A group of bacteria found in the intestinal tract of humans and animals, and also found in soil. While harmless in themselves, coliform bacteria are commonly used as indicators of the presence of pathogenic organisms and other disease-causing bacteria, such as those that cause typhoid, dysentery, hepatitis A and cholera. Measured in number of bacteria per 100 milliliters of water. Failing septic systems and runoff from feedlots are common sources of fecal coliform in water samples.

Animal sources of bacteria include feedlot and manure runoff, urban runoff and wildlife. Improperly treated human waste may come from overflows of sewage treatment systems in cities and towns, unsewered areas with inadequate community or individual wastewater treatment, or a single home with a failing septic system. Bacteria and other pathogens make river water unsafe for drinking and activities that involve body contact.

Source: MPCA