Keeping Pace with Science and Engineering Case Studies in Environmental Regulation (1993) / Chapter Skim
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Trihalomethanes and Other By-Products Formed by Chlorination of Drinking Water
Trihalomethanes and Other By-Products Formed by Chlorination of Drinking Water
Pages 141-164
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From page 141... ...
Environmental Protection Agency (EPA) is considering adopting more stringent regulations for THMs; it may also establish maximum contaminant levels or treatment techniques for several other disinfection by-products (DBPs)
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From page 142... ...
occurrence may be greater than initially believed PHILIP C SINGER Policy and Regulation - ~- Congress legislates Safe Drinking Water Act - EPA issues advance notice of proposed rulemaking for organic chemicals in water - ~- EPA proposes maximum contaminant level for total THMs - ~-THMs regulated Utilities serving more than 75,000 people must comply with THM rule - Utilities serving from 10,000 to 75,000 must comply with THM rule - EPA proposes treatment techniques to comply with maximum contaminant level for total THMs _ _ _ 1 985 - · - Congress legislates SDWA amendments - EPA proposes Surface Water Treatment Rule - EPA proposes Total Coliform Rule ,___ ~ - AWWARF survey determines impact of THM ,===- _ ~ regulation onwaterutilities - EPA finalizes Surface Water Treatment Rule ' ,- 19 go - EPA finalizes Total Coliform Rule l ~ - EPA initiates approach to balance microbial risks and risks associated with disinfection by-products _ _ _ _ _ L EPA originally expected to establish maximum contaminant levels for additional disinfection by-products and more stringent maximum contaminant levels for THMs; proposed rule delayed until 1993 EPA considers ~enhanced" Surface Water Treatment Rule - EPA requests negotiated rulemaking (RegNeg)
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From page 143... ...
Figure 2 shows that in the 80-city survey, total trihalomethane concentrations in the finished drinking water correlated with the nonpurgeable organic carbon concentrations in the raw water. From March 1976 to January 1977 the EPA conducted the National Organics Monitoring Survey, which verified the findings of the earlier survey, and demonstrated that THMs continued to form to a significant extent in the finished water distribution system (Brass et al., 1977~.
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From page 144... ...
By separately measuring the total organic halide concentration in chlorinated water using an adsorption/pyrolysis/coulometric detection procedure (Standard Methods, 1985) , researchers have demonstrated that the sum of the measured THMs, haloacetic acids (HAAs)
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From page 145... ...
. 145 The results of this survey indicated that THMs were the by-products present in the highest concentrations in finished drinking water, with the haloacetic acids present at approximately 50 percent of the total THM concentration.
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From page 146... ...
with the consumption of chlorinated drinking water. Although there is no single study that can be cited as a seminal study linking chlorination and cancer, it is the sheer weight of evidence provided by the large number of studies showing a positive relationship, albeit a weak one, that underscores the concern, from a cancer risk perspective, about the safety of drinking chlorinated water (Morris et al., 1992~.
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From page 147... ...
The issues involve the weakness of the reported epidemiological relationships between cancer and consumption of chlorinated drinking water, the high dosages of test compounds administered to laboratory animals to induce tumors, and the validity of the models used to extrapolate from these high dosage effects to the low concentrations at which these compounds are found in drinking water. These are issues common to many
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From page 148... ...
Following passage of the Safe Drinking Water Act by Congress in 1974 and the findings of the National Organics Reconnaissance Survey, the Environmental Protection Agency published its advance notice of proposed rulemaking on July 14, 1976 to address control options for organic chemical contaminants in drinking water (EPA, 1976~. Two approaches were considered: establishing maximum contaminant levels for specific organic chemicals or for surrogates (indicators)
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From page 149... ...
On February 28, 1983, in accordance with the stipulations of the Safe Drinking Water Act, the EPA identified the best technology and treatment techniques that community water systems could use to achieve compliance with the maximum contaminant level for total THMs (EPA, 1983~. These techniques were believed to be "generally available, taking costs into consideration." The specific techniques identified were the use of chloramines or chlorine dioxide as alternative or supplemental disinfectants and oxidants, improved clarification for THM precursor removal, moving the point of chlorination to reduce THM formation, and the use of powdered activated carbon to remove THMs or THM precursors.
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From page 150... ...
to determine the extent to which utilities were in compliance with the maximum contaminant level for total THMs, and the cost of achieving such compliance. The results showed that enactment of the THM regulation resulted in a 40-50 percent average reduction in total THM concentrations for the larger utilities surveyed.
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From page 151... ...
Additional scientific findings involving the formation and behavior of THMs and the other disinfection by-products led to the development of water treatment strategies to limit the formation of halogenated disinfection by-products. The enactment of the THM regulation resulted in treatment modifications that subsequently reduced the extent of THM formation and, most likely, of many of the other disinfection by-products as well, thereby lowering the public health risk associated with THMs and the consumption of chlorinated drinking water.
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From page 152... ...
They revolve primarily around the 1986 amendments to the Safe Drinking Water Act, the promulgation by the EPA in 1989 of the Surface Water Treatment Rule and the Total Coliform Rule, the perceived need to establish maximum contaminant levels for other disinfection by-products in addition to the THMs, and the previously stated need (EPA, 1979) to reevaluate the maximum contaminant level for total THMs based on experiences gained following the initial regulation.
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From page 153... ...
The original EPA schedule consisted of proposed maximum contaminant levels for disinfectants and disinfection by-products by September 1990, adoption of final maximum contaminant levels by September 1991, and compliance with the adopted maximum contaminant levels by March 1993 (McGuire, 1989~. As a result of the Safe Drinking Water Act amendments, it was anticipated that: the previous maximum contaminant level for total THMs would be modified by adopting individual maximum contaminant levels for each of the four THM species based on knowledge of the differing toxicological impacts of each of the species; consideration would be given to making the new maximum contaminant levels for the THMs more stringent than the maximum contaminant level for total THMs previously adopted in 1979; maximum contaminant levels would be established for a number of the additional disinfection by-products identified in finished drinking water for which data on health effects were available; maximum contaminant levels would be established for the disinfectants themselves; and the maximum contaminant levels would apply to all water systems, not just to those serving more than 10,000 people.
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From page 154... ...
Furthermore, even without the Surface Water Treatment Rule and Total Coliform Rule, most of the utilities surveyed by McGuire and Meadow indicated they would have difficulty complying with a maximum contaminant level for total THMs significantly below 50 ,ug/L. Clearly, given the stringent provisions of the two new rules, reduction of the maximum contaminant level to less than 50 ,ug/L would be expected to have an even greater economic impact than that projected by the McGuire and Meadow survey.
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From page 155... ...
at anything more stringent than a 10-4 risk level. While it might be possible to achieve maximum contaminant levels corresponding to these risk levels by reducing the dose of chlorine for drinking water treatment, the Surface
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From page 156... ...
Alternatively, other disinfectants could be used in place of free chlorine to meet the requirements of the Surface Water Treatment Rule, but these alternatives are not without their own health risks. For example, the use of chlorine dioxide results in the presence of chlorite (ClO2-)
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From page 157... ...
Although the infectivity of the cysts was not verified, these findings suggest that the specifications for 3-log and 4-log inactivation or removal of Giardia and viruses, respectively, in the Surface Water Treatment Rule may not be restrictive enough to reduce the risk of exposure to these waterborne diseases to levels that EPA deems acceptable. Accordingly, the EPA is considering adopting an "enhanced" Surface Water Treatment Rule.
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From page 158... ...
EPA is still developing their risk assessment model for disinfection byproducts. Initial predictions indicated that there would be a dramatic increase in the incidence of waterborne disease if more stringent maximum contaminant levels for THMs and other disinfection by-products were established, but there is a vast amount of uncertainty associated with the model, deriving primarily from inadequate scientific (primarily toxicological and microbiological)
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From page 159... ...
Epidemiological studies suggested that people drinking chlorinated water appeared to be subjected to a somewhat increased incidence of cancers of the urinary and digestive tracts. Accordingly, THMs were regulated.
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From page 160... ...
Research on this subject is continuing. Using granular activated carbon adsorption to control disinfection by-products has been demonstrated to be a relatively expensive process for most waters, and adoption of maximum contaminant levels for disinfection byproducts that are based on the use of granular activated carbon as the best available technology is likely to have a major economic impact on society.
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From page 161... ...
Pp. 807-824 in Proceedings of the American Water Works Association Annual Conference.
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From page 162... ...
Pp. 913-943 in Proceedings of the American Water Works Association Annual Conference.
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From page 163... ...
1989. Correlations between trihalomethanes and total organic halides formed during drinking water treatment.
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From page 164... ...
1987b. Drinking water; national primary drinking water regulations; total coliforms.
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