Turbidity Removal For Small Public Water Systems


United States
Environmental Protection
Agency
Office of
Drinking Water (WH-550)
Washington, DC 20460
EPA 570/9-83-011
June 1983
Turbidity Removal
for Small Public
Water Systems

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TURBIDITY REMOVAL FOR
SMALL PUBLIC WATER SYSTEMS
Prepared by:
SMC-MARTIN
900 W. Valley Forge Road
Valley Forge, PA 19482
Prepared for:
U.S. Environaental Protection Agency
Office of Drinking Water
Chester Paula, Project Officer
401 M Street, 8W
Washington, DC 20460
Contract No. 68-01-6285

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DISCLAIMER
THIS GUIDE HAS BEEN REVIEWED BY THE U.S. ENVIRONMENTAL PROTECTION AGENCY
AND APPROVED FOR PUBLICATION. APPROVAL DOES NOT SIGNIFY THAT THE CONTENTS
NECESSARILY REFLECT THE VIEWS AND POLICIES OF THE U.S. ENVIRONMENTAL
PROTECTION AGENCY, NOR DOES MENTION OF TRADE NAMES OR COMMERCIAL PRODUCTS
CONSTITUTE ENDORSEMENT OR RECOMMENDATION FOR USE.
i

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TABLE OF CONTENTS
Page
I.	SUMMARY AND OVERVIEW		1-1
Purpose and Structure of This Manual		1-1
When Turbidity is a Problem		 .	1-2
Alternative Methods Used to Reduce Excess
Drinking Water Turbidity 		1-2
Cost Estimating Procedures and Funding Sources 		1-5
Operation and Maintenance			1-5
Summary		 . .	1-6
II.	INTRODUCTION	II-1
Definition & Causes of Turbidity ............	II-l
Significance of Turbidity to Human Health. . 		II-2
The Safe Drinking Water Act	II-2
Sampling and Analyzing for Turbidity 		II-7
III. MEASURES TO TAKE IF THE TURBIDITY IS EXCESSIVE 		III-l
Introduction 		III-l
Nontreatment Alternatives	III-l
Treatment Alternatives for Turbidity Removal 		III-3
Presettling	III-5
Coagulation	III-5
Flocculation 		111-14
Sedimentation. . 	 ...	111-15
Filtration			111-17
Packaged Treatment Systems 		111-25
Direct Filtration			111-30
Waste Management	111-30
IV. DESIGNING TURBIDITY REMOVAL SYSTEMS	IV-1
Introduction 		IV-1
Characterization 		IV-1
Process and Equipment Selection	IV-4
Monitoring and Control 	 ...........	IV-10
Waste Disposal	IV-11
Corrosion Prevention 		IV-11
Other Design Considerations			IV-13
V. COST ESTIMATING PROCEDURES AND FUNDING SOURCES 		V-l
Cons true tion Costs	V—1
Operation & Maintenance Costs. . 			V-9
Funding Sources. 			V-14
VI. OPERATION AND MAINTENANCE	VI-1
Operator Requirements	VI-1
Manuals, Equipment and Supplies Needed .... 		VI-1
Startup Training and Assistance. ............	VI-2
Monitoring	VI-2
Coagulation Control and Monitoring 		VI-3
Preventive Maintenance		 •	VI-4
ii

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TABLE OF CONTENTS
(Continued)
Page
Emergency Procedures			VI-7
Safety Procedures	VI-7
VII. CASE HISTORIES	VII-1
Carlisle, Pennsylvania	VII-1
Hancock, Maryland. .................. .VII-3
Direct Filtration - 17 Plant Survey	VII-8
REFERENCES
Appendices:
A: Hetrie-English Conversion Factors
Abbreviations and Symbols	A-l
B: Sample Turbidity Meter Specification 	 B-l
C: Jar Test Procedure	C-l
D: Preventive Maintenance for Aquarius A Series
Complete Treatment Plant 	 D-l
# • •
hi.

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LIST OF FIGURES
Number
Title
Page
1
Nontreatment and Treatment Alternatives


for Turbidity Removal	

2
Water Treatment Processes for Turbidity


Removal	

3
Typical Packaged Complete Treatment Plant	
. 1-4
4
Typical Sources of Turbidity in Surface Waters . .
. II-l
5
Protected and Exposed Kicro-Organisms	
. II-3
6
Turbidity Sampling Points for a Small Water


System Using Surface Waters	

7
Comparison of Nephelometric and Jackson


Candle Turbidity Measurement ..... 	

8
Nontreatment and Treatment Alternatives for


Meeting NIPDWR Turbidity Standards 	

9
Turbidity Removal from Drinking Water	
.111-4
10
Coagulation/Flocculation/Sedimentation/Filtration.
.111-6
11
Mechanisms of Chemical Coagulation 	
.111-6
12
Jar Test Apparatus 	

13
Chemical Dissolving and Feeding Equipment	

14
Some Rapid Chemical Mixers . 	

15
Flocculators 	 . .

16
Clarifiers 	

17
Clarifier/Flocculator	

18
Tube Clarifier 	

19
Principal Mechanisms of Filtration . 	

20
Typical Rapid Sand Filter. ...... 	

21
Filter Configurations	

22
Ideal Filter ........ 	

23
Mixed Media Filter		

24
Pressure Filter	

25
Diatomaceous Filter Septum 	

26
Pressure Diatomite Filter	

27
Packaged, Complete Treatment System	
.111-29
28
Direct Filtration vs. Conventional Process


Design 	

29
Design Process for Turbidity Control Systems . . .
. IV-2
30
Treatment Process Selection	

31
Site Plan of 250,000 gpd Packaged Complete


Treatment Plant with Waste Lagoons 	

32
Construction Cost for Package Gravity


Filtration Plants	

33
Construction Cost for Package Pressure


Diatomite Filters	

34
Construction Costs for Package Complete


Treatment Plants 	

35
Construction Costs for Sludge Dewatering


Lagoons	

36
Annual Labor Hours for Package Gravity Filters . .
. V-13
iv

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LIST OF FIGURES
Continued
Number Title	Page
37	Annual Labor Hours for Packaged Pressure
Diatomite Filters. ..... 	 .....	V-13
38	Operation and Maintenance Cost of Packaged
Complete Treatment Plants - Building Energy,
Process Energy and Maintenance Material	V-17
39	Annual Labor Hours for Packaged Complete
Treatment Plants 		V-18
40	Sample Coagulant Control Curves	VI-3
41	Equipment Inventory Sheet	VI-5
42	Equipment Data Sheet	VI-6
43	Maintenance Procedure Sheet	VI-8
44	Weekly Preventive Maintenance Schedule .......	VI-9
45	Report of Trouble/Corrective Action Form ...... VI-10
46	Carlisle, PA Packaged Complete Treatment System. . .VII-2
47	Hancock, MD Packaged Complete Treatment System . . .VII-5
v

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LIST OF TABLES
Number
Title
Page
1
Federal Financial Assistance Programs	
. 1-6
2
Some Waterborne Illnesses and Causitive Agents . .
. II-3
3
Sample Turbidity Data Form 	
. II-6
4
Partial List of Nephelometric Turbidity Meter


Suppliers	.v	

5
Commonly Used Coagulating Agents 	
.III-7
6
Partial List of Coagulant Suppliers. . 	

7
Partial List of Gravity and Pressure Sand


Filter Suppliers 	
.111-26
8
Partial List of Diatomite Filter Vendors 	

9
Summary of Complete Treatment Design Data For


Packaged and Custom Designed Systems 	
. IV-9
10
System Design Approach For Small Water Systems . .
. IV-14
11
Package Gravity Filter Plants Design Concept . . .
. V-4
12
Itemised Construction Costs for Package Gravity


Filter Plants	
. V-6
13
Itemized Construction Costs for Package Pressure


Diatomite Filters	

14
Itemized Construction Costs for Package


Complete Treatment Plants		
. V-8
15
Itemized Construction Costs for Sludge Dewatering


Lagoons	
. V-10
16
Capital Recovery Factors for Some Combinations


of Interest (i) and Project Life (n) 	
. V-ll
17
Operation and Maintenance Summary for Package


Gravity Filter Plants	

18
Operation and Maintenance Summary for Package


Pressure Diatomite Filters 	
. V-15
19
Operation and Maintenance Summary for Package


Complete Treatment Plants	
. V-16
20
Sample Cost Analysis for a 140 gpm Complete


Treatment Plant	

21
Carlisle Suburban Authority, Pennsylvania


Plant Data 	

22
Hancock, Maryland Plant Data 	
.VII-7
vi

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I. SUMMARY AND OVERVIEW
PURPOSE AND STRUCTURE OF THIS
MANUAL
This document has been prepared to
aid water utility owners, engin-
eers , managers and operators in
understanding and dealing with
excess turbidity levels in the
water supply. It is intended to
be used for defining the problem,
developing and evaluating proposed
solutions, explaining to utility
customers the need for turbidity
control, and understanding opera-
tional considerations. Finally,
it explains a method to estimate
the costs associated with install-
ation and operation of turbidity
removal systems.
This handbook is designed as a
technical guide to turbidity
removal for those smaller size
systems that have decided that
turbidity control is desirable.
This document contains no
regulatory policy and does not
obligate systems to use any
treatment or nontreatment
technique to reduce turbidity
concentrations. If appropriate,
those regulatory requirements are
or will be established by the
primacy agency as part of its
implementation of the Primary
Drinking Water Regulations.
The handbook is divided into seven
sections, plus references and an
Appendix, as follows:
Section
I -Sumaary and Overview
II Introduction - discusses
sources of turbidity in
drinking water, health
effects, federal drinking
water regulation, and meth-
ods for turbidity analysis
in drinking water.
Ill Nontreatment and Treatment
Alternatives - different
approaches to solving ex-
cess turbidity problems.
IV Design of Turbidity
Removal Systems -
turbidity removal system
types and some suppliers;
design factors and
suggested specification
items.
V Cost estimating procedures
and Funding Sources-
Provides a method for
determining capital and
operation and maintenance
costs; sources of loans,
grants and other financial
assistance.
VI Operation and Maintenance
- guidelines for setting up
and running O&M and monitor-
ing programs.
VII Case Histories - experi-
ences of several utilities
which are removing excess
turbidity from drinking
water supplies.
This document is written for the
owners, engineers and operators of
smaller water systems, serving up
to 6,000 persons at a flow rate of
up to 500,000 gallons per day
(1892.5 cu.m./day). Although the
information contained herein may
be useful to larger utilities, it
is intended primarily to support
the water quality improvement
efforts of smaller utilities that
1-1

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may lack the technical and finan-
cial resources of the larger sys-
tems.
This document is not intended as a
substitute for professional ad-
vice for site-specific problems.
These should be approached in con-
sultation with the state agency
having primary enforcement respon-
sibility for the SDWA and compe-
tent professional engineers.
The abbreviations and units used
in this document are defined in
Appendix A.
WHEN TURBIDITY IS A PROBLEM
The term turbidity is an expres-
sion of the optical property that
causes light to be scattered and
absorbed rather than transmitted
in straight lines through a liquid
sample. In water, it is caused by
the presence of suspended matter
(e.g., clay, silt, algae). Typi-
cally, water sources become turbid
as a result of erosion, waste dis-
charges, aquatic weeds and algae,
and decay of surface vegetation
which falls or is washed into the
water.
Generally, moderate amounts of tur-
bidity are not a direct health haz-
zard. However, turbidity can
interfere with the action of disin-
fectants thereby allowing disease
causing organisms in the water to
survive and multiply. For this
reason, it is important to control
turbidity in public water sup-
plies. Accordingly, the National
Interim Primary Drinking Hater
Regulations (NIPDWR), resulting
from the 1974 Safe Drinking Water
Act, specify average monthly and
two-day maximum turbidity levels
of 1 NTU* and 5 NTU* respectively.
* Nephelometric Turbidity Units.
To meet these standards, most
surface waters and some ground
waters require treatment.
ALTERNATIVE METHODS USED TO REDUCE
EXCESS DRINKING WATER TURBIDITY
Figure 1 depicts the nontreatment
and treatment alternatives discuss-
ed in this Manual. Treatment for
turbidity removal can involve
significant costs. Therefore,
nontreatment alternatives deserve
close scrutiny before a treatment
plant is selected. For example,
it may be possible to switch from
surface to ground water sources of
acceptable turbidity. Alternative-
ly, your system might join with
other systems in an existing or
new regional system, thereby
benefitting by economies of scale
in plant construction and opera-
tion.
Whether you use a packaged (preman-
ufactured) or custom designed and
constructed** plant, it will proba-
bly feature the processes shown in
Figure 2. Process elements are as
follows:
•	Coagulation - Addition of
relatively small quantities of
coagulating chemicals to a tur-
bid water will cause finely div-
ided solids to clump together,
or coagulate, aiding in their
removal in subsequent process-
es. The chemicals must be com-
pletely and rapidly mixed with
the influent water to most
effectively meet this objec-
tive .
•	Flocculation - Gently
stirring coagulated waters
** The term "custom" used here
describes plants that have each
stage of the process individual-
ly designed and constructed.
1-2

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NON - TREATMENT	TREATMENT
-watershed and reservoir
management
-source substitution
cooperative efforts
•	join existing system
•	organize new system
-offline storage
-reservoir/raw water
management
-custom designed water
treatment plants
-packaged treatment
plants
•	direct filtration
•	complete treatment
Figure 1. Nontreatment and Treatment Alternatives for Turbidity Removal
Chemicals,
wattr

D
It®

Chemical addition/ Flocculation
rapid mixing
-Solid*
Settling	Filtration
Figure 2. Water Treatment Process for Turbidity Removal

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under controlled conditions
(flocculation) causes further
aggregation of the solids in
the treated waters.
•	Clarification - The
flocculated solids will then
settle in a clarifier, a
quiescent settling vessel with
provision for solids removal.
•	Filtration - Solids remaining
after settling are removed in a
filter by entrapment and strain-
ing. Usually, a gravity filter
with a bed of sand and/or
anthracite coal is used.
Packaged treatment systems, for
direct filtration or complete
treatment are generally the most
economical for small water utili-
ties. Direct filtration should
only be used where close operator
supervision can be provided.
Otherwise, packaged complete treat-
ment is recommended. Figure 3 is
a typical packaged complete treat-
ment system, suitable for use by a
small water utility. The plant is
factory assembled and shipped to
the plant site ready for hook up
to utilities and clear water
storage. It is semi-automatic and
thus does not require continuous
operator supervision.
Depending on the size of the facil-
ity, the cost of a packaged plant,
delivered, set up and housed in a
prefabricated building, can be as
little as one-half the cost of
installing a custom designed and
constructed plant.
Operation and maintenance (O&M)
costs are also somewhat reduced
due to the simplicity, service-
ability and automated features of
packaged plants.
Jtj. Raw Water
Flocculator
Settling
Chamber
Mixed Media
Filter
Courtesy: NEPTUNE
Microfloc, Inc,
Figure 3. Typical Packaged Complete Treatment Plant
1-4

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Selection of the appropriate pack-
aged system begins with fully de-
fining the application. For
example:
•	Water quality - characteris-
tics of the water source includ-
ing quality and variability of
suspended and dissolved solids,
turbidity, alkalinity and hard-
ness, and presence of signifi-
cant color levels.
•	Plant sice - hourly, daily,
weekly and annual flow and sea-
sonal variation; expected
future demand growth.
•	Site constraints - available
land area and topography, cli-
mate, special waste disposal
problems.
•	Available O&M Resources -
availability (hours per day and
per week) and skill levels of
plant operators, and basic
laboratory facilities for pro-
cess monitoring.
Turbidity removal processes gener-
ate waste which must be disposed
of properly. Typically,
coagulation and settling processes
require disposal of dilute
gelatinous sludge. Filter
backwashing (cleaning) produces
several thousand gallons per day
of turbid wash water at the
average 250,000 gpd (946.2
cu.m./d) plant. Settling and
recirculation of clear water,
discharge to local sewers, sludge
hauling to landfill, lagooning and
sand drying beds are some waste
management approaches used by
small water systems.
In some cases, it is possible to
reduce the size and cost of
turbidity removal systems by
protective supervision and
maintenance of your watershed.
Supervision of development and
agricultural activities to limit
erosion on the watershed is one
example of watershed management.
If your system is equipped with
off stream raw water storage, you
could reduce treatment costs by
switching from river intakes to
stored supplies during episodes of
high turbidity, such as might
occur after heavy rains.
COST ESTIMATING PROCEDURES AND
FUNDING SOURCES
Section V explains a procedure
that can be used for estimating
treatment and operation and
maintenance costs.
Costs cited in the examples and
cost curves provided in this
handbook are estimated data
generated from a variety of
sources. Adjusting cost figures
for inflation is also discussed in
Section V.
Sources of financial assistance in
the form of loans, loan
guarantees, or outright grants are
very limited. The principal
federal financial assistance
programs available are shown in
Table 1.
OPERATION AND MAINTENANCE
Operator requirements for turbidi-
ty removal systems depend on the
plant size, raw water characteris-
tics, and equipment selected.
Packaged systems are generally
semi-automatic, freeing the plant
operator to carry out routine or
repair maintenance. These systems
are also usually designed to allow
for intermittent operation. Thus,
you may be able to schedule water
production for one or two shifts
daily, or only during weekdays,
reducing operator costs.
1-5

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TABLE 1
FEDERAL FINANCIAL ASSISTANCE PROGRAMS
Agency
Farmers Home Administration	1.
2.
3.
Department of Interior	1.
2.
Department of Housing and Urban 1.
Development
Program Description
Cooperative grants up to 75 per-
cent of project cost for public-
ly owned rural systems serving
fewer than 10,000 persons.
Loan gurantees up to 90 per-
cent of loan face value for
public or private rural
utilities, emphasizing those
serving fewer than 2500 persons.
Direct loans up to 75 percent
of project cost.
Direct loan programs for non-
federal entities in the 17
western states.
Financial assistance for systems
serving American Indians.
Community Block Development
Grant Program.
Plant operators need to be proper-
ly trained. For systems using
complete treatment, this includes
control and monitoring of coagula-
tion. This requires good basic
understanding of coagulation chem-
istry and test methods for alkalin-
ity, pH and turbidity. Knowledge
of disinfection techniques and
ability to measure disinfectant
application rates and residuals is
also necessary.
Selection of a packaged treatment
system should include a thorough
review of spare parts and special-
ized service needs. Do not pur-
chase a plant from a vendor who
cannot supply service support and
shipment of critical spare parts
on short notice. Chemical feed
equipment and instrumentation are
particularly important. A servic-
ing representative should be avail-
able on short notice, as the util-
ity's servicemen may not be quali-
fied to repair this equipment.
Stock all recommended chemical
feed system spare parts. Provide
specific training to operators on
routine maintenance and repair,
and make sure that several copies
of detailed service manuals are
available on site.
SUMMARY
Systems faced with the need to
reduce excessive turbidity in the
water supply can use a variey of
nontreatment approaches, or
install a treatment system. This
handbook describes the design
rationale used for developing a
1-6

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simple, reliable and cost	individual water utilities are
effective system for turbidity	also offered and a reference that
control. Suggestions for	discusses regionalization options
nontreatment approaches by	in detail is provided.
1-7

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II. INTRODUCTION
DEFINITION AND CAUSES OF TURBIDITY
Turbidity is an expression of
the optical property that causes
light to be scattered and absorbed
rather than transmitted in
straigh^ lines through a liquid
sample.
Turbidity in water is caused by
any suspended matter which inter-
feres with the clarity of the
water. This may include clay or
silt, algae, and other organic or
inorganic compounds.
Typical sources of turbidity in
drinking water include the follow-
ing (See Figure 4):
•	Waste discharges.
•	Runoff from disturbed or erod-
ing watersheds.
•	Algae or aquatic weeds and pro-
ducts of their breakdown in
water reservoirs, rivers, or
lakes.
•	Humic acids and other organic
compounds resulting from decay
of plants, leaves, etc. in
water sources.
•	High iron concentrations which
give waters a rust red colora-
tion.
Erosion of rocks
and minora! deposits
Figure 4. Typical Sources of Turbidity in Surface Waters
II-l

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SIGNIFICANCE OF TURBIDITY TO HUMAN
HEALTH
Excessive turbidity in drinking
water is not only unsightly, but
also may be a health hazard:
•	Turbidity can provide food for
microbes, promoting their re-
growth in the distribution sys-
tem.
•	Turbidity interferes with ion
exchange and carbon adsorption
processes, and may interfere
with laboratory analysis of
water quality.
•	Turbidity causing suspended
particulate matter can absorb
toxic substances, providing a
medium to concentrate and trans-
port these substances.
Of greatest concern, turbidity
can interfere with disinfection,
allowing disease causing patho-
genic organisms to enter the
distribution system.
In effect, the particles of turbi-
dity provide "shelter" for mi-
crobes by reducing their exposure
to attack (Figure 5). Turbidity
also reacts with chlorine disinfec-
tants directly, causing quick
depletion of disinfecting power,
possibly allowing disease causing
pathogens to survive and be passed
into the distribution system.
Table 2 summarizes the principal
waterborne diseases, mechanism of
attack and symptoms, and health
effects associated with waterborne
organisms. Many of these illness-
es are potentially fatal, particu-
larly for more vulnerable members
of the population: the very young
or old, or those in poor health
for other reasons. There is no
"safe" level of microbial pollu-
tion in drinking water. A dose
which may not cause infection in
one person may cause fatal illness
in another, even though both are
similar in age, background and
physical health.
For a more detailed discussion of
waterborne illness and disinfec-
tion techniques, the reader is
referred to the following publica-
tion: "Micro-organism Removal for
Small Water Systems." It has been
prepared as a companion to this
document and is available from the
U.S. Environmental Protection
Agency, Office of Drinking Water,
401 M Street, SW, Washington, DC
20460.
Turbidity from decaying vegeta-
tion can react with free chlorine
to form trihaloswthanes, com-
pounds that have been implicated
in human cancer. One of the tri-
halomethanes, chloroform is a
particularly toxic by-product of
the reaction of free chlorine and
organic turbidity.
Asbestos, a mineral fiber which
occurs naturally over much of the
U.S., will cause turbidity when
present in high concentrations.
Inhaled asbestos has been identi-
fied as a carcinogen (cancer caus-
ing substance); therefore, it is
wise to control and remove it from
public drinking water supplies.
THE SAFE DRINKING WATER ACT
The Safe Drinking Water Act (SDWA)
became law on December 16, 1974.
It mandated the U.S. Environmental
Protection Agency (EPA) to develop
and implement regulations to
enforce the Act. The Rational
Interim Primary Drinking Water
Regulations (KIPDHK) resulted
from this mandate. The regula-
tions are being implemented in two
steps:
II-2

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TABLE 2
SOME WATERBORNE ILLNESSES AND CAUSATIVE AGENTS*
Illness
Typhoid Fever
Paratyphoid Fever
Bacillary Dysentery
Cholera
Amoebic Dysentery
Infectious Hepatitus
Giardiasis
Gastroenteritis
Agent
Salmonella typhi, (bacterium)
Salmonella paratyphi, (bacterium)
Shigella species, (bacterium)
Vibrio cholerae, (bacterium)
Endamoeba histolytica, (protozoan)
Hepatitus A Agent, (virus)
Giaridia lamblia, (protozoan)
Rotavirus, Norwalk Agent, (viruses)
Campylobacter Jejuni, Yersinia
Enterocoliticus, (bacterium)
As well as other bacteria and viruses.
*From "Micro-organism Removal For Small Water Systems.'
Protected
micro-organisms
Particulates
Exposed
micro-organism
Figure 5. Protected and Exposed Micro-Organisms^
II-3

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• The interim (initial) regula-
tions, which became effective
June 24, 1977.
• The revised regulations;
changes to the regulations as
health studies and treatment
technology reviews on various
contaminants are completed.
A public water system is defined
in the NIPDWR and can be described
as follows:
ANY PUBLICLY OR PRIVATELY OWNED
DRINKING WATER SUPPLY WITH AT
LEAST 15 SERVICE CONNECTIONS,
SERVING AT LEAST 25 PERSONS
FOR A.MINIMUM OF 60 DAYS PER
YEAR.
The NIPDWR applies to both c
-------
Note that these standards alone
do not assure that the water will
be microbiologically safe. Ade-
quate disinfection is also re-
quired. Some organisms, such as
Giardia cysts (Protozoa) can pass
through granular media filters and
be present even where turbidity is
1 NTU or less. Giardiasis in
humans, a dysentery like illness,
may result if treatment and disin-
fection are inadequate to remove
or kill the cysts.
NIPDWR Sampling and Analysis
Requirements
Turbidity sampling requirements
are outlined in Section 141.22 of
the NIPDWR. They require daily
turbidity samples for systems
using surface water. This applies
to both community and noncommunity
systems. At state option, ground
water users may be required to
sample regularly for turbidity as
well.
The samples must be taken at the
point that the treated and disin-
fected water enters the distribu-
tion system. This must be done
wherever a different treated sur-
face water enters the system.
Figure 6 depicts an example of
these requirements. In addition
to routine sampling, check samples
are required if the maximum
contaminant level exceeds the
limit. The check sample should be
taken within 1 hour. If this
sample also exceeds the limit, you
must report to the state within 48
hours.
The NIPDWR currently recognizes
only one method of turbidity analy-
sis, the nephelonetrie method.
Results are reported as Turbidity
Units (TUs) or nephelometric turbi-
dity units (NTUs). An explanation
of this method and how it compares
with other turbidity measures is
given later in this Section.
NIPDWR Recordkeeping and Report-
ing Requirements
Reporting and recordkeeping
requirements are outlined in
Sections 141.31 and 141.33 respec-
tively of the NIPDWR.
The NIPDWR requires public water
systems to keep a daily record of
turbidity measurements and to
retain, at minimum, a summary of
test results for K) years.
Records of any variances or
exemptions granted for turbidity
must be retained for 5^ years
after their expiration. Any
actions taken to correct a
turbidity violation must be
recorded and filed for at least 2
years following the last recorded
action.
Table 3 from Reference 5 is a
sample turbidity record form. It
can be used to set up a turbidity
record or it can be adapted to
meet any specialized need. In any
case, this form provides space for
all of the information needed to
be recorded from daily turbidity
analyses and any additional check
samples.
The NIPDWR requires two types of
reporting by public water utili-
ties :
• Reporting to the State
• Public notification
The state receives routine and
check sampling and analysis
reports, plus violation reports.
Public notification via mail, news
paper, and radio/television may be
required for violations of the
MCLs or monitoring requirements.
II-5
-------
Table 3^
Sample Turbidity Data Form

Routine Sampla
Cnack Simple
Value Used
Too-Day Average
Ot TurMMy
Oat*
1
Sampled
by loc
2
Time
3
VaiuaiTut)1"
4
Time
9
V«iu e
Sum
•
a«o
10
1

1-2

2-1

3-4

4 - S

8-6

6-7

7-9

9- 10

10* 11

11 • 12

12- 13

13- 14

14-is

16-16

16- 17

17-16

16-19

19-20

20-21

21-22

22 - 23

23-24

24-25

2S-26

26-27

27-26

26-29

29-30

30-31

TfttAI
WATER
MONTHLY TOTAL TUl SVBTFM
AVERAGE 111 * Day* in Uanth ID*
Nam. 0- Walar Supply |yp,o,IWfum#n,UMd M0N™
—— (a) U value aiCHOt 1 TU lake chacfc tampl* within ont ho*
(b) Um value* Irom origmel tampiet en day* MCL on no) MCMid
and shack Mmpl* vaiuM lor deyi the MCL wit a«c«Mad
2
Id) M monthly ivwa^* • mora than 1 TU. tapen w aula and notdy ma puOfcc
11-6
-------
Sompl*
point->
Sample
point
Treatment
Plant
~ ~~~~~
Figure 6. Turbidity Sampling Points for a Small Water System Using
Surface Waters
Recommended Reading
A complete synopsis of the N1PDWR
requirements, including MCL's,
sampling and analysis, reporting
and recordkeeping is available
from the American Water Works
Association:
The Safe Drinking Water Act—
Self Study Handbook, Community
Water Systems, American Water
Works Association, 6666 W.
Quincey Avenue, Denver,
Colorado 80235
It provides information on
compliance with the Federal
drinking water regulations. For
answers to specific questions,
contact the agency having primary
enforcement responsibility within
your State.
SAMPLING AND ANALYZING FOR TURBIDI-
TY
Turbidity Sampling
Since the turbidimeter will detect
any interference in the light path
regardless of source, cleanliness
of sample bottles and strict adher-
ence to standard procedures are
required for accurate analysis.
These sampling procedures should
be followed closely:
1. Use a clean, widemouth con-
tainer specifically designed
for water e^pling. Glass or
polyethylene bottles with plas-
tic sealing lids are recom-
mended .
2. Rinse the sample container 2
to 3 times with free flowing
water from the sample tap
before taking the sample.
II-7
-------
3. Take the sample and cap it
immediately. Test the sample
as soon as possible (prefer-
ably within a few hours after
collection). Do not add
anything to preserve the
sample. Storage over one day
is not recommended as irrever-
sible changes in turbidity
may occur.
Turbidity Analysis
As noted previously, there is only
one test method approved for turbi-
dity monitoring under the NIPDWR:
The nephelometric method. The
measured unit of turbidity is the
NTU (nephelometric turbidity
unit). You may be more familiar
with the older Jackson candle
turbidimeter. This device, still
in widespread use for various
water and wastewater uses, mea-
sures turbidity in terms of Jack-
son Turbidity Units (JTUs). The
basic difference between the units
is shown in Figure 7. The nephelo-
metric unit measures the light
scattered at right angles by the
sample; the Jackson Candle turbidi-
meter measures both the scattered
and direct light as viewed through
the sample. There is no general
correlation between the NTU and
the JTU. All NIPDWR standards and
EPA documents that refer to Turbi-
dity Units (TUs) are using NTU
measurements.
To measure NTUs you will need a
nephelometric turbidimeter and
standard solutions which are used
to calibrate the meter before each
test. The meter must be able to
detect turbidity from 0 to 40
NTUs. Appendix B provides a
sample specification for an accep-
table turbidimeter. Table 4 lists
some vendors of turbidimetric
equipment.
Reference standard solutions can
be obtained from the following
sources:
• Laboratory equipment suppliers
• Local state certified labora-
tories
• Preparation in your labora-
tory
You should ask the turbidimeter
supplier for a list of certified
standard suppliers. Alternative-
ly, you may be able to have a
local, state certified laboratory
prepare reference standards at rea-
sonable cost. Note that standard
solutions must be replaced periodi-
cally. Try to locate a reliable
supplier as nearby as possible.
Perhaps a large water utility in
your area could be used as a
supplier since they may be
preparing standard solutions for
their own use.
Preparation of reference stand-
ards requires precision equipment
and trained personnel. You should
not prepare them in-house unless
you are equipped to.do so. Refer
to Standard Methods and Refer-
ences 5 and 6 for the procedures
and equipment used to prepare
reference standards.
Potential Interferences^
• Floating debris and rapidly
settling particles can cause
low readings. Retake those
samples where debris (large
particles) is present.
• Dirty, scratched or etched
tubes cause high readings. Re-
place these immediately. Do
not touch the body of the tube
where the light passes through.
II-8
-------
# Phototube
Phototube
Somple <)=»
NEPHELOMETRIC TURBIDIMETER CONVENTIONAL TURBIDIMETER
Figure 7. Comparison gf Nephelometric and Jackson Candle Turbidity
Measurement
7 9
Table 4. Partial List of Nephelometric Turbidity Meter Suppliers '
Bristol Babcock Division
40 Bristol Street
Acco Industries, Inc.
Waterbury CT 06708
Fisher Scientific Company
711 Forbes Street.

Pittsburgh, PA 15219
Hach Company
Box 389, Loveland, CO 80537
Roberts Filter
6th & Columbia Avenue
Manufacturing Co.
Darby, PA 19023
Sherman Machine
26 E. Main Street
and Iron Works
Oklahoma City, OK 73104
Technicon Industrial Systems
511 Benedict Avenue, Tarrytown, NY 10591
The Turbitrol Company
415 E. Paces Ferry Road, Box 12047

Atlanta, GA 30355
Turner Designs
2247A Old Middlefield Way,

Mountain View, CA 94043
II-9
-------
Condensed water on the exterior
of the sample tube gives erro-
neous results. This is impor-
tant when measuring turbidity
of cold waters.
Air bubbles cause high read-
ings. Make sure that the
sample is free of air bubbles
before taking readings.
Vibration during the test can
cause high readings. Put the
meter on a flat surface in an
area that is not affected by
vibration. Don't touch the
meter or the surface it is on
while the reading is being
made.
• Different sample volumes may
produce different results. Be
sure that you follow the direc-
tions with your meter and use
only the specified sample
volume.
• Color causing agents that
absorb light may cause low read-
ings. Be aware of the possi-
bility and visually check for
sample coloration prior to
test. Discard suspect samples
and retest.
• Turbidity causing substances
can settle if the sample is
allowed to stand for even a
short period. All samples
should be shaken vigorously
before testing.
11-10
-------
III. MEASURES TO TAKE IF THE TURBIDITY IS EXCESSIVE
INTRODUCTION
If it is determined that the turbi-
dity level is excessive, two
general approaches to reduce the
level should be evaluated:
• Nontreatment Alternatives
• Treatment Alternatives
Each is discussed in this section.
Economic and engineering data
which further aid in the analysis
of treatment and non-treatment
alternatives is given in Section
IV.
NONTREATMENT ALTERNATIVES
Small water systems faced with
upgrading or installation of new
facilities needed to meet turbi-
dity standards may find that the
nontreatment approach is the most
economical. The "manufacture" of
safe potable drinking water is
subject to economies of scale as
most other manufacturing process-
es; that is, it is cheaper to
process and sell it in larger quan-
tities. Also, it is generally true
that the closer that the original
water quality is to the desired
final water quality, the lower
processing costs are.*
Before adding treatment equipment
for turbidity control, evaluate
the nontreatment alternatives.
* Exceptions occur when polymer
or clay must be added to water
to enable the removal of the
turbidity-causing substances.
For example:
• Water source management.
Contaminants and turbidity
enter surface waters as a
result of overland flow and
stream impoundment pollution.
If water quality tests indicate
substantial pollution, particu-
larly from turbidity, color,
and organic compounds, a water-
shed and reservoir study should
be carried out. Try to mini-
mize water contaminants at the
source to reduce the need for
expensiye treatment equipment
and large quantities of chemi-
cal! :
- Seek to control sediment rela-
ted turbidity by identifying
erosion sources such as agri-
cultural practices and land
development. Require
developers to provide runoff
and sediment control when
building on slopes. Use raw
water reservoirs or holding
ponds to presettle turbid
waters.
- Identify and control indus-
trial effluents. Monitor
suspended solids discharge
from upstream water and waste-
water plants. Control algal
growth in reservoirs.
- Protect the watershed and
reservoir from trash and
litter dumping, including
refuse, leaves and tree trimm-
ings and the like. If possi-
ble, limit public access to
areas adjacent to reservoirs.
• Water source substitution.
Required treatment and
disinfection costs are directly
related to raw water quality.
III-l
-------
NON
TREATMENT
WATERSHED AND
RESERVOIR
MANAGEMENT
SOURCE
SUBSTITUTION
COOPERATIVE
— join existing system
L—organize new system
TREATMENT
OFF LINE
STORAGE
PRESETTLING
CHEMICAL
TREATMENT
FLOCCULATION
h SETTLING
FILTRATION
PACKAGED COMPLETE
TREATMENT
CHEMICAL
TREATMENT
FILTRATION
PACKAGED DIRECT
FILTRATION
Figure 8. Nontreatment and Treatment Alternatives for Meeting NIPDWR
Turbidity Standards
III-2
-------
Costs could be greatly reduced
by switching from a turbid
surface water source to a clear
well water. Disinfection costs
would probably be reduced as
well.
• Regional Systems. Regional
systems are becoming more
attractive as the need to, and
costs of, producing high quali-
ty drinking water increase.
Larger systems can spread the
costs of water quality monitor-
ing and analysis, and of opera-
tion and maintenance, over a
larger user base, lowering per
capita costs. The analysis of
nontreatment alternatives
should look at regional alterna-
tives: either connecting to an
existing regional system, or
the formation of a new regional
utility by joining with other
nearby systems which may be
experiencing similar water
quality problems.
Several government agencies can
provide support to small water
systems interested in regionali-
zation. The Farmers Home Admin-
istration (FmHA) has the most
experience in dealing with
regionalization attempts, hav-
ing the largest federal grant-
loan program for rural water
projects. HUD, the Appalachian
Regional Commission, the Econo-
mic Development Administration
and the Coastal Plains Commis-
sion all have limited federal
funds available for rural water
projects, including regionaliza-
tion efforts by small water
systems.
Nontreatment alternatives which
involve regional systems are
discussed in detail in a companion
document, available as follows:
Regionalization Options for
Small Water Systems, U.S. EPA
Office of Drinking Water, 401 M
Street, SW, Washington, DC
20460.
TREATMENT ALTERNATIVES FOR TURBIDI-
TY REMOVAL
Removing turbidity will require
physical treatment, chemical treat-
ment, or a combination of the two.
As a general rule, the higher the
raw water turbidity, the more com-
plicated and costly the treatment
scheme required. Contaminants
which color the water may be diffi-
cult to remove but can be reduced
by some of the treatment tech-
niques used to reduce turbidity.
Figure 9 depicts the treatment pro-
cesses that are discussed in this
section. Each process discussed
below is a separate and discrete
treatment step, but all are inter-
related and must be considered as
part of an overall process scheme.
Traditionally, water treatment
plants have been constructed as a
series of separate processes.
Small utilities, however, can pur-
chase packaged treatment systems
which incorporate all of the pro-
cesses within a very compact hous-
ing. Design of these treatment
systems are discussed in detail in
Section IV:
• Direct Filtration
• Direct Coagulation and
Filtration
• Packaged Complete Treatment
Systems
III-3
-------
PRESETTLIN6
(OPTIONAL)
Alternative
Direct Filtration
CHEMICAL!
ADDITION
COAGULATION
• CHEMICAL ADDITION
• RAPID MIXING
FLOCCULATION
SETTLING
FILTRATION
F
ADJUSTMENTS TO
BASIC COAGULATION \
PROCESS TO OPTIMIZE*
| COLOR REMOVAL I
| (OPTIONAL) J
rToLYMERT
—|ADDITION |
J(OPTIONAL)j
Figure 9. Turbidity Removal from Drinking Water
III-4
-------
PRESETTLING
If your system uses surface water
of highly variable quality, but
has no raw water reservoir, use of
a holding pond of 1 to 3 days
detention should be evaluated.
The holding pond provides pre-
settling of the raw water allow-
ing silt and sand to settle out.
It also equalizes the flow to the
water treatment plant by averaging
out short term changes in raw
water quality. Equalization makes
plant operation simpler by reduc-
ing the need to adjust treatment
chemical dosages. Also, if not
removed, abrasive grit and other
solids may shorten the life of
pumps and other mechanical parts
of the treatment plant.
Certain raw water supplies may sup-
port rapid growth of nuisance aqua-
tic organisms, such as algae, when
held in equalization ponds. Be-
fore opting for the use of ponds,
investigate this possibility dur-
ing the initial stage of plant
design. In some cases, algae
growth can be controlled through
the application of copper sulfate
(CuSO.).
4
COAGULATION
Coagulation is a process that
aids in the aggregation of small,
hard to settle, particles into
larger ones that can be removed by
gravity (sedimentation) and/or by
filtration. Coagulating chemi-
cals are added to a turbid water,
creating conditions that allow the
formation of floe, or groupings
of particles. As seen in Figure
10, coagulation is the first step
in the solids (turbidity) removal
process.
Chemical coagulants initiate parti-
cle aggregation by three main
mechanisms: electrical charge
reduction, interparticle bridg-
ing, and enmeshment. These are
illustrated in Figure 11. Floccu-
lation, discussed later herein,
continues the process of particle
aggregation.
Coagulating Chemicals
The chemicals most commonly used
for coagulating solids in potable
water treatment are listed in
Table 5 along with their chemical
formulas and typical dosage
ranges. Dosage for a specific
water must be determined by actual
testing of the raw water. Coagu-
lant combinations may be used to
reduce overall chemical costs.
For example, it is becoming quite
common to combine a traditional
coagulant such as alum with organ-
ic polymers to reduce overall
chemical consumption, sludge pro-
duction and costs.
Jar tests are the simplest proce-
dure for selecting optimal chemi-
cal type and dosage. Figure 12 is
a photograph of a typical jar test
apparatus. Appendix C details the
procedure for conducting jar
tests. Basically, the test is sim-
ple. Varying amounts of a coagu-
lant are added to samples of the
raw water in each of six stirred
beakers and the results are observ-
ed. Initial mixing is rapid, fol-
lowed by gentle mixing. The test
is repeated for the full range of
practical dosages and for various
coagulants. The coagulant and
dosage which flocculates the raw
water most effectively is used to
approximate coagulant needs for
the full scale installation. Jar
tests can be conducted by many
laboratories, colleges and univer-
sities, and some consulting engi-
neers. Most chemical vendors will
also assist you in determining op-
timum chemicals and dosages. Some
chemical suppliers are listed in
Table 6.
III-5
-------
Chemical*
Raw
water
Coagulating chemicals Flocculation Sedimentation Filtration
added/rapid mixing
Figure 10. Coagulation/Flocculation/Sedimentation/Filtration
ELECTROSTATIC
CHARGE REDUCTION
coagulant I
added I
1NTERPARTICLE
BRIDGING
oo
coagulant
added
i
oo
EMMESHMENT
°o°
o o
coagulant
added
I
coagulant
molecule
Hydroxide
The larger particles thus formed can be settled by gravity or filtering.
Figure 11. Mechanisms of Chemical Coagulation
III-6
-------
Table 5
Commonly Used Coagulating Agents
Name
Aluminum Sulfate
Sodium Aluminate
Alone
Chemical Reaction
A12(S04) + 3Ca(HC0) =
3CaS04 + 2A1(0H)3 + 6C(>2
NaAlO + Ca(HCO ) + HO
Al(OH73 + CaC03 + NaHC03
Aluminum Sulphate- 6AnAlO_ + A12(S0),)3,18H„0
Sodium Aluminate 8A1(0H7, + 3Na„S0. + 6H-0
2 4
Dosage Range
15 to 100 mg/1 of A12(S04) ,
18 H20 (commercial) according to the
turbidity of the water.
5 to 50 mg/1 of ^2^3 (commer-
cial) according to the turbidity of
the water.
The weight of commercial sodium alu-
minate required is 75% of the weight
of aluminum sulphate (commercial) for
an equimolecular reaction. The dose
of sodium aluminate may, however, be
much less, in which case the reagent
serves only to initiate the coagula-
tion of the aluminum sulphate.
Sodium Aluminate + 3NaAlO„ + FeCl,, 6H2 =
Ferric Chloride 3Al(OH7, + Fe(OH), + 3NaCl
Ferric Chloride
Alone
2FeCl_ + 3Ca(HC0)_) =
3CaCl2 + 2Fe(0H)3 + 6C02
Approximately equal weights of commer-
cial sodium aluminate (50Z A^2°3
and FeCl3. 6H2 (commercial)
to 100 mg/1 FeClj, 6H- (comm
ial) according to the turbidi
5
cial) according
the water.
commer-
ty of
Aluminum Sulphate + A1«(S0,)3 + 3Ca(0H)2
Hydrated Lime 3CaS04 + 2A1(0H)3
One part of Ca(OH)2 (lime) to three
parts of A1 (S0,)3> 18H2
(commercials• Lime is added to coun-
teract the acidity of alum.
(Continued)
-------
Table 5
Continued
Name
Aluminum Sulphate +
Caustic Soda
Chemical Reaction
A12(S0,)_ + 6NaOH =
2Al(OH)3 + 3Na2S04
Aluminum Sulfate +
Sodium Carbonate
Ferric Sulphate:
A1-(S0.) + 3Na CO + 3H 0 =
2a1(OH7, + 3Na SO + 3C0,
A1_(SO,7_ + 6Na CO + 6IT0 =
2Al(0HJ- + 3Na SO + 6NaHC0,
3 2 4 3
Fe2(SO.) + 3Ca(HC0.) =
2Fe(OH7, + 3CaS0. + 6C0„
3 4 2
Ferric Sulphate +
Hydrated Lime
Fe2(SO,)3 + 3Ca(0H), =
2Fe(OH)3 + 3CaS04
Ferrous Sulphate
FeSO. + Ca(HCO,)_ =
Fe(OH)2 + CaSO^ + 2C02
Ferrous Sulphate + FeSO, + Ca(0H)_ =
Fe(OH>2 + CaS04
Hydrated Lime
(Continued)
Dosage
The requirement of NaOH (caustic soda)
is 36% of the dose of A1 (SO.)
18 H2 (commercial).
One part of anhydrous sodium
carbonate to 1 or 2 parts of A1?(S0.) .
18H20 (commercial).
10 to 50 mg/1 of Fe2(S0 )3,
9H20 (commercial) according to the
turbidity of the water.
The requirement of hydrated lime as
Ca(0H)2 is 40Z of the quantity of
iron sulphate Fe2(S04)3, 9H20.
5 to 25 mg/1 of FeSO^, 7H20
(commercial) according to the turbidi-
ty of the water. In aerated waters,
the ferrous hydroxide oxidizes and be-
comes ferric hydroxide: 2Fe(0H) +0+
H20 = 2Fe(0H)3
The requirement of Ca(0H)2 (hydra-
ted lime is 26Z of the quantity of
FeS04> 7H20.
-------
Table 5
Continued
Name
Ferrous Sulphate +
Chlorine
Sodium Aluminate +
Magnesium Chloride
Ozone
Chemical Reaction
2FeS0, + 3Ca(HC03)2 + Cl, «
2Fe(0H)3 + 2CaS0^ + CaCl^ + 6C02
2AlNaO. + MgCl. + 4H.0 =
2A1(0H73 + Mg(OH)2 + 2NaCl
Dosage
The requirement of chlorine is 12% of
the quantity of FeSO^. 7H20.
The requirement of MgCl2. 6H2 is
125% of the weight of commercial
sodium aluminate (with 50% A^O^).
Ozone is not a true coagulant as it has no action on the electric charges of
the colloids in the water. However, in specific cases when water contains
complexes linking organic matter to iron or manganeses, ozone can initiate a
coagulation process. The complexes are destroyed by the ozone and the metal
ions thus released are oxidized. With the necessary pH conditions, this may
result in the formation of a small amount of a generally fragile precipitate.
The density and cohesion properties of the floe so formed are inadequate to
provide acceptable clarification, but may serve for filter coagulation.
-------
7 8 9
Table 6. Partial List of Coagulant Suppliers ' '
Name
Address*
Allied Chemical, Indus-
trial Chemicals Division
Box 1139R, Morristown, NJ 07960
Allied Colloids, Inc.
161 Dwight Place, Fairfield, NJ 07006
American Colloid, Inc.
5100 Suffield Ct., Skokie, IL 60076
American Cyanamid
Wayne, NJ 07470
Calgon Corporation
Box 1346, Pittsburgh, PA 15230
Carus Chemical Co.
1500 8th. St., LaSalle, IL 61301
Diamond Shamrock Corp.
351 Phelps Ct., Irving, TX 75062
Dow Chemical, USA
2020 Dow Center, Midland, MI 48640
Dupont Chemicals
Chemicals & Pigment Dept.
Wilmington, DE 19898
Hercules, Inc.
910 Market St., Wilmington, DE 19899
Jones Chemical Corp.
100 Sunny Sol Blvd., Caledonia, NY 14423
Leopold Company
227 S. Division St., Zelienople, PA 16063
Nalco Chemical
2901 Butterfield Rd., Oak Brook, IL 60521
Olin Corporation
Chemicals Group, 120 Long Ridge Rd.,
Stamford CT 06904
Permutit Co.
E. 49 Midland Ave., Paramus, NJ 07652
Petrolite Corp.
Tretolite Division
369 Marshall Ave., St. Louis, M0 63119
Rohm & Haas Co.
Independence Mall W., Philadelphia, PA
19105
Stauffer Chemical Co.
New York, NY
* National headquarters. Many of these vendors have regional branch
offices or local representatives.
111-10
-------
mmmm
l-.-;Jif-V.H i4'"i
pjr'f**}A**ir«*A• "*^fiWl«;*r*
Figure 12. Jar Test Apparatus
Characteristic Chemistry of the
Common Coagulants
ALUM, an acidic compound, reacts
with the alkalinity (carbonate and
bicarbonate) of natural waters to
form aluminum hydroxide, a fluffy
white flocculating agent. Mixing
alum in water causes it to break
down as shown by the equations
below:
A12(S04)3 » 2A1+++ + 3S04 -
alum
It then combines with ionized
water,
6H,0 —+ 6H+ + 60H~
water hydrogen hydroxide
To form aluminum hydroxide, a
fluffy white coagulant:
2A1+++ + 60H~ —* 2A1(0H)3
aluminum hydroxy1 aluminum
ion ion hydroxide
In the process, hydrogen (H*)
ion is liberated, making the water
more acid. Unless lower pH (more
acidic condition) is required,
lime (Ca^lOg), soda ash
(Na.CO.), or caustic soda
(NaOH) may be needed to be added
to keep the pH in the optimum
range for effective coagulation.
Also, for each milligram per liter
(mg/1) of alum added, the sulfate
content of the water increases 0.5
mg/1. This may be important if
III-ll
-------
raw water sulfate is high or if
the plant uses ion exchange for
nitrate removal.
FERRIC SULFATE and FERRIC CHLOR-
IDE react in a similar manner as
alum to produce ferric hydroxide
(a fluffy white coagulant). As
before, water pH will be reduced
unless lime, soda ash, or caustic
soda are added.
FERROUS SULFATE and FERROUS CHLOR-
IDE react with the alkalinity of
the natural water or with added
alkaline materials (e.g., lime,
soda ash, caustic soda) to form
ferrous hydroxide (FeCOH^)* If
oxygen is present in the water or
it is aerated, the ferrous hydrox-
ide is changed to ferric hydrox-
ide. Ferrous hydroxide is slightly
soluble in water and thus may
cause high iron, content of the
treated water, causing stains on
consumers' plumbing fixtures.
SODIUM ALUMINATE (NaAK>2) is an
alkaline coagulant that can be
effective in relatively small
doses. It is expensive compared
to other chemicals and therefore
may be used in conjunction with
less expensive coagulants such as
alum. Sodium aluminate is not
effective if the raw water is vetfy
soft. When mixed with water,
aluminum hydroxide is formed as
the final coagulating agent.
LIKE (CaCOH)^) can be used for
coagulation as well as for pH
adjustment. Relative to other
coagulants, large quantities of
lime may be required for turbidity
removal, producing substantial
waste sludge which must be dispos-
ed. Lime treated waters, if not
properly stabilized, tend to
deposit calcium carbonate
(CaCOj) scale in consumers'
plumbing, particularly hot water
heaters.
POLY-ELECTROLYTES (polymers) have
synthetic or natural long chain
organic compounds of high
molecular weight that have
function groups (active sites)
along the length of the molecule.
These may be negatively charged
(anionic polymers), positively
charged (cationic polymers) or
uncharged (nonionic polymers).
Polymers can be used alone or as a
coagulant aid to improve the
performance of other chemicals.
They are quite costly and are
generally used in small dosages
(0.1 - 0.5 mg/1). Often, they are
combined with alum and dosed prior
to filtration, as a filter aid.
COAGULANT AIDS include polyelec-
trolytes, clays (such as benton-
ite) and activated silica. They
are added in conjunction with
other coagulants and serve to
enhance coagulation and minimize
chemical addition.
Chemical Feeding and Mixing
Coagulant chemicala are purchased
either in dry or liquid form, in
bulk, bag, or drums (for liquid).
Dry chemicals require fairly ela-
borate dissolving and feeding
equipment. Liquid feed systems
are somewhat simpler but their
chemicals are often more costly.
For effective chemical usage,
mixing with the process water
stream must be rapid and com-
plete. A high speed mixer, shown
in Figure 14, is often used.
Detention time (the time each unit
volume of water spends in the mix-
ing chamber) is typically 10 to 30
seconds. In-line mixers, blen-
ders and mixing pumps are also
used for rapid mixing (Figure 14).
111-12
-------
Dust
collector

ill pip* (pneumatic)
Bin gat*
Flexible
connection
DUST and VAPOR
REMOVER
Water
supply
ALTERNATE SUPPLIES
DEPENDING ON STORAGE
-Duet collector
Bag fill
—Screen with breaker
DAY HOPPER for
dry chemical from
bags or drums
Scole or sample chute
Mixer
Baffl*
Solenoid
valve
Control
valve
ROTAMETE
DISSOLVER
Level probes
TANK
Pressure reducing
valve
Water
supply
.Gravity to
application
- Pump to
{JT application
Figure 13. Chemical Dissolving and Feeding Equipment
-nm
¦Motor ft
drive-
Propellers

a) HIGH
SPEED
MIXER
b) IN-LINE
BLENDER
Mixing
•lament
c) IN-LINE
MIXER
Figure 14. Some Rapid Chemical Mixers
111-13
-------
Factors that Affect Coagulation
Coagulation effectiveness is depen-
dent on a complex interaction of
water characteristics which in-
clude pH, turbidity (magnitude and
variation), chemical composition
of the water and temperature. Of
these, the pH is the most impor-
tant single variable. The coagula-
tion process must be operated with-
in the correct pH range for the
coagulant being used if the pro-
cess is to be optimized and chemi-
cal dosage minimized.
Aluminum salts (alum) have been
shown to work best when applied to
a water of pH ranging from 6.0 to
7.8. Iron salts (ferric chloride)
behave similarly, thoug^the accep-
table range is broader. It
may be necessary to adjust the pH
of the raw water to optimize the
coagulation process. Jar testing,
discussed earlier in this section,
is used to find optimal coagula-
tion conditions.
Natural waters nearly always con-
tain inorganic salts (sulfates,
phosphates, carbonates, bicarbon-
ates) of varying concentration and
composition. These can affect
coagulant choice and dosage. For
example, sulfate ion concentration
affects the optimal pH range for
chemical application, while
increasing phosphate concentration
tends to shift the optimum pH down-
ward toward more acidic condi-
tions. It has been generally con-
cluded that anions (negatively
charged ions) affect coagulation
more than cations (positively
charged) and that they tend to
move the optimum coagulatio^gpH
range toward the acid side.
The nature of the suspended solids
turbidity) being coagulated also
affects coagulant selection and
dosage. In general, there is a
minimum dosage requirement for co-
agulation of turbidity caused by
clay, regardless of turbidity con-
centration. Above the minimum,
required dosage increases at a
declining rate with increasing tur-
bidity concentration. Very high
turbidity may be coagulated with
relatively small coagulant dosages
due to this effect. Waters of low
turbidity may coagulate poorly and
require excessive coagulant dos-
age. Particle size distribution
of the turbidity causing substanc-
es can affect coagulation. Wider
distributions of clay particle
sizes coagulate better than narrow
ranges. Organic material carried
by clay seemingly has little
effect on coagulant demand.
Temperature affects the coagula-
tion process by changing the visco-
sity of water and, to a lesser
extent, by affecting the rate of
the coagulation reactions. Very
low temperature waters may exhibit
lower optimum pH levels, with the
effect more pronounced as^goagu-
lant dosage is decreased.
Choice of coagulant and optional
coagulant aid is, of course, one
of the prime factors that influ-
ences coagulation. Alum is the
most commonly used coagulant; how-
ever, iron salts may work better
for treatment of soft colored
water8. The coagulant(s) for a
given system should only be chosen
after thorough analysis of the raw
water and jar testing.
FLOCCULATION
Solids that are coagulated and
precipitated in the coagulation/
rapid mix treatment stage are
still too finely divided for effec-
tive removal. The flocculation
process aids in the formation of
large settlable and filterable
solids by creating a suitable
111-14
-------
environment for agglomeration of
the small solids. In the floccula-
tor, very small (colloidal) solids
collide with each other and agglom-
erate into larger solids or floe.
The flocculation process is car-
ried out in a basin which provides
15 to 30 minutes detention time
while some type of mixer provides
slow, gentle stirring. Figure 15
depicts two common flocculator
types; other types include static
baffle, and diffused aeration
flocculators. Flocculation is
basically a controlled mixing
process and is therefore quite
dependent on control of velocity,
detention time and short
circuiting. Agitation in the
flocculator must be sufficiently
intense for solids contact and
compaction, but below the level at
which a substantial number of floe
would be broken down. Of course,
successful flocculation is also
very much influenced by raw water
characteristics and proper
application and control of
coagulant.
SEDIMENTATION
The sedimentation process sepa-
rates the solids containing floe
from the clear water by providing
a stilling basin with carefully
controlled fluid flow and a means
of settled solids removal. The
flocculated solids are heavier
than water, hence they sink to the
floor of the unit where they are
removed. Figure 16 illustrates
some typical clarifier configura-
tions used for sedimentation in
water treatment plants.
Clarifiers are usually designed on
the basis of surface loading (gpd/
sq.ft. or lpd/sq.m. surface area)
and detention time (hours). Rise
rate, in feet or meters per hour,
may be specified as an alter-
native to surface loading. Sur-
face loading (SL) is related to
rise rate (RR) as follows:
English Units:
RR(ft/m) ¦ SL (gpd/sq.ft.)
179.5
Metric Units:
RR(m/m) = SL (lpd/sq.m.)
1000
Typical water treatment clarifier
detention time is 2 to 4 hours
with an overflow rate of 350 to
550 gpd/sqI|t12(14,260 - 22,407
lpd/sq.m.) '
Clarifiers are also described by
the method used for settled solids
(sludge) removal. Scraper clari-
fiers use wiper blades that move
slowly along the floor, pushing
the sludge to an opening in the
center (circulator clarifiers) or
at one end (rectangular clari-
fiers) where it is pumped away by
solids handling pumps. Suction
lift clarifiers have hydraulic
vacuum heads which move slowly
over the clarifier floor, lifting
the solids out. Some clarifiers
have no scraping on vacuuming
equipment. Rather, they use
hopper bottoas; steeply sloped
floors formed into an inverted
cone or pyramid. Solids fall by
gravity to the removal pipe at the
bottom. This approach is more
often used in small clarifiers to
simplify operation and lower
C08 tS .
Upflow solids contact clarifiers
combine the mixing, coagulation,
flocculation and settling func-
tions into one compact unit
(Figure 17). By flowing the floc-
culated influent through the
settled solids layer, enhanced
solids removal is obtained at
higher flow rates. The process
works by matching the settling
111-15
-------
Influent
Woter level
Poddies
Control volvs
Effluent
MECHANICAL FLOCCULATION BASE
HORIZONTAL SHAFT-REEL TYPE
Flash mixing
basin
Motorized speed reducer
Flocculatlon
MECHANICAL FLOCCULATOR
VERTICAL SHAFT PADDLE TYPE
Figure 15. Flocculators
Sludge
CIRCULAR RIM-FEED, RIM TAKE-OFF CLARIFIER
CZflE
*Sludge
Sludge
hopper
-Drive sprocket |#va,
-Adjustable
Chrtn ft flight
cross collector
Flights
RECTANGULAR CLARIFIER WITH WAIN
AND FLIGHT COLLECTOR
Figure 16. Clarifiers
111-16
-------
velocity of the floe to the upward
velocity of the water, causing the
formation of a sludge "blanket"
which enhances solids capture. As
might be expected, operation of
solids contact clarifiers requires
good control of flow and coagula-
tion. Upflow clarifiers are wide-
ly used in water softening pro-
cesses and are generally applied
in larger water treatment plants.
The time required for suspended
solids to settle from the water
surface to the floor of the clari-
fier is largely a function of par-
ticle size and weight and the qui-
esence (stillness) of the liquid
mass. Theoretically, clarifier
size could be greatly reduced by
decreasing the distance of fall of
the solids particle. Also, it is
quite difficult to eliminate stray
currents and other hydraulic dis-
turbances in large tanks of water.
Tube and plate clarifiers (or
standard clarifiers to which tubes
and plates have been added) have
hundreds of small settling cells
in the clarifier liquid space,
greatly enhancing performance per
unit of surface area. Figure 18
depicts a tube clarifier frequent-
ly used in packaged water treat-
ment systems. Each tube functions
like a small clarifier, discharg-
ing settled solids downward and
clear water at the top. Tubes can
be retrofitted into existing poor-
ly performing clarifiers as well.
Other similar units may use hexa-
gonal or square tubes, or stacks
of shallow plates. Sedimentation
is not used in direct filtration
systems.
FILTRATION
Filters remove suspended solids by
three principal mechanisms (Figure
19).
• Surface filtration - large
solids settle out or are trap-
ped at the surface of the fil-
ter bed.
• Physical straining - smaller
solids cannot pass the gap
between filter particles and
are trapped.
• Adhesion - the smallest solids
that can readily pass through
the pores in the filter bed may
be attracted by weak forces
which cause them to adhere to
the surface of individual fil-
ter particles.
Depending on the type of filter
used (discussed below) and the
solids being filtered, solids are
entrapped on the surface of the
filter as well as in the body of
the bed. Filter types and designs
are quite numerous. However,
granular media and diatoaite
are the most common types used in
water treatment.
Granular Media Filters
As typically applied to potable
water treatment in the past, granu-
lar media filters are beds of
select sand 1-1/2 to 3 feet deep
through which the water is p^|sed
to physically remove solids.
In more recent years, there has
been a proliferation of filtration
devices and filter media as the
nature of the physical and chemi-
cal processes used in filtration
have become better understood.
The simplest filter has at least
three main components.
• A housing to hold the filter
bed and appurtenances.
• A filter bed, often consist-
ing of fine filter sand on a
gravel bed.
111-17
-------
Rotor impeller
Chemical—
-Secondary mixing
iand reaction zone
Draft tubes
Effluent-
Concentrator
Clear water
escape
Clarified
water
v. V V
^ - ( ^Primary mixing \
f f and^reaction zone ~
Discharge
p?2$32!E233!
SSZZESZ
Raw
water
Blow-off and drain
Figure 17. Clarifier/Flocculator
Bockwoih
Row wottr
Filter
Figure IB. Tube Clarifier
111-16
-------
solids
surface
filter bed-
trapped
solid
filter
media
adhering particle
filter
medii
a) Surface entrapment
b) Physical straining
c) Adhesion
Figure 19. Principal Mechanisms of Filtration
• Underdrains to collect and
carryoff filtered waters.
A filter may also be equipped with
backwashing equipment to allow for
cleaning of the sand bed by
reversing the flow through the
unit, dislodging the trapped
solids.
Three types of granular media
filters are in common use today:
• Slow sand filters
• Rapid sand filters
• Multimedia filters
Slow sand filters. These filters
are characterized by simple design
and operation, and relatively low
flow rates per unit of surface
area. They are normally not
equipped with backwashing equip-
ment; rather cleaning is accom-
plished by removing and replacing
the top several layers of sand
when plugged. Slow sand filters
can often be used on low turbidity
waters with no chemical addition
and flocculation. However, since
most of the solids are trapped
near the filter surface, this type
of filter has relatively low
solids capacity and is poorly
suited for filtration of very
turbid waters. They are
appropriate for use where it is
desirable to filter the water to
ensure its microbiological quality
even though the turbidity per se
is not a problem.
Rapid sand filters. Rapid sand
filters evolved from the need to
increase filtration capacity and
ease of cleaning in larger
installations. Rapid filters
operate at about 30 times the
filtration rate of slow sand
filters; hence they take up^ess
space for equivalent flows.
111-19
-------
However, rapid filters must be
equipped with back, washing equip-
ment as they require more frequettL
cleaning as well. Although their
operation is considerably more
complex than slow filters, rapid
filters can cope with a broader
range of water quality and are
best suited to filtration of
waters which require chemical
coagulation. Figure 20 is a typi-
cal rapid sand filter widely used
in the U.S. today.
Conventional rapid sand filters
depicted in Figure 21(a) often
feature a 30 to 40 inch (76 to 101
cm) bed of sand graded from fine
to coarse. Rapid filters are much
like slow filters in that most of
the solids are trapped at or near
the surface, limiting bed capacity
for solids. Several variations on
this approach, developed to
improve solids handling capacity
and/or filter cleaning, are shown
in Figures 21(b) and (c). Newer
developments in improved filter
media, discussed next, are rapidly
displacing conventional rapid sand
filtration for potable water fil-
tration.
Multiaedia Filters. Theoretical-
ly, the ideal filter would be even-
ly graded in particle size, coarse
to fine, as shown in Figure 22.
Such a filter would function as a
progressive sieve, trapping the
larger solids at the top and the
smallest deep within the bed.
This would maximize the solids
holding capacity of the bed, sub-
stantially reducing backwash needs
over filters that use only the top
portion of the bed.
To more closely approximate the
ideal filter, multi-media filters
have'been developed. Figures
21(d) and (e) illustrate two of
the most common variations: the
"dual media" and "mixed media" fil-
ters. Common to most of the varia-
tions on the conventional sand
filter is better utilization of
the filter bed by grading the
media from coarse at the top to
fine at the bottom.* This allows
for particles to penetrate into
the media body better distributing
the solids loading over the voluae
of filter media. Dual aedia fil-
ters typically use a layer of an-
thracite coal 18 inches (46 cm)
thick above an 8 to 10 inch (20 -
25 cm) sand layer. Mixed aedia
filters more closely approximate
the ideal coarse to fine grada-
tion, by using three layers of
media. The filter bed is 30 inches
(76 cm) deep, consisting of 18
inches (46 cm) of anthracite coal
on top, followed by 9 inches (23
cm) of silica sand with 3 inches
(8 cm) of garnet sand on the
bottom.
The media is graded in size so
that backwashing (reversing flow)
in the filter causes a fairly uni-
form gradation from coarse to fine
in the media. Mixed media filtra-
tion is a patented process, avail-
able from Neptune Micro Floe
Corporation, Corvallis, Oregon.
Claimed advantages are longer fil-
ter runs between cleaning (back-
washing) , higher solids handling
capability, and lower filtered
water turbidity. Figure 23 is a
cutaway drawing of mixed media
filter suitable for a small water
utility. Most new and retrofitted
water filtration plants in the
U.S. use multi media technology.
Granular media filters (rapid sand
and multimedia) are available as
either gravity filters
* However, the bottom of the fil
ter, including the underdrains
includes a layer of gravel.
111-20
-------
Rot* of flow ond
loss of hood gages
Filter bed
washwoter
troughs
Operating table
Operating
floor
Filter drain
Concrete
filter
tank
Filter to waste
Pressure lines
to hydraulic
valves from
operating tables
Wash line
Influent to filters
Pipe gallery floor
Effluent to clear well
Oroin
Wash troughs
Filter tank
Graded gravel
Perforated
laterals
Filter floor
Cast - iron
manifold
g
Figure 20. Typical Rapid Sand Filter
111-21
-------
Overflow trough
Effluent
Grid to
retain
sand
Fin*
Strainer
Influent
Effluent
Influent
Sand
Coarse
Spnd
Coarse
Coarse
Underdrain
chamber
Underdrain
chamber
Effluent
Influent
a) Conventional b) Upflow Filter c) Bi-Flow Flow
Filter
SINGLE MEDIA FILTERS
30-40
depth—¦

««

VMVMMWM

SxSlllea

-Coarse media
-Intermix zone
Finer media
Finest media
-Underdrain
chamber
Anthracite
Silica v:::
Sand: : ::
P.qrnet Sand
•—28"-48"
depth
d) Dual Media Filters
MULTI MEDIA FILTERS
e) Mixed-Media Filters
(Triple Media)
Figure 21. Filter Configurations
111-22
-------
CROSS - SECTION
THROUGH MIXED
MEDIA FILTER
UNIFORMLY GRADED
FROM COARSE TO
FINE FROM TOP
TO BOTTOM
t
z
H
o.
U1
a
o
z
m
<
UJ
CE
O
LlI
a
GRAIN SIZE
Figure 22. Ideal Filter
or as pressure filters. Gravi-
ty filters are generally open on
top (Figure 20) and rely on the
weight of water above the bed to
force the water through. As the
filter becomes plugged, the
height of water (head) above the
filter increases. Generally,
these filters are controlled by
the head of water. When it reach-
es a predetermined level, the fil-
ter is taken out of service and
cleaned by backwashing (reversing
flow). Gravity filters are almost
always used for turbidity removal
in drinking water plants. Pres-
sure filters such as the one
shown in Figure 24 use an enclos-
ed pressure tank, generally fabri-
cated from steel. Water is pump-
ed into the filter and forced
through the bed under pump pres-
sure. As the filter becomes clog-
ged, the pumping pressure rises
to a predetermined level, at which
time backwash cleaning is initi-
ated.
Pressure filters may be used for
iron and manganese removal from
well waters. Many states discour-
age or prohibit their use for tur-
bidity removal unless they are pre-
ceded by coagulation, flocculation
and sedimentation.
Rapid granular media filters
(rapid sand and multimedia) are
typically operated at flow rates
ranging from 2 to 8 gpm/sq. ft.
(815-326 lpm/sq.m.) of filter bed
surface area. Mixed media filters
tend to the upper end of this flow
range, depending on influent water
solids loading. Back washing may
consume up to 10 percent of the
filtered water supply, flowing at
rates of 10 to 20 gpm/sq.ft.
(407-815 lpm/sq.m.). To reduce
111-23
-------
Influent -bockwosh
collection header
To backwash
~ watte disposal
Influent valve
»C
Surface wash
Watte valve
n n k
Mixed media
n n n
Mixed medio
ce wash
Backwash valve
Filter tank
Effluent collection header
Effluent valve
Backwash
supply
Rote
control valve
To clearwell
Surface
wash supply
Figure 23. Mixed Media Filter
Courtesy: Neptune Microfloc Corp.
Influent
Influent-bockwosh
collection header
Filter tank-
Waste valve
=3-*
Surface wosh
valves
Mixed media
Mixed media
h n n n ri
Backwash
volve
Effluent
valve
Backwash
supply
Rate
control
valve
Surface
wash supply
To backwash
waste disposal
— Surface
wash
Effluent collection header
clearwell
Figure 24. Pressure Filter
Courtesy: Neptune Microfloc Corp.
111-24
-------
backwash water consumption and
improve filter cleaning, air may
also be injected into the filter
bed during backwash (air scrub-
bing) . Surface accumulation of
solids may be broken up and agitat-
ed by a rotary spray arm mounted
above the surface (rotary spray
washer). Slow sand filters do not
use backwashing for cleaning.
Vendors of gravity and pressure
filters are quite numerous and
some are listed in Table 7.
Diatomite Filters
Diatomaceous earth filters, wide-
ly used for filtering swimming
pool water, have been applied for
drinking water treatment as well.
In contrast with granular media
filters, diatomite filters use a
very thin layer of filter mater-
ial (1/8 to 1/4 inch) (3.2-6.4 mm)
which is coated out porous
"septum" (Figure 25). In use,
additional diatomaceous earth is
added to the influent water as
"body feed." When the filter
becomes plugged, it is backwashed
and agitated to cause the diatoma-
ceous earth to fall off the septum
and be flushed from the filter
tank. After fresh precoating, the
unit is returned to service.
Cited advantages of diatomite
filters include compact size,
simplicity of operation (coagula-
ting chemicals are not used) and
excellent turbidity removal.
Three major factors af|^ct diato-
mite filter operation:
• Type and concentration of diato-
mite feed
• The filtration rate
• The pressure drop across the
fiIter
Generally, filtration rates range
from 1 to 2 gpra/sq.ft. (40.7-81.4
lpm/sq.m.) of septum area. Body
feed and operating pressure (head)
are estimated from solids loading
and are a function of the type of
diatomite and filter selected. A
partial list of filter vendors is
given in Table 8.
Diatomite filters are most suited
for smaller water systems
filtering water of low turbidity
(less than 10TU)*. The principal
advantages of diatomite in this
application are low first cost and
compact size. They are also quite
widely used for emergency or
seasonal^yater treatment
systems. Because the precoat
and body coat will tend to slough
off when filter flow is stopped,
diatomite filters are operated on
continuous flow basis. Typically,
they are operated for a set period
of time, usually 24 hours,
discharging filtered water to
storage, before shutdown/cleaning.
The unit is precoated and
returned to continuous service
when stored water drops below the
required minimum levels.
Diatomite filters are available as
either pressure or vacuum filters,
depending on whether the pressure
pump is located upstream or down-
stream of the filters. Most diato-
mite filters are pressure units
similar to the one shown in Figure
26.
PACKAGED TREATMENT SYSTEMS
The preceding discussion dealt
with water treatment on a step by
* Although there is no agreement
on the upper limits of turbidi-
ty, most municipal experience
falls in this range.
111-25
-------
Table 7 (
Partial List of Gravity and Pressure Sand Filter Suppliers
Anthracite Filter Media Co,
90302
Calgon Corp.
Culligan Intl. Co.
Delaval Turbine Inc.
Dorr-Oliver, Inc.
Envirex Inc.
Waukesha, WI 53186
Filtration Equipment Corp.
General Filter Co.
Hungerford & Terry Inc.
08312
Hydro Clear Corp.
Infilco Degremont Inc.
Leopold Co.,
Midwest Marine Cont. Inc.
Neptune Microfloc Inc.
Corvallis, OR 97330
Peabody Welles, Inc.
Permutit Co., Inc.
NJ 07652
Roberts Filter Mfg. Co.
Tonka Equipment Co.
The Turbitrol Co.
Atlanta, GA 30355
Western Filter Co.
80216
734 E. Hyde Park Blvd., Inglewood , CA
Box 1346, Pittsburgh, PA 15230
One Culligan Pkwy, Northbrook, IL 60062
Box 251, Trenton, NJ 08602
77 Havemeyer Land, Stamford, CT 06904
A Rexnord Co., 1901 S. Prairie Ave.,
1425 Emerson St., Rochester, NY 14606
Arrasmith Trail, Box 350, Ames, IA 50010
226 Atlantic Ave., Box 45, Clayton, NJ
Box 2360, Newport Beach, CA 92660
Roger Executive Center, Box K-7, Richmond,
VA 23288
Division of Sybron Corp., 227 S. Division
St., Zelienople, PA 16063
149 Gregory St., Mount Prospect, IL 60056
Subsidiary of Neptune Intl., Box 612,
11765 Main St., Roscoe, IL 61073
A Zurn Co., E. 49 Midland Ave., Paramus,
6th & Columbia Ave., Darby, PA 19023
5115 Industrial St., Maple Plain, MN 55359
415 E. Paces Ferry Rd., Box 12047,
4545 E. 60th Ave., Box 16323, Denver, CO
111-26
-------
a) Precoating Filter
Direction of Flow
Precoat Liquid
Precoat of Filter
Aid Particles
b) Filtering Raw Water
Direction of Flow cii
OUTSIDE ^ 'c; O
Liquid to be Filtered £3
..A'
Filter Cake of Removed Solids
and Filter Aid Particles
INSIDE
Filtered Liquid
Precoat of Filter
Aid Particles
Septum
Figure 25. Diatomaceous Filter Septum
Table 8
Partial List of Diatomite Filter Vendors'
Bif-Unit of General Signal 1600 Division Rd., West Warwick, RI 02893
Delaval Turbine Inc.
General Filter Co.
Hydro Clear Corp.
Jones Chemicals Inc.
Box 251, Trenton, NJ 08602
Arrasmith Trail, Box 350, Ames, IA 50010
604 Moore Rd., Box 151, Avon Lake, OH
40012
100 Sunny Sol Blvd., Caledonia, NY 14423
McKesson Chemical Co. [D] Crocker Plaza, 1 Post St., San Francisco,
CA 94104
Western Filter Co.
4545 E. 60th Ave., Box 16323, Denver, CO
80216
111-27
-------
All*
¦ COMPREWOR
CONTROL
CABINET
AIR VENT
| POST I, TO
TREAT-1» VALVES
¦MENT II
Itoorbon |
|_eoUimn)|
CLEAR
WELL
•IOHT ,
GLASS
CLEAN ,
WATER c=~->
LET
DISTRI -
6UTION
SYSTEM
PRESSURE
LINE
CLEAN BACKWASH WATER,
CLEAN WATER
BACKWASH
.RECIRCULATION
INLET
DRAIN
DETENTION
TANK
RAW
WATEI
FILTER
PUMP
FROM
IrrrTni
HI3H PRESSURE
RAW
WATER
SUCTION
BODY
UOW PRESSURE SUCTION
FEED
SLURRY
TANK
777777777
77777777
Figure 26. Pressure Diatomite Filter
step basis. Traditionally, treat-
ment plants have been custom de-
signed, with each process consider-
ed as a separate step. Small
water utilities, however, can
select and purchase "packaged"
systems, premanufactured and part-
ly assembled before being shipped
to the site. Packaged plant
systems are usually constructed of
protected steel and plastic and
can be installed in simple prefa-
bricated buildings. They are
supplied complete with chemical
mixing and feeding equipment, and
controls, ready for installation.
Up to about 2 mgd (7570 cu.m./d)
treated flow, packaged systems can
offer substantial cost savings
over custom designed and construct-
ed plants. For example, a custom
designed 1 mgd (3185 cu.m./d)
plant which would have cost $1.1
million in 1978 could have been
installed for $500,000^i£ a pack-
aged system were used. ' Reduc-
ed operator needs would cut operat-
ing costs by a third, due to the
compact, easily maintained design
of the plants and their semi-auto-
matic control systems.
Figure 27 illustrates a typical
layout of a packaged complete
treatment system. This plant
includes chemical mixing and feed-
ing, coagulation, flocculation,
settling, and filtration, plus con-
trols, in a simple prefabricated
type building. A cost estimating
technique has been provided in
Section V for this type of system.
111-28
-------
Toi let
Ad
»ash water ore in
Chlorine
room
^Alum /—
feed VJ
^ssembly
' compartment
Compressed
• ir supply
assembly
Feed pumps
F lobula-
tion
compart mei
Filter pumps'
Chemical 6torage
Control panel
assembly
PLAN VIEW
Filtered water to
storage —
Package treat-
ment plant —p
Chemical
teed tank
r*' Concrete slab

Washwater sewer
ELEVATION VIEW
Figure 27. Packaged, Complete Treatment System
111-29
-------
DIRECT FILTRATION
The term "direct filtration" de-
scribes a turbidity removal pro-
cess, which may eliminate separate
flocculation and settling steps
and features coagulation immediate-
ly before, or in the feed water
side of the filter. It has receiv-
ed considerable interest, and wide-
spread appj^c^icjig ^ large water
utilities. ' ' ' Figure 28
compares direct filtration by
comparison to the conventional
process design. It is most suit-
able for surface waters of low
turbidity (less than 50 to 60 NTU)
caused by fjlj^ or other coagulat-
ed solids. ' A pilot study
is recommended before selecting
this process. It is important to
note that this process generally
requires close operator control.
Packaged direct filtration plants
are available; however, their manu-
facturers generally suggest that
small water utilities with limited
operator resources use packaged
complete treatment as it is less
sensitive to operator error or
neglect.
WASTE MANAGEMENT
Water treatment processes gener-
ate wastes in the form of dilute
sludges (from coagulation/floccula-
tion/sedimentation) and turbid
backwash waste water. These must
be disposed of in an environmental-
ly sound manner. Four options are
commonly used by small water utili-
ties in handling these wastes:
1. discharge to sewer
2. haul to landfill
3. lagooning
4. sand drying beds
Fortunately, water treatment plant
wastes are generally low in organ-
ic content and free of toxic sub-
stances and do not require the
specialized handling needed for
more toxic wastes.
Waste Characteristics
The characteristics of alum sludge
from package plants depend on the
type of plants and raw water char-
acteristics. Typically, a 500,000
gpd (1892 cu.m.d) plant produces
about 25,000 gallons per day (95
cu.m.) of dilute sludge (2000 to
5000 mg/1 of solids) and 1000 to
2500 gpd (3.8 - 9.5 cu.m./d) of
backwash waters containing 50 to
100 mg/1 of solids. ' '
Organic content is usually quite
low, approximately that of efflu-
ent from a secondary wastewater
treatment plant.
Sludge from alum treated waters
appear as gelatinous greyish white
slurries that are quite difficult
to dewater (separate solid from
the water). Larger plants employ
a variety of machinery to dewater
and concentrate sludge. Small
plants, because of economic and
O&M considerations, generally em-
ploy the simpler methods discussed
below.
Discharge to Sewer:
Discharging water treatment wastes
to the sewer of a local waste
treatment plant may solve the
waste disposal problem with little
impact on wastewater treatment
costs or effluent quality. In
fact, settling at the waste water
tre^gment plant might be improv-
ed. Sewer discharge might be
feasible if these conditions are
met:
• Local sewers are capable of
handling the sludge without
blockage or excess scour.
111-30
-------
©direct*
FILTRATION
WITH CONTACT
BASIN
©DIRECT*
FILTRATION
~
i
i
COAGULANT
CONTROL
CENTER
ILTER
AID
RAW -
WATERS
RAPID
MIX
COAGULATION
PRIMARY
COAGULANT
©CONVENTIONAL
FILTRATION
Q.
CONTACT TIME
TIME = I HOUR

FILTRATION
FLOC FORMATION,
PARTICLES
ADHERE TO EACH
OTHER 8 MEDIA
TURBIDITY
MONITORING
FLOCCULATION

SEDIMENTATION

•FLOC FORMATION
• ENLARGE FARTFCLES
W
SETTLING
PARTICLES
di
FILTRATION
RARTICLES
ADHERE
TO MEDIA
PRODUCED
WATER
» MAY ALSO REQUIRE A SEPARATE
FLOCCULATION STEP
FILTER
AID
-------
• The waste is amenable to the
wastewater plant's treatment
processes.
• The additional water will not
hydraulically overload the
wastewater plant.
• The waste does not significant-
ly affect wastewater effluent
quality.
If this option is used, the sludge
should be discharged slowly, over
an 18 to 24 hour period, to avoid
shock loading the wastewater treat-
ment plant. Use backflow preven-
tion valves, air gaps and other
appropriate means to protect the
water treatment plant from conta-
mination caused by sewage backup.
Haul to Landfill:
Localities with remote or nonexis-
tent sewerage facilities can dis-
pose of dilute water treatment
sludges by land disposal in sani-
tary landfills. Reference 15
presents a cost model for this
alternative based on tank truck
haulage with the utility owning
the truck. Hauling of backwash
waters should not be required.
Rather, this water should be held
in a small settling tank or pond
fitted with a skimmer. The clear
water is returned to the process
stream.
Lagooning:
Lagooning is the most popular
method o| handling coagulant
sludges. A large, relatively
shallow lagoon will reduce the
sludge volume by both evaporation
and seepage into the ground. In
addition, freezing of the pond's
contents (in colder climates) nay
aid in solids/water separation.*
The lagoons are usually designed
as unlined earthen ponds capable
of retaining 3 to 5 years of
sludge flow. Two parallel lagoons
are provided to allow time for
cleaning. (See Figure 31) A sur-
face skimmer, to facilitate with-
drawal of clear surface water, is
provided in each basin. Periodi-
cally, the plant operator pumps
the excess water off, either to
the plant headworks or directly
back to the source stream
(although this may require a dis-
charge permit).
Sand Drying Beds:
Warmer, drier climates may be able
to use sand drying beds. The
beds, widely used for dewatering
wastewater treatment sludge, are
commonly constructed of 6 to 9
inches (15-23 cm) of sand over-
lying 9 to 12 inches (23-30 cm) of
gravel used to cover drain pipes
which convey seepage from the
beds. Sand sizes ^ 0.4 to 0.5 mm
are commonly used. The drying
beds appear as shallow basins into
which 8 to 12 inches of sludge is
pumped at a time. After the
sludge dries, in 1 to 2 weeks, it
is scraped off using a front end
loader or similar equipment and
hauled to a landfill.
* If freezing is to be used for
dewatering, it must be carried
out on a batch basis as
unfrozen sludge mixed with
frozen sludge will negate the
process. Further, freezing must
be complete for an effective
process. As snowfall may
"insulate" the ponds contents
from freezing, provision for
snow removal may be needed if
this process is used.
111-32
-------
Sand drying beds require exten-
sive space and long dewatering
times and may perform poorly dur-
ing cold or wet weather. The
labor and equipment required to
remove the sludge are expensive as
well. Small water utilities
should throughly investigate the
alternatives discussed above
before choosing sand bed dewater-
ing.
111-33
-------
IV. DESIGNING TURBIDITY REMOVAL SYSTEMS
INTRODUCTION
Design of water treatment systems
entails several interrelated
steps, as illustrated by Figure
29. The design process begins
with complete characterization of
system needs and constraints.
Characterization data is used in
selecting process and equipment
for the treatment plant. The
level and type of treatment needed
largely determines equipment
selection. The decision to use
packaged versus custom designed
systems depends mainly on site
considerations, O&M resources, and
cost considerations.
Water treatment plants using chemi-
cal coagulation generate signifi-
cant quantities of waste which
must be disposed in an environmen-
tally sound manner. Fortunately,
water treatment plant wastes rare-
ly contain hazardous or toxic
substances. Small systems general-
ly produce relatively small quanti-
ties of wastes which can be safely
disposed by landfilling or lagoon-
ing. Discharge of liquid wastes
to a nearby wastewater treatment
plant may also be possible. Other
options include mechanical condens-
ing and disposal systems which
should be avoided if possible as
they are more complex, costly and
maintenance intensive.
This section of the text discuss-
es design of treatment systems and
equipment for turbidity removal.
Emphasis is placed on packaged sys-
tems as they are generally the
most economical and easy to oper-
ate for water utilities treating
less than 500,000 gpd. Because
packaged systems are pre-engineer-
ed, the discussion focuses on
selection of the proper plant
type, size and site requirements,
for new or upgraded turbidity
removal systems. At the conclu-
sion of the section, Table 10 pro-
vides an example of the decision
process that would be followed in
designing a small packaged treat-
ment system. Custom designed
water treatment systems require a
more extensive engineering effort
and should be designed by profes-
sional consulting engineers with
specific experience in their
design and construction.
CHARACTERIZATION
Developing a complete understand-
ing of the specific characteris-
tics of the application is the key
to subsequent decision making and
system design. Time and money
spent up front for this activity
can avert costly and time consum-
ing errors in design and operation
of the plant.
Water Quality Analysis
Water quality analyses coupled
with projection of current and
future quantity and quality needs
provides the primary basis for
design. Analyze representative
water samples to determine key
turbidity related parameters. For
example:
• Turbidity and Suspended Solids-
used in process and coagulant
selection.
• pH and alkalinity - key fac-
tors in coagulation chemistry
and control.
IV-1
-------
Characterization
Water Quality Analysis
- check existing
records
- jar testing
and pilot testing
Other Data
- current and
future needs
Process/Equipment Selection
Direct Filtration
- packaged systems
- slow sand filters
- diatomaceous earth
Complete Treatment
- packaged systems
- custorn designed
systems
Waste Management
• Lagooning
• Disposal to Wastewater
Treatment Plant
• Other
Figure 29. Design Process for Turbidity Control Systems
IV-2
-------
• Hardness and total dissolved
solids - also affect coagulant
chemistry.
• Sodium and chlorides - may
affect coagulant selection
because of consumer health
considerat ions.
• Iron and manganese - excessive
levels (over 0.3 mg/ for iron,
0.05 mg/1 for manganese) may
affect coagulation and may
require additional treatment
processes.
• Algae - excessive levels may
affect treatment process and
equipment selection and may
require pretreatment.
• Organic compounds - additional
treatment may be required for
some organics.
Collect sufficient water sample
data to characterize the full
range of water quality that may
occur. This is particularly impor-
tant with suface water supplies,
where key parameters can vary with
weather, seasonal changes, and
watershed development. Ground
water tends to change much more
slowly (in the absence of gross
pollution).
Before setting up a sampling pro-
gram, check all existing utility
and state records for the results
of previous analyses. Existing
water utilities may already have
adequate long-term data to provide
the background needed for treat-
ment design. Also, consult with
the suppliers of the treatment
systems that you are considering
to find out their data needs for
developing recommendations.
Jar Te-sting, described in Section
III, is used to determine
coagulant selection and dosage.
Jar tests are also quite useful in
identifying turbidity related
water quality parameters that may
interfere with the coagulation
process. Expert assistance for
jar testing may be available from
chemical suppliers, packaged
treatment system manufacturers or
local water quality laboratories.
Pilot Testing is used to simulate
the proposed treatment process on
a small, low cost scale. Where
water quality analysis or jar test-
ing indicates potential problems
with the proposed process, a pilot
test might be indicated. The pilot
plant would be set up to treat a
small (usually less than 10 gpm,
37.8 1/min) using a model of the
proposed process. Pilot testing
is generally not required for most
treatment system designs. How-
ever, if direct filtration is the
preferred process, it may be advis-
able to pilot test it if jar test
or water quality data indicate
potential problems.
Other Characterization Data
The selection of appropriate treat-
ment for new turbidity removal
systems also depends on these
factors:
• Plant size - hourly, daily,
weekly and annual flow,
seasonal variation expected;
future demand growth.
• O&M resources - availability
and funding to support full
time trained plant operators
and laboratory facilities.
• Site constraints - climate,
land area, waste disposal con-
straints .
Is the expected growth in future
water demand rapid, slow or un-
known? The answer to this ques-
tion determines how much capacity
should be installed initially and
IV-3
-------
the provisions needed for expan-
sion. How much can the system
afford for operating personnel and
supporting laboratory equipment?
If O&M resources are severely
limited, processes and equipment
that minimizes O&M needs should be
favored. Are there constraints
unique to the locality or plant
site that markedly impact design?
If so, these should be communicat-
ed to plant engineers and poten-
tial equipment suppliers early in
the design process.
PROCESS AND EQUIPMENT SELECTION
In selecting treatment processes
and equipment, be guided first and
foremost by the needs, con-
straints, and resources of your
particular utility and regulatory
agencies such as the State Health
Department that may have jurisdic-
tion. In most cases, one of the
early decisions will involve the
choice between "custom designed"
plants (individually designed and
conventionally constructed sys-
tems) versus "packaged" systems
(engineered and manufactured in a
factory and shipped to site by
truck or rail). In the latter
case, site work consists mainly of
the plumbing, electrical, housing,
road ways, and ancillary storage
vessels that support the packaged
plant. Because they can offer
substantial savings j^a^guisition
and operating costs, ' ' pack-
aged systems are frequently chosen
by small water utilities. Regard-
less of the chosen option, how-
ever, the services of an experienc-
ed Professional Engineer will be
needed for plant design, obtaining
state approvals, and overseeing
the installation of the plant.
Whether you elect to use a packag-
ed system or a custom designed
plant, you will have to select a
treatment process that is best
suited to your raw water quality
and operational resources.
Usually, you will be choosing
between direct filtration and
complete treatment options as
discussed below and illustrated by
Figure 30.
Direct Filtration For Low Turbidi-
ty Waters (<60 NTU)
In some cases, raw water quality
and operational resources permit
the use of less extensive treat-
ment schemes based on filtration.
Water of low turbidity(10 to 60
NTU) direct filtration may be a
viable option, using multi-media
filters and close operator
supervision (see Figure 30).
These systems may require
flocculation for satisfactory
performance. Some packaged direct
filtration systems can be
purchased with coagulation and
flocculation chambers built into
the filter body.
Very low turbidity water (<10 NTU)
that does not vary drastically in
quality over time and requires
only minimal coagulation might be
treated with simple, low-mainten-
ance slow sand filters, or compact
diatomaceous earth filters.
Consider using direct filtration
if the following conditions are
met:
Dual Media/Multi-media Sand
Filters:
• low turbidity waters (10 NTU-
-------
VERY UOW TURBIDITY
(less than 10 NTU)
(low color)
WATER
QUALITY
ANALYSIS
URBIDITY
GREATER
THAN 10 NTU

DIRECT

FILTRATION

/slow sond\

I filtration f

9
%

Criteria
•
very low (less

than 10 NTU)

turbidity and

little color?
•
reduce turbidity

to less than 1

NTU ?
•
little or no

chemical addition

needed ?
•
disinfect

after

filtration ?
h
i
PRESETTING
I
T
1
TURBIDITY

TURBIDITYl
LESS

GREATER
THAN

than
60 NTU

60 NTU

OIRECT
COAGULATION
AND FILTRATION
Criteria
• moderate (less
than 50 NTU)
turbidity and
low color ?
f, adequate
supervision
available ?
• raw water
quality stable ?
• reduce turbidity
to less than I
NTU ?
PACKAGED
COMPLETE
TREATMENT
Criteria
• raw water
turbidity under
400 NTU ?
• color removable
by chemical
coagulation ?
• raw water
quality
variable ?
• minimal
operator
supervision
available ?
Figure 30. Treatment Process Selection
IV-5
-------
Slow Sand/Diatomaceous Earth
Filters:
• very low turbidity waters
(<10 NTU).
• low variability in raw water
quality
vided. The system should be
capable of controlling coagu-
lant dosage and pH adjustment
automatically with provision
for manual override.
• Provision for surface wash or
air scour cleaning is needed.
• required coagulant dosage is
minimal
• pilot study indicates that
direct filtration is feasible
and safe
DO NOT SELECT DIRECT FILTRATION OF
ANY TYPE UNLESS IT CAN BE CLOSELY
SUPERVISED. PROVIDE CONTINUOUS ON-
LINE TURBIDITY MONITORING OF RAW
AND FINISHED WATER QUALITY AND
AUTOMATIC CHEMICAL DOSAGE CONTROL.
If these conditions cannot be met,
use a complete treatment system.
Complete treatment is more forgiv-
ing of operator error and/or
neglect of coagulant control and
can tolerate greater variation in
raw water quality. Also, pilot
study is generally not required
for complete treatment system
application.
Specifications for Treatment
Systems Using Gravity Filters:
• A detailed O&M manual and on-
site startup supervision and
operator training for at least
2 days should be provided with
the equipment.
• Maximum flow rates (per manu-
facturers specifications and
state standards) as follows:
Dual
Media
3
Media
4
Media
Maximum*
Flow Rate
gpm/sq.ft. 4 5 5
(lpm/sq.m.) (163) (204) (204)
Backwash**
Rate
gpm/sq.ft.
(lpm/sq.m.)
10
(407)
17
(693)
19
(774)
Backwash
Volume
gal/sq.ft.
(1/8q,m. @
70 F)
100 100
(4074) (4074)
100
(4074)
Use of packaged dual media or
mixed media filtration systems is
recommended for small water
systems using direct filtration
systems. Specifications for
packaged gravity filters should
include the following items (plus
those for packaged complete
treatment that are applicable):
• There should be at least 5
years in service experience
with the specified plant.
• A monitoring/control system for
influent and effluent turbidi-
ty, flow and pH should be pro-
* Some state regulations allow
only a 2gpm/sq.ft. (81 lpm/sq.
m.) rate.
** Complete backwash specifica-
tions include cycle time, flow
rate and total water consump-
consumption per backwash cycle.
Air scouring is recommended for
systems using in-line coagula-
tion. Rotary surface washing
should be provided on all
filters.
IV-6
-------
Slow Sand Filter Specifications
Slow sand filters may be consider-
ed for use for water of less than
10 NTU turbidity, and requiring
only minimal chemical treatment.
Suggested specifications for slow
sandj|ilters include the follow-
ing:
Surface
Loading
Bed Depth*
Effective
Size of Sand
Uniformity
Coefficient
o f Sand
70-140 gpd/sq.ft.
(2850-57001pd/sq.m.)
24-42 inches
(61-106 cm)
0.25-0.35 mm
2-3
Slow sand filters are cleaned by
scraping off several inches of
surface sand after head loss has
reached about 4 feet (1.2 m).
Depending on cost and 0&M consider-
ations, the removed sand could be
cleaned and replaced or disposed
to landfill and replaced with
fresh sand. The length of run
between cleanings will probabjy
range between 20 and 60 days.
Diatomaceous Earth Filter Specifi-
cations
Diatomaceous earth filters merit
close consideration for treatment
of very low turbidity waters or
for low cost upgrading of existing
treatment systems (as an add-on
final filter). Diatomite systems
are available from a number of
Sand depth up to 42 inches (106
cm) which is reduced to a
minimum of 24 inches (61 cm) by
periodic scraping for cleaning
before fresh sand is added.
vendors as packaged systems (see
Table 8). Suggested specifica-
tions for diatomite fi^e^|
include the following: '
Surface
Loading
Precoat
Thickness
Body Feed
Concen.
1 to 2 gpm/sq.ft.
40.7-81.4 lpm/sq.m.
1/16-1/8 inches
(1.6-3.2 mm)
20 mg/1 of
Diatomite
Maximum Cake 1/2 inches
Thickness (12.7 mm)
Minimum Spac- 1"
ing Between (25.3 mm)
Filter Septums
Available commercial diatomite fil-
ters use either manual or combin-
ations of mechanical, air, and/or
hydraulic cleaning. See Reference
20 and 21 for detailed suggested
specifications for municipal diato-
mite filter installations.
Packaged Complete Treatment
As the name implies, complete
treatment involves the use of the
full range of processes: rapid
mixing, chemical coagulation, floc-
culation, sedimentation, and
filtration. Packaged complete
treatment equipment is generally
recommended for these conditions:
• For Turbidity Levels Up to 400
NTU - packaged complete treat-
ment plants can handle turbidi-
ties from 10 to 400 NTU.
• Where Minimal Operator Super-
vision is Available - the
plants are designed to operate
semi-automatically with oper-
operator supervision limited to
routine and repair maintenance.
• Where Raw Water Quality is
Variable - complete treatment
IV-7
-------
systems can tolerate a wider
range of turbidity and still
produce water that meets NIPDWR
standards. The plants are less
sensitive to water quality
variation than direct or in-
line filtration.
• Where Color Removal is Required
- A more controlled coagula-
tion/ flocculation/sedimentat ion
process is required for effec-
tive color removal in most
cases. Complete treatment is
generally used for color
removal.
Manufacturers of packaged com-
plete treatment systems normally
provide suggested plant layout
drawings, including specifications
for building size and special
features needed to house the
plant. These must be modified as
needed to fit the requirements of
your particular application.
NOTE: THE SYSTEM MANUFACTURER
MUST BE GIVEN ADEQUATE WATER
QUALITY DATA TO SIZE AND DESIGN
THE UNIT PROCESSES. Jar tests are
recommended before selecting a
plant design.
Specifications for packaged com-
plete treatment should include the
following items (Table 9 summar-
izes some typical design paramet-
ers for both packaged and custom
designed complete treatment
systems):
• A manitoring/contro1 system for
influent and effluent turbidi-
ty. The system should be capa-
capable of reliably controlling
coagulant dosage and pH adjust-
adjustment automatically with
provision for manual override.
• Filter backwashing should be
automatically initiated, with
provision for manual override
by the plant operator. Back-
wash rate, provided by the manu-
facturer, should not exceed 15
to 22 gpm/ sq.ft. of filter
area (611-896 lpm/sq.m.) with
a total water consumption of
100 to 150 galIons/sq . ft. per
backwash cycle. The clear
water (backwash water) storage
tank should be separated from
other parts of the plant either
as a separate tank or at mini-
mum, by a double bulkhead with
a cavity drain. It should be
sized to provide for at least 2
consecutive backwash cycles (or
backwash water can be drawn dir-
ectly from the finished water
reservoir). Filters applied to
high turbidity waters (over 200
NTU) should be provided with
air scour and surface rotary
spray washers.
• The manufacturer or design
engineer should provide a
detailed O&M manual and onsite
startup and operator training
to ensure that the plant is
operated properly.
• The manufacturer should provide
a listing of recommended spare
parts for all system compon-
ents. It is recommended that
these be purchased and stocked
at the time the plant is pur-
chased .
• The manufacturer should be able
to provide or arrange for the
provision of factory service on
the plant and its components.
This is particularly important
in the case of plant components
that require specialized O&M
skills, such as monitors and
controls, and chemical metering
pumps. Do not purchase equip-
ment froa a manufacturer that
cannot provide service.
IV-8
-------
Table 9
Summary of Complete Treatment Design Data For Packaged and Custom Designed Systems
Complete Treatment Packaged Systems
21,22,23
Coagulation/Rapid
Mixing
Flocculation
Sedimentation
Complete & homogeneous rapid
mixing 10 to 30 seconds detention
Up to 20 minutes
Tube or plate settlers
235 gpd/sq.ft. (9574 lpd/sq.m.)
maximum surface loading rate
Custom Designed Systems
Same
11,12
20 to 60 minutes detention
0.1 to 3 fps (3-91 cm/sec)
Paddle area 10 to 25 percent
of tank section area
Surface loading rate - for alum
sludge 360 to 547 gpd/sq.ft.
(14,667-22,285 lpd/sq.m.)
Detention 2 to 4 hours
Filtration
(maximum rates)*
Mixed Media:
Dual Media:
Rapid Sand:
Backwashing:
Chemical Feed/
Storage
5gpm/sq.ft. (204 lpm/sq.m.)
4 gpm/sq.ft. (163 lpm/sq.m.)
Not Recommended
22 gpm/sq.ft. (896 lpm/sq.m.)
Dependent on chemical chosen,
raw water characteristics,
storage needs of specific system.
5 gpm/sq.ft. (204 lpm/sq.m.)
4 gpm/sq.ft. (163 lpm/sq.m.)
2 gpm/sq.ft. (81.5 lpm/sq.m.)
20 gpm/sq.ft. (815 lpm/sq.m.)
Dependent on chemical chosen
raw water characteristics,
storage needs of specific system.
Some state regulations specify design maximum filtration rates not to exceed 2 gpm/sq.ft,
(81.51 pm/sq.m.)
-------
The manufacturer should have at
least 5 years of in service
experience with the treatment
plant,
Dual or mixed media filter beds
as follows: '
Dual Mixed*
Media Media
6" anthracite 18"anthracite
18" silica sand 9"silica sand
8"high den-
sity sand
Maximum filter flow rates (per
manufacturers specification and
state standards), not to exceed
4 gpm/sq.ft. for dual media and
5 gpm/sq.ft. for mixed media.
• Chemical feed and mixing equip-
ment sized at two times maximum
coagulant flow, capable of mix-
ing and storing a one day sup-
ply of coagulant(s)
• Rapid chemical mixing should be
provided and the floccuation
compartment should have at
least 20 minutes detention with
controlled mechanical stirring.
• Settling compartments should
include tube or plate settlers.
Loading rate should not exceed
235 gpd/sq.^2^(9574 lpd/sq.m.)
of face area. Flocculated
water should be evenly distri-
buted across the face of the
tube/plate assembly.
Figure 27, shown on page 111-29 is
a typical packaged treatment plant
used to treat flows up to 100 gpm
(144,000 gpd).
* Mixed media may be of either 3
or 4 layer type. For larger
filters use two layers of differ-
ently sized anthracite.
MONITORING AND CONTROL
Monitoring and control equipment
for packaged or custom designed
systems should include the follow-
ing:
• A main control panel with
switching and indicator lights
for all pumps, motors and
electrical controls.
• Automatic settled sludge pump-
ing, with timers for setting
cycle frequency and length,
plus manual over-ride.
• Automatic backwashing of fil-
ters, initiated by filter head
loss monitors with a manual
override. Backwashing should
be controlled by a programmable
monitor controller which allows
the operator to vary cycle
times for each phase of the
backwashing operation.
• Automatic continuous monitoring
of raw and finished water turbi~
dity with warning lights and/or
alarms to alert the operator
when influent turbidity varies
by more than 20 percent or when
treated water turbidity exceeds
the 1 NTU standard.
Automated chemical feed equipment
which is controlled by turbidity
monitors is now available from
some equipment vendors. As of
1981, it was still relatively
unproven in long term field ser-
vice. However, the status and
availability of this equipment
should be checked on when the
system is being designed as it
could be of great use to the
operators by reducing the need for
continuous and close supervision
of chemical feeding.
IV-10
-------
WASTE DISPOSAL
CORROSION PREVENTION
Four alternate means of waste dis-
posal were discussed beginning on
page 111-30. Of these, discharge
to local sewers and lagooning are
by far the most commonly used by
small water utilities. This
section will focus on lagooning.
Figure 31 depicts a typical site
plan for a 250,000 gpd packaged
complete treatment system with
waste lagoons. Filter backwash
waters are recycled to the raw
water pre-settling and holding
pond. Sludge from alum coagula-
tion is stored in each of two
sludge lagoons in turn, providing
a total of 4 years storage of up
to 600 gpd of alum sludge (volume
after clear water skimming).
Periodically, clear water is
skimmed from the top of the pond
using a skimmer arrangement such
as the one shown in Figure 31.
The clear water stream is returned
to the presettling pond or back to
the stream. The lagoons are
designed to fill to a 5 foot
maximum sludge depth, with an
additional 2 feet of freeboard.
Dirt needed to construct the 3:1
sloped walls is obtained by
excavation of the lagoon bottom.
Operation of the lagoon system
alternates between the two basins.
After the first basin has reached
capacity, the waste flow is divert-
ed to the second basin. The first
is allowed to stand for several
seasons, or until the contents
have dried suffiently to be remov-
ed by earth moving equipment and
trucked to a landfill for final
disposal. After cleaning, it is
again available for service at
such time as the second basin re-
quires cleaning.
The combination of water plus cor-
rosive coagulating chemicals
results in a high potential for
corrosion of metallic system com-
ponents. Where packaged treat-
ment systems are housed in weather
tight buildings, care must be
taken to prevent buildup of a
moist and corrosive internal atmos-
phere which can damage equipment
not directly in contact with water
or chemicals (such as electrical
controls, motor windings and
instruments). Corrosion preven-
tion specifications should include
the following:
• All painted surfaces which con-
tact the raw or treated water
should be coated only with AWWA
and FDA approved coatings for
potable water service. Use
high strength PVC or other
plastic piping, containers, and
fittings where practicable to
minimize corrosion.
• Chemical feed lines should be
as short and straight as
possible. Provide for easy
line cleaning.
• Use only chemical mixing,
storage and feeding equipment
suitable for chemical service.
It should be constructed of
polyethylene, stainless steel
and other non-corroding
materials.
• Electrical controls should be
installed in air tight housings
with internal humidity control
as needed in moist climates.
• Provide an indoor humidistat
controller with an exhaust fan
to automatically vent excess
moisture outside. In very damp
climates, consider installation
of a dehumidifier as well.
IV-11
-------
'RIVER sz r
Intake
Preseltling pond
(5 days)
67,000 ft3
Backwash
Clean
water
storage
Treatment plant
59,000 fts
59,000 ft'
Skimmer
Waste
lagoons
Adiustmtnt wlr*
SKIMMER DETAIL
Figure 31. Site Plan of 250,000 gpd Packaged Complete Treatment Plant
With Waste Lagoons.
1V-12
-------
OTHER DESIGN CONSIDERATIONS
These considerations should also
be looked at when designing a
small complete treatment or direct
filtration plant:
• The plant layout should allow
for the possibility of expan-
expansion or addition of other
treatment processes.
• Design the plant for intermit-
tent operation, to allow time
for routine and repair servic-
ing, or provide duplicate pro-
cess units (e.g., parallel
package units).
• Provide a presettling pond of
2-5 days detention time if raw
water quality is highly vari-
variable. This will simplify
operation and reduce chemical
costs • Before using a holding
pond for raw water, make sure
that algae or other aquatic
growths will not create water
quality or operational prob-
lems .
• Provide for rapid flushing and
disposal of chemical spills
inside the treatment building.
The floor should be equipped
with floor drains connected to
a holding tank and a sewer.
Provide an emergency shower and
eyewash fountain if concentrat-
concentrated chemicals are
used.
• Continuous influent/effluent
turbidity monitoring is recom-
mended. Where coagulation and
pH control are required, this
unit can be used to control
chemical addition, reducing the
direct supervision time requir-
ed of the operator.
• Provide adequate equipment
redundancy to assure uninter-
rupted treated water flow.
Larger plants should employ
parallel treatment units or
provide 3 to 5 days clean water
storage.
• Provide adequate climb proof
fencing, lighting and entry
control in and around the
plant.
• All control switches and valves
should be located so that they
are protected from wetting and
can be reached by an operator
standing on the plant floor.
IV-13
-------
TABLE 10
SYSTEM DESIGN APPROACH FOR SMALL WATER SYSTEMS
STEP lr OBTAIN ALL REQUIRED BACKGROUND DATA
A. Water quality data:
1. Review all existing records.
(a) Existing water utility files.
(b) EPA/State/local regulatory agency files.
(c) Records of other local utilities that use the
same raw water source.
(d) (ground water supply) Information from local well
drilling companies.
2. Perform all other required analyses.
B. Site data:
1. Soils, topography, ground water and percolation data.
2. Location and boundaries of any nearby floodplains.
3. Access to supporting utilities such as gas, electric,
roads, Landfills.
STEP 2: PRELIMINARY STUDIES
A. Identify and contact 3 or more suppliers of packaged water
treatment systems:
1. Provide each supplier with a summary of existing water
quality conditions and the expected range of the data.
(a) Water quality data.
(b) Water source hydrology.
2. Provide each supplier with a summary of pertinent site
conditions.
(a) Climate.
(b) Any special soil conditions that impact on founda-
tion design.
(continued)
IV-14
-------
TABLE 10
(continued)
(c) Any constraints on the availability of supporting
utilites.
(d) Special conditions imposed on plant operations by
adjoining land use (ie. noise, dust, traffic).
3. Provide any additional data requested by suppliers.
B. (Optional) Coagulation testing:
1. If raw water conditions are unusual, or if system manu-
facturers recommend it, conduct jar test to determine
types and quantities of coagulating chemical(s) needed.
(a) Determine if jar testing can be carried out by
equipment or coagulating chemical suppliers.
(b) Contact state or local regulatory officials for the
names of qualified local labs (including local
college labs).
(c) Determine the price and local availability of the
common coagulating chemicals (ie. alum, polymers)
and conduct jar tests as needed to determine the
dosages and combinations of coagulants to be used.
(Note: Local chemical suppliers are often excellent
sources of information on the best chemicals and
combinations available.)
STEP 3: PROCESS AND EQUIPMENT SELECTION
A. Review water quality and hydrologic data and categorize the
water supply:
1. Average turbidity (up to 200 NTU), no unusual conditions.
2. Low turbidity (up to 60 NTU), no unusual conditions.
3. Very low turbidity (up to 10 NTU), no unusual conditions.
4. Unusual or highly variable water quality.
B. For average turbidity waters:
1. Evaluate the packaged complete treatment systems offered
by at least 3 manufacturers.
(continued)
IV-15
-------
TABLE 10
(continued)
(a) Provide each with the data obtained in Steps 1 and
2 and any additional data or water samples request-
ed by them.
(b) Obtain a listing from each of water treatment plants
using their equipment and identify those plants in your
locality that are treating similar quality waters.
(c) Contact a represeutative sampling of the plants for
performance and O&M data:
(1) Ability of plant to consistently produce
waters of acceptable quality.
(2) Required levels of operator supervision.
(3) Any special maintenance problems and weak
or trouble prone components.
(d) Visit 1-2 plants from each suppliers list and
meet with the operational personnel directly
responsible for running the plant to determine
their operation and maintenance experience.
(e) Request a system proposal from those manufac-
turers whose plants are performing satis-
factorily in the field. The system proposal
shoufd include:
(1) Details of the process flow schematic,
layout and site requirements for the
model of plant proposed.
(2) Description of the design basis of the
major plant elements:
- chemical mixing and feeding
- coagulation/rapid mixing
- design of settler and loading rates
- provisions for desludging and cleaning
settler
- design of filter and loading rates
- filter backwash system layout, controls,
wash water flow rates, projected wash
water consumption per cycle
- controls and instrumentation normally
provided with the plant and recommended
options
- recommended operator supervision and pre-
ventive maintenance.
- recommended spare parts.
- availability and description of local and/
or factory service.
(continued)
IV-16
-------
TABLE 10
(continued)
(3) Recommended supporting facilities
and instrumentation.
(4) Budget price and normal delivery times
from receipt of written order.
C. For low turbidity waters:
1. Evaluate packaged direct filtration alternatives and
compare to an evaluation of packaged complete treatment
performed as per B above (Note: The complete treatment
system supplier can often provide an alternative
recommendation and proposal for direct filtration).
2. Conduct the evaluation for at least 3 suppliers of di-
rect filtration equipment as outlined in B above (Note:
Delete those items related to the settler as direct fil-
tration does not utilize a separate settling unit).
D. For very low turbidity waters:
1. In addition to packaged direct filtration alternatives,
evaluate the following:
(a) Slow sand filtration.
(b) Diatomaceous earth filtration (Note: Diatomaceous
earth filter systems are often supplied in the form
of packaged direct filtration systems, and can be
evaluated using the same approach).
2. Slow Sand Filtration:
(a) All slow sand filtration systems are custom de-
signed. The design consultant should prepare a
preliminary design and cost evaluation tailored
to the specific requirements of the project.
3. Diatomaceous Earth Filtration:
(a) The evaluation should include close review of the
system's consumption of diatomaceous earth and the
disposal requirements and cost for handling spent
earth.
(b) Availability and long term reliability and price of
diatomaceous earth supplies should be checked care-
fully before selecting this alternative.
(continued)
IV-17
-------
TABLE 10
(continued)
E. Unusual or variable water quality:
1. This situation will require the services of a design
consultant who is expert in the design of water treat-
ment processes and plants. Although the final solution
may use packaged components, the overall process and
plant design may require additional specialized water
quality analysis or pilot study, as well as custom de-
sign of critical plant elements.
STEP 4: FINAL DESIGN
A. After selection of the preferred alternative, the design
consultant proceeds with the final project design and the
preparation of detailed drawings and specifications. This
includes sitework, design and specification of supporting
facilities such as raw water storage and intake headworks,
utility hookups, roadways and buildings, chemical storage,
clear water storage and pumping, disinfection, etc.
B. The detailed final plans and specifications must be reviewed
and approved by State regulatory authorities prior to bid-
ding, contractor selection, and construction.
IV-18
-------
V. COST ESTIMATING PROCEDURES AND FUNDING SOURCES
This section provides a summary of
the kinds of costs that are like-
ly to be encountered in any treat-
ment facility construction project
and outlines a procedure to esti-
mate costs associated with treat-
ment for turbidity removal. It
also summarizes some estimated
construction and operating costs
which have been made for the fol-
lowing treatment alternatives and
provides an overview of potential
funding sources for small water
utilities.
•Package Gravity Filters
•Package Pressure Diatomite
Filters
•Package Complete Treatment
Plants
•Sludge Disposal Lagoons
Additional cost information, on
actual operating plants, is given
in Section VII. Table 20, at the
end of the cost section, provides
an example of cost analysis using
the cost data presented in this
chapter.
Costs depend largely on site speci-
fic conditions, some of which may
change over time. The cost esti-
mates in this report were based on
assumptions made when the cost
curves were developed (1976-78).
In this regard, other projects are
currently in progress to refine
and improve the accuracy of cost
estimating procedures. As these
projects are completed they should
be consulted for more accurate
cost estimation procedures.
The total cost estimate for a
water treatment facility is
generally the sum of the costs
associated with two major categor-
ies: (1) Construction Costs, and
(2) Operation and Maintenance
Costs. Each of these major cost
categories is composed of indivi-
dual costs for a number of compo-
nents. To arrive at a total cost
estimate for a given facility, the
component costs are evaluated,
adjusted as necessary for site
specific considerations and infla-
tion, then summed. Costs can be
expressed many ways but annual
cost, and cost per thousand gal-
lons treated are two of the most
common. The latter can be used
directly to estimate the effect
the project will have on the indi-
vidual consumer's water bill. How-
ever, cost curves are generally
most useful for comparing relative
costs of the treatment alterna-
tives and for approximating the
general cost level to be expected
for a proposed treatment system.
CONSTRUCTION COSTS
Introduction
Whenever treatment costs are deter-
mined, whether from a published
report or a vendor's estimate, it
is extremely important to esta-
blish exactly what components and
processes the cost estimate includ-
es. Different cost estimates
based on different components
(such as housing) have in the past
resulted in many misunderstand-
ings. In addition, if the costs
are taken from a report, it is im-
portant to be sure they apply to
the size category of your system.
Once this has been ensured, cost
comparisons between alternatives
can be made using the process out-
lined in the introduction above.
To illustrate this procedure, the
V-l
-------
cost information developed by the
EPA Municipal Environmental Resea-
rch Laboratory (presented in a 4-
volume report titled: Estima-
ting Water Treatment Costs, EPA-
600/2-79-162) can be used.
This report presents cost curves
for 99 unit processes useful for
removing contaminants covered by
the NIPDWR.
The construction cost curves for
Reference 15 were developed by
using equipment cost data supplied
by manufacturers, cost data from
actual plant construction, publish-
ed data, and estimating techni-
ques from Richardson Engineering
Services Process Plant Construc-
tion Estimating Standards, Mean's
Building Construction Cost Data,
and the Dodge Guide for Estimating
Public Works Construction Costs.
The construction cost curves were
then checked and verified by an
engineering consulting firm.
Adjustment of the cost curves may
be necessary due to site-specific
considerations such as geographi-
cal or local conditions, stand-by
power requirements, and increases
in the construction cost index as
a result of inflation. The con-
struction cost curves are particu-
larly useful for comparing rela-
tive costs of the treatment alter-
natives and for evaluating the
general cost level to be expected
for a proposed treatment system.
Reference 15 Cost curves were all
based on October 1978 dollars.
The costs contained in these
curves can be updated by using the
Engineering News Record(ENR),
Construction Cost Indexes (CCI),
or Building Cost Index (BCI).
Both indices utilize a single
ratio to update costs. Note that
these indices average cost figures
from 20 cities—there is wide
variation among individual cities
and regions of the U.S. For
example, the August 1981 CCI
varied from a low of 274 to a high
of 360 among the 20 cities, about
a 31 percent difference. As a
result, updated cost figures using
this adjustment may tend to over
or underestimate costs depending
on the locality of interest. More
sophisticated cost updating
techniques are also available and
are described in Reference 15.
The following formula applies the
ENR CCI (base year 1967 = 100).
To update the October 1978
construction costs simply multiply
them by the current index and
divide by the October 1978 index:
Cost from curve X Current ENR CCI
265.38*
As of June, 1982, the ENR CCI
stood at 359.92. Thus, to update
the Reference 15 cost estimates to
this date, you would multiply them
by 359.92/265.38 or 1.33. For
more precise adjustment, use the
current and October 1978 CCIs for
the city/region that most closely
approximates your own.
The construction costs cited in
this document from Reference 15
are developed from 8 principal
components:
Excavation and Site Work.
This category includes work
related only to the applicable
process and does not include any
general site work such as
sidewalks, roads, driveways, or
landscaping.
Manufactured Equipment. This
category includes estimated pur-
chase costs of pumps, drives,
* October 1978 ENR CCI was
265.38 for 20 city average.
V-2
-------
process equipment, specific pur-
pose controls, and other items
that are factory made and sold
with equipment.
Concrete. This category
includes the delivered cost of
ready-mix concrete and concrete-
forming materials.
Steel. This category includes
reinforcing steel for concrete
and miscellaneous steel not
included within the manufactured
equipment category.
Labor. The labor associated
with installing manufactured
equipment, and piping and
valves, constructing concrete
forms, and placing concrete and
reinforcing steel are included
in this category.
Pipe and Valves. Cast iron
pipe, steel pipe, valves, and
fittings have been combined into
a single category. The purchase
price of pipe, valves, fittings,
and associated support devices
are included within this cate-
gory.
Electrical Equipment and Instru-
mentation. The cost of process
electrical equipment, wiring,
and general instrumentation
associated with the process
equipment is included in this
category.
Housing. In lieu of segregat-
ing building costs into several
components, this category repre-
sents all material and labor
costs associated with the build-
ing, including heating, ventilat-
ing, air conditioning, lighting,
normal convenience outlets, and
the slab and foundation.
The total for construction cost
using these cost components
includes the costs of materials
and subcontractors overhead and
profit, to which is added 15
percent for miscellaneous items
and contingencies.
The construction cost curves do
not include the following items:
Special Sitework
General Contractor Overhead and
Profit
Engineering
Interest
Land
Legal, Fiscal, Administrative
Services
These are not directly applicable
to the costs for specific process-
es. Rather, they should be added
in after process costs have been
estimated. Typically, these will
average 30 to 35% of the total
construction cost.
Package Gravity Filters
The configuration cost estimated
in Reference 15 could be used for
either direct or inline filtration
(p. 111-29). Construction cost
estimates assume that the package
gravity filtration plant is preced-
ed by a one hour detention basin.
Flow capacity assumed is 80* to
1400 gpm (5-88 1/s) at filtration
rates of 2 and 5 gpm/sq.ft. (81.5-
203.7 1pm/ sq.m.) of filter sur-
face area. Table 11 summarizes
the design assumptions used to
make the cost estimates.
* At flows below 80 gpm (5 1/s),
use a packaged complete treat-
ment plant.
V-3
-------
Table 11
Package Gravity Filter Plants Design Concept
Plant Capacity (gpm) Number
2 gpm/sq.ft. 5 gpm/sq.ft. of Units
80 200 2
140 350 2
225 560 2
280 700 2
560 1,400 3
NOTE: 1 gpm = 0.061 1/s
1 gpd = 0.003785 cum/d
1 ft = 30.48 cm
1 sq.ft. = 0.0429 sq. m.
Filter Area
(sq.ft.)
Diameter
(ft.)
Total Filter
Area (sq.ft.)
Housing
Area (sq.ft.)
20
5
40
1,500
38
7
76
1,800
50
8
100
1,800
79
10
158
1,800
113
12
339
3,600
-------
The equipment cost estimates of
Reference 15 include the following
items:
• shop fabricated, open type,
cylindrical steel tanks sized to
permit over the road shipment.
• mixed granular filter media
• piping, valves and controls
• backwash and surface wash system
• chemical feed system (alum, soda
ash, polymer, chlorine)
• raw water pumps
• backwash water storage
• building
• other items needed for a com-
plete and operable installation
Cost curves are presented in
Figure 32 for the two flow rates.
It is recommended that you select
the lower flow rate if you want to
maximize time between filter back-
washing. Using the higher rate,
where allowed, will reduce the
size and capital cost of the
plant. Table 12 gives the cost
breakdown for 80 to 560 gpm plants
(5-35 1/s).
Package Pressure Diatomite Fil-
ters
Construction costs shown in Figure
33 and Table 13 assume a 1 gpm/sq.-
ft. septum area flow rate. Cost
estimates are for a complete
installation, including diatoma-
ceous earth storage, preparation
and feed equipment, filters,
supply pumps, valves and piping,
and controls. Housing costs
assume enclosure in a modular
steel building with minimum space
needed for maintenance. The con-
ceptual design assumes one filter
up to 380,000 gpd (1463 cu.m./d)
and two up to 560,000 gpd (2156
cu.m./d). The required housing
area ranges from 260 to 500 square
feet (24.2-46.4 sq.m.).
Package Complete Treatment Plants
Cost estimates assume standard
manufactured units with rapid mix-
ing, 20 minutes of flocculation,
sedimentation in tube settlers
rated at 150 gpd/sq.ft. (6111 lpd/
sq.m.) tube surface area, mixed
media filters operated at either 2
or 6 gpm/sq.ft. (81.5-203.7 1pm/
sq.m.). The cost estimates
include the following items:
• premanufactured treatment tanks
• mixed media filter materials
• chemical storage tank and feed
pumps
• flow measurement and control
devices
• pneumatic air supply (200 gpm,
12.6 1/s and larger plants) for
valve and control devices
• all controls
• buildings
The plants listed in the first two
columns of Table 14 have low head
filtered water transfer pumps and
are designed to discharge to an
above ground clear well. Larger
plants are assumed to have gravity
flow to an inground clearwell.
Figure 34 shows cost curves for
plants with filters loaded at
either 2 or 5 gpm/sq. ft. (81.5-
203.7 1pm/ sq.m.).
Sludge Dewatering Lagoons
Construction costs assume 7 feet
(2.13 m) deep unlined earthen
V-5
-------
1.000,000
O 100,000
u
3
p
V)
2 GPM/fT2
5 GPM/FT2
l0'°°° I I I I > III! ' « I I I ml I * .... ..I
10 100 1,000
CAPACITY - gpm
+
+
+
10 100
CAPACITY— litan /mc
Figure 32. Construction Cost for Package Gravity Filtration
Plants
Table 1215
Itemized Construction Costs for Package Gravity Filter Plants

Plant
Flow Rate
(gpm)

80*
140*
225*
Cost Category
and 200+
and 350+
and 560+
Excavation & Sitework
830
1,140
1,510
Manufactured Equipment
28,640
37,130
40,310
Concrete
14,840
20,670
28,090
Labor
11,800
13,340
14,330
Pipe and Valves
6,870
8,910
11,810
Electrical & Instrumentation
20,410
26,070
32,450
Housing
48,190
57,830
57,830
SUBTOTAL
131,580
165,909
186,330
Miscellaneous & Contingency
19,740
24,750
27.950
TOTAL
151,320
189,850
214,280
* Lower capacity represents a filtration rate of 2 gpm/sq.ft.
+ Higher capacity represents a filtration rate of 5 gpm/sq.ft.
V-6
-------
Table 1315
Itemized Construction Costa for Package Pressure Diatomite Filters
Plant Capacity (gpd)
Cost Category
28,000
140,000
560,000
Excavation & Sitework
200
220
320
Manufactured Equipment
17,250
32,600
71,400
Concrete
200
250
380
Steel
100
130
170
Labor
4,500
5,200
6,300
Pipe & Valves, Pumps
1,500
1,800
3,100
Electrical & Instrumentation
2,500
2,800
4,200
Housing
13,850
13,850
16,600
SUBTOTAL
40,100
56,850
102,470
Miscellaneous & Contingency
6,020
8,530
15,370
TOTAL
46,120
65,380
117,840
NOTE: 1 gptn = 0.0631 1/s
1 pgd = 0.003785 cu.m./d
1 gpm/sq.ft. ¦ 40.74 lpm/sq.m.
1.000,000
i
£ IOO.I
p

100,000 1,000,000
PLANT CABXCITY- gpd
+
+
100 1000
PLANT CAPACITY- m3/doy
+
10,000
Figure 33. Construction Cost for Package Pressure Diatomite Filters
15
V-7
-------
Table 1415
Itemized Construction Costs for Package Complete Treatment Plants
Cost Category
Excavation & Sitework
Manufactured Equipment
Concrete
Labor
Pipe & Valves
Electrical & Instrumentation
Housing
SUBTOTAL
Miscellaneous & Contingency
(@ 15%)
TOTAL
4*
and 10+
210
13,050
370
5,360
1,060
16,360
15,960
52,370
7.860
60,230
Plant Capacity (gpm)
40
and 100
390
30,770
690
7,360
1,590
21,580
21 ,740
84,120
12,620
96,740
140
and 350
810
72,140
1,950
14,290
3,610
26,990
48,840
168,630
25,290
193,920
* Lower capacity represents a filtration rate of 2 gpm/sq.ft.
(81.5 lpm/sq.m.)
+ Higher capacity represents a filtration rate of 5 gpm/sq.ft.
(203.7 lpm/sq.m.)
NOTE: 1 gpm = 0.0631 1/s
1 gpd = 0.003785 cu.m./d
1,000.000
§ too, ooo
GPM / FT2
"¦POO 1 ¦ 1 ' 1 ,""1
10 100 1,000
CAPACITY - gpm
_| 1 J-
10 IOO
CAPACITY- IIMrt/wc
Figure 34. Construction Costs for Package Complete Treatment
Plants
V-8
-------
basins with 2 feet (61 cm) of free
board (unused depth). Dike side-
slope is 3:1 and dike materials
are assumed obtained from on-site
excavation. The lagoon is provid-
ed with inlet and clear water skim-
ming. Costs per lagoon are a
function of effective volume
(volume at 5 foot (1.5 m) depth,
not including freeboard volume).
Since sludge lagoons are typically
dewatered every several years for
sludge removal, a minimum of 2
lagoons should be provided. Land
costs are not included. Table
15 contains the itemized costs
used to obtain the cost curve of
Figure 35. The Table provides a
cost breakdown for 5 sizes of
sludge lagoon.
Annualizing Capital Costs
Although capital costs are given
as a lump sum, one time cost,
water utilities usually operate on
an annual (yearly) budget cycle.
Thus, to state the total cost of
treatment (capital plus O&M) on a
yearly basis, the capital cost
must be restated in terms of an
annual equivalent payment over the
life of the system in years (n),
allowing for the cost of money, or
interest (i). If the water utili-
ty choses to borrow the entire
capital cost and pay it back in
the form of equal payments over
the project life, the amount of
capital repaid (or recovered),
plus the interest cost is determin-
ed by multiplying a Capital
Recovery Factor (CRF) times the
lump sum cost of the facility:
Annual Capital Cost = CRF X Lump
Sum Capital Cost
In turn, the CRF is a function of
the project life in years (or
payback period) and the cost of
money, i interest.
Many economics handbooks provide
tables of CRF values corresponding
to various combinations of inter-
est and project life. Table 16
is an example of this type of
table, condensed from Reference
23. The cost example of Table 20
shows how this table can be used
to find the annual cost equivalent
of a proposed system's capital
cost estimate.
OPERATION AND MAINTENANCE COSTS
To obtain a total operation and
maintenance (O&M) cost, the indivi-
dual costs for energy (process and
building heating), maintenance
material, and labor must be deter-
mined and summed.
Total Operation and Maintenance
costs from a reference document or
previous contractor's estimate can
be updated and adjusted to local
conditions by updating and adjust-
ing the operation and maintenance
cost components: energy, labor
and maintenance materials. Energy
and labor requirements are general-
ly provided in kilowatts per year
and hours per year respectively
and the curves from Reference 15
provide these as a function of
plant size. To use this type of
curve, the annual consumption is
multiplied by the current energy
or labor costs.
Maintenance material costs are
related to as the Producer Price
Index (PPI) for Finished Goods.
To update this component, the PPI
at the time the original cost esti-
mates were made must be known.
Then the new annual cost is deter-
mined by multiplying the cost from
the graph by the ratio of the new
PPI divided by the PPI at the time
V-9
-------
Table 1515
Itemized Construction Costs for Sludge Dewatering Lagoons
Effective Lagoons Volume (cu.ft.)
Cost Category
1,500
3,500
5,000
17,000
30,000
Excavation & Sitework
500
650
700
1,300
2,000
Concrete
300
300
300
350
600
Pipe & Valves
600
600
600
750
900
Labor
400
500
650
1,000
1,800
SUBTOTAL
1,800
2,100
2,250
3,400
5,300
Miscellaneous &

Contingency (@ 15%)
270
320
340
510
800
TOTAL COST
2,070
2,420
2,590
3,910
6,100
NOTE: 1 cu.ft. * 0.028 cu.m.
10,000

o
o
z
o
jZ 1,000
o
3
K
h
(/)
z
100
100
J I L
JUU
J I I II I III
1,000 10,000
EFFECTIVE STORAGE VOLUME - ft3
1
to 100
EFFECTIVE STORAGE VOLUME - m'
+
1
ipoo
Figure 35. Construction Costs for Sludge Dewatering Lagoons
15
V-10
-------
23
Table 16
Capital Recovery Factors for Some Combinations of Interest (i) and Project
Life (n)
Capital Recovery Factor
n Years 6% 7% 8% 9% 10% 12%
5
0.237396
0.243891
0.250456
0.257092
0.263797
0.277410
10
0.135868
0.142378
0.149029
0.155820
0.162745
0.176984
15
0.102963
0.109795
0.116830
0.124069
0.131474
0.146824
20
0.087185
0.094393
0.101852
0.109546
0.117460
0.133879
25
0.078227
0.085811
0.092679
0.101806
0.110168
0.127500
the graph was prepared. This tech-
nique is also demonstrated in the
example (Table 20).
Within the size range of plants
covered by this document, O&M
costs will rise slowly with in-
creasing plant size. A very small
plant costs almost as much to run
as one 2-3 times larger. With
respect to O&M costs, there are
considerable economies of scale in
larger plants and new/ expanded
facility planning should take
advantage of this where possible.
the filters. Administrative and
laboratory supplies and general
facility maintenance are not in-
cluded. Chemical costs are not
included. Labor costs assume that
the filter will not be attended
full time. Typically, such sys-
tems are attended for 8 to 12
hours/day, operating on automatic
controls otherwise.
Table 17 presents O&M cost data
for filtration rates of 2 and 5
gpm/sq.ft. (81.5-203.7 lpm/sq.m.).
Figure 36 is the associated O&M
cost curve.
Package Gravity Filters
O&M costs include building energy
based on housing floor area and
assuming that all equipment is
enclosed. Process energy is for
filter supply, backwash and
surface wash pumping. Maintenance
material costs were estimated from
operating facilities and include
replacement of washed out media,
small parts, recorder ink/paper
for controls and instruction, and
other supplies required to operate
Package Pressure Diatomite
Filters
O&M data were developed from manu-
facturer data and are representa-
tive of minimum operating require-
ments. Process energy is for
filter and hold pumps, mixers and
other items associated with the
filter system. Backwashing every
24 hours was assumed. Maintenance
materials include spare parts, and
general facility supplies but do
not include chemicals and
V-ll
-------
Table 17
Operation and Maintenance Summary for Package Gravity Filter Plants
15
Energy(kw-hr/yr)
Plant Capacity (gpm) Building Process Total
Filtration rate of 2gpm/sq.ft. (81.5 lpm/sq.m.):
Maintenance
Material
($/year)
Labor
(hr/yr)
Total Cost*
($/year)
80
140
225
280
560
153,900
184,680
184,680
184,680
360,000
3,950
6,920
11,064
13,830
27,660
157,850
191,600
195,740
198,510
387,660
1,070
1,280
1,390
1,600
2.670
2,920
2,920
3,650
3,650
4,380
35,010
36,230
43,760
44,060
58.100
Filtration rate of 5 gpm/sq.ft. (203.7 lpm/sq.m.):
200
350
560
153,900
184,680
184,680
9,470
16,580
26,250
163,370
201,260
210,930
1,070
1,280
1,390
2,920
2,920
3,650
35,170
36,520
44,220
* Calculated using $0.03/kw-hr and $10.00/hr of labor.
-------
10 000
C
o
CD
<
LABOR 2 GPM / FT2
LABOR 5 GPM/FT2
,02° I I I I 11 III I ' i i i 1111 i
10 100 10,000
PLANT FLOW RATE - gpm
PLANT FLOW RATE - liters
Figure 36. Annual Labor Hours for Package Gravity Filters^
3,000
LABOR
w '.qoo
100
10,000 100,000 1,000,000
PLANT FLOW RATE - gpd
100 1000 10,000
PLANT FLOW RATE - m3/day
Figure 37. Annual Labor Hours for Packaged Pressure Diatomite Filters^
V-13
-------
diatomaceous earth.* Labor costs
assume that the filter operates
with little attention except for
preparation of precoat and body
feed, chemical feed adjustment,
and product water quality monitor-
ing.
Table 18 summarizes the O&M costs
used in developing Figure 37.
Package Complete Treatment Plants
O&M costs include building energy
for a totally housed system, and
process energy for operation of
rapid mix, flocculators and filter
washing pumps. Maintenance mater-
ial costs, based on experience at
typical operating installations,
include spare parts, replacement
media and other general suppliers.
Administrative and laboratory
services, chemicals and general
facility maintenance are not
included.
Operator time includes that needed
for adding chemicals and adjusting
feed rates, performing routine
quality control laboratory work,
and carrying out daily maintenance
and housekeeping.
Cost data is provided for filtra-
tion flow rates of 2 and 5
gpm/sq.ft. (81.5-203.7 lpra/sq.m.).
Table 19 summarizes the cost data
used to develop Figures 38 and 39.
Table 20 provides an example of
how capital, O&M, total annual
cost of treatment, and total cost
per 1000 gallons of treated water
can be calculated.
FUNDING SOURCES**
The principal financing options to
small water systems for treatment
process improvement can be categor-
ized as follows:
• Self Financing
- User charges and fees
- Bonding/loans
• Direct Grant Programs
• Subsidized/Assisted Loan Pro-
grams
• Other Assistance Programs
- Labor sharing with other
systems
- EPA technical assistance
activities
These are discussed in turn below:
Self Financing
Water utilities process, deliver
and charge consumers for potable
water. In this, they bear close
resemblence to other businesses
that also produce and sell a pro-
duct. Most of these utilities,
publicly or privately owned, do
not normally have problems in
financing needed capital improve-
ments either through user fees or
changes in the water rate, or by
* Diatomaceous earth is a signifi-
cant expense in operating these
filters. Be sure to include
this cost in your estimate.
** NOTE: Federal financial assis-
tance programs were under sub-
stantial revision at the time
that this document was prepar-
ed. You will need to reconfirm
existing programs and check for
new ones as part of your financ-
ing study.
V-14
-------
Operation
and Maintenance
Table 18
Summary for Package
Pressure Diatomite
Filters^

Energy(kw-hr/yr)

Maintenance
Material
Labor
Total Cost*
Plant Flow Rate (gpd)
Building
Process
Total
($/year)
Chr/yr)
($/year)
28,000
26,700
1,380
28,080
$150
700
$ 7,990
86,000
28,700
4,140
32,840
250
750
8,740
140,000
31,800
6,900
38,700
300
900
10,460
280,000
47,200
13,800
61,000
400
1,100
13,230
560,000
51,300
27,600
78,900
550
1,500
17,920
1,000,000
77,100
51,740
128,840
750
2,900
33,620
* Calculated using $0.03/kw-hr and $10.00/hr of labor.
NOTE: 1 gpd = 0.003785 cu.m./d
-------
Table 19
Operation and Maintenance Summary for Package Complete Treatment Plants
Plant
Capacity Energy(kw-hr/yr)
(gpm) Building Process Total
Energy
Cost
Maintenance
Material
($/year)
Labor
(hr/yr)
Cost
Total Cosf
($/year)
Filtration
Rate of
2 gpm/sq.ft.
:

4
30,780
320
31,100
$ 930
$ 320
1,460
$14,600
$15,850
8
38,780
390
39,170
1,170
590
1,460
14,600
16,360
40
61,560
3,210
64,770
1,940
860
1,750
17,500
20,300
80
98,500
3,950
102,450
3,070
1,600
3,200
32,000
36,670
140
174,420
6,920
181,340
5,440
1,920
3,600
36,000
43,360
225
184,680
11,060
195,740
5,870
2,140
3,600
36,000
44,010
280
277,020
13,830
290,850
8,730
2,570
3,600
36,000
47,300
560
410,400
27 ,660
438,060
13,140
3,210
5,400
54,000
70,350
Filtration
Rate of
5gpm/sq.ft.

10
30,780
780
31,560
950
320
1,460
14,600
15,870
20
38,780
1,560
40,340
1,210
590
1,460
14,600
16,400
100
61,560
7,810
69,370
2,080
860
1,750
17,500
20,440
200
98,500
9,470
107,970
3,240
1,600
3,200
32,000
36,840
350
174,420
16,580
191,000
5,730
1,920
3,600
36,000
43,650
560
184,680
26,520
211,200
6,340
2,140
3,600
36,000
44,480
* Calculated using $0.03/kw-hr and $10.00/hr of labor.
-------
10,000
MAINTENANCE
AfERIAL-
__ J/A^TN^N*fE_
filii "ERIAL 5( PN /H*
1000 1,000,000
BUILDING
BU ILt»IN
E RGY
GP
o 1000 100,000
ni:f
proci:ss
V
UJ
100
10,000
fi -
5 -
100'
>0 2 3 4 5 6 7 8 91000
PLANT FLOW RATE — gpm
10,000
-» 1 1—
I 10 100
PLANT FLOW RATE - liters/*e c
Figure 38. Operation and Maintenance Cost of Packaged Complete Treatment
Plants -.Building Energy, Process Energy and Maintenance
Material
V-17
-------
10,000 >0,000
I
(t
8
<
>090 1022
10
LABOR-2 GPM/FT2
LABOR - 5 GPM / FT2
irawTO-— 1
1 1 I | | ml I 1 » I * Mil L
too
PLANT FLOW RATE -flpm
i,000
1 «"o
PLANT FLOW RATE - liters/*ec
"t
Figure 39. Annual Labor Hours for Packaged Complete Treatment Plants
bonding. However, the financing
needs for constructing and operat-
ing a turbidity removal system may
severely strain small community
water systems, either by requiring
capital expenditures beyond their
ability to finance, or by causing
large incremental increases in
user charges. The latter course
may incur consumer resistance to
the improvement program, a major
impediment in the case of publicly
owned systems. Very small systems
may be particularly vulnerable to
problems in this regard—one study
indicates that up to 30 percent of
systems serving less than 500
people may be unable to finance
turbidity rggoval without outside
assistance.
The prime considerations for self-
financing include the following:
• Amount of revenues available for
payment of interest costs
• Ratio of new treatment capital
coats to existing assets
• Percent rate increase needed to
finance and operate treatment
• Ratio of the typical residen-
tial water bill to the communi-
ty's median family income
In competing for funds on the
private capital markets, the
larger utility is expected to have
a debt service ratio (ratio of
income after operating expenses to
interest costs) of at least 1.3
and income at least twice that of
interest charges. Private utili-
ties must be showing a net profit,
after taxes, of 10 to 13 percent.
User bills should run less than
1.5 to Z.O^gercent of median fami-
ly income.
Smaller utilities may be substan-
tially less robust financially,
and still be able to raise money
locally. Utility customers may be
willing and able to put up the
needed capital. Even so, the util-
ity should have a debt service
ratio of at least 1.0 so interest
V-18
-------
and bond repayment schedules can
be me t.
Grant Programs
The principal financial assistance
program available to small communi-
ty water systems (public or pri-
vate nonprofit) is operated by the
Farmers Home Administration (FmHA)
of the Department of Agriculture.
FmHA can grant up to 75 percent of
the cost for installation, repair
or upgrading of community water
systems that serve fewer than
10,000 people and meet certain
median income criteria. The empha-
sis is on farmers and other rural
residents .
Program aid priorities are as
follows:
• Public bodies and towns with
emphasis to those serving 5,500
people or less
• Assist compliance with Safe
Drinking Water Act
• Low income communities receive
pre ference
(1) User charges must be at least
equal to other similar, al-
ready established systems, on
the basis of:
• Similar costs of contruction
and operation
• Similar economic conditions
(2) Debt service costs exceed net
levels as determined by the
ratio of mean family cost for
water service to median family
income. Specifically:
• For communities of median
family income less than
$6,000, debt service must
exceed 0.75 percent of
median family income to be
eligible.
• For communities of median
family income, $6,000 to
$10,000, debt service/in-
come must exceed 1.0 per-
cent for eligibility.
• For communities exceeding
$10,000 median family
income, debt service/income
must exceed 1.25 percent
for eligibility.
FmHA can be contacted for further
information at any one of 340
offices nationwide.
The Economic Development Adminis-
tration (EDA) has some limited
programs for water/sewer assis-
tance, primarily keyed to promot-
ing industrial development and
employment and creation of jobs.
Grants can range from 50 to 80
percent of project costs (up to
100 percent for Indian Tribes) and
public or private nonprofit agen-
cies may qualify. EDA has six
regional offices and staff in each
of the 50 states.
The Department of Housing and
Urban Development (HUD) has a
program of Community Development
Block Grants (CDBG) that are admin-
istered locally and used for a
wide variety of community improve-
ment projects. You can apply for
funding through city and/or county
governments in which your system
is located.
Direct Loan Programs
Three federal agencies operate
direct loan programs:
• Department of Interior - has two
programs available to public
nonfederal entities in the 17
western states.
V-19
-------
• Farmers Home Administration -
has loan program with similar
criteria to those used in their
grant program. The loan can be
for 100 percent of the project
cost.
• Small Business Administration -
has a number of loan programs
that may be used by small inves-
tor-owned water utilities.
Loans cannot exceed $150,000.
Loan Guarantee Programs
Both the Small Business Administra-
tion (SBA) and the Farmer's Home
Administration (FmHA) can provide
backing for privately placed loans
as follows:
• SBA - will guarantee up to 90
percent of a loan up to $500,000
for private, independent busi-
nesses that are refused a bank
loan.
• FmHA - has a Business and Indus-
try Loan Program available to
public or private organizations,
particularly those located in
rural areas and serving fewer
than 2,500 persons. Loan
guarantees range up to 90
percent of face value.
Other Forms of Assistance
Other ways of reducing financing
and/or operating costs include the
following:
• Bond banks - Several states have
central bond banks that assist
localities in the mechanics of
bond financing. By aggregating
small bonds into larger ones,
interest costs may be reduced
and bond placement enhanced.
• State loan programs - Several
states provide direct loans for
construction of public water and
sewer projects. The programs
are normally operated under the
aegis of state economic develop-
ment offices.
• Shared operation costs with
other nearby utility(s) -
Regionalization is one approach
to shared operating expenses.
V-20
-------
Table 20
Sample Cost Analysis for a 140 gpm Complete Treatment Plant
STEP 1: Calculate Cost Adjustment Factors as of June, 1982.
A. Construction Cost = Current ENR CCI
Escalation Factor Base ENR CCI
(CCEF )
The cost curves of Reference 15 are based on October, 1978, costs,
when the ENR Construction Cost Index (CCI) stood at 265.38. The June,
1982, ENR CCI was 352.92.
Therefore, CCEF = 352.92 = 1.33
265.38
B. Maintenance Material = Current PPI
Cost Escalation Factor Base Year PPI
(MMCEF)
The October, 1978, Producer Price Index (PPI) issued by the U.S.
Department of Commerce, was 199.7. The June, 1982, PPI was 299.4.
Therefore, MMCEF = 299.4 = 1.50
199.7
STEP 2: Estimate Construction Cost Using Figure 34.
From Figure 34, Construction cost in October, 1978, dollars, is
$190,000 for a 140 gpm plant with a 2 gpm/sq.ft. filter rate.
June 1982 = $190,000 x CCEF
Construction Cost
= $190,000 x 1.33 = 252,700
From Figure 35, Construction cost in October 1978 dollars, is
$6000 for a 30,000 cubic foot (852.3 cubic meter) sludge storage
lagoon for process wastewater storage.
June 1982 = $6000 x CCEF
Constr. Cost
= $6000 x 1.33 = $7980
Total Construction Cost = $252,700 + $7900 = $260,680
(Continued)
V-21
-------
Table 20
Sample Cost Analysis for a 140 gpm Complete Treatment Plant
STEP 3: Estimate Annual O&M Cost
A. Maintenance Material
From Figure 38, October, 1978, annual maintenance material cost is
$1,600.
June 1982 = $1,600 x MMCEF
Maintenance Materials Cost
= $1,600 x 1.50 = $2,400
B. Energy Cost
Energy Use = Process Energy + Building Energy*
From Figure 38,
Energy Use = 150,000 kwh/year + 7,000 kwh/year
= 157,000 kwh/year
Energy Cost/Year = kwh/year x energy cost
kwh
For this example, assume energy cost of $0.05/kwh
Energy Cost/Year = 157,000 x $0.05
= $7,850
C. Labor Cost
From Figure 39, Labor, hr/year = 3,000. If labor costs $12 per hour
(including fringe costs), annual labor cost is calculated as follows:
Annual Labor Cost = 3,000 hours x $12/hour
year
- $36,000
D. Total O&M Cost
Total O&M Cost * Maintenance Material Cost + Energy Cost «•
Labor Cost
= $2,400 + $7,850 + $36,000 = $46,250
* Building energy is very dependent on climate. If possible, estimate
this directly for your area.
(Continued)
V-22
-------
Table 20
Sample Cost Analysis for a 140 gpm Complete Treatment Plant
STEP 4: Annualize Construction Cost
If the cost of money is 10 percent, and the system has a 20 year
design life, the annual equivalent of the construction cost is as
fo1 lows:
Annual Capital = Capital x Capital Recovery Factor,
Equivalent Cost 10 percent, 20 years
The capital recovery factor from Table 16 for 10 percent and 20 years
is 0.117460.
Annual Capital Equivalent = $260,680 x 0.117460
= $30,620 per year
STEP 5: Sum Annual Costs of Construction and O&M and Determine Cost per
1,000 Gallons Treated*
A. Annual Cost Summary
Capital $30,620
Operation and Maintenance:
Maintenance Materials 2,400
Energy 7,850
Labor 36,000
Total $76,870
B. Annual Treated Flow, Thousands of Gallons
Annual Treated Flow = 140 gpm x 1440 min x 1 x 365
(1000 gallons) day 1000
= 73,584
C. Cost per 1000 gallons treated**
Cost/1000 gallons = Annual Cost
Annual Treated Flow (1000 gallons)
$76,870
73,584 (1000 gallons per year)
Cost/1000 gallons = $1,045
* This does not include chemical costs which are specific to
the water being treated.
** This does not include waste disposal costs other than the annualized
capital cost of the lagoon.
V-23
-------
VI. OPERATION AND MAINTENANCE
Packaged water treatment systems
will provide long, low maintenance
service if properly cared for.
The equipment does not normally
require continuous operator super-
vision because of control systems
which monitor turbidity levels and
automatically adjust coagulant
dosage and filter backwashing.
Preventive Maintenance (PM) is the
key to long, trouble free perfor-
mance. This section of the Manual
sets out recommended monitoring
and PM activities for a typical
small packaged complete treatment
or direct filtration water treat-
ment plant.
OPERATOR REQUIREMENTS
Operation of a packaged water
treatment plant does not require
unusual operator skills. However,
the operator should be reasonably
expert in basic plumbing and elec-
trical skills and should under-
stand the operation and repair of
simple pumps, valves, water meters
and controls. He or she must be
capable of carrying out a program
of periodic sampling and be able
to use a Nephelometric Turbidity
Test Meter, make simple calcula-
tions and keep organized legible
records. He/she must be able to
conduct jar tests and must under-
stand and be able to apply the
basic principles of coagulation
chemistry. The operator should be
of sufficient intelligence and
schooling to understand the funda-
mentals of process operation and
be able to attain state certifica-
tion where required.
Operator time requirements are
dependent on system size. How-
ever, it is not likely that he or
she will spend more than one regu-
lar shift per day monitoring and
maintaining the plant.
MANUALS, EQUIPMENT AND SUPPLIES
NEEDED
Provide the system operator with
the service manuals, tools, analy-
tical equipment and supplies need-
ed to properly maintain the
system. For example:
• System maintenance manual
for each individual piece
of equipment and the system
as a whole.
- Startup, test, routine
(preventive) maintenance,
trouble shooting guide.
- Schedule of routine main-
tenance activities and
tools/supplies for each
task. The schedule
should be laid out on a
daily, weekly, monthly,
quarterly and annual
basis as needed.
- Sources, including name,
address and telephone
numbers, for emergency
parts and service. This
should also be posted
near the equipment.
- Operational directions,
including detailed con-
trol settings for electri-
cal controls, motorized
valves, flowmeters,
pumps, etc.
- Sampling and test proce-
dures and schedules for
process monitoring and
reporting to the state.
VI-1
-------
- Appropriate sample forms for
recording maintenance proce-
dures and water quality data.
Format of recommended record
keeping.
• Recommended tools and critical
spare parts for each item, such
as lubricants, valve and pump
gaskets and packing, electrical
fuses. Stock key spare parts
that are not available locally
or overnight from manufactur-
er 's warehouse.
• Test Equipment for Process
Contro1
- Alkalinity
- Turbidity
- PH
- Chlorine
• Supply of coagulating and pH
adjustment chemicals.
STARTUP TRAINING AND ASSISTANCE
A trained representative of the
manufacturer should be present
when starting up a packaged water
treatment system. He should train
your operators and check the equip-
ment out fully. Normally, this
should require several weeks time
and the cost of this service
should be included in the price of
the equipment. The manufacturer
should also provide a detailed
service manual for the equipment.
MONITORING
Monitoring encompasses two activi-
ties :
(1) Monitoring to satisfy regula-
tory requirements
(2) Monitoring for process
control
Regulatory requirements (see
page 11 — 5) for turbidity require
you to monitor and record turbidi-
ty data daily. Table 3, on page
II-6, is a form which can be used
for recording turbidity data. The
form allows you to calculate and
record the 2 day average turbidity
as well.
Remember that the turbidimeter
should be calibrated before each
series of tests, at least once
daily. Also, standard solutions
must be periodically replaced.
Obtain replacement standards from
the instrument manufacturer or a
nearby certified laboratory unless
you have the equipment and person-
nel to prepare them in-house.
Monitoring for process control
requires use of the turbidity
meter to check the operation of
the automatic control system. A
daily check is recommended. Ana-
lyze influent and effluent turbidi-
ties and compare them with the
data logged by the automatic moni-
tor. If the variation exceeds
that called for in the service
manuals, check and adjust the
system as specified. Your plant
should be equipped with continuous
reading turbidimeters for both raw
and finished water turbidities.
These should be equipped to sound
alarms or other indicators in the
event of major changes in turbidi-
ty. For example, the raw water
turbidimeter for a system whose
water averages 5 NTU might be set
to automatically sound an alarm if
a 10 NTU level is exceeded. The
treated water turbidimeter should
sound an alarm if turbidity
exceeds 1 NTU.
As coagulating chemicals may
affect finished water pH, this
should also be checked daily, at
the same time that turbidity is
checked. Use a pH test kit or
portable pH meter for this check.
VI-2
-------
COAGULATION CONTROL AND MONITORING
As part of the process study and
design process, your engineers
will have characterized the raw
water supply characteristics and
performed sufficient jar tests and
other analyses to select the pri-
mary coagulant(8), coagulant aids
(polymers), and approximate dosage
ranges. It is the job of the
plant operators, during the first
few months after plant startup to
"fine tune" the coagulant system
by developing a control and moni-
toring scheme that suits your par-
ticular raw water and treatment
plant.
Setting up a coagulant control
program that works for your system
includes the following steps:
• Operator training: Enroll
operatoj^ in state, local
college and/or professional
association (such as AWWA)
training courses that stress
treatment plant operation and
coagulation control. If a
packaged plant is used, make
sure that the supplier includes
onsite operator training in his
bid. Plan on a continuing
effort in operator training
which includes additional
training annually, and
subscriptions to trade
publications. Contact the
American Water Works Associ-
ation, 6666 W. Quincey Avenue,
Denver, Colorado 80235, for a
listing of their current
manuals and training aids for
small water systems and obtain
those which suit your situa-
tion.
• Review Nearby Plant Practices:
Quite possibly, there are other
plants nearby treating the same
raw water supply. Find out
about these from your state
health department or state
water supply agency and spend
some time talking with their
operators to find out their
experience.
• Consult the Chemical Manufac-
turer: Chemical suppliers are
an excellent source of applica-
tions expertise. Ask your
coagulant supplier about any
literature, training aids,
trouble shooting assistance or
other services available from
his firm.
• Conduct Jar Testing: Conduct
a series of jar tests for your
raw water over its range of con-
dition. Find out how much
coagulant and polymer is needed
for the high and low range of
turbidities (such as might
occur after a heavy rain or dur-
ing extended low flow periods).
Use the jar test to determine
the optimum pH for your coagula-
tion system and develop a
scheme for pH monitoring and
control. Over a period of time
you will develop a body of data
which, when combined with opera-
tor observations, can be used
to set up a coagulant control
scheme. Figure 40 is an
example of a graph that you
might prepare as a guide for
coagulation control.
v>
o
0
RAW WATER TURBIDITY
( NTU )
Figure 40. Sample Coagulant Con-
trol Curves
VI-3
-------
If your plant is equipped with
automatic coagulation control
equipment you can use the steps
above to set up the operating
program for the controller. A
properly set up automatic control
system can reduce the need for
continuous supervision of the
coagulating process. IT IS NOT A
SUBSTITUTE FOR DIRECT OPERATOR
SUPERVISION. Coagulation is a
critical process in the water
treatment scheme and needs to be
given close attention by plant
operators.
The water quality monitoring
instruments, particularly those
for pH and turbidity, are the
"eyes" of your coagulation control
system. Set up a separate check-
ing and maintenance program, in
accordance with manufacturers'
recommendations, for these impor-
tant instruments. At least twice
daily, check the continuous turbi-
dimeter readings against samples
tested on your laboratory turbidi-
meter and make appropriate adjust-
ments and/or repairs.
PREVENTIVE MAINTENANCE
Preventive maintenance (PM) is the
key to reliable service and long
equipment life. Close attention
to PM activities will reduce
annual costs and minimize system
failure. A detailed schedule of
PM activities should be provided
by the packaged plant manufacturer
along with the service manual.
Startup training should include a
thorough grounding in PM activi-
ties. Appendix D is a listing of
typical PM activities for a pack-
aged complete treatment plant.
Setting Up a Formal PM System
mixers, drivers, controls, meters,
etc., each with its own mainte-
nance requirements. You can set
up a simple maintenance schedule
and recordkeeping system which
will help manage the preventive
maintenance function. Also, it is
useful as a management tool to
identify where your time (and
money) is being spent and spot
failure prone system components.
The first step is to develop an in-
ventory of each piece of plant
equipment you wish to cover in the
PM system. In general, any equip-
ment directly involved in the
treatment plant process with mov-
ing parts requiring periodic main-
tenance should be covered. Figure
41 is an example of an equipment
inventory sheet that could be
used. Each piece of equipment is
assigned a number which is used on
all records. The number is paint-
ed onto the equipment as well.
For each item on the equipment
inventory, a Maintenance Data
Form, shown in Figure 42, is set
up. This form records pertinent
data on the item such as its model
and serial numbers, installation
date, location, power require-
ments, and a record of maintenance
actions taken on it. This is an
extremely useful form as it can
show you at a glance the history
of a piece of equipment. Numerous
entries closely spaced in time may
indicate that a particular piece
of equipment is failure prone and
should be replaced or modified.
There are three main sources of
maintenance data which can be used
to develop the plant PM system:
• Equipment Manuals
• The Equipment Manufacturer
• Experience of Plant Operators
Even the smallest water treatment
plants may have numerous pumps,
VI-4
-------
O) (2) (3) (4)
Equipment
Numbe r
Equipment
Name
Type of
Equipment
Location of
Equipment

Figure 41. Equipment Inventory Sheet
Equipment number - use any number of series of numbers that
will uniquely identify the equipment. The number should also
be painted conspicuously on the equipment.
Name as given in the plant specification or as given by the
manufacturer.
Describes briefly the equipment function and power source.
Provides sufficient detail for finding the equipment readily.
NOTES: (1)
(2)
(3)
(4)
VI-5
-------
(A) Front Side
Equipment Name and Number
Type
Location
Manufacturer
Local Representative Part or Model Number Serial Number
Reference Drawing
Reference Catalog Introduction Book Date Put In Service
Electric Motor
Pump
Drive or Reducer
HP Frame
RPM
Capacity
TDH RPM
HP RPM in
RPM Out
Volt a Amps Phase
Impeller Packing
Ratio
Type
O Series
O Shunt
Q Synchronous
0 Introduction
n
Specifications
~ Open
PI Exp. proof
~ Drip proof
0 Totally enclosed
~
Type
0 Centrifugal
I~~] Plunger
~ Diaphragm
0 Gear
~ Screw
n
1nstallation
0 Horizontal
0 Vertical
0 Submersed
Lubrication
0 Water
n on
O Grease
Type
~ Gear
~ V-Belt
n Chain
D Va rid rive
Bearings
~ Sleeve ~ Ball DRoller
Bearings
^Sleeve 0Ball 0Roller
Bearlnga
Dsieeve 0Ball 0 Roller
Lubricant
Lubricant
Lubricant
Other Equipment
Type, Speed, Size, Capacity, Range
Bearings, Lubricant
Other Features
(b) Reverse Side
CORRECTIVE MAINTENANC
E WORK RECORD
Date
Mechanic's Name
Reg. Hrs.
OT Hrs.
Parts or Mtls.
Manufacturer and
Catalog No.
Cost

Describe what was found wrong and how it was fixed
CXitslde Contractor Used

Reason
Recommendation for avoiding repeated failure
Actua
1 Costs
Labor

Parts

Contractors
Equipment Status of Completion
Fully operational
Non-operational
Reduced capability
Awaiting spare parts
Spare Parts Availability
In stock
Obtained locally
Delay in procurrlng
Length
Total
Total Down-Time
Work Completed
Date Malnt* Foreman
Wo I
Dat
¦k Accepted
e Requestor

Figure 42. Equipment Data Sheet
VI-6
-------
This data can be compiled in the
form of a maintenance procedures
sheet (MPS) as shown in Figure 43,
which lists the specific steps and
spare parts needed to carryout a
specific maintenance activity.
You will need one of these for
each identifiably distinct main-
tenance action on a piece of equip-
ment. They can be tied together
in a numbering system which is
coordinated with the plant inven-
tory listing. For example, equip-
ment item 10 might have 4 associat-
ed maintenance procedure forms,
numbered 10-01, 10-02, 10-03, and
10-04. These forms would be kept
in sequence in a book or file for
ready access and reference by main-
tenance personnel.
There are two main types of main-
tenance activity: Routine (perio-
dic) preventive maintenance (PM) ,
and repair maintenance. The for-
mer is carried out on a regular
schedule, the latter is performed
on equipment that has broken down
or is expected to fail shortly.
You will need to prepare and
follow a PM schedule, an example
of which is shown in Figure 44.
One of these is prepared for each
week of the year and includes
daily, weekly and periodic PM
activities. Figure 45a is the
form used to report trouble and
request needed repair. When a
maintenance action is carried out,
either for PM or for repair, it is
reported on the back of the mal-
function report form (Figure 45b).
In turn, this data is entered on
the permanent record for the equip-
ment item (Figure 42).
You should give serious considera-
tion to setting up a PM system for
your plant. It can be a valuable
management tool for tracking O&M
activities and associated costs.
Too, the improved equipment main-
tenance that results from the use
of a PM system will prolong equip-
ment life and cut repair costs.
This in turn, can lead to more
consistent, higher quality water
production.
EMERGENCY PROCEDURES
Should excessive turbidity break
through the final filter, the sys-
tem should be shut down immediate-
ly and the filter backwashed. Be-
fore restarting, check for over
accumulation of sludge in the
settling chamber and check and
adjust chemical feed as needed.
After returning the unit to ser-
vice, check and calibrate turbi-
dity monitors and verify that tur-
bidity standards are being met.
Diagnose the cause of the failure
and modify operating procedures to
prevent a reoccurrence. Observe
all State regulatory requirements
regarding notification and monitor-
ing.
SAFETY PROCEDURES
Owners of packaged water treat-
ment systems that use coagulation
should take normal safety precau-
tions where strong chemicals are
used. An emergency shower and eye
wash fountain should be provided
adjacent to the chemical mixing
area. A washing hose and floor
drain should be provided in the
chemical treatment section of the
plant. Operators should wear
protective gloves and face shields
when handling chemicals, particu-
larly those used for pH adjust-
ment. Provide adequate ventila-
tion and a high capacity exhaust
fan that can be turned on to quick-
ly clear out dusts and vapors from
chemicals.
VI-7
-------
MAINTENANCE PROCEDURE SHEET
(1)
MPS
Page 1 of 1
Equipment Name and Number
Plant Area Location
Maintenance Description
(2)
Safety Precautions
Tools, Parts, Materials, Test Equipment
Procedure
Figure 43. Maintenance Procedure Sheet
NOTES: (1) The MPS Number should include the equipment number plus a
number or letter for the MPS. For example 1-A, 1-B, I-C might
refer to a series of MPS for a given piece of equipment.
(2) Should include a reference to any maintenance manuals for the
piece of equipment.
VI-8
-------
ill
Equipment Name/No.
Maintenance Action
MPS No.
Frequency

Figure 44. Weekly Preventive Maintenance Schedule
NOTES: (1) Frequency is either: D - Daily
W - Weekly
P - Periodic, performed only when listed
on the weekly schedule
VI-9
-------
(a) Front Side
CORRECTIVE MAINTENANCE WORK REQUEST
Date
Requested by
Required Completion Date
Equipment N*ne and Number
Location
Indication of Trouble
OBroken Part
Oworn Part
~ Heat
~Nolae
~ Sim 11
D Vibration
~ leaking
Dother
O Dirty, fouled
~ Voltage
D Current
~ Assistance
OfIov rate
~ Pressure
Ospeed
When D1 sccrvered
~ Starting
O Stopping
~ During Operation
~ During PM
~ During CM
~ During MOD
~During ON
~ other
Cause of Trouble
CD Heat/cold/weather
O Humidity/moisture
CD Foreign object
[U Shock/vlbratlon
~ Wear
CD Equipment defect
~ Improper installation
~ improper lubrication
~ Improper operation
~ Other
Corrective Vork Requested
Approved by
Date
Estimated Coats
Labor
Parts
Contractors
Total
Estimated Down-Time
Job No.
(B) Reverae Side
PARTS LIST
Name of Part
Manufacturer
Cat. No.
Local Supplier
Cost

Figure 45. Report of Trouble/Corrective Action Form
VI-10
-------
VII. CASE HISTORIES
CARLISLE, PENNSYLVANIA
The Carlisle Suburban Authority,
located in south central Pennsyl-
vania, serves a current population
of 4,500 outside of the town of
Carlisle with water and sewer ser-
vices. The Authority operates a
combined water treatment and waste
water treatment/disposal plant
located adjacent to Conodoqumet
Creek, in the eastern suburbs of
Carlisle.
The Creek is typical of many
medium sized eastern streams drain-
ing areas which have both exten-
sive agricultural and industrial
development. Turbidity, which
averages 4 NTU, can exceed 200 NTU
after significant rainfalls. pH
ranges from 6.5 to 7.8. Extended
dry periods may cause the stream
to dwindle to a trickle. By the
time that the stream reaches
Carlisle, it has received efflu-
ents from a number of domestic and
industrial sources.
The treatment plant uses two
complete treatment packaged plants
operated in parallel, each of 280
gpm (17.7 1/s) capacity with the
mixed media filters operating at
their design capacity of 5 gpm/sq.
ft. (203.7 lpm/sq.m.). The pack-
aged plants feature flash mixing
of the alum and polyelectrolyte
coagulants followed by floccula-
tion in horizontal paddle mixed
flocculators of 17 minutes deten-
tion time. (Figure 46)
Tube settlers in each unit of 105
sq.ft. face area (9.75 sq.m.),
loaded at 2.6 gpm/sq.ft. (106
lpm/sq.m.) settle the flocculated
water before it enters the mixed
media filters. Each mixed media
filter has 56 sq.ft. (5.2 sq.m.)
of surface area and includes facil-
ities for high rate backwashing
and surface washing. The plant
engineers elected to use a program-
mable solid state digital control-
ler for automatic backwash control
instead of the mechanical system
normally provided by the manufac-
turer of the package plant. The
reason cited for this change was
that the electronic controller
gave the plant operators far
greater flexibility in varying
filter cycles.
Alum is the primary coagulant,
supported by a polyelectrolyte
coagulant aid. Alum is normally
added at a rate of 12-23 mg/1 with
polyelectrolyte added at 1% of
this rate. A small quantity of a
filter aid polymer is also added
to extend filter runs and improve
performances. Powdered activated
carbon is added into the filter
head tanks for taste and odor
control at the beginning of each
filter cycle (12 hours). The
plant is operated 5 days per week,
12 hours per day with two shifts
of operators.
Construction of the plant immedi-
ately adjacent to the sewerage
treatment plant has allowed the
Authority to combine their opera-
tion, with considerable cost sav-
ings. Both plants use liquid
alum, stored at the sewage plant.
A staff of four operators and a
superintendent run both plants and
maintain the system's distribution
and collection piping, pumping
stations, fire hydrants and water
meters. Wastes from the water
treatment plant are discharged to
an equilization tank below the
floor of the water plant and
VII-1
-------

>y 7
Figure 46. Carlisle, PA Packaged Complete Treatment System
VII-2
-------
gravity fed continuously to the
headworks of the sewage treatment
plant. Provision has also been
made to skim the supernatant from
the holding tank for recycle to
the water treatment plant during
drought conditions. Plant opera-
tors report that the water treat-
ment sludge has had a significant
beneficial impact on the operation
of the wastewater treatment plant.
The two plants also share a joint
control room/laboratory which
features centralized monitoring
and control of all equipment and
processes. The compact and func-
tional design maximizes shared
facilities and operator efficien-
cy. Laboratory space is ample and
well laid out (Figure 46).
This plant is an excellent example
of the combination of good equip-
ment and design, with conscien-
tious operation. Chemical mixing
and feeding equipment is well
located and accessible to opera-
tors. Provision has been made for
quick and easy cleanup of chemical
spills. Control and monitoring
equipment is highly visible and
easy to work on.
The packaged treatment plants were
supplied by a leading U.S. manufac-
turer with extensive experience in
water treatment. The opportunity
to integrate water and wastewater
treatment and support facilities
has been maximized, with close
attention given to protecting the
water supply. The operators were
given extensive startup training,
and there is a continued commit-
ment to training, averaging 1 week
per year per man. The specifica-
tion of high quality materials and
construction for both buildings
and equipment is evident, and
conscientious housekeeping and
maintenance is practiced by plant
operators who appear to have
substantial pride in the plant.
After several months for startup
and shakedown, plant operators
reported that operation has been
almost trouble free. The polyelec-
trolyte metering and feed pumps
was found to be undersized and was
replaced with a larger unit. Some
trouble was experienced in learn-
ing the operation of the backwash
controller. Also, operators have
found the controls for shutting
down either of the two parallel
units to be somewhat inconvenient.
The plant is consistently produc-
ing highly clarified water, averag-
ing 0.3 NTU or less in turbidity.
When the adjacent Town of Carlisle
water treatment plant suffered a
major breakdown, Carlisle Suburban
operated their system 24 hours per
day at 60% over the design flow
rate, successfully meeting the
emergency without seriously lower-
ing the quality of the finished
water.
The water treatment portion of the
system was constructed in 1978-79
at a cost of $634,540 for general
construction and $179,730 for
electrical work (Table 21). The
packaged treatment plants and
appurtenant chemical mixing and
feeding equipment cost $133,190.
The plant was formally placed in
service in December of 1979.
HANCOCK, MARYLAND
Hancock, Maryland, located in the
western part of the state, upgrad-
ed and expanded an existing treat-
ment system with a packaged
complete treatment system. The
560 gpm (35.3 1/s) plant was
installed in October 1979 to treat
surface waters from the Little
Conoloway Creek. Raw water turbi-
dity averages 5 NTU but can rise
to very high levels after a rain-
fall. Figure 47 is a photograph
of the interior of the plant
VII-3
-------
Table 21
Carlisle Suburban Authority, Pennsylvania Plant Data
Manufacturer/Model
Rated Capacity (2 parallel units)
Raw Water Data:
Turbidity, NTU
pH
Alkalinity mg/1
Finished Water
Turbidity
PH
Neptune Microfloc
Aquarius 112
560 gpm (35.5 1/s)
4 to 200
6.5 - 7.8
150
0.3 - 0.4
7.5
Chemical Feed Rate (avg. Conditions)
Alum, mg/1
Polyelectrolyte mg/1
Lime
7.5 as needed for taste and Activated Carbon odor control
Filter aid (polymer) Trace
17-23
0.17-0.23
As needed to adjust pH to
Filters
Type
Area, each filter
Design Loading
Mixed Media
56 sq.ft. (5.2 sq.m.)
5 gpm/sq.ft. (204 lpm/sq.m.)
Cost
Package Plant and Chemical Mix/Handling $133,190
Total Facility, including equipment,
installation, and housing (Engineering
and legal fees not included). $634,540
VII-4
-------
Figure 47. Hancock, MD Packaged Complete Treatment System
VII-5
-------
housing, showing the controls and (3)
chemical mixing/metering system.
Alum and polyelectrolyte are used
for coagulation.
The water treatment process fea-
tures two parallel sections with
rapid mixing, flocculation with
vertical paddle flocculators,
parallel plate settlers, and dual
media filters. The filters have
18 inches of 0.45 to 0.55 mm sand (4)
under 12 inches of anthracite and
are rated at 4.6 gpm/sq.ft. at
design flow (Table 22). The back-
washing system includes provision
for air scouring. Alum sludge is
disposed by land spreading and
filter backwash water is sewered
although the plant has provision
for recycling this stream. Wet
well for storage of finished
water, alum sludge and backwash
water are located under the floor
of the attractive brick building
which houses the plant.
(5)
The plant has experienced severe
equipment and operational problems
since startup. These are some of
the most significant:
(1) The calibration curves provid-
ed for the operator to use in
correlating chemical dosage
are apparently incorrect. (6)
The settings on the chemical
feed pumps are not accurate.
(2) The raw water supply is high-
ly variable in quality. No
provision was made to level
out the variability (i.e., a (7)
presettling pond). No equip-
ment has been provided to
automatically monitor the raw
water quality and alert the
operator to large fluctu-
ations. Hence, chemical feed-
ing is often incorrect, caus-
ing high loading to the
filters. (8)
The plant was originally pro-
vided with a rotary micro-
screen for flocculated solids
removal. This equipment
failed and was replaced with
parallel plate settlers.
Plant operators indicated
great difficulty in desludg-
ing the settlers and the
settler wet well.
Due to frequent failure of
the chemical addition system,
solids are not being effec-
tively removed by the floccu-
lation/settling step. This
causes solids overload of the
filters, resulting in the
need to backwash the filters
more often than anticipated
in the original design.
About 20,000 gallons per day
of ground water is being used
to wash both filters twice
per 16 hour running day.
The plant is being operated
on a 2 shift, 16 hour day.
When restarted, the initial
product water is quite tur-
bid. No provision has been
made to bypass this water to
prevent degradation of the
treated water supply.
It is necessary to shut down
the plant to stop the raw
water feed to the chemical
injection pumps. This
increases the difficulty of
repair.
The chemical injection pumps
supplied with the packaged
treatment system have been
inaccurate and unreliable.
No nearby source of service
or parts is available and
the plant does not stock
spare parts or a spare pump.
The air scour backwash system
causes cratering in the
VII-6
-------
Table 22
Hancock, Maryland Plant Data
Manufacturer/Model
Rated Capacity (2 parallel units)
Raw Water Data:
Turbidity, NTU
pH
Alkalinity mg/1
Finished Water
Turbidity
F low
(1514-1892 cu.m/d)
Chemical Feed Rate
Alum
Polymer
Filters
Type
Media
Sand 0.45 to 0.55 mm
Anthrac ite
Area, each filter
Design Loading
Cost
Package Plant and Equipment
Building and Wet Wells
Paddock Re finite
560 gpm (35.5 1/s)
4 to 10 avg, over 200 maximum
7.5
165
1 or greater
400,000 to 500,000 gpd
Unknown
Intermittent
Dual Media
18 inches (45.5 cm)
12 inches (30.5 cm)
60.5 sq.ft. (5.6 sq.m.)
4.6 gpm/sq.ft. (187 lpm/sq.m.)
$229,657
$180,444
VII-7
-------
filter bed. Air flow
solenoid valves regularly
stick and must be rapped
sharply to be operated.
The plant operators have express-
ed dissatisfaction with the start-
up service and training provided
on the project. Operation and
maintenance of the chemical feed
system was singled out as the
major problem area. Also, the
lack of automatic turbidity moni-
toring control on a highly vari-
able water supply is a problem as
there is only one operator
normally on duty during each
shift and he has numerous other
duties which require leaving the
plant for short periods of time.
Recently, the town retained an
outside engineering consultant to
diagnose the plant's problems and
recommend remedial measures.
plants, but 20 percent of the
plants treated water that
exceeded 100 NTU at times.
• Seven plants used single stage
rapid mix, six used two stage,
and mixing time varied from 15
seconds to 5 minutes. One did
not report.
• Eight plants used floccula-
tion, nine did not.
• Fourteen plants used dual or
mixed media; three used sand or
coal single media. Thirteen
plants used gravel media
supports.
• Filtration rates ranged from
2-5 gpm/sq.ft. Backwash rates
ranged from 8-22 gpm/sq.ft.
Ten plants had filter bed
surface washing. The average
filter run between cleanings
was 5-8 hours.
DIRECT FILTRATION—17 PLANT SURVEY
19
Culp reported data from a
questionnaire directed at 100
direct filtration plants. The 17
responding plants ranged in size
from 0.5 mpd to 200 mgd. The
following data was reported:
• Average raw water turbidity was
less than 25 in all of the
• Five plants add alum alone, 6
plants add alum and a polymer,
three add only polymer. Three
did not report.
• Eight plants had continuous
turbidity meters.
The reference also provides a
partial listing of direct
filtration plants.
VII-8
-------
REFERENCES
1. S. P. Hansen, "Package Plants: One Solution to Small Community Water
Supply Needs," Journal AWWA, June 1979, pp. 315-323.
2. R. M. Clark and J. M. Morand, "Package Plants: A Cost Effective
Solution to Small Water System Treatment Needs," Journal AWWA,
January 1981, pp. 24-30.
3. Standard Methods for the Examination of Water and Wastewater, 15th
Edition, Water Pollution Control Federation, Washington, DC, 1980.
4. E. S. Postgate, "The Health Risks of Turbidity," Water & Pollution
Control Magazine, May/June, 1978, p. 30.
5. The Safe Drinking Water Act Self Study Handbook, Community Water
Systems, American Water Works Association, 6666 W. Quincey Avenue,
Denver, Colorado 80235.
6. Methods for Chemical Analysis of Water and Wastes, U.S. EPA
600/4-79-020, 1979.
7. 1981 Buyers Guide, Journal AWWA, November 1980, Part 2.
8. Process Design Manual for Suspended Solids Removal, U.S. EPA
Technology Transfer, January 1975.
9. 1981 Year Book, Water Pollution Control Federation Journal, March
1981, Part 2.
10. Water Quality and Treatment, A Handbook of Public Water Supplies,
McGraw Hill, 1971.
11. Water Treatment Plant Design, American Water Works Association, 6666
W. Quincey Avenue, Denver, Colorado 80235.
12. G. L. Culp, R. L. Culp, New Concepts in Water Purification, Van
Nostrand Reinhold Company, New York, 1974.
13. CRC Handbook of Environmental Control, Vol. Ill, Water Supply and
Treatment, CRC Press, Cleveland, 1973.
14. Manual of Instruction for Water Treatment Plant Operators, Health
Education Service, PO Box 7283, Albany, NY 12224, 1965.
15. S. P. Hansen, R. C. Gumerman, R. L. Culp, Estimating Water Treatment
Costs, Vol. Ill, Cost Curves Applicable to 2500 gpd to 1 mgd Treatment
Plants, U.S. EPA, Municipal Environmental Research Laboratory,
Cincinnati, Ohio 45268, August, 1969.
16. G. J. Venema, "In-line Filtration May Be Just For You," Water and
Wastes Engineering, May 1975, pp. 50-57.
-------
17. G. S. Logsdon, R. M. Clark, C. H. Tate, "Direct Filtration Treatment
Plants: Costs and Capabilities," Journal AWWA, March 1980, pp.
134-147.
18. G. P. Westerhoff, A. F. Hess, M. J. Barnes, "Plant Scale Comparison of
Direct Filtration vs. Conventional Treatment of Lake Erie Water,"
Journal AWWA, March 1980, pp. 148-154.
19. R. L. Culp, "Direct Filtration," Journal AWWA, July 1977, pp.
375-378.
20. Disposal of Wastes From Water Treatment Plants, AWWA Research
Foundation, 1969.
21. "Diatomite Filters for Municipal Use," Task Group Report, American
Water Works Association, Journal AWWA, Vol. 57, No. 2, February
1965.
22. "Diatomite Filter Equipment Evaluation and Design Guide Lines," AWWA
Committee No. 7110P on Diatomite Filtration Report, American Water
Works Association, 6666 W. Quincey Avenue, Denver, Colorado 80235.
23. Neptune Microfloc, Inc., Corvallis, Oregon.
24. Permutit Co., Paramus, NJ.
25. R. M. Willis," Tubular Settlers - A Technical Review, Journal AWWA.
June 1978, pp. 331-335.
26. Water Utility Financing Study, Vol. I; National Costs of the Interim
Primary Drinking Water Regulations, U. S. EPA, Office of Drinking
Water, Washington, DC, 1980.
27. Water Treatment Plant Operation-A Field Study Training Program,
California State University, (CSUS), 6000 J. St., Sacramento, CA 95819
-------
APPENDIX A
ABBREVIATIONS AND SYMBOLS
ft — foot
sq.ft.
—
square foot
cu .ft.
—
cubic foot
ga 1
—
ga1Ion
gpd
—
gallons per day
gpd/sq.ft.
—
gallons per day per square foot
gpm
—
gallons per minute
hr
—
hours
kw-hr
—
killowatt-hour
1
—
liter
lb
—
pound
1pm/sq.m.
—
liters per minute per square meter
lpd
—
liters per day
lpd/cu.m.
—
liters per day per cubic meter
lps
—
liters per second
mm
—
millimeter
cm
—
centimeter
m
—
meter
sq .m.
—
square meter
cu ,m.
—
cubic meter
cu.m./d
—
cubic meters per day
cu.m./s
—
cubic meters per second
mg/1
—
milligrams per liter
mgd
—
million gallons per day
min
—
minutes
psi
—
pounds per square inch
tu
—
turbidity unit
cu .yd.
—
cubic yard
yr
—
year
METRIC-ENGLISH CONVERSION FACTORS
English Unit
Multiplier
Metric Ui
sq.ft.
0.0929
sq
cu,ft.
0.028
cu .in.
cu.yd.
0.75
cu .m.
in
2.53
cm
ft
0.3048
m
gal
3.785
i
gal
0.003785
cu ,m.
gpd
0.003785
cu,m./d
gpm
0.0631
1/s
gpm/sq.ft.
40.74
1pm/sq .m
gpd/sq.ft.
40.74
lpd/sq .m
mgd
0.0438
cu.m./s
-------
APPENDIX B 5
SAMPLE TURBIDITY METER SPECIFICATION
-------
DETAILED SPECIFICATIONS
for the
NEPHELOMETRIC TURBIDIMETER
The following specifications will help you select your
turbidimeter:
The turbidimeter shall consist of a nephelometer, with
a light source for illuminating the sample, and one or
more photoelectric detectors, with a readout device to
indicate the intensity of light scattered at right angles to
the path of the incident light. The turbidimeter shall be
so designed that little stray light reaches the detector in
the absence of turbidity and shall be free from signifi-
cant drift after a short warm-up period.
The sensitivity of the instrument should permit detec-
tion of turbidity differences of 0.02 unit or less in waters
having turbidities less than 1 unit. The instrument
should measure from 0 to 40 units turbidity. Several
ranges will be necessary to obtain both adequate
coverage and sufficient sensitivity for low turbidities.
The sample tubes to be used with the available instru-
ment must be of clear, colorless glass. They should be
kept very clean, both inside and out, and discarded
when they become scratched or etched. They must not
be handled at all where the light strikes them, but
should be provided with sufficient extra length or with a
protective case for handling.
Differences in physical design of turbidimeters will
cause differences in measured values of turbidity even
though the same suspension is used for calibration. To
minimize such differences, the following design criteria
should be observed:
• Light source: Tungsten lamp, operated at not less
than 85 per cent of rated voltage or more than
rated voltage
• Light path: Distance traversed by incident and
scattered light within the sample tube not to
exceed 10 cm total
• Detector light-acceptance angle: Centered at 90
degrees to the incident light path and not to exceed
± 30 degrees from center.
• Maximum turbidity to be measured: 40 units.
The Hach turbidimeter, models 2100 and 2100-A, and
the H. F. instruments DRT-100 have been found
acceptable; other instruments meeting the above design
criteria also are acceptable.
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APPENDIX C
JAR TEST PROCEDURE
(Courtesy, Phipps & Bird, Inc.)
-------
COAGULATION TEST
Every rapid sand filter plant should be equipped with apparatus for conducting coagulation tests,
commonly called "jar tests." In its simplest form, the only apparatus required to perform this test
is a series of six glass jars, stirring rod, pipettes, pH test equipment, and standard solutions of
coagulant and alkali (or acid). The jars may either be 1 qt. or 1 gal. capacity; the latter are
preferred. Although hand stirring is quite satisfactory for an occasional test, a mechanical stirring
device is far more satisfactory and gives better results. In carrying out the test, the jars are filled
with freshly drawn water and solution [and the alkali (acid) solution if necessary] beginning with a
small dose in the first jar and increasing throughout the series. The chemicals are added rapidly
and the treated water is stirred vigorously for 3 min. and slowly for 15 min. and is then allowed to
subside quietly for 3 hr. or more.
The quantities of the chemicals applied are chosen in accordance with the results of the preliminary
physical and chemical tests and the experience of the operator in the coagulation of water. In the
absence of such experience, the test will have to be repeated and numerous doses and combinations
of doses used until the minimum dosage can be determined with which satisfactory coagulation can
be secured. In judging coagulation the following criteria should be used:
1. The first appearance of floe.
2. The appearance of floe in (a) 5 min., (b) 30 min.
3. The appearance of the supernatant liquid and the settleability of the floe at the end of a period
of time corresponding to the retention period of the plant sedimentation basin.
4. The effect of filtration may be ascertained by filtering a portion of water from each jar through
plugs of absorbent cotton and determining the color and turbidity of the filtrate.
In conducting the jar test, it is important that the temperature of the water in the jars be
maintained at approximately the same temperature as when the samples were taken. A pH
determination on the water in each jar must be made 5 min. after the preliminary mixing is
completed. All observations made during the test should be recorded on a sheet similar to the
example given below.
From this information, it is apparent that a dosage of 1.0 gpg of alum, without the addition of alkali,
is close to the optimum for this particular sample of water and that a pH of 6.4 should be maintained
on the water in the mixing chamber. On a plant scale a dosage of 0.9 gpg at a pH 6.6 should give
good results. This is a simple example; in ordinary practice, numerous conditions will occur that re-
quire several trials before the optimum is secured. It often happens that the amount of coagulant re-
quired to produce the optimum pH of coagulation is far in excess of that necessary completely to
clarify. In this case the only value of the excess alum is its acidity, and the alum is wasted. It is possi-
ble to treat such waters successfully and economically with a combination of alum and sulphuric
acid, and jar tests are made with standard solutions of these chemicals in the same manner as
described above. Naturally a process involving the use of sulphuric acid has numerous disadvan-
tages and requires careful chemical control.
TEST EXAMPLE
Raw Water at 7 a.m.
Color
Turbidity
Temperature
. . .10
. . .50
,6tf F
Date
Alkalinity
pH
Free C02.
.45
7.0
. .9
-------
JAR TEST EXAMPLE
Jar
No.
Alum
added
g-pg-
Lime
added
p.p.m.
First
Floe
5 min.
30 min.
5 hr.
pH
1
0.5
0
None

6.9
2
0.6
0
10 min.
Smoky
Smoky
Smoky
6.9
3
0.7
0
5 min.
Fair
Fair
Fair
6.8
4
0.8
0
2 min.
Fair
Good
Good
6.7
5
0.9
0
1 min.
Good
Good
Excellent
6.6
6
1.0
0
1 min.
Excellent
Excellent
Excellent
6.4
In the case of those waters for which excessive quantities of alum or the use of acid is required to
reach the optimum, ferric compounds have a useful field, for they can be coagulated either in a low
or a high pH range. Because alum can be used only in a low pH range—usually less than7.0—it is
apparent that the filtered water will be corrosive and that this condition will have to be corrected
following filtration. Iron coagulation at high^pH prior to filtration can be designed to correct for
corrosion so that no further adjustment of the filtered-water reaction is necessary. In cases where
the raw water contains undesirable amounts-of iron or manganese or both, the iron-coagulation
process is plainly indicated.
When the chemical doses that are most effective for a given raw-water condition have been
determined in the laboratory, it is up to the operator to adjust the chemical feeds until the best floe
is obtained, using the pH results obtained from the jar tests as a guide. The ability to tell whether
the dosage is satisfactory or not is largely a matter of experience, but the following suggestions will
be helpful to the novice:
1. The quality of the floe in the mixing chambers and the sedimentation basins, as weli as the
appearance of the filter influent, should be observed hourly by the operator. A submerged
waterproof light is useful for this.
2. With rapidly fluctuating raw waters or those in which good coagulation is difficult to maintain, a
quart jar of water from the mixing chamber should be taken every hour, the pH recorded, and
the jars preserved in a row upon a table until eight have been collected. These samples form a
continuous historical record of the coagulation process and serve to prove to each successive shift
operator and the superintendent that the operator responsible for them has performed his duty
faithfully and well.
3. In a well-coagulated water, the particles of floe are distinct and well formed, and the water
should show numerous clear spots between the particles. After 5 or 10 min. settling in a jar,
particles of floe at the center of the jar should be clearly visible when viewed sidewise through
the liquid.
4. A cloudy or smoky appearance of the treated water indicates incorrect dosage.
As the experience of the operator increases, he will require fewer jar tests. He will learn to recognize
recurring conditions and handle them from past experience. Careful records of previous operations
and graphs relating to turbidity and color and to coagulant requirements under different conditions
of temperature 3nd alkalinity are very valuable. As has been stated earlier, the coagulation process
is the heart of the rapid sand process. Failure to give constant attention results in a poor product,
filter deterioration, waste of chemicals and thoroughly unsatisfactory conditions.
-------
APPENDIX D
PREVENTIVE MAINTENANCE FOR AQUARIUS A SERIES COMPLETE TREATMENT PLANT
(Courtesy, Neptune Microfloc Corporation)
-------
PUNT MAINTENANCE
GENERAL
Procedures for plant maintenance may vary from plant to plant, but good house-
keeping rules should apply anywhere. The following are some general
suggestions:
Oust from chemicals should b$ cleaned up at once and not allowed to build up
on floors, pumps, valves, instruments, etc.
CAUTION: Alum in solution with water lowers the pH, that is, acid conditions
are formed. Alun dust combined with a little moisture can become quite
corrosive to equipment, metals, and finishes and should be cleaned up and
wiped or washed off at once.
WARNING: POLYELECTROLYTE MIXED WITH A LITTLE WATER OR MOISTURE FORMS A VERY
SLIPPERY FILM. SPILLED CHEMICAL SHOULD BE CLEANED UP AT ONCE AND THE FL"TOR~
CLEANED AND DRIED IF CHEMICAL WAS WETTED IN ANY WAY. THE FLOOR SHOULD BE
CHECKED AND SANO OR OTHER MATERIAL TO PREVENT SLIPPING INJURIES SHOULD BE
SPREAD TEMPORARILY.
Chemical storage areas should be kept as clean as possible to prevent chemical
dust from creating health or maintenance problems.
WARNING: THE CHEMICALS USED IN WATER TREATMENT REQUIRE SOME. PRECAUTIONS FOR
STORAGE AND HANDLING. PRODUCT SAFETY INFORMATION FOR CHEMICALS IS INCLUDED AT
THE END OF THE INSTRUCTION SECTION OF THIS OWNER'S MANUAL.
Moisture should not be allowed to accumulate on electrical equipment or
devices.
Electrical equipment should not be subjected to direct water hose pressure and
indirect splashing should be minimized during plant wash-down and clean up.
Water should not be allowed to stand on floors or accumulate anywhere.
WARNING: ONLY QUALIFIED PERSONNEL SHOULD WORK ON ELECTRICAL EQUIPMENT.
A regular schedule of cleanup and maintenance should be planned and followed
to insure long equipment life and promote trouble-free plant operation.
A plant operation and maintenance log should be set up and filled out on a
regular basis..
The following suggested procedures should be included in your maintenance
schedule but are not meant to be the complete schedule.
CAUTION: The maintenance schedule should include all recommendations in the
equipment manufacturer's instructions included in the Equipment Data section
of the Manual.
-------
PLANT MAINTENANCE
GENERAL
Procedures for plant maintenance may vary from plant to plant, but good house-
keeping rules should apply anywhere. The following are some general
suggestions:
Dust from chemicals should be cleaned up at once and not allowed to build up
on floors, pumps, valves, instruments, etc.
CAUTION: Alum in solution wlth water lowers the pH, that Is, acid conditions
are formed. Alim dust combined with a little moisture can become quite
corrosive to equipment, metals, and finishes and should be cleaned up and
wiped or washed off at once.
WARNING: POLYELECTROLYTE MIXED WITH A LITTLE WATER OR MOISTURE FORMS A VERY
SLIPPERY FILM. SPILLED CHEMICAL SHOULD BE CLEANED UP AT ONCE AND THE FLUB*"
CLEANED AND DRIED IF CHEMICAL WAS WETTED IN ANY WAY. THE FLOOR SHOULD BE
CHECKED AND SAND OR OTHER MATERIAL TO PREVENT SLIPPING INJURIES SHOULD BE
SPREAD TEMPORARILY.
Chemical storage areas should be kept as clean as possible to prevent chemical
dust from creating health or maintenance problems.
WARNING: THE CHEMICALS USED IN WATER TREATMENT REQUIRE SOME. PRECAUTIONS FOR
STORAGE AND HANDLING. PROOUCT SAFETY INFORMATION FOR CHEMICALS IS INCLUDED AT
THE END OF THE" INSTRUCTION SECTION OF THIS OWNER'S MANUAL.
Moisture should not be allowed to accumulate on electrical equipment or
devices.
Electrical equipment should not be subjected to direct water hose pressure and
indirect splashing should be minimized during plant wash-down and clean up.
Water should not be allowed to stand on floors or accumulate anywhere.
WARNING: ONLY QUALIFIED PERSONNEL SHOULD WORK ON ELECTRICAL EQUIPMENT.
A regular schedule of cleanup and maintenance should be planned and followed
to insure long equipment life and promote trouble-free plant operation.
A plant operation and maintenance log should be set up and filled out on a
regular basis.
The following suggested procedures should be included in your maintenance
schedule but are not meant to be the complete schedule.
CAUTION: The maintenance schedule should Include all recommendations in the
equipment manufacturer's instructions included in the Equipment Data section
of the Manual.
-------
DAILY
1. Check chemical feeders for correct operation and calibration. Suction
lines must be free of air. Strainers should be clear of sediment. Feed
lines and connections should be free of leaks.
2. Check and maintain an adequate supply of chemical solution 1n the
chemical feed tanks.
NOTE: Chemical feed charts and mixing Instructions are included at the end of
the Instruction Section of the Manual.
CAUTION: Remember chemical treatment is the most important step in water
treatment. Without chemicals, essentially untreated raw water goes into your
finished water storage.
3. Make a general Inspection of the entire plant observing operation and
condition of all equipment.
4. Drain accumulated moisture from any non-automatic condensate traps in the
air lines.
5. Check and record water quality (turbidity, pH, chlorine, color, etc.) and
note any operational problems. Record chemical dosages including any
changes in feed rate and the reasons and results of same.
NOTE: Records of operating condition changes are valuable to anticipate and
make adjustments 1n your operation for changes in the raw water
characteristics because of seasonal changes or due to storms. A sample Weekly
Operating Report log sheet is included with these instructions.
WEEKLY
1. Check the function and adjustment of all of the plant equipment according
to the manufacturer's recommendations and the Operation Instruction
section of this Manual. Manufacturer's Instructions are in the Equipment
Data section of this Manual and maintenance recommendations should be
Included 1n your log.
2. Check oil levels In the chemical feed pumps and in the flocculator drive
gearbox. The recommended oil specifications are in the manufacturer's
instructions 1n the Equipment Data section.
3. Plant flow rate and especially the splitting of the raw water flow, one
half the flow to each section of the plant, should be observed at least
once a week. If you do not have raw water flow instrumentation, an
Indication of the flow splitting would be by the valve disc position
indicator on the two effluent valves. Valve discs should be open the
same and the out-put gauges on the level controllers should read about
the same pressure with clean filters after a backwash of both filters.
4. This would be a good time to get the filters clean and, at the same time,
observe the complete backwash cycle. The cycle can be initiated with the
"Automatic Backwash Manual Initiate" switch on the plant controller.
-------
Check the functioning and speed of opening of the waste valve. The water
level in the tube clarifier should drop at about two feet per minute.
Check the speed of opening of the backwash valve.
NOTE: Refer to the Equipment Adjustment for Backwashing and Backwash Cycle in
the Operation and Maintenance section of the Manual for the complete descrip-
tion of adjustments that should be checked.
5. Inspect the filter media surface and the tubes in the tube clarifier.
Agitate the media with a rake if there appears to be an accumulation of
floe that was not washed out during the backwash cycle. The media should
be clean after the next cycle. Re-agitate if 1t is not. A clean filter
will run longer between backwash cycles and should save finished water.
Wash any accumulation of sludge from the tube modules with a Tow pressure
hose.
CAUTION: Do not use a high pressure fire hose to wash out the filter or to
clean the tube modules.
The NMI Technical Director will demonstrate these cleaning procedures
during plant startup.
6. Check the coagulant feed rate and floe formation in the two flocculator
compartments.
Raw water conditions may change and you may want to run some jar tests to
check the effectiveness of the alum feed rate and make some
adjustments. Settling tests of the floe coming out of the flocculator
can help judge the effectiveness of any changes. RECORD any CHANGES in
CHEMICAL FEED and the raw water conditions, season, storm conditions,
etc., at the time of the change. These records can help you make
adjustments to your plant for similar conditions in the future without
having to redo the jar tests.
NOTE: The Chemical Treatment and Coagulation, Mechanically Powered Floccu-
lation, and Chemical Feed sections of the Operation and Maintenance
instructions have guides to checking coagulant feed rate.
MONTHLY
I. Drain chemical mixing tanks and clean out any chemical sludge in the
bottom of the tanks.
Check chemical feed pumps, lines, check valves, and strainers for any
accumulation of chemical residue. Clean or flush the pumps according to
the manufacturer's recommendations.
NOTE: Chemical feed pump manufacturer's maintenance instructions are in the
Equipment Data section of the Manual.
-------
2. Observe and check the functioning of all automatic valves. Follow any
manufacturer's recommendations for maintenance of actuators and
positioners.
CAUTION: Lack of maintenance of air lines, filters and compressor/dryer cause
most valve actuator problems. D1rt or moisture in the compressed air supply
are the most frequent cause of automatic valve malfunction.
3. Check the functioning of the level controller in the filter compart-
ment. The water level should be at about the middle hole in the
controller mounting bracket. Check the functioning of the limit
switches.
NOTE: Level controller adjustment is covered in the Plant Operation section
of the Manual under Equipment Adjustment for Filtering, Backwashing.
4. Observe and check the headloss switch adjustment. The switch should
start a backwash cycle automatically when the headloss gauge reads 7-8
feet of water headloss.
5. All pumps should be checked for leaks at the seals and for overall
function. Motor bearings should not be noisy.
6. Flocculator drive motor should not have noisy bearings. Brushes should
be checked for remaining wear life.
7. Filter agitators should rotate freely by hand and rotate automatically
during the backwash cycle.
8. Adjust or repair anything found in the equipment checks according to the
manufacturer's recommendations.
9. Review records of the months operation. A brief summary with comments on
unusual operational conditions or problems can be valuable and save you
time when simillar conditions occur in the future.
10. The overall plant should give the appearance of good housekeeping. It is
easier to keep 1t clean than 1t 1s to clean it up later.
YEARLY
1. Drain each section of the plant separately. One section can stay on-
line.
2. Clean out any accumulatin of sludge in the flocculator and tube clarifier
compartments.
3. Check the flocculator rotors for broken or misaligned paddles. Check the
bearings.
4. Check the settling tube modules for tube pagesses that may be plugged
with sludge. Check for damage to the tube modules.
-------