MMSD Clarifiers at Wastewater Treatment Plant

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.


Learn About the Various Aspects of Wastewater Treatment:

drone shot of jones island wastewater treatment plant

Wastewater Treatment Process

Learn the four stages of the wastewater treatment process.

deep underground tunnel in milwaukee

Deep Tunnel

Learn why we need deep tunnels, how they work, and where they are in our system.

image of water pipes

Overflows

Why do overflows happen? MMSD addresses the issue.

combined sewer system graphic

Sewers

How many miles of laterals, city sanitary sewers, regional sewers and Deep Tunnels are there anyway?

tour of jones island wastewater treatment plant

Tours

Learn how you can tour one of our wastewater treatment facilities or our laboratory. 

wisconsin DNR logo on lake michigan

Discharge Permit

The rules from our state and local regulators.