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Ground Water & Drinking Water |  |
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Drinking Water Priority Rulemaking: Microbial and Disinfection Byproduct RulesExisting Rules Future Rules
Guidance & implementation documents for these rules 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 throughout American cities. Disinfection was a major factor in reducing these epidemics, and it is an essential part of drinking water treatment today. However, the disinfectants themselves can react with naturally-occurring materials in the water to form unintended organic and inorganic byproducts which may pose health risks. Over the past ten years, we have also learned that there are specific microbial pathogens, such as Cryptosporidium, that are highly 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. A major challenge for water suppliers is how to balance the risks from
microbial pathogens and disinfection byproducts. It is important to provide
protection from these microbial pathogens while simultaneously ensuring
decreasing health risks to the population from disinfection byproducts
(DBPs). The 1996 Safe Drinking Water Act (SDWA) Amendments require EPA
to develop rules to achieve these goals.
Schedule of M-DBP Rules
Public Health Concerns Most Americans drink tap water that meets all existing health standards all the time. These new rules will further strengthen existing drinking water standards and thus increase protection for many water systems. 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. In addition, while disinfectants are effective in controlling many microorganisms, they react with natural organic and inorganic matter in source water and distribution systems to form potentially harmful DBPs. Many of these DBPs have been shown to cause cancer and reproductive and developmental effects in laboratory animals. More than 200 million people consume water that has been disinfected. Because of the large population exposed, health risks associated with DBPs, even if small, need to be taken seriously.
To support the M-DBP rulemaking process, the Information Collection Rule required large public water systems serving at least 100,000 people to monitor and collect data on microbial contaminants, disinfectants and disinfection byproducts for 18 months. The data provide EPA with information about disinfection byproducts, disease-causing microorganisms, including Cryptosporidium, and engineering data to control these contaminants. Drinking Water Microbial and Disinfection Byproduct Information collected for the ICR is available in EPA's Envirofacts Warehouse. Interim Enhanced Surface Water Treatment Rule & Stage 1 Disinfectants and Disinfection Byproducts Rule EPA finalized the Interim Enhanced Surface Water Treatment Rule and Stage 1 Disinfectants and Disinfection Byproducts Rule in November 1998, as required by the 1996 Amendments to the Safe Drinking Water Act, Section 1412(b)(2)(C). The final rules resulted from formal regulatory negotiations with a wide range of stakeholders that took place in 1992-93 and 1997. On Jan 16, 2001, EPA published final revisions to the IESWTR and Stage 1DBPR (read online) ~ (PDF).
Interim Enhanced Surface Water Treatment Rule The Interim Enhanced Surface Water Treatment Rule applies to systems using surface water, or ground water under the direct influence of surface water, that serve 10,000 or more persons. The rule also includes provisions for states to conduct sanitary surveys for surface water systems regardless of system size. The rule builds upon the treatment technique requirements of the Surface Water Treatment Rule with the following key additions and modifications:
The Interim Enhanced Surface Water Treatment Rule, with tightened turbidity performance criteria and required individual filter monitoring, is designed to optimize treatment reliability and to enhance physical removal efficiencies to minimize the Cryptosporidium levels in finished water. In addition, the rule includes disinfection benchmark provisions to assure continued levels of microbial protection while facilities take the necessary steps to comply with new DBP standards. Stage 1 Disinfectants and Disinfection Byproducts Rule The final Stage 1 Disinfectants and Disinfection Byproducts Rule applies to community water systems and non-transient non-community systems, including those serving fewer than 10,000 people, that add a disinfectant to the drinking water during any part of the treatment process. The final Stage 1 Disinfectants and Disinfection Byproducts Rule includes the following key provisions:
The terms MRDLG and MRDL, which are not included in the SDWA, were created during the negotiations to distinguish disinfectants (because of their beneficial use) from contaminants. The final rule includes monitoring, reporting, and public notification requirements for these compounds. This final rule also describes the best available technology (BAT) upon which the MRDLs and MCLs are based.
Filter Backwash Recycling Rule The Filter Backwash Recycling Rule (FBRR) requires public water systems (PWSs) to review their backwash water recycling practices to ensure that they do not compromise microbial control. Under the FBRR, recycled filter backwash water, sludge thickener supernatant, and liquids from dewatering processes must be returned to a location such that all processes of a system’s conventional or direct filtration including coagulation, flocculation, sedimentation (conventional filtration only) and filtration, are employed. Systems may apply to the State for approval to recycle at an alternate location. The Filter Backwash Rule applies to all public water systems, regardless of size. Long Term 1 Enhanced Surface Water Treatment Rule While the Stage 1 Disinfectants and Disinfection Byproducts Rule rule applies to systems of all sizes, the Interim Enhanced Surface Water Treatment Rule only applies to systems serving 10,000 or more people. The Long Term 1 Enhanced Surface Water Treatment Rule, promulgated in January 2002, will strengthen microbial controls for small systems i.e., those systems serving fewer than 10,000 people. The rule will also prevent significant increase in microbial risk where small systems take steps to implement the Stage 1 Disinfectants and Disinfection Byproducts Rule. EPA believes that the rule will generally track the approaches in the Interim Enhanced Surface Water Treatment Rule for improved turbidity control, including individual filter monitoring and reporting. The rule will also address disinfection profiling and benchmarking. The Agency is considering what modifications of some large system requirements may be appropriate for small systems. Future M-DBP Rules EPA has proposed a Ground Water Rule that specifies the appropriate use of disinfection while addressing other components of ground water systems to ensure public health protection. There are more than 158,000 public ground water systems. Almost 89 million people are served by community ground water systems, and 20 million people are served by non-community ground water systems. Ninety-nine percent (157,000) of ground water systems serve fewer than 10,000 people. However, systems serving more than 10,000 people serve 55% (more than 60 million) of all people who get their drinking water from public ground water systems. The Ground Water Rule will be promulgated summer 2001. The SDWA, as amended in 1996, requires EPA to finalize a Stage 2 Disinfectants and Disinfection Byproducts Rule by May 2002. Although the 1996 Amendments do not require EPA to finalize a Long Term 2 Enhanced Surface Water Treatment Rule along with the Stage 2 Disinfectants and Disinfection Byproducts Rule, EPA believes it is important to finalize these rules together to ensure a proper balance between microbial and DBP risks. EPA begun discussions with stakeholders in December 1998 on the direction for these rules. EPA anticipates proposing these rules in 2001. The intent of the rules is to provide additional public health protection, if needed, from DBPs and microbial pathogens.
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