Interim Enhanced Surface Water Treatment Rule

• Read the Federal Register Notice About the Rule (HTML) ~ (PDF)

Disinfection of drinking water is one of the major public health advances in the 20th century. One hundred years ago, typhoid and cholera epidemics were common through American cities and disinfection was a major factor in reducing these epidemics. However, the disinfectants themselves can react with naturally-occurring materials in the water to form unintended byproducts which may pose health risks.

In the past ten years, however, we have learned that there are specific microbial pathogens, such as Cryptosporidium, that are resistant to traditional disinfection practices. In 1993, Cryptosporidium caused 400,000 people in Milwaukee to experience intestinal illness. More than 4,000 were hospitalized, and at least 50 deaths have been attributed to the disease. There have also been cryptosporidiosis outbreaks in Nevada, Oregon, and Georgia over the past several years.

Amendments to SDWA in 1996 require EPA to develop rules to balance the risks. It is important to strengthen protection against microbial contaminants, especially Cryptosporidium, and at the same time, reduce potential health risks from disinfection byproducts. The new Interim Enhanced Surface Water Treatment Rule and Stage 1 Disinfectants and Disinfection Byproducts Rule are the first of a set of rules under the Amendments. This fact sheet focuses on the Interim Enhanced Surface Water Treatment Rule. A separate fact sheet focuses on the Stage 1 Disinfectants and Disinfection Byproducts Rule (EPA 815-F-98-010).

EPA's Science Advisory Board concluded in 1990 that exposure to microbial contaminants such as bacteria, viruses, and protozoa (e.g., Giardia lamblia and Cryptosporidium) was likely the greatest remaining health risk management challenge for drinking water suppliers. Acute health effects from exposure to microbial pathogens are documented and associated illness can range from mild to moderate cases lasting only a few days to more severe infections that can last several weeks and may result in death for those with weakened immune systems.

The Interim Enhanced Surface Water Treatment Rule applies to public water systems that use surface water or ground water under the direct influence of surface water (GWUDI) and serve at least 10,000 people. In addition, States are required to conduct sanitary surveys for all surface water and GWUDI systems, including those that serve fewer than 10,000 people.

The Interim Enhanced Surface Water Treatment Rule amends the existing Surface Water Treatment Rule to strengthen microbial protection, including provisions specifically to address Cryptosporidium, and to address risk trade-offs with disinfection byproducts. The final rule includes treatment requirements for waterborne pathogens, e.g., Cryptosporidium. In addition, systems must continue to meet existing requirements for Giardia lamblia and viruses. Specifically, the rule includes:

• Maximum contaminant level goal (MCLG) of zero for Cryptosporidium

• 2-log Cryptosporidium removal requirements for systems that filter

• Strengthened combined filter effluent turbidity performance standards

• Individual filter turbidity monitoring provisions

• Disinfection profiling and benchmarking provisions

• Systems using ground water under the direct influence of surface water now subject to the new rules dealing with Crypdosporidium

• Inclusion of Cryptosporidium in the watershed control requirements for unfiltered public water systems

• Requirements for covers on new finished water reservoirs

• Sanitary surveys, conducted by States, for all surface water systems regardless of size

The rule, with tightened turbidity performance criteria and individual filter monitoring requirements, is designed to optimize treatment reliability and to enhance physical removal efficiencies to minimize the Cryptosporidium levels in finished water. Turbidity requirements for combined filter effluent will remain at least every four hours, but continuous monitoring will be required for individual filters. In addition, the rule includes disinfection profiling and benchmarking provisions to assure continued levels of microbial protection while facilities take the necessary steps to comply with new DBP standards.

States must adopt and implement the requirements of this regulation by January 1, 2002. Simultaneous compliance with the Stage 1 Disinfection Byproduct Rule, promulgated at the same time, will be achieved as follows:

Public water systems that use surface water or ground water under the direct influence of surface water, either in whole or in part, and serve a population of 10,000 or more generally have three years from Federal promulgation to comply with requirements of this rule, except for disinfection profiling and benchmarking, which require systems to begin sampling after three months. In cases where capital improvements are needed to comply with the rule, States may grant systems up to an additional two years to comply.

EPA estimates that implementation of the Interim Enhanced Surface Water Treatment Rule will:

• Improve public health by increasing the level of protection from exposure to Cryptosporidium and other pathogens (i.e., Giardia, or other waterborne bacterial or viral pathogens) in drinking water supplies through improvements in filtration at water systems;

• Significantly reduce the level of Cryptosporidium in finished drinking water supplies through improvements in filtration at water systems (i.e., revised turbidity requirements);

• Decrease the likelihood of endemic (constant low-level presence of a disease or infection) illness from Cryptosporidium by 110,000 to 463,000 cases annually and related health costs, as well as incidences of illness from Giardia and other waterborne pathogens; and

• Reduce the likelihood of the occurrence of outbreaks of cryptosporidiosis (illness from Cryptosporidium) and their associated economic costs by providing a larger margin of safety against such outbreaks for some systems.

The total annualized national cost for implementing the Interim Enhanced Surface Water Treatment Rule is $307 million. EPA believes that the benefits exceed the costs. The rule will result in increased costs to public water systems for improved turbidity treatment, monitoring, disinfection benchmarking and covering new finished water reservoirs, as well as State implementation costs.

EPA estimates that 92 percent of households will incur an increase in their water bill of less than $1 per month; 7 percent of households will incur an increase in their water bills of between $1 - $5 per month; and less than 1 percent will incur an increase of between $5 to $8 per month.

A series of guidance manuals supports the Interim Enhanced Surface Water Treatment Rule and the Stage 1 Disinfectants/Disinfection Byproducts Rule. The manuals aid EPA, State agencies and affected public water systems in implementing the two interrelated rules, and will help to ensure that implementation among these groups is consistent. These manuals are available on the Internet at http://www.epa.gov/safewater/mdbp/implement.html and may be ordered from the Safe Drinking Water Hotline, 1 (800) 426-4791.

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