Coliform bacteria occur naturally in the environment and are not generally harmful themselves. However, their presence suggests other disease causing organisms may exist in your drinking water supply.

Coliform bacteria are found in the intestinal tracts of warm-blooded animals such as humans, dogs, and deer. They have been selected as an indicator for the bacterial quality of drinking water. The presence of these bacteria in drinking water may signify the well (source) is defective, or that there may be problems with the water treatment, or the water distribution system.

It is common to have contamination when maintenance has been performed on the water supply system. Faulty in-ground sewage disposal systems may also be the source of contamination.

Coliforms from animal waste can enter directly into water supplies but can also move down through the soil and contaminate ground water. This process is accelerated during spring flooding or heavy rainfall.

Symptoms: The symptoms of disease-causing organisms may include diarrhea, nausea, vomiting, cramps or other gastrointestinal distress.

Risks: Most coliform bacteria are used as an indicator that suggests the water is not safe for human consumption. The presence is of concern in that disease-causing organisms, such as E.coli or parasites may be present. In severe cases, the symptoms listed above can be fatal. Most susceptible are infants, elderly and others with compromised immune systems.

Action: Consult with your physician immediately if you suddenly have diarrhea with blood, regardless of the suspected cause.

Water containing coliform bacteria should not be used for human consumption. As a precautionary measure, the water should be boiled, at a rolling boil for at least one minute prior to consumption. Bacteria and other harmful disease-causing microorganisms can be removed from water by disinfections (chlorine treatment, ozone treatment, ultraviolet light treatment, and distillation) and /or filtration.

For detailed procedure of well disinfections, please refer to the web page on well disinfection.

There is detailed information about environmental health and water testing in the Public Health section of this website.

You can also check Health Canada's website (see link below) for detailed information on water quality and health.

Contact your local public health inspector (see link below) for specific advice about your water supply.