Coliform bacteria are Aindicator organisms which are used in water microbiological analysis. Coliforms are a group of bacteria which are readily found in soil, decaying vegetation, animal feces, and raw surface water. They are not normally present in deep groundwater and treated surface water. However, individuals with compromised immune systems should be considered at risk. Coliforms, rather than the actual pathogens, are used to assess water quality because their detection is more reliable.
Pathogens appear in smaller numbers than coliforms, so are less likely to be isolated.
Drinking water found to contain coliforms is considered biologically contaminated. In brief, this method combines two separate examinations. First, the 100 milliliter sample is combined with growth medium, and then incubated for 24 hours at 35.0 degrees Centigrade. After 24 hours, only coliform bacteria will use the growth medium for food, resulting in a change in the water sample's appearance. At the same time, a second examination is performed to determine if the coliform present is from feces.