June 27, 2008
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Floodwaters and surface water runoff commonly contain high levels of bacteria. Whenever floodwaters or surface runoff inundates a well, bacterial contamination is likely. Any private well inundated with flood waters or runoff should be tested for bacterial contamination. If bacteria is suspected, or if laboratory tests confirm the presence of bacteria in a private water supply, users should use an alternative water supply or disinfect water for drinking and food preparation until further testing for bacteria is negative.
Disinfecting Your Water Supply
For short-term disinfection of water for drinking and food preparation, it is highly recommended to boil the water. Heat kills microorganisms and is the oldest effective means of disinfecting drinking water. Water should be brought to a vigorous rolling boil for one minute, which includes an adequate safety factor. Any longer will concentrate other chemical contaminants that may be present, such as nitrate. Generally, untreated water can be used for showering and bathing as long as the water is not swallowed.
Shock Chlorination
The entire distribution system can be disinfected using shock chlorination. Shock chlorination involves placing a strong chlorine solution in the well and the complete distribution system. After shock chlorination, another water sample should be submitted for testing. The water should test negative before use. More than one shock chlorination treatment may be needed to effectively treat the entire water supply.
Sharon Skipton
Extension Water Quality Educator
