The 50 largest wastewater treatment plants in Wisconsin
Ranked by average flow · 264 MGD combined · 86% 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 95.1 million gallons per day. The 50 plants below treat 264 MGD between them, 86% of the flow reported by all 391 plants in the state, and serve about 1,735,469 people. Every plant links to its profile with permit, technology and compliance data.
| # | Facility | City | Avg flow (MGD) | Population | NPDES permit | Expires | Technology | Violations (3y) |
|---|---|---|---|---|---|---|---|---|
| 1 | Milwaukee Metro Sew Dist Combi | Milwaukee | 95.1 | 531,068 | WI0036820 | Mar 2024 | — | 392 |
| 2 | Green Bay Metropolitan Sewerage District | Green Bay | 27.53 | — | WIL065251 | Dec 2030 | Clarifiers, Carrousels / oxidation ditches, Biogas silos, Biogas balloons | 7 |
| 3 | Racine Wastewater Treatment Facility | Racine | 14.44 | 134,178 | WI0025194 | Sep 2019 | Clarifiers, Biogas silos, Biogas balloons | 6 |
| 4 | La Crosse City | La Crosse | 10.29 | 84,678 | WI0029581 | Dec 2020 | Clarifiers, Biogas silos, Biogas balloons | 0 |
| 5 | Janesville Wastewater Utility | Janesville | 9.98 | 63,000 | WI0030350 | Jun 2025 | Clarifiers, Biogas silos, Biogas balloons | 0 |
| 6 | Appleton City WWTF | Appleton | 9.25 | 74,098 | WI0023221 | Mar 2022 | Clarifiers, Uncovered lagoons, Biogas silos, Biogas balloons | 7 |
| 7 | Fox River Water Pollution Control Center | Brookfield | 8.95 | 58,930 | WI0023469 | Dec 2023 | Clarifiers, Uncovered lagoons, Biogas silos, Biogas balloons | 10 |
| 8 | Oshkosh Wastewater Treatment F | Oshkosh | 8.49 | 78,158 | WI0025038 | Dec 2023 | Clarifiers, Biogas silos | 34 |
| 9 | Grand Chute-Menasha West Sewer | Neenah | 5.31 | 36,713 | WI0024686 | Jun 2022 | Clarifiers, Biogas silos | 3 |
| 10 | Wausau Cty Wastewater Treatment Plt | Wausau | 4.39 | 42,857 | WI0025739 | Dec 2023 | Clarifiers, Biogas silos, Biogas balloons | 0 |
| 11 | Beloit Wastewater Treatment Facility | Beloit | 3.79 | 36,269 | WI0023370 | Sep 2025 | Clarifiers, Biogas silos, Biogas balloons | 37 |
| 12 | Waukesha Waste Water Treatment Plant | Waukesha | 3.15 | 72,784 | WI0029971 | Jun 2018 | Clarifiers, Biogas silos, Biogas balloons | 3 |
| 13 | Rib Mountain Sewage Dist | Wausau | 2.94 | 37,721 | WI0035581 | Dec 2023 | Clarifiers, Uncovered lagoons, Biogas silos | 3 |
| 14 | Burlington Water Pollution Control | Burlington | 2.88 | 12,426 | WI0022926 | Dec 2019 | — | 0 |
| 15 | Watertown Wastewater Treatment | Watertown | 2.81 | 24,743 | WI0028541 | Sep 2025 | Clarifiers | 0 |
| 16 | Stevens Point Wastewater Treatment Facility | Stevens Point | 2.59 | 28,196 | WI0029572 | Dec 2023 | Clarifiers, Biogas silos, Biogas balloons | 2 |
| 17 | Sussex Wastewater Treatment Facility | Sussex | 2.57 | 16,684 | WI0020559 | Dec 2024 | Carrousels / oxidation ditches, Biogas balloons | 3 |
| 18 | Marshfield Wastewater Utility | Marshfield | 2.42 | 19,144 | WI0021024 | Sep 2023 | Carrousels / oxidation ditches, Biogas balloons | 4 |
| 19 | Delafield Hartland Pollution C | Delafield | 2.33 | 19,751 | WI0032026 | Sep 2025 | Clarifiers, Biogas silos | 1 |
| 20 | Wisconsin Rapids WWTF | Wisconsin Rapids | 2.32 | 13,392 | WI0025844 | Jun 2023 | Clarifiers, Biogas silos | 1 |
| 21 | Heart Of The Valley Metro Sewage District | Kaukauna | 2.21 | 49,948 | WI0031232 | Dec 2023 | Clarifiers, Biogas silos, Biogas balloons, Cooling towers | 1 |
| 22 | South Milwaukee Wastewater Tre | South Milwaukee | 2.18 | 21,000 | WI0028819 | Dec 2020 | Clarifiers, Biogas silos, Biogas balloons | 1 |
| 23 | Reedsburg Wastewater Treatment Facility | Reedsburg | 2.02 | 10,000 | WI0020371 | Jun 2023 | Clarifiers, Biogas balloons | 3 |
| 24 | Chippewa Falls WWTP | Chippewa Falls | 1.81 | 14,000 | WI0023604 | Sep 2025 | Clarifiers, Biogas silos | 11 |
| 25 | Menomonie Wastewater Treatment Facility | Menomonie | 1.72 | 16,187 | WI0024708 | Sep 2025 | — | 4 |
| 26 | Shawano Lake Sanitary District 1 | Shawano | 1.71 | 18,080 | WI0028452 | Sep 2022 | Clarifiers | 2 |
| 27 | Whitewater City WWTF | Whitewater | 1.61 | 14,611 | WI0020001 | Mar 2022 | Cooling towers | 19 |
| 28 | Ripon Wastewater Treatment Plt (duplicate) | Ripon | 1.59 | 7,733 | WI0021032 | Sep 2025 | Carrousels / oxidation ditches, Biogas balloons | 5 |
| 29 | Wpsc Marinette Mgp | Marinette | 1.55 | 10,968 | WI0026182 | Sep 2022 | Clarifiers, Biogas silos, Biogas balloons | 34 |
| 30 | River Falls WWTP | River Falls | 1.53 | 15,418 | WI0029394 | Jun 2025 | — | 0 |
| 31 | Portage Wastewater Treatment Facility | Portage | 1.52 | 10,704 | WI0020427 | Sep 2021 | Clarifiers, Uncovered lagoons, Biogas silos | 32 |
| 32 | Sparta Wastewater Treatment Facility | Sparta | 1.51 | 9,353 | WI0020737 | Mar 2025 | Biogas silos, Biogas balloons | 2 |
| 33 | Monroe Wastewater Treatment Facility | Monroe | 1.5 | 11,756 | WI0020362 | Dec 2025 | Clarifiers, Uncovered lagoons, Biogas silos, Biogas balloons | 17 |
| 34 | Rice Lake Wastewater Plt | Rice Lake | 1.45 | 8,741 | WI0021865 | Dec 2025 | Clarifiers, Biogas silos, Biogas balloons | 0 |
| 35 | Wi Dells Lake Delton Sew Comm | Lake Delton | 1.4 | 5,827 | WI0031402 | Mar 2022 | Clarifiers, Carrousels / oxidation ditches, Biogas silos, Biogas balloons | 0 |
| 36 | Platteville Wastewater Treatment Facility | Platteville | 1.34 | 10,543 | WI0020435 | Jun 2025 | Clarifiers | 0 |
| 37 | Baraboo Water Resource Recovery Facility | Baraboo | 1.29 | 13,847 | WI0020605 | Jun 2018 | Carrousels / oxidation ditches, Biogas balloons | 0 |
| 38 | Antigo City Of | Antigo | 1.21 | 8,234 | WI0022144 | Dec 2019 | Clarifiers | 5 |
| 39 | Arcadia Wastewater Treatment F | Arcadia | 1.19 | 2,468 | WI0023230 | Jun 2025 | Aerated lagoons, Uncovered lagoons | 1 |
| 40 | Salem Utility District No 2 | Trevor | 1.13 | — | WI0031496 | Dec 2013 | Clarifiers, Biogas silos | 1 |
| 41 | Waupaca Wastewater Treatment Facility | Waupaca | 1.11 | 7,975 | WI0030490 | Sep 2024 | Clarifiers | 0 |
| 42 | Tomah Wastewater Treatment Facility | Tomah | 1.11 | 9,494 | WI0021318 | Mar 2024 | Clarifiers, Carrousels / oxidation ditches, Biogas balloons | 54 |
| 43 | Western Racine County Sewerage District | Rochester | 1.08 | 13,610 | WI0028754 | Dec 2020 | Clarifiers, Carrousels / oxidation ditches, Biogas balloons | 5 |
| 44 | New London Wastewater Treatmen | New London | 1.07 | 7,500 | WI0024929 | Mar 2022 | Clarifiers, Biogas silos, Biogas balloons | 0 |
| 45 | Stoughton Wastewater Treatment Facility | Stoughton | 1.06 | 13,272 | WI0020338 | Mar 2025 | Clarifiers, Biogas silos, Biogas balloons | 0 |
| 46 | Sturgeon Bay Utilities | Sturgeon Bay | 1.06 | 10,013 | WI0021113 | Dec 2025 | Clarifiers, Biogas silos | 0 |
| 47 | Jefferson Wastewater Treatment | Jefferson | 1.06 | 7,989 | WI0024333 | Mar 2026 | Clarifiers, Biogas silos, Biogas balloons | 0 |
| 48 | Kiel Wastewater Treatment Facility | Kiel | 1.05 | 3,610 | WI0020141 | Mar 2023 | Clarifiers, Biogas balloons | 1 |
| 49 | Port Washington WWTP | Port Washington | 1.04 | 11,672 | WI0020460 | Mar 2026 | Clarifiers, Biogas silos, Biogas balloons | 20 |
| 50 | Columbus City WWTF | Columbus | 1.03 | 6,126 | WI0021008 | Jun 2025 | Biogas balloons | 2 |
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 September 11, 2026.