Coliform Testing

Coliform testing measures the concentration of total coliform bacteria. Coliform bacteria are found in the intestines of warm blooded animals and therefore are present in sewage, on and in soils, surface waters and vegetation. They are tested for as indicators of sewage contamination. They can be tested for in water samples, swab samples, and air samples. Water samples for coliform testing must be treated with sodium thiosulfate if the water comes from a chlorinated system. Swab samples must use liquid culture swabs to preserve the sampled bacteria. Testing can be done for presence/absence of coliform in the samples or for enumeration. For sampling information, please contact us so that we can discuss the needs of your unique situation.

The purpose of coliform testing

Coliform bacteria may or may not be harmful themselves, but their presence is a strong indication potential presence of other harmful bacteria. The total coliform test is therefore routinely used for monitoring drinking water. Their presence in your drinking water suggests that there has been a breach, failure, or other change in the integrity of the water system and that disease causing bacteria may have entered into your drinking water.

Limitation of coliform testing

Unfortunately, coliform testing does not indicate their source. The presence of coliform bacteria in drinking water indicates a possible contamination by sewage or animal wastes. Sewage and animal wastes contain many disease causing organisms in addition to coliforms.

Detection of fecal coliforms (a subset of total coliforms) or Escherichia coli (E. coli—a subset of fecal coliforms) can indicate that your system is contaminated with fecal waste. Fecal coliforms and E. coli are good indicators of fecal contamination and of the potential presence of waterborne pathogens associated with fecal contamination.