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Nitrates in Wisconsin Drinking Water
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Nitrates show up more than any other contaminate in Wisconsin drinking water supplies. The most common sources of nitrates include fertilizers, animal feedlots and waste storage sites, sludge disposal, and refuse disposal areas. Septic systems and other sources contribute much less.Groundwater is a source for most of the 608 public water supply wells systems in Wisconsin. At least 15 of these 608 have been required to install nitrate removal systems or drill new wells at a total cost to municipal taxpayers in excess of $10 million. This cost is just for installation and does not include the cost of maintaining the nitrate removal system.
Nitrates are seldom detected in areas with limited pollution sources, such as northern Wisconsin. However, elevated nitrate concentrations can occur anywhere in the State.
The federal and state groundwater standard for nitrates, measured as nitrogen, is 10 parts per million (mg/L). This maximum contaminant level standard is based on the risk of methemoglobenemia, or "blue baby syndrome," in infants. According to a recent study by Wisconsin Department of Agriculture, Trade, and Consumer Protection, approximately 10% of Wisconsin wells exceed the groundwater standard.
Without a reduction of nitrate loading to Wisconsin's groundwater, nitrate contamination likely will continue and most likely will affect larger areas. Nitrate loading can be managed through regulation of nitrogen-containing wastewater, animal feedlots, and private septic systems. More importantly, nitrate loading can and should be managed within municipalities' well head protection areas to ensure safe drinking water for communities.
