Total coliforms are indicator organisms used to detect bacterial contamination in drinking water. Their presence indicates that a pathway for contamination exists and organisms that cause disease may be present, even though total coliforms themselves typically do not cause disease in healthy individuals. However, one species of total coliform (E. coli) is found in the feces of warm blooded animals. The presence of E.coli in a drinking water sample is an indication of fecal contamination of the water supply.
Surface water may be tested for E. coli. The only natural habitat of E. coli is the intestinal tract of warm-blooded animals. The recreational water guideline is less than 235 MPN/100 mL. An advisory is recommended between and 235 MPN/100 mL and 1000 MPN/100 mL. A closure is recommended at greater than 1000 MPN/100 mL.
High nitrate levels in drinking water pose a risk to infants. Infants under six months of age who are fed water or formula made with water that is high in nitrate can develop a condition called methemoglobinemia or “blue baby syndrome.” State and federal laws set the maximum allowable level for nitrate-nitrogen in public drinking water at 10 milligrams per liter (ppm).
There are a variety of other contaminants that can make their way into your water supply. Inorganic chemicals, volitle organic compounds, pesticides, and heavy metals such as lead or arsenic can all cause severe health effects. If you suspect your water has been contaminated or would like further testing, the Wisconsin State Lab of Hygiene has a variety of tests available for homeowners.