Why are coliforms used to indicate water quality?
Drinking water must be free of disease-causing microorganisms, such as viruses, protozoa, fungi or bacteria. To test water for specific disease-causing microorganisms is very time consuming and expensive. In addition, not all laboratories are equipped and approved for these tests. Therefore, water testing is generally limited to investigating the number of colony-forming bacteria. The number of these bacterial colonies – the coliform count – is used as an indicator of sanitary conditions. High coliform counts in water indicate that it not safe for drinking or food preparation, as other disease-causing microorganisms, such as viruses and parasites, may also be present.
