Cattle standing in Pomme de Terre RiverThere are countless numbers of bacteria, viruses, and other microorganisms in the environment. Most are beneficial, serving as food for larger organisms, and playing critical roles in biogeochemical cycles such as organic matter decomposition, fixation of nitrogen, and digestion of food. Only about 10 percent — known as pathogens — are harmful and, if ingested by humans, cause illness or even death. Symptoms of waterborne diseases may include gastrointestinal illnesses such as severe diarrhea, nausea, and possibly jaundice as well as headaches and fatigue. However, these symptoms are not associated only with disease-causing organisms in drinking water.

Fecal coliform and E. coli

In water quality monitoring, specific disease-producing (pathogenic) organisms are not easily identified. Testing for them is difficult, expensive, and time-consuming. Instead, fecal coliform and E. coli, two closely related bacteria groups, can indicate the presence of pathogens. E. coli is virtually always present in water along with fecal coliform. Protozoa and microorganisms such as giardia and cryptosporidia also cause disease and may be in water contaminated by animal waste.

The behavior of fecal coliform and E. coli in the environment is complex. Seasonal weather, stream flow, water temperature, proximity to pollution sources, livestock management practices, wildlife activity, and rainfall can all affect the amount of bacteria found in water. In addition, bacteria in stream sediments can survive for extended periods and even grow.

Bacteria sources

Fecal coliform and E. coli found in Minnesota rivers and steams may come from human, pet, livestock, and wildlife waste and are more common in heavily populated or farmed areas. Bacteria may reach surface water through malfunctioning or illicit septic system connections, urban stormwater, manure spills or runoff, and more. Properly managing land-applied manure and manure storage can help reduce bacteria contamination in lakes, rives, and groundwater.

Learn more: PDF icon Bacteria - Sources, Types, Impact on Water Quality - A General Overview