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 29 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. People often think you can flush anything down the toilet or drain, which 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, efficiently clean about 150 million gallons of water on a dry day and have the capacity to clean up to 630 million gallons a day, which can be needed when it rains.

Thanks to the deep tunnel and many other improvements, we average 2.2 overflows per year (down from 50-60) and have captured and cleaned 98.6% of all the water that's entered the regional sewer system since 1994. The national goal 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 = 98.6%


How we're doing so far this year:


Gallons Treated: 42,354,000,000

Gallons Overflowed: 357,000,000

Total Gallons: 42,711,000,000

MMSD % Treated: 99.16%

MMSD Renewable Energy

Cleaning water is very energy-intensive; therefore, MMSD utilizes renewable energy to reduce energy costs, price volatility, greenhouse gases, and to provide energy security. To reduce our carbon footprint, each water reclamation facility has the capability to generate renewable energy. The Jones Island facility's primary renewable fuel comes from a landfill pipeline, a local renewable energy source recycled into power, saving MMSD ratepayers millions of dollars. The South Shore facility's primary renewable fuel comes from methane gas produced by the digesters. If we do not capture, clean, and burn the methane gas in generators, it would be a waste of energy and instead is savings ratepayers approximately $140,000 in savings each month. MMSD continues to pursue energy reduction and renewable generating technologies to support our 2035 Vision.

The below charts show MMSD’s renewable energy usage, for the last 365 days, at our two water reclamation facilities.


19 % Renewable Energy

As of 06/21/2024 12:00:00 AM


70 % Renewable Energy

As of 06/20/2024 12:00:00 AM

Both Facilities

28 % Renewable Energy

As of 06/19/2024 12:00:00 AM

MMSD’s two Water Reclamation Facilities have similar wet weather capacities; however, the Jones Island facility consumes about 80% of the total energy use, whereas the South Shore facility consumes about 20%. The interplant pipeline interconnects the two facilities’ biosolids processes, and the Milorganite® dryers consume a lot of natural gas, which is why Jones Island consumes more power than the South Shore facility.

This page is automatically updated. The data have not been verified and may contain errors. As data are verified, MMSD reserves the right to make corrections to values as necessary. MMSD is providing this data as is and the user assumes the entire risk of use of this data.

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.