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Water: Microbial & Disinfection Byproducts Rules

Microbial/Disinfection Byproducts Federal Advisory Committee Agreement in Principle

1.0 Introduction
Pursuant to requirements under the Safe Drinking Water Act (SDWA), the Environmental Protection Agency (EPA) is developing interrelated regulations to control microbial pathogens and disinfectants/disinfection byproducts (D/DBPs) in drinking water. These rules are collectively known as the microbial/disinfection byproducts (M/DBP) rules.

The regulations are intended to address complex risk trade-offs between the two different types of contaminants. In keeping with the agreement reached during the 1992-93 negotiated rulemaking on these matters, EPA issued a Notice of Proposed Rulemaking for Disinfection By-Products Stage I on July 29, 1994. EPA also issued a Notice of Proposed Rulemaking for an Interim Enhanced Surface Water Treatment Rule (IESWTR) on July 29, 1994. Finally, in May 1996, EPA promulgated a final Information Collection Rule (ICR), to obtain data on source water quality, byproduct formation and drinking water treatment plant design and operations.

As part of recent amendments to the SDWA, Congress has established deadlines for all the M/DBP rules, beginning with a November 1998 deadline for promulgation of both the IESWTR and the Stage I D/DBP Rule. To meet this new deadline, EPA initiated an expedited schedule for development of these two rules. Building on the 1994 proposals, EPA intends to issue a Notice of Data Availability (NODA) in November 1997 for public comment. EPA also decided to establish a committee under the Federal Advisory Committee Act (FACA) for development of the rules.

The M/DBP Advisory Committee is made up of organizational members (parties) named by EPA (see Attachment A). The immediate task of the Committee has been to discuss, evaluate and provide advice on data, analysis and approaches to be included in the NODA to be published in November 1997. This Committee met four times from March through June 1997, with the initial objective to reach consensus, where possible, on the elements to be contained in the D/DBP Stage I and IESWTR NODA. Where consensus was not reached, the Committee sought to develop options and/or to clarify key issues and areas of agreement and disagreement. This document is the Committee's statement on the points of agreement reached.

2.0 Agreement in Principle
The Microbial and Disinfection By-Products Federal Advisory Committee considered the technical and policy issues involved in developing a DBP Stage I rule and an IESWTR under the Safe Drinking Water Act and recommends that the Environmental Protection Agency base the applicable sections of its anticipated M/DBP Notice of Data Availability (NODA) on the elements of agreement described below.

This agreement in principle represents the consensus of the parties on the best conceptual principles that the Committee was able to generate within the allocated time and resources available.

The USEPA, a party to the negotiations, agrees that:

  1. The person signing this agreement is authorized to commit this party to its terms.
  2. EPA agrees to hold a meeting in July 1997 following circulation of a second draft of the NODA to obtain comments from the parties and the public on the extent to which the applicable sections of the draft NODA are consistent with the agreements below.
  3. Each party and individual signatory that submits comments on the NODA agrees to support those components of the NODA that reflect the agreements set forth below.

    Each party and individual signatory reserves the right to comment, as individuals or on behalf of the organization he or she represents, on any other aspect of the Notice of Data Availability.
  4. EPA will consider all relevant comments submitted concerning the Notice(s) of Proposed Rulemaking and in response to such comments will make such modifications in the proposed rule(s) and preamble(s) as EPA determines are appropriate when issuing a final rule.
  5. Recognizing that under the Appointments Clause of the Constitution governmental authority may be exercised only by officers of the United States and recognizing that it is EPA's responsibility to issue final rules, EPA intends to issue final rules that are based on the provisions of the Safe Drinking Water Act, pertinent facts, and comments received from the public.
  6. Each party agrees not to take any action to inhibit the adoption of final rule(s) to the extent it and corresponding preamble(s) have the same substance and effect as the elements of this agreement in principle.

2.1 MCLs
MCLs should remain at the levels proposed: 0.080 mg/l for TTHMs, 0.060 mg/l for HAA5, and 0.010 mg/l for bromate.

2.2 Enhanced Coagulation The proposed enhanced coagulation provisions should be revised as follows:

a. The top row of the TOC removal table (3x3 matrix) should be modified for systems that practice enhanced coagulation by lowering the TOC removal percentages by 5 % across the top row, while leaving the other rows the same.

b. SUVA (specific UV absorbance) should be used for determining whether systems would be required to use enhanced coagulation. The use of a raw water SUVA < 2.0 liter/mg-m as a criterion for not requiring a system to practice enhanced coagulation should be added to those proposed in §141.135(a)(1)(i)-(iv).

c. For a system required to practice enhanced coagulation or enhanced softening, the use of a finished water SUVA < 2.0 liter/mg-m should be added as a Step 2 procedure. Such a criterion would be in addition to the proposed Step 2 procedure, not in lieu of it.

d. The proposed TOC removals for softening systems should be modified by lowering the value for TOC removal in the matrix at alkalinity > 120 mg/l and TOC between 2-4 mg/l by 5 % (which would make it equal to the value for non-softening systems) and leaving the remaining values as proposed.

e. If a system is required to practice enhanced softening, lime softening plants would not be required to perform lime soda softening or to lower alkalinity below 40-60 mg/l as part of any Step 2 procedure.

f. There is no need to separately address softening systems in the 3x3 matrix or the Step 1 regulatory language, which was identical to enhanced coagulation regulatory language in the proposed D/DBPR. The revised matrix should appear as follows:

Alkalinity (mg/l)
TOC (mg/l) 0 - <60 60 - <120 =>120
2 - 4 35 25 15
4 - 8 45 35 25
>8 50 40 30

2.3 Microbial Benchmarking/Profiling
A microbial benchmark to provide a methodology and process by which a PWS and the State, working together, assure that there will be no significant reduction in microbial protection as the result of modifying disinfection practices in order to meet MCLs for TTHM and HAA5 should be established as follows:

A. Applicability. The following PWSs to which the IESWTR applies must prepare a disinfection profile:

1) PWSs with measured TTHM levels of at least 80% of the MCL (0.064 mg/l) as an annual average for the most recent 12 month compliance period for which compliance data are available prior to November 1998 (or some other period designated by the State),

2) PWSs with measured HAA5 levels of at least 80% of the MCL (0.048 mg/l) as an annual average for the most recent 12 month period for which data are available (or some other period designated by the State) - In connection with HAA5 monitoring, the following provisions apply:

a) PWSs that have collected HAA5 data under the Information Collection Rule must use those data to determine the HAA5 level, unless the State determines that there is a more representative annual data set.

b) For those PWSs that do not have four quarters of HAA5 data 90 days following the IESWTR promulgation date, HAA5 monitoring must be conducted for four quarters.

B. Disinfection profile. A disinfection profile consists of a compilation of daily Giardia lamblia log inactivations (or virus inactivations under conditions to be specified), computed over the period of a year, based on daily measurements of operational data (disinfectant residual concentration(s), contact time(s), temperature(s), and where necessary, pH(s)). The PWS will then determine the lowest average month (critical period) for each 12 month period and average critical periods to create a "benchmark" reflecting the lower bound of a PWS's current disinfection practice. Those PWSs that have all necessary data to determine profiles, using operational data collected prior to promulgation of the IESWTR, may use up to three years of operational data in developing those profiles. Those PWSs that do not have three years of operational data to develop profiles must conduct the necessary monitoring to develop the profile for one year beginning no later than 15 months after promulgation, and use up to two years of existing operational data to develop profiles.

C. State review. The State will review disinfection profiles as part of its sanitary survey. Those PWSs required to develop a disinfection profile that subsequently decide to make a significant change in disinfection practice (i.e., move point of disinfection, change the type of disinfectant, change the disinfection process, or any other change designated as significant by the State) must consult with the State prior to implementing such a change. Supporting materials for such consultation must include a description of the proposed change, the disinfection profile, and an analysis of how the proposed change will affect the current disinfection.

D. Guidance. EPA, in consultation with interested stakeholders, will develop detailed guidance for States and PWSs on how to develop and evaluate disinfection profiles, identify and evaluate significant changes in disinfection practices, and guidance on moving the point of disinfection from prior to the point of coagulant addition to after the point of coagulant addition.

2.4 Disinfection Credit
Consistent with the existing provisions of the 1989 Surface Water Treatment Rule, credit for compliance with applicable disinfection requirements should continue to be allowed for disinfection applied at any point prior to the first customer. EPA will develop guidance on the use and costs of oxidants that control water quality problems (e.g., zebra mussels, Asiatic clams, iron, manganese, algae) and whose use will reduce or eliminate the formation of DBPs of public health concern.

2.5 Turbidity
Turbidity Performance Requirements. For all surface water systems that use conventional treatment or direct filtration, serve more than 10,000 people, and are required to filter: a) the turbidity level of a system's combined filtered water at each plant must be less than or equal to 0.3 NTU in at least 95 percent of the measurements taken each month and, b) the turbidity level of a system's combined filtered water at each plant must at no time exceed 1 NTU. For both the maximum and the 95th percentile requirements. compliance shall be determined based on measurements of the combined filter effluent at four-hour intervals.

Individual Filter Requirements. All surface water systems that use rapid granular filtration, serve more than l0,000 people, and are required to filter shall conduct continuous monitoring of turbidity for each individual filter and shall provide an exceptions report to the State on a monthly basis. Exceptions reporting shall include the following: 1) any individual filter with a turbidity level greater than l.0 NTU based on 2 consecutive measurements fifteen minutes apart; and 2) any individual filter with a turbidity level greater than 0.5 NTU at the end of the first 4 hours of filter operation based on 2 consecutive measurements fifteen minutes apart. A filter profile will be produced if no obvious reason for the abnormal filter performance can be identified.

If an individual filter has turbidity levels greater than l .0 NTU based on 2 consecutive measurements fifteen minutes apart at any time in each of 3 consecutive months, the system shall conduct a self-assessment of the filter utilizing as guidance relevant portions of guidance issued by the Environmental Protection Agency for Comprehensive Performance Evaluation (CPE). If an individual filter has turbidity levels greater than 2.0 NTU based on 2 consecutive measurements fifteen minutes apart at any time in each of two consecutive months, the system will arrange for the conduct of a CPE by the State or a third party approved by the State.

State Authority. States must have rules or other authority to require systems to conduct a Composite Correction Program (CCP) and to assure that systems implement any follow-up recommendations that result as part of the CCP.

2.6 Cryptosporidium MCLG
EPA should establish an MCLG to protect public health. The Agency should describe existing and ongoing research and areas of scientific uncertainty on the question of which species of Cryptosporidium represents a concern for public health (e.g. parvum, muris, serpententious) and request further comment on whether to establish an MCLG on the genus or species level.

In the event the Agency establishes an MCLG on the genus level, EPA should make clear that the objective of this MCLG is to protect public health and explain the nature of scientific uncertainty on the issue of taxonomy and cross reactivity between strains. The Agency should indicate that the scope of MCLG may change as scientific data on specific strains of particular concern to human health become available.

2.7 Removal of Cryptosporidium
All surface water systems that serve more than l 0,000 people and are required to filter must achieve at least a 2 log removal of Cryptosporidium. Systems which use rapid granular filtration (direct filtration or conventional filtration treatment - as currently defined in the SWTR), and meet the turbidity requirements described in Section 2.5 are assumed to achieve at least a 2 log removal of Cryptosporidium. Systems which use slow sand filtration and diatomaceous earth filtration and meet existing turbidity performance requirements (less than 1 NTU for the 95th percentile or alternative criteria as approved by the State) are assumed to achieve at least a 2 log removal of Cryptosporidium.

Systems may demonstrate that they achieve higher levels of physical removal.

2.8 Multiple Barrier Concept
EPA should issue a risk-based proposal of the Final Enhanced Surface Water Treatment Rule for Cryptosporidium embodying the multiple barrier approach (e.g. source water protection, physical removal, inactivation, etc.), including, where risks suggest appropriate, inactivation requirements. In establishing the Final Enhanced Surface Water Treatment Rule, the following issues will be evaluated:

  • data and research needs and limitations (e.g. occurrence, treatment, viability, active disease surveillance, etc.);
  • technology and methods capabilities and limitations;
  • removal and inactivation effectiveness;
  • risk tradeoffs including risks of significant shifts in disinfection practices;
  • cost considerations consistent with the SDWA;
  • reliability and redundancy of systems;
  • consistency with the requirements of the Act.

2. 9 Sanitary Surveys
Sanitary surveys operate as an important preventive tool to identify water system deficiencies that could pose a risk to public health. EPA and ASDWA have issued a joint guidance dated 12/21/95 on the key components of an effective sanitary survey. The following provisions concerning sanitary surveys should be included.


A) A sanitary survey is an onsite review of the water source (identifying sources of contamination using results of source water assessments where available), facilities, equipment, operation, maintenance, and monitoring compliance of a public water system to evaluate the adequacy of the system, its sources and operations and the distribution of safe drinking water.

B) Components of a sanitary survey may be completed as part of a staged or phased state review process within the established frequency interval set forth below.

C) A sanitary survey must address each of the eight elements outlined in the December 1995 EPA/STATE Guidance on Sanitary Surveys.


A) Conduct sanitary surveys for all surface water systems (including groundwater under the influence) no less frequently than every three years for community systems except as provided below and no less frequently than every five years for noncommunity systems.

- May "grandfather"sanitary surveys conducted after December 1995, if they address the eight sanitary survey components outlined above.

B) For community systems determined by the State to have outstanding performance based on prior sanitary surveys, successive sanitary surveys may be conducted no less than every five years.


A) Systems must respond to deficiencies outlined in a sanitary survey report within at least 45 days, indicating how and on what schedule the system will address significant deficiencies noted in the survey.

B) States must have the appropriate rules or other authority to assure that facilities take the steps necessary to address significant deficiencies identified in the survey report that are within the control of the PWS and its governing body.

Agreed to by:

Name, Organization


Signed By:

Peter L. Cook, National Association of Water Companies
Michael A. Dimitriou, International Ozone Association
Cynthia C. Dougherty, US Environmental Protection Agency
Mary J.R. Gilchrist, American Public Health Association
Jeffrey K. Griffiths, National Association of People with AIDS
Barker Hamill, Association of State Drinking Water Administrators
Robert H. Harris, Environmental Defense Fund
Edward G. Means III, American Water Works Association
Rosemary Menard, Large Unfiltered Systems
Erik D. Olson, Natural Resources Defense Council
Brian L. Ramaley, Association of Metropolitan Water Agencies
Charles R. Reading Jr., Water and Wastewater Equipment Manufacturers Association
Suzanne Rude, National Association of Regulatory Utility Commissioners
Ralph Runge, Chlorine Chemistry Council
Coretta Simmons, National Association of State Utility Consumer Advocates Bruce Tobey, National League of Cities
Chris J. Wiant, National Association of City and County Health Officials; National Environmental Health Association

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