# 4. Approach for Compliance 

## Compliance Approach for Turbidity Requirements

While many systems already meet or will meet turbidity requirements
prior to compliance deadlines, some systems will need to evaluate their
treatment plants to determine what changes, if any, are needed to comply
with the requirements. Utilities which determine they may have
difficulty complying with the turbidity requirements of the IESWTR
should first evaluate the system and begin to optimize plant
performance. Section 4.2 outlines the Agency's suggested approach for
utilities to evaluate their systems, and identifies key areas which
systems should evaluate.

Although it is anticipated that compliance with the IESWTR will
generally be possible through adjustments to existing treatment
processes, additional treatment processes or other treatment
technologies or enhancements may be required in some cases. It is not
anticipated that systems will need to make major capital improvements,
but those systems considering capital improvements in order to meet
requirements of the IESWTR should conduct an optimization activity
similar to the Composite Correction Program to assess the real need of
construction. Section 4.3 briefly outlines many of the process
enhancements that, in the opinion of the Agency and other water
professionals, are the most likely to be employed by systems, if
optimization alone does not permit a system to comply with turbidity
requirements.

## System Evaluation & Plant Optimization

A thorough treatment plant evaluation and improvement program is the
best way to ensure pathogen-free drinking water. With an emphasis on
improved performance at minimal cost, optimization is an economical
alternative for compliance with the turbidity requirements. Currently,
two programs serve as excellent resources for systems wishing to follow
a systematic and proven approach to optimizing water treatment plant
performance. These are:

-   Composite Correction Program

The Composite Correction Program (CCP) is a systematic action oriented
approach that federal or state regulators, consultants, or utility
personnel can implement to improve performance of existing water
treatment plants. The Comprehensive Performance Evaluation phase of the
CCP is described in greater detail in Chapter 6. The Agency has
developed a guidance manual that may be obtained by calling the EPA Safe
Drinking Water Hotline at

1-800-426-4791.

-   ![](media/image1.png){width="2.279861111111111in"
    height="2.475in"}Partnership for Safe Water

The Partnership is a voluntary cooperative effort between the EPA, AWWA
and other drinking water organizations, and over 186 surface water
utilities representing 245 water treatment plants throughout the United
States. The goal of this common sense cooperation is to provide a new
measure of safety to millions of Americans by implementing prevention
programs where legislation or regulation does not exist. The
preventative measures are based around optimizing treatment plant
performance and thus increasing protection against microbial
contamination in America\'s drinking water supply. Information regarding
the Partnership is found at AWWA's website
<http://www.awwa.org/partner1.htm> or may be obtained by calling (303)
347-6169.

Systems are strongly encouraged to utilize one of the above noted
programs if intending to optimize plant performance.

While systems should consider the above noted programs, this section
provides information utilities may find useful in evaluating their
system and optimizing their plant's performance. It is important to
remember that the items listed in this chapter may or may not apply to
all systems. Optimizing water treatment plants is a site-specific
endeavor. As such, this section does not seek to serve as a recipe for
how to optimize water treatment for lowered turbidity. It does however
highlight the areas which, in the experience of the Agency and other
water professionals, most often can be improved to optimize water
treatment at PWSs. The items discussed in this section are addressed in
greater detail in the Composite Correction Program and the Partnership
for Safe Water.

### Coagulation/Rapid Mixing

Coagulation is the process by which small particles are combined to form
larger aggregates and is an essential component in water treatment
operations. Evaluation and optimization of the Coagulation/Rapid Mixing
step of the water treatment process includes a variety of aspects.
Optimal coagulant dosages are critical to filter performance.
Maintaining the proper control of these chemicals can mean the
difference between an optimized surface plant and a poorly run surface
plant. Inadequate mixing of chemicals or their addition at inappropriate
points within the treatment plant can limit performance. The following
issues may be evaluated as they may improve the performance of this step
in the treatment process.

#### Chemicals

An evaluation of the chemicals used in the treatment process can
identify the appropriateness of the coagulation chemicals being used. A
thorough understanding of coagulation chemistry is necessary, and
changes to coagulation chemicals should not be made without careful
consideration. The following aspects relating to coagulation chemicals
may be considered by systems:

-   Operating procedures should not call for the shutting off of
    coagulant chemical addition when raw water is less than 1 NTU.

-   Are chemicals being dosed properly, paying special attention to pH?
    Is dose selection based on frequent jar testing or other testing
    methods such as streaming current monitoring, zeta potential, or
    pilot filters? Relying exclusively on past practice is not good
    practice.

-   Do Standard Operating Procedures exist for coagulation controls?
    Systems should develop SOPs, and establish a testing method that is
    suited to the plant and personnel.

-   Are the correct chemicals being utilized? Is the best coagulant
    being used for the situation? Changing coagulant chemicals or adding
    coagulant aids may improve the settleability of the flocculated
    water and in turn optimize performance. Coagulants may also be
    changed seasonally.

-   Do operators have the ability to respond to varying water quality by
    adjusting coagulation controls to ensure optimum performance?
    Systems should provide operators with such learning opportunities so
    that they can react to various conditions with understanding and
    confidence.

-   Are solutions used promptly? Most solutions should be utilized
    within 48 hours of their formulation. Are chemicals utilized before
    manufacturer recommended expiration or use-by dates?

-   Is pH a consideration? Measurement of pH is a key aspect in
    coagulation chemistry. Do not dilute coagulant solutions to pH
    levels higher than 3.3 for alum and 2.2 for iron salts.
    Manufacturers instructions should be followed when diluting
    polymers.

-   Are chemicals being added in the correct order? The order of
    chemicals is very important, as certain chemicals interfere with
    others. Jar tests should be utilized to develop optimal sequences.

-   Is the chemical feed system operating properly? Operators should
    consider checking the accuracy of systems at least once daily or
    once per shift.

#### Feed Systems

Feed systems are another important aspect of the coagulation step in
typical treatment processes. These systems are responsible for
delivering coagulants into the system at rates necessary for optimal
performance. The following aspects should be evaluated regarding feed
systems.

-   Is redundancy a consideration? Redundancy may be built into the feed
    systems so that proper feeding of chemicals can be maintained in the
    event of failure or malfunction of primary systems.

-   Is the feed system large enough? Feed systems should be sized so
    that chemical dosages can be changed to meet varying conditions.

-   Are chemical pumping equipment and piping checked on a regular
    basis? Maintenance of these systems should be a priority and
    incorporated into routine maintenance performed at the system.

-   Is a diaphragm pump utilized? A continuous pump allows coagulants to
    be added in such a way as to avoid pulsed flow patterns.

#### Satisfactory Dispersal/Application Points

Finally, proper coagulation and mixing also depends on satisfactory
dispersal of coagulation chemicals and appropriate application points.
Coagulants should be adequately dispersed so that optimal coagulation
may occur. A sufficient number of feed points should exist such that
chemicals have the opportunity to mix completely. Utilities should
evaluate the following items:

-   Is adequate dispersion taking place? If chemicals are added at a
    hydraulic pump, ensure that the chemicals are distributed across the
    width of the flow stream and at the location where turbulence is
    greatest. The rapidity of coagulation necessitates even dispersal as
    soon as possible.

-   Are coagulants being added at the proper points? Metal salts should
    be introduced at the point of maximum energy input. Low molecular
    weight cationic polymers can be fed with metal salts at the rapid
    mix or to second stage mixing following the metal salt. High
    molecular weight nonionic/anionic floc/filter aids should be
    introduced to the process stream at a point of gentle mixing.

-   Is rapid mixing equipment checked frequently? Systems should check
    the condition of equipment, and ensure that baffling provides for
    adequate, even-flow.

### Flocculation

Flocculation is the next step in most treatment plants (in-line
filtration plants being the exception). It is a time-dependent process
that directly affects clarification efficiency by providing multiple
opportunities for particles suspended in water to collide through gentle
and prolonged agitation. The process takes place in a basin equipped
with a mixer that provides agitation. This agitation should be thorough
enough to encourage interparticle contact but gentle enough to prevent
disintegration of existing flocculated particles. Effective flocculation
is important for the successful operation of the sedimentation process.
Several issues regarding flocculation should be evaluated by utilities
to ensure optimal operation of flocculation basins.

#### Flocculation Mixing and Time

Proper flocculation requires long, gentle mixing. Mixing energy should
be high enough to bring coagulated particles constantly into contact
with each other, but not so high as to break up those particles already
flocculated. Utilities should consider evaluating:

-   How many stages are present in the flocculation system? Three to
    four are appropriate to create plug flow conditions and allow
    desired floc formation.

-   Is the mixing adequate to form desired floc particles? Tapered
    mixing is most appropriate. "G" values should be variable through
    the various stages from 70 sec^-1^ to 15 sec^-1^.

-   Are mechanical mixers functioning properly? Are flocculator paddles
    rotating at the correct rates?

-   If flow is split between two flocculators, are they mixing at the
    same speed and "G" value? If the flocculators have different
    characteristics, dosages may be proper for one, but not both.

#### Flocculator Inlets and Outlets

If water passes through the flocculation basin in much less time than
the volumetric residence time, the influent stream has short circuited.
Inlet and outlet turbulence is oftentimes the major source of
destructive energy in flocculation basins that contributes to short
circuiting. Utilities should evaluate the following:

-   Do basin outlet conditions prevent the breakup of formed floc
    particles? Basin outlets should avoid floc breakup. Port velocities
    should be \<0.5 fps. The velocity gradient at any point from the
    flocculation basin to the sedimentation basin should be less than
    the velocity gradient in the last flocculation stage.

-   Do inlet conditions prevent the breakup of formed floc particles?
    Inlet diffusers improve the uniformity of the distribution of
    incoming water. Secondary entry baffles across inlets to basins
    impart headloss for uniform water entry.

-   What size are the conduits between the rapid mix basin and the
    flocculation basin? Larger connecting conduits help reduce
    turbulence which can upset floc.

#### Flocculator Basin Circulation

Baffles are used in flocculator basins to direct the movement of water
through the basin. Baffling near the basin inlet and outlets improves
basin circulation and achieves more uniform circulation. A system may
think about the following items when evaluating flocculation.

-   Is current baffling adequate? Can baffling be added to improve
    performance or does existing baffling require repair? Serpentine
    baffling is better than over/under. Baffling should allow headloss
    through opening to prevent short-circuiting and to allow plug flow
    conditions.

-   Induced velocity in floc chambers should vary from 2 fps in first
    stage to 0.25 fps in the last stage. Velocity through openings in
    the baffle should be slightly less than the induced velocities.

### Sedimentation

Sedimentation is the next step in conventional filtration plants (direct
filtration plants omit this step). The purpose of sedimentation is to
enhance the filtration process by removing particulates. Sedimentation
requires that water flow through the basin at a slow enough velocity to
permit particles to settle to the bottom before the water exits the
basin. Utilities should consider the following items when evaluating
sedimentation basins.

-   Is sludge collection and removal adequate? Inadequate sludge
    collection and removal can cause particles to become re-suspended in
    water or upset circulation. Systems should disrupt the sludge
    blanket as little as possible. Sludge draw-off rates can effect the
    sludge blanket. Sludge draw off procedures should be checked
    periodically, making sure sludge levels are low; and sludge should
    be wasted if necessary. Sludge pumping lines should be inspected
    routinely to ensure that they are not becoming plugged. These lines
    should also be flushed occasionally to prevent the buildup of
    solids.

-   Do basin outlet conditions prevent the breakup of formed floc
    particles? Settling basin inlets are often responsible for creating
    turbulence that can break up floc. Improperly designed outlets are
    also often responsible for the break-up of floc. Finger launders
    (small troughs with V--notch weir openings that collect water
    uniformly over a large area of the basin) can be used to decrease
    the chance of short-circuiting.

-   Is the floc the correct size and density? Poorly formed floc is
    characterized by small or loosely held particles that do not settle
    properly and are carried out of the settling basin. This is the
    result of inadequate rapid mixing, improper coagulant dosages, or
    improper flocculation. Systems should look to previous steps in the
    treatment train to solve this problem.

-   Is the basin subject to short circuiting? If the basin is not
    properly designed, water bypasses the normal flow path through the
    basin and reaches the outlet in less time than the normal detention
    time. The major cause of short-circuiting is poor influent baffling.
    If the influent enters the basin and hits a solid baffle, strong
    currents will result. A perforated baffle can successfully
    distribute inlet water without causing strong currents. Tube or
    plate settlers also improve efficiency, especially if flows have
    increased beyond original design conditions. Tube settlers can
    result in twice the basin's original settling capacity.

-   Are basins located outside and subject to windy conditions? Wind can
    create currents in open basins that can cause short-circuiting or
    disturbances to the floc. If wind poses a problem, barriers lessen
    the effect and keep debris out of the unit.

-   Are basins subject to algal growth? A problem that occurs in open,
    outdoor basins is the growth of algae and slime on the basin walls.

-   In solids contact clarifiers, is the sludge blanket maintained
    properly? Operators should be able to measure the sludge depth and
    percent solids to ensure the sludge blanket is within the
    manufacturer's recommendations.

### Filtration

Filtration is the last step in the particle removal process. Improperly
designed, operated, or maintained filters can contribute to poor water
quality and sub-optimal performance. There are a host of items which
systems will need to evaluate regarding filters that may be contributing
to poor performance. Many of the items listed below are detailed in
Chapter 5, Individual Filter Self-Assessment.

#### Design of Filter Beds

It is important to verify that the filters are constructed and
maintained according to design specifications. Utilities should consider
the following items when evaluating the design of filter beds.

-   Media -- Is the correct media being used? Issues such as size,
    uniformity coefficient, and depth need to be evaluated.

-   Underdrains -- Are underdrains adequate or have they been damaged or
    disturbed?

#### Filter Rate and Rate Control

The rate of filtration and rate control is another important aspect of
filters that should be evaluated. Without proper control, surges may
occur which would force suspended particles through the filter media.

-   Are surges in flow an issue of concern? Systems should avoid sudden
    changes to filter rate. Systems should minimize plant flow rate
    changes, throttle filter control valves slowly, and bring a filter
    on-line when one is being backwashed).

-   Is the plant operating at the appropriate flow rate? At some plants
    (typically smaller systems), the flow is operated at a level that
    hydraulically overloads unit processes. Operating at lower flow
    rates over longer periods of time prevents overloading and increases
    plant performance.

-   At what flows are the filters rated? Make sure not to exceed flow
    rates on remaining in-service filters when taking filters off-line
    or out of service for backwash.

#### Filter Backwashing

Filter backwashing has been identified as a critical step in the
filtration process. Many of the operating problems associated with
filters are a result of inadequate backwashing. Utilities should
consider the following items when evaluating filter backwash practices.

-   Is the rate of filter backwash appropriate for the filter? Filters
    can be either underwashed or overwashed. Utilities need to determine
    the appropriate flow that will clean the filter and prevent
    mudballs, but will not upset the filter media to the extent that the
    underdrain is damaged or filter media is lost. (20-50 percent bed
    expansion is typical)

-   Are criteria set for initiating backwash? Systems should establish
    criteria such as time, headloss, turbidity, or particle counts for
    initiating backwash procedures.

-   How are filters brought back on-line? Media should be allowed to
    settle after backwashing before bringing filters back on-line.
    Filters should be brought back on line slowly. Several filters
    should not be brought on line at the same time. Filters should not
    be brought back on-line without backwashing first.

-   When a filter is backwashed, is more water diverted to the remaining
    filters, causing them to be overloaded during backwash? During the
    backwash, flow going to the remaining filters may need to be cut
    back to ensure the filters are not overloaded or "bumped" with a
    hydraulic surge causing particle pass through.

## Process Enhancements/Technologies

As noted at the beginning of this chapter, some systems may need to
provide additional treatment processes or make enhancements to existing
processes to meet the requirements of the IESWTR. **The Agency stresses
that utilities need to first fully evaluate their systems, specifically
utilizing either the CCP or Partnership for Safe Water programs, prior
to installing new treatment or equipment. EPA believes that most systems
will be able to meet requirements through process optimization.**

EPA expects that systems might use a combination of equipment
modifications and process enhancements or treatment processes to meet
requirements if process optimization alone does not bring the system
into compliance. The Agency developed a *Cost and Technology Document
for the Interim Enhanced Surface Water Treatment Rule*, which discusses
these treatment processes/enhancements. Treatment process enhancements
fall into the following categories:

-   Chemical Modifications

-   Coagulant Improvements

-   Rapid Mixing Improvements

-   Flocculation Improvements

-   Settling Improvements

-   Filtration Improvements

-   Hydraulic Improvements

-   Laboratory Modifications

-   Process Control Modifications

By no means is this list exhaustive or do the process enhancements which
fall under each category represent the only modifications available to
systems. They represent enhancements that, in the opinion of the Agency
and other water professionals, are the most likely to be employed by
systems. For further information regarding these enhancements, the
reader is directed to the *Cost and Technology Document for the Interim
Enhanced Surface Water Treatment Rule*, dated July 28, 1998, which was
developed in support of the Regulatory Impact Analysis (RIA) for the
IESWTR.

Certain technologies, especially those involving large financial
expenditures, should only be implemented with appropriate engineering
guidance, and should consider factors such as the quality and type of
source water, turbidity of source water, economies of scale and
potential economic impact on the community being served, and treatment
and waste disposal requirements. An engineering study should be
conducted, if needed, to select a technically feasible and
cost-effective method to meet the unique needs of each system for
improved filter effluent quality to comply with the IESWTR. Some
situations may require more extensive water quality analyses or bench
and/or pilot scale testing. The engineering study may include
preliminary designs and estimated capital, operating and maintenance
costs for full-scale treatment.

## References

1.  AWWA. 1994. "Preventing Waterborne Disease: How to Optimize
    Treatment, Participant Guide." AWWA Satellite teleconference.

2.  Bucklin, K., A. Amirtharajah, and K. Cranston. 1998.
    "Characteristics of Initial Effluent Quality and its implications
    for the Filter to Waste Procedure." AWWARF, Denver, CO.

3.  Logsdon, G. 1987. "Evaluating Treatment Plants for Particle
    Contaminant Removal." *J. AWWA*. 79(9):82-92.

4.  Partnership for Safe Water. 1995. *Voluntary Water Treatment Plant
    Performance Improvement Program Self Assessment Procedures.*
    October.

5.  Huben, H. 1995. *Water Treatment*. Second Edition. AWWA.

6.  USEPA. 1998*. Regulatory Impact Analysis for the Interim Enhanced
    Surface Water Treatment Rule*. Office of Ground Water and Drinking
    Water, Washington, D.C.

7.  USEPA. 1998. *Handbook: Optimizing Water Treatment Plant Performance
    Using the Composite Correction Program*. EPA/625/6-91/027.

8.  USEPA. 1989. Technologies for Upgrading Existing or Designing New
    Drinking Water Treatment Facilities. EPA/625/4-89/023, Center for
    Environmental Research Information, Cincinnati, OH.

4\. Approach for Compliance [1](#approach-for-compliance)

4.1 Compliance Approach for Turbidity Requirements
[1](#compliance-approach-for-turbidity-requirements)

4.2 System Evaluation & Plant Optimization
[1](#system-evaluation-plant-optimization)

4.2.1 Coagulation/Rapid Mixing [2](#coagulationrapid-mixing)

4.2.2 Flocculation [4](#flocculation)

4.2.3 Sedimentation [6](#sedimentation)

4.2.4 Filtration [7](#filtration)

4.3 Process Enhancements/Technologies
[8](#process-enhancementstechnologies)

4.4 References [9](#references)