New UW-Extension resource describes risk to public health from untreated drinking water

drinking waterContact Madeline B. Gotkowitz, 608-262-1580, or David S. Liebl, 608-265-2360,

Madison, Wis.–New research reveals that groundwater can be contaminated by viruses from untreated sewage. While the majority of the state’s municipalities disinfect their public water supplies, about 60 systems that serve the public do not currently offer this protection.

Around four million, or 70 percent, of all Wisconsin residents get their drinking water from one of over 600 municipal water systems. Several larger communities, such as Milwaukee, Green Bay and Appleton, use surface water that comes from lakes. These systems, which serve about 1.8 million residents, are required by federal and state laws to disinfect the water to remove disease-causing agents, or pathogens.

In the past, the state’s abundant supply of groundwater has allowed communities to develop public water supplies without the treatment required for disinfection. Disinfection is critical to eliminate water-borne diseases caused by pathogens, such as bacteria and viruses. But the new research shows that even groundwater can become contaminated with pathogens from leaky municipal sewer systems and other sources that can cause illness.

A new fact sheet produced by the Wisconsin Geological and Natural History Survey and the UW-Extension Solid and Hazardous Waste Education Center titled Municipal Drinking Water Safety: The Link Between Groundwater, Pathogens and Public Health can help communities navigate the process of ensuring their drinking water is safe. It identifies communities that do not provide treatment; explains what contaminants have been found in groundwater; shows how to test for pathogens; discusses the link between drinking water and illness; and describes methods for maintaining a sanitary public water supply.

The fact sheet is available from the Wisconsin Geological and Natural History Survey at


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