Wastewater Treatment Plants in Wisconsin
391 facilities · 308 MGD combined flow
Klarifi tracks 391 publicly owned wastewater treatment plants in Wisconsin with a combined average flow of 308 MGD, serving about 2,897,609 residents. 50 plants treat more than 1 MGD and 4 more than 10 MGD; 161 use lagoon systems and 144 have digesters or biogas infrastructure. The largest is Milwaukee Metro Sew Dist Combi in Milwaukee at 95.1 MGD. 11 NPDES permits expire this year and 1 next year.
Every plant below links to a profile with average and design flow, treatment technology, the NPDES permit and its expiry, a three-year compliance snapshot and the capital projects planned in its city. Showing facilities 1–200 of 391 by average flow — browse the rest with the page links below.
390 plant locations in Wisconsin; dot size follows average flow.
NPDES permits and renewals in Wisconsin
Every plant discharges under an NPDES permit that is renewed every five years, usually with tighter limits. The renewal year is the year a plant budgets for upgrades.
Largest wastewater treatment plants in Wisconsin
| Facility | City | Avg flow (MGD) | Design (MGD) | NPDES permit | Expires | Technology | Violations (3y) |
|---|---|---|---|---|---|---|---|
| Milwaukee Metro Sew Dist Combi | Milwaukee | 95.1 | 123 | WI0036820 | Mar 2024 | — | 392 |
| Green Bay Metropolitan Sewerage District | Green Bay | 27.53 | — | WIL065251 | Dec 2030 | Clarifiers, Carrousels / oxidation ditches, Biogas silos, Biogas balloons | 7 |
| Racine Wastewater Treatment Facility | Racine | 14.44 | 30 | WI0025194 | Sep 2019 | Clarifiers, Biogas silos, Biogas balloons | 6 |
| La Crosse City | La Crosse | 10.29 | 20 | WI0029581 | Dec 2020 | Clarifiers, Biogas silos, Biogas balloons | 0 |
| Janesville Wastewater Utility | Janesville | 9.98 | 17.18 | WI0030350 | Jun 2025 | Clarifiers, Biogas silos, Biogas balloons | 0 |
| Appleton City WWTF | Appleton | 9.25 | — | WI0023221 | Mar 2022 | Clarifiers, Uncovered lagoons, Biogas silos, Biogas balloons | 7 |
| Fox River Water Pollution Control Center | Brookfield | 8.95 | 10 | WI0023469 | Dec 2023 | Clarifiers, Uncovered lagoons, Biogas silos, Biogas balloons | 10 |
| Oshkosh Wastewater Treatment F | Oshkosh | 8.49 | 20 | WI0025038 | Dec 2023 | Clarifiers, Biogas silos | 34 |
| Grand Chute-Menasha West Sewer | Neenah | 5.31 | 3.9 | WI0024686 | Jun 2022 | Clarifiers, Biogas silos | 3 |
| Wausau Cty Wastewater Treatment Plt | Wausau | 4.39 | 9.2 | WI0025739 | Dec 2023 | Clarifiers, Biogas silos, Biogas balloons | 0 |
| Beloit Wastewater Treatment Facility | Beloit | 3.79 | 9.5 | WI0023370 | Sep 2025 | Clarifiers, Biogas silos, Biogas balloons | 37 |
| Waukesha Waste Water Treatment Plant | Waukesha | 3.15 | 16 | WI0029971 | Jun 2018 | Clarifiers, Biogas silos, Biogas balloons | 3 |
| Rib Mountain Sewage Dist | Wausau | 2.94 | 4.94 | WI0035581 | Dec 2023 | Clarifiers, Uncovered lagoons, Biogas silos | 3 |
| Burlington Water Pollution Control | Burlington | 2.88 | 2.5 | WI0022926 | Dec 2019 | — | 0 |
| Watertown Wastewater Treatment | Watertown | 2.81 | 5.2 | WI0028541 | Sep 2025 | Clarifiers | 0 |
| Stevens Point Wastewater Treatment Facility | Stevens Point | 2.59 | 4.1 | WI0029572 | Dec 2023 | Clarifiers, Biogas silos, Biogas balloons | 2 |
| Sussex Wastewater Treatment Facility | Sussex | 2.57 | 1 | WI0020559 | Dec 2024 | Carrousels / oxidation ditches, Biogas balloons | 3 |
| Marshfield Wastewater Utility | Marshfield | 2.42 | 3.5 | WI0021024 | Sep 2023 | Carrousels / oxidation ditches, Biogas balloons | 4 |
| Delafield Hartland Pollution C | Delafield | 2.33 | 2.2 | WI0032026 | Sep 2025 | Clarifiers, Biogas silos | 1 |
| Wisconsin Rapids WWTF | Wisconsin Rapids | 2.32 | 4 | WI0025844 | Jun 2023 | Clarifiers, Biogas silos | 1 |
| Heart Of The Valley Metro Sewage District | Kaukauna | 2.21 | 5.5 | WI0031232 | Dec 2023 | Clarifiers, Biogas silos, Biogas balloons, Cooling towers | 1 |
| South Milwaukee Wastewater Tre | South Milwaukee | 2.18 | 6 | WI0028819 | Dec 2020 | Clarifiers, Biogas silos, Biogas balloons | 1 |
| Reedsburg Wastewater Treatment Facility | Reedsburg | 2.02 | 1.4 | WI0020371 | Jun 2023 | Clarifiers, Biogas balloons | 3 |
| Chippewa Falls WWTP | Chippewa Falls | 1.81 | 5.61 | WI0023604 | Sep 2025 | Clarifiers, Biogas silos | 11 |
| Menomonie Wastewater Treatment Facility | Menomonie | 1.72 | 2.88 | WI0024708 | Sep 2025 | — | 4 |
Wisconsin plants by treatment technology
All 391 plants in Wisconsin
Wastewater treatment 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.