Fecal Bacteria
Members of two bacteria groups, coliforms and fecal streptococci, are used to test for contamination from sewage. These bacteria are called "fecal" indicators because they live in the intestinal track of humans and animals and are found in human and animal feces. The fecal indicators themselves are not harmful, but because they live in the same portion of the digestive system where disease-causing microorganisms occur, the presence of these fecal bacteria in a water sample indicates that water might contain microorganisms harmful to human health. Very high levels of fecal bacteria can give water a cloudy appearance, cause unpleasant odors, and increase oxygen demand (see BOD and Dissolved Oxygen). Disinfectants added at the local water treatment plants control microbes in drinking water. Sources of fecal bacteria in surface waters include wastewater treatment plants, on-site septic systems, domestic and wild animal manure, and storm runoff.

Measuring Fecal Bacteria
Fecal bacteria levels in water are determined by incubating a water sample for 24 hours and then counting the number of bacterial colonies that grew during that time. The unit for reporting fecal bacteria is "colony-producing units" per 100 milliliters of water (CPU/100 mL). CPUs/100 mL is used interchangeably with "organisms per 100 mL."

Fecal Bacteria in the Red River
The regulatory standard for fecal bacteria in the water varies by state, and several fecal bacteria indicators can be used. In this region, we use fecal coliform. The regulatory limit in North Dakota is 200 organisms/100 mL of water, which applies only during the recreational season, May 1 to September 30. The regulatory limit in Minnesota is also 200 organisms/100 mL of water.The intent of the regulations is to protect people who use the river for recreation. The level of fecal bacteria and other parameters in treated sewage that is discharged to the Red is checked frequently. The monthly average for treated wastewater from the Fargo and Moorhead Wastewater Treatment Plants is usually less than 100 CPU/100 mL and in most winter months is less than 10 CPU/100 mL. Specific reaches of the Red River, including the Fargo-Moorhead (FM) metropolitan area, and some of its tributaries contain elevated levels of fecal coliform bacteria. State regulatory agencies are developing a water quality management plan as part of TMDL activity, to address and remedy these impairments. The target date for implementing this plan is 2004.

Graph of fecal bacteria levels (CPU/100 mL) for the Red River in the FM metro area for the period July 2001 to July 2003 in relation to the regulatory limit for surface water of 200 CPU/100 mL (red line) intended to protect human health.