United States Office of Water EPA 816-R-01-014

Environmental Protection (4606) June 2001

Agency

The Interim Enhanced Surface

Water Treatment Rule

What Does it Mean to You?
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TABLE OF CONTENTS

Definitions and Abbreviations ....................................................... 3

1. Introduction ................................................................. 5

Purpose of the Guide ....................................................... 5

Background .............................................................. 5

Development of the Rule ..................................................... 6

Benefits of the Rule ........................................................ 7

2. Applicability and Compliance Dates ................................................. 7

3. Summary of Requirements ...................................................... 9

Disinfection profiling and benchmarking .......................................... 9

Cryptosporidium ......................................................... 10

Strengthened turbidity requirements ............................................ 10

Individual filter monitoring requirements ......................................... 10

Uncovered finished water storage facilities ....................................... 10

Public water system recordkeeping and reporting requirements ......................... 10

Sanitary surveys ......................................................... 11

Unfiltered Systems ........................................................ 11

4. Additional Information ......................................................... 11

5. Detailed regulatory requirements .................................................. 13

Combined filter effluent turbidity monitoring ...................................... 14

Individual filter turbidity monitoring ............................................ 20

Disinfection profiling and benchmarking ......................................... 24
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Definitions and Abbreviations

Definitions

Comprehensive performance evaluation (CPE) — is a thorough review and analysis of a treatment

plant’s performance-based capabilities and associated administrative, operation and maintenance

practices. It is conducted to identify factors that may be adversely impacting a plant’s capability to

achieve compliance and emphasizes approaches that can be implemented without significant capital

improvements.

Disinfection profile — is a summary of daily Giardia lamblia inactivation through the treatment plant. 

Filter profile — is a graphical representation of individual filter performance, based on continuous

turbidity measurements or total particle counts versus time for an entire filter run, from startup to

backwash inclusively, that includes an assessment of filter performance while another filter is being

backwashed. 

Uncovered finished water storage facility ---- is a tank, reservoir, or other facility used to store water

that will undergo no further treatment except residual disinfection and is open to the atmosphere.

Abbreviations Used in This Document 

CCP: Composite Correction Program

CDC: Centers for Disease Control

CPE: Comprehensive Performance Evaluation

CTA: Comprehensive Technical Assistance

CWS: Community Water System

DBP: Disinfection Byproducts

DBPP: Disinfection Byproducts Precursors 

DBPR: Disinfectants/Disinfection Byproducts Rule

EC: Enhanced Coagulation

EPA: United States Environmental Protection Agency

ES: Enhanced Softening

ESWTR: Enhanced Surface Water Treatment Rule

FACA: Federal Advisory Committee Act

FR: Federal Register

GAC10: Granular activated carbon with ten minute empty bed contact time and 180 day

reactivation frequency

GWR: Ground Water Rule

GWUDI: Ground Water Under the Direct Influence of Surface Water

HAA5: Haloacetic acids (Monochloroacetic, Dichloroacetic, Trichloroacetic,

Monobromoacetic and Dibromoacetic Acids)

hrs: Hours

ICR: Information Collection Rule
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IESWTR: Interim Enhanced Surface Water Treatment Rule

Log Inactivation: Logarithm of (N0/NT)

Log: Logarithm (common, base 10)

LT1ESWTR: Long Term 1 Enhanced Surface Water Treatment Rule

LT2ESWTR: Long Term 2 Enhanced Surface Water Treatment Rule

LTESWTR: Long Term Enhanced Surface Water Treatment Rule

MCL: Maximum Contaminant Level

MCLG: Maximum Contaminant Level Goal

M–DBP: Microbial and Disinfectants/Disinfection Byproducts

MR: Monitoring/Reporting

MRDL: Maximum Residual Disinfectant Level

MRDLG: Maximum Residual Disinfectant Level Goal

NCWS: Non-Community Water System

NSCEP: National Service for Environmental Publications

NTIS: National Technical Information Service

NTNCWS: Non-Transient Non-Community Water System

NTU: Nephelometric Turbidity Unit

PWS: Public Water System

RegNeg.: Regulatory Negotiation

SDWA or “The Act”: Safe Drinking Water Act

SDWIS: Safe Drinking Water Information System

Subpart H: PWS using surface water or ground water under the direct influence of surface

water 

SUVA: Specific Ultraviolet Absorption

SWTR: Surface Water Treatment Rule

TNCWS: Transient Non-Community Water System

TOC: Total Organic Carbon

TTHM: Total Trihalomethanes

x log removal: Reduction to 1 /10x of original concentration
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1. Introduction 

Purpose of the Guide

The purpose of this guide is to detail the regulatory requirements of the Interim Enhanced Surface Water

Treatment Rule (IESWTR). The IESWTR, published in the Federal Register on December 16, 1998 (63

FR 69478; www.epa.gov/OGWDW/mdbp/ieswtrfr.html; 66 FR 3770;

www.epa.gov/safewater/mdbp/iesfr.html; Appendix H—rule language only), is the first part of a series of

rules, the “Microbial-Disinfectants/Disinfection Byproducts Cluster” (M-DBP Cluster), to be published

over the next several years that are intended to control microbial pathogens while minimizing the public

health risks of disinfectants and disinfection byproducts (DBPs). The IESWTR is designed to address the

health risks from microbial contaminants without significantly increasing the potential risks from

chemical contaminants. This rule was published concurrently with the Stage 1 Disinfectants/Disinfection

Byproducts Rule (Stage 1 DBPR), which addresses control of disinfectants and their byproducts.

Background

The 1974 Safe Drinking Water Act (SDWA) called for EPA to regulate drinking water by creating the

national interim primary drinking water regulations (NIPDWR). In 1979, the first interim standard

addressing DBPs was set for total trihalomethanes (TTHMs), a group of four volatile organic chemicals

which form when disinfectants react with natural organic matter in the water. 

Although SDWA was amended slightly in 1977, 1979, and 1980, the most significant changes to the

1974 law occurred when SDWA was reauthorized in 1986. Disease-causing microbial contamination

had not been sufficiently controlled under the original Act. To safeguard public health, the 1986

Amendments required EPA to set health goals, or maximum contaminant level goals (MCLGs) and

maximum contaminant levels (MCLs) for 83 named contaminants. EPA was also required to establish

regulations within certain time frames, require disinfection of all public water supplies, specify filtration

requirements for nearly all water systems that draw their water from surface sources, and develop

additional programs to protect ground water supplies.

In 1989, EPA issued two important National Primary Drinking Water Regulations (NPDWR): The Total

Coliform Rule (TCR) and the Surface Water Treatment Rule (SWTR). The TCR and SWTR provide the

foundation for the M-DBP Cluster and are summarized below.

The TCR covers all public water systems. Since coliforms are easily detected in water, they are used to

indicate a water system’s vulnerability to pathogens in the water. In the TCR, EPA set a MCLG of zero

for total coliforms. EPA also set a MCL for total coliforms. If more than 5.0 percent of the samples

contain coliforms within a month, water system operators must report this violation to the state and the

public. In addition, sanitary surveys are required every five or ten years (depending on the quality of the

source water) for every system that collects fewer than five samples per month (typically systems that

serve less than 4,100 people).

EPA issued the SWTR in response to Congress’ mandate requiring disinfection, and where necessary,

filtration of systems that draw their water from surface sources before distribution. The SWTR applies to

all systems that use surface water or ground water under the direct influence of surface water (GWUDI). 

The rule sets MCLGs for Legionella, Giardia lamblia, and viruses at zero since any exposure to these

contaminants presents some level of health risk. 
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Specifically, the rule requires that a surface water system have sufficient treatment to reduce the source

water concentration of Giardia lamblia and viruses by at least 99.9 percent (3 log) and 99.99 percent (4

log), respectively. A detectable disinfection residual must be maintained throughout the entire

distribution system. For systems that filter, the adequacy of the filtration process is determined by

measuring the turbidity of the treated water since high levels of turbidity often indicate that the filtration

process is not working properly. The goal of the SWTR is to reduce risk to less than one infection per

year per 10,000 people. However, the SWTR does not account for systems with high pathogen

concentrations that, when treated at the levels required under the rule, still may not meet this health goal,

and the rule does not specifically control for the protozoan Cryptosporidium.

In 1990, EPA’s Science Advisory Board, an independent panel of experts established by Congress, cited

drinking water contamination as one of the most important environmental risks and indicated that

disease-causing microbial contaminants (i.e., bacteria, protozoa, and viruses) are probably the greatest

remaining health-risk management challenge for drinking water suppliers. Data from the Centers for

Disease Control (CDC) confirm this concern and indicate that between 1980 and 1994, 379 waterborne

disease outbreaks were reported, with over 500,000 cases of disease. During this period, a number of

agents were implicated as the cause, including protozoa, viruses, bacteria, and several chemicals. Most of

the cases (but not the outbreaks) were associated with surface water, including a single outbreak of

cryptosporidiosis in Milwaukee (over 400,000 cases).

In response to these findings, the SDWA was further amended in 1996 to improve public health

protection by incorporating new data on the adverse health effects of contaminants, the occurrence of

contaminants in public water systems, and the estimated reduction in health risks that would result from

further regulation. The Act also increased scientific research requirements and emphasized cost-benefit

analyses in the regulatory decision process. 

Based on prevailing scientific data, the M-DBP Cluster is intended to control microbial pathogens while

minimizing the public health risk from disinfectants and DBPs. Since multiple threats require multiple

barriers, the IESWTR and Stage 1 DBPR expand on the foundation of the TCR, SWTR, and TTHM

standards to target health risk outliers unaddressed by prior regulations. By targeting these gaps, multiple

threats can be minimized.

The IESWTR builds on the SWTR by adding protection from Cryptosporidium through strengthened

combined filter effluent turbidity performance standards and individual filter turbidity provisions for

filtered systems that serve greater than 10,000 people. For unfiltered systems, Cryptosporidium must be

included in the watershed control requirements. In addition, the IESWTR builds on the TCR by

requiring sanitary surveys for all public water systems using surface water and ground water under the

direct influence of surface water. The IESWTR also requires covers for all new finished water storage

facilities and includes disinfection benchmark provisions to ensure continued levels of microbial

protection while taking the necessary steps to comply with the DBP standards. Collectively, the SWTR

and IESWTR place stringent treatment requirements on systems using surface water as a source.

By building on the foundation set forth by the original SDWA, the quality of drinking water has

improved and public health protection has increased. The IESWTR and Stage 1 DBP Rules are part of a

series of rules designed to expand on the foundation of prior rulemaking efforts. By encompassing

previously unaddressed health risks from microbials and disinfection byproducts, the M-DBP Cluster

continues to maximize drinking water quality and public health protection.
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Development of the Rule

The new rules are a product of 6 years of collaboration among the water supply industry, environmental

and public health groups, and local, state, and federal governments. EPA first launched a rule-making

process in 1992 and convened a Regulatory Negotiation (RegNeg) Advisory Committee under the

Federal Advisory Committees Act (FACA), representing a range of stakeholders affected by possible

regulation. The 1996 SDWA Amendments required EPA to develop rules to balance the risks between

microbial pathogens and disinfection byproducts. 

In 1997, a similar FACA process was implemented with the Microbial-Disinfectants/Disinfection

Byproducts (M-DBP) Advisory Committee. The M-DBP Committee convened to collect, share, and

analyze new information available since 1994, review previous assumptions made during the RegNeg

process, as well as build consensus on the regulatory implications of this new information. Negotiations

resulted in the following three proposals:

C A staged approach to regulation of DBPs (referred to as the Stage 1 and Stage 2 DBPRs)

incorporating Maximum Contaminant Levels (MCLs), Maximum Residual Disinfectant

Levels (MRDLs), and treatment technique requirements;

C A companion Interim Enhanced Surface Water Treatment Rule (IESWTR) designed to

improve control of microbial pathogens and prevent inadvertent reductions in microbial

safety as a result of DBP control efforts; and,

C An Information Collection Rule (ICR) to collect information necessary to reduce many

key uncertainties prior to subsequent negotiations for the Stage 2 DBPR.

Benefits of the Rule

The IESWTR will improve public health by increasing the level of protection from exposure to

Cryptosporidium and other pathogens in drinking water supplies through improvements in filtration at

water systems. According to the risk assessment performed for the Regulatory Impact Analysis, the

IESWTR decreases the likelihood of endemic illness (constant, low-level presence of a disease or

infection) from Cryptosporidium by 110,000 to 463,000 cases annually. Based on these values, the

estimated annual benefits of reducing the illness range from $0.263 billion to $1.240 billion per year.

This calculation is based on a valuation of $2,000 per incidence of cryptosporidiosis prevented. The

IESWTR will also reduce the risk of more severe health impacts on sensitive populations, including the

risk of mortality. Additionally, the IESWTR will reduce the likelihood of outbreaks of cryptosporidiosis

and its associated costs by providing a larger margin of safety against such outbreaks in some systems.

2. Applicability and Compliance Dates

The IESWTR applies to public water systems (PWSs) that use surface water or ground water under the

direct influence of surface water (GWUDI) as a source (also known as subpart H systems) and serve

10,000 or more people. Additionally, it establishes a schedule by which states are required to conduct

sanitary surveys for all subpart H systems.

Subpart H systems serving at least 10,000 people must comply with the turbidity and monitoring

requirements, the primary requirements of the IESWTR, no later than January 1, 2002. However, PWSs

with elevated levels of DBPs (total trihalomethanes—TTHM; and five haloacetic acids—HAA5) are
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required to develop an evaluation of their existing disinfection practices—a disinfection profile—no later

than April 2001. 

The timetable for the IESWTR is presented in Table 1. The compliance dates for the associated Stage 1

Disinfectants/Disinfection Byproducts Rule (Stage 1 DBPR) are January 2002 and January 2004. Subpart

H systems that serve 10,000 or more people will have to comply with the provisions of the Stage 1 DBPR

by January 2002. Subpart H systems that serve fewer than 10,000 people and all ground water systems

will have to comply with the provisions of the rule by January 2004. The rules to provide additional

microbial protection for small subpart H systems (Long Term 1 ESWTR) and ground water systems

(Ground Water Rule) are scheduled to be finalized in Spring/Summer 2001, with compliance required by

Spring/Summer 2004.

Table 1: Timetable for the IESWTR Requirements

Date IESWTR Requirement

December 16, 1998 Rule is published in Federal Register [63 FR 241 69478].

February 16, 1999 60-day legal challenge period ends.

February 16, 1999 Construction of uncovered finished water storage facilities is prohibited [40 CFR

141.170(c)].

March 16, 1999 After this date, TTHM and HAA5 monitoring must begin for systems that do not have

ICR or occurrence data and wish to determine if they must develop a disinfection profile

[40 CFR 141.172(a)(2)(iii)].

April 16, 1999 Systems that have 4 consecutive quarters of HAA5 occurrence data that meet the TTHM

monitoring requirements must submit those data to the state to determine if they must

develop a disinfection profile [40 CFR 141.172(a)(5)(ii)].

December 31, 1999 TTHM and HAA5 data are due for those systems that collected data under the ICR to

determine if they must develop a disinfection profile [40 CFR 141.172(a)(5)(i)].

December 31, 1999 Systems that elect to profile without conducting 4 quarters of TTHM and HAA5

monitoring must notify the state of their election [40 CFR 141.172(a)(5)(iv)].

December 31, 1999 Systems that wish to request state approval of “a more representative annual data set”

than the ICR data set to determine if they must develop a disinfection profile must do so

in writing [40 CFR 141.172(a)(5)(v)]. 

March 31, 2000 TTHM and HAA5 monitoring must be complete for systems determining if they must

develop a disinfection profile [40 CFR 141.172(a)(2)(iii)(A)].

March 31, 2000 If system is using 3 years of existing operational data to develop the disinfection profile,

the profile generated from these data and a request for state approval must be submitted

[40 CFR 141.172(b)(3)(i)].

April 1, 2000 Systems determining if they must develop a disinfection profile must submit their

TTHM and HAA5 data to the state [40 CFR 141.172(a)(5)(iii)].

April 1, 2000 Systems must begin developing a disinfection profile if either their annual average

TTHM $ 0.064 mg/L or their annual average HAA5 $ 0.048 mg/L [40 CFR

141.172(b)(2)].

March 31, 2001 Disinfection profile is complete [40 CFR 141.172(b)(2)].
Date IESWTR Requirement

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March 31, 2001 After this date, systems that were required to develop a disinfection profile that wish to

make a significant change to their disinfection practice must first calculate a disinfection

benchmark and consult with the state [40 CFR 141.172(c)].

December 31, 2001 Systems that are not required to filter must comply with the requirements for TTHM in

§141.12 and §141.30 until this date. After this date, systems must comply with the

requirements in Subpart L for TTHM, HAA5, bromate, chlorite, chlorine, chloramines,

and chlorine dioxide [40 CFR 141.71(b)(6)].

December 31, 2001 Systems that do not meet all of the criteria for avoiding filtration and use

conventional/direct filtration must meet the turbidity requirements of the rule [0.3 NTU

CFE (combined filter effluent) 95 percent of the time, at no time exceed 1 NTU] [40

CFR 141.173]. 

December 31, 2001 Alternative technologies for systems that serve at least 10,000 people must remove 99

percent of Cryptosporidium oocysts, and the state must establish alternative turbidity

performance standards that must be met 95 percent of the time and a maximum [40 CFR

141.173(b)].

January 1, 2002 Systems must comply with the reporting and recordkeeping requirements of 40 CFR

141.175, including turbidity exceptions reporting. Systems must, when appropriate:

• Produce filter profiles or identify obvious reason for poor filter performance.

• Report profile has been produced or identify obvious reason for poor filter

performance.

• Conduct filter self-assessments.

• Have 3rd party CPEs performed.

December 2004 State must have first round of sanitary surveys completed for Subpart H CWSs [40 CFR

142.16(b)(3)(i)].

December 2006 State must have first round of sanitary surveys completed for Subpart H NCWSs [40

CFR 142.16(b)(3)(i)].

3. Summary of Requirements 

Disinfection profiling and benchmarking

Surface water or GWUDI systems having average annual TTHM $ 0.064 mg/L or annual average HAA5

$ 0.048 mg/L must develop a disinfection profile. The disinfection profile is a compilation of daily

measurements of microbial inactivation by disinfection, collected over the period of 1 year. From the

disinfection profile, the PWS calculates the average microbial inactivation potential for each month, and

the lowest monthly average inactivation becomes the disinfection benchmark.

The purpose of these provisions is to provide a process whereby a public water system (PWS) and the

state, working together, assure that there will be no significant reduction in microbial protection as the

result of disinfection practice modifications designed to meet the more restrictive maximum contaminant

levels (MCLs) for DBPs established in the Stage 1 DBPR. Those PWSs required to develop disinfection

profiles, and that then wish to modify their disinfection practices to meet the new MCLs, must establish

the disinfection benchmark and consult with the state prior to implementing such modifications. In

addition, PWSs must keep the disinfection profile on file for the state to review during their sanitary

surveys. The benchmark does not set a new regulatory floor for disinfection practice, but instead
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characterizes current practice so that the system, in consultation with the state, can make an informed

decision when implementing a modification.

Cryptosporidium

The IESWTR sets a maximum contaminant level goal (MCLG) of zero for the protozoan

Cryptosporidium. It also establishes a requirement for 2-log (99%) removal of Cryptosporidium for

systems that must currently filter under the SWTR. Systems that use conventional or direct filtration

meet this requirement if they are in compliance with the strengthened turbidity performance standards for

combined filter effluent in the IESWTR (discussed below). Systems that use slow sand or diatomaceous

earth filtration meet the 2-log removal requirement if they are in compliance with the existing turbidity

performance standards under the SWTR. 

The IESWTR also extends the existing watershed control requirements for unfiltered systems to include

the control of potential sources of Cryptosporidium. Such sources must be included in an unfiltered

system’s watershed control plan.

These new provisions, along with the new turbidity requirements, will better protect consumers from

Cryptosporidium and other pathogens.

Strengthened turbidity requirements

The IESWTR includes a series of requirements related to turbidity. These requirements strengthen

current SWTR requirements for combined filter effluent for systems that use conventional or direct

filtration. The turbidity level of a system’s combined filtered water at each plant must be less than or

equal to 0.3 nephelometric turbidity units (NTUs) in at least 95 percent of the measurements taken each

month, and the turbidity level of a system’s combined filtered water must at no time exceed 1 NTU

(under the SWTR, these turbidity requirements are 0.5 NTU and 5 NTU, respectively).

Individual filter monitoring requirements

The IESWTR requires continuous turbidity monitoring for individual filters. The rule requires that

surface water and GWUDI systems that use conventional or direct filtration must conduct continuous

turbidity monitoring (every 15 minutes) on the effluent of each individual filter. PWSs must report

instances of poor filter performance to the state, and, based on performance triggers, must take prescribed

actions to identify and correct the cause(s). This requirement will allow systems to identify filters whose

poor performance might be masked in a combined filter effluent.

Uncovered finished water storage facilities

The rule prohibits building any uncovered finished water storage facilities (reservoir, holding tank, or

other storage facility) for which construction begins after February 16, 1999. This provision will help

limit recontamination of treated water, but does not require that existing uncovered finished water

storage facilities be covered.

Public water system recordkeeping and reporting requirements

The IESWTR requires PWSs to submit combined filter effluent monitoring and compliance data and

report that they have conducted individual filter turbidity monitoring to states within 10 days after the

end of each month the system serves water to the public. Additionally, PWSs must report to the state if

certain individual filter monitoring trigger levels are exceeded. In this case, systems must report turbidity
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measurements and report that filter profiles, filter self-assessments, or Comprehensive Performance

Evaluation (CPE) reports have been produced or conducted when instances of poor filter performance

occur or persist based on monitoring of individual filter performance. Systems must maintain the results

of individual filter monitoring for at least three years.

Sanitary surveys

The IESWTR requires that the state must conduct sanitary surveys for all PWSs using surface water or

ground water under the direct influence of surface water (GWUDI), regardless of the population served,

no less frequently than every 3 years for community water systems and every 5 years for noncommunity

systems. For community water systems determined by the state in previous sanitary surveys to have

“outstanding performance,” successive sanitary surveys may be conducted at up to 5-year intervals.

Unfiltered Systems

The IESWTR requires unfiltered systems to continue to meet the SWTR source water and site-specific

requirements to remain unfiltered. In addition, unfiltered systems must include Cryptosporidium in their

watershed control programs and must meet all Stage 1 DBPR MCLs and MRDLs to remain unfiltered. 

Like filtered systems, they are subject to disinfection profiling and benchmarking and sanitary surveys.

4. Additional Information

A series of guidance manuals have been developed to support the Interim Enhanced Surface Water

Treatment Rule and the Stage 1 Disinfectants/Disinfection Byproducts Rule. The manuals will aid EPA,

state agencies and affected public water systems in implementing the two interrelated rules, and will help

to ensure that implementation among these groups is consistent. The manuals are available on EPA’s

website at www.epa.gov/safewater/mdbp/implement.html. Additional information on ordering these

manuals is provided below.

The manuals for the IESWTR include:

Disinfection Profiling and Benchmarking Guidance Manual (EPA 815-R-99-013)

Objective: To help determine if a disinfection profile (an evaluation of current disinfection practice) is

required and how to do one; when a disinfection benchmark must be determined and how to extract it

from the profile; and how a public water system uses the benchmark, in consultation with the state, to

protect from microbial risk when the system changes disinfection practice.

Contents: The manual provides detailed information on the following subjects: applicability of the

profiling and benchmarking requirements to public water systems; procedures for generating a

disinfection profile, including example profiles; methods for calculating the disinfection benchmark,

including example calculations; the use of the benchmark in modifying disinfection practices,

communicating with the state, and assessing significant changes to disinfection practices; the

development of the profiling and benchmarking regulations; the significance of the log inactivation

concept and CT values for inactivations achieved by various disinfectants; and the determination of

contact time.
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Guidance Manual for Compliance with the Interim Enhanced Surface Water Treatment Rule:

Turbidity Provisions (EPA 815-R-99-010)

Objective: The first section provides technical information regarding specific requirements of the

Interim Enhanced Surface Water Treatment Rule relating to turbidity and is intended for experienced

operators and others in the regulated community. The second section of the document provides

background on concepts surrounding turbidity and serves as a primer for less experienced operators and

individuals.

Contents: The first section contains key regulatory requirements including combined filter effluent

monitoring and individual filter monitoring; recordkeeping and reporting requirements; additional

compliance issues such as compliance schedule, public notification, variances/exemptions, and follow-up

action requirements; approved methods and additional measurement and calibration issues; components

and description of a filter self-assessment; and components and description of a Comprehensive

Performance Evaluation.The second section of the manual includes more basic information on turbidity;

description of the particles (both natural and man-made) which typically contribute to turbidity;

discussion of typical steps in a treatment process and how turbidity is removed or created in each step;

discussion of turbidity in different source waters with an emphasis of how changes in source water effect

turbidity; and basic turbidimeter design.

Alternative Disinfectants and Oxidants Guidance Manual (EPA 815-R-99-014)

Objective: To provide technical data and engineering information on disinfectants and oxidants that are

not as commonly used as chlorine, so that systems can evaluate their options for developing disinfection

schemes to control water quality problems such as zebra mussels and Asiatic clams, and oxidation to

control water quality problems associated with iron and manganese.

Contents: The manual discusses six disinfectants and oxidants: ozone, chlorine dioxide, potassium

permanganate, chloramines, ozone/hydrogen peroxide combinations, and ultraviolet light. A decision

tree is provided to help evaluate which disinfectant(s) is most appropriate given certain site-specific

conditions (e.g., water quality conditions, existing treatment and operator skill). The manual also

contains a summary of existing alternative disinfectants use in the United States and cost estimates for

the use of alternative disinfectants. 

Microbial and Disinfection Byproducts Simultaneous Compliance Manual (EPA 815-R-99-015)

Objective: To help public water systems achieve simultaneous compliance with various drinking water

regulations (e.g., Stage 1 Disinfectants and Disinfection Byproducts Rule, Interim Enhanced Surface

Water Treatment Rule, Lead and Copper Rule and the Total Coliform Rule). The manual discusses

operational problems systems may encounter when implementing these rules.

Contents: The manual provides detailed information on the requirements in the Stage 1 Disinfectants

and Disinfection Byproducts Rule and the Interim Enhanced Surface Water Treatment Rule.

Guidance Manual for Conducting Sanitary Surveys of Public Water Systems: Surface Water and

Ground Water Under the Direct Influence (GWUDI) (EPA 815-R-99-016)

Objective: The guidance manual provides an overview of how to conduct a sanitary survey of all water

systems using surface water and ground water under the direct influence of surface water. It is intended

to help state agencies improve their sanitary survey programs where needed.
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Contents: The manual provides information about the objective and regulatory context of sanitary

surveys. It covers four principal stages of a sanitary survey: planning, including preparatory steps to be

taken by inspectors before conducting the onsite portion; conducting the onsite survey; compiling a

sanitary survey report; and performing follow-up activities. 

Uncovered Finished Water Reservoirs (EPA 815-R-99-011)

Objective: To provide information on ways systems can limit water quality degradation in existing

finished water reservoirs. 

Contents: The manual provides detailed information on the following subjects: developing and

implementing comprehensive open finished water reservoir management plans based on site-specific

conditions; identifying potential sources of contamination in open finished water reservoirs and potential

mitigation measures; employing different methods to control the degradation of water quality while it

resides in the reservoir; monitoring schemes that can be used to characterize water quality and identify

water quality degradation before it becomes severe and is difficult to correct.

To order copies of these guidance manuals you may contact the Safe Drinking Water Hotline at 

(800) 426-4791 or you may download an electronic version from the OGWDW website at:

www.epa.gov/safewater/mdbp/implement.html

Guidance manuals are also available through the National Service Center for Environmental

Publications (NSCEP) (free of charge). These documents may also be purchased through National

Technical Information Service (NTIS)

NSCEP: 1.800.490.9198

NTIS: 1.800.553.6847

5. Detailed regulatory requirements

Detailed descriptions of the monitoring and reporting requirements for public water systems (PWSs) are

presented in the following section. The IESWTR applies only to subpart H systems that serve 10,000 or

more people, with the exception of a sanitary survey provision that applies to all subpart H systems (the

state or a third party conducts the sanitary survey). These systems are all required to monitor and report

similar data, with the exception of turbidity exceedance reports that will be prepared as required.

Combined filter effluent turbidity monitoring

The Interim Enhanced Surface Water Treatment Rule (IESWTR) establishes a number of provisions

related to the performance of filters used in drinking water treatment. These provisions include treatment

technique requirements restricting turbidity levels in the combined filter effluent. These requirements

are designed to decrease risk from waterborne microbial pathogens by limiting levels of particulate

material in finished water. EPA has used a treatment technique because it is neither technically nor

economically feasible to measure pathogens such as Giardia, Cryptosporidium, and viruses in either the

source water or treated water.
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Which systems must comply with turbidity requirements for the combined filter effluent under the

IESWTR?

The treatment technique requirements for combined filter effluent turbidity under the IESWTR apply to

public water systems (PWS) that use surface water or ground water under the direct influence of surface

water (GWUDI), serve 10,000 or more people, and are required to filter. 

What are the maximum allowable levels of turbidity in the combined filter effluent?

For systems using conventional filtration or direct filtration, the turbidity level of representative samples

of a system's filtered water must be less than or equal to 0.3 NTU in at least 95 percent of the

measurements taken each month, and must never exceed 1 NTU. For slow sand and diatomaceous earth

filtration systems, requirements for turbidity levels in the combined filter effluent remain as specified

under the SWTR (less than or equal to 1 NTU in 95 percent of the measurements taken each month and

never greater than 5 NTU). For systems using filtration technologies other than conventional, direct,

slow sand, or diatomaceous earth, the systems must demonstrate to the state, using pilot plant studies or
Page 15

Systems are not permitted to begin construction of uncovered finished water storage facilities

beginning 2/16/99.

Does system serve 

$10,000 people? Subpart H Systems

State and system must

comply with Sanitary

Survey Requirements

No further

requirements 

under the IESWTR

YES

NO

System must meet treatment technique requirement in 40 CFR 141.70 (SWTR) and must install and properly

operate treatment processes which reliably achieve:

At least 2 log removal of Cryptosporidium by filtration or Cryptosporidium control under the watershed control

plan for unfiltered systems

Does the system 

provide filtration?

General Requirements (1998 IESWTR)

System must comply with

Criteria for Avoiding Filtration

YES

YES

YES

Does the 

system use

conventional

filtration

treatment or

direct

filtration?

Does 

system use

slow sand or

diatomaceous

earth

filtration?

NO NO

System must meet 

Alternative Filtration

Requirements

(refer to attached flow

chart).

System must meet

Combined Filter Provisions of SWTR

for Slow Sand and Diatomaceous Earth

(refer to attached flow chart).

System must meet

Disinfection Profiling and Benchmarking

Provisions

(refer to attached flow chart)

NO

System must meet 

Individual Filter Provisions

(refer to attached flow chart).

System must meet 

Combined Filter Provisions

of IESWTR

(refer to attached flow chart).
Page 16

other means, that the alternative filtration technology in combination with disinfection treatment

consistently achieves 99.9 percent removal and/or inactivation of Giardia lamblia cysts, 99.99 percent

removal and/or inactivation of viruses, and 99 percent removal of Cryptosporidium oocysts. For each

approval of an alternative filtration technology, the state will set turbidity performance requirements that

the system must meet at least 95 percent of the time, and that the system may not exceed at any time, at

values that consistently achieve these levels of removal and/or inactivation of Giardia lamblia, viruses,

and Cryptosporidium. Failure to meet these requirements is a treatment technique violation.

What are the monitoring requirements for combined filter effluent turbidity?

Systems must monitor combined filter effluent turbidity as specified under the SWTR. This specifies

that turbidity measurements must be performed on representative samples of the system’s filtered water

every four hours (or more frequently) that the system serves water to the public. A public water system

may substitute continuous turbidity monitoring for grab sample monitoring if it validates the continuous

measurement for accuracy on a regular basis using a protocol approved by the state. For any systems

using slow sand filtration or filtration treatment other than conventional treatment, direct filtration, or

diatomaceous earth filtration, the state may reduce the sampling frequency to once per day if it

determines that less frequent monitoring is sufficient to indicate effective filtration performance. 

Turbidity must be measured using methods approved by EPA and by a party approved by the state. A

system that uses lime softening may acidify representative samples prior to analysis using a protocol

approved by the state. Failure to meet these requirements is a monitoring violation.

What are the reporting and recordkeeping requirements for turbidity in the combined filter

effluent?

The reporting requirements for combined filter effluent turbidity are unchanged from those established

under the SWTR, except where reporting levels have been modified to reflect more stringent turbidity

requirements established under the IESWTR. Required turbidity measurements must be reported within

10 days after the end of each month the system serves water to the public. Information that must be

reported includes: 1) the total number of filtered water turbidity measurements taken during the month;

2) the number and percentage of filtered water turbidity measurements taken during the month which are

less than or equal to the turbidity limits established under the SWTR for diatomaceous earth and slow

sand filtration systems, and under the IESWTR for conventional, direct, and alternative filtration

systems; and 3) the date and value of any turbidity measurements taken during the month which exceed 1

NTU for conventional and direct filtration systems, 5 NTU for slow sand and diatomaceous earth

filtration systems, and the maximum level established by the state for alternative filtration technology

systems. Failure to meet these requirements is a reporting/recordkeeping violation.

IESWTR COMBINED FILTER EFFLUENT TURBIDITY 

COMPLIANCE REQUIREMENTS

FILTRATION TECHNOLOGY 95th PERCENTILE 

TURBIDITY (NTU)

MAXIMUM

TURBIDITY (NTU)

Conventional filtration 0.3 1

Direct filtration 0.3 1

Diatomaceous earth filtration 1 5

Slow sand filtration 1 5

Filtration technologies not listed above as determined by the state as determined by the state
Page 17

Combined Filter Effluent Provisions of IESWTR

(Applicable to Conventional and Direct Filtration Systems)

Turbidity Performance Requirements

 - Measurements are taken every 4 hours of

representative samples of the systems

filtered water (as required under the SWTR)

- Turbidity must at no time exceed 1 NTU

- Turbidity must be less than or equal to

 0.3 NTU in at least 95 percent of the

measurements taken each month.

Reporting and Recordkeeping Requirements

Within 10 days after the end of the month, system must 

provide a report of turbidity measurements to the State 

which includes:

- Total number of measurements taken during the 

month

- Number and percentage of measurements less than

or equal to 0.3 NTU

- Date and value of any measurements taken during

the month which exceed 1 NTU.

Did System 

report all required

information to State within

10 days after the end of 

the month?

Did 

turbidity exceed 

1 NTU at any time?

Was

turbidity less than or equal to 

0.3 NTU in at least 95

percent of the measurements

taken each month?

MR Violation

TT Violation

TT Violation

YES

YES

YES

NO

NO

NO
Page 18

Alternative Filtration Requirements of the IESWTR

(Filtration Technologies other than conventional, direct, slow sand or diatomaceous earth)

Alternative Filtration Technologies

System must demonstrate to the State that the alternative filtration technology,

in combination with disinfection consistently meets:

- 3 log Giardia and 4 log virus

removal/inactivation

- 2 log Cryptosporidium removal

Did State

approve the alternative

filtration technology?

TT Violation

Alternative Turbidity Performance Requirements

The State will set turbidity performance requirements that the system must meet 95 percent of 

the time (95th PERCENTILE)

The State will set turbidity performance requirements that the system may not exceed at any 

time (MAXIMUM)

These performance requirements will be set at a level that consistently achieves 3 log Giardia

removal/inactivation, 4 log virus removal/inactivation and 2 log Cryptosporidium removal

Reporting and Recordkeeping Requirements

Within 10 days after the end of the month, the system must provide a report of turbidity

measurements to the State which includes:

1)Total number of measurements taken during the month

2)Number and percentage of measurements less than or equal to 95TH PERCENTILE

3)Date and value of any measurements taken during the month which exceed MAXIMUM

Did system report

to State within 10 days after

the end of the month?

Did turbidity 

exceed State-set MAXIMUM at 

any time?

Was turbidity 

less than or equal to 

State-set 95TH PERCENTILE in 

at least 95 percent of the 

measurements taken each

month?

MR Violation

TT Violation

TT Violation

NO

NO

NO

NO

YES

YES

YES

YES
Page 19

Combined Filter Effluent Provisions of SWTR

(Applicable to Systems using Slow Sand and Diatomaceous Earth Filtration)

Turbidity Performance Requirements

Systems must meet the following provisions:

- Measurements are taken every 4 hours of

representative samples of the systems filtered water

- State may reduce the monitoring frequency to once

per day for systems using slow sand or that serve

<500

- Turbidity must at no time exceed 5 NTU

- Turbidity must be less than or equal to 1 NTU in at

least 95 percent of measurements taken each month.

Reporting and Recordkeeping Requirements

Within 10 days after the end of the month, System 

must provide a report of turbidity measurements

 to the State which includes:

- Total number of measurements taken during the 

month

- Number and percentage of measurements less than

or equal to 1 NTU

- Date and value of any measurements taken during

the month which exceed 5 NTU.

Did System 

report all required

information to the 

State within10 days 

after the end of the 

month?

Did turbidity 

exceed 5 NTU at 

any time?

Was turbidity less 

than or equal to 1 NTU in at

 least 95 percent of the 

measurements taken each 

month?

MR Violation

TT Violation

TT Violation

YES

YES

YES

NO

NO

NO
Page 20

Individual filter turbidity monitoring

The IESWTR establishes a number of requirements related to the performance of filters used in drinking

water treatment. Included in these requirements are provisions mandating that certain systems monitor

the effluent of individual filters. These provisions are designed to decrease the risk of microbial

pathogen contamination of finished waters by focusing greater attention on the performance of individual

filters. 

Which systems are required to monitor individual filters?

The filtration requirements of the IESWTR apply to PWSs that use surface water or GWUDI, serve

10,000 or more people, and are required to filter. Systems that provide conventional or direct filtration

treatment must monitor individual filters.

What are the monitoring requirements for individual filters?

Systems must continuously measure the effluent turbidity of each individual filter using a method

approved by EPA, and must record the results every 15 minutes. If there is a failure in the continuous

turbidity monitoring equipment, the system must conduct grab sampling every four hours in lieu of

continuous monitoring until the turbidimeter is repaired or replaced, and is in violation if the turbidimeter

is not replaced or repaired within five working days following the failure of the equipment. Failure to

comply with these requirements is a monitoring violation. 

What are the reporting and recordkeeping requirements for individual filter monitoring?

Systems required to monitor individual filters must maintain the results of this monitoring for at least 3

years. Within 10 days after the end of each month, these systems must make a report to the state that

they have conducted individual filter turbidity monitoring. Systems must report individual filter turbidity

measurements only if the measurements demonstrate any of the following four exceedance conditions: 

1) Any individual filter that has a measured turbidity level of greater than 1.0 NTU in two

consecutive measurements taken 15 minutes apart. The system must report the filter

number, the turbidity measurement, and the date(s) on which the exceedance occurred. 

The system must also either identify and report an obvious reason for the exceedance or

produce a filter profile for the filter within 7 days of the exceedance and report that the

profile has been produced. (A filter profile is a graphical representation of turbidity or

total particle counts as a function of time for an entire filter run. A discussion of filter

profiles is included in EPA’s guidance document on turbidity.)

2) Any individual filter that has a measured turbidity level of greater than 0.5 NTU in two

consecutive measurements taken 15 minutes apart at the end of the first four hours of

continuous filter operation after the filter has been backwashed or otherwise taken

offline. The system must report the filter number, the turbidity measurement, and the

date(s) on which the exceedance occurred. The system must also either identify and

report an obvious reason for the exceedance or produce a filter profile for the filter

within 7 days of the exceedance and report that the profile has been produced. (A filter

profile is a graphical representation of turbidity or total particle counts as a function of

time for an entire filter run. A discussion of filter profiles is included in EPA’s guidance

document on turbidity.)

3) Any individual filter that has a measured turbidity level of greater than 1.0 NTU in two

consecutive measurements taken 15 minutes apart at any time in each of three

consecutive months. The system must report the filter number, the turbidity

measurement, and the date(s) on which the exceedance occurred. The system must

conduct a self-assessment of the filter within 14 days of the exceedance and report that
Page 21

the self-assessment was conducted in the monthly report. The self-assessment must

consist of at least the following components: assessment of filter performance,

development of a filter profile, identification and prioritization of factors limiting filter

performance, assessment of the applicability of corrections, and preparation of a filter

self-assessment report.

4) Any individual filter that has a measured turbidity level greater than 2.0 NTU in two

consecutive measurements taken 15 minutes apart at any time in each of two consecutive

months. The system must report the filter number, the turbidity measurement, and the

date(s) on which the exceedance occurred. The system must arrange for the conduct of

a comprehensive performance evaluation (CPE) by the state or a third part approved by

the state no later than 30 days following the exceedance. (A CPE is a thorough review

and analysis of a treatment plant’s performance-based capabilities and associated

administrative, operation and maintenance practices.) The CPE must be completed and

submitted to the state no later than 90 days following the exceedance.

The turbidity guidance manual has detailed information about filter profiling, filter self-assessments, and

CPEs. Systems using lime softening may apply to the state for alternative exceedance levels to those

specified above if they can demonstrate that higher turbidity levels in individual filters are due to lime

carryover only and not due to degraded filter performance.

Failure to comply with these requirements is a reporting violation. However, the exceedance criteria are

not treatment technique requirements, and systems have not committed a violation solely by

demonstrating any of the exceedance conditions in their individual filters.
Page 22

Individual Filter Provisions (1998 IESWTR)

Was there

a failure in continuous

turbidity monitoring

equipment?

System must conduct

grab sampling every

4 hours in lieu of

continuous monitoring

and must replace the

turbidimeter within 5

working days following

equipment failure.

Was 

monitoring conducted

continuously and were the

results recorded?

Did system

conduct grab sampling

and reestablish continuous

monitoring by the 5th

working day following

equipment failure?

Individual Filter Monitoring and Reporting

Requirements

- Systems using conventional or direct 

filtration

- Continuous monitoring must be conducted

at each filter

- System must record results of this 

monitoring every 15 minutes and maintain

these records for at least 3 years.

- Within 10 days after the end of the month, 

system must report to the State that this

monitoring was conducted (specific results

not required to be reported).

- Turbidimeters must be calibrated using

procedure specified by manufacturer.

NO YES

YES

Did system

report to State within 10

days after end of month

that monitoring was

conducted?

MR Violation5

NO

YES

MR Violation5

NO

MR Violation5

NO

Monthly Exceedance Reporting

Requirements1

System must provide a report within

10 days after end of month for any

individual filter turbidity measurement

(based on 2 consecutive 

measurements taken 15 minutes 

apart) that meets any of the following:

- greater than 1.0 NTU

- greater than 0.5 NTU after

the first 4 hours of operation

- greater than 1.0 NTU in each of three

consecutive months

- greater than 2.0 NTU in two

consecutive months.

The report shall include the filter 

number, the turbidity measurement,

and the date(s) on which the

exceedance occurred.

YES

Was reason

reported?

System must report the

obvious reason to the State

Is there an 

obvious reason

for the

abnormal filter

performance? 

Were any 2 

consecutive 

 individual filter

turbidity measurement:

-greater than 0.5 NTU after

the first four hours of 

operation or

-greater than 1.0 NTU?

YES

YES

YES

MR Violation5

NO

Did system

produce profile within

7 days and report that

it was produced??

NO

System must

produce a filter

profile within 7 days

of exceedance and

report that the profile

has been produced

NO

Did any

individual filter

have 2 consecutive 

turbidity

measurement > 1.0

NTU in each of three

consecutive 

months?

YES

System must conduct a

self-assessment 2 of the filter

within 14 days of the

exceedance and report that

self-assessment was

conducted.

MR Violation5

Did system

conduct self

assessment within

14 days and report

to State that it was

produced?

YES

NO

Were any 

2 consecutive

individual filter

turbidity measurement

greater than 2.0 NTU

in two consecutive

months?

System must contact State or third

party approved by State to conduct a

CPE3 no later than 30 days after

exceedance and have the evaluation

completed and submitted to the 

State no later than 90 days following

exceedance. 

Did system

contact State or

third party to

conduct CPE4 

within 30 days of 

exceedance?

MR Violation5

Was evaluation

completed and

submitted to State

within 90 days?

NO NO

YES

YES

YES

NO

NO

NOTES

1 Systems that use lime softening may apply to the State for alternative exceedance levels if they can demonstrate that higher levels are due to lime carry-over only and not due to degraded filter performance.

2 A self-assessment must consist of at least the following components 1). assessment of filter performance; 2). development of filter profile; 3). identification and prioritization of factors limiting performance; 4). Assessment of the applicability of

corrections; and 5). Preparation of filter assessment report.

3 CPE- Comprehensive Performance Evaluation.

4

 State has the authority to require full Composite Correction Program (CCP) which consists of CPE and Comprehensive Technical Assistance (CTA).

5

 System has MR violation until relevant task is completed (e.g., filter profile produced).

NO

YES
Page 23

What ROUTINE MONITORING must I conduct under the IESWTR?

What do I have to REPORT to the State?

IMPORTANT: The information in the table below does not include the requirements for determining

profiling applicability, disinfection profiling, and disinfection benchmarking. Please refer to the section

on Disinfection Benchmarking for these monitoring and sampling requirements.

Activity Requirement

Combined filter

effluent

monitoring

All systems must continue to monitor the combined filter effluent at the same location and

frequency as under the SWTR.

Turbidity

Monitoring at

Individual

Filters

• All systems using conventional filtration treatment or direct filtration must conduct

continuous turbidity monitoring for each individual filter using an approved method and 

Individual must calibrate turbidimeters using the procedure specified by the manufacturer.

• Systems must record the results of individual filter monitoring every 15 minutes.

• If there is a failure in the continuous turbidity monitoring equipment, the system must

conduct grab sampling every 4 hours in lieu of continuous monitoring .

Triggers for

Turbidity

Exceptions

Reporting for

Individual

Filters

• For any individual filter that has a measured turbidity level of greater than 1.0 NTU in 2

consecutive measurements taken 15 minutes apart, the system must report the filter number,

turbidity measurement, and date of exceedance. The system must produce a filter profile for

the filter within 7 days of the exceedance and report that the profile has been produced or

report the obvious reason for the exceedance.

• For any individual filter that has a measured turbidity level of greater than 0.5 NTU in 2

consecutive measurements taken 15 minutes apart after the first 4 hours of operation after the

filter has been backwashed or otherwise taken offline, the system must report the filter

number, turbidity measurement, and date of exceedance. The system must produce a filter

profile for the filter within 7 days of the exceedance and report that the profile has been

produced or report the obvious reason for the exceedance.

• For any individual filter that has a measured turbidity level of greater than 1.0 NTU in 2

consecutive measurements taken 15 minutes apart in each of 3 consecutive months, the

system must report the filter number, turbidity measurement, and date of exceedance. The

system must conduct a self-assessment of the filter within 14 days of the exceedance and

report that the self-assessment was conducted.

• For any individual filter that has a measured turbidity level of greater than 2.0 NTU in 2

consecutive measurements taken 15 minutes apart in 2 consecutive months, the system must

report the filter number, turbidity measurement, and date of exceedance. The system must

contact the state or 3rd party to conduct a CPE no later than 30 days following the

exceedance and have the evaluation completed and submitted to the state no later than 90

days following the exceedance. 

Reporting and

Recordkeeping

Individual Filter Data

• Results of individual filter monitoring must be maintained for at least 3 years.

• Individual filter data must be reported only if there has been a turbidity exceedance

Combined Filter Effluent Data Reporting

• Total number of combined filter effluent turbidity measurements taken during last month that

do not exceed the turbidity limits.

• Date and value of any turbidity measurements taken during the month that exceed 1 NTU for

systems using conventional or direct filtration.

• Turbidity measurements must be reported within 10 days after the end of each month the

system serves water to the public.
Page 24

Disinfection profiling and benchmarking

The Interim Enhanced Surface Water Treatment Rule (IESWTR) establishes disinfection benchmarking

as a procedure requiring certain public water systems (PWSs) to evaluate the impact on microbial risk of

proposed changes in disinfection practice. It is designed to help utilities and states work together to

assure that pathogen control is maintained while the provisions of the Stage 1 Disinfectants and

Disinfection Byproducts Rule (Stage 1 DBPR) are implemented. This procedure involves a PWS

charting daily levels of pathogen inactivation for a period of at least one year to create a profile of

inactivation performance. The PWS then uses this profile to determine a baseline or benchmark of

inactivation against which proposed changes in disinfection practices can be measured. Profiling and

benchmarking is explained in detail in the Disinfection Profiling and Benchmarking Guidance Manual.

Who is required to prepare a disinfection profile?

Surface water or GWUDI systems having average annual TTHM $ 0.064 mg/L or annual average 

HAA5 $ 0.048 mg/L as a result of data or specific monitoring conducted by March 31, 2000 must

develop a disinfection profile. These levels, equal to 80% of the MCLs established for these compounds

by the Stage 1 DBPR, are intended to include most systems that will modify their disinfection practices

to comply with the Stage 1 DBPR. To determine applicability, systems that collected TTHM and HAA5

data under the ICR must use the results of the last 12 months of ICR monitoring unless the state

determines there is a more representative data set. Non ICR systems may either use existing TTHM and

HAA5 data, if approved by the state, or must conduct TTHM and HAA5 monitoring for four quarters. 

This monitoring must be completed before April 2000. Alternatively, systems can elect to forgo this

monitoring if they construct a disinfection profile.

How are the disinfection profile and benchmark developed?

A disinfection profile consists of a compilation of daily Giardia lamblia log inactivations (plus virus

inactivations for systems using either chloramines or ozone for primary disinfection) computed over a

period of at least one year through the entire treatment plant. It is based on daily measurements of

disinfectant residual concentration(s), contact time(s), temperature, and pH. A system with more than

one point of disinfection application must conduct this monitoring for each disinfection segment. The

profile may also be developed using up to 3 years of existing (i.e. grandfathered) data if the state finds

the data acceptable. Systems having less than 3 years of acceptable grandfathered data are required to

conduct one year of monitoring to create the profile. This monitoring must be completed by April 2001. 

The disinfection benchmark is equal to the lowest monthly average inactivation level in the disinfection

profile (or average of low months for multi-year profiles). 

How are the disinfection profile and benchmark used?

Any system required to develop a disinfection profile under the IESWTR that decides to make a

significant change to its disinfection practice must calculate its benchmark and consult with the state

prior to and only if making a significant change. Significant changes in disinfection practice are defined

as: 1) changes to the point of disinfection; 2) changes to the disinfectant(s) used in the treatment plant; 3)

changes to the disinfection process; and 4) any other modification identified by the state. As part of the

consultation process, the system must submit to the state the following information: a description of the

proposed change; the disinfection profile for Giardia lamblia (and, if necessary, viruses) and benchmark;

and an analysis of how the proposed change will affect the current levels of disinfection. In addition, the

state is required to review the disinfection profile as part of its periodic sanitary survey.
Page 25

Disinfection Profiling and Benchmarking Provisions (1998 IESWTR)

Subpart H System

serving $10,000?

NO Profiling and Benchmarking

provisions do not apply.

YES

System needs to determine whether

Profiling and Benchmarking is required. 

Did system 

collect TTHM and HAAS

data under the 1996

Information Collection 

Rule (ICR)?

Has the

State determined if

there is a more

representative data

set?

Has the system

collected 4 consecutive

quarters of TTHM

compliance data and

HAA5 occurrence

data?

Has the State

approved the use of

this data for

applicability

determination?4,5

NO

NO

YES YES YES

NO NO NO

Has the

system elected to

forgo TTHH/HAA5

monitoring?

System must collect 4 

consecutive quarters of

TTHM and HAA5 data

beginning no later than

Apr-Jun ‘99 quarter and

completed no later than

Mar ‘00.3

Systems must submit

the 4 quarters of data to 

the State by March 2000

and use that data to

determine applicability.

Systems must submit data to

State no later than 4 mos

after promulgation (Apr ‘99)

and use that data to

determine applicability.

System must notify State

in writing no later than 12

mos after promulgation

(Dec. ‘99).

YES

System must

develop

a Disinfection

Profile

and keep it

on file.6

Does system

have annual average of

TTHM $0.064 mg/L

OR

HAA5 $ 0.048 mg/L?

YES

System is in compliance with Profiling and Benchmarking

requirements.

Disinfection Profile is not needed.

NO

Has system

decided to make

significant change

to disinfection

practices?

NO

System is in compliance

with Profiling and 

Benchmarking

requirements.

System must calculate

Benchmark and 

Consult with State.

YES

Did 

system

calculate benchmark

and consult with the

State?

TT Violation

NO

System must submit

1998 ICR data to State

no later than 12 mos

after promulgation

(Dec 99) and use that

data for determining

applicability.

System uses

more 

representative

data set to

determine

applicability.

YES

YES

NOTES

1TTHM and HAA5 averages must be taken from same time period.

2Any lab approved under the ICR or using ICR-approved methods may conduct HAA5 analyses.

3TTHM and HAA5 monitoring must meet same sampling number and location requirements as TTHM in 141.12 and 141.30; and same handling

and analytical requirements as the ICR in 141.142(b)(1).

4System must conduct HAA5 monitoring until state approves of the existing data.

5State may also require a more representative data set.

6Disinfection Profile must be kept on file for State to review during Sanitary Survey.

Did 

system

develop a

profile and

keep it

on file?

YES

NO

TT Violation
Page 26

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