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 our water, your home, and our systems.

Our two water reclamation facilities, Jones Island and South Shore, can efficiently clean about 150 million gallons of water on a dry day and 630 million gallons of water a day when it is raining. 

Thanks to the deep tunnel and many other improvements, we average 2.3 overflows per year (down from 50-60) and have captured and cleaned 98.5% of all the water that's entered the regional sewer system since 1994. The goal nationally is to capture and clean 85% of water for 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.

Environmental Protection Agency (EPA) Goal for capturing and cleaning wastewater = 85%

MMSD's performance since 1994 = 98.5%


Here's how we're doing so far this year:

2022 Volume treated

Gallons Treated: 29,442,000,000

Gallons Overflowed: 0

Total Gallons: 29,442,000,000

MMSD % Treated: 100.00%

MMSD Renewable Energy

Sustainability is a rich part of MMSD's history, integral to present-day operations, and critical to our future. However, cleaning water is very energy-intensive. Therefore, MMSD utilizes renewable energy to reduce energy costs, price volatility, greenhouse gases and provides energy security. Shown below is our renewable energy usage, for the last 365 days, at our two water reclamation facilities. 


20 % Renewable Energy

As of 06/29/2022 12:00:00 AM


65 % Renewable Energy

As of 06/27/2022 12:00:00 AM

Both Facilities

29 % Renewable Energy

As of 06/27/2022 12:00:00 AM

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


Why do overflows happen? MMSD addresses the issue.

combined sewer system graphic


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

tour of jones island wastewater treatment plant


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

wisconsin DNR logo on lake michigan

Discharge Permit

Federal and Wisconsin law requires the MMSD to have a discharge permit. Learn what the permit includes, and how it protects public health and the environment.