Disinfection By-Products in Drinking Water - ACS Publications

Chapter 2

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The Evolution of Disinfection By-Products Regulations: Past, Present, and Future J. Alan Roberson American Water Works Association, 1300 Eye Street, N.W., Washington, DC 20005

The regulation of disinfection by-products (DBPs) has evolved significantly in the last thirty years since the initial discovery of trihalomethanes (THMs) in drinking water in 1974. DBP regulations are important from a public health perspective due to the potential widespread exposure. These changing regulations have both significantly reduced DBP exposure and challenged water utilities to maintain compliance. Compliance challenges will continue as recently finalized regulations will impact more water utilities and potential treatment technologies for compliance become more complex. Many questions still remain about unknown and unregulated DBPs that might result in future additional DBP regulations.

Introduction The regulation of DBPs continues to be important for water utilities due to the widespread practice of disinfection and the potential for exposure to a large fraction of the population. The majority of water utilities disinfect, primarily for the prevention of waterborne disease outbreaks. Disinfection of water supplies started in the early 1900s and resulted in a significant decrease in the annual death rate from typhoid fever (/). Yet, even in those early times before the actual scientific discovery of DBPs, utilities recognized that chlorine disinfection had to be balanced with potential taste and odor problems from chlorine itself 22

© 2008 American Chemical Society In Disinfection By-Products in Drinking Water; Karanfil, T., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 2008.


23 and certain chlorination reaction products (e.g., chlorophenols). As the science evolved with the initial discovery of DBPs, the risk balancing between the formation of DBPs and adequate disinfection became more significant. Going beyond the valid and significant taste and odor concerns, utilities and their customers continue to be legitimately concerned about potential adverse health effects from DBPs. More health effects research on DBPs is needed, as the body of current health effects data still generates controversy. From the federal perspective, DBPs are regulated on a bladder cancer endpoint assuming a lifetime exposure of 70 years, i.e., a chronic health endpoint. Some limited and mixed health effects data points towards potential adverse reproductive and developmental endpoints. Addressing more acute health endpoints would constitute a major regulatory shift, leading to substantial changes in the complianceframework,which would pose compliance challenges for utilities. The universe of knowledge is still not complete on DBPs, as the initial discovery of trihalomethanes (THMs) in drinking water was only a little over thirty years ago (2, 3). As analytical methods have ipiproved, more and more DBPs are being identified and quantified (4). Many research questions remain on the health effects from these new DBPs, the potential exposure, and how treatment can prevent their formation or remove them.

Historical DBP Regulations The Safe Drinking Water Act (SDWA) was signed into law on December 16, 1974 (PL 93-523). In 1975, using existing Public Health Service guidelines as the foundation, EPA finalized the National Interim Primary Drinking Water Regulations (NIPDWRs) for 22 well-known chemical and microbial contaminants (5). Since DBPs had just been recently discovered, they were not included in this initial rulemaking.

The Total Trihalomethane (TTHM) Rule The Total Trihlalomethane (TTHM) Rule was finalized in 1979 and was the first federal regulation addressing DBPs (6). The TTHM Rule established a Maximum Contaminant Level (MCL) for TTHMs at 0.10 mg/1 with compliance based on a running annual average of quarterly samples taken at locations throughout the distribution system. The TTHM Rule applied only to systems serving > 10,000 people that added a disinfectant, so small systems were not impacted by this first DBP regulation. From the national perspective, the TTHM Rule was significant as it was the first federal regulation that followed a broad range of new SDWA regulatory requirements for USEPA, including toxicological and health risk assessments, occurrence and exposure assessments,

In Disinfection By-Products in Drinking Water; Karanfil, T., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 2008.


24 specified analytical techniques, options for treatment technologies, and a detailed cost-benefit analysis (7). The TTHM Rule was successful in significantly reducing THM exposure and most utilities complied by shifting the point of chlorination to later in the treatment plant, reducing the amount of chlorine added, or switching to chloramination for secondary disinfection in the distribution system (8). Soon thereafter, USEPA finalized the Surface Water Treatment Rule (SWTR) in 1989, mandating filtration and specific inactivation (disinfection) requirements for viruses and Giardia lamblia that varied slightly based on pH and temperature and had to be achieved on essentially a continuous basis (9). The risk balancing between disinfecting for microbial protection and minizing DBP exposure was now instituted in a regulatory framework, and EPA had additional concerns with utilities simply increasing the amount of disinfectant to meet their inactivation requirements.

Evolving from the TTHM Rule To address ongoing concerns with potential adverse health effects from DBPs, USEPA informally released a "straw man" rule in 1989 that broadly framed future DBP regulations. At that time, USEPA was considering a future TTHM MCL of 25 or 50 ug/1, and listed other DBPs that it would consider regulating. This was a substantial reduction in the MCL, and many utilities would have faced major compliance challenges. EPA followed up this "straw man" with a status report in 1991. Due to the significant concerns with the "straw man" rule that were raised by the water utilities and the recognition of the need for appropriate risk balancing, USEPA elected to use a negotiated rulemaking (Reg-Neg) process for future DBP and microbial regulations and to continue to pair these regulations in the future. USEPA constituted a Reg-Neg Committee that included representatives of State and local health and regulatory agencies, utilities, elected officials, and consumer and environmental advocates. The Reg-Neg Committee met from November 1992 through June 1993. The Reg-Neg Committee recommended the development of three categories of proposed regulations: • • •

A two-stage approach for DBPs, i.e., Stage 1 and Stage 2 Disinfection Byproducts Rules (70); An "interim" Enhanced Surface Water Treatment Rule (ESWTR) (77); and An Information Collection Rule (ICR) (72).

The approach used by the Reg-Neg Committee considered the constraints of simultaneously treating the water to control for both DBPs and microbial


25 contaminants. The Reg-Neg Committee further stipulated that the compliance schedules for the paired rules should be linked to assure simultaneous compliance and the appropriate risk-risk balancing.


The Stage 1 Disinfection By-Products Rule (DBPR) USEPA published the final Stage 1 Disinfection By-Products Rule (DBPR) on December 16, 1998, along with the final IESWTR (13,14). The Stage 1 DBPR lowered the TTHM MCL to 0.080 mg/1 and established a new MCL of 0.060 mg/1 for the sum of five of the haloacetic acids (HAA5). The Stage 1 DBPR also established a MCL for bromate at 0.010 mg/1 for plants that use ozone and a MCL for chlorite of 1.0 mg/1 for plants that use chlorine dioxide. The Stage 1 DBPR set new standards for disinfectants, with the Maximum Residual Disinfectant Levels (MRDLs) for chlorine and chloramines of 4.0 mg/1 and a MRDL for chlorine dioxide of 0.8 mg/1. The Stage 1 DBPR applied to all systems that added a disinfectant, with phased compliance deadlines for large and small systems. The compliance impacts of pulling small systems into the DBP regulatoryframeworkwill be discussed later. Systems complied with the Stage 1 DBPR with the typical treatment strategies of shifting the point of chlorination to later in the treatment plant, reducing the amount of chlorine added, switching to ozone or chlorine dioxide for primary disinfection, implementing enhanced coagulation or enhanced softening, and/or switching to chloramination for secondary disinfection in the distribution system. In an attempt to address unknown DBPs, a Treatment Technique (TT) was established using enhanced coagulation or enhanced softening to improve removal of DBP precursors. A 3X3 matrix mandated a percentage removal of Total Organic Carbon (TOC) based on source water alkalinity and source water TOC and alternative compliance criteria were also developed for "difficult-totreat" waters. Many utilities were able to comply with the DBP MCLs by taking advantage of the TOC removal from enhanced coagulation/softening. The intent of the ICR was to collect raw water quality, treatment informaion, and DBP occurrence data for 18 months from the large systems serving > 100,000 to be used in the next round of negotiations for the Stage 2 DBPR. The results of the ICR monitoring data have been summarized elsewhere (15, 16).

The Stage 2 Disinfection By-Products Rule (DBPR) A Federal Advisory Committee (FACA) met from September 1999 to July 2000 to work on the Stage 2 DBPR and Long-Term 2 Enhanced Surface Water



26 Treatment Rule (LT2ESWTR). The Advisory Committee developed an Agreement in Principle that laid out their recommendations on how to further control DBPs (77). This Agreement was the basis for the final Stage 2 DBPR that was published on January 4, 2006 (75). The Stage 2 DBPR maintained the same numeric MCLs from the Stage 1 DBPR but added three significant modifications to compliance monitoring design and compliance determinations. First, as part of the Stage 2 DBPR, systems would be required to conduct an Initial Distribution System Evaluation (IDSE). The IDSE is a monitoring program (or a hydraulic study) to locate potential future compliance monitoring locations that would be more representative of higher DBP concentrations in the distribution system. Second, future compliance at these locations would also be based on the Locational Running Annual Average (LRAA), i.e., based on the running annual average of each sampling location as opposed to averaging across all compliance locations in the distribution system. Finally, the concept of operational evaluation levels was established to curtail peak DBP levels by providing utilities with a structured approach in the regulation to remain in compliance. Compliance with the Stage 2 DBPR was predicted to drive the many of the surface water systems still usingfreechlorine to switch to chloramination for secondary disinfection in the distribution system. To address groundwater systems that could potentially need disinfection (comparable to the SWTR), USEPA published the final Ground Water Rule (GWR) on November 8, 2006 (19). The GWR established a risk-based approach for ground water systems to collect data to determine if their wells were susceptible to fecal contamination, submit that data to the state, and then the state would make the determination if disinfection was required (or not).

DBP Compliance Data USEPA tracks compliance with the federal regulations with the Safe Drinking Water Information System/Federal (SDWIS/FED), and this compliance data is available on the EPA website. The author downloaded the FY 1998-2005 data for DBP MCL, MRDL, and TT (enhanced coagulation or softening) violations. As previously mentioned, the Stage 1 DPBR had phased compliance deadlines for large and small systems. Systems serving > 10,000 people (that were already impacted by the TTHM Rule) had to comply with the Stage 1 DBPR by January 1, 2002. Smaller systems serving

Disinfection By-Products in Drinking Water - ACS Publications

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