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Coliform Bacteria

Coliform bacteria are organisms which live in the intestines of humans and animals. They also can be found in plants, soils and surface water. Presence of these bacteria indicate that other harmful organisms may be present in the water. Since testing for a specific disease-causing organism is difficult, the coliform bacteria test is considered the best way to determine whether or not a water supply is safe from bacterial contamination.

Drinking Water Standard and Health Risks

Water containing any coliform bacteria per 100 milliliters of water, TNTC (too numerous to count) or CG (confluent growth) should not be used for drinking or cooking unless boiled for 5 minutes or disinfected by other means. Bacteria and other organisms found in drinking water can cause intestinal upset as well as diseases such as dysentery, typhoid and hepatitis.

Possible Source of Contamination

Most bacteria in wells or springs come from surface water contaminated by decayed animal waste or human activities. As surface water seeps downward through the soil towards the water table, these bacteria may be naturally removed by the soils. The extent of removal depends on the depth and character of the soil. In general, shallow wells and springs are more likely to be contaminated than deep wells. Wells and springs must be properly located, constructed and maintained in order to prevent surface water from entering the well or spring.

Presence of coliform bacteria in wells or springs usually result from:

1. Well or spring covers that allow dust, rain, bird droppings, etc. to enter.

2. Wells or springs that are located in areas where surface water covers the well or spring during the wet periods of the year.

3. Defective steel well-casing seals.

4. Shallow wells or springs with rocked up side walls.

5. Recent changes or repairs to the well or spring, pumps, piping, etc.

6. Improper well location and/or construction.

If you have one or more of the problems described above, it should be corrected. If it is not corrected, the problem may reoccur, even after repeated disinfection.

The water system may be disinfected by mixing chlorine bleach (Clorox, Dazzle, etc.) with the water in the well or spring in the following dosages:

DUG WELL

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*Approximate amount of water in the bottom of a well and not the total depth of the well. For a surface SPRING, use 2 gallons.

DRILLED WELL

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*PLEASE NOTE: A greater amount of chlorine may be needed to disinfect the water depending on the degree of contamination.

Once the chlorine has been mixed with the water, open all faucets, sillcocks and similar outlets individually until you smell chlorine in each outlet. Allow the mixture to stand in the system overnight, then flush the chlorine mixture from the system using an outside faucet and garden hose. DO NOT FLUSH THE MIXTURE INTO YOUR SEPTIC SYSTEM!! You may resume using the toilet facilities as the septic system is designed to handle this, but the septic system cannot handle the large amount of water needed to flush the chlorine from the well. Since the chlorine will kill the grass, be careful where you run the water outside.

After disinfection, the water supply should be resampled. Resample kits for "bacteria only" are available. (SEE ENCLOSURE)

Resampling should be done only after the odor of chlorine disappears. It takes about 3 or 4 days of normal water usage before all of the chlorine smell disappears.

 

IF YOU HAVE QUESTIONS OR NEED ADVICE ON HOW TO CORRECT THE PROBLEM, CONTACT THE HEALTH AND ENVIRONMENTAL TESTING LABORATORY AT 207-287-1716.

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