Drinking Water Rules Target Disease-Causing Microorganisms, Disinfection Byproducts

On Dec. 15, EPA finalized two related drinking water protection rules -- one to reduce the risk of disease-causing microorganisms from entering water supplies and the other to require water systems to limit the amount of potentially harmful "disinfection byproducts" (DBPs) that end up in drinking water.

"Clean drinking water is a key ingredient to keeping people healthy and our economy strong," said EPA Administrator Stephen L. Johnson. "Over the past seven years EPA has worked collaboratively with stakeholders to develop regulations that will provide a balance between the need to disinfect drinking water and protect citizens from potentially harmful contaminants."

Agency officials said the rules are important public health measures that will decrease the incidence of gastrointestinal illnesses caused by microbial contaminants and reduce potential cancer risks associated with disinfectant byproducts in drinking water. Finalizing the two rules represents the last phase of a congressionally required rulemaking strategy under the 1996 Amendments to the Safe Drinking Water Act.

Long Term 2 Enhanced Surface Water Treatment Rule

The "Long Term 2 Enhanced Surface Water Treatment Rule" (LT2), increases monitoring and treatment requirements for water systems that are prone to outbreaks of Cryptosporidium, a waterborne pathogen. Consuming water with Cryptosporidium causes gastrointestinal illness which can be severe in people with weakened immune systems, such as infants or the elderly and could be fatal in people with severely compromised immune systems, such as cancer and AIDS patients. LT2 will improve public health by reducing illness due to Cryptosporidium and other harmful microorganisms in drinking water.

The rule requires that public water systems that are supplied by surface water sources monitor for Cryptosporidium. Those water systems that measure higher levels of Cryptosporidium or do not filter their water must provide additional protection by using options from a "microbial toolbox" of treatment and management processes, such as ultraviolet disinfection, and watershed control programs.

The rule also addresses risks of contamination in systems that store treated drinking water in open reservoirs, where water quality can be compromised by exposure to outdoor elements. The rule requires open reservoirs to either be covered or receive added treatment.

Monitoring: Under the rule, systems will monitor their water sources to determine treatment requirements. This monitoring includes an initial two years of monthly sampling for Cryptosporidium. To reduce monitoring costs, small filtered water systems will first monitor for E. coli -- bacterium which is less expensive to analyze than Cryptosporidium, according to the agency -- and will monitor for Cryptosporidium only if their E. coli results exceed specified concentration levels.

Monitoring starting dates are staggered by system size, with smaller systems beginning monitoring after larger systems. Systems must conduct a second round of monitoring six years after completing the initial round to determine if source water conditions have changed significantly. Systems may use (grandfather) previously collected data in lieu of conducting new monitoring, and systems are not required to monitor if they provide the maximum level of treatment required under the rule.

Cryptosporidium treatment: Filtered water systems will be classified in one of four treatment categories (bins) based on their monitoring results. The majority of systems will be classified in the lowest treatment bin, which carries no additional treatment requirements. Systems classified in higher treatment bins must provide 90 percent to 99.7 percent (1.0 to 2.5-log) additional treatment for Cryptosporidium. Systems will select from a wide range of treatment and management strategies in the "microbial toolbox" to meet their additional treatment requirements. All unfiltered water systems must provide at least 99 or 99.9 percent (2 or 3-log) inactivation of Cryptosporidium, depending on the results of their monitoring. These Cryptosporidium treatment requirements reflect consensus recommendations of the Stage 2 Microbial and Disinfection Byproducts Federal Advisory Committee.

Other requirements: Systems that store treated water in open reservoirs must either cover the reservoir or treat the reservoir discharge to inactivate 4-log virus, 3-log Giardia lamblia, and 2-log Cryptosporidium. These requirements are necessary to protect against the contamination of water that occurs in open reservoirs, according to the agency. In addition, systems must review their current level of microbial treatment before making a significant change in their disinfection practice. This review will assist systems in maintaining protection against microbial pathogens as they take steps to reduce the formation of disinfection byproducts under the Stage 2 Disinfection Byproducts Rule.

The rule will result in increased costs to public water systems and states. The average annualized present value costs of the rule are estimated to range from $92 million to $133 million (using a three percent discount rate). Public water systems will bear approximately 99 percent of this total cost, with states incurring the remaining 1 percent.

Stage 2 Disinfection Byproducts Rule

The "Stage 2 Disinfection Byproducts Rule" (Stage 2 DBP), was developed to balance the benefits and risks posed by drinking water disinfection. While disinfection is commonly known as one of the major public health advances of the 20th century, it also creates harmful byproducts that are formed when disinfectants, such as chlorine, combine with naturally occurring materials in water.

The final rule targets water systems that have the greatest risk of high DBPs by using more stringent methods for determining compliance, officials said. Under the rule, water systems are required to find monitoring sites where higher levels of DBPs are likely to occur and use these new locations for compliance monitoring. If DBPs are found to exceed drinking water standards at any of these new monitoring locations, water systems must begin to take corrective action.

Entities potentially regulated by the Stage 2 DBPR are community and nontransient noncommunity water systems that produce and/or deliver water that is treated with a primary or residual disinfectant other than ultraviolet light.

A community water system (CWS) is a public water system that serves year-round residents of a community, subdivision, or mobile home park that has at least 15 service connections or an average of at least 25 residents.

A nontransient noncommunity water system (NTNCWS) is a water system that serves at least 25 of the same people more than six months of the year, but not as primary residence, such as schools, businesses, and day care facilities.

The rule applies to approximately 75,000 systems; a small subset of these (about 4 percent) will be required to make treatment changes. The mean cost of the rule is $79 million annually.

The rules were proposed in August 2003, and were developed from consensus recommendations from a federal advisory committee comprised of state and local governments, tribes, environmental, public health and water industry groups, agency officials said.

The final rules will be published in the Federal Register in January. Pre-publication copies and additional information can be found on the EPA Web site at http://www.epa.gov/safewater/disinfection.

This article originally appeared in the 12/01/2005 issue of Environmental Protection.

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