USEPA has announced that it is proposing to revise its Total Coliform rule. That rule, first effective December 31, 1990, establishes limits for total coliform levels in treated drinking water provided by affected public water supplies.
"The coliforms are a broad class of bacteria which live in the digestive tracts of humans and many animals. The presence of coliform bacteria in tap water suggests that the treatment system is not working properly or that there is a problem in the distribution system that moves treated water from the treatment plant to customer homes." (www.epa.gov/safewater/disinfection/tcr/basicinformation.html)
The presence of total coliforms in drinking water generally is controlled by disinfection applications, of which chlorination is the oldest methodology and probably still the most commonly used, although other approaches also are being used.
The Total Coliform rule establishes a maximum contaminant level (MCL) or limit for total coliforms, which is an enforceable, absolute standard. It also establishes a Maximum Contaminant Level Goal (MCLG) of zero, which is an non-enforceable health based goal. Compliance with the MCL is determined by required sampling of treated water.
The presence of coliforms in water does not necessarily constitute pathogens, but instead can serve as a signal that there may be a problem with the integrity of the system or its operation that could permit pathogens or other bacteria to enter the system.
The proposed revisions to the rule will require water utilities to find and fix the problem that permits microbacterial presence when sampling results are positive. They also provide incentives for better system operation and update public notice requirements. To learn more about the proposed revisions see www.epa.gov/safewater/disinfection/tcr/index.html
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