# National Primary Drinking Water Regulations: Disinfectants and Disinfection Byproducts Notice of Data Availability > Briefs, arguments, decisions, and more. URL: https://www.frixlaw.com/law-library/documents/fr%3A97-28746 ## Record - **Collection:** Federal Register - **Document type:** Proposed Rule - **Published:** November 3, 1997 - **Citation:** 62 FR 59388 ## Text SUMMARY: In 1994 USEPA proposed a Stage 1 Disinfectants/Disinfection Byproducts Rule (DBPR) to reduce the level of exposure from disinfectants and disinfection byproducts (DBPs) in drinking water (USEPA, 1994b). This Notice of Data Availability summarizes the 1994 proposal; describes new data and information that the Agency has obtained and analyses that have been developed since the proposal; provides information concerning recommendations of the Microbial- Disinfection/Disinfectants Byproducts (M-DBP) Advisory Committee (chartered in February 1997 under the Federal Advisory Committee Act) on key issues related to the proposal; and requests comment on these recommendations as well as on other regulatory implications that flow from the new data and information. USEPA solicits comment on all aspects of this Notice and the supporting record. The Agency also solicits additional data and information that may be relevant to the issues discussed in the Notice. USEPA is particularly interested in public comment on the Committee's recommendations and whether the Agency should reflect these recommendations in the final rule. USEPA also requests that any information, data or views submitted to the Agency since the close of the comment period on the 1994 proposal that members of the public would like the Agency to consider as part of the final rule development process be resubmitted during this current 90- day comment period unless already in the underlying record in the Docket for this Notice. The Stage 1 DBPR would apply to community water systems and nontransient noncommunity water systems that treat their water with a chemical disinfectant for either primary or residual treatment. In addition, certain requirements for chlorine dioxide would apply to transient noncommunity water systems because of the short-term health effects from high levels of chlorine dioxide. Key issues related to the Stage 1 DBPR that are addressed in this Notice include the establishment of Maximum Contaminant Levels for total trihalomethanes, five haloacetic acids, bromate and chlorite; requirements for enhanced coagulation and enhanced softening; disinfection credit; health effects information; and analytical methods. Today's Federal Register also contains a related Notice of Data Availability for the Interim Enhanced Surface Water Treatment Rule (IESWTR). USEPA proposed this rule at the same time as the Stage 1 DBPR and plans to promulgate it along with the Stage 1 DBPR in November 1998. DATES: Comments should be postmarked or delivered by hand on or before February 3, 1998. Comments must be received or post-marked by midnight February 3, 1998. ADDRESSES: Send written comments to DBP NODA Docket Clerk, Water Docket (MC-4101); U.S. Environmental Protection Agency; 401 M Street, SW; Washington, DC 20460. Please submit an original and three copies of your comments and enclosures (including references). If you wish to hand-deliver your comments, please call the Docket between 9:00 a.m. and 4 p.m., Monday through Friday, excluding legal holidays, to obtain the room number for the Docket. Comments may be submitted electronically to [email protected]. FOR FURTHER INFORMATION CONTACT: The Safe Drinking Water Hotline, Telephone (800) 426-4791. The Safe Drinking Water Hotline is open Monday through Friday, excluding Federal holidays, from 9:00 am to 5:30 pm Eastern Time. For technical inquiries, contact Thomas Grubbs or William Hamele, Office of Ground Water and Drinking Water (MC 4607), U.S. Environmental Protection Agency, 401 M Street SW, Washington DC 20460; telephone (202) 260-7270 (Grubbs) or (202) 260-2584 (Hamele). Regional Contacts I. Kevin Reilly, Water Supply Section, JFK Federal Bldg., Room 203, Boston, MA 02203, (617) 565-3616 II. Michael Lowy, Water Supply Section, 290 Broadway, 24th Floor, New York, NY 10007-1866, (212) 637-3830 III. Jason Gambatese, Drinking Water Section (3WM41), 841 Chestnut Building, Philadelphia, PA 19107, (215) 566-5759 IV. David Parker, Water Supply Section, 345 Courtland Street, Atlanta, GA 30365, (404) 562-9460 V. Kimberly Harris (micro), Miguel Del Toral (DBP), Water Supply Section, 77 W. Jackson Blvd., Chicago, IL 60604, (312) 886-4239 (Harris), (312) 886-5253 (Del Toral) VI. Blake L. Atkins, Team Leader, Water Supply Section, 1445 Ross Avenue, Dallas, TX 75202, (214) 665-2297 VII. Stan Calow, State Programs Section, 726 Minnesota Ave., Kansas City, KS 66101, (913) 551-7410 VIII. Bob Clement, Public Water Supply Section, (8WM-DW), 999 18th Street, Suite 500, Denver, CO 80202-2466, (303) 312-6653 IX. Bruce Macler, Water Supply Section, 75 Hawthorne Street, San Francisco, CA 94105, (415) 744-1884 X. Wendy Marshall, Drinking Water Unit, 1200 Sixth Avenue (OW-136), Seattle, WA 98101, (206) 553-1890 SUPPLEMENTARY INFORMATION: Regulated Entities Entities potentially regulated by the Stage 1 DBPR are public water systems that add a disinfectant or oxidant. Regulated categories and entities include: ------------------------------------------------------------------------ Examples of regulated Category entities ------------------------------------------------------------------------ Public Water System....................... Community water systems that add disinfectant or oxidant. State Governments......................... State government offices that regulate drinking water. ------------------------------------------------------------------------ This table is not intended to be exhaustive, but rather provides a guide for readers regarding entities likely to be regulated by the Stage 1 DBPR. This table lists the types of entities that EPA is now aware could potentially be regulated by the rule. Other types of entities not listed in this table could also be regulated. To determine whether your facility may be regulated by this action, you should carefully examine the applicability criteria in Sec. 141.130 of the proposed rule published on July 29, 1994 at 59 FR 38668 (USEPA, 1994b). If you have questions regarding the applicability of this action to a particular entity, contact one of the persons listed in the preceding FOR FURTHER INFORMATION CONTACT section. Additional Information for Commenters The Agency requests that commenters follow the following format: type or print comments in ink, and cite, where possible, the paragraph(s) in this Notice to which each comment refers. Commenters should use a separate paragraph for each method or issue discussed. Electronic comments must be submitted as a WP5.1 or WP6.1 file or as an ASCII file avoiding the use of special characters and any form of name [[Page 59389]] or title of the Federal Register. Comments and data will also be accepted on disks in WordPerfect in 5.1 or WP6.1 or ASCII file format. Electronic comments on this Notice may be filed online at many Federal Depository Libraries. Commenters who want EPA to acknowledge receipt of their comments should include a self-addressed, stamped envelope. No facsimiles (faxes) will be accepted. Availability of Record The record for this Notice, which includes supporting documentation as well as printed, paper versions of electronic comments, is available for inspection from 9 to 4 p.m., Monday through Friday, excluding legal holidays at the Water Docket, U.S. EPA Headquarters, 401 M. St., S.W. Washington, D.C. 20460. For access to docket materials, please call 202/260-3027 to schedule an appointment and obtain the room number. Copyright Permission Supporting documentation reprinted in this document from copyrighted material may be reproduced or republished without restriction in accordance with 1 CFR 2.6. Abbreviations Used in This Notice AOC: Assimilable organic carbon ASDWA: Association of State Drinking Water Administrators AWWA: American Water Works Association AWWARF: AWWA Research Foundation AWWSCo: American Water Works Service Company BAC: Biologically active carbon BAF: Biologically active filtration BAT: Best Available Technology BCAA: Bromochloroacetic acid BDOC: Biodegradable organic carbon CT: Contact time CWS: Community Water System DBP: Disinfection byproducts D/DBP: Disinfectants and disinfection byproducts DBPRAM: DBP Regulatory Analysis Model DOC: Dissolved Organic Carbon EPA: United States Environmental Protection Agency ESWTR: Enhanced Surface Water Treatment Rule FACA: Federal Advisory Committee Act FY: Fiscal year GAC: Granular Activated Carbon GWDR: Ground Water Disinfection Rule HAA5: Haloacetic acids (five) IC: Ion chromotography ICR: Information Collection Rule ILSI: International Life Sciences Institute IOC: Inorganic chemical LOAEL: Lowest observed adverse effect level MCL: Maximum Contaminant Level (expressed as mg/l, 1,000 micrograms (g)=1 milligram (mg)) MCLG: Maximum Contaminant Level Goal M-DBP: Microbial and Disinfectants/Disinfection Byproducts MDL: Method Detection Limit mg/dl: Milligrams per deciliter mg/L: Milligrams per liter MGD: Million Gallons per Day MRDL: Maximum Residual Disinfectant Level (as mg/l) MRDLG: Maximum Residual Disinfectant Level Goal MWDSC: Metropolitan Water District of Southern California NCI: National Cancer Institute NIPDWR: National Interim Primary Drinking Water Regulation NOAEL: No observed adverse effect level NOM: Natural Organic Matter NPDWR: National Primary Drinking Water Regulation NTNCWS: Nontransient noncommunity water system O&M: Operations and maintenance PE: Performance evaluation PODR: Point of Diminishing Returns POE: Point-of-Entry Technologies POU: Point-of-Use Technologies ppb: Parts per billion PQL: Practical Quantitation Level PWS: Public Water System RIA: Regulatory Impact Analysis RMCL: Recommended Maximum Contaminant Level SAB: Science Advisory board SDWA: Safe Drinking Water Act, or the ``Act,'' as amended in 1986 SUVA: Specific ultraviolet absorbance at 254 nm SWTR: Surface Water Treatment Rule TOC: Total organic carbon TTHM: Total trihalomethanes TWG: Technical Working Group UNC: University of North Carolina VOC: Volatile Synthetic Organic Chemical WIDB: Water Industry Data Base WITAF: Water Industry Technical Action Fund Table of Contents I. Introduction and Background A. Existing Regulations 1. Surface Water Treatment Rule 2. Total trihalomethane MCL 3. Total Coliform Rule 4. Information Collection Rule B. Public Health Concerns to be Addressed C. Statutory Provisions 1. SDWA and 1986 provisions 2. Changes to initial provisions and new mandates D. Regulatory Negotiation Process E. Information Collection Rule F. Formation of 1997 Federal Advisory Committee G. Overview of 1994 DBP Proposal 1. MCLGs/MCLs/MRDLGs/MRDLs 2. Best available technologies 3. Treatment technique 4. Preoxidation (predisinfection) credit 5. Analytical methods 6. New information II. Health Effects A. Cancer Epidemiology Studies 1. Expert panels recommendations on cancer epidemiology 2. Implementation of expert panel recommendations a. Improve exposure assessments/geographic identification studies/classes of DBPs other than THMs b. Meta-analysis of existing cancer epidemiology data B. Reproductive and Developmental Epidemiology Studies 1. Improving exposure assessments 2. New studies since proposal C. Significant New Toxicological Information for Stage 1 Disinfectants and Disinfection Byproducts 1. Chlorite 2. Chlorine dioxide 3. Trihalomethanes 4. Haloacetic acids 5. Chloral hydrate 6. Bromate D. Summary of Key Observations E. Request for Public Comments III. Enhanced Coagulation and Enhanced Softening A. 1994 Enhanced Coagulation and Enhanced Softening Proposal B. New Information on Enhanced Coagulation and Softening Since 1994 Proposal 1. New Data on enhanced coagulation a. UNC Enhanced Coagulation Study b. Metropolitan Water District of Southern California WDSC/ ColoradoUniversity Enhanced Coagulation Study c. Malcolm Pirnie, Inc./Colorado University data collection and analysis d. Evaluation of current (baseline) TOC removals at full scale e. Evaluation of ``optimized'' TOC removal f. ``Case-by-case'' data analyses 2. New data on enhanced softening a. AWWARF Studies--data on TOC removal b. Shorney and Coworkers--data on the use of SUVA c. Malcolm Pirnie, Inc. modeling d. ICR mail survey C. Summary of Key Enhanced Coagulation and Enhanced Softening Observations D. Request for Public Comment on Enhanced Coagulation and Enhanced Softening Issues IV. Predisinfection Credit A. 1994 Proposal B. New Information Since 1994 Proposal 1. ICR mail survey--predisinfection practices 2. Summers et al.--Impact of chlorination point on DBP production C. Summary of Key Observations D. Request for Public Comments V. Analytical Methods [[Page 59390]] A. Chlorine Dioxide B. Haloacetic Acids C. Total Trihalomethanes (TTHMs) D. Bromate E. Chlorite F. Total Organic Carbon (TOC) G. Specific Ultraviolet Absorbance (SUVA) H. Summary of Key Observations I. Request for Public Comments VI. MCLs for TTHMs, HAAs, Chlorite, and Bromate A. 1994 Proposal B. New Information Since 1994 Proposal 1. TTHM and HAA5 MCLs 2. Bromate 3. Chlorite VII. Regulatory Compliance Schedule and Other Compliance-related Issues A. Regulatory Compliance Schedule B. Compliance violations and State primacy obligations C. Compliance with current regulations VIII. Economic Analysis of the M-DBP Advisory Committee Recommendations A. Plant-level DBP Treatment Effectiveness and Cost B. Decision Tree Analysis--Compliance Forecasts C. National Cost Estimates 1. System level costs 2. Household costs 3. Monitoring and State implementation costs D. DBP Exposure Estimates E. National Benefits Analysis F. Cost-Effectiveness G. Summary of Key Observations H. Request for Public Comments IX. National Technology Transfer and Advancement Act X. References I. Introduction and Background A. Existing Regulations 1. Surface Water Treatment Rule Under the Surface Water Treatment Rule (SWTR)(USEPA, 1989a), USEPA set maximum contaminant level goals of zero for Giardia lamblia, viruses, and Legionella; and promulgated national primary drinking water regulations for all public water systems (PWSs) using surface water sources or ground water sources under the direct influence of surface water. The SWTR includes treatment technique requirements for filtered and unfiltered systems that are intended to protect against the adverse health effects of exposure to Giardia lamblia, viruses, and Legionella, as well as many other pathogenic organisms. Briefly, those requirements include (1) removal or inactivation of 3 logs (99.9%) for Giardia and 4 logs (99.99%) for viruses (2) combined filter effluent performance of 5 NTU as a maximum and 0.5 NTU at 95th percentile monthly, based on 4-hour monitoring for treatment plants using conventional treatment or direct filtration (with separate standards for other filtration technologies); and (3) watershed protection and other requirements for unfiltered systems. 2. Total trihalomethane MCL USEPA set an interim maximum contaminant level (MCL) for total trihalomethanes (TTHMs) of 0.10 mg/l as an annual average in November 1979 (USEPA, 1979). This standard was based on the need to balance the requirement for continued disinfection of water to reduce exposure to pathogenic microorganisms while simultaneously lowering exposure to disinfection byproducts which might be carcinogenic to humans. The interim TTHM standard only applies to any PWSs (surface water and/or ground water) serving at least 10,000 people that add a disinfectant to the drinking water during any part of the treatment process. At their discretion, States may extend coverage to smaller PWSs. However, most States have not exercised this option. About 80 percent of the PWSs, serving populations of less than 10,000, are served by ground water that is generally low in THM precursor content (USEPA, 1979) and which would be expected to have low TTHM levels even if they disinfect. 3. Total Coliform Rule The Total Coliform Rule (USEPA, 1989b) was revised in June 1989, and became effective on December 31, 1990. The rule, which applies to all public water systems, sets compliance with the maximum contaminant level (MCL) for total coliforms as follows. For systems that collect 40 or more samples per month, no more than 5.0% of the samples may be total coliform-positives; for those that collect fewer than 40 samples, only one sample may be total coliform-positive. If a system exceeds the MCL for a month, it must notify the public using mandatory language developed by the USEPA. The required monitoring frequency for a system ranges from 480 samples per month for the largest systems to once annually for certain of the smallest systems. All systems must have a written plan identifying where samples are to be collected. In addition, systems are required to conduct repeat sampling after a positive sample. The Total Coliform Rule also requires each system that collects fewer than five samples per month to have the system inspected every 5 years (10 years for certain types of systems using only protected and disinfected ground water.) This on-site inspection (referred to as a sanitary survey) must be performed by the state or by an agent approved by the state. 4. Information Collection Rule The Information Collection Rule (ICR) is a monitoring and data reporting rule that was promulgated on May 14, 1996 (USEPA, 1996b). The purpose of the ICR is to collect occurrence and treatment information to evaluate the need for possible changes to the current Surface Water Treatment Rule and existing microbial treatment practices and to evaluate the need for future regulation for disinfectants and DBPs. The ICR will provide USEPA with additional information on the national occurrence in drinking water of (1) chemical byproducts that form when disinfectants used for microbial control react with compounds already present in source water and (2) disease-causing microorganisms, including Cryptosporidium, Giardia, and viruses. The ICR will also collect engineering data on how PWSs currently control such contaminants. This information is being collected because the regulatory negotiation on disinfectants and DBPs concluded that additional information was needed to assess the potential health problem created by the presence of DBPs and pathogens in drinking water and to assess the extent and severity of risk in order to make sound regulatory and public health decisions. The ICR will also provide information to support regulatory impact analyses for various regulatory options, and to help develop monitoring strategies for cost effectively implementing regulations. B. Public Health Concerns To Be Addressed In 1990, USEPA's Science Advisory Board, an independent panel established by Congress, cited drinking water contamination as one of the highest ranking environmental risks. The Science Advisory board reported that microbiological contaminants (e.g. bacteria, protozoa, viruses) are likely the greatest remaining health risk management challenge for drinking water suppliers. The control of microbiological contaminants is further complicated because commonly-used disinfection processes themselves may pose health risks. Conventional practices require the addition of disinfectant chemicals to the water that, while effective in controlling many harmful microorganisms, combine with organic matter in the water and form compounds known as disinfection byproducts (DBPs). One of the most complex questions facing water supply professionals is how to minimize the risks from these DBPs and still control microbial contaminants. Chemical disinfectants (e.g., chlorine, chloramines, chlorine dioxide) are [[Page 59391]] added to drinking water to provide continuous disinfection throughout the distribution system. There is generally little health concern over exposure to the levels of the disinfectant residuals commonly found in finished drinking water. A number of organic DBPs, including some trihalomethanes (chloroform, bromoform, and bromodichloromethane) and some haloacetic acids (e.g., dichloroacetic acid) cause cancer in laboratory animals. Other DBPs cause reproductive or developmental effects in laboratory animals (e.g., chlorite). Bromate, a byproduct of ozonation, causes cancer in laboratory animals. Several epidemiology studies have evaluated the association of chlorination and chloramination with several adverse outcomes including cancer, cardiovascular disease, and adverse reproductive outcomes. Several studies have reported small increases in bladder, colon, and rectal cancers. In some cases, these effects appeared to be associated with the duration of exposure and volume of water consumed. Data on DBPs and cardiovascular disease are inconclusive. Animal studies in the mid 1980's indicated a potential increase in the serum lipid levels in animals exposed to chlorinated water. However, in a cross-sectional epidemiology study in humans, comparing chlorinated and unchlorinated water supplies with varying water hardness, no adverse effects on serum lipid levels were found. Recent epidemiology studies have reported increased incidence of decreased birth weight, premature births, intrauterine growth retardation, and neural tube defects with chlorinated water. As with the other reported adverse outcomes from the epidemiology studies, there is considerable debate in the scientific community on the significance of these findings (USEPA, 1994a). A discussion of new health effects information that has become available since the 1994 proposal appears in Section VI of this Notice. In order to accurately assess risk from DBPs, it is important to have information on human exposure to DBPs, information on the toxicity of the DBPs and an understanding of the mode of action of toxicity. The preamble to the 1994 proposed DBP rule presented information on the occurrence and exposure to the Stage 1 DBPs. The information presented in that preamble was summarized from the document ``Occurrence Assessment for Disinfectants and Disinfection By-products (Phase 6a) in Drinking Water'' (USEPA, 1992a) and from information presented as a part of the 1992 and 1993 Regulatory Negotiation process that led to the 1994 Stage 1 DBP proposal (see section D below). Since the proposal, USEPA has updated the document cited above with new occurrence and exposure information. Copies of the revised document, entitled ``Occurrence Assessment for Disinfectants and Disinfection Byproducts in Public Drinking Water Supplies'' (USEPA, 1997a) can be obtained from the Docket for this Notice. The Information Collection Rule (ICR) (USEPA, 1996b) will supply additional information on the occurrence of DBPs for the Stage 2 DBP rule; however, this ICR information will not be available in time for the Stage 1 DBP rule. C. Statutory Provisions 1. SDWA and 1986 Provisions The Safe Drinking Water Act (SDWA or the Act), as amended in 1986, requires USEPA to publish a ``maximum contaminant level goal'' (MCLG) for each contaminant which, in the judgement of the USEPA Administrator, ``may have any adverse effect on the health of persons and which are known or anticipated to occur in public water systems'' (Section 1412(b)(3)(A)). MCLGs are to be set at a level at which ``no known or anticipated adverse effect on the health of persons occur and which allows an adequate margin of safety'' (Section 1412(b)(4)). The Act also requires that at the same time USEPA publishes an MCLG, which is a non-enforceable health goal, it also must publish a National Primary Drinking Water Regulation (NPDWR) that specifies either a maximum contaminant level (MCL) or treatment technique (Sections 1401(1) and 1412(a)(3)). USEPA is authorized to promulgate a NPDWR ``that requires the use of a treatment technique in lieu of establishing a MCL,'' if the Agency finds that ``it is not economically or technologically feasible to ascertain the level of the contaminant''. Section 1414(c) of the Act requires each owner or operator of a public water system to give notice to the persons served by the system of any failure to comply with an MCL or treatment technique requirement of, or testing procedure prescribed by, a NPDWR and any failure to perform monitoring required by section 1445 of the Act. Section 1412(b)(7)(C) of the SDWA requires the USEPA Administrator to publish a NPDWR ``specifying criteria under which filtration (including coagulation and sedimentation, as appropriate) is required as a treatment technique for public water systems supplied by surface water sources''. In establishing these criteria, USEPA is required to consider ``the quality of source waters, protection afforded by watershed management, treatment practices (such as disinfection and length of water storage) and other factors relevant to protection of health''. This section of the Act also requires USEPA to promulgate a NPDWR requiring disinfection as a treatment technique for all public water systems and a rule specifying criteria by which variances to this requirement may be granted. 2. Changes to Initial Provisions and New Mandates In 1996, Congress reauthorized the Safe Drinking Water Act. Several of the 1986 provisions discussed above were renumbered and augmented with additional language, while other sections mandate new drinking water requirements. These modifications, as well as new provisions, are detailed below. As part of the 1996 amendments to the Safe Drinking Water Act (the Amendments), USEPA's general authority to set a MCLG and NPDWR was modified to apply to contaminants that may ``have an adverse effect on the health of persons'', that are ``known to occur or there is a substantial likelihood that the contaminant will occur in public water systems with a frequency and at levels of public health concern'', and for which ``in the sole judgement of the Administrator, regulation of such contaminant presents a meaningful opportunity for health risk reduction for persons served by public water systems' (1986 SDWA Section 1412 (b)(3)(A) stricken and amended with 1412(b)(1)(A)). The Amendments also require that USEPA, when proposing a NPDWR that includes an MCL or treatment technique, publish and seek public comment on health risk reduction and cost analyses. The Amendments also require USEPA to take into consideration the effects of contaminants upon sensitive subpopulations (i.e. infants, children, pregnant women, the elderly, and individuals with a history of serious illness), and other relevant factors. (Section 1412 (b)(3)(C)). The 1996 Amendments also newly require USEPA to promulgate an Interim Enhanced SWTR and a Stage I Disinfectants and Disinfection Byproducts Rule by November 1998. In addition, the 1996 Amendments require USEPA to promulgate a Final Enhanced SWTR and a Stage 2 Disinfection Byproducts Rule by November 2000 and May 2002, respectively (Section 1412(b)(2)(C)). [[Page 59392]] Under the Amendments of 1996, recordkeeping requirements were modified to apply to ``every person who is subject to a requirement of this title or who is a grantee'' (Section 1445 (a)(1)(A)). Such persons are required to ``establish and maintain such records, make such reports, conduct such monitoring, and provide such information as the Administrator may reasonably require by regulation * * *''. D. Regulatory Negotiation Process In 1992 USEPA initiated a negotiated rulemaking to develop a disinfectants/disinfection byproducts rule. The negotiators included representatives of State and local health and regulatory agencies, public water systems, elected officials, consumer groups and environmental groups. The Committee met from November 1992 through June 1993. Early in the process, the negotiators agreed that large amounts of information necessary to understand how to optimize the use of disinfectants to concurrently minimize microbial and DBP risk on a plant-specific basis were unavailable. Nevertheless, the Committee agreed that USEPA propose a Disinfectant/Disinfection Byproducts rule to extend coverage to all community and nontransient noncommunity water systems that use disinfectants. This rule proposed to reduce the current TTHM MCL, regulate additional disinfection byproducts, set limits for the use of disinfectants, and reduce the level of organic compounds in the source water that may react with disinfectants to form byproducts. One of the major goals addressed by the Committee was to develop an approach that would reduce the level of exposure from disinfectants and DBPs without undermining the control of microbial pathogens. The intention was to ensure that drinking water is microbiologically safe at the limits set for disinfectants and DBPs and that these chemicals do not pose an unacceptable risk at these limits. Following months of intensive discussions and technical analysis, the Committee recommended the development of three sets of rules: a two-staged Disinfectants/Disinfection Byproduct Rule (proposal: 59 FR 38668, July 29, 1994), an ``interim'' ESWTR (proposal: 59 FR 38832, July 29, 1994), and an Information Collection rule (proposal: 59 FR 6332, February 10, 1994). The IESWTR would only apply to systems serving 10,000 people or more. The Committee agreed that a ``long- term'' ESWTR (LTESWTR) would be needed for systems serving fewer than 10,000 people when the results of more research and water quality monitoring became available. The LTESWTR could also include additional refinements for larger systems. The approach in developing these proposals considered the constraints of simultaneously treating water to control for both microbial contaminants and DBPs. As part of this effort, the Negotiating Committee concluded that the SWTR may need to be revised to address health risk from high densities of pathogens in poorer quality source waters and from the protozoan, Cryptosporidium. The Committee also agreed that the schedules for IESWTR and LTESWTR should be ``linked'' to the schedule for the Stage 1 DBP Rule to assure simultaneous compliance and a balanced risk-risk based implementation. The Committee agreed that additional information on health risk, occurrence, treatment technologies, and analytical methods needed to be developed in order to better understand the risk-risk tradeoff, and how to accomplish an overall reduction in risk. Finally the Negotiating Committee agreed that to develop a reasonable set of rules and to understand more fully the limitations of the current SWTR, additional field data were critical. Thus, a key component of the regulation negotiation agreement was the promulgation of the Information Collection Rule (ICR) noted above and described in more detail below. E. Information Collection Rule As stated above, the ICR established monitoring and data reporting requirements for large public water systems serving populations over 100,000. About 350 PWSs operating 500 treatment plants are involved in the data collection effort. Under the ICR, these PWSs monitor their source water for bacteria, viruses, and protozoa (surface water sources only); water quality factors affecting DBP formation; and DBPs within the treatment plant and in the distribution system. In addition, PWSs must provide operating data and a description of their treatment plan design. Finally, a subset of PWSs perform treatment studies, using either granular activated carbon or membrane processes, to evaluate DBP precursor removal. Monitoring for treatment study applicability began in September 1996. The remaining occurrence monitoring began in July 1997. The initial intent of the ICR was to collect monitoring data and other information for use in developing the Stage 2 DBPR and IESWTR and to estimate national costs for various treatment options. However, because of delays in promulgating the ICR and technical difficulties associated with laboratory approval and review of facility sampling plans, most ICR monitoring did not begin until July 1, 1997. As a result of this delay and the new Stage 1 DBPR and IESWTR deadlines specified in the 1996 SDWA amendments, ICR data will not be available for analysis in connection with these rules. In place of the ICR data, the Agency has worked with stakeholders to identify additional data developed since 1994 that can be used in components of these rules. USEPA intends to continue to work with stakeholders in analyzing and using the comprehensive ICR data and research for developing subsequent revisions to the SWTR and the Stage 2 DBP Rule. F. Formation of 1997 Federal Advisory Committee In May 1996, the Agency initiated a series of public informational meetings to exchange information on issues related to microbial and disinfectants/disinfection byproducts regulations. To help meet the deadlines for the IESWTR and Stage 1 DBPR established by Congress in the 1996 SDWA Amendments and to maximize stakeholder participation, the Agency established the Microbial and Disinfectants/Disinfection Byproducts (M-DBP) Advisory Committee under the Federal Advisory Committee Act (FACA) on February 12, 1997, to collect, share, and analyze new information and data, as well as to build consensus on the regulatory implications of this new information. The Committee consists of 17 members representing USEPA, State and local public health and regulatory agencies, local elected officials, drinking water suppliers, chemical and equipment manufacturers, and public interest groups. The Committee met five times, in March through July 1997, to discuss issues related to the IESWTR and Stage 1 DBPR. Technical support for these discussions was provided by a Technical Work Group (TWG) established by the Committee at its first meeting in March 1997. The Committee's activities resulted in the collection, development, evaluation, and presentation of substantial new data and information related to key elements of both proposed rules. The Committee reached agreement on the following major issues discussed in this Notice and the Notice for the IESWTR published elsewhere in today's Federal Register: (1) MCLs for TTHMs, HAA5 and bromate; (2) requirements for enhanced coagulation and enhanced softening (as part of DBP control); (3) microbial benchmarking/profiling to [[Page 59393]] 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; (4) disinfection credit; (5) turbidity; (6) Cryptosporidium MCLG; (7) removal of Cryptosporidium; (8) role of Cryptosporidium inactivation as part of a multiple barrier concept and (9) sanitary surveys. The Committee's recommendations to USEPA on these issues were set forth in an Agreement In Principle document dated July 15, 1997. This document is included with this Notice as Appendix 1. G. Overview of 1994 DBP Proposal The proposed Disinfectants and Disinfection Byproducts Stage I Rule (DBPI) addressed a number of complex and interrelated drinking water issues. The proposal attempted to balance the control of health risks from compounds formed during drinking water disinfection against the risks from microbial organisms (such as Giardia lamblia, Cryptosporidium, bacteria, and viruses) to be controlled by the IESWTR. The proposed Stage 1 DBP rule applied to all community water systems (CWSs) and nontransient noncommunity water systems (NTNCWSs) that treat their water with a chemical disinfectant for either primary or residual treatment. In addition, certain requirements for chlorine dioxide would apply to transient noncommunity water systems because of the short-term health effects from high levels of chlorine dioxide. Following is a summary of key components of the 1994 Stage 1 DBPR proposal. 1. MCLGs/MCLs/MRDLGs/MRDLs EPA proposed MCLGs of zero for chloroform, bromodichloromethane, bromoform, bromate, and dichloroacetic acid and MCLGs of 0.06 mg/L for dibromochloromethane, 0.3 mg/L for trichloroacetic acid, 0.04 mg/L for chloral hydrate, and 0.08 mg/L for chlorite. In addition, EPA proposed to lower the MCL for TTHMs from 0.10 to 0.080 mg/L and added an MCL for five haloacetic acids (i.e., the sum of the concentrations of mono-, di-, and trichloroacetic acids and mono-and dibromoacetic acids) of 0.060 mg/L. EPA also, for the first time, proposed MCLs for two inorganic DBPs: 0.010 mg/L for bromate and 1.0 mg/L for chlorite. In addition to proposing MCLGs and MCLs for several DBPs, EPA proposed maximum residual disinfectant level goals (MRDLGs) of 4 mg/L for chlorine and chloramines and 0.3 mg/L for chlorine dioxide. The Agency also proposed maximum residual disinfectant levels (MRDLs) for chlorine and chloramines of 4.0 mg/L, and 0.8 mg/L for chlorine dioxide. MRDLs protect public health by setting limits on the level of residual disinfectants in the distribution system. MRDLs are similar in concept to MCLs--MCLs set limits on contaminants and MRDLs set limits on residual disinfectants in the distribution system. MRDLs, like MCLs, are enforceable, while MRDLGs, like MCLGs, are not enforceable. 2. Best Available Technologies EPA identified the best available (BAT) technology for achieving compliance with the MCLs for both TTHMs and HAA5 as enhanced coagulation or treatment with granular activated carbon with a ten minute empty bed contact time and 180 day reactivation frequency (GAC10), with chlorine as the primary and residual disinfectant. The BAT for achieving compliance with the MCL for bromate was control of ozone treatment process to reduce formation of bromate. The BAT for achieving compliance with the chlorite MCL was control of precursor removal treatment processes to reduce disinfectant demand, and control of chlorine dioxide treatment processes to reduce disinfectant levels. EPA identified BAT for achieving compliance with the MRDL for chlorine, chloramine, and chlorine dioxide as control of precursor removal treatment processes to reduce disinfectant demand, and control of disinfection treatment processes to reduce disinfectant levels. 3. Treatment Technique EPA proposed a treatment technique that would require surface water systems and groundwater systems under the direct influence of surface water that use conventional treatment or precipitative softening to remove DBP precursors by enhanced coagulation or enhanced softening. A system would have been required to remove a certain percentage of TOC (based on raw water quality) prior to the point of continuous disinfection. EPA also proposed a procedure to be used by a PWS not able to meet the percent reduction, to allow them to comply with an alternative minimum TOC removal level. Compliance for systems required to operate with enhanced coagulation or enhanced softening was based on a running annual average, computed quarterly, of normalized monthly TOC percent reductions. A complete discussion of the proposed requirements is in Section III.A. 4. Preoxidation (Predisinfection) Credit The proposed rule did not allow PWSs required to use enhanced coagulation or enhanced softening to take credit for compliance with disinfection requirements in the SWTR/IESWTR prior to removing required levels of precursors unless they met specified criteria. These criteria are explained in Section IV.A. 5. Analytical Methods EPA proposed nine analytical methods (some of which can be used for multiple analytes) to ensure compliance with proposed MRDLs for chlorine, chloramines, and chlorine dioxide. The three disinfectant residuals were measured and reported as: chlorine as free chlorine (four methods) or total chlorine (five methods); chloramines as combined chlorine (three methods) or total chlorine (five methods); and chlorine dioxide as chlorine dioxide (3 methods). EPA proposed methods for the analysis of two classes of organic DBPs: TTHMs (three methods) and HAA5 (2 methods). In addition, EPA proposed one method for measuring both inorganic DBPs (chlorite and bromate) and two methods for total organic carbon (TOC). 6. New Information Since July, 1994, new information has become available in several key areas related to issues put forth in the DBP Stage 1 proposal. The key issues where new information has become available since the proposal include the following: (1) MCLs; (2) Enhanced Coagulation and Enhanced Softening; (3) Predisinfection Credit; (4) Health Effects Information; (5) Analytical Methods; and (6) the Regulatory Impact Analysis (DBP and TOC occurrence, compliance decision tree). This information and its implications are discussed in more detail below. II. Health Effects The preamble to the 1994 proposed rule provided a summary of the health criteria documents for bromate; chloramines; haloacetic acids and chloral hydrate; chlorine; chlorine dioxide, chlorite, and chlorate; and trihalomethanes. The information presented in the proposal was used to establish MCLGs and MRDLGs for the disinfectants and DBPs listed above. Since the 1994 proposal, several epidemiology and toxicology studies have been completed. The study results need to be considered for the final Stage 1 DBPR. The following section briefly [[Page 59394]] discusses the new epidemiological and laboratory toxicology studies. In addition, USEPA has developed summaries of this new information and included these documents in the Docket for this action as ``Summaries of New Health Effects Data'' (USEPA, 1997b). A. Cancer Epidemiology Studies The preamble to the proposed rule discussed several cancer epidemiology studies that had been conducted over the past 20 years on chlorinated drinking water (see USEPA, 1994b). At the time of the proposed rule, there was disagreement among the members of the Negotiating Committee on the conclusions to be drawn from the cancer epidemiology studies. Some members of the Committee felt that the cancer epidemiology data, taken in conjunction with the results from toxicological studies, provide an ample and sufficient weight of evidence to conclude that exposure to DBPs in drinking water could result in an increased cancer risk at levels encountered in some public water supplies. Other members of the Committee concluded that the degree of resolution in cancer epidemiology studies on the consumption of chlorinated drinking water to date was insufficient to provide definitive information for the regulation. USEPA, therefore, agreed to pursue additional research to reduce the uncertainties associated with these epidemiology data and to better characterize and project the potential human cancer risks associated with the consumption of chlorinated drinking water. To implement this commitment, USEPA sponsored two expert panel reviews on the state of cancer epidemiology. Each of these panels recommended short and long-term research for improving the assessment of risks using cancer epidemiology. 1. Expert Panels Recommendations on Cancer Epidemiology USEPA conducted an expert panel workshop in July 1994 on the scientific considerations for conducting cancer epidemiologic studies for DBPs (USEPA, 1994a). The expert panel presented the following conclusions. (A)lthough ecological and analytic epidemiologic studies have reported associations between chlorinated water and cancer at various sites, many of the studies have methodologic problems or systematic biases that limit the interpretation of results. Moreover, the studies vary according to the amount of information available on exposure to chlorinated water or DBPs. The panel agrees that existing epidemiologic data are insufficient to conclude that the reported associations are causal or provide an accurate estimate of the magnitude of risk. This cancer workshop panel also provided several recommendations for conducting additional research. These included: (1) improving exposure assessments; (2) conducting a reanalysis of previously conducted interview-based case control studies using improved exposure estimates and analytical methods to determine the validity of these risks and to address confounding factors and bias not adequately excluded in previous reports such as the meta-analysis completed by Morris, et al. (1992) discussed in the 1994 proposed rule (USEPA, 1994b, page 38689); (3) conducting feasibility studies to identify geographic locations with adequate exposure data and appropriate cohorts for study (including the possibility of using existing cohorts that are being studied for other potential exposures); and (4) consideration of several possible designs for full scale studies (i.e., cohort, case-control, and case-control nested within a cohort). In October 1995, the International Life Sciences Institute (ILSI) sponsored a workshop on ``Disinfection by-products in Drinking Water: Critical Issues in Health Effects Research'' (ILSI, 1995). One of the panels at the workshop provided a brief summary of the findings from cancer epidemiology studies and made recommendations for further research in this area. The panel concluded that the epidemiological studies of bladder and colorectal cancer have generally shown an increased risk associated with the consumption of chlorinated surface water, although a causal association has not been conclusively established. The panel made several recommendations for future research including the need to conduct hypothesis driven cancer epidemiological studies to examine the risk of classes of DBPs other than THMs and to support these studies with improved exposure assessments. 2. Implementation of Expert Panel Recommendations a. Improve Exposure Assessments/Geographic Identification Studies/ Classes of DBPs Other Than THMs. USEPA, in conjunction with other parties, has begun research to provide the tools needed to improve exposure assessments for epidemiology studies. USEPA is supporting studies in Colorado, North Carolina, and New Jersey that will provide improved tools for conducting exposure assessments for epidemiology studies. While the results from these studies will not be available for the final Stage 1 DBP rule, they will be very useful in designing future epidemiology studies. In addition to USEPA's research, the Microbial/DBP Research Council (M/DBP Council) is funding a study on ``Identification of Geographic Areas for Possible Epidemiological Studies'' and is evaluating several proposals for a project on ``Development of Methods for Predicting THM and HAA Concentrations in Exposure Assessment Studies.'' The M/DBP Council was formed as a joint USEPA and American Water Works Association Research Foundation (AWWARF) project to identify and fund critical research. This research, in conjunction with the USEPA research discussed above, will improve the understanding of risks associated with the consumption of chlorinated surface water. However, as with USEPA's work, this research will not be completed in time to impact the Stage 1 DBPR. b. Meta-analysis of Existing Cancer Epidemiology Data. The 1994 proposal includes results of a meta-analysis that pooled the relative risks from 10 cancer epidemiology studies in which there was a presumed exposure to chlorinated water and its byproducts (Morris et al., 1992). This meta-analysis estimated that approximately 10,000 cancer cases each year could be attributed to the consumption of chlorinated drinking water and its byproducts. As discussed in the preamble to the proposed rule, this study generated considerable debate among the members of the Negotiation Committee. An evaluation of the Morris et al. meta-analysis has been recently completed for USEPA. USEPA is currently evaluating this report and will provide an opportunity to comment on EPA's assessment and implications for the regulatory provisions for the final Stage 1 DBPR. In addition to the meta-analysis, USEPA has summarized several new cancer epidemiology studies and included them as part of the ``Summaries of New Health Effects Data'' (USEPA, 1997b) that is included in the Docket for this Notice. USEPA will be evaluating the data from the new epidemiology studies and will provide an opportunity to comment on the potential implications of these new studies for the regulatory provisions for the final Stage 1 DBPR. B. Reproductive and Developmental Epidemiology Studies The preamble to the 1994 proposal discussed several reproductive epidemiology studies that had been conducted (see USEPA, 1994b, page 38690). It also included a discussion of an USEPA and ILSI expert panel that reviewed the published epidemiologic and experimental data on reproductive [[Page 59395]] and developmental effects and a strategy developed by the panel for related short-term and long-term research (USEPA, 1993b). The panel concluded that the currently available data on the effects of chlorination byproducts provide an inadequate basis for identifying DBPs as a reproductive or developmental hazard. Recommendations were made for refining studies using existing data bases, strengthening studies designed to collect new data, improving exposure assessments, investigating selected health endpoints, and developing a stronger link between animal research and epidemiology studies. The results from the ILSI expert panel, and additional information provided since the 1994 proposal, are summarized in Reif et al. (1996). This paper reviewed the available epidemiological data on the reported association between the consumption of chlorinated drinking water and reproductive and developmental effects. The panel reached the following conclusions. ``The currently available human studies on effects of chlorination by-products provide an inadequate basis for identifying DBPs as a reproductive or developmental hazard. Nevertheless, additional laboratory animal and epidemiological research should be conducted, employing a coordinated multi disciplinary approach.'' They also provided recommendations for short-and longer-term research. 1. Improving Exposure Assessments Many of the exposure assessment projects identified above for cancer epidemiology are also relevant to improving exposure assessments for evaluating reproductive and developmental effects. As discussed in the cancer epidemiology section, while the results from these studies will not be available for the final Stage 1 DBPR, they will be very useful in designing future reproductive epidemiology studies. 2. New Studies Since Proposal Since the proposal, several new reproductive and developmental epidemiology studies have been published. Additionally, studies in California and Colorado are nearing completion, but results will not be available for this NODA. Savitz et al. (1995) used data from a population-based case-control study to evaluate the potential risk of miscarriage, preterm delivery and low birth weight in North Carolina based on water source, amount of water consumed, and TTHM concentration in water. The authors concluded, ``These data do not indicate a strong association between chlorinated byproducts and adverse pregnancy outcome, but given the limited quality of the exposure assessment and the increased miscarriage risk in the higher exposure group, more refined evaluation is warranted.'' Kanitz et al. (1996) conducted an epidemiology study in Italy on the association between somatic parameters (e.g., birthweight, body length, cranial circumference, and neonatal jaundice) and drinking water disinfection with chlorine dioxide and/or sodium hypochlorite. The authors concluded, ``The study provides some new information on the possible association between some drinking water disinfection treatments and somatic parameters of infants at birth. Further investigations will be needed to verify the results of the present study by rigorous exposure assessments.'' The 1994 proposed rule reported the results of a New Jersey Department of Health report on the results of a cross-sectional study evaluating the association between drinking water contaminants with low birth weight and selected birth defects (Bove et al., 1992a, 1992b). Since the proposal, an article summarizing the cross-sectional study has been published by Bove et al. (1995). The results are consistent with those reported in the proposed Stage 1 DBPR. The authors concluded, ``By itself, this study cannot resolve whether the drinking water contaminants caused the adverse birth outcomes; therefore, these findings should be followed up utilizing available drinking water contamination databases.'' While the new epidemiology studies add to the database on the potential reproductive and developmental effects from DBPs, USEPA believes that the results are inconclusive. A more complete discussion of the new reproductive and development epidemiology studies can be found in the ``Summaries of New Health Effects Data'' (USEPA, 1997b). C. Significant New Toxicological Information for the Stage 1 Disinfectants and Disinfection Byproducts Since the proposal, new toxicological information has become available for several of the disinfectants and DBPs. The information presented below is a summary of the significant new information for several disinfectants and DBPs. For a more complete discussion of the new information see the ``Summaries of New Health Effects Data'' (USEPA, 1997b) in the Docket (a summary of the new information for chlorine and chloramines is not included below, but is included in the document cited above.) 1. Chlorite The 1994 proposal included an MCLG of 0.08 mg/L and an MCL of 1.0 mg/L for chlorite. In order to fill an important data gap, the Chemical Manufacturers Association (CMA) agreed to conduct a two-generation reproductive effects study of chlorite. The Negotiating Committee agreed that if the studies indicated that a level of 1.0 mg/L of chlorite is safe, the MCL would remain at 1.0 mg/L. If the studies indicate that a level of 1.0 mg/L of chlorite is not safe or, if such a study is not conducted, the MCL would be re-evaluated. After the Negotiating Committee agreed to support a proposed MCL of 1.0 mg/L, USEPA selected developmental neurotoxicity hazard as the critical effect for chlorite (Mobley et al., 1990). Based on this 1990 rat developmental study, an MCLG of 0.08 mg/L was derived for chlorite. USEPA believed that the MCL of 1.0 mg/L agreed to by the Committee was not adequate to protect the public from the acute developmental health effects of chlorite. USEPA decided to propose an MCL of 1.0 mg/L to honor the agreement of the Committee and requested comment on several possible approaches for promulgating the final rule. Since the proposal, a study on the subchronic toxicity of sodium chlorite in rats (Harrington et al., 1995a) and a developmental toxicity study in rabbits (Harrington, et al., 1995b) have been published. Both of these studies reported no adverse toxicological effects. Other than the two-generation reproductive study cited above, which USEPA recently received, relevant new literature has not been found that would alter the assessment for chlorite from the 1994 proposal. USEPA is conducting an external peer review of the CMA two- generation reproductive study. These peer review comments will be included in the Docket for this NODA when they become available. USEPA will evaluate the data from the CMA study, including the peer review, and will provide an opportunity to comment on the potential implications for the regulatory provisions for chlorite prior to the final Stage 1 DBP rule. The CMA study is included in the Docket for this action (CMA, 1997). 2. Chlorine Dioxide The proposed Stage 1 DBPR included a MRDLG of 0.3 mg/L and a MRDL of 0.8 mg/L for chlorine dioxide. The proposed MRDLG for chlorine dioxide was based on developmental neurotoxicity as the critical effect (Orme et al., 1985). The Negotiating Committee agreed to the MRDL of 0.8 mg/L for [[Page 59396]] chlorine dioxide with certain qualifications and reservations. As cited above, the Committee agreed that a two-generation reproductive study on chlorite would be completed for consideration in the final Stage 1 DBPR. Toxicity information on chlorite is considered relevant for characterizing the toxicity of chlorine dioxide. If the chlorite study indicated no concern from reproductive effects at 0.8 mg/L, then the proposed MRDL for chlorine dioxide would remain the same as proposed. If these new data indicate reproductive or developmental effects, then the MRDL will need to be re-examined comparing the tradeoffs and regulatory impacts of a lower chlorine dioxide MRDL and the positive aspects of using chlorine dioxide as a disinfectant. Other than the two-generation reproductive study conducted by CMA for chlorite, there is no new literature that would alter the assessment for chlorine dioxide from the 1994 proposal. As stated above, USEPA believes that the results from the chlorite study are applicable for addressing the toxicity data gaps for chlorine dioxide. USEPA will evaluate the data from the CMA study, including the peer review, and will provide an opportunity to comment on the potential implications for the regulatory provisions for chlorine dioxide prior to the final Stage 1 DBP rule. 3. Trihalomethanes The proposed rule includes an MCL for total trihalomethanes (TTHM) of 0.080 mg/L. MCLGs of zero for chloroform, bromodichloromethane (BDCM), and bromoform were based on sufficient evidence of carcinogenicity in animals. The MCLG of 0.060 mg/L for dibromochloromethane (DBCM) was based on observed liver toxicity from a subchronic study and possible carcinogenicity. Since the 1994 proposal, several new studies have been published on the metabolism for BDCM and chloroform (Testai et al., 1995; Gemma et al., 1996a, 1996b; Gao et al., 1996; Nakajima et al., 1995). In addition, several new studies were found concerning the genotoxicity of chloroform, BDCM, and bromoform (Roldan-Arjona and Pueyo, 1993; LeCurieux et al., 1995; Pegram et al., 1997; Larson et al., 1994c; Fujie et al., 1993; Shelby and Witt, 1995; Hayashi et al., 1992; Sofuni et al., 1996; Matsuoka et al., 1996; Miyagawa et al., 1995; Banerji and Fernandes, 1996; and Potter et al., 1996). There are considerable new data on cytotoxicity and regenerative cell proliferation in the liver and kidney of rats and mice under various conditions (Larson et al., 1993, 1994a, 1994b, 1994c, 1995a, 1995b, 1996; Templin et al., 1996a, 1996b). Many other studies also examined the mechanism of chloroform carcinogenicity, including studying the effects on methylation and expression of growth control genes (Fox et al., 1990, Vorce and Goodman, 1991, Dees and Travis, 1994, Testai et al., 1995, Sprankle et al., 1996, Chiu et al., 1996, Gemma et al., 1996a, 1996b). Short-term toxicity studies (Thorton-Manning et al., 1994; Lilly et al., 1994 and 1996) and chronic toxicity studies which included reproductive evaluations (Klinefelter et al., 1995) were found for BDCM. The new studies on THMs contribute to the weight-of-evidence conclusions reached in the 1994 proposal. Based on the available new studies noted above, the proposed MCLGs for BDCM, DBCM, and bromoform are not anticipated to change. The International Life Science Institute (ILSI) convened an expert panel in 1996 to explore the application of the USEPA's 1996 Proposed Guidelines for Carcinogen Risk Assessment (USEPA, 1996a) to the available data on the potential carcinogenicity of chloroform and dichloroacetic acid (DCA); these data include chronic bioassay data and information on mutagenicity, metabolism, toxicokinetics and mode of carcinogenic action. USEPA will be evaluating the data from the ILSI expert panel for chloroform and will provide an opportunity to comment on the potential implications for the regulatory provisions for chloroform and the trihalomethanes prior to the final Stage 1 DBP rule. 4. Haloacetic Acids The proposed rule included an MCL of 0.060 mg/L for the haloacetic acids (five HAAs-monobromoacetic acid, dibromoacetic acid, monochloroacetic acid, dichloroacetic acid, and trichloroacetic acid) with an MCLG of zero for dichloroacetic acid (DCA) based on sufficient evidence of carcinogenicity in animals, and a MCLG of 0.3 mg/L for trichloroacetic acid (TCA) based on developmental toxicity and possible carcinogenicity. There has been cancer research completed for other HAAs since the 1994 proposal. The 1994 proposal did not include an MCLG for monochloroacetic acid (MCA) because there were inadequate occurrence data for MCA. Since the proposal, a few toxicological studies on MCA have been identified. A recent 2-year carcinogenicity study on MCA and trichloroacetic acid (TCA) (DeAngelo et al., 1997) demonstrated that MCA and TCA were not carcinogenic in male rats. This confirms the results of the NTP (1990) cancer rodent bioassays of MCA. There have been several recent studies examining the mode of carcinogenic action for both DCA and TCA (Pereira and Phelps 1996; and Pereira 1996) including mutagenicity studies (Austin et al., 1996; Mackay et al., 1995; Fox et al., 1996; Fuscoe et al., 1996; Tao et al., 1996; and Parrish et al., 1996). As discussed above USEPA will evaluate the significance of the ILSI panel's report on the risk assessment for DCA and provide an opportunity to comment on the potential implications for the regulatory provisions for DCA and the other haloacetic acids prior to the final Stage 1 DBP rule. Screening studies have shown the potential of different haloacetic acids, including DCA and brominated haloacetic acids, to produce reproductive and developmental effects (Linder et al., 1997c; Hunter et al., 1996; Richard and Hunter, 1996; Linder et al. 1994, 1995, 1997a, 1997b). At this time, these new studies are not expected to alter the MCLGs for DCA or TCA in the proposed rule. USEPA continues to believe that there are inadequate occurrence data to establish MCLGs for MCA, monobromoacetic acid and dibromoacetic acid. 5. Chloral Hydrate The proposed rule included an MCLG of 0.04 mg/L for chloral hydrate. USEPA did not set an MCL for chloral hydrate because it believed the MCLs for TTHM and HAA5, and the treatment technique requirements would provide adequate control for chloral hydrate. In the 1994 proposal, chloral hydrate was considered a group C, possible human carcinogen. Since the 1994 proposal, several new studies have been published which contribute to the weight of evidence conclusion for the potential carcinogenicity of chloral hydrate. These include in vitro cell transformation and genotoxicity studies (Gibson et al., 1995; Adler, 1996; Allen et al., 1994; Parry et al., 1996; and Ni et al., 1996). Some screening studies were found concerning the potential of chloral hydrate to cause reproductive and developmental toxicity (Klinefelter et al., 1995 and Saillenfait et al., 1995). The available new studies mentioned above do not indicate a change in the MCLG for chloral hydrate. 6. Bromate The proposed rule included an MCL of 0.010 mg/L and an MCLG of zero for bromate. A major issue in the proposal was that setting an MCL at 0.010 mg/L [[Page 59397]] would exceed the theoretical 1 x 10-4 lifetime excess cancer risk level for bromate of 5 ug/L. Since the proposal, several toxicology studies have been completed on bromate, including assays for reproductive and developmental effects (Wolfe and Kaiser, 1996). USEPA has recently completed a chronic cancer study in male rats and male mice for bromate. USEPA is evaluating this data and will provide an opportunity for public comment on the potential implications for the regulatory provisions for bromate prior to the final rule. D. Summary of Key Observations Since the proposal, several epidemiology and toxicology studies have been completed on the potential health effects associated with exposure to DBPs. USEPA currently believes the new published data will not impact the MCLGs for BDCM, CDBM, bromoform, chloral hydrate, or trichloroacetic acid. However, USEPA is currently evaluating the results from new toxicology studies for chlorite and bromate and will evaluate the report from the ILSI expert panel on chloroform and DCA when it becomes available. USEPA will provide an opportunity to comment on the potential implications for the regulatory provisions for these DBPs prior to the final rule. E. Request for Public Comments USEPA requests comment on all the new information outlined above and its potential impacts on the regulatory provisions for the final Stage 1 DBPR and any additional data on the health effects from DBPs that need to be considered for the final Stage 1 DBPR. III. Enhanced Coagulation and Enhanced Softening A. 1994 Enhanced Coagulation and Enhanced Softening Proposal As discussed above, the 1994 proposed rule for D/DBPs included enhanced coagulation/enhanced softening requirements in addition to maximum contaminant levels (MCLs) for total trihalomethanes (TTHMs) and the sum of five haloacetic acids (HAA5) (USEPA, 1994b). In that proposal, Subpart H systems (utilities treating either surface water or groundwater under the direct influence of surface water) that use conventional treatment (i.e., coagulation, sedimentation, and filtration) or precipitative softening would be required to remove DBP precursors by enhanced coagulation or enhanced softening. The removal of total organic carbon (TOC) would be used as a performance indicator for DBP precursor control. The 1994 proposed rule (in ``Step 1'' of the treatment technique) provided for 20-50 percent TOC removal, depending on influent water quality (Table III-1). Table III-1.--1994 Proposed Required Removal of TOC by Enhanced Coagulation/Enhanced Softening for Surface-Water Systems a Using Conventional Treatment b ------------------------------------------------------------------------ Source-water alkalinity, mg/L as CaCO3 Source-water TOC, mg/L -------------------------------------- 0-60 >60-120 >120 c (percent) (percent) (percent) ------------------------------------------------------------------------ >2.0-4.0......................... 40.0 30.0 20.0 >4.0-8.0......................... 45.0 35.0 25.0 >8.0............................. 50.0 40.0 30.0 ------------------------------------------------------------------------ a Also applies to utilities that treat groundwater under the influence of surface water. b Systems meeting at least one of the conditions in Section 141.135(a)(1)(i)-(iv) of the proposed rule are not required to operate with enhanced coagulation. c Systems practicing precipitative softening must meet the TOC removal requirements in this column. The 1994 Stage I Federal Register notice proposed that systems achieve a percent TOC removal based on their influent TOC concentration and alkalinity. The proposed rule provided for a number of exceptions to the enhanced coagulation and enhanced softening requirements, namely: (a) When the system's treated water TOC concentration, prior to the point of continuous disinfection, is 2.0 mg/L (b) when the PWS's source water TOC level, prior to any treatment, is 60 mg/L; and these systems are achieving TTHMs 3), except those that use ion exchange, are not subject to performance criteria for the removal of TOC. As part of the enhanced coagulation requirements, the proposed rule indicated that if a PWS could not meet the prescribed TOC removal criteria, it must perform a series of jar or pilot-scale tests (``Step 2'') to determine how much TOC removal they can reasonably and practically achieve. This Step 2 requirement was created to handle the 10 percent of the waters that were not expected to meet the Step 1 criteria, and considerations as to what was practical to achieve involved a consensus-based balancing of policy and scientific perspectives. The proposed jar-testing protocol involves adding regular-grade alum in 10 mg/L increments (or an equivalent amount of iron coagulant) until specific depressed pH goals are achieved (this was referred to as ``maximum pH'' in the proposal), which depends on influent alkalinity and what is practical to achieve. For the alkalinity ranges 0-60, >60- 120, >120-240, and >240 mg/L as calcium carbonate (CaCO3), the maximum pH values are 5.5, 6.3, 7.0, and 7.5, respectively. The maximum pH is a target pH goal for step 2 testing. The maximum pH is the pH value the tested water must be at or below before incremental coagulant addition is discontinued. The protocol was based on alum, as more data were available on the use of this coagulant in a wide variety of waters. However, the proposed rule allows for the use of iron coagulants in the step 2 jar testing. The TOC of each jar-treated water is measured, and then the residual TOC is plotted versus alum dosage. The ``point of diminishing returns'' (PODR) is determined to be when 10 mg/L of additional alum (or an equivalent amount of iron coagulant) does not decrease residual TOC by 0.3 mg/L (i.e., slope of TOC versus alum dosage curve [0.3 mg/L TOC]/[10 mg/L alum]). These data would be used by a utility [[Page 59398]] to request alternative TOC removal performance criteria from the primacy agency. However, one of the intents in setting the step 1 TOC removal percentages at the values chosen was to provide that 90 percent of the systems would not need to do step 2 testing. This would minimize transactional costs for the primacy agencies. If the TOC removal curve never met the slope criterion at any coagulant dose, such a water would be considered unamenable to enhanced coagulation and no TOC removal would be required for such a water. Waters with low TOC and moderate-to-high alkalinity were expected to be some of the more difficult to treat with enhanced coagulation, so systems treating such waters were encouraged to explore alternative technologies (e.g., ozone/chloramines) that could reduce DBP levels significantly below the proposed Stage 1 MCLs (i.e., 3? (2) Use of ferrous salts: Can ferrous salts be used at softening pH levels to further enhance TOC removals? (3) Step 2: Whether data are available on the use of ferrous salts in the softening process which can help define a step 2 for softening? What is the definition of Step 2? B. New Information on Enhanced Coagulation and Enhanced Softening since 1994 Proposal Since the 1994 proposal, there has been considerable research on a number of enhanced coagulation and enhanced softening issues highlighted above in a wide variety of waters nationwide. A summary of the results of some of the studies and surveys are included below. Studies of enhanced coagulation are covered first, followed by discussion of enhanced softening studies. Note that a number of the softening studies looked at TOC removal in essentially the same framework as is used for enhanced coagulation, with emphasis on the coagulant and lime dose and geared toward finding a similar format for step 2 enhanced softening as was defined for enhanced coagulation. A number of these studies focused on the benefits of increased lime or coagulant doses in removing TOC in softening systems. Results of these studies generally showed that percent TOC removal is dependent on the raw water. 1. New Data on Enhanced Coagulation a. UNC Enhanced Coagulation Study. To address many of the aforementioned issues, the University of North Carolina (UNC) at Chapel Hill, with funding from the Water Industry Technical Action Fund (WITAF), performed an enhanced coagulation study (Singer et al., 1995). The UNC research team evaluated a wide range of waters nationwide, which included at least three waters in each box of the 3 x 3 matrix in Table III-1. Each water was jartested in order to determine the feasibility of achieving the proposed step 1 TOC percent removal requirement for each water, as well as to assess the PODR criteria. In addition, recognizing that coagulation primarily removes the humic fraction of the natural organic matter (NOM) in water (Owen et al., 1993), a determination of the percent humic content was made for each of the waters studied in order to better characterize the treatability of each water. NOM fractionation was performed on samples of each raw water and on select coagulated waters using an XAD-8 resin adsorption procedure (Thurman & Malcolm, 1981). In this procedure, the hydrophobic fraction of the water, which includes humic substances, was determined. Furthermore, Edzwald and Van Benschoten (1990) have found the specific ultraviolet absorbance (SUVA) of a water to be a good indicator of the humic content of that water, so SUVA was also determined in the UNC study. SUVA is defined as the UV (measured in m-1) divided by the dissolved organic carbon (DOC) concentration (measured as mg/L). Typically, SUVA values 40 mg/L). BILLING CODE 6560-50-P [[Page 59399]] [GRAPHIC] [TIFF OMITTED] TP03NO97.000 [[Page 59400]] [GRAPHIC] [TIFF OMITTED] TP03NO97.001 BILLING CODE 6560-50-C [[Page 59401]] In the jar tests of the Raleigh water, an alum dose of 35 mg/L resulted in the removal of 47 percent of the TOC, where the proposed step 1 TOC removal for this water was predicted to be 45 percent. The PODR, based on the slope criterion of 0.3 mg/L TOC/10 mg/L of alum, was realized at a jar-test alum dose of 39 mg/L, in which 51 percent of the TOC was removed. In order to comply with a 45-percent TOC removal requirement with a 15-percent safety factor (Krasner et al, 1996), a system would need to design for a 52- percent TOC removal. The results using the Raleigh water appear to address several of the outstanding issues: namely, that the step 1 TOC removal requirements for this water is appropriate, the slope criterion did identify the PODR, and evaluation of the PODR required an examination of points beyond the threshold coagulant dose. Figure III-3 shows jar test results for a low-TOC (2.9 mg/L), high-alkalinity (239 mg/L) water from Indianapolis, IN, from the UNC study (White et al., 1997). The TOC removal curve never exceeded the 0.3/10 slope criterion, which means that this water would be exempt from the enhanced coagulation requirements in the 1994 proposed rule. The step 1 TOC removal requirement of 20 percent can be achieved, with an alum dose of 65 mg/L required in the jar tests. However, the slope of the TOC removal curve shows that this water is not very amenable to enhanced coagulation. BILLING CODE 6560-50-P [[Page 59402]] [GRAPHIC] [TIFF OMITTED] TP03NO97.002 BILLING CODE 6560-50-C [[Page 59403]] A summary of the controlling criterion for each of the 31 waters tested by UNC, based on the 1994 proposed rule criteria, is shown in Table III-2 (adapted from White et al., 1997). Only 14 of the 31 waters met the proposed step 1 percent TOC removal requirements or achieved a settled water TOC concentration 3 Source-water TOC, mg/L ------------------------------------------------------------------------- 0-60 >60-120 >120 ---------------------------------------------------------------------------------------------------------------- >2.0-4.0.............................. a PODR b N/A c PODR PODR PODR PODR STEP 1 d N/A PODR PODR PODR >4.0-8.0.............................. STEP 1 PODR STEP 1 STEP 1 PODR STEP 1 STEP 1 STEP 1 PODR STEP 1 >8.0.................................. STEP 1 STEP 1 STEP 1 STEP 1 PODR PODR PDOR STEP 1 PODR ---------------------------------------------------------------------------------------------------------------- a Settled water TOC less than 2.0 mg/L. b Point of diminishing returns. c Not amenable to enhanced coagulation. d Step 1 required percent removal of TOC. White and co-workers (1997) examined the relationship between the percent humic (hydrophobic) content of the raw waters in the UNC study and the maximum percent removal of DOC achieved at the high alum doses where little additional TOC removal was observed. Figure III-4 shows that waters with relatively high levels of humic material tended to exhibit higher degrees of DOC removal than those with low humic content. Figure III-5 shows that waters that contained high initial nonhumic (hydrophilic) DOC concentrations tended to have high residual DOC concentrations following coagulation. BILLING CODE 6560-50-P [[Page 59404]] [GRAPHIC] [TIFF OMITTED] TP03NO97.003 [[Page 59405]] [GRAPHIC] [TIFF OMITTED] TP03NO97.004 BILLING CODE 6560-50-C [[Page 59406]] In the UNC study, the humic carbon content of the raw waters was reasonably correlated (r\2\=0.74) with their SUVA values (White et al., 1997). Figure III-6 shows that waters with high initial SUVA values (i.e., 3.4-5.7 L/mg-m) exhibited significant reductions in SUVA as a result of coagulation, reflecting substantial removal of the humic (and other UV-absorbing) components of the overall organic matter, whereas waters with low initial SUVA values (i.e., 1.5-2.0 L/mg-m) exhibited relatively low reductions in SUVA. For all of the waters examined, the residual SUVA (i.e., 2.4 L/mg-m) tended to plateau at high alum doses, reflecting that the residual DOC was primarily nonhumic organic matter. BILLING CODE 6560-50-P [[Page 59407]] [GRAPHIC] [TIFF OMITTED] TP03NO97.005 BILLING CODE 6560-50-C [[Page 59408]] In the UNC study, for the 14 waters in which the step 1 TOC removal requirements were met before the PODR was reached, the average raw- water SUVA was 3.9 L/mg-m, whereas the average raw-water SUVA of the other 17 waters was 2.6 L/mg-m (White et al., 1997). For most of the 31 waters examined, the PODR was found to occur at alum doses where SUVA had already reached its plateau. These findings suggested that raw- water SUVA values might be utilized in redefining the step 1 TOC removal requirements and that residual SUVA values might be utilized in defining the PODR. Unlike NOM characterizations with XAD resins in a research laboratory, SUVA is an easy parameter that can be determined by laboratories that measure DOC concentrations and UV absorbance. b. Metropolitan Water District of Southern California/Colorado University Enhanced Coagulation Study. As noted in the UNC study, waters with low TOC and high alkalinity were expected to be the more difficult to treat with enhanced coagulation. Metropolitan Water District of Southern California (MWDSC) and Colorado University at Boulder did detailed studies on two low-TOC waters, one with moderate alkalinity (California State Project Water) and the other with high alkalinity (Colorado River water). In addition to using an XAD-8 resin fractionation to quantify the humic (hydrophobic) versus nonhumic (hydrophilic) content of the NOM, a 1000-dalton (1K) ultrafilter was used to determine what fraction of the bulk or coagulated water was of a lower versus higher molecular weight (Amy et al., 1987). California State Project Water (with 80 mg/L alkalinity) was jar- treated with incremental alum doses of 622 mg/L (up to a total of 111 mg/L). Figures III-7 and III-8 show that addition of alum at 47 mg/L reduced the raw-water bulk DOC concentration from 4.3 mg/L to 2.6 mg/L (a 39-percent bulk DOC removal); subsequent alum addition resulted in a plateauing of the DOC removal rate (Krasner et al., 1995). Throughout the entire range of alum doses evaluated, little of the low-MW and nonhumic DOC was removed. The high-MW and humic fractions, however, were well removed with increasing alum dosages, demonstrating preferential removal of these fractions. The residual DOC remaining after enhanced coagulation was primarily made up of low-MW and nonhumic material. The latter NOM fractions represent the part of the bulk DOC that is not readily amenable to removal by coagulation. BILLING CODE 6560-50-P [[Page 59409]] [GRAPHIC] [TIFF OMITTED] TP03NO97.006 [[Page 59410]] [GRAPHIC] [TIFF OMITTED] TP03NO97.007 BILLING CODE 6560-50-C [[Page 59411]] For this sample of California State Project Water, 52 percent of the DOC was humic NOM and the SUVA value was 2.5 L/mg-m (Krasner et al., 1995). Figure III-9 shows that increasing doses of alum reduced the fraction of humic DOC in the residual DOC to 26 percent. In addition, the reduction in SUVA closely paralleled the reduction in the humic content of the residual DOC. SUVA was reduced to 1.7 L/mg-m with 47 mg/L of alum, whereas the addition of 111 mg/L of alum only reduced the value of SUVA to 1.5 L/mg-m. BILLING CODE 6560-50-P [[Page 59412]] [GRAPHIC] [TIFF OMITTED] TP03NO97.008 BILLING CODE 6560-50-C [[Page 59413]] Colorado River water has a greater amount of low-molecular weight DOC and somewhat more nonhumic DOC than California State Project Water (Krasner et al., 1995). Nonetheless, increased doses of alum did remove DOC in Colorado River water, although not to the same extent as in California State Project Water. Although the alkalinity of Colorado River water (135 mg/L) is higher than that of California State Project Water, the difference in treatability was more likely related to the differences in the NOM characteristics of the two waters. As with California State Project Water, the residual DOC in the coagulated Colorado River water was primarily low-molecular weight and nonhumic NOM (Figures III-10 and III-11). The raw-water Colorado River water had a SUVA value of 1.1 L/mg-m and 44 percent of the DOC was humic NOM. After the addition of 114 mg/L of alum, the humic content of the residual DOC was only reduced to 38 percent and the SUVA value was only reduced to 1.0 L/mg-m (Figure III-12). BILLING CODE 6560-50-P [[Page 59414]] [GRAPHIC] [TIFF OMITTED] TP03NO97.009 [[Page 59415]] [GRAPHIC] [TIFF OMITTED] TP03NO97.010 [[Page 59416]] [GRAPHIC] [TIFF OMITTED] TP03NO97.011 BILLING CODE 6560-50-C [[Page 59417]] Cheng and co-workers (1995) studied enhanced coagulation of California State Project Water and Colorado River water, as well as the effects of seasonal changes on TOC removal. Several water blends were tested, including 100-percent California State Project Water and Colorado River water, as well as 90-, 80-, 70-, 60-, and 50-percent Colorado River water blends. These blends represent the range of waters that are treated at MWDSC's plants and may be subject to enhanced coagulation treatment. The SUVA values for California State Project Water during this study ranged from 2.8 to 3.8 L/m-mg, whereas the SUVA values for Colorado River water varied from 1.0 to 1.7 L/m-mg (the blends of California State Project Water and Colorado River water contained SUVA values of 8 mg/L)/low alkalinity (120 mg/L) waters had low-SUVA (median = 1.7). For the entire 3 x 3 matrix, the cumulative probability distribution (10th, 50th, and 90th percentile) of SUVA values typically increased with either increasing TOC or decreasing alkalinity. Because SUVA is an indication of humic NOM content, and it is the humic fraction that is most amenable to enhanced coagulation, this SUVA distribution supports the earlier observation of the UNC research team that step 1 TOC removals were most readily met in high-TOC waters with low alkalinity. BILLING CODE 6560-50-P [[Page 59418]] [GRAPHIC] [TIFF OMITTED] TP03NO97.012 BILLING CODE 6560-50-C [[Page 59419]] From this database, the Colorado University research team (Edwards, 1997; Tseng & Edwards, 1997) developed a model for predicting organic carbon removal during enhanced coagulation, using as input the coagulant dose, coagulation pH, raw-water UV absorbance, and raw-water DOC concentration. The model assumes that all DOC can be divided into two distinct fractions (Figure III-13): DOC that strongly complexes hydroxide surfaces formed during coagulation and DOC that does not (Edwards et al., 1996). Edwards defined these fractions as sorbing and nonsorbing DOC, respectively. In the model, the relative fraction of sorbing and nonsorbing NOM is calculated using an empirical relation based on the value of SUVA (Edwards, 1997). BILLING CODE 6560-50-P [GRAPHIC] [TIFF OMITTED] TP03NO97.013 BILLING CODE 6560-50-C In the Colorado University modeling effort (Edwards, 1997), the best predictive capability was provided by a site-specific approach using a best-fit sorption constant and nonsorbing DOC fraction for each water quality and coagulant type (Figure III-14). Assuming a typical DOC analytical error of either 0.25 mg/L or 5 percent, 81 percent of the model predictions were accurately predicted within analytical precision. BILLING CODE 6560-50-P [[Page 59420]] [GRAPHIC] [TIFF OMITTED] TP03NO97.014 BILLING CODE 6560-50-C The Colorado University DOC/SUVA model was subsequently used to determine the ``maximum'' TOC removal that can be achieved with enhanced coagulation. All nine boxes in the 3 x 3 matrix (Table III-3) were evaluated using the 10th, 50th, and 90th percentile water qualities. The model was used to determine the amount of sorbable TOC and to examine removal of 100, 90, 80, 70, 60, and 50 percent of the sorbable TOC. Table III-4 summarizes the results from the maximum TOC removal task. A 10th percentile SUVA value corresponds to a water that is difficult to treat (relative to other waters in that same box), whereas a 50th and 90th percentile SUVA value corresponds to waters that are average and easy to treat, respectively, in that box. The sorbable amount of TOC represents the maximum amount of TOC that can be removed using coagulants with no limit on coagulant dosage. Therefore, these values may not be practical or realistic to achieve. In Table III-4, the 1994 proposed Step 1 TOC removal requirements are listed, along with a 15 percent safety factor. For example, in the low-TOC, low alkalinity box, the current Step 1 TOC removal requirement (40 percent) with a safety factor is 46 percent. In this box, for an easy to treat water (90th percentile SUVA of 3.97), 62 percent of the sorbable TOC would need to be removed to ensure compliance with the proposed requirement; whereas for a difficult to treat water (10th percentile SUVA of 2.84), 71 percent of the sorbable TOC would need to be removed. BILLING CODE 6560-50-P [[Page 59421]] [GRAPHIC] [TIFF OMITTED] TP03NO97.015 BILLING CODE 6560-50-C The next analyses evaluated what TOC removal is ``practical'' to achieve in order to better define the 3 x 3 matrix. The data analyses were aimed at developing an alternative set of percent TOC removal numbers for step 1 requirements, recognizing that the goal was to select values that could be ``reasonably'' met by 90 percent of the systems implementing enhanced coagulation. Using the database compiled through the Malcolm Pirnie, Inc./AWWA project and summarized in Table III-3, the following nine equations were developed to predict ``90th- percentile'' TOC for a given coagulant dose. Figure III-15 illustrates the shape of the curves for the low-alkalinity waters. BILLING CODE 6560-50-P [[Page 59422]] [GRAPHIC] [TIFF OMITTED] TP03NO97.016 BILLING CODE 6560-50-C [[Page 59423]] The significance of the 90th-percentile data point is that 90 percent of systems (represented by the database) will have a lower residual TOC compared to what is predicted by the equations for a given coagulant dose. 1. TOC=1.42+2.04 e -7.15 Dose (moles/L) [for low-TOC, low-alkalinity box] 2. TOC=1.37+2.10 e -3.92 Dose (moles/L) [for low-TOC, medium-alkalinity box] 3. TOC=2.10+1.27 e -2.73 Dose (moles/L) [for low-TOC, high-alkalinity box] 4. TOC=1.60+5.38 e -6.29 Dose (moles/L) [for medium-TOC, low-alkalinity box] 5. TOC=2.11+4.41 e -3.47 Dose (moles/L) [for medium-TOC, medium-alkalinity box] 6. TOC=2.64+3.30 e -4.83 Dose (moles/L) [for medium-TOC, high-alkalinity box] 7. TOC=3.22+23.1 e -2.99 Dose (moles/L) [for high-TOC, low-alkalinity box] 8. TOC=4.88+13.8 e -3.33 Dose (moles/L) [for high-TOC, medium-alkalinity box] 9. TOC=6.61+6.44 e -3.57 Dose (moles/L) [for high-TOC, high-alkalinity box] Based upon the above equations, the coagulant dosages for achieving the proposed percent TOC removals and the proposed PODR slope criterion (i.e., 0.3 mg/L TOC per 10 mg/L of alum) were calculated. These calculations indicated that the low-TOC boxes will be at the proposed slope criterion at coagulant dosages lower than what would be required for achieving the proposed step 1 percent TOC removals. The opposite was true for the high-TOC boxes. For the medium-TOC boxes, the calculated coagulant dosages were approximately equal for both criteria. The trends for the different boxes in the matrix are similar to that observed by the UNC research team (Table III-2). Table III-5 summarizes the controlling criteria. Table III-5.--Controlling Criterion for Enhanced Coagulation for Waters Evaluated in Malcolm Pirnie, Inc. Study, Based on Modeling Approach ------------------------------------------------------------------------ Alkalinity mg/L TOC (mg/L) ----------------------------------------- 0-60 >260-120 >120 ------------------------------------------------------------------------ >2.0-4.0...................... PODR........ PODR......... PODR >4.0-8.0...................... Step 1...... PODR......... Step 1 >8.0.......................... Step 1...... Step 1....... Step 1 ------------------------------------------------------------------------ Malcolm Pirnie, Inc. next examined SUVA removal curves (Figure III- 16), similar to what was examined by the UNC research team (Figure III- 6). BILLING CODE 6560-50-P [[Page 59424]] [GRAPHIC] [TIFF OMITTED] TP03NO97.017 BILLING CODE 6560-50-C [[Page 59425]] The 90th-percentile SUVA curves were observed to reach asymptotic values with increasing coagulant Dose (Figure III-16 illustrates the shape of the curves for the low-TOC waters). The following seven equations were developed to predict the 90th-percentile SUVA for a given coagulant Dose. The three alkalinity ranges for the high-TOC waters were collapsed into one group due to lack of sufficient data. Similar to the TOC equations, the significance of the 90th-percentile data point is that 90 percent of systems (represented by the database) will have a lower residual SUVA compared to what is predicted by the equations for a given coagulant Dose. a. SUVA=1.8+2.1 e -11.1 Dose (moles/L) [for low-TOC, low-alkalinity box] b. SUVA=1.8+1. 2 e -7.9 Dose (moles/L) [for low-TOC, medium-alkalinity box] c. SUVA=1.4+2.2 e -9.5 Dose (moles/L) [for low-TOC, high-alkalinity box] d. SUVA=1.9+2.8 e -17.5 Dose (moles/L) [for medium-TOC, low-alkalinity box] e. SUVA=1.8+2.0 e -5.2 Dose (moles/L) [for medium-TOC, medium-alkalinity box] f. SUVA=2.1+0.95 e -6.0 Dose (moles/L) [for medium-TOC, high-alkalinity box] g. SUVA=2.5+2.8 e -3.8 Dose (moles/L) [for high-TOC boxes] From a theoretical viewpoint, the asymptote of the above equations represents the minimum SUVA that could be achieved for a given data set (box) of the 3x3 matrix. The dosages for the minimum SUVA are related to certain maximum percent TOC removals. However, from a practical standpoint, achieving the minimum SUVA could be extremely difficult. An alternative approach could be to attempt to reach SUVA values which are 20 or 25 percent above minimum SUVA indicated by the above equations. Equations 1 through 9 and equations a. through g. were combined to determine the practical percent TOC removal values that could be achieved. The results for ``minimum SUVA+25%'' are shown in Table III- 6. Table III-6.--TOC Removals (%) at ``Minimum SUVA+25%,'' Based on Malcolm Pirnie, Inc. Modeling Effort ------------------------------------------------------------------------ Alkalinity (mg/L) TOC (mg/L) --------------------------- 0-60 >60-120 >120 ------------------------------------------------------------------------ >2.0-4.0.................................... 35 25 15 >4.0-8.0.................................... 35 45 20 >8.0........................................ 60 55 35 ------------------------------------------------------------------------ One limitation of a step 2 based on a settled-water SUVA approach would be that the utilities would have to determine these SUVA values in the absence of any oxidant (such as chlorine, permanganate, or ozone). Addition of oxidant changes the characteristics of the NOM in a manner that disproportionately affects the UV absorbance compared to TOC, thus changing the SUVA values without any actual removal of TOC. d. Evaluation of current (baseline) TOC removals at full-scale. Full-scale TOC removal data were obtained from 76 treatment plants (Table III-7). These data were obtained from plants in the American Water Works Service Company (AWWSCo) system, plants studied by Randtke et al. (1994), and plants in North Carolina studied by Singer et al. (1995). Note that these data represent a one-time sampling at each plant and no specific attempt was made to meet the proposed TOC removal percentages. Also, the proposed compliance requirements were based on an annual average. Based on current treatment, 83 percent of the systems treating moderate-TOC, low-alkalinity water removed an amount of TOC greater than the proposed step 1 requirement, whereas only 14 percent of the systems treating water with low TOC and high alkalinity met the proposed step 1 requirement. For the other systems treating low- or moderate-TOC water, 29-38 percent met the proposed step 1 requirements with existing treatment. Although all of the high-TOC systems met the proposed TOC removal requirements with current treatment, the number of systems in this database were insignificant (1-2 per box). Table III-7.--TOC Removal at Full-Scale Treatment Plants ---------------------------------------------------------------------------------------------------------------- TOC >2.0-4.0 mg/L Percent of plants that achieve specified TOC removal ---------------------------------------------------------------------------------------------------------------- No. of Step 1 0-10% 10-20% 20-30% 30-40% >40% Alkalinity (mg/L) Plants TOC% removal removal removal removal removal ---------------------------------------------------------------------------------------------------------------- 0-60................................. 14 40 14 14 14 29 *29 >60-120.............................. 11 30 36 0 27 18 18 >120................................. 7 20 57 29 14 0 0 ---------------------------------------------------------------------------------------------------------------- TOC >4.0-8.0 mg/L (4)Percent of plants that achieve specified TOC removal -------------------------------------------------------------------------- 0-15% removal 15-25% removal 25-35% removal 35-45% removal >45% removal ---------------------------------------------------------------------------------------------------------------- 0-60................................. 18 45 0 0 11 6 83 >60-120.............................. 8 35 12 25 25 38 0 >120................................. 13 25 31 31 23 15 0 ---------------------------------------------------------------------------------------------------------------- TOC >8.0 mg/L (4)Percent of plants that achieve specified TOC removal -------------------------------------------------------------------------- 0-20 20-30 30-40 40-50 >50 ---------------------------------------------------------------------------------------------------------------- 0-60................................. 2 50 0 0 0 0 100 >60-120.............................. 2 40 0 0 0 0 100 >120................................. 1 30 NA NA 100 NA NA ---------------------------------------------------------------------------------------------------------------- *Values in bold represent the percentage of systems that achieved full-scale TOC removal that is greater than the proposed step 1 requirements. [[Page 59426]] e. Evaluation of ``optimized'' TOC removal. An ``optimized'' coagulation database was assembled, utilizing experiments performed by AWWSCo and by Randtke et al. (1994) (Table III-8). This database included experiments in which a combination of coagulant and acid was evaluated. The National Sanitation Foundation (NSF) limit on sulfuric acid addition (to minimize the introduction of trace impurities present in the acid) is 50 mg/L. In examining the database, an attempt was made to limit coagulant doses to 10-20 times the TOC level. Thus, a water with 3 mg/L TOC might use up to 30-60 mg/L of coagulant (with or without acid), but would not use 100 mg/L of coagulant full- scale. However, a water with 10 mg/L TOC could use 100 mg/L or more of coagulant given the aforementioned 10-20 multiplier for coagulant dose and TOC. A dose of this magnitude is discouraged because the NSF limits on aluminum sulfate and ferric chloride are 150 mg/L and 250 mg/L, respectively. Because these experiments were performed without these acid and coagulant dose limits as constraints, some waters were evaluated with more realistic chemical doses in the PODR experiments. A judgment was made in deciding which set of conditions was the most realistic for each water evaluated. With these elements in mind, an assessment was made as to which experiment was the most appropriate (controlling criteria) for each water. In some cases, a source water was tested more than once. If the identical sample of water (same TOC, SUVA, alkalinity) was coagulated with different coagulants, with or without acid, the highest TOC removal for that water was chosen, as many systems enhancing their coagulation process are also evaluating switching the type of coagulant. BILLING CODE 6560-50-P [[Page 59427]] [GRAPHIC] [TIFF OMITTED] TP03NO97.018 BILLING CODE 6560-50-C [[Page 59428]] f. ``Case-by-case'' data analyses. A decision was made by the TWG, based on the Malcolm Pirnie, Inc. modeling effort and examination of the case-by-case data, to segment out raw waters with SUVA (SUVAr) 120 mg/L) waters in the low (>2-4 mg/L) and moderate (>4-8 mg/L) TOC boxes have SUVA 2.0 L/mg-m, the minimum, 25th percentile, 50th percentile, 75th percentile, and maximum TOC removal for each of the boxes in the 3 x 3 matrix were determined. This analysis allowed for an analysis of the cumulative probability distribution of TOC removal for waters that are amenable to enhanced coagulation. (3) For example, the high-TOC (>8 mg/L)/low alkalinity (0-60 mg/L) box had a range of TOC removals from 56 to 76 percent. In order to comply with a 50 percent TOC removal (the proposed step 1 value for that box) with a safety factor of 15 percent, a 57 percent TOC removal would be required. The minimum and 25th percentile TOC removal for that box is 56 percent. Thus, it is expected that essentially all of the waters in this box (based on this limited data set and data from other sources) could comply with the proposed step 1 requirement. (4) If the step 1 requirement for the high-TOC/low-alkalinity box was raised, for example, to 60 percent, then systems would need a 69 percent TOC removal to safely meet such a requirement. The 75th percentile of TOC removal for this box is 69 percent. Thus, raising the step 1 requirement to 60 percent could potentially drive half or more of the systems in this box to need to do step 2 testing for possible alternative performance criteria. Thus, these data suggest that for this and a number of other boxes (all of the high-TOC boxes and probably most of the moderate-TOC boxes), the currently proposed step 1 TOC removals are appropriate. Systems that can achieve higher TOC removals in these boxes will consider doing so in order to more effectively meet the DBP MCLs that have been proposed. (5) For the low-TOC boxes, even after excluding the low-SUVA waters, the proposed step 1 TOC removal levels still appear too high. In Malcolm Pirnie, Inc.''s modeling of TOC removal at minimum SUVA + 25 percent, it was predicted that the required TOC removals in the low-TOC boxes would be 35, 25, and 15 percent for low-, moderate-, and high- alkalinity, respectively. These predicted TOC removal values are in the range for which the majority of low-TOC waters with SUVA values >2.0 L/ mg-m can achieve. Thus, the TWG recommended to the FACA Negotiating Committee-based on Malcolm Pirnie, Inc.''s modeling effort and this case-by-case analysis--a revised set of TOC removal numbers for the low-TOC boxes, keeping in mind that low-SUVA waters would be excluded from the requirement. (6) The TWG also recommended to the FACA Negotiating Committee an alternative step 2 point of diminishing return (PODR) of settled-water SUVA 2.0 L/mg-m. This action will also reduce transactional costs, as presentation of a settled-water SUVA value will be easier than presenting jar-test data. Nonetheless, the jar-test protocol and slope criterion will still be needed for evaluating alternative performance criterion for other waters. 2. New Data on Enhanced Softening a. AWWARF studies--data on TOC removal. Several studies examined the relationship between increased coagulant dose and TOC removal (Shorney and Randtke, 1996; Clark et al. 1994). These studies indicate that the benefit from increased coagulant dose in TOC removal was dependent on the raw water. In a study funded by AWWARF, Shorney and Randtke (1994) indicated that utilities treating source water relatively low in TOC (i.e., 2.5 to 4 mg/L) and low in turbidity will have the greatest difficulty in removing TOC (Figure III-17 and III- 18). BILLING CODE 6560-50-P [[Page 59429]] [GRAPHIC] [TIFF OMITTED] TP03NO97.019 [[Page 59430]] [GRAPHIC] [TIFF OMITTED] TP03NO97.020 BILLING CODE 6560-50-C [[Page 59431]] The authors indicate some improved TOC removal from small doses of iron salts (5 mg/L ferric sulfate), but no additional TOC removal during softening occurred with increased coagulant addition (up to 25 mg/L dose) as shown in Figures III-17 and III-18. In limited jar testing and in pilot testing, the City of Austin (a softening plant) has observed no significant difference in TOC removal with increasing doses of ferric sulfate beyond a low dose. Table III-9 shows the impact of increasing ferric sulfate doses on the turbidity and TOC concentration for jar tests in the City of Austin. The results indicate no significant difference in TOC removal with increasing doses of ferric coagulants, but did show that varying the coagulant dose did impact the turbidity removal as measured by NTU. Table III-9.--Impact of Varying Ferric Coagulant Dose on TOC Removal, Austin, Texas, 4/9/93, 110 mg/L Lime Dose, Jar Tests ------------------------------------------------------------------------ Treated water Treated Ferric sulfate addition (mg/L) turbidity, water TOC NTU (mg/L) ------------------------------------------------------------------------ 3................................................ 16 2.45 6................................................ 15 2.30 9................................................ 12 2.46 12............................................... 12 2.23 18............................................... 5.5 2.31 ------------------------------------------------------------------------ Pilot testing confirmed the jar test results by showing that increasing ferric sulfate doses beyond that required for turbidity removal proved to have no advantage in additional TOC removal (see Figure III-19). BILLING CODE 6560-50-P [[Page 59432]] [GRAPHIC] [TIFF OMITTED] TP03NO97.021 BILLING CODE 6560-50-C [[Page 59433]] Full-scale plant data from St. Louis County Water Company and Kansas City, MO Water Services show that water temperature, turbidity, and raw water TOC levels have direct impact upon the efficiency of lime softening with iron salt coagulants to improve TOC removal. Multiple jar tests on various waters done by Singer et al. (1996) focused on the relationship between use of lime and soda ash and TOC removal. Using only lime and soda ash (no coagulants), Singer et al. defined the dosages required to meet TOC removal percentages in the matrix. He also defined the dosages required to remove 10 mg/L of magnesium for nine waters that met the alkalinity levels in the right hand column of the matrix (i.e., >120 mg/L). Results of these jar tests are shown in Table III-10. Impacts of the proposed rule would be significant to softening plants if the TOC removal requirements were required to be met by all plants because the requisite lime and soda ash doses were higher than existing doses in the plants. Singer et al. (1996) found the removal of 10 mg/L of magnesium hardness to have less impact, although using the magnesium criteria would make TOC removal levels variable and less significant than meeting the removal levels in the matrix. BILLING CODE 6560-50-P [[Page 59434]] [GRAPHIC] [TIFF OMITTED] TP03NO97.022 BILLING CODE 6560-50-C [[Page 59435]] b. Shorney and coworkers--data on use of SUVA. As discussed previously, SUVA may be a practical method for determining which PWSs would be required to perform enhanced coagulation and enhanced softening. SUVA has been found to be a good indicator of humic content and it is the humic material that is best removed by coagulation. Shorney et al. (1996) report raw water SUVA values -1) divided by the DOC concentration (mg/L). Typically, SUVA values 2-4............................................ 11 8 >4-8............................................ 20 17 >8.............................................. 4 3 ------------------------------------------------------------------------ The data were analyzed with two goals in mind: to find the appropriate TOC removal levels for the rule matrix for softening plants and to determine what would define an appropriate step 2 for softening systems. To address the first question, the average TOC percent removals for each TOC group were plotted on a percentile basis and are shown in Figure III-21 (Clark et al., 1997) for the 2-4 mg/L TOC, and Figure III-22 for the 4-8 mg/L TOC (Clark et al., 1997). BILLING CODE 6560-50-P [[Page 59438]] [GRAPHIC] [TIFF OMITTED] TP03NO97.024 [[Page 59439]] [GRAPHIC] [TIFF OMITTED] TP03NO97.025 BILLING CODE 6560-50-C [[Page 59440]] To examine the percentage of plants that would meet the proposed requirements, the survey data were analyzed and the results are shown in Table III-12. The results in Table III-12 indicate that the relative impact of meeting the TOC removal requirement in the proposed rule would be greatest in the low TOC group (>2-4 mg/L) . Table III-12.--Percentage of Softening Plants Meeting Current Proposed Requirements ------------------------------------------------------------------------ Proposed 1994 Percentage Raw TOC (mg/L) required of plants percent that met removals requirements ------------------------------------------------------------------------ >2-4........................................... 20 60 >4-8........................................... 25 80 >8............................................. 30 66 ------------------------------------------------------------------------ To address the second question regarding Step 2 criteria, the survey results for percent removal TOC and lime dose were plotted to examine the relationship between them (see Figure III-23) and to determine whether a point of diminishing returns can be identified for lime addition. Figure III-23 indicates that no correlation can be discerned, the data are highly variable, and no point of diminishing returns corresponding to a specific lime dose addition can be identified. The wide variation in water quality (e.g., pH, alkalinity, type of TOC), as well as the differences in coagulant usage, probably contributed to data variability. BILLING CODE 6560-50-P [[Page 59441]] [GRAPHIC] [TIFF OMITTED] TP03NO97.026 BILLING CODE 6560-50-C [[Page 59442]] Another important issue for softening systems is the pH level used in the softening process. As the lime dose is increased, the pH of the softening process increases and the character of the precipitate changes; as the pH rises above 10, the major precipitate formed changes from calcium carbonate to magnesium hydroxide. The TOC percent removal in the survey data was plotted versus the pH of softening and is shown in Figure III-24 . The data show that at higher softening pH levels, generally greater percentages of TOC are removed. Also as the lime dose is increased alkalinity is consumed and if the lime dose is high enough to deplete the raw water alkalinity, soda ash must be added to maintain the precipitation process. Crossing either one of these thresholds (either changing the dominant precipitate from calcium carbonate to magnesium hydroxide or changing from a lime softening system to a lime/ soda softening system) constitutes a major change in the treatment process. Magnesium hydroxide floc do not act the same as calcium carbonate floc either in settling or in sludge treatment and the plant design for the two precipitates would be significantly different. Forcing a plant to increase pH to the point of having to add soda ash would also be a significant treatment change due to pH adjustment problems and because the precipitate would likely be changing at the same time. Most softening plants are normally operated without soda ash addition because of the high cost of soda ash, the additional sludge production, the increased chemical addition to stabilize the water and the increased sodium levels in the finished water (Randtke et al., 1994 and Shorney et al., 1996). BILLING CODE 6560-50-P [[Page 59443]] [GRAPHIC] [TIFF OMITTED] TP03NO97.027 BILLING CODE 6560-50-C [[Page 59444]] Raising the pH by adding lime can have other impacts such as depleting alkalinity and potentially causing corrosion problems. To determine what finished water alkalinity most softening plants produce, the survey data was plotted for finished water alkalinity and TOC percent removal (see Figure III-25 (Clark et al., 1997)). With only a few outliers and regardless of the percent TOC removal, most plants produce finished water with alkalinity between 30 and 60 mg/L as CaCO3. BILLING CODE 6560-50-P [[Page 59445]] [GRAPHIC] [TIFF OMITTED] TP03NO97.028 BILLING CODE 6560-50-C [[Page 59446]] The survey obtained basic information on disinfection practices in softening plants. Forty percent of the plants responding predisinfect. Softening plants predisinfect for the same reasons that conventional coagulation plants do, that is, to comply with Surface Water Treatment Rule Disinfection requirements, to oxidize iron and manganese, to control zebra mussels and Asiatic clams, and to control taste and odor problems. Disinfectants in use in softening plants are as follows: 28% of plants use free chlorine for both primary and secondary disinfection. 50% of plants use free chlorine/chloramine. 10% of plants use chloramine. 7% of plants use chlorine dioxide/chloramine. 5% of plants use ozone/chloramine. In spite of the fact that some 78% of softening plants are using free chlorine for at least a portion of their disinfection, the reported yearly average THMs indicate that 90 percent of plants are currently meeting an 80 g/L level for THMs (see Figure III-26 (Clark et al., 1997)). All reporting softening plants have average HAA5 levels below 60 g/L (see Figure III-27 (Clark et al., 1997)). For the majority of softening plants, minor adjustments to disinfection practices may bring them into compliance with the proposed total THM and HAA5 MCLs, as long as predisinfection credit is allowed. Without predisinfection credit, these plants could face the major impact of having to provide disinfection time after sedimentation, and for at least one of the reporting utilities, that could mean significantly increasing the free chlorine contact time to get the maximum CT credit by making up for a shortened detention time. The end result for that system will likely be an increase in finished water total THMs over what are being produced using predisinfection credit. However, these site-specific issues will need to be addressed individually, as removing the precursors by enhanced softening will also remove some of the chlorine demand resulting in less disinfectant addition to obtain the necessary residual. BILLING CODE 650-50-P [[Page 59447]] [GRAPHIC] [TIFF OMITTED] TP03NO97.029 [[Page 59448]] [GRAPHIC] [TIFF OMITTED] TP03NO97.030 BILLING CODE 6560-50-C [[Page 59449]] C. Summary of Key Enhanced Coagulation and Enhanced Softening Observations Based on the data and analysis outlined above, the M/DBP Advisory Committee has recommended the following revisions to the proposed enhanced coagulation and softening requirements to address the outstanding issues on the use of this technology to control DBP precursors (see Table III-13). The top row has been modified from the proposal by lowering the values by 5%. Enhanced softening systems are required to comply with the column for alkalinity > 120 mg/L as CaCO3. Table III-13.--1997 Proposed Required Removal of TOC by Enhanced Coagulation/Enhanced Softening for Surface- Water Systems Using Conventional Treatment ---------------------------------------------------------------------------------------------------------------- Source water alkalinity, mg/L as CaCO3 ----------------------------------------------- Source water TOC, mg/L 0-60a >60-120 a >120 a b (percent) (percent) (percent) ---------------------------------------------------------------------------------------------------------------- >2.0-4.0........................................................ 35.0 25.0 15.0 >4.0-8.0........................................................ 45.0 35.0 25.0 >8.0............................................................ 50.0 40.0 30.0 ---------------------------------------------------------------------------------------------------------------- a Not applicable to waters with raw-water SUVA 2.0 L/mg-m. b Systems practicing precipitative softening must meet the TOC removal requirements in this column. For waters with TOC >4.0 mg/L (6 of the 9 boxes in the 3 x 3 matrix), the TWG felt that 90 percent of these waters can meet the 1994 proposed step 1 TOC removal requirements. For waters with TOC >2.0-4.0 mg/L, the Committee recommended that the TOC removal requirements be 35, 25, and 15 percent for low-, moderate-, and high-alkalinity waters, respectively. For low-TOC waters with raw-water SUVA >2 L/mg-m, the TWG felt that 90 percent of the systems treating such waters will be able to comply with the revised step 1 TOC removal levels. The Committee recommended that waters with raw-water SUVA 2.0 L/mg-m be given an exemption to enhanced coagulation and enhanced softening. SUVA is an indicator of the humic content of a water. Coagulation removes humic matter, so waters with low-SUVA values contain primarily nonhumic matter, which is not amenable to enhanced coagulation. The use of a raw water SUVA 2.0 L/mg-m. At this point, the residual TOC is mainly composed of nonhumic matter that is not amenable to enhanced coagulation; therefore, it is not productive to add additional coagulant. Because oxidants can destroy UV, but not TOC, SUVA must be determined on water that has not been exposed to oxidants. Thus, using a settled-water SUVA 2.0 L/mg-m as a PODR should be done on jar-tested water (as the slope criterion is done) unless the full-scale plant is not using preoxidation/predisinfection. The TWG believes that these revised requirements will result in a limited amount of transactional costs for the PWSs and their primacy agencies. The Committee recommended this option to EPA. Enhanced softening systems that cannot meet the removal percentages specified in the TOC removal matrix must demonstrate that they have met alternative performance criteria, e.g., depressed the alkalinity to a minimum level or lowered settled water SUVA 2.0 L/mg-m. Also, systems that remove a minimum of 10 mg/L of magnesium hardness (as CaCO3) from their raw water are exempt for enhanced softening requirements. Lime softening plants would not be required to perform lime-soda ash softening, and no softening plant will be required to lower treated effluent alkalinity below 40 mg/L (as CaCO3), as part of any Step 2 procedure. Because the determination of SUVA requires measurement of DOC, the TWG believed that guidance on this determination is necessary. DOC is determined on filtered samples, but it is important that the filter paper does not leach DOC. Protocols and quality assurance measures to ensure that SUVA is properly measured are discussed in the analytical methods section. Another exception to enhanced coagulation in the proposed 1994 rule was for systems that treated water with 60 mg/L alkalinity that achieved TTHMs 2/chloramine addition in order to lead to reduction of DBPs. Four investigators tested the validity of this assumption. Summers (Summers et al., 1997) summarized the findings of the four investigators concerning the impact of moving the point of chlorination during coagulation, flocculation and sedimentation on DBP formation for a representative range of waters and treatment conditions. In addition, studies were carried out at the University of Cincinnati under the sponsorship of EPA, the American Water Works Association (Water Utility Council-Water Industry Technical Action Fund) and the Chlorine Chemistry Council (Solarik et al., 1997). The results of these studies are summarized here. Sixteen source waters have been evaluated to date. The waters were selected to proportionately represent the national source water distribution in the enhanced coagulation 3 x 3 (TOC--alkalinity) matrix as estimated from AWWA water industry database (WIDB). Waters were chosen to represent the >2.0-4.0 mg/L and >4.0-8.0 mg/L TOC ranges. For TOC >8.0 mg/L, prechlorination would generally not be a suitable option, as experience and computer modeling have shown that prechlorination of these waters under the conditions of this study is likely to yield TTHM and HAA5 values that exceed the 0.080 mg/L and 0.060 mg/L proposed MCLs, respectively. WIDB TOC data indicate that less than 10 percent of the surface waters have TOC concentrations greater than 8.0 mg/L. The study was conducted using a bench-scale batch jar testing procedure with chlorine added at different times to simulate full-scale continuous flow conditions with chlorine added at different points. Alum (Al2(SO4)318H2O) was used as the coagulant for all waters and two alum doses were examined for 14 of the 16 waters evaluated. The baseline dose was set at the level required for turbidity control, while a second increased dose was set at the level necessary to meet the required percent TOC removal in the 3 X 3 enhanced coagulation matrix. In three cases, the required TOC removal was achieved by baseline coagulation. The jar tests were carried out at ambient laboratory temperature, (22 deg.C). Chlorine was added to four parallel jars at four different times during the coagulation, flocculation and sedimentation process for both the baseline coagulant dose and the increased coagulant dose: 1) 3 minutes before rapid mixing (Pre-RM), (2) at the end of rapid mixing (Post-RM), (3) in the middle of flocculation (Mid-Floc), and (4) at the end of sedimentation (Post-Sed). Additionally, the raw uncoagulated water was adjusted to the settled water pH and chlorinated. The DBP results from the raw uncoagulated water served as a basis for comparison. The chlorine doses were chosen to yield a free chlorine residual of 0.6 0.4 mg/L after 3 hours of total contact time at ambient pH (6.1-8.1) and laboratory temperature (22 deg.C). The 3 hour reaction time is representative of that of a typical coagulation, flocculation and sedimentation process train. At the end of the 3 hour incubation time, the reaction was quenched and DBPs were assessed. Settled water was also chlorinated under uniform formation conditions (UFC) (Summers et al., 1996) to represent distribution system DBP formation. A more detailed experimental approach is presented elsewhere (Solarik et al., 1997, Summers et al., 1997). Impact of Point of Chlorination The impact of moving the point of chlorination downstream for both baseline and increased dose coagulation is shown in Figures IV.1, IV.2, and IV.3 for TOX, TTHM, and HAA5 concentrations, respectively. The d [Text truncated at 120,000 characters. The full text is on the page linked above.] --- Source: Frix Law Library, https://www.frixlaw.com/law-library/documents/fr%3A97-28746. Public record. Not legal advice.