OPERATIONS MANUAL
AWBERC LIBRARY U.S. EPA
PACKAGE
TftEATmiflT
PLAflT/
PROJECT OFFICER
LEHN POTTER
MUNICIPAL OPERATIONS BRANCH
OFFICE OF WATER PROGRAM OPERATIONS
WASHINGTON, D.C.
for the
OFFICE OF WATER PROGRAM OPERATIONS
U.S. ENVIRONMENTAL PROTECTION AGENCY
WASHINGTON, D.C. 20460
CONTRACT NO. 68-01-3547
APRIL 1977
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ACKNOWLEDGMENTS This operations manual was prepared for the Office of
Water Program Operations of the United States Environ-
mental Protection Agency. Development and preparation of
the manual was carried out by the firm of Stevens, Thomp-
son & Runyan, Inc., Portland, Oregon, under the direction of
Chuck Zickefoose. Recognition is due to plant operators,
Oregon Department of Environmental Quality, Kansas
Department of Health;and Environment, California Regional
Water Quality Board, Colorado Department of Health,
National Sanitation Foundation, and the manufacturers of
package plants for their assistance in providing information
for the manual and, for comments on material content. This
manual was illustrated by Bryce Kimberling and graphs were
prepared by Jimi Kent and John Blankenbiller. EPA coordi-
nation and review was carried out by Lehn Potter, Office of
Water Program Operations.
. The mention of trade names of commercial products
in this publication is/for illustration purposes and does not
constitute endorsement or recommendation for use by the
U.S. Environmental Protection Agency.
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CONTENTS
ACKNOWLEDGMENTS
CONTENTS
INTRODUCTION
HOW TO USE THIS MANUAL
PART 1 OPERATIONS
Section 1
Plant Survey 1-1
Section 2
Observations 1 -3
Pretreatrnent 1-3
Aeration Tank 1-4
Clarifier 1-5
Return Activated Sludge 1-7
Waste Sludge 1-8
Total Sludge Loss 1-9
Section 3
Tests and Interpretations 1-10
Settleability 1-10
Settlometer Tests 1-12
Centrifuge for Suspended Solids 1-15
pHTest 1-16
Residual Chlorine Test 1-16
Other Tests and Measurements 1-17
Section 4
Operational Procedures 1 -20
Pretreatrnent 1-20
Aeration Basin 1-20
Clarifier and Return Activated Sludge 1-22
Wasting Program and Digestion 1-23
Disinfection 1-25
Chemical Additions 1-26
Section 5
Final Plant Survey 1-27
Section 6
Laboratory Procedures 1-28
Settleability 1-28
Settlometer Tests 1 -30
Centrifuge for suspended solids 1-31
pHTest 1-33
Residual Chlorine 1-34
in
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Section 7
Troubleshooting 1 -35
Section .8
Plant, Checklist 1-38
Inlet and Outlet Facilities 1-39
Pretreatment 1-39
Aeration Basin 1-40
Clarifier 1-40
Pumps and Motors 1-41
Operational Controls 1-41
PART 2 BASICS
Section 1
Basic Principles of Wastewater Treatment 2-2
Section 2
Types of Wastewater Treatment Processes 2-5
Conventional Activated Sludge 2-5
Contact Stabilization 2-7
Extended Aeration 2-8
Oxidation Ditch 2-8
RBC (Rotating Biological Contactor) 2-9
ABF (Activated Bio-Filter) 2-9
Physical-Chemical 2-10
Section 3
Description of Unit Process Equipment 2-11
Pretreatment 2-11
Aeration 2-12
Clarification 2-13
Sludge Handling and Disposal 2-14
Pumping 2-15
Chlorination 2-18
Section 4
Effects of Weather 2:19
PART 3 POTPOURRI
Section 1
Case Histories 3-1
Operational Hints 3-1
Equipment Modifications 3-2
Tools 3-5
IV
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Section 2
Safety and Emergencies 3-7
General 3-7
Laboratory Safety 3-7
Chlorine Safety 3-8
Emergencies 3-8
Section 3
Plant Management 3-11
Plant Owner 3-il
Plant Operator 3-11
APPENDIX
Bibliography A -1
Glossary B-1
Operation and Maintenance Schedule C-1
Settlometer Graph D-1
Monthly Trend Graph E-1
Flow Record F-1
Metric Equivalents G-1
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INTRODUCTION . Package treatment plants were originally designed to
serve areas that could not be easily connected to an existing
sewage treatment plant. Such areas include the subdivisions
that began springing up in the fifties and commercial estab-
lishments such as restaurants, motels, and parks. More
recently, package plants have increased to a size that can
serve small municipalities. Many were sold with the idea that
the plants would operate themselves and, therefore, could be
turned on and forgotten. However, to meet today's more
demanding pollution discharge regulations, these plants
require daily attention by a knowledgeable and conscientious
operator. In addition, the new operator needs time to famil-
iarize himself with the plant. This manual is designed to give
the operator an increased knowledge of the basics and aid
in effective operation of a package treatment plant.
Some problems in operation of the package plant may
be beyond the ability of the operator to control and are too
detailed to be presented in this manual. The operator should
learn to identify and define these problems in order to turn
to someone for outside help. Outside help may be the oper-
ator's consulting engineer, the operator of the treatment
plant in a nearby town, or an engineer from the State Pollu-
tion Control Agency. One possible solution may be for
several package plant owners to pool resources and provide
an areawide management person to be called in for consulta-
tion on special problems.
Besides the treatment plant operator, this manual is
also directed to the plant owner and the design engineer.
The owner is either the actual purchaser of the plant
if privately owned or the individual or group responsible
for making policy decisions concerning the treatment plant;
such as a city council.
The owner is responsible for adding to the treatment
plant when needed, controlling sewer construction practices
in the service area, keeping supplies at the plant and super-
vising the operator. Most importantly, the owner is ulti-
mately, legally, and administratively responsible for the per-
formance of the treatment plant.
For detailed descriptions of the duties and responsibil-
ities of the owner, the reader should refer to Part III, Sec-
tion 3 — Plant Management.
VI
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For the engineer, the purposes of this manual are
two-fold. It provides additional information that can be used
wholly or in part with an O&M manual written for a specific
plant. In addition, it can aid the consulting engineer in the
selection of a plant by pointing out design problems found in
some package plants.
Many of these problems and actions that operators have
taken to overcome them are covered in the section on Case
Histories.
VII
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HOW TO USE THE MANUAL
This manual is intended to be a handy reference for
operation of a biological package treatment system. For
detailed maintenance procedures, the operator should refer
to the manufacturer's recommendations or other sources
such as the plant operation and maintenance manual.
HOW DOES IT WORK?
How to Find Your Way Around
Part I—Operations
The manual is divided into three parts, each with a
different use. For example:
1. For a solution to a specific problem go to the
Troubleshooting section of Part I. Part I also tells
how to operate the plant through daily attendance.
2. Have a question on how the treatment plant works?
Go to the Basics in Part II.
3. Part III has useful information on Case Histories,
Safety and Emergencies, and Plant Management.
It also contains the Appendices.
Part I assumes that the reader is familiar with the pro-
cess of biological wastewater treatment. If not, check out
Part 11 on the Basics for a quick review.
1-1 Plant Survey—Tells what the treatment plant oper-
ator should be observing in the way of sight! sound, and odor
upon first reaching the plant.
I-2 Observations—A detailed discussion of the different
parts of the treatment plant and the things the operator can
learn about the condition of the plant by observing them.
For example, if there is a lot of foam on the aeration tank,
this section will tell why it is there.
I-3 Operational Tests and Interpretations—A discussion
of some of the basic tests to keep a plant in proper operation.
Additional tests will probably be required by the National
Pollution Discharge Elimination System (NPDES) permit and
the type and number vary from state to state. Therefore,
references are included so the operator can find the correct
laboratory procedure for these tests.
This section should be used in conjunction with Sec-
tion I-6 to confirm any observations obtained on plant
inspection. The following section on Operational Procedures
should then be used as guidance in implementing changes in
plant operation.
I-4 Operational Procedures—The section with the
instructions—what we always fail to read. Need we say
more?
viii
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Part II—Basics
Part Ill-Potpourri
1-5 Final Plant Survey—A sort of wrap-up tour of the
plant before leaving.
1-6 Laboratory Procedures-Actual laboratory instruc-
tions for the basic tests discussed in Section 1-3.
1-7 Troubleshooting-Information on what to do or
where to go to correct an operational problem.
1-8 Plant Checklist—A handy checkoff list of things to
do each time the plant is visited.
Some of the things you already know are listed in this
part along with some things you possibly don't know.
Simplified diagrams illustrate specific ideas and equipment.
This will be of special benefit to new operators. The bold
type is used to place emphasis on certain words found in the
Glossary in the Appendix.
This part includes information which will be helpful
to the operator, but may not be part of day to day operation.
Several of the items located here are Case Histories, Safety
and Emergencies, Plant Management, and Appendices.
NOW...
You have some idea of what's inside. Flip through the
pages, get acquainted with the way the Troubleshooting
Guide 4 works, review the Basics, if necessary. Use it in the
way that best fits your needs.
FINALLY
Remember that conditions, arrangement, and equip-
ment will vary from plant to plant depending on factors
such as design, load, or waste. The values presented are typi-
cal, but may vary. See how the contents relate to what you
have in your own treatment plant.
After that is done, go to the section or sections that will
help answer any questions raised.
Most of all—don't try to read the manual cover to
cover—pick the parts that interest you and can help you the
most.
IX
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OPERATONS
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SECTION 1
PLANT SURVEY
Problem Areas
What are these possible
problems?
Problems—Yes?
What should be done if
problems exist?
Part I is intended to present a suggested plan of opera-
tion for the operator as if he pulls up to the plant in his
pickup, opens the front gate, and starts his daily duties after
being away from the plant for 16 hours or more.
Sight, sound, smell, and touch are the senses the opera-
tor must learn to use in making a quick inspection of the
plant. Close observation of the plant during normal opera-
tion will enable the operator to identify during the plant
survey any possible problems.
Some of the things to take note of are:
1. Does everything look right? Is there any evidence
of vandalism, high flows, foaming tanks, or other
visual signs or problems.
2. A plant has a characteristic sound while operating.
If this is not evident upon arrival, possibly some-
thing has gone wrong mechanically.
3. As with sound, the treatment plant should have a
characteristic but not unpleasant smell. An ab-
normal, unpleasant odor may indicate problems.
4. Are the motor bearings too hot to touch? The
operator with experience will learn the "feel" of
housings covering moving parts so that any unusual
vibration or temperature change will be noticed.
By making use of the senses to notice the possible
problems, the operator should be able to verify quickly that
everything is working properly.
If problems should appear, the operator must locate
the source of the problem and determine if outside help is
needed. The goal is to return the plant to proper operation
as soon as possible—no matter how large or small the
problem. If the trouble is in the treatment process, either
mechanically or biologically, the section on troubleshooting
will be helpful in correcting the problem.
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Problems—No?
What is done if no
problems exist?
If everything appears to be operating normally upon
initial inspection, the operator should continue with the
routine operation and maintenance procedures outlined in
the following sections.
To organize the daily duties, the plant operator is en-
couraged to develop an outline based on the topics covered
in this and following sections. It should include a checklist
similar to the one presented in Section 8 so that the operator
will not overlook certain areas in his or her daily duties. It
will also be helpful if someone less familiar with the plant is
called in to work during the regular operator's absence.
A Note to the Consultant
(Consulting engineers using this manual to supplement
specific plant manuals are encouraged to review the plant
layout, equipment, and type of operation in comparison with
the sequence of events presented. A schedule for the opera-
tor to follow, naming equipment that he has in his plant,
will be a valuable tool both for his use and any others that
have responsibility of the plant in his absence.)
1-2
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SECTION 2
OBSERVATIONS
PRETREATMENT
Odor
How are odors controlled?
Color
What does a black influent
color and septic odor tell?
Walking around the plant following the normal flow
route gives the operator an idea of the type of wastewater
the plant has received since the last visit. Following are some
of the indicators.
Odors in the area may indicate evidence of septic sew-
age, scum buildup, or a strong industrial waste in the waste-
water. If so, a temporary solution is to wash down the entire
area to remove the scum. If grease or industrial waste
becomes a problem, the operator should locate the source
and attempt to control it at its source through the use of
existing ordinances or discussions with the contributor.
Other sources of the odor may be an accumulation of
rags and other debris on the comminutor or bar screen. Fre-
quent removal (twice daily) and daily disposal by burying
will help to control the odor.
The color of the influent tells a lot about the waste. A
black color accompanied by a septic odor may indicate that
part of the wastewater is staying in level sewer lines during
low flow periods. The low flow results in solids settling out
and slowing down the flow. Manholes should be inspected
for the buildup of sludge and/or sand. These lines and man-
holes require periodic flushing. A source of information on
how to locate and flush the lines is:
Handbook for Sewer System Evaluation and
Rehabilitation
Publication No. EPA 430/9-75-021, December, 1975,
MCD-19
Available from:
General Services Administration (8 FFS)
Centralized Mailing List Services
Building 41, Denver Federal Center
Denver, Colorado 80225
1-3
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Silt in lines?
Visual
What does a "high-water
mark" indicate?
A reddish or brown color may indicate silt getting into
the lines which, in turn, increases the wear on and requires
more frequent maintenance of pumps and other mechanical
items. Source of the silt may be a broken line or a side
sewer excavation.
A high-water mark greater than normal in the inlet
channel may indicate a high flow during operator's absence
or plugging downstream in the bar screen or comminutor.
These areas should be checked for proper operation. Com-
minutor blades may be dull and may not be providing good
cutting action.
AERATION TANK
Turbulence
How to tell if complete
mixing is occurring.
What may cause low DO?
Surface Foam and Scum
What type of foam should
be present?
The operator should observe the entire aeration tank
surface for turbulence. Though some of his conclusions
will be based on past experience, the extent of surface
activity will show if the contents are thoroughly mixed
throughout the entire aeration tank. Watching the surface
for dead spots will tell if mixing is the same throughout the
aeration tanks.
An equipment modification for eliminating dead spots
in the aeration tank is shown in the Case Histories section.
The operator should raise or lower air usage based on
Dissolved Oxygen (DO) readings. See Section 4-Operational
Procedures for information on proper DO levels in the aera-
tion basin.
If the DO does not increase above 1.0 when all aeration
equipment is operating, it may be due to plugged air lines,
blower not sized right, or high strength waste. If normal air
feed fails to raise DO over a 24-hour period, a further check
of the mechanical air system may be needed.
The type of foam or scum, if any, on the aeration tank
surface, and to a lesser extent, the color of the mixed liquor
gives the operator a clue to how well the process is working.
Fresh, Crisp, White Foam: Only a modest accumula-
tion of white, or at least light colored, crisp appearing foam
is usually present on aeration tank surfaces when an excellent
final effluent is produced. The operator should take note of
the conditions in the process and keep them within these
ranges because whatever is happening is just right.
1-4
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What causes thick dark
foam ?
What do hydrogen sulfide
odors mean?
CLARIFIER
Final Effluent Appearance
If the effluent is clear—fine!
But. . .
If not, something needs to
be done.
Excessive, Billowing White Foam: If the aeration tanks
are covered by thick billows of white sudsy foam, the opera-
tor can be quite certain that the sludge is too young and that
sludge age should be increased by reducing the sludge wasting
rate.
Operators who have actually gone through this white
foam cycle realize that not all foam is caused by detergents.
Thick, Scummy, Dark Tank Foam: At the other
extreme, the operator may observe a dense and somewhat
greasy scummy layer of deep tan to brown foam covering the
entire aeration tank surface. Such foam almost always indi-
cates that the sludge is too old and possibly overoxidized.
In this case, the answer is to increase sludge wasting rates.
Here again, the sludge wasting rate should usually be
increased gradually, possibly 20 percent of return rate per
day, on a day-to-day basis while watching the graph plot to
see how the changes affect the effluent and mixed liquor
solids.
Sludge Color and Odor: At times a poor quality, ex-
tremely dark brown colored sludge, releasing hydrogen
sulfide odors may be seen in the aeration tanks. It does not
take much experience to recognize this problem. The
solution is to increase air discharge rates immediately to pro-
vide a 2-3 mg/L DO in the aerator. A time clock may be nec-
essary to keep the DO up. See Part I, Section 4, Aeration
Basin, for a typical time clock setting.
When the system is operating well, it will generally have
a dark brown aeration tank color and will be accompanied by
an earthy odor. If the mixed liquor solids level becomes
too low, the odor will either disappear or change to that of
fresh grease or lard.
The operator should also observe the final effluent and
the clarifier water surface to see how the process is working.
If the final effluent appears clear or is improving day by
day, obviously the operator should continue to do what he
has been doing.
However, if it appears turbid or contains noticeable
solids, trouble may be just around the corner. Visual
observations and control tests will help to show what needs
to be done.
1-5
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Final Clarifier Surface
Appearance
How is sludge bulking
controlled?
How does solids washout
differ from sludge bulking?
Sludge Bulking: Operators who have experienced true
classic sludge bulking find it all too easy to remember and
identify. It will usually show up as a uniform sludge blanket
that lies a few inches below the surface of the entire clarifier
and may even cause the mixed liquor solids to pour out over
the final effluent weirs. It may be due to shock loadings and
inefficient aeration devices; however, classic sludge building
usually is caused by improper operational control rather than
by inadequate plant capacity.
This type of bulking, which is practically always associ-
ated with young sludge, usually can be eliminated by reduc-
ing sludge wasting rates and changing return sludge rates. If
a centrifuge is used to find RAS concentrations, the goal
should be to adjust the return rate to equal the concentration
found in the settlometer settling test after 2-3 hours of settl-
ing. This concentration can be found by multiplying the
mixed liquor concentration by 1,000 and dividing by the
volume settled after 2-3 hours. Adjust the return rate either
up by 20 percent to cause the desired change and recheck
after 24 hours. If this causes improvement, keep going in
this direction. If not, move return in other direction. Sludge
blanket in the clarifier should be watched for improvement
too. Some sludge may still be lost in the effluent, but the
goal is to bring the sludge quality back into a good range.
If the plant has the capability, contact stabilization
might also be tried if the condition does not improve in
10-14 days.
For further information, see EPA Bulletins
330/9-74-001 a, b, c, d, and e and Operator Pocket Guide to
Activated Sludge, Part II, listed in the References Section
of this manual.
Sludge Solids Washout: Excessive sludge washout
over the final effluent weirs, when the upper surface of the
sludge blanket is more than three feet below the clarifier
water surface and when sludge settles properly in the lab-
oratory tests', should not be confused with classic sludge
bulking.
Solids washout is generally caused by hydraulic over-
loading, improper clarifier inlet port arrangements, or
faulty final effluent weir locations or a combination of these.
Clumping: At times, large masses of sludge, possibly
four inches (0.11 meter) in diameter, may be seen rising, then
bursting, and finally spreading over the clarifier surface. This
has sometimes been called "clumping." This may also indi-
cate a need to scrape the sides of sloping clarifiers that do
not have mechanical sludge removal.
1-6
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What happens when the
sludge age is too old?
What factors make
straggler floe worse?
What is pin floe?
How does settlometer
test confirm pin floe?
RETURN ACTIVATED
SLUDGE
Ashing: At other times, smaller sludge particles usually
deep brown to gray in color, may rise and then spread over
the tank surface. Some operators call this "ashing."
This problem occurs when sludge age is too old and it
can usually be eliminated by increasing sludge wasting rates.
Reducing air discharge rates to the minimum levels that wilj
still maintain aerobic conditions in the aeration tanks may
also be helpful.
Straggler Floe: At times, small, almost transparent,
very light fluffy, buoyant sludge particles (1/8 to 1/4 inch,
3-6 mm in diameter) may rise to the clarifier surface near the
outlet weirs. This condition is usually worse in a shallow
clarifier and may be especially noticeable at high return
sludge flow rates. When this type of straggler floe is observed
while the final effluent is otherwise exceptionally clear,
and if it is present even during relatively low discharge
periods, sludge age should be increased. Since this type of
straggler floe usually occurs at relatively low mixed liquor
solids concentrations and is usually worse during the early
morning hours, it may be reduced by cutting back on sludge
wasting rates 10-20 percent. This will increase sludge age.
Return sludge and air discharge rates are controlled by re-
sults calculated from other control tests.
Pin Floe: Very small compact pin floe, usually less than
1/32 of an inch (0.8 mm) in diameter, may be observed sus-
pended throughout moderately turbid final clarifier tank con-
tents. This is a strong indication that sludge age is too high
and the sludge has become overoxidized. This results from
high return rates which cause the sludge to make too many
passes through the aeration in a days time.
The settlometer test will confirm this if rapidly-settling,
discrete sludge particles appear as individual "grains" or gran-
ular rather than clumping together. The sludge tends to
accumulate rather than compact while forming a settlometer
sludge blanket. In essence, granular sludge particles are fall-
ing through a turbid liquor rather than compacting and
squeezing out a clear final effluent. When final clarifier
characteristics are confirmed by the settlometer test, the
sludge wasting rate should be increased while return sludge
flow is adjusted to meet other control test demands.
The Return Activated Sludge (RAS) condition should
be observed as it discharges into the aeration basin. A good
RAS has a brown color, no offensive odor and good settling
in the clarifier prior to pumping to the aeration tank.
1-7
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What are the causes of
a septic RAS?
Is the pump operating
correctly?
Is return sludge measured?
WASTE SLUDGE
Watch the wasting
operation closely.
A black and odorous sludge indicates that it has turned
septic. Two possible causes are an excessively low rate of
sludge return and not enough air supplied to the aeration
basin. The first results in the sludge remaining in the clarifier
too long and since it doesn't receive aeration, the sludge
turns septic/ The aeration basin should be checked for .
dissolved oxygen to see if low DO (less than 0.5) is the cause.
Sludge should be returning from the clarifier all the time
unless it is necessary to shut it off to waste and then only for
short periods of time (1-2 hours maximum). Material that
blows into the clarifier may plug the suction line. This re-
quires rodding out or blowing back with air or water.
Air lift pumps may not operate because the air line con-
trol valve vibrates shut. Valves should be checked each time
the operator passes them. Handles and stems should be ad-
justed so they are tight and not knocked out of adjustment
by bumping or vibration.
The meter or measuring device for return sludge should
be read and a record kept on rate of return as well as total
pumped each day.
Float type meters need to be checked daily to be sure
nothing interferes with free operation of the float. Grease
and sticks sometimes cause the float to stay in one place
regardless of the flow, causing false readings.
Weirs that measure flow must be kept clean. Grease,
weeds, trash, or thick sludge that collects on the weir edges
will cause falsely high readings. The weirs should be checked
and cleaned daily.
Many small plants were never provided with a way to
waste sludge nor a place to waste it to. Several suggestions
are made in later portions of this manual to solve this
problem.
Other plants have methods of wasting either on a batch
basis or continuously to an aerobic digester or to a holding
tank. It is generally the best practice to waste only while the
operator is on site to watch the operation. It is important
to calculate the amount needed to be wasted and then to be
sure not more than that amount is drawn out. When waste
valves are left open overnight it is too easy to either waste
too much or something plugs the line up and nothing is
wasted.
Valves, meters', and pumps used in the wasting proce-
dure should be checked at least every other hour when in
use.
1-8
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TOTAL SLUDGE LOSS
Oops!
Getting back in operation.
Borrow
Start from "scratch"
Sometime, the operator may come to the plant and find
that all or most of the solids have been washed out or wasted
from the plant. The two most probable causes are hydraulic
washout due to high flows or accidentally leaving a valve
open.
In either case, it will be necessary to start over and build
new activated sludge. Several options are available:
1. Check with a neighboring activated sludge plant and
see if some return sludge can be hauled in and
dumped in the aeration basin. By using 5,000
gallons of return sludge at a concentration of 10,000
mg/L in an aeration tank holding 50,000 gallons,
an instant MLSS of 1,000 mg/L would result.
2. If the plant has an aerobic digester or holding tank,
some of these solids could be transferred to the aera-
tion tank. The bugs will not be as healthy but it
will cause the process to come back faster than start-
ing from "scratch."
3. If it is necessary to start from nothing, it can be
done by setting the return rate at maximum for 2-3
days and stopping wasting until the proper level of
solids are built up. There will probably be foaming
in the aeration tank and chemicals may be needed
to keep it down. Also, a lawn sprinkler can be set
up to spray over the surface of the tank.
It may take 8-12 days to get back to normal.
Return rates should be cut back at about 10 percent
per day after the first 3 days. No wasting should be
done until back to normal.
One other problem might result in sludge loss and this
may be due to "toxic" or poison materials coming to the
plant. Metal wastes, high organic content, or low or high pH
are some of the possible causes. The sludge may lose its
ability to settle and go out over the weirs.
The source must be found immediately and stopped.
This requires the help of regulatory people usually.
Plant startup may be done in any of the above ways after
the problem is found and corrected.
1-9
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SECTION 3
TESTS AND INTERPRETATIONS
Listed below are sampling locations and tests that can
be performed at a treatment plant. The list includes both
those for operational control of the plant and are used to
confirm conditions suspected in plant observation, and those
that measure the efficiency of the treatment system and are
used for reporting to the state regulatory agency. The tests
indicated in bold type are those for which the procedure is
described in Section 6.
Raw
Wastewater
BOD5
Suspended
Solids (SS)
pH
Temperature
Flow
Pretreat-
ment
None
Aeration
Tank
Mixed Liquor
Suspended
Solids
(MLSS)
Centrifuge
Settlometer
Settleability
PH
Dissolved
Oxygen (DO)
Temperature
Clarifier
BODs In/Out
SS In/Out
pH In/Out
DO In/Out
SS of Return
Sludge
Settleability
Turbidity Out
Chlorine
Contact
Chamber
Residual Out
*BOD5Out
SSOut
Bacteriological
Out (Fecal
Coliform)
*Dechlorinate sample and reseed before running test.
SETTLEABILITY
Purpose
Those tests for which the procedure is not covered in
Section 6 can be found in detail in the references listed at the
end of Section 3.
Following is a discussion of the above tests and how
they applied to treatment plant operation.
This test is conducted daily to assist the operator in
routine process control and identification of specific prob-
lems. It involves obtaining samples from the aeration tank
and clarifier setting them at within five minutes of collection
and allowing the samples to settle for a 30- or 60-minute
period.
1-10
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Interpretation
Well-Operating Plant
Poorly Operating Plant
1. Mixed Liquor
a. Sludge vyill be dense/and'will stay settled for at least
one hour.
b. Sludge reading should be about 50-70 percent at
5 minutes, 35-50 percent at 30 minutes, and 30-40
percent at 60 minutes. At about 30 percent at 1
hour, the foam,in aeration tank begins to increase
and turns white and color of tank contents gets
lighter.
NOTE: These figures are typical values and will
•vary from plant to plant.
c. Supernatant should be clear.
2. Settling Tank Effluent
a. Clear and solids free.
b. Slight "dusting" of sludge on bottom of jar.
c. Light solids suspended in a clear supernatant.
1. Mixed Liquor
a. Turbid settling vessel supernatant, black sludge,
and odor (plant not getting enough air).
b. Reddish color (overaeration).
e. Solids in jar rise within an hour after settling
(overaeration).
d. Settleability after 5 minutes either above 80 percent
or below 40 percent.
2. Settling Tank Effluent
a. Turbid settling vessel supernatant (sludge is being
mechanically torn apart in clarifier, or the sludge has
gone septic due to remaining in clarifier too long.
Sludge return line may be plugged).
1-11
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Settlometer Tests
Purpose
Interpretation
Ideal Curve
This daily test is to observe sludge quality and to give
the operator advance warning of the need to change process
control. It is more informative than the previously
mentioned settleability test.
Plot th'e sludge settling data as shown in Example Curve
No. 1. A blank form is included in Appendix D for copying.
A typical plant that is operating properly should develop a
similar curve. In each plant, a particular curve will occur
when all phases of the plant are operating well; i.e., clear
effluent, good settling .in the clarifier, proper color. This
curve, reflecting good.operation of the plant, becomes the
curve that the operator strives to maintain.
1000
Example Curve No.1
100
5 10 15 20 25 3O
40
50
60
SLUDGE SETTLING TIME (MINUTES)
1-12
-------
1000
Example Curve No. 2
ACTUAL PLANT CURVE
Young Sludge
5 10 15 20 25 30
SLUDGE SETTLING TIME (MINUTES)
When the curve tends to rise from the ideal plant curve,
as depicted in Example Curve No. 2 (usually accompanied
by excessive white sudsy foam in the aeration basin), the
sludge age is probably young and the return sludge rate
from the clarifier should be adjusted. This is usually done in
steps of 20 percent increase at one time. This also should be
accomplished by decreasing the sludge wasting from the
•system and reducing the air into the aeration basin.
Possible causes of this condition are: too great or too
fast a removal of sludge from the system or high organic load.
1-13
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1000
Example Curve No.3
Old Sludge
5 10 15 20 25 30
SLUDGE SETTLING TIME ( MINUTES)
When the resulting curve drops down from the ideal
plant curve, as depicted in Example Curve No. 3 (usually
accompanied by thick, scummy, dark tan foam), the sludge
age is considered to be too old and the operator should begin
to increase the sludge wasting rate. (See the topic on Obser-
vations: Aeration Tank, of Section 2 for information on
sludge wasting.) Possible causes are: reduced organic
loading, too high a return rate from the clarifier, long periods
of overaeratiori, and retaining old sludge for long periods of
time.
1-14
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Graphing Lab Results
These day-to-day curves may be combined into a weekly
or monthly graph as in Example Curve No. 4 (Appendix E
contains a blank form for copying) along with additional data
from flow, BODg, or just the operator's observation of the
clearness of the supernatant. A scale could be made from
0-10 with "0" being a perfectly clear supernatant after 60
minutes of settling and 10 would represent a very murky
liquid. This will give the.operator a graphic view of the pos-
sible causes for changes in the process. The operator should
then be able to know the limits of the plant, such as when a
certain hydraulic surge or flow will cause solids loss and how
long it takes to cause the' loss, or at what MLSS level range
does the clarifier perform well. It should also enable the
operator to answer questions regarding the plant's ability to
accept additional loads connected to the plant.
DAILY SETTLEABLE
RESULTS AT M MIN.
DAY OF MONTH
CENTRIFUGE FOR
SUSPENDED SOLIDS
Purpose
The settlometer test concept of operational control is
explained in EPA bulletins available from the National Train-
ing and Operational Technology Center.
This is a quick method of estimating the mixed liquor
suspended solids concentration.
1-15
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Interpretation of Results
pH TEST
Purpose
Interpretation
RESIDUAL CHLORINE
TEST
Purpose
Interpretation
If the suspended solids concentration is above or below
the desired range, then the proper changes in the pumping
rate of the waste and return sludge should be made. Part II,
Section 2, gives ranges of mixed liquor suspended solids
ranges for different types of treatment processes.
This daily test is used to determine the acidity or alka-
linity of the wastewater, both the raw waste and mixed
liquor.
A "neutral" pH is 7. Below that, an acidic condition
exists and above 7 alkaline conditions exist. The most favor-
able pH for a biological system is between 6.5 and 7.5, but
the aeration basin may have a range of 5-8. Extreme changes
in raw waste pH may indicate an industrial spill. If the pH
does change abnormally, it can be corrected by adding
certain chemicals. The state regulatory official or the oper-
ator's consulting engineer should be contacted for
instructions.
pH change not related to industrial spills may be
observed. A low pH following clarification may indicate
that the sludge is remaining too long in the clarifier. A low
pH after chlorination may indicate overchlorination which
results in the formation of hydrochloric acid. A chlorine
residual test should be made to confirm any suspicion of
overchlorination.
Low pH in the mixed liquor in plants with high'sludge
age may be caused by nitrification depleting alkalinity,
particularly if the alkalinity of the raw waste is low (less than
100). Sodium bicarbonate may be added without causing
problems. Check with your consultant or regulatory
personnel.
This daily test is used to determine if the chlorinator is
operating at a level to kill the bacteria before discharge of the
wastewater.
The chlorine residual will typically be between 0.5
-------
OTHER TESTS AND
MEASUREMENTS
In some cases, the operator may need to make more.
in-depth tests to tell how well the plant is working. Possibly
these tests will be handled by an outside contractor. If not,
three publications that will provide detailed information on
how to perform: these and other tests are listed under
References at the end of this section.
Flow
BODg (5-Day Biochemical
Oxygen Demand)
Flow may be recorded in gallons per day (gpd), million
gallons per day (mgd), liters per day, and cubic meters per
day. Flow information'is critical to the operation of the
plant. The operator should have a flow recorder that is cap-
able of giving the flow at a particular instant and the total
flow over a definite time period. The flow is sometimes read
from an indicator and may be recorded on a strip chart or
circular recorder which continuously plots the flow through
the treatment plant. This knowledge is helpful in finding at
what part of the day the treatment plant is receiving the high
and sometimes troublesome flows. If the meter has a
totalizer, the-reading should be written down daily and the
reading.for the previous day subtracted from it to get the
total flow in 24 hours. By adding these figures and dividing
by days in the month, the average flow is found.
Another method to find average daily flow for the
month is as follows:
Avg. Daily _ Total Flow, Beginning - Ending Reading
Flow 'Number of Days in Recording Period
gpd (Liters or Cubic Meters per Day)
Daily records of the meter reading should be kept. It
is important to take the reading at the same time each day.
These daily records are important in determining the cause of
changes in treatment plant efficiency and can be used as
shown in the settlometer test. A blank form is included in
Appendix F for copying and using.
For more detailed information on different methods of
ffow measurement/consult the Sacramento Manual listed'at
the end of this section.
This test is a measurement of the amount of oxygen
required in a 5:day period by the microorganisms'irvconsurn-
ing the organic material in the wastewater. BODg is used to
present historic information on the efficiency .of the treat-
ment system in reducing the oxygen demand of the waste-
water/ The test is'usually run on both the influent and
effluent. Long-term trends can be observed by studying
BOD5 results.
1-17
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Suspended Solids (SS)
Temperature
Mixed Liquor Suspended
Solids (MLSS)
Dissolved Oxygen (DO)
Bacteriological
References
This test measures the amount of solids that are either
floating on the surface or in suspension with the wastewater
SS tests are usually run on the influent and effluent. When
used to take the suspended solids of the aeration tank, it is
referred to as the Mixed Liquor Suspended Solids (MLSS).
The temperature of the aeration tank contents should
be taken daily by reading the thermometer while it is
submersed in the water. Temperature affects the efficiency
of the biological process. Proper recording of the tempera-
ture aids the operator in detecting long-term trends. Rapid
downward changes during rain storms may also indicate
infiltration.
The test for MLSS measures the amount of solids in the
aeration basin which, in turn, gives an indication of the
amount of bugs there are. The activated sludge process is
controlled by maintaining certain levels of MLSS. Part II,
Section 2, gives typical values of MLSS levels.
Dissolved oxygen can be read directly by using a meter
or by the Winkler titration test. It is important to maintain
proper DO levels in the aeration basin for an activated sludge
process to work. Possible suppliers of DO meters are Yellow
Springs Instrument Co., Yellow Springs, Ohio 45387; or
Weston and Stack, 446 Lancaster Avenue, Malvern, Penn-
sylvania 19355.
The success of disinfection is determined by bacteriolog-
ical tests on the effluent of the chlorine contact chamber.
This is usually done by determining the amount of fecal coli-
form bacteria in the wastewater. Note that samples collected
for these tests must contain sodium thiosulfate to destroy
residual chlorine at time of sampling.
1. Simplified Laboratory Procedures for Wastewater Exam-
ination. 1976 (Second Edition) by the Water Pollution
Control Federation, 2626 Pennsylvania Avenue, Wash-
ington, D.C. 20037.
2. Operation of Wastewater Treatment Plants. By Ken
Kerri of the Sacramento State College Department of
Civil Engineering (commonly known as the Sacramento
Manual),
1-18
-------
3. Standard Methods for the Examination of Water and
Wastewater. Published by American Public Health
Association, American Water Works Association and
Water Pollution Control Federation.
4. Methods for Chemical Analysis of Water and Wastes.
Environmental Protection Agency, National Research
Center, Analytical Quality Control Laboratory, Cincin-
nati, Ohio 45268.
5. Self-Monitoring Procedures for NPDES Permits (Student
Reference Manuals). EPA National Training Center,
Cincinnati, Ohio 45268.
1-19
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SECTION 4
OPERATIONAL PROCEDURES
PRETREATMENT
AERATION BASIN
Conventional and Extended
Aeration Activated Sludge
How is the correct amount
of oxygen maintained?
Plow can DO be varied?
Pretreatment facilities, the comminutor, bar screen,
and/or grit chamber operate without any daily adjustment
provided they are maintained according to the information
given in the sections on Plant Checklist and Observations and
according to manufacturer's recommendations.
All walkways in the pretreatment as well as other areas
should be kept clean and free of grease.
One of the keys to proper activated sludge operation is
maintaining the correct Dissolved Oxygen (DO) concentra-
tion throughout the aeration basin. Air can be added by the
two methods discussed in Part II—Section 3, Diffusers and
Surface Aerators. Two items are beneficial in insuring that
the aerators supply the correct amount of oxygen. These are
a timer and a method for measuring DO. The amount of
oxygen that the treatment system needs varies throughout
the day due to the changing flow into the plant. A blower .
supplying air to diffusers or a surface aerator may be
connected to a timer so that air can be regulated as needed.
The DO measurements are used to verify the settings on the
timer. A possible operating scheme for a municipality or
residential area is as follows:
7 a.m. — 9 p.m.:
9 p.m.- 2a.m.:
2 a.m. — 7 a.m.:
Blower or Aerator On All the Time
On 15 Minutes, Off 10 Minutes
On 10 Minutes, Off 10 Minutes
A DO reading should be taken at 8 a.m.
If above 4.0 mg/L, cut back on the air at night.
If below 1.0 mg/L, increase aeration time at night.
Besides the normal daily variations in flow, other major
effects on the operation of the aeration basin are:
1-20
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How is the effect of
hydraulic overload reduced?
What should the operator
do if it is suspected that
someone is dumping a strong
waste into the sewer?
Where do grease and fat
problems originate?
1. Hydraulic overload (flow is greater than that for
for which the plant is designed) which may be due
to a growth in the service area of the treatment
plant or to infiltration into the sewer lines during
storms and high groundwater levels. The etfect can
be reduced by installing a surge basin ahead of the
treatment plant to equalize the flow throughout the
day. A representative of the state regulatory agency
or the consulting engineer should be consulted for
assistance before building a surge basin.
2. Organic overload usually occurs during the 7 a.m. to
9 p.m. period when the treatment plant is already
receiving its heaviest load and someone dumps a
strong waste into the sewer. If this is suspected,
the operator should make a survey of places such as
schools and other institutions to see if food waste,
dishwashing water, and/or shower drainage is enter-
ing the sewer at the same time. If so, the problem
should be explained to institution officials and alter-
natives suggested. These might include scheduling
dumping during low flow period or installing a hold-
ing tank to allow waste discharge to be spread over
longer periods.
3. Slug loads, such as cooking fat or oil, can cause
problems because the bugs may not be able to use
it as food fast enough. It can also be unsightly and
odorous. Restaurants and large institutions should
be checked as possible sources of fat. Motor oil may
also come to the plant from service station sumps
that are illegally connected to the sewer system.
4. The amount of activated sludge returned to the aera-
tion basin is important to having good treatment.
Return sludge pumps should be properly maintained
and the settlometer test (see Part i—Section 3 and
6) should be run daily to tell if the sludge is settling
properly.
5. Sludge should be periodically wasted to maintain
the proper balance in the system. The settlometer
test and amount of solids in the system should be
used to gain information on when to waste.
1-21
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Contact Stabilization
Why is the reaeration basin
run at higher solids levels?
CLARIFIER AND RETURN
ACTIVATED SLUDGE
What happens when the
clarifier is disturbed by
high flows?
The operational procedures for contact stabilization
are similar to those for the conventional and extended aera-
tion activated sludge processes except that the sludge is re-
turned to a reaeration (stabilization) basin prior to passing
to the aeration (contact) basin. (See the Basics, Section 2.)
For the reaeration basin, complete mixing and dissolved
oxygen must be maintained. A DO level between 1.0 and 4.0
mg/L is an average range.
The settlometer centrifuge tests should be used to
control the solids levels in the contact and reaeration basins.
The reaeration basin should be run at higher solids levels
(3-6 times) than that in the contact basin. This allows the
operator to increase the rate of return solids to the contact
basin during the daytime period when the load or strength of
the wastewater is greatest. Prior to leaving at the end of the
day, the operator should then reduce the return flow to the
contact tank.
Because the solids in the reaeration basin are not
affected directly by the flow into the plant, only by the rate
of return, the danger of losing solids during high flows is
much less. The contact'tank removes the food by settling,
the sludge is returned to the reaeration tank where the bugs
have more time to use the food.
All visual observations regarding the aeration basin in
Section 2 also apply to the contact and reaeration basins,
however, it is normal to have more thick foam on the reaera-
tion basin because of the normally higher solids content.
The key to good clarifier performance is maintaining •••
calm conditions so that the solids will settle to the bottom.
Two things that might upset these calm conditions are:
1. Too high a sludge return rate (over 100 percent
of influent rate) tends to disturb the sludge blanket
at the bottom of the clarifier and causes solids to
rise and flow over the effluent weir. The rate should
be set to maintain the concentration found after
1.5 to 3.0 hours settling in the settlometer when the
plant is producing clear effluent.
2. If a plant is operating at or near its hydraulic capac-
ity, the wastewater isn't detained as long in the
clarifier and the efficiency of the settling is affected.
Continuous operation of the scum skimmer could
provide enough additional turbulence to further
hinder settling. If such is the case, the operator
should try operating the skimmer just often enough
to keep from losing scum in the effluent.
1-22
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What is the effect of too
slow a sludge return?
WASTING PROGRAM AND
DIGESTION
What is sludge age?
How should changes in
sludge wasting be made?
What test should be made
to give information on
sludge wasting?
How is sludge wasted in
plants without provisions
for such?
The return activated sludge should be pumped either
continuously at a steady rate or at regular intervals. Care
must be taken not to pump the sludge so fast that it becomes
too thin or disturbs the clarifier. Neither should it be so slow
that the sludge blanket builds up.
In a rectangular clarifier, the operator might experience
sludge building up in the corners and turning septic. If
such is the case, the operator may have to scrape the corners
daily with a long handled scraper so that the sludge will be
picked up by the return sludge pump.
All activated sludge plants build up excesss sludge and
require periodic wasting. Control tests, such as the settlo-
meter and MLSS solids, should be used to determine when
and how much to waste. All wasting should be done in small
amounts, not more than 20 percent of the total sludge
volume per day until the desired level is reached. Larger
waste amounts may upset the balance maintained by the
biological system.
Sludge age, which is controlled by the sludge wasting
rate, indicates the approximate number of days that an aver-
age activated sludge "bug" remains in the system before
being wasted. Too much sludge wasting will reduce sludge
age by increasing the relative amount of newly developed floe
in the system. If wasting rates are too low, it will increase
the number of days the sludge is kept in the system and will
increase the relative amount of older sludge.
Sludge wasting rates should be reduced gradually on a
day-to-day basis to correct the problem of excessive white
foam. Best results are usually found by reducing the wasting
rate approximately 20 percent of return flow on each succes-
sive day until the mixed liquor is back to normal. When
things are correct, the operator should keep the lowered
wasting rate for about three more days to allow the sludge to
stabilize. The operator should plot volume settled sludge
and sludge settling time on a graph as shown in Section 3—
Settlometer, which will alert him or her to future control
adjustments that may be needed. Wasting usually should not
be stopped completely. When sludge is settling very poorly
and sludge is bulking at the same time white foam is forming,
it may be corrected by reducing the air feed rate to 1.0
mg/L or less DO.
Following is a method for wasting sludge from plants
without an aerobic digester or holding tank: Shut the return
sludge pump off but still allow the mixed liquor to flow to
the clarifier. This action concentrates the solids in the
bottom of the clarifier. The volume of sludge should then
1-23
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How does the operator
determine the amount of
sludge to waste?
Plants With Aerobic
Sludge Digestion
be estimated by the depth of the sludge layer. A portable
pump or an adapter on the return sludge line could be used
to transfer the sludge to a tank truck for hauling to an
approved site designated by the regulatory agency. In some
cases, a drying bed might be constructed on site. Assistance
should be obtained from a consultant and the regulatory
agency.
As suggested above, this method of sludge wasting is
possible if the plant is equipped with an air lift return sludge
pump. A plugged tee can be placed in the eductor pipe as
shown in Part III—Section 1, Case Histories. When it is time
to waste, the valve on the line leading to the aeration basin is
closed and a line for the waste sludge is connected at the tee.
Listed below are formulas that allow the operator to
calculate how much to waste each day.
1.
% Sludge Vol. =
Actual Depth of Sludge
in Feet
Depth From Bottom of
Tank to Water Level in
Feet
x(100)
2. Maximum Amount of Sludge to Waste Per Day
_ (Actual Depth of Sludge in Feet) x 2
10
3. After the desired amount of sludge is pumped out,
the return pumps are turned on and normal opera-
tion is resumed. This operation should be done
when flows are low and should not take over two
hours.
As with the aeration basin, the key to digester opera-
tion is maintaining a proper dissolved oxygen concentration,
in this case around 1 mg/L.
Other important items in operation are:
1. To allow room for added sludge to the digester, the
aeration is turned off, and the solids are allowed to
settle (usually takes one to two hours). Part of the
supernatant is then pumped to the aeration basin
and mixed with the wastewater being treated.
2. Solids levels that will still allow good settling should
be maintained in the digester. At high concentra-
tions (possibly above 10,000 to 20,000 mg/L) the
solids do not separate from the liquid. Therefore,
1-24
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Plants Without Aerobic
Sludge Digestion
What advantage does a
temporary storage tank
for sludge offer?
DISINFECTION
How does the operator
verify one hour detention?
while the aeration devices are turned off, enough
sludge should be removed to maintain a proper
solids level.
Disposal of the digested sludge should be on land or
drying beds as approved by the state regulatory
agency.
Package treatment plants without sludge digestion have
to obtain other methods to handle sludge. If the plant is
not designed for wasting, a septic tank pumper may be used
to pump the sludge out.
Disposal of the sludge must be at an approved site.
This might be a sludge stabilization lagoon, a drying bed or
land disposal. If a nearby treatment plant has the capacity,
arrangements might be made with that operator to handle the
sludge.
Many plants find it difficult to get a septic tank hauler
to pump a small amount of sludge at frequent intervals. A
solution would be for the operator to obtain a 5,000-gallon
(19 cubic meter) tank to store the sludge. Enough air would
have to be provided to maintain aerobic conditions and pre-
vent odors. Then, at less frequent intervals, the septic tank
hauler would empty the storage tank.
Disinfection of the wastewater, usually by chlorine,
must be a continuous process. To determine the level at
which to set the chlorinator, chlorine residual tests should be
run as described in Part I—Section 6, Laboratory Procedures.
The following items are important to effective and safe
operation of the chlorinating facility:
1. A detention time, generally one hour, is necessary
to allow the chlorine to contact and kill the
bacteria. One hour detention and effective mixing
can be verified by adding dye at the point of
chlorine discharge and check the time required for
the majority of the dye to appear in the effluent.
It may be necessary to install baffles as shown in
the drawing of the chlorine contact basin in Part II —
Section 3.
2. Replacement chlorine containers should be
connected so that gas supply will not be interrupted.
The amount of chlorine used should be recorded
daily in order to know when to switch containers.
1-25
-------
How does the operator
check for chlorine leaks?
CHEMICAL ADDITIONS
Why is it disadvantageous
to use chemicals?
Are enzymes a good buy?
3. The chlorine piping should be checked daily for
leaks. Chlorine will cause an ammonia water soaked
cloth to give off a white cloud of ammonia chloride.
Chemicals have been used occasionally for temporary
relief of problems in biological treatment systems. Alum,
ferric chloride, and polymers are sometimes added to the
clarifier to assist in settling. When chemicals such as alum
are used, they will increase the volume of return sludge and
may reduce the pH of the sludge.
Chlorine is used to reduce the odors from septic influent
wastewaters. Care must be taken not to chlorinate the in-
fluent to a level that will kill the bugs in the aeration basin.
A proper dosage, to be added over a 24-hour period, is 1/2
pound chlorine for every 10,000 gallons of wastewater
(6mg/L).-
Bicarbonate of soda may be used to raise pH in the aera-
tion basin. A guideline for the amount to add is to maintain
a minimum of 25 mg/L bicarbonate alkalinity. The
procedure for running the alkalinity test is in Standard
Methods and Simplified Laboratory Procedures cited in the
Bibliography in Appendix A.
The pH will vary some during normal wastewater treat-
ment. A sudden rise or drop may indicate an industrial dis-
charge and it is often too late for any pH control to save the
bugs. If a plant has persistent problems with pH, a state regu-
latory official should be contacted for technical assistance in
regard to pH control. Efforts should be made to eliminate
the cause at its source through the use of city ordinances
prohibiting the dumping of strong acidic or basic wastes.
There has been much discussion over the use of en-
zymes in the aeration basin. In specific instances, enzyme
addition may be helpful to treatment, but only after labora-
tory testing to determine which type would be effective.
Due to the high cost of enzymes and their controversial
nature, it is suggested that before making a decision concern-
ing enzymes the operator read the article by James C. Young,
entitled "The Use of Enzymes and Biocatalytic Additives
for Wastewater Treatment Processes." (Deeds and Data,
May 1976, Water Pollution Control Federation.)
1-26
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SECTION 5
FINAL PLANT SURVEY
Before leaving for the day, one final inspection should
be made around the plant. The following questions may help
in seeing that the operator has left the plant in a condition
that it will operate well until the next time it is attended.
1. Are there any pieces of equipment that are running
poorly that may have to be checked before the next
scheduled day of operation (hot bearings, loose
belts, etc.)?
2. Are return sludge rates set at correct level?
3. Are f lowmeters clean and operating?
4. Are inlet gates set properly in case of high flows
before the next plant visit.
5. Are air flow rates set properly?
6. If some processes are time-clock controlled, are time
clocks set?
7', If remote alarms are used to warn someone about
power or equipment failures, are these set to turn
on?
8. Is equipment stored and locked so as to prevent
vandalism?
9. Are outside lights on or set to come on?
TO. Is plant secured to prevent vandalism?
1-27
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SECTION 6
LABORATORY PROCEDURES
SETTLEABILITY
Purpose
Equipment
Following are the laboratory procedures for the tests
that are discussed in detail in Section 3.
This test is conducted daily to assist the operator in
routine process control and identification of specific prob-
lems, using one of the following:
1. Quart or liter jars (clear glass) marked with a scale
from 9-10.
2. Graduated glass cylinders (1,000 milliliter capacity).
OR
3. 2-liter beaker.
-1000-
500—
OR
1-28
-------
Procedure
1 Fill the container with mixed liquor (liquid from aera-
tion tank).
It should be filled to the upper mark on the scale.
NOTE: A more informative test on the mixed liquor
is the Settlometer test described later.
2. Let container sit for 60 minutes.
3. At 5, 30, and 60 minutes note:
a. Mixed Liquor
(1) Scale reading at top of settled sludge.
(2) Density of sludge (thick or light).
(3) Clarity of supernatant (clear or cloudy).
— 1OOO —
500-
SUPERNATANT
125
2.5
SETTLED SLUDGE
1-29
-------
Example Calculations
Sludge Scale Reading
Glass Jar
(scale reading) x (10) = % sludge volume
Example:
(2.5) (10) = 25% sludge volume
1,000 ml Graduated Cylinder:
(scale reading) = 0/o s|udge vo|ume
Example:
250
-.= 25% sludge volume
10
3. 2-Liter Beaker Marked From 0-1,000:
(scal* r0eaging) x 100 = % sludge volume
Example:
250
1,000
x 100 = 25% sludge volume
SETTLOMETER TESTS
Purpose
Equipment
Procedure
This daily test is to observe sludge quality and to give
the operator advance warning of the need to change process
control.
One glass container equivalent to the five-inch (13 cm)
diameter, six-inch (15 cm) depth, two-liter Majlory "Sett I-
ometer" that is graduated in hundreds is needed. The equip-
ment is obtainable from laboratory supply houses such as
SGA Scientific, 2375 Pratt Boulevard, Elkgrove Village,
Illinois 60007
1. Fill'the container to the upper mark on the scale with a
sample frorn the aeration tank with the least possible
amount of additional aeration or disturbance. For con-
tact stabilization, tests should be run on both the con-
tact and reaeration tank,
2. Stir contents gently and then dampen immediately with
a wide paddle before starting timer.
1-30
-------
3. Read and record the volume occupied by the settled
sludge every five minutes for the first 30 minutes and at
10-minute intervals for the second 30 minutes of the
one-hour test.
4.
NOTE: During the first five minutes, the operator
should observe how the sludge particles come together
while forming a blanket on the bottom.
Does the sludge compact slowly and uniformly while
squeezing clear liquid from the sludge mass? This is
an indication of good sludge.
Do tightly knotted sludge particles fall down through a
turbid supernatant? This indicates an old sludge in poor
condition.
How much and what type of floe (sludge particles) if
any, remains in the supernatant above the main sludge
mass? Note types on daily log.
At 60 minutes the sludge characteristics should again be
noted as this will show what the sludge will do in the
clarifier. A sludge that starts rising again by the 60-
minute time may be overoxidized.
NOTE: A properly oxidized sludge will not start rising
to the surface until two to four hours after the test was
started.
CENTRIFUGE FOR
SUSPENDED SOLIDS
Purpose
Equipment
Procedure
This is a quick method of estimating the mixed liquor
suspended solids concentration.
1. Laboratory centrifuge with speed control.
2. Graduated centrifuge tubes, standard API calibrated
0-100 percent, 0-15 ml, or 0-30 ml.
1. Collect sample in regular sampling can.
2. Mix sample well and fill each centrifuge tube to the top
line with sample and place in centrifuge holders. If the
machine will handle four tubes, use two for MLSS and
two for RAS.
1-31
-------
3. If centrifuge is hand powered, crank at a fast speed
while counting slowly to 60. Count and crank at the
same speed for all tests. The most accurate ones are
motor driven. Use maximum speed for 15 minutes if
motorized. In either case, it is extremely important to
perform each step exactly the same every time.
4. Remove tubes and read the amount of suspended solids
concentrated in the bottom of each one. This reading
will be in percent or tenths of a milliliter. Average the
values if two or more tubes are used.
5. Refer to conversion graph to determine suspended solids
in mg/L.
NOTE: Graph must be developed for each plant, This
can be done by taking a sample from the aeration tank
and measuring suspended solids by the regular Gooch
Crucible Method or membrane filter and centrifuging a
portion of the same sample to obtain the centrifuge
sludge reading in ml of sludge at the bottom of the tube.
Keep records on other samples at different solids con-
centrations to obtain the points on the graph, as shown
in the following example. Draw a line of best fit
through the points. With each major change in weather
or sludge condition, the points should be checked be-
cause the influent characteristics and conditions in the
aeration tank change (approximately every two to
three months).
01 0.2
UJ
5
It
1
1
18
E
~
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5
C
(A
C
S
API
US
Et
MP
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>
IPLES MEASURED FOR
PENDED SOLIDS AND
LE<
TRIFUGE SLUDGE READING
PENDED SOLIDS = 700 m
1 |
S
_IN
-
E
S
OF
-
S
ffr
-
rl-
E
*
T
^
F
T-
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—
^
-
= 0.3ml
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-
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*•
—
3
-
r
~
^.
**
s
•*
-
^--
-4— ,
~|-
-
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—
^
-
-
-
-
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-
-
-
-j-
--
200
300
400
500 600
SUSPENDED SOLIDS
700 800
(my/1.1
900 1000
1-32
-------
pH TEST
Purpose
Equipment
Procedure
This daily test is used to determine the acidity or alka-
linity of the wastewater, both the raw waste and mixed
liquor.
NOTE: The following test uses color comparison and
will not be allowed by U.S. EPA for NPDES reporting. The
procedure is included for use for process control as a handy
tool. A pH meter, when purchased, should come with com-
plete instructions for its use, therefore, no instructions are
presented here.
1. pH comparator
2. Brom thymol blue indicator
3. Eye dropper with a 1 ml mark on glass tube
1 . Obtain a fresh sample of raw waste.
2. Fill the tubes with a portion of the sample.
3. To one tube add the amount of indicator recommended
on the pH disc.
4. Place tube with indicator in the opening behind the
clear glass.
5. Place tube without indicator in the opening behind the
colored disc.
6. Compare colors by rotating the disc. Read the pH of
the indicator having the color closest to the sample
color.
NOTE: Some comparators have standard color solu-
tion vials instead of the disc. If so, change vials until
color matches.
7.
8.
Wash and dry sample tubes.
Repeat procedure using supernatant from a sample of
mixed liquor. This test should be run within 10 minutes
of collection time.
NOTE: When using an electric pH meter, a sample of
mixed liquor can be run directly.
1-33
-------
RESIDUAL CHLORINE TEST
Purpose
Equipment
Procedure
This daily test is used to determine if the chlorinator is
operating at a level to kill the coliform bacteria before dis-
charge of the wastewater.
NOTE: As with pH, color comparison will not be
allowed for NPDES reporting. A replacement test is the
starch iodide method found in the references at the end of
this section. Kits such as the Model CN 65, which make the
test easier, are availabile from Hach Chemical Co. or Bausch
and Lomb Mini-Spectronic 20.
1. Chlorine comparator (same as for pH but change the
disc for chlorine)
2. A fresh (within six months) supply of orthotolidine
reagent
3. Eye dropper with a 1 ml mark on glass tube
1. Fill tubes with liquid taken from outlet of chlorine con-
tact chamber, hold tube in hand for few minutes if
liquid is not room temperature.
2. Place one tube in the opening behind the colored disc.
3. To the other tube add 1 ml of orthotolidine and place
in the opening behind the clear glass.
1-34
-------
SECTION 7
TROUBLESHOOTING Troubleshooting begins by knowing the system. The
operator needs to know:
1. What each part of the system is supposed to do.
2. How each process or piece of equipment operates
normally.
3. How to recognize abnormal conditions.
4. What alternatives are available when trouble
develops.
Briefly, to recognize when something is bad, the
operator must know how it works when no trouble exists.
The purpose of this section is to present a ready and
quick operator's reference to process problems and their
solutions.
The table is arranged in columns as explained below:
Condition: The information in this column shows
what has been indicated or observed by the operator.
Possible Cause: This shows the most likely cause of the
indicated upset.
Solutions: The operator should arrange the suggested
solutions in the order that he wants to try them and
proceed from the easiest to the most difficult.
Reference: The numbers appearing in this column show
where in the manual the operator can find additional
information.
1-35
-------
CO
O)
TROUBLESHOOTING
Condition
Possible Cause
Solution
References
Controls
1. Pump fails to start
2. Overloads trip
3. Starters chatter
1. Overload relays tripped; starter coil damaged; HOA switch
off; blown fuse; breaker off; alternator damaged.
2. High amperage draw.
3. Starter contacts burned; dirty contacts in alternator.
1. Inspect; see "Motors," call electrician.
2. See "Motors."
3. Clean, inspect or replace contacts.
Pumps
1. Unusual noise
2. Vibration
3. Reduced pumping rate
1. Plugged impeller or suction; reciprocating pump pumping
water instead of sludge (knocking noise).
2. Plugged pump priming line; see 1 above.
3. Broken impeller; worn wear rings; see 1 above.
1. Clean intake screen; remove pump housing and unclog
impeller, turn off purnp and check clarifier sludge blanket;
too fast a pumping can suck a hole in the sludge blanket.
2. Remove and unplug line; check impeller for debris.
3. Disassemble, replace impeller; measure wear rings.
1. 1-4 Clarifier & Return
Activated Sludge
1-3, Pumping
3. 11-3, Pumping
Mechanical Seals
1. Clogged filter
1. I nnerseal leaking; bad motor bearings and vibration causing
seal failure.
1. Repair bearings and seal(s).
Motors
1. Noise and/or vibration
2. Run hot
3. High amperage
1. Damaged, broken fan vanes.
2. Excessive bearing grease; wrong type of grease; overloaded;
lack of grease.
3. Drive motor too light for head requirements; too low
discharge pressure; plugged impeller; damaged bearings; power
imbalance; high or low voltage condition; misalignment.
1. Inspect and replace, if necessary.
2. See manufacturer's recommendations to verify correct
amount and type of grease.
3. Match equipment to load. Clean and repair impeller as
necessary.
Pretreatment
1. Septic conditions upstream
of bar screen
2. Odors around bar screen
3. Leakage under drum of
comminutor
4. Organics settling out in
grit chamber
1. Infrequent cleaning causes organic material to settle out
upstream.
Comminutor not functioning properly or debris present
which the equipment cannot remove.
2. Collected screenings not disposed frequently enough.
3. Rubber seal worn or not seated.
4. Flow too slow.
1. Clean screen and flush sewer.
Divert flow. Shut unit off and remove blockage.
2. Remove screenings and bury with 6-12 inches (15-30 cm)
earth cover.
3. Inspect, adjust or replace.
4. Reduce number of channels used during low flow. Introduce
air into chamber to keep organics suspended.
1. I-2, Pretreatment
4. III-1, Equipment
Modifications
-------
TROUBLESHOOTING
Condition
Possible Cause
Solution
References
Biological Treatment
1. Turbid clarifier supernatant
(effluent)
2. Black MLSS, septic odor and
turbid supernatant
3. Black MLSS and turbid
supernatant
4. Reddish MLSS and return
sludge
5. Light brown aeration tank
liquid and thinner solids
6. Clumps of black solids on
clarifier and odorous
7. Black aeration tank contents
8. Excessive foaming
9. Activated sludge bulking
(activated sludge not
settling in clarifier)
1. Return rate out of balance.
2. Not enough air; possibly localized septic pockets due to
incomplete mixing.
3. Abnormal pH; possibly due to industrial wastes.
4. Overaerat ion, check DO to verify.
5. Insufficient sludge return.
6. Solids remaining too long in clarifier and septic conditions
occurring; sludge return line possibly plugged. Sides of
hopper-type clarifier not scraped frequently enough.
7. Septic conditions.
Too much activated sludge solids wasted at one time;
insufficient air during high "storm" flows; plant recovering
from overload or septic conditions; overaeration.
9. Too low solids level in system; strong stale septic sewage
received after a storm following a long dry spell; poor grease
trap cleaning (restaurant wastes); alkaline wastes from a
laundry.
1. Adjust sludge return rate to match 1.5-3 hour settling
concentration.
2. Increase air supply. Check and clean diffusers.
3. Check pH. Add acid or sodium bicarbonate if pH is low. See
state regulatory official for instructions.
4. Reduceair to aeration tank.
5. Increase rate of sludge return to aeration tank.
6. Check sludge return lines for proper operation and increase
sludge return rate.
7. Increase aeration.
8. Can be controlled until eliminated by using a water spray.
Solution is generally to stop wasting until solids are back up
to normal.
9. Check solids level with settling test. Increase sludge wasting.
Increase air rate if test shows less than 0.5 milligrams per liter
Ippm) dissolved oxygen near the surface of the settling tank.
Hold approximately 1.0mg/L.
1. I-2 and 4, Clarifier
2. I-2 and 4, Aeration Tank
3. l-3andG, pH
4. I-4, Aeration Tank
I-3, DO
5. I-2, Aeration Tank
I-4, Clarifier and Return
Activated Sludge
6. I-2 and 4, Clarifier
II1-1, Equipment
Modifications
8. I-2 and 4, Aeration Tank
III-1, Equipment
Modifications
9. I-2 and 4, Clarifier
l-3and 6, Settleability
and Settlometer
Note: For more information, see "Operators Pocket Guide to Activated Sludge—Part II: Process Control and Troubleshooting." Available from Stevens, Thompson & Runyan, Inc.. 5505 S.E.
Milwaukie Avenue, Portland, Oregon 972O2. Price: $1.OO.
-------
SECTION 8
PLANT CHECKLIST ' Following is a sample operation and maintenance
schedule for a package plant. Although it is not a complete
list of everything the operator should be observing, it will
serve as a guide for setting up a schedule for his or her own
plant. The schedule will help the operator organize work in
a step-by-step fashion and it will also help relief operators
or new personnel who are not familiar with the plant. For
the design engineer, a checklist should be developed for the
plant and included in the operation and maintenance manual.
The blank form in Appendix C may be used as a guide.
Most of the items are visual observations or maintenance
needs that take little time if performed according to
schedule. With regular attendance, the operator will develop
ways to combine some of the duties. In many package plants
that are looked after regularly by a conscientious operator,
the scheduled items can be accomplished in one to two hours
a day, allowing the balance of the time for lab and other
duties.
1-38
-------
Operational and Preventive Maintenance
Inlet and Outlet Facilities
1 . Clean weirs, weir troughs and weir boxes.
2. Flush influent sewer, if possible, using
water from fire hydrant or street
cleaning water tank truck
Pretreatment
1 . Remove and dispose of rags and
accumulations from comminutor and
screens.
2. Observe flow and cutting action of
comminutor. Plugging may occur if
rags are not cut up.
3. Check for rock or metal objects in
comminutor channel.
4. Sharpen comminutor blades when
cutting edge is worn 1/8th of an inch
(0.3cm).
5. Grease comminutor, if called for in
manufacturer's instructions.
6. Check oil level of comminutor.
7. Observe air flow in grit chamber and
unclog any ineffective d iff users.
Remove rags from diffusers daily.
8. Remove scum from grit. chamber.
9. Wash down grit chamber.
10. Check grit pump packing for leakage,
(20-30 drops per minute is normal).
11. Inspect grit collection system.
1 2. Remove and dispose of grit collection.
13. Wash down entire grit collection system.
Frequency
Daily
X
X
X
X
X
X
X
X
Wk.
X
X
X
Mo.
3 Mo.
6 Mo.
Yearly
As
Necessary
X
X
X
X
1-39
-------
(Continued)
Operational and Preventive Maintenance
Aeration Basin
1 . Visually check aeration system for even
air distribution, no dead spots.
2. Raise and clean rags from diffusers.
3. Check oil level in mechanical aerator
• gear cases.
I
4. Check oil level in blower gear case's.
I.
5. Check for air leaks around base and
fittings of blower.
6. Check blower belts for wear and tension.
7. Check blower motor and bearings for
excessive heat.
8. Check aeration system for unusual noises
or vibration.
Clarifier
1 . Scrape sides and sloping bottom of clarifier.
2. Check to see if sludge collection arm is
turning.
3. Remove any floating material on top of
clarifier.
4. Verify that scum skimmer is depositing
all scurrrin hopper.
5. Pump scum box arid hose down.
6. Scrub launders and weirs with brush.
Frequency
Daily
X
X
X
X
X
X
X
X
X
Wk.
X
X
X
X
Mo.
3 Mo.
6 Mo.
Yearly
As
Necessary
X
1-40
-------
(Continued)
Operational and Preventive Maintenance
Pumps and Motors
1 . Check for blockages in RAS return pump.
2. Check pumps for clogging or near clogging
condition.
3. Clean screen at intake of suction piping
of pump.
4. Lubricate pump bearings.
5. Check pump bearings temperature. ,
6. Drain pump lubricants, wash out oil wells
and bearings with kerosene.
7. Check pump bearings for wear.
8. Check alignment of pump and motor
flange, with straight edge.
9. Check motors for heating.
10. Replace pump packing.
1 1 . Check pump shaft sleeves.
12. Replace pump shaft sleeves
13. Examine pump wearing rings (manufac-
turer should specify what is excessive).
14. Clean water seal piping.
1 5. Inspect foot valves and check valves.
Operational Controls
' 1 . Observe odor, color, and foam of
aeration tank.
2. Perform necessary operational and
control tests (settleability test, pH,
chlorine residual, etc.).
3. Perform tests as required by NPDES
permit and regulatory agency.
Frequency
Daily
X
X
X
X
X
X
Wk.
Mo.
X
3 Mo.
: I
X
X
6 Mo.
X
i-X
Yearly
X
X
As
Necessary
X
X
X
X
X
1-41
-------
BASICS
-------
SECTION 1
BASIC PRINCIPLES OF
WASTEWATER TREATMENT
Wastewater contains both suspended and dissolved
pollutants. In order to treat the wastewater, two methods
are used to get rid of these pollutants. Part of the suspended
pollutants are taken out with screens and settling, and the
rest.are biologically changed to a form that is more easily
removed.
If only physical removal is used, objects removed are
those that would float or settle under calm conditions.
Physical treatment protects the river or lake from eyesores
like floating bottles or rags that occasionally get washed into
the sewer.
2-1
-------
Smaller particles, if they are not removed, might cause
the river or lake to become cloudy or murky. These particles
may also require oxygen from the stream as they decompose.
If there are many of these particles, the dissolved oxygen
content of the stream, necessary for fish life, would be
reduced.
The other type of pollutant in the wastewater, the dis-
solved one, must be changed in form before it can be re-
moved. Fortunately, there is a character that will help us do
this. It is the microorganism, or "bug," as it is sometimes
called. The bug uses the dissolved organic material as food.
The bug can take up some of the suspended organic
material also. Material may come into contact with the bug,
attaching.to the outside. This is called adsorption. Later,
food is absorbed through its cell wall so that the food can
be digested. Oxygen from air forced into the liquid is re-
quired for the bug to function and grow so that new bugs
can be produced.
2-2
-------
ABSORPTION
When the bug has taken in the pollutants in the waste-
water, it can be removed by settling. Now the dissolved
material has been converted to a form (called sludge) which
can be removed by the physical means described earlier.
Just like you and I, the bugs need a healthy environ-
ment in which to live and grow: enough oxygen (1-2 milli-
grams per liter), the right number of bugs for the food com-
ing in, a neutral pH, a warm temperature between 59 to 95
degrees Fahrenheit (15 to 35 degrees Celsius), and enough
time to digest the food. If these conditions are maintained,
and proper sludge wasting and return sludge flow procedures
are followed, the bugs will reward us with a cleaner waste-
water. Otherwise, conditions such as too much food for
the number of bugs, high flows, lack of wasting, or too much
air may prevent the production of a good clear effluent.
THAT 5 THE
PLACE FOR US.
DEAR!
FEATURING
APLENTY or OXYGEN
NO OVCRCROWMNO
* NICE AND WARM
A LOTS Or TIME
A NEUTRAL
2-3
-------
Note: For more detailed information, see "Operator's
Pocket Guide to Activated Sludge-Part 1: The Basics."
Available from Stevens, Thompson & Runyan, Inc., 5505
S.E. Milwaukie Avenue, Portland, Oregon 97202. Price:
$1.00.
2-4
-------
SECTION 2
TYPES OF WASTEWATER
TREATMENT PROCESSES
Conventional Activated Sludge
Conventional activated sludge is one type of process
that makes use of bugs under aerobic conditions. Aerobic
means in the presence of oxygen. After the wastewater has
passed through the pretreatment process, screening, grit
removal, and comminution, it enters the activated sludge
system.
The first point of interest is the aeration tank. Here,
the wastewater is detained long enough (four to eight hours)
for the bugs to eat the organics in the wastewater. Organics
are waste materials which come from animal or vegetable
origins and can be eaten by the bugs. Oxygen and mixing
are required for the bugs to come in contact and digest or
metabolize the organics. The products are new bugs, carbon
dioxide, ammonia, and water. A Dissolved Oxygen (DO)
level between one to two mg/L should usually be maintained
in the aeration tank for this to occur.
2-5
-------
The process of the eating and digestion occurs in two
steps. First, the particle sticks to the surface of the bug.
This is called "adsorption." Secondly, "absorption" occurs
and consists of the organic material passing through the cell
wall of the bug where it is digested.
The bugs tend to bunch together and form a floe which
occurs throughout the aeration tank. This wastewater-bug
mixture is called the "mixed liquor" and the concentration
of bugs in the mixed liquor is defined as the "Mixed Liquor
Suspended Solids" (MLSS). For a properly operating acti-
vated sludge system on ordinary municipal wastes, the MLSS
concentration should be held at the level that gives the best
effluent. If the M LSS concentration or sludge volume is
too low, there would not be enough bugs to adequately
treat the wastes. If the MLSS concentration or sludge vol-
ume is too high, the bugs will not all settle in the clarifier
which follows the aeration tank. The mixed liquor should
also have a musty odor and dark brown color.
The clarifier performs the function of removing the bugs
and any floating scum from the wastewater. The settled bugs
form what is called activated sludge. The activated sludge is
pumped back to the aeration tank to maintain the correct
level of MLSS. With the bugs eating the food the wastewater
contains, there is an increase in the population of the bugs.
When this occurs, some of the activated sludge has to be
"wasted" or not returned to the aeration tank.
UNTREATED
WASTEWATER
TREATED
WASTEWATER
RETURN SLUDGE
WASTED SLUDGE
2-6
-------
Contact Stabilization
This waste (or excess) sludge is usually pumped to a
digester to stabilize it and:then possibly to sludge drying beds
for dewatering. With the bugs settled to form a sludge and
the scum removed, the clarified wastewater.flows on to
another tank for disinfection.
Contact stabilization is similar to conventional activated
sludge except that the capture of the waste material and the
digestion of that material by the bugs is done in different
aeration tanks. The bug can "adsorb" the waste material on
the cell wall in only fifteen to thirty minutes, but it takes
several hours to "absorb" the material through the cell wall.
In conventional activated sludge, adsorption and absorption
are done in one tank, therefore, the wastewater has to remain
there for a longer period. In both cases, the bugs flow to the
clarifier to be separated from the wastewater, but in contact-
stabilization, the settled bugs still have to digest their food.
Another aeration tank called a stabilization or reaeration
tank is provided separately for this step. Here the bugs
digest the food and then are returned hungry to the original
aeration tank (contact tank) ready to eat more food.
UNTREATED
WASTEWATER
TREATED
WASTEWATER
WASTED
SLUDGE
REAERATION TANK
The Mixed Liquor Suspended Solids (MLSS) concen-
tration of the contact tank should be maintained around
1,500-2,000 mg/L. If the MLSS gets too high, the sludge
2-7
-------
Extended Aeration
Oxidation Ditch
that the microorganisms form is disposed of or "wasted" as
in conventional activated sludge.
Extended aeration is similar to conventional activated
sludge except that the bugs are retained in the aeration tank
longer and do not get as much food. The bugs get less food
because there is a high mixed liquor suspended solids concen-
tration, 2,000-5,000 mg/L. In addition to the bugs consum-
ing the incoming food, they, in turn, consume any stored
food in the dead bugs. The new products are carbon dioxide,
water, and a biologically inert residue.
. Extended aeration does not produce as much waste
sludge as other processes; however, wasting still may be
necessary to maintain proper control of the process.
The oxidation ditch can be operated as either a conven-
tional or extended aeration activated sludge treatment sys-
tem. An oxidation ditch system consists of channels placed
side by side, connected such that one continuous loop of the
wastewater flow is obtained.
AERATOR
tt AERATION TANK
The wastewater is propelled and aerated by use of
horizontal-shaft mechanical aerators placed in the channels.
As with the other activated sludge systems, the wastewater
then flows to the clarifier where the solids are settled and re-
turned to the oxidation ditch to provide a fresh hungry group
of bugs for the incoming wastewater.
2-8
-------
RBC (Rotating Biological
Contactor)
ABF (Activated Bio-Filter)
A bio-disc, or RBC (Rotating Biological Contactor as it
is sometimes called, utilizes a biological slime of bugs which
forms on a series of thin discs mounted side by side on a
shaft. These discs are partially submerged by the wastewater
and slowly rotate. The bugs obtain oxygen from the atmos-
phere at the exposed portion of the disc. The excess growth
of bugs on the disc sloughs or breaks off and flows to the
clarifier to be separated from the wastewater.
DISC UNIT
INFLUENT
CHLORINE
CONTACT TANK
EFFLUENT
The principles of treatment are the same as in pre-
viously mentioned systems. The bugs adsorb and absorb the
solids and soluble organics in the wastewater and digest the
food with the aid of oxygen from the atmosphere.
The ABF makes use of both suspended microorganisms
or bugs as in conventional activated sludge and a fixed micro-
organism growth as in bio-discs. The fixed growth occurs on
wooden racks stacked on top of each other in a tank approxi-
mately 14 feet (4 meters) deep. The racks are made of
wooden laths fixed to supporting rails. Oxygen is supplied
to the wastewater and the bugs by the action of the water
splashing between layers and moving in a film over the fixed
growth.
BIO-MEDIA RACKS
INFLUENT
WET WELL AERATION TANK
2-9
-------
The suspended bugs, as in conventional activated sludge,
are mixed with the untreated wastewater, then are pumped
up to the tank containing the wooden racks, then flow to an
aerated tank before being separated in a clarifier. The sludge
formed in the clarifier is returned to the untreated waste-
water after the excess sludge is wasted.
Physical-Chemical Besides the biological wastewater treatment processes
mentioned previously, there also exists Physical-Chemical
(P-Chem.) or advanced wastewater treatment plants. In-
stead of using the bugs to consume the pollutants, chemicals
are added that react with the pollutants and allow them to be
removed by physical means such as sedimentation and
filtration.
Another form of advanced wastewater treatment makes
use of activated carbon. The process of adsorption is used to
remove the pollutants. Activated carbon can follow either
the biological treatment systems mentioned previously or
physical-chemical treatment to provide a higher degree of
pollutant removal.
2-10
-------
SECTION 3
DESCRIPTION OF UNIT
PROCESS EQUIPMENT
Pretreatment
Screens
Screens are provided at the beginning of the treatment
process to remove pieces of wood, rags, and other debris
that get in the wastewater. These objects may damage the
pumps or hinder in-plant flow. The screens usually consist of
parallel bars placed vertically or at an angle in the channel
through which the wastewater flows.
BAR SCREEN
Comminutor
Often following, and sometimes in parallel with a bar
screen, is a comminutor. This device cuts up or shreds
material as the wastewater flows through. It consists of a
screen with cutting teeth moving through the openings.
Solids are cut into fine particles that will not interfere with
operation of the treatment plant.
2-11
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COMMIIMUTOR
Grit Chamber
AERATION
Diffused Air
Inorganic material, such as eggshells and sand, is abrasive
and damaging to equipment, and is not broken down in the
treatment process. This material, called grit, will settle out if
the velocity of the wastewater does not exceed one foot per
second (fps) (0.3 meters per second). A grit chamber is a
long trough that is designed such that the wastewater will
flow at approximately one fps (0.3 mps) under average flow
conditions. The settled grit is removed either by hand or
mechanically, and is usually buried. In some grit chambers,
air is added through diffusers to provide better separation of
grit from other solids.
Diffused air systems are one method of supplying oxy-
gen to the wastewater. The systems consist of a blower, air
piping with mains, valves, meters, and other fittings used to
carry air from the blowers to the air diffusers located at the
bottom of the aeration tank. The diffusers are designed to
produce either small or large bubbles. An equally important
function of aeration devices is to maintain complete mixing
throughout the aeration basin so that no stale or septic
pockets exist.
2-12
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Several types of diffusers are shown in the figure below.
Surface Aerators
CLARIFICATION
Solids Separation
COARSE BUBBLE DIFFUSERS
OPEN PIPE DIFFUSER
FINE BUBBLE DIFFUSERS
PLATE DIFFUSER
CLOTH TUBE
SARAN-WRAPPED TUBE
AERATION DIFFUSERS
Surface aerators are also used to mix and supply oxygen
to the wastewater. The aerator consists of a submerged
impeller mounted vertically in the aeration tank. The motor,
mounted overhead, turns the impeller vigorously allowing the
wastewater to be aerated.
Sludge coming from the aerator must pass to a settling
tank (clarifier) where the flow rate is slowed down to remove
the bugs from the wastewater.
The shape of the clarifier may be either circular or rec-
tangular, and is large enough to detain the wastewater for
1-1/2 to 2 hours. This detention time reduces the velocity
and allows the solids time to settle. The settled solids
(sludge) and floating solids (scum) are generally removed by
mechanical collectors. The clarified wastewater passes over
a long weir either at the end or around the basin. The weir
should allow the wastewater to overflow at a velocity slow
enough not to disturb the solids that have settled.
2-13
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SLUDGE HANDLING
AND DISPOSAL
Aerobic Digestion
Anaerobic Digestion
CIRCULAR CLARIFIER
DRIVE UNIT
L
EFFLUENT TROUGH
INFLUENT WELL
EFFLUENT WEIR
[J
INFLUENT
SLUDGE COLLECTOR
MECHANISM
CLARIFIER
Aerobic digestion is a method often used in package
plants to prepare waste sludge for dewatering and disposal
possibly as compost material or soil conditioner. The excess
sludge from the treatment process is pumped to the digester
where it is aerated for 20 days or longer in order to oxidize
the remaining food. An extended aeration sludge requires
20 days, but a contact stabilization sludge requires longer.
After aeration for the required time, the aerators are turned
off and the sludge is allowed to settle. The liquid on top
(supernatant) is returned to the aeration basin of the waste-
water treatment plant. The sludge is pumped to dewatering
facilities or land disposal. The whole process of settling and
withdrawal may take from 1 to 4 hours. If it takes more
than 8 hours to get 6 to 12 inches (15-30 cm) of supernatant,
it is time to dispose of sludge.
Anaerobic digestion is a continuous process of stabiliz-
ing waste sludge. Fresh sewage sludge is added continuously
or at frequent intervals. The water separated from the sludge
is normally removed as the sludge is added. Digested sludge
is removed at less frequent intervals. The sludge is digested
by bacteria, which use the organic material as food, and they
give off the products carbon dioxide and methane gas.
Anaerobic digestion is generally not found on package
treatment plants. If the operator is responsible for main-
taining a digester, the following EPA publication should be
obtained for information on the basics and operation.
2-14
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Sludge Drying Beds
(Operations Manual—Anaerobic Sludge Digestion, EPA
Publication No. EPA 430/9-76-001.)
Sludge drying beds are used to dewater the sludge com-
ing from the digester. The surface of the bed is eith'er sand
with a gravel underdrain or the bed might be of asphalt.
\
SLUDGE DRYING BED
PUMPING
Centrifugal Pump
Sludge may be placed on the surface 6 to 18 inches
(15-46 cm) deep, depending on the climate. The drying is
accomplished by evaporation and percolation of the mois-
ture from the sludge. Removal of the dried sludge on the
sand beds must be done by hand since heavy equipment will
damage the underdrain. The underdrain is pumped back to
the influent to the treatment plant. The dried sludge may be
used as a soil conditioner and fertilizer. Some states have
restrictions against placing the sludge on soil growing root
crop vegetables; therefore, it is best to check with the regula-
tory agency first.
A centrifugal pump consists of an impeller rotating in a
casing. The impeller is supported by a shaft and bearings.
The liquid enters at the center of the impeller, is rotated by
the vanes of the impeller, and thrown out the exit by centrif-
ugal force.
2-15
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CENTRIFUGAL PUMP
Reciprocating Pump
CENTRIFUGAL PUMP
A reciprocating (positive displacement) pump is one
that utilizes a piston to move sludge or water. When the
piston retreats back up the cylinder, it allows a check valve
to open so the fluid can flow in. On the following compres-
sion stroke, the inlet check valve closes and the outlet check
valve opens, allowing the fluid to flow out. This action
occurs repeatedly to allow a continuous flow of liquid.
POSITIVE DISPLACEMENT SLUDGE PUMP
SOLENOID
DISCHARGE
'PRESSURE
'PUMP
POSITIVE DISPLACEMENT PUMP
2-16
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Air Lift Pump
An air lift pump is frequently used to pump sludge. It
consists of a suction or eductor pipe placed vertically such
that the suction end is in the sludge layer. Air enters the
eductor pipe near the bottom. The rising bubbles cause a
lower pressure inside the pipe causing the sludge to be lifted
to the discharge point. Two possible causes of problems are:
1. The footpiece, or the point at which the air pipe
joins the suction pipe, may become clogged so that
there is not sufficient air to operate the air lift.
2. The entrance to the tail pipe (suction pipe) may be-
come blocked from a large concentration of solids
or objects too large to be pumped.
OUTLET
INLET
AIR LIFT PUMP
2-17
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CHLORINATION
Chlorination is used at the last step in the treatment
process to kill disease-causing organisms that exist in the
wastewater. A basin, called the chlorine contact chamber, is
provided to allow the chlorine sufficient time to be com-
pletely mixed and to "contact" the bacteria. A one-hour
detention time is generally provided in order to kill the
bacteria.
BOARD TO SKIM FLOATABLES
(INSTALLED SAME WAY AS IN CLARIFIERS
SEE CASE HISTORIES)
CHLORINE GAS
INFLUENT £1
EFFLUENT
TO PREVENT SHORT-CIRCUITING
TURBULENCE NECESSARY FOR
COMPLETE MIXING OF CHLORINE
CHLORINE CONTACT TANK
2-18
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SECTION 4
EFFECTS OF WEATHER
Environmental factors that affect the wastewater treat-
ment process include temperature and precipitation. The
wastewater temperature affects the activity of the micro-
organisms or bugs. During cold winter weather this reduced
activity might lower the efficiency of the treatment system.
Besides biological effects of temperature, the flocculation
and sedimentation of the mixed liquor solids is not as effec-
tive at lower temperatures. Ice buildup will hinder or stop
altogether the proper operation of mechanical parts such as
sludge scraper mechanisms and aerators.
Precipitation over the area served by the treatment
plant may cause the wastewater flow to increase due to the
existence of combined sewers or due to infiltration into the
sewer line. This is generally accompanied by a weaker waste-
water in terms of Biochemical Oxygen Demand (BOD) due
to the dilution effect of the stormwater. (See Glossary for
explanation of BOD.) These occasions might cause the treat-
ment system to be hydraulically overloaded. This results in
a reduced time spent by the wastewater in the treatment
system; thus, treatment efficiency is reduced.
Without plant modifications, there is not much the
operator can do to offset the changes in treatment efficiency
caused by temperature changes and high flows during storms.
However, ice buildup can be controlled by frequent observa-
tion and removal during cold periods. For persistent cold
weather problems, construction of a lightweight building over
the aerator and clarifier may be more economical in the long
run than fighting ice. Diffused air systems will supply suffi-
cient heat inside the building to prevent ice from forming on
the clarifier.
It normally will be necessary to vary the amount of
• sludge as seasons change. Because the bugs are not as active
in winter at low temperatures, than in summer, the MLSS
will need to be higher in the winter than in the summer.
2-19
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POTPOURR
-------
SECTION 1
CASE HISTORIES
OPERATIONAL HINTS
Tank Cleanliness
In the course of writing this manual, several package
plants were visited to observe and note innovative ideas by
the operators and unusual operating conditions they ex-
perienced. Some of these are presented here as an example
of things the operator can do at his own plant to improve
performance or ease maintenance.
One operator of an activated sludge plant has a problem
with scum in his plant due to a dog food processor discharg-
ing to the treatment system. This scum ends up in the aero-
bic digestion portion of the plant. When the sludge has
been stabilized, the air supply is turned off and the solids are
allowed to settle. The sludge solids are pumped to a tank
truck for disposal. The floating scum should not be returned
to the aeration tank with the supernatant; therefore, it is
pumped out and disposed of by burying. To prevent odors
due to the scum, the surfaces of all tanks containing the scum
are hosed down daily.
Diffuser Clogging
Daily plant observation tells one operator when an air
diffuser begins to clog. This is done by noting the surface
area that is cleared of any foam or scum. When the diffuser
begins to clog, this area will be reduced. As indicated in the
3-1
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photo, the operator knows the diffuser is clogging because
the scum is normally cleared across the whole width of the
tank.
Aerator Time Clock Control
EQUIPMENT MODIFICATIONS
Airlift Pump Plugging
One operator of a plant serving a tourist facility has a
varying flow based on the seasons. During the slow winter
season, if the air diffusers ran full time, the contents of the
aeration tank would be overaerated. To solve this problem,
the operator connected the blower to a timer such that air
would be supplied only an average of 15 minutes out of every
hour.
For normal operation of a plant, and especially one that
is hydraulically overloaded, a possible solution to reducing
a high solids level in the effluent is to operate the air lift
scum skimmer in the clarifier only once a day. Any move-
ment in the clarifier reduces the effectiveness of the unit and
the skimmer movement tends to create an updraft in the
flow, thus hindering settling.
Most of the clogging of air lift pumps occurs in the
riser. This can be easily cleaned if there is a way to ram a
small diameter pipe or rod down through the riser to the
suction end. This can be done by replacing the ell at the top
of the riser with a plugged tee as shown in the figure.
The plug can be removed after turning off the pump and
the rod can be inserted to unclog the riser.
32
-------
] PLUGGED TEE
Scum Baffle Installation
Another beneficial use of the plugged tee is that it pro-
vides a place for the operator to connect a line when it be-
comes necessary to waste sludge. When less flow is needed,
due to fluctuating seasonal loads, a second smaller air lift
might be installed.
If a rectangular clarifier is not provided with a scum
baffle, one can be constructed out of wood. Cut a 1 x 10 or
1x12 inch board long enough to wedge in the clarifier just
prior to the overflow weir as shown in the drawing.
3-3
-------
TOP
^)
AERATION -L
TANK _.
UJ
LL.
2
5k
i=iiu(r
1
1
^
SIDE
SCUM
Use of a Screen
Air Regulation
Odors in Grit Channels
The wooden strip extends above and below the water
level 10-12 inches (25-30 cm) in order to block any floating
particles or scum.
Another method of preventing leaves and floating
objects from flowing to the chlorine contact basin and then
out with the effluent is a screen basket that may be hung on
the clarifier discharge. A suitable wire mesh would be that
found in rabbit hutches.
Similar baskets may be placed at the inlets to the aera-
tion basin or clarifier, depending on the design of the package
plant. The basket could contain a smaller one within it with
window screen mesh to catch even smaller floatables.
Sometimes treatment plants are placed in areas where
sticks and leaves from nearby trees create a major problem on
the surface of the package plant. If this is the case, small
treatment plants may be easily covered with a screen.
Some treatment plants are not provided with a means to
regulate the air to the aeration tank. To reduce the amount
of air needed in these cases, one individual suggested putting
a tap on the air line and having it "wasted" just below the
water surface. The submerged discharge will eliminate the
noise due to air being bled off, but at the same, time will not
affect the dissolved oxygen when air is being wasted to pre-
vent high DO levels.
Treatment plants are designed sometimes for larger
flows than they receive initially. The lower flow may result
in organics settling out in the grit chamber with the
inorganics. This leads to odor problems. A solution to this
is to tap the air supply line to the diffusers and have an air
discharge in the grit chamber. The air outlets should be lo-
cated approximately two to three feet (1/2 to 1 meter) apart
3-4
-------
Sludge Settling in Aeration Tanks
Foam Control
at the bottom of the channel with the air projected across the
channel. A rolling action should be created that keeps the
organics suspended but still allows the inorganics (grit) to
settle.
Rectangular aeration basins sometimes contain dead
spots in the corners due to the inability of the air diffusers to
provide complete mixing. If such is the case, the operator
should tap the air supply line and install a diffuser in each
corner. This will allow for better distribution of the available
air supply and eliminate dead or septic pockets in the basin.
To control foam in the aeration tank or direct floating
scum in the clarifier toward the scum box, a water spray sys-
tem can be installed by the operator. The foam will require a
spray with a larger force than would be necessary and desir-
able on a clarifier. For small aeration tanks, a shower nozzle
located above the tank with the necessary piping is effective.
For the clarifier, a nozzle, such as the type shown in the
drawing with a fan spray, is effective in directing the scum.
TOOLS
Sludge and Scum Scraper
One operator constructed a handy tool for scraping
solids that accumulate in the inlet trough to the aeration
tank. The following photos show the tool's construction
and operation. If the solids were not occasionally stirred
up, they would become septic and produce odors. This
same tool can be used for scraping the sides of the clarifier.
3-5
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Dip Net
Another device that every plant should have and that is
easily constructed is a dip net to skim off the top of the
water level. As shown in the photo, all that is necessary is
the wood and screen. The handle should be long enough to
reach any point on the water surface.
3-6
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SECTION 2
SAFETY AND EMERGENCIES
GENERAL
Lost time, days, and even death is the result of not
being concerned with applying the rules of safety to all acti-
vities involved in operating and maintaining a plant. Prac-
ticing "safety" is not just knowing what to do; it is a life-
style. Personnel must not only acquire this "life-style," but
must also know what to do if an accident occurs.
Sewage treatment plant operators have one of the most
hazardous of jobs. Their injury rate or number of disabling
injuries per man-hour is four times the average of all indus-
tries. Daily exposure to physical injuries, body infections,
noxious gases or vapors and oxygen deficiencies is an occupa-
tional hazard encountered at sewage treatment plants.
LABORATORY SAFETY
The handling of wastewater and numerous chemicals
creates a potential hazard to the health and safety of individ-
uals in the lab. Danger originates when lab workers fail to
use caution in handling these materials, fail to read labels or
fail to follow directions as to use and procedure. There
always exists the possibility of inadvertent or accidental
spills which will require immediate and specifically correct
action to minimize a potential hazard. Inhalation of vapors
must be avoided since many chemicals or compounds are
dangerous in this respect. In summary, it can be said that
most hazards caused in the lab result from inattention, care-
lessness, and poor housekeeping.
3-7
-------
CHLORINE SAFETY
SincQ chlorine usagG is common to most treatment
plants and duG to its hazardous nature, some safety precau-
tions regarding its use warrant mention. Chlorine gas affects
the respiratory system and can cause burns. In any chlorine
atmosphere use short, shallow breathing; recovery depends
on the amount of chlorine inhaled. For more information on
chlorine safety and first aid, see:
Chlorine Manual
By: The Chlorine Institute, Inc.
342 Madison Avenue
New York, New York 10017
Price: $0.75
EMERGENCIES
Effects of Weather
Emergency Resources
Freezing: All outside hose bibs should have under-
ground drain capability in order to dewater the faucets dur-
ing extreme freezing conditions. It will be necessary to check
other portions of the plant which may be subject to freezing
due to water splashing on mechanical equipment. If faucets
are not self-draining, leave hose running into tank at a rate
fast enough to prevent freezing.
High Winds: The major problem presented by wind-
Storms could possibly be blowing debris, such as leaves, sticks,
and paper from the surrounding area into the clarifier. This
material could cause plugging of pumps, and the operator
should check the pumping operation following windstorms
to verify that sludge lines are open.
Warning System: Some of the larger plants may have a
visual indication of the operating status of all equipment
shown on a panel located in the control room. The control
panel has two major functions—one is to show the status of
all the operating equipment that is tied to the panel electri-
cally, and the second is to sound an audible alarm and show
visually which piece of equipment is in alarm condition.
Some operators have installed a flashing red light at a high
point around the plant connected to critical circuits such that
when they are not energized the light flashes. Local police,
or an obliging neighbor, can then notify the operator that a
problem exists.
Standby Equipment: The operator should either have
on site, or know where to obtain on short notice, a gas-driven
pump. This allows the operator to handle emergency pump-
ing needs during power failures or equipment breakdown.
3-8
-------
Chemical Supplies: To ensure an adequate supply of
chlorine at all times, the plant operating policy should be to
reorder chlorine so as to always have at least two weeks
supply and preferably 30 days supply on hand.
Security: Plants should be protected by a chain link
fence around the periphery of the property with a locked
entrance gate. External lighting should be provided and
controlled by a light detector to automatically control the
on-off function of the lights.
In regard to safety equipment, operators must be fam-
1 iliar with the location and use of the first aid kit, fire extin-
guishers, gas mask, and other items necessary in an emer-
gency situation. A list of minimum emergency equipment
follows:
One 16-foot ladder
One gas-driven, portable pump
Fire extinguishers
One first aid kit
One special breathing apparatus
One heavy-duty flashlight
One chlorine leak repair kit
Emergency Notification An emergency notification schedule such as the one
presented below should be developed and posted at the plant
and at the city's water and sewage works office or at the of-
fice of the treatment plant owner.
TELEPHONE
NUMBER
INJURY
fire Department
Ambulance
Hospital Emergency Room
Poison Center
3-9
-------
TELEPHONE
NUMBER
FIRE-EXPLOSION-CHLORINE
Fire Department
Local Police
County Sheriff
State Patrol
Local Chlorine Supplier
UTILITIES
Power Company
Communication (Telephone)
Water
TOXIC SPILLS
State Pollution Control Agency
County Health Department
RESPONSIBLE PLANT PERSONNEL
Operator
Relief Operator
Person In Charge of Collection System
3-10
-------
SECTION 3
PLANT MANAGEMENT
PLANT OWNER
PLANT OPERATOR
The owner may be the individual who actually pur-
chased the package plant, the governing board of a sewerage
agency, the city manager or city council. It is the individual
or group of individuals that the operator is ultimately respon-
sible to and who have the authority to make policy decisions
in regard to the treatment plant.
The owner of a package sewage treatment plant has the
responsibility of providing an operator who is conscientious,
in good physical condition, and is capable of operating and
maintaining the treatment plant after being provided proper
instruction and orientation. The orientation period might
initially require the full-time duties of the operator.
If the current operator leaves the employ of the owner,
it is the owner's responsibility to obtain immediate replace-
ment. The replacement should be provided with proper
training to make up any possible deficiency.
The owner should encourage opportunities for plant
personnel to expand their knowledge by attendance at
meetings, short schools, special training courses, and utili-
zing other opportunities for increasing their technical
competence.
The owner has the responsibility to establish a salary
level scale that encourages tenure of trained and experienced
personnel.
It is the responsibility of the owner to obtain from the
appropriate regulatory agency any permit required for opera-
tion of the plant.
The owner is ultimately responsible for the performance
of the treatment plant. To maintain such performance, the
owner is responsible for general supervision of the operator,
in addition to supplying him or her with all necessary tools,
materials, and parts for proper plant operation and main-
tenance. It is also the responsibility of the owner to provide
adequate funds for plant expansion as needed.
The plant operator is responsible for the conscientious
and proper operation and maintenance of the plant. This
includes maintenance of buildings, grounds, and equipment.
The operator is responsible for maintaining a safe work-
ing environment and being safety conscious in his or her
actions.
3-11
-------
The operator is required to make those tests and obser-
vations required for the proper operation of the plant and to
satisfy the appropriate reporting agency regulations. All
results should be made known to the owner in terms that can
be easily understood.
The operator must have the ability to interpret labora-
tory tests and apply their results to the operational control
of the treatment plant.
The operator is responsible in notifying the owner as
to the need for tools, parts, and supplies. Sufficient notice
should be given so that such items will be available when
needed.
The operator has the responsibility to become fully
acquainted with the plant and the treatment process used.
He should take advantage of training offered by the regula-
tory agency, manufacturer-supplier or local community
college.
3-12
-------
APPENDICES
-------
APPENDIX A
BIBLIOGRAPHY Alaska, State of, Department of Health and Welfare, Division
of Public Health. Operating Manual For Small, Extended
Aeration, Activated Sludge Treatment Plants. October 1963.
American Public Health Association. Standard Methods for
the Examination of Water and Wastewater. 14th Edition,
1975.
Dresnack, R. and W. Miller. "Current Trends in Packaged
Wastewater Treatment Facilities, Part I-IV." Water and Sewage
Works, August-November 1975.
Eye, J. D., D. P. Eastwood, F. Requena, and D. P. Spath. "Field
Evaluation of the Performance of Extended Aeration Plants."
Journal WPCF 41:7 (1299). July 1969.
Hayes, R. B. Operator's Pocket Guide to Activated Sludge:
Part I — The Basics, Part II — Process Control and Trouble-
shooting. Stevens, Thompson & Runyan, Inc., 5505 S.E. Mil-
waukie Avenue, Portland, Oregon 97202. 1975.
Lesperance, T. W. "A Generalized Approach to Activated
Sludge, Part I-VI." Water Worksand Wastes Engineering, April-
December 1965.
McKinney, R. E. "Principles of Aerobic Digestion, Part 1-3."
Water and Waste Digest, September 1962-February 1963.
National Sanitation Foundation. Package Sewage Treatment
Plants Criteria Development Part I: Extended Aeration.
FWPC Grant WPD-74. September 1966.
National Sanitation Foundation. Package Sewage Treatment
Plants Criteria Development Part II: Contact Stabilization.
FWPC Grant WPD-74. June 1968.
Pfeffer, J. T. "Extended Aeration." Water and Sewage Works,
June 1966.
Sacramento State College Department of Civil Engineering.
Operation of Wastewater Treatment Plants — A Field Study
Training Program. Environmental Protection Agency Water
.Quality Office Technical Training Grant No. 5TT1-WP-16-03.
1970.
A-1
-------
Smith & Loveless. Factory Built "Oxigest" Extended Aera-
tion Treatment Plant Operation and Maintenance. Lenexa,
'Kansas 66215.
Surburbia Systems, Inc. Operating and Maintenance Manual-
Model DCSC-250 Sewage Treatment Plant. Leawood, Kansas
66203.
Water Pollution Control Federation. Process Control, Ex-
tended Aeration Wastewater Treatment Plants. WPCF - Man-
force Training Module-1 with Audio-Visual Aid. WPCF,
Washington, D.C. 1972.
Water Pollution Control Federation. Simplified Laboratory
Procedures for Wastewater Examination. 2626 Pennsylvania
Avenue, Washington, D.C: 20037.
Yeomans Brothers Company. Handbook for Care of Centri-
fugal Pumps. Manual 2000, E.R.W. 5M-11-55.
U.S. Environmental Protection Agency. Operational Control
Procedures for the Activated Sludge Process. 330/9-74-001
a, b, and c.
Part I — Observations
Part 11 - Control Tests
Part 111A — Calculation Procedures
National Training and Operational Technology Center,
Cincinnati, Ohio 45268.
(This material is also available in slide/tape format from this
source.)
A-2
-------
APPENDIX B
GLOSSARY
Absorption — A process in wastewater treatment by which
organic material is consumed by a microorganism by passing
the material through the cell of the microorganism.
Adsorption — The sticking of a solid in the wastewater to
the surface of the microorganism.
Aerobic — A condition in which "free" or dissolved oxygen
is present in the aquatic environment.
Anaerobic — A condition in which "free" or dissolved oxy-
gen is not present in the aquatic environment.
Biochemical Oxygen Demand (BOD) - A measurement of
the amount of oxygen required by the microorganisms to
metabolize or digest the organic material in the wastewater.
Contact Tank — The tank in the contact-stabilization plant
that receives wastewater and reaerated return sludge.
Adsorption takes place here.
Dissolved Solids — Consists of organic and inorganic material
that is present in true solution in the wastewater.
Grit — The heavy mineral material present in wastewater such
as sand, eggshells, gravel, and cinders.
Inorganic Waste — Waste material such as sand, salt, iron, cal-
cium, and other mineral materials which are not converted in
large quantities by microorganism action. Inorganic wastes
are chemical substances of mineral origin and may contain
carbon and oxygen.
Microorganisms - Microscopic living objects which require
energy, carbon, and small amounts of inorganic elements to
grow and multiply. They get these requirements from the
wastewater and the sun and in doing so help to remove the
pollutants from the wastewater.
Mixed Liquor — Used to refer to the mixture of wastewater
and return activated sludge in the aeration tank of an acti-
vated sludge system.
B-1
-------
Overaerated — Sludge which has long periods in the aeration
tanks with dissolved oxygen at 4 mg/L and above.
Overoxidized - Sludge which passes through the aerator
and clarifier many times in one day due to high return rates.
Organic Waste — Waste material which comes from animal or
vegetable sources. Organic waste generally can be consumed
by bacteria and other small organisms. Organic wastes con-
tain mainly carbon and hydrogen along with other elements.
pH - A term used to express the intensity of the acid or
alkaline sources. A pH of 7 is considered neutral, with acidity
increasing as the pH decreases. Normal pH for wastewater
treatment is 6.5 to 7.5.
Septic — A condition produced by the growth of anaerobic
organisms. If severe, the wastewater turns black, giving off
foul odors and creating a heavy oxygen demand.
Settleable Solids — That matter in wastewater which will
not stay in suspension during a preselected settling period.
Sludge — The settleable solids separated from the liquid
during clarification.
Sludge Age — The theoretical length of time that a particle
of activated sludge will remain in the aeration system.
Sludge Digestion - A process by which organic matter in
sludge is gasified, liquified, mineralized, or converted to a
more stable form by anaerobic or aerobic organisms.
Stabilization Tank — The tank in the contact-stabilization
plant that receives return sludge from the clarifier for more
aeration (reaeration). Absorption takes place here.
Supernatant — Liquid removed from settled sludge. Super-
natant commonly refers to the liquid between the sludge on
the bottom and the scum on the surface of any settling
tank.
Suspended Solids — Solids that either float on the surface of,
or are in suspension in, water, wastewater, or other liquids
and are largely removable by filtering.
B-2
-------
APPENDIX C
OPERATION AND MAINTENANCE SCHEDULE
Frequency
Operational and As
Preventive Maintenance Daily Wk. Mo. 3 Mo. 6 Mo. Yearly Necessary
C-1
-------
APPENDIX D
SETTLOMETER GRAPH
SETTLOMETER
DATE:
1UUU
ann
ann
ouu
UI
X TOO
3
(A
° finn .
UI
(A 500
UI
5
3
» iinn .
onfi .
200
100
n
IUU
80
01
o
: VOLUME
O
0
3
_l
4O (A
2O
5 10 15 20 25 30
40
50
60
TIME- MIN.
D-1
-------
APPENDIX E
MONTHLY TREND GRAPH
MONTH:
DAILY SETTLOMETER
RESULTS AT 15 WIN.
1000
800
600
400
200
O (O
CO (/>
> _i _i
ii I
u. u. u.
I I I I I I I III
2468
10 12 14 16 18 20 22 24 26 28 3O
DAY OF MONTH
-------
APPENDIX F
FLOW RECORDS
Day of Month
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
Total
Average
MONTH:
Totalizer Reading
Daily Flow
Comments
F-i
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APPENDIX G
METRIC EQUIVALENTS
METRIC CONVERSION TABLES
Recommended Units
Description
Length
Area
.Volume
Mass
Timi
Force
Unit
meter
kilometer
millimeter
centimeter
micrometer
iquare meter
square kilometer
square centimeter
square millimeter
hectare
cubic meter
cubic centimeter
liter
kilogram
gram
milligram
tonne
second
day
year
newton
Symbol
m
km
mm
cm
pm.
m?
km2
em>?
mm'
he
m3
cm3
L
kg
g
mg
t
s
day
yror
1
N
Comments
Baxif SI unit
The hectere 11 0.000
m2) is a recogni/ed
multiple unit and
will remain in inter-
national use.
The liter is now
recogni/ed as the
special name lor
the cubic decimeter
Bask SI unit
1 tonne » 1.000kg
Basic SI unit
Neither the d«y nor
the year is en SI unit
but both are impor
lint.
The newton is that
force that produces
an acceleration of
1 m/s? in a mass
ol 1 kg.
English
Equivalents
39. 37 in. = 3.28(1 =
1.09yd
0.62 mi
0.03937 in.
0.3937 in.
3.937 X I03=I03A
10.744 sq ft
= M96iqyd
6.384 iq mi «
247 acres
0.155 sq in.
0.00155 sq in.
2471 acres
35. 314 cult •
1.3079cuyd
0.061 cu in.
1. 057 qt= 0.264 gal
= 0.81 X 10-* acre-
It
2.20S Ib
0.035 01 = 15.43 gr
0.01543 gr
0.984 ton (long) =
1.1023 ton (short)
0.2248 lib (weight]
" 7.5 poundals
Description
Velocity
linear
ingulir
Flow (volumetric)
Viscosity
Pressure
Temperature
Work, energy.
quantity of heet
Power
Application of Units
Description
Precipitation,
run-ol.,
evaporation
River flow
Flow in pipes.
conduit!, chan-
nvli, over weirs,
pumping
Discharges or
abstractions,
yield!
U»ge of water
Density
Unit
millimeter
cubic meter
p«r ucond
cubic meter par
tecond
liter per second
cubic meter
per day
cubic meter
per year
liter per person
pir day
kilogram per
cubic mater
Symbol
mm
m3/s
m3/s
L/s
m3/day
m3/yr
L/person
day
kg/m3
Comments
For meteorological
purposes it miy be
convenient to meas-
ure precipitetion in
terms of miss/unit
area (kg/m3).
1 mm of rain =
1 kg/sg m
Commonly celled
the cumec
1 L/s = 86.4 m3/dav
The density of
water under stand-
ard conditions ii
I,000kg/m3or
l,OOOg/L
English
Equivalents
35. 314 els
15.85 gpm
1.83 X 10-3gpm
0.264 gcpd
0.0624 Ib/cu ft
Description
Concentration
BOD loading
Hydraulic load
par unit am:
e.g. filtration
rates
Hydraulic load
par unit volume;
e.g. biological
lilters, lagoons
Air supply
Pipes
diameter
length
Optical units
Recommended Units
Unil
meter per
second
millimeter
per second
kilometers
per ucond
fldiini pit
HCond
cubic meter
per second
liter per second
poise
newton per
square meter
kilonewton per
square meter
kilogram (torce)
per square
centimeter
degree Kelvin
degree Celsius
joule
kilojoule
watt
kilowatt
joule per second
Symbol
m/s
mm/s
km/s
red/I
m3/s
L/s
poise
N/m2
kN/m2
kgl/cm'
K
C
J
kJ
W
kW
ill
Comments
Commonly called
the cumec
The newton is nol
yet well known es
the unit of lorce
and kgt cm2 will
clearly be used for
some time. In this
lield the hydraulic
head expressed in
meters ii en accept
able elternative.
Basil SI mill
The Kelvin and
Celsius degrni
»re identical.
The use of the
Celiiui scale is
recommended as
it il till lormll
centigrade scale.
1 joule - 1 N m
1 watt • 1 J/s
English
Equivalents
3.28 Ips
0 00328 Ips
2.230 mph
15.850 gpm
= 2.120 elm
15.85 gpm
0.0672/lb'
sec II
0.00014 psi
0145 psi
14.223 psi
2.778 X ID'7
kwhr '
3.725X10-7
hp.hr • 0.73756
ft-lb - 9.48 X
10"" Blu
2.778 kwhr
Application of Units
Unit
milligram par
liter
kilogram par
cubic meter
per day
cubic meter
pit tquan mini
per day
cubic mater
par cubic mater
par day *
cubic meter or
liter of Iree air
per ucond
millimeter
m«ter
lumen per
squere meter
Symbol
mg/L
kg/m3 day
m3/m2 day
nv>/m3day
m3/s
L/s
mm
m
lumen/m2
Comments
If this is con-
verted to a
velocity.it
should be l«
(1 mm/s » 86.4
m3/m2 day).
English
Equivalents
1 ppm
0.0624 Ib/cu-tl
day
3.28 cu ft/sq ft
0.03937 in.
39.37 in. •
3.28 ft
0.092ft
cjndll/sq It
G-1
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