Milwaukee County has confirmed cases of Coronavirus Disease 2019 (COVID-19) and more cases have been identified in the U.S. It's important that everyone take steps to reduce the spread. Find out more about COVID-19 and our ongoing response.

Wastewater Treatment

How Does MMSD Treat Wastewater?

The Milwaukee Metropolitan Sewerage District (MMSD) cleans billions of gallons of wastewater every year, safeguarding natural resources and protecting public health for 28 communities in southeastern Wisconsin. We treat a range of wastewater sources from industrial to surface runoff and whatever water you send down the drain at home, work, school or church. Often people think you can flush anything down the toilet or drain and that is not true. Learn what not to flush to protect your home and our system.

Thanks to the deep tunnel and many other improvements, we average 2.4 overflows per year (down from 50-60) and have captured and cleaned 98.4% of all the water that's entered the regional sewer system since 1994. The goal nationally is to capture and clean 85% for the more than 700 cities with systems like ours. We continue to strive for zero overflows by investing in our treatment plants, sewers and implementing green infrastructure in our region to help manage water where it falls.