Water: Microbial & Disinfection Byproducts Rules
Microbials and Disinfection Byproducts (MDBP)
This site provides information about microbial pathogens and disinfection byproducts as related to drinking water.
In many cases, source water from a lake, river, reservoir or ground water aquifer needs to be disinfected to inactivate (or kill) microbial pathogens. Microbial pathogens include a few types of bacteria, viruses, protozoa, and other organisms. Some pathogens are often found in water, frequently as a result of:
- Fecal matter from sewage discharges
- Leaking septic tanks
- Runoff from animal feedlots into bodies of water
To protect drinking water from these pathogens, water suppliers often add a disinfectant to drinking water such as chlorine. However, disinfectant practices can be problematic because:
- Certain microbial pathogens, such as Cryptosporidium, are highly resistant to traditional disinfection practices.
- Disinfectants themselves can react with naturally-occurring materials in the water to form byproducts, such as trihalomethanes and haloacetic acids, which may pose health risks.
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 microbial pathogens while simultaneously minimizing health risks to the population from disinfection byproducts. There are several existing and future rules that are designed to achieve these goals.
This web site is designed to provide you with information about microbial pathogens, disinfection byproducts, existing and future rules, as well as guidance materials and background information.
This site provides information about past and upcoming training for the implementation of the Stage 2 and LT2 rules. On this site you will find information about webcasts, train the trainer sessions, and other training opportunities designed to help you with the implementation of the Stage 2 and LT2 rules.
This site contains tools developed to assist public water systems, laboratories, EPA, and states in implementing the Long Term 2 Enhanced Surface Water Treatment Rule and the Stage 2 Disinfectants and Disinfection Byproducts Rule.
This site will also provide you with access to the following tools:
- Ground Water Rule (GWR) (October 11, 2006)
Ground Water Rule specifies the appropriate use of disinfection while addressing other components of ground water systems to ensure public health protection.
- Long Term 2 Enhanced Surface Water Treatment Rule (LT2 rule) (December 15, 2005)
LT2 rule is to reduce illness linked with the contaminant Cryptosporidium and other disease-causing microorganisms in drinking water.
- Stage 2 Disinfectants and Disinfection Byproducts Rule (Stage 2 DBP) (December 15, 2005)
Stage 2 DBP rule builds upon earlier rules that addressed disinfection byproducts to improve your drinking water quality and provide additional public health protection from disinfection byproducts.
- Long Term 1 Enhanced Surface Water Treatment Rule (LT1) (January 14, 2002)
The Long Term 1 Enhanced Surface Water Treatment Rule strengthens control of microbial contaminants, particularly Cryptosporidium, for small systems—those systems serving fewer than 10,000 people. It is the smaller system counterpart of the Interim Enhanced Surface Water Treatment Rule.
- Filter Backwash Recycling Rule (FBR) (June 8, 2001)
The Filter Backwash Recycling Rule requires public water systems (PWSs) to review their backwash water recycling practices to ensure that they do not compromise microbial control.
- Stage 1 Disinfectants and Disinfection Byproducts Rule (Stage 1 DBP) (December 16, 1998)
The Stage 1 Disinfectants and Disinfection Byproducts Rule reduces exposure to disinfection byproducts for customers of 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.
- Interim Enhanced Surface Water Treatment Rule (IESWT) (December 16, 1998)
The Interim Enhanced Surface Water Treatment Rule improves control of microbial contaminants, particularly Cryptosporidium, in systems using surface water, or ground water under the direct influence of surface water, that serve 10,000 or more persons. The rule builds upon the treatment technique requirements of the Surface Water Treatment Rule.
- Surface Water Treatment Rule (SWT) (June 28, 1989)
The Surface Water Treatment Rule seeks to prevent waterborne diseases caused by viruses, Legionella, and Giardia lamblia. These disease-causing microbes are present at varying concentrations in most surface waters. The rule requires that water systems filter and disinfect water from surface water sources to reduce the occurrence of unsafe levels of these microbes.
- Total Coliform Rule (June 29, 1989)
The Total Coliform Rule set both health goals and legal limits for total coliform levels in drinking water. The rule also details the type and frequency of testing that water systems must do.
- Ground Water Rule (GWR) (October 11, 2006)