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Testing
To ensure our drinking water is safe, we conduct routine bacteriologic tests. More than 200 samples are taken every month from representative sites in the system and tested for coliform bacteria. The presence of coliform bacteria is considered to be an indicator that the water may have been contaminated. If any sample comes back from the lab positive, that site is immediately resampled to confirm the presence or absence of contamination. The Utility took 2,428 microbial distribution samples in 2006, with no positive result. Potential sources of contamination could, under certain conditions, include microbial organisms from leaking sewer pipes, septic systems, agricultural livestock operations, wildlife and points of use. The Utility's testing program is a systematic method of checking that such events have not occurred.
Disinfection
To prevent microbial contamination in our water system, Madison Water Utility adds chlorine to the water to provide protection against bacterial or viral contamination. The advantage of using chlorine as a disinfectant is that it will produce a free residual that will stay in the system for several days, ready to kill any bacteria and viruses that might get into the system. Our goal is to maintain a free chlorine residual throughout our distribution system.
Health Impacts
For drinking water to be totally safe, it needs to be free of bacteria and viruses.
The presence of bacteria or viruses in a drinking water supply may or may not result in disease symptoms such as diarrhea, intestinal cramps, nausea and jaundice. The EPA has set enforceable safe drinking water standards for fecal coliform bacteria to reduce the risk of these adverse health effects. Under this standard, all drinking water shall be free of such bacteria. If microbiological sampling within our system indicates that there is a potential that the system may have been contaminated, Madison Water Utility will take immediate steps to correct the situation, and the public may be advised to boil their drinking water until follow-up samples demonstrate that the water is free of coliform bacteria.
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