 382
Measurement of gases, 211
Measurements
in-plant, 187
process control, 190
receiving water, 190
Mechanical aeration, 16, 17, 21, 28, 35, 64, 65, 66
Mechanical dewatering, 161, 164

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620 Treatment Plants
Mechanical equipment
also see Mechanical maintenance, Meter maintenance
and Volume III, Chapter 26, Instrumentation,
and Chapter 29, Support Systems
axial flow pumps, 257, 263
centrifugal pumps, 250, 257, 258, 259
chlorinators, 248
electric motors, 269, 287, 288, 289
electrical controls, 269
incline screw pumps, 257, 265
lubrication, 254
multi-stage pumps, 257, 264
operation, 269, 270
piston pumps, 257, 284
pneumatic ejectors, 257
positive-displacement pump, 257, 284
progressive cavity pumps, 257, 266, 267
propeller pumps, 257, 262, 263, 285
pump-driving equipment, 269
radial flow pumps, 257, 263
reciprocating pumps, 257, 264
repair shop, 250
screw-flow pumps, 257, 266, 267
shutdown, 269, 270, 274
single-stage pumps, 257, 264
sludge pump, 257, 284
start-up, 269, 270, 274
submersible pump, 257, 261
troubleshooting, 269, 270
turbine pumps, 257, 264
vertical wet well pump, 257, 264
wet well pump, 257, 261, 264
Mechanical maintenance
air chamber, 283, 284
air-gap separation systems, 308
alignment, 278
ball valves, 283, 284
bearings, 278, 285, 287
belt drives, 270, 290, 291, 292
capacity, pump, 278
centrifugal pumps, 270, 276
chain drives, 290
change oil, 283, 291
check valves, 285, 299, 300
cleaning pump, 276
connecting rods, 283, 284
controls, 276
conversion instruments, 318
couplings, 270, 293, 294
dehumidifiers, 308
draining pump, 273, 283
eccentric, 283, 284
efficiency, pump, 278
ejectors, 285
electric motors, 287
electrode switches, 285
equipment service card, 245, 246
float switches, 276, 285
flow meters, 312
frequency of service, 245
gaskets, 283
gate valves, 296, 297, 298, 299
gear, reducer, 283
greasing, 285
impeller, 278
lantern ring, 278, 279
lubrication, 257, 269, 270, 278, 285, 287, 289, 291
mechanical seals, 278
noises, 283, 287, 291
oil change, 283, 291
packing, 270, 276, 278, 279, 280, 281, 282, 283, 284
piston pumps, 283, 284
plug valves, 299, 301, 302, 303, 304, 305
plunger pumps, 283, 284
pneumatic ejectors, 285
positive displacement pumps, 283, 284
preventive maintenance, 276
progressive cavity pumps, 285
propeller pumps, 285
pumps, general, 276
readout instruments, 318
reciprocating pumps, 283, 284
reducer, gear, 283
rings, pump, 278
rods, 284
safety equipment, 308
seals, 276, 278, 279
sensors, 316
service record card, 245, 246
shear pins, 283, 295
sludge pump, 283, 284
sluice gates, 299, 306, 307
stuffing box, 278
switches, 269, 276, 285
TDH, 278
total dynamic head, 278
troubleshooting, 269, 270, 291
valve-chamber gasket, 283, 284
valves, 278, 283, 284, 296, 299
variable speed belt drives, 291
vibrations, 272, 273, 287
water seal, 278, 279
wearing rings, 278
Mechanical mixing, 129, 130, 131
Mechanical seals, 278
Mechnics of writing, 554
Median, 482, 521
Membrane filter test, 419
Meniscus, 346, 519
Mercury, 210, 356
Mesophilic bacteria, 101, 142
Metals, test, 363, 433
Meter maintenance, 312, 316, 318
Metering devices, 190
Methane fermenters, 98
Methane gas, 98, 107, 136, 143, 160, 210, 219, 383
Metric conversion factors
activated sludge, 79
aerobic digestion, 170
anaerobic digestion, 170
chemistry, 339
conversion tables, 509
laboratory, 339
Metric problem solutions
activated sludge, 79
aerobic digestion, 170
anaerobic digestion, 170
arithmetic, 486
calculations, 539
Metric system
capacity, 486
concentration, 487
formulas, 508
length, 486
problems, 487, 503
pumps, 509
temperature, 487
volume, 486

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Index 621
weight, 486
Mixing
aerobic digestion, 160, 161
anaerobic digestion, 98, 130, 131, 139, 153, 154, 155
Mode, 521
Modified aeration, activated sludge, 75
Mohr pipets, 348
Monitoring programs
effluent sampling, 191
stream survey, 191
water quality survey, 191
Monthly records, 552
Monthly reports, 555, 557
Most probable number (MPN) test, 409
Motor, pump, 273
Movement of chemicals, 355
Moving averages, 528
Muffle furnace, electric, 343
Multiple hearth furnace
also see Volume III, Chapter 22
sludge, 141
Multiplication, 476
Multipurpose receiver, 316
Multi-stage pumps, 257, 264
N
NPDES permits, 54, 191, 550, 552
Nanometer, 438
Naphtha, 223
National Pollutant Discharge Elimination System permits, 54,
191, 550, 552
Natural gas, 210
Nephelometry, 456
Nessler tubes, 342
Neutralizing, 138, 153
Neutralizing a sour digester, 138
Nitrogen
fertilizer, 187
requirements, 59, 72, 75
test in wastewater, 363, 433
valve, 187
Nitrogen removal, 160
Nitrogen test, 363, 433
ammonia, 363, 433
nitrate, 363, 438
nitrate and nitrite, 363, 441
total Kjeldahl nitrogen (TKN), 363, 436
Noise, safety, 210
Noisy chain drive, 291
Noisy electric motor, 287
Noisy pump, 270, 283
Nonsparking tools, 219
Normal distribution of data, 532
Normality, 348
Notebooks, laboratory, 350
Nozzles, flow measurement, 313, 316
Nuclear accidents or attacks, 558
Numerator, 478
Nutrient removal
See Volume III
Nutrients, 59, 72, 75, 187
O
O & M manual, 249, 551
OSHA, 353
Objectives
activated sludge, 6
anaerobic digestion, 95, 98
analysis of data, 517
chemistry, 332
data analysis and presentation, 517
effluent disposal, 187
laboratory, 332
maintenance, 243
presentation of data, 517
receiving water monitoring, 191
records, 549
report writing, 549
safety, 208
sampling, 359
Occupational Safety and Health Act (OSHA), 353
Odors
activated sludge, 15, 60
aerobic digestion, 159, 160, 161
anaerobic digestion, 139, 149, 157
effluent disposal, 190
hydrogen sulfide, 366
odorous air, 22
receiving waters, 187, 190
sludge drying beds, 163
sulfate, 455
Odor control
see Volume III, Chapter 20
Oil and grease test, 363, 445
Oil change, pump, 283
Open impeller, 260
Operation
activated sludge, 13, 46, 49, 50, 63
aerobic digestion, 161
anaerobic digesters, 135, 142, 148, 153
blacktop drying beds, 164
digesters, 135, 142, 148, 153
effluent disposal, 191
pumps, 269, 270
records, 550
sludge drying beds, 163
temperature effect, 46, 58
Operation and maintenance manuals, 249, 551
Operational problems
see Troubleshooting
Operational strategy
activated sludge, 49, 50, 51
anaerobic digestion, 148
effluent disposal, 191
Operators' reports, 556
Organic loading, 550, 502, 504, 506, 507, 508, 509
Organizing for writing reports, 554
Orifice, 313, 315, 316
Oven, mechanical convection, 343
Oxidation ditch
see Volume I, Chapter 8
Oxygen profile, 196, 198
Oxygen activated sludge
see Volume III, Chapter 21
Oxygen deficiency, 210, 211
Ozone
See Volume I, Chapter 10, and
Volume III, Chapter 20
P
Package aeration plants
see Volume I, Chapter 8
Packing, 266, 270,274, 276, 278, 279, 280, 281, 282, 283, 284
Paint, buildings and equipment, 247
Palmer-Bowlus flume, 313, 314, 316
Parshall flume, 313, 315, 316, 520
Pen, recorder, 316
Percentage, 479

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622 Treatment Plants
Personal hygiene, 354
Personnel records, 551
Petri dish, 343
pH
meter, 345
paper, 345
safety, 224
test, 363, 432
pH control, anaerobic digester, 142
pH measurement, 432
Phosgene, 223
Phosphorus
also see Volume III, Chapter 24
concentration in wastewater, 447
fertilizer, 187
preservation of sample, 363
test in wastewater, 447
value, 187
Physical chemical treatment
see Volume III, Chapters 23 and 28
Physical injuries, 209
Physical plant records, 551
Pillows (reagent containers), 427
Pipe friction losses, 495, 496, 497
Pipets, 340, 348
Piping
gas collection and storage, 107
maintenance, 311
sludge, 102
Piston flow meter, 313, 315, 316
Piston pumps, 257, 274, 283, 284
Plans and specifications
anaerobic digestion, 169
effluent disposal, 201
electrical systems, 319
equipment, 319
lift stations, 319
pump stations, 319
safety, 231
Plant appearance, 248
Plant control tests, 364
Plant log book, 551
Plug flow, 360
Plug valves, 299, 301, 302, 303, 304, 305
Plunger pumps, 257, 274, 283, 284
Pneumatic ejectors, 257, 285
Policy, safety, 230
Polio virus, 355
Polyelectrolyte, 59
Ponds
also see Volume I, Chapter 9
formulas, 508, 509
problems (arithmetic), 501, 506
safety, 222
Population loading, 502, 506, 508, 509
Porcelain crucible, 345
Portable generators, 319
Positive displacement pumps
sludge, 257, 274, 283, 284
wastewater, 257, 274, 283, 284
Potable water, 227, 308
Power, 491
Power outage, 191, 558
Power, pump, 256, 274
Precautions, running lab tests
see Laboratory precautions, running tests
Preparation of charts, 533
Presentation of data
see Data analysis and presentation
Preserving samples, 361, 363
Pressure cleaning pipelines, 311
Pressure filters, sludge, 141
also see Volume III, Chapter 22 (Sludge) and
Chapter 23 (Solids in Effluents)
Pressure (hydraulic), 488
Pressure regulators, 108, 117, 120, 121, 123
Pressure relief valves, 102, 105, 108, 109, 110, 111,115, 116
Pressure swing system, oxygen activated sludge
see Volume III, Chapter 21
Pretreatment
see Volume I, Chapter 4
industrial wastes, see Volume III, Chapters 21, 27 and 28
Preventive maintenance, program, 276, 311
Preventive maintenance, records, 245, 551
Preventive maintenance, sensors, 316
Primary sedimentation
see Volume I, Chapter 5
Primary treatment
see Volume I, Chapter 5
Prime, centrifugal pump, 225, 269, 270, 273, 274
Principles of writing, 553
Prism, 485
Problem solving
arrangement of formula, 498
calculations, 498
check your results, 499
dimensions, 498
formulas (English System), 507
formulas (Metric System), 508
identification of problem, 495
selection of formula, 495
significant figures, 498
typical problem solutions (English System), 499
typical problem solutions (Metric System), 503
units, 475, 476, 498
Problems, metric, 487, 503
Process control
also see Operation and Operational strategy
tests, 190
Progressive cavity pumps, 257, 266, 267, 274, 285
Propeller flow meter, 313, 315, 316
Propeller pumps, 257, 262, 263, 285
Proportion, 480
Proportional sample, 190
Proportional weir, 313, 316
Protective clothing, 35, 210, 212, 222, 223, 225, 226, 230, 308
355
Protective coating, 223
Prussian blue, 296
Psychrophilic bacteria, 101
Public health, 187
Public relations
appearance of plant, 247, 248
management responsibility, 247, 248
Pump capacity, 256
Pumping stations, 215, 319
Pumps
air chamber, 283, 284
air pressure, 345
alignment, 254, 270, 293, 294
axial flow, 257, 263
ball valves, 283, 284
bearings, 250, 253, 258, 259, 265, 269, 273, 285
belts, 270, 290, 291
capacity, 256, 270
casing, 250, 254, 258, 259
cavitation, 256
centrifugal, 250, 253

-------
characteristics, 492
circuit breakers, 270
cleaning pump, 276
connecting rods, 283, 284
coupling, 254, 265, 270, 293, 294
cross connections, 276
description, 250
discharge, 251, 256, 270, 271, 272, 274, 285
drain, 273, 283
drain pumps, 269
driving equipment, 269
eccentric, 283
efficiency, 493
electric motors, 269
energy, 270
evaluation, 493
formulas, 508, 509
friction, 256
fuses, 270
gasket, 283
gear reducer, 283
general, 271, 276, 490
greasing, 285
head, 256, 491
horsepower, 491
impeller, 250, 251, 253, 257, 258, 259, 260, 263, 270, 272,
273
incline screw, 257, 265
lantern ring, 278, 279
Let's Build a Pump, 253
lubrication, 254, 257, 269, 270, 285
maintenance, 276
metric, 509
motor, 273
multi-stage, 257, 264
noisy, 270, 283
oil change, 283
operation, 269, 270
packing, 266, 270, 274, 276, 283, 284
performance, 493
plunger, 283, 284
pneumatic ejectors, 257, 285
positive displacement, 257, 274, 283, 284
power, 270, 274, 491
prime, 255, 269, 270, 273, 274
progressive cavity, 257, 266, 267, 274, 285
propeller, 257, 262, 263, 285
pump driving equipment, 269
radial flow, 257, 263
reciprocating, 257, 283, 284
reducer, gear, 283
repair shop, 250
rings, 255, 258, 270, 272, 273
rods, 284
rotation, 269, 270
rotor, 266, 274
screw-flow, 257, 266, 267
seal cage, 256
seals, 270, 272, 273
Shaft, 250, 253, 258, 259, 270
shear pin, 283
shutdown, 269, 270, 272, 273, 274
single-stage, 257, 264
sleeves, 253
sludge pump, 257, 283, 284
start up, 256, 269, 270, 272, 274
stator, 257, 266, 274
stuffing boxes, 255, 258
submersible pump, 257, 261
Index 623
suction, 251, 254, 256, 270, 271, 272, 274
troubleshooting, 269, 270
turbine pumps, 257, 264
vacuum, 345
valve-chamber gasket, 283, 284
vanes, 250
vertical wet well, 257, 261, 264
vibrations, 272, 273, 293
volute, 271, 272, 273, 274
wearing rings, 255, 258, 270, 272, 273
wet well pumps, 257, 261, 264
Pump parts
air chamber, 283, 284
ball valves, 283, 284
bearings, 250, 253, 257, 258, 259, 265, 269, 273
belts, 270, 290, 291
casing, 250, 254, 258, 259
connecting rods, 283, 284
coupling, 254, 265, 270, 293, 294
drain, 273
eccentric, 283
gasket, 283
gear, reducer, 283
gland, 255, 270, 274
impeller, 250, 251, 253, 257, 258, 259, 260, 263, 270, 272,
273
lantern ring, 278, 279
motor, 273
packing, 266, 270, 276, 283, 284
reducer, gear, 283
rings, 255, 258, 270
rods, 283, 284
rotor, 257, 266
seal cage, 256
seals, 270
shaft, 250, 253, 258, 259, 270
shear pin, 283, 295
sleeves, 253
stator, 257, 266
stuffing boxes, 255, 258
suction, 251, 254, 256, 270
valve-chamber gaskets, 283, 284
vanes, 250, 251
volute, 271, 272
wearing rings, 255, 258, 270
Purchase order, 551
Purchasing equipment and supplies, 551
Purpose of treatment process
activated sludge, 6, 20, 72
aeration, 20
aerobic sludge digestion, 98
anaerobic digestion, 95, 98
blacktop drying beds, 164
effluent disposal, 187
sludge drying beds, 161
Putrefaction, 160
Q
Quality control, laboratory, 361, 518, 535
Quotient, 477
R
Racks
see Volume I, Chapter 4
Radial flow pumps, 257, 263
Radiological hazards, 210
Range of values, 521
Ratio, 480
Raw sludge, 98, 135, 143, 149

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624 Treatment Plants
Raw sludge piping, 102
Raw sludge pumps, 250
Raw wastewater pumps, 250
Reading manometers and gages, 519
Readout instruments, 318
Reagent bottle, 342
Receiver mechanisms, 315, 316, 318
Receiving waters, 201
Recharge basins, 187
Reciprocating pumps, 257, 283, 284
Recirculation, anaerobic sludge digester, 143
Reclamation, wastewater, 187
Record keeping
activated sludge, 13, 15, 36, 50, 57
aerobic digestion, 161
anaerobic digestion, 101, 142, 150, 153, 155
cost records, 551
daily records, 551, 563
effluent disposal, 199
evaluation of records, 553
financial records, 551
frequency, 551
importance, 550
inventory, 551
laboratory, 350
legal action, 550, 551
log, 551
MPN test, 414
maintenance, 551
monthly records, 552
need, 550
operation, 550
personnel, 551
physical plant, 551
plant log book, 551
preventive maintenance, 245, 551
pumps, 41, 42, 245
stock inventory, 551
types of records, 550
Recorders, 315, 317, 318
Recording pen, 315
Recording receiver, 316, 317
Records of plant performance
see Record keeping
Recreation, 189
Rectangle, 483, 485
Rectangular weir, 313, 314, 316
Reducer, gear, 283
Reducing fractions, 478
Reflux, 402
Report forms, accident, 231
Report writing
annual reports, 556
effective writing, 554
importance of reports, 553
mechanics of writing, 554
monthly reports, 555, 557
NPDES, 54, 191, 550, 552
operators' reports, 556
organization, 554
principles of writing, 553
reports by other operators, 556
types of reports, 555
typical monthly report, 557
Reports
see Report writing
Reports by other operatives, 556
Representative sample, 195, 359, 518
Respiration, 196
Reuse, wastewater, 187
Review of plans and specifications
anaerobic digestion, 169
effluent disposal, 201
electrical systems, 319
equipment, 319
lift stations, 319
pump stations, 319
safety, 231
Rings, pump, 255, 258, 270, 272, 273, 278
Rising sludge, 60, 75
Rods, pump, 283, 284
Roots (arithmetic), 481, 482
Rotameter, 314, 316
Rotating biological contactors
see Volume I, Chapter 7
Rotation, pump, 269, 270
Rotor, 257, 266, 274, 289
Rounding off numbers, 477, 498
S
SDI
activated sludge, 50, 51, 53
test, 378
SI
see Metric
SVI
activated sludge, 50, 51, 53
test, 378
Safety equipment
air-gap device, 227, 228
air supply, 222
blowers, 210, 219, 308
breathing apparatus, self-contained, 222, 357
chlorine detector, 210
combustible gas indicator, 211
ear protecting devices, 210
explosimeter, 223
face shield, 222, 354
fans, 210, 219
fire extinguishers, 215, 227, 308
fire fighting equipment, 210, 227, 357
first aid kit, 229, 308, 356
gas testing, 211, 308
Geiger counter, 210
gloves, 354
hard hat, 212
harness, 212, 308
hydrogen sulfide analyzer, 211
ionization chamber, 210
life line, 212
lock-out tag, 216, 217, 218, 277
manhole hooks, 212
measurement of gases, 211
nonsparking tools, 219
oxygen deficiency indicator, 210, 211
protective clothing, 35, 210, 212, 222, 223, 225, 226, 230
308, 355
purchase, 230
safety glasses, 354
safety harness, 212, 308
safety tongs, 344
self-contained breathing apparatus, 222, 357
storage containers, 210
tag, 216, 217, 218
tongs, 344
traffic warning signs and flags, 212
ventilation, 210, 219
Safety harness, 212

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Index 625
Safety hazards
acids, 210, 354
activated sludge, 28, 61
aeration tanks, 35, 40, 221
air distribution system, 35
air filters, 35
air headers and diffusers, 35
amines, 224
anaerobic digesters, 102,103, 107, 109, 112,134,137,141,
157
applying protective coatings, 223
back strains, 212
bar screens, 215
biocides, 224
blowers, 22, 35
burns, 356
carbon tetrachloride, 290, 354
chemical storage, 355
chemicals, 210, 214, 225, 354
clarifiers, 210
collection systems, 212, 223
comminutors, 216
confined spaces, 157, 210, 212, 214, 215, 216, 219, 221,
308, 365
corrosive chemicals, 354
cross connections, 227
cuts, 356
digesters, 219
digestion equipment, 219
drowning, 35
dysentery, 209, 353
effluent disposal, 200
electrical, 35, 210, 356
emergencies, 35, 230
empty digesters, 157
explosion, 109, 112, 210, 354
falls, 209
fire, 66, 210, 226, 227, 354, 357
foam, 224
fuels, 210, 223
gasoline vapors, 210
grit channels, 219
hepatitis, 209, 353
hoists, 35, 40
hydrogen sulfide, 100, 157, 210, 215, 216, 219, 223, 354,
364
ice, 35, 38, 40, 219, 222
industrial waste treatment, 210, 223, 224
infections, 209, 353
infectious diseases, 209
laboratory, 225
lift station, 215
lighting, 35, 40
manholes, 212
mercury, 210, 356
methane, 98, 107, 136, 143, 160, 210, 219
movement of chemicals, 355
natural gas, 210
noise, 210
oil and grease soaked rags, 66
oil and grease spills, 35, 40, 61
oxygen deficiency, 210
pH, 224
physical injuries, 209
ponds, 222
protective coatings, 223
pumping stations, 215
radiological, 210
sampling, 225
sedimentation basins, 219
sewer cleaning, 214
sharp objects, 41
slippery surfaces, 28,35, 38, 40, 61, 209, 216, 219,221,222
sludge drying beds, 163
spills, 35, 221, 223
start-up, 215
suffocating gases or vapors, 210
surface active agents, 224
surface aerators, 35
tetanus, 209, 353, 354
toxic chemicals, 210, 354
toxic gases or vapors, 210, 223, 226, 356, 364
traffic, 212
treatment plants, 215
trickling filters, 221
typhoid fever, 209, 353
vapors, 210
waste disposal, 357
wet wells, 215, 216
Safety information, 214, 219, 229
Safety policy, 230
Safety program
accident prevention, 356
accident report form, 231
accidents, 230
backflow prevention, 227
building, 247
conditions for program, 229
cross connections, 227
development, 229
drills, 230
effectiveness, 229
emergencies, 230, 249
emergency team, 249
entry of confined spaces, 212
equipment use, 225, 229, 230
fire control methods, 227
fire drills, 230
fire prevention, 226, 227
forms, accident, 230
housekeeping, 215, 216, 219, 223, 354
immunization shots, 209
importance of program, 230
information, 214, 219, 220
inoculations, 353
laboratory, 225
laundry service, 210
library, 249
locker room, 210
management responsibility, 209, 230
manhole entry, 212
meetings, 229, 230
need, 209
OSHA, 353
operator responsibility, 209
paper work, 230
personal hygiene, 354
planning, 230
policy, 230
procedures, 209
promotion, 230
protective clothing, 35, 210, 222, 230, 355
purchase of equipment, 250
purpose, 209
report form, 231
review of plans and specifications, 231
rules, 354
safety policy, 230

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626 Treatment Plants
safety, rules, 231
sampling techniques, 225
sewer-use ordinance, 223
starting program, 230
storage of chemicals, 355
tailgate safety meetings, 229
testing procedures, 225
training programs, 229, 230, 231, 249
uniforms, 210
water supply protection, 227
work clothes, 210
Safety rules, 231
Salmonella, 355
Samplers, 361
Sampling
access, 196
activated sludge, 15, 16, 44, 58
analysis, 199
anaerobic digestion, 142, 150
blacktop drying beds, 164
composite, 190, 359, 360
devices, 361
dissolved oxygen, 196, 197
effluent disposal, 190
equipment, 190, 361
errors, 199, 359
frequency, 200
grab, 190, 360
importance, 359
labeling, 200
location, 194, 197, 199, 359
monitoring, 191
plug flow sampling, 360
preservation, 199, 200, 361, 363
purpose, 359
receiving water, 191
representative sample, 195, 359
review of results, 199
safety, 225
samplers, 361
size of sample, 200
sludge, 361
sludge drying beds, 163
storage, 199, 200
supernatant, 145
techniques, 359
temperature, 193, 194
thief hole, 117, 125, 126
time, of sampling, 195, 359
types, 360
well, sampling, 117, 125, 126
Saprophytic organisms, 98
Screens
see Volume I, Chapter 4
Screw-flow pumps, 257, 266, 267
Screw-lift pumps, 257
Scum, 98, 135, 161
problems, 269, 286
unplugging pipes, 311
Scum and foam control, anaerobic digester, 132, 135
Seal cage, pump, 256
Seals, pump, 270, 272, 273, 276, 278, 279
Secchi disc, 15, 364
Secondary sedimentation
see Volume I, Chapter 5
Sediment traps, 102, 105, 108, 117, 118, 119, 149
Sedimentation
also see Volume I, Chapter 5
aerobic digestion, 160, 161
formulas, 507, 508
problems (arithmetic), 499, 503
safety, 219
secondary, 15, 28, 41, 50, 60, 75
Seed sludge
activated sludge, 43, 44
aerobic digestion, 160
anaerobic digestion, 58, 101, 136, 137, 141, 145
Seizing, 68, 70
Selection of formula, 495
Self-contained breathing apparatus, 222, 357
Sensors, 316, 318
Separatory funnel, 342
Septic sludge, 45, 60
Septicity, 60
Serological pipets, 340, 348
Service record card, 245, 246
Settleability test, 377
Settleable solids test, 366
Settlometer, 44, 377
Sewer cleaning, 214
Sewer gases, characteristics, 211
Sewer-use ordinance, 223
Shaft, pump, 250, 253, 258, 259, 270
Shear pins, 283, 295
Sheaves, 290
Shock loads
activated sludge, 13
aerobic digestion, 161
anaerobic digestion, 142
Short-circuiting, 38
Shuntflow meter, 313, 315, 316
Shutdown
activated sludge, 63, 64
anaerobic digesters, 155, 157
blowers, 35, 64
draining pump, 283
effluent disposal, 191
pumps, 269, 270, 272, 273, 274
surface aerators, 64
SI system
see Metric
Significant figures, 498
Single-stage pumps, 257, 264
Sixty-minute settling test, activated sludge, 44, 45
Size of sample, 200
Skewed distribution of data, 532
Sleeves, 253
Sludge
digester, 98
raw, 98, 135
unplugging pipelines, 311
Sludge age, activated sludge, 15, 16, 46, 58, 59, 60, 62
Sludge age, test, 378
Sludge blanket, secondary sedimentation, 50, 57
Sludge bulking, 59, 66, 75
Sludge density index (SDI)
activated sludge, 50, 51, 53
test, 378
Sludge dewatering
also see Volume III, Chapter 22
tests, 391
Sludge digestion, anaerobic
see Anaerobic sludge digestion
Sludge disposal
see Digested sludge handling and
Volume III, Chapter 22
Sludge drying beds
application of sludge, 163

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Index 627
blacktop drying beds, 164, 165
depth of sludge, 163
description, 161, 162, 163
drain system, 161, 162, 163
drying time, 163
fertilizer, 163
flies, 163
gravel, 161, 162
green sludge, 163
health regulations, 163
lime application, 163
maintenance, 163
odors, 163
operation, 163
partially digested sludge, 163
process description, 161, 163
purpose, 161
removal of sludge, 163
safety, 163
sampling, 163
sand, 161, 162
soil conditioner, 163
solids, 163
time for drying, 163
underdrain system, 161, 162, 163
volatile solids, 163
withdrawal from digester, 163
Sludge handling
see Digested sludge handling
and Volume III, Chapter 22
Sludge lagoons, 164
Sludge piping, anaerobic digestion, 102
Sludge pumping
anaerobic digester, 137, 143, 149, 153, 154
primary sedimentation
see Volume I, Chapter 5
Sludge pumps, 257, 283, 284
Sludge re-aeration, activated sludge, 72, 73, 74, 75
Sludge removal rate, pumping, 141
Sludge residence time
see Sludge age
Sludge sampling, 361
Sludge solids tests, 378
Sludge thickening and conditioning
see Volume III, Chapter 22
Sludge treatment
see Anaerobic sludge digestion
Sludge volume index (SVI)
activated sludge, 50, 51, 53
test, 378
Sludge withdrawal, anaerobic digester, 141
Sluice gates, 299, 306, 307
Sodium azide modification of DO test, 424
Sodium sulfide, 223
Solids
balance, 146, 151
disposal, 145
Solids balance, 146, 151
Solids disposal
see Digested sludge handling
and Volume III, Chapter 22
Solutions, chemical, 348
Solving problems
see Problem solving
Sour digester, 135, 138, 142
Specific conductance, 363, 453
Spectrophotometer, 348
Sphere, 485, 486
Square root, 482, 539
Squares, 481
Standard rate, anaerobic digester, 98
Standard solution, 348
Standardization of equipment, 319
Standards
effluent quality, 187
treatment efficiency, 187
Start up
activated sludge, 43, 63
aeration tanks, 43
aerobic digestion, 160
anaerobic digestion, 136
assistance, 43
blowers, 35, 39, 41, 43
chemical addition, 43
compressors, 39
digester, 136
digester foaming, 139
effluent disposal, 191
help, 43
inspecting new facilities, 36
pumps, 256, 269, 270, 272, 274
safety hazards, 215
water level controls, 285
Stator, 257, 266, 274, 289
Step-feed aeration, activated sludge, 38, 49, 75, 76
Sterilization, 410
Stethoscope, 287
Stock inventory, 551
Stopcock, buret, 346
Storage
chemicals, 225, 342, 355
samples, 199, 220, 361
Storm flows, 13, 51, 52, 58
Storms, 558
Straight edge, alignment, 254, 293
Strikes, 558
Stuck digester, 135, 138, 383
Stuffing box, valve, 296, 297, 298
Stuffing boxes, pump, 255, 258, 278
Submersible pump, 257, 261
Subtraction, 475
Suction, pump, 251, 254, 256, 270, 271
Suffocating gases or vapors, 210
Sulfate test, 363, 455
Summators, 315, 316, 317
Supernatant
activated sludge, 13, 57, 58, 60, 72, 75, 137
control, 139
definition, 13
disposal, 145
operation, 139
quality, 145, 151, 154
return, 13, 57, 58, 60, 72, 75, 136
solids, 145, 151, 154
toctc
tubes, 102, 103, 104, 106, 145, 149, 150
Supernatant test, 394
Surface active agents, safety, 224
Surface aerators, 16, 17, 21, 28, 35, 64, 65, 66
Surface loading, 499, 504, 507, 508
Surfactants, 60, 224, 360
Surfactants, test, 455
Suspended solids
in aerator, test, 380
test, 367
Storage of chemicals, 355
Switches, level control, 269, 276, 285

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628 Treatment Plants
T
TDH, 278
TOC, 15
TOC test, 456
Tailgate safety meetings, 229
Tanks, maintenance, 247
Tare weight, 368
Techniques, laboratory, 356
Temperature
anaerobic digester, 101
metric, 487
test in digester, 395
test in wastewater, 363, 455
wastewater characteristics, 455
Temperature, effect
activated sludge, 13, 15, 46, 58
aerobic digestion, 160
anaerobic digestion, 98, 101, 142, 148, 151, 153, 155
blacktop drying beds, 164
effluent disposal, 193
monitoring, 193
plugging pipelines, 311
receiving water, 193
sludge drying beds, 163
Terminology, wastewater treatment, 577
Tertiary treatment
see Volume III
Test tubes, 342
Tetanus, 209, 353, 354
Thermal valve, 109
Thermometer, 343
Thermophilic bacteria, 101
Thick foam, activated sludge, 49
Thickness gage, alignment, 293
Thief hole, 117, 125, 126, 383
Titration, laboratory, 341, 348
Tongs, safety, 344
Total coliform, test, 409
Total dynamic head, 278
Total organic carbon, 15
Total organic carbon test, 456
Totalizers, 315, 316, 317, 520
Totalizing receiver, 316, 317
Toxic chemicals, 210
Toxic gases or vapors, 210, 223, 226
Toxic wastes
activated sludge, 58, 60, 72, 75
aerobic digestion, 161
anaerobic digestion, 153, 154, 155
effluent disposal, 190, 191
gases, 210, 223, 226, 356
materials, 354
Traffic hazards, 212
Training
courses, 230
management planning, 230
safety, 229, 230, 231, 249
Transmittance, light, 349
Transmitters, 315
Traps
condensate, 117
drip, 117
sediment, 117
Treatment efficiency, 187
Treatment plant maintenance, general
also see Mechanical equipment, Mechanical maintenance,
Meter maintenance, and Volume III, Chapter 26,
Instrumentation, and Chapter 29, Support Systems
buildings, 247
channels, 247
costs, 245
grounds, 248
inspection, 247
landscaping, 248
library, 249
paint, 247
preventive maintenance program, 276
preventive maintenance records, 245
public relations, 247, 248
records, 245
safety, 247
tanks, 247
Treatment plant problems (English System)
activated sludge, 500
blueprint reading, 503
chlorination, 502
clarifiers, 499
efficiency, 502
grit channels, 499
laboratory results, 502
ponds, 501
sedimentation, 499
sludge digestion, 501
trickling filters, 500
Treatment plant problems (Metric System)
activated sludge, 504
blueprint reading, 507
chlorination, 506
clarifiers, 503
efficiency, 507
grit channels, 503
laboratory results, 506
ponds, 506
sedimentation, 503
sludge digestion, 505
trickling filters, 504
Treatment plants, safety, 215
Trend chart
activated sludge, 50
data, 142, 148, 150, 531
Triangle, area, 483
Triangle, lab, 344
Trickling filters
also see Volume I, Chapter 6
formulas, 508, 509
problems (arithmetic), 500, 504
safety, 221
Tripod, lab, 344
Troubleshooting
activated sludge, 57, 64
aerobic digestion, 161
anaerobic digestion, 153
chain drive, 291
effluent disposal, 191, 192, 193
flow meters, 319
gas system, 154
meters, 319
pumps, 269, 270
surface aerators, 35
water level controls, 285, 286
Turbidity
measurement, 363, 456
meter, 15
units, 457
Turbine pumps, 257, 264
Types of records, 550
Types of reports, 555
Typical monthly report, 557

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Index 629
Typhoid fever, 209, 353
U
Underground disposal, 187
Uniforms, 210
Units (in formulas), 475, 476, 498
Unplugging pipes, pumps and valves
costs, 311
cutting tools, 312
digested sudge lines, 311
equipment, 311, 312
high velocity pressure units, 312
methods of unplugging, 311, 312
pipes, 311
pressure clearing methods, 311
pumps, 312
scum lines, 311
sludge lines, 311
valves, 312
Upset digester, 135, 138, 142
Use of digester gas, 107
Use of lab glassware, 348
V
V-notch weir, 313, 315, 316
Vacuum filtration
also see Volume III, Chapter 22
blankets, 166
cake, 166
cycle, 166
description, 166, 167, 168
elutriation, 166
odor, 166
operation, 166
sludge conditioning, 166
sludge dewatering, 141, 166
Vacuum pump, 345
Vacuum relief valves, 102, 105, 108, 109, 110, 111
Valve chamber gaskets, 283, 284
Valve friction losses, 495, 496, 497
Valve parts
bonnet, 301, 303
gear, 296, 301
gland, 299
packing, 296, 297
plug, 301, 303
rising stem, 296
seal, 301
seats, 296, 299, 303
stuffing box, 296, 297, 298
threads, 296, 297
Valves
ball valves, 283, 284
check valves, 271, 278, 285, 299
description, 296, 299
foot valves, 296, 297, 298, 299
location, 271
maintenance, 296, 299
plug valves, 299
unplugging, 311, 312
Valves, maintenance, 102, 278
Vanes, pump, 250, 251
Vapors, toxic or suffocating, 210
Variable-speed belt drives, 291
Variance, 533
Variations in data, causes, 518
Velocity flow, 489
Velocity formulas, 507, 508
Velocity head, 315
Velocity meter, 313, 315, 316
Vendor, 551
Ventilation, safety, 210, 219
Venturi meters, 313, 315, 316
Venturi tube, 313, 315, 316
Vertical wet well pumps, 257, 264
Vibrations, electric motor, 287
Vibrations, pump, 272, 273, 293
Visual inspection
activated sludge, 15, 50
anaerobic digestion, 148, 149
blacktop drying beds, 164
chain drive, 291
effluent disposal, 190, 191
sludge drying beds, 163
Volatile acid/alkalinity, 142, 183, 501, 505
Volatile acids, test, 383
Volatile liquids, 355
Voltage fluctuations, 518
Volumes
cone, 485
cylinder, 485
formulas (English System), 507
formulas (Metric System), 508
metric, 486
prism, 485
rectangle, 485
sphere, 486
Volumetric flask, 341, 348
Volumetric pipets, 340, 348
Volute, 22, 271, 272, 273, 274
W
WAS, 41, 47, 48, 49, 135
Warning tag, 216, 217, 218, 277
Waste activated sludge, 41, 47, 48, 49, 135
Waste gas burner, 108, 117, 124, 150, 221
Wastewater
flows, 359
pumps, 250
Wastewater characteristics
acidity, 398
alkalinity, 387, 399
ammonia, 433
biochemical oxygen demand (BOD), 427
carbon dioxide (C02), 389
chloride, 403
chlorine residual, 405
clarity, 364
coliform group bacteria, 409
dissolved oxygen (DO), 424
dissolved oxygen in aerator, 379
grease, 445
hydrogen ion (pH), 432
hydrogen sulfide, 365, 366
lime analysis, 395
mean cell residence time, 382
nitrogen, 433
ammonia, 433
nitrate, 433
nitrite, 433
total Kjeldahl, 433
oil and grease, 445
pH,432
phosphorus, 447
settleable solids, 366
sludge age, 379
sludge (digested) dewatering characteristics, 391
sludge density index (SDI), 378

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630 Treatment Plants
sludge solids, 371
sludge volume index (SVI), 378
solids, total (residue), 451
specific conductance, 453
supernatant, 394
surfactants, 455
suspended solids, 368
suspended solids in aerator, 380
temperature, 455
total organic carbon, 456
turbidity, 456
volatile acids, 383
Wasting activated sludge, 41, 47, 48, 49
Water hammer, 278, 283
Water level controls, 285
Water quality criteria, 189
Water quality indicator, 189
Water seal, digester covers, 102, 105
Water supplies, 227
Water uses, 189
Wearing rings, pump, 255, 258, 270, 272, 273, 278
Weight measurement (metric), 486
Weight-volume relations, 488
Weir overflow formulas, 500, 504, 507, 509
Weirs, 313, 314, 316
Wet well pumps, 257, 261, 264
Wet wells, 215, 216, 271, 272, 319
White foam, activated sludge, 38, 49
Whole numbers, 475
Wildlife, 189
Winkler method of DO test, 424
Wire to water pump efficiency, 494
Withdrawal of sludge digester, 141
Work, 491
Work clothes, 210
Work sheets, laboratory, 350
Work stoppages, 558
Writing reports
see Report writing

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NOTES

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