The 50 largest wastewater treatment plants in Wisconsin
Ranked by average flow · 363 MGD combined · 85% of the state's reported flow
Milwaukee Metro Sew Dist Combi in Milwaukee is the largest publicly owned wastewater treatment plant in Wisconsin by reported average flow, treating about 103.5 million gallons per day. The 50 plants below treat 363 MGD between them, 85% of the flow reported by all 394 plants in the state, and serve about 2,179,513 people. Every plant links to its profile with permit and compliance data. Treatment technology is shown with a free Klarifi account.
| # | Facility | City | Avg flow (MGD) | Population | NPDES permit | Expires | Violations (3y) |
|---|---|---|---|---|---|---|---|
| 1 | Milwaukee Metro Sew Dist Combi | Milwaukee | 103.5 | 531,068 | WI0036820 | Mar 2024 | 392 |
| 2 | EPA Superfund Site: Madison Metropolitan Sewerage District Lagoons | Madison | 39.37 | 359,595 | WIG009756 | Sep 2026 | 2 |
| 3 | Green Bay Metropolitan Sewerage District | Green Bay | 36.81 | — | WIL065251 | Dec 2030 | 7 |
| 4 | Racine Wastewater Treatment Facility | Racine | 20.89 | 134,178 | WI0025194 | Sep 2019 | 6 |
| 5 | Neenah-Menasha Sewerage Commission WWTF | Menasha | 12.33 | 67,716 | WI0026085 | Jun 2022 | 194 |
| 6 | Janesville Wastewater Utility | Janesville | 11.03 | 63,000 | WI0030350 | Jun 2025 | 0 |
| 7 | Oshkosh Wastewater Treatment F | Oshkosh | 10.56 | 78,158 | WI0025038 | Dec 2023 | 33 |
| 8 | La Crosse City | La Crosse | 10.21 | 84,678 | WI0029581 | Dec 2020 | 0 |
| 9 | Fox River Water Pollution Control Center | Brookfield | 10.11 | 58,930 | WI0023469 | Dec 2023 | 9 |
| 10 | Appleton City WWTF | Appleton | 9.3 | 74,098 | WI0023221 | Mar 2022 | 7 |
| 11 | Grand Chute-Menasha West Sewer | Neenah | 6.52 | 36,713 | WI0024686 | Jun 2022 | 3 |
| 12 | Hartford Water Pollution Control Facility | Hartford | 5.48 | 14,423 | WI0020192 | Sep 2023 | 7 |
| 13 | Wausau Cty Wastewater Treatment Plt | Wausau | 5.3 | 42,857 | WI0025739 | Dec 2023 | 0 |
| 14 | Heart Of The Valley Metro Sewage District | Kaukauna | 4.54 | 49,948 | WI0031232 | Dec 2023 | 1 |
| 15 | Beloit Wastewater Treatment Facility | Beloit | 4.15 | 36,269 | WI0023370 | Sep 2025 | 37 |
| 16 | Watertown Wastewater Treatment | Watertown | 3.51 | 24,743 | WI0028541 | Sep 2025 | 0 |
| 17 | Rib Mountain Sewage Dist | Wausau | 3.48 | 37,721 | WI0035581 | Dec 2023 | 3 |
| 18 | City Of Sun Prairie Site | Sun Prairie | 3.41 | 30,909 | WI0020478 | Sep 2023 | 0 |
| 19 | Waukesha Waste Water Treatment Plant | Waukesha | 3.33 | 72,784 | WI0029971 | Jun 2018 | 3 |
| 20 | Burlington Water Pollution Control | Burlington | 3.21 | 12,426 | WI0022926 | Dec 2019 | 0 |
| 21 | Marshfield Wastewater Utility | Marshfield | 2.9 | 19,144 | WI0021024 | Sep 2023 | 4 |
| 22 | Wisconsin Rapids WWTF | Wisconsin Rapids | 2.88 | 13,392 | WI0025844 | Jun 2023 | 1 |
| 23 | South Milwaukee Wastewater Tre | South Milwaukee | 2.85 | 21,000 | WI0028819 | Dec 2020 | 1 |
| 24 | Stevens Point Wastewater Treatment Facility | Stevens Point | 2.77 | 28,196 | WI0029572 | Dec 2023 | 2 |
| 25 | Sussex Wastewater Treatment Facility | Sussex | 2.75 | 16,684 | WI0020559 | Dec 2024 | 3 |
| 26 | Fort Atkinson Wastewater Treat | Fort Atkinson | 2.45 | 12,390 | WI0022489 | Jun 2024 | 0 |
| 27 | Cedarburg Water Recycling Center | Cedarburg | 2.33 | 11,600 | WI0020222 | Mar 2022 | 1 |
| 28 | Delafield Hartland Pollution C | Delafield | 2.24 | 19,751 | WI0032026 | Sep 2025 | 1 |
| 29 | Shawano Lake Sanitary District 1 | Shawano | 2.22 | 18,080 | WI0028452 | Sep 2022 | 2 |
| 30 | Reedsburg Wastewater Treatment Facility | Reedsburg | 1.93 | 10,000 | WI0020371 | Jun 2023 | 3 |
| 31 | City Of Plymouth | Plymouth | 1.93 | 8,932 | WI0030031 | Dec 2023 | 18 |
| 32 | Wpsc Marinette Mgp | Marinette | 1.89 | 10,968 | WI0026182 | Sep 2022 | 34 |
| 33 | Chippewa Falls WWTP | Chippewa Falls | 1.81 | 14,000 | WI0023604 | Sep 2025 | 11 |
| 34 | Salem Utility District No 2 | Trevor | 1.71 | — | WI0031496 | Dec 2013 | 1 |
| 35 | Sturgeon Bay Utilities | Sturgeon Bay | 1.7 | 10,013 | WI0021113 | Dec 2025 | 0 |
| 36 | Monroe Wastewater Treatment Facility | Monroe | 1.64 | 11,756 | WI0020362 | Dec 2025 | 17 |
| 37 | Menomonie Wastewater Treatment Facility | Menomonie | 1.6 | 16,187 | WI0024708 | Sep 2025 | 4 |
| 38 | Whitewater City WWTF | Whitewater | 1.57 | 14,611 | WI0020001 | Mar 2022 | 19 |
| 39 | Portage Wastewater Treatment Facility | Portage | 1.55 | 10,704 | WI0020427 | Sep 2021 | 31 |
| 40 | Port Washington WWTP | Port Washington | 1.5 | 11,672 | WI0020460 | Mar 2026 | 20 |
| 41 | Ripon Wastewater Treatment Plt (duplicate) | Ripon | 1.48 | 7,733 | WI0021032 | Sep 2025 | 5 |
| 42 | River Falls WWTP | River Falls | 1.4 | 15,418 | WI0029394 | Jun 2025 | 0 |
| 43 | Wi Dells Lake Delton Sew Comm | Lake Delton | 1.38 | 5,827 | WI0031402 | Mar 2022 | 0 |
| 44 | Antigo City Of | Antigo | 1.34 | 8,234 | WI0022144 | Dec 2019 | 5 |
| 45 | Sparta Wastewater Treatment Facility | Sparta | 1.33 | 9,353 | WI0020737 | Mar 2025 | 2 |
| 46 | Waupun City WWTF | Waupun | 1.32 | 11,098 | WI0022772 | Jun 2021 | 16 |
| 47 | New London Wastewater Treatmen | New London | 1.31 | 7,500 | WI0024929 | Mar 2022 | 0 |
| 48 | Baraboo Water Resource Recovery Facility | Baraboo | 1.31 | 13,847 | WI0020605 | Jun 2018 | 0 |
| 49 | Rice Lake Wastewater Plt | Rice Lake | 1.28 | 8,741 | WI0021865 | Dec 2025 | 0 |
| 50 | Arcadia Wastewater Treatment F | Arcadia | 1.25 | 2,468 | WI0023230 | Jun 2025 | 1 |
Treatment technology for each plant is shown with a free Klarifi account. Create one →
Largest plants in Wisconsin: questions
Sources and methodology
Flow, permit and violation figures come from the EPA's ICIS-NPDES discharge monitoring records. Population served comes from the Clean Watersheds Needs Survey 2022. Treatment structures are identified by Klarifi's review of aerial imagery, and capital improvement projects are extracted from published municipal budget documents. Violations are counted over the last three years of monitoring reports.
Data refreshed October 26, 2026.
Wastewater terms: WWTP · POTW · MGD · NPDES permit · Inflow and infiltration · Sludge dewatering · all terms
Cite this page
Journalists, researchers and educators are welcome to quote these figures. Please credit Klarifi as the source and link to this page.
Klarifi. “Largest wastewater treatment plants in Wisconsin (2026).” Updated October 26, 2026. https://klarifi.io/facilities/wisconsin/largestNeed a custom cut of the data for a state, a county or a list of plants? Email info@klarifi.io.