Activated sludge and clarifiers: wastewater treatment plants in Wisconsin
83 plants · 21% of the state · 158 MGD reported by 62 plants
Klarifi identifies 83 publicly owned wastewater treatment plants with activated sludge and clarifiers in Wisconsin, 21% of the 391 plants in the state (158 MGD reported by 62 plants). The largest is Green Bay Metropolitan Sewerage District in Green Bay at 27.53 MGD.
Activated sludge is the standard mechanical process for cities: aeration basins where bacteria consume organic matter, followed by clarifiers that settle the biomass out. These plants are identified by their circular or rectangular clarifiers and by the suspended-growth process code, and they are the main market for blowers, diffusers, clarifier mechanisms and instrumentation.
The largest activated sludge plants in Wisconsin
| # | Facility | City | Avg flow (MGD) | NPDES permit | Expires | Violations (3y) |
|---|---|---|---|---|---|---|
| 1 | Green Bay Metropolitan Sewerage District | Green Bay | 27.53 | WIL065251 | Dec 2030 | 7 |
| 2 | Racine Wastewater Treatment Facility | Racine | 14.44 | WI0025194 | Sep 2019 | 6 |
| 3 | La Crosse City | La Crosse | 10.29 | WI0029581 | Dec 2020 | 0 |
| 4 | Janesville Wastewater Utility | Janesville | 9.98 | WI0030350 | Jun 2025 | 0 |
| 5 | Appleton City WWTF | Appleton | 9.25 | WI0023221 | Mar 2022 | 7 |
| 6 | Fox River Water Pollution Control Center | Brookfield | 8.95 | WI0023469 | Dec 2023 | 10 |
| 7 | Oshkosh Wastewater Treatment F | Oshkosh | 8.49 | WI0025038 | Dec 2023 | 34 |
| 8 | Grand Chute-Menasha West Sewer | Neenah | 5.31 | WI0024686 | Jun 2022 | 3 |
| 9 | Wausau Cty Wastewater Treatment Plt | Wausau | 4.39 | WI0025739 | Dec 2023 | 0 |
| 10 | Beloit Wastewater Treatment Facility | Beloit | 3.79 | WI0023370 | Sep 2025 | 37 |
| 11 | Waukesha Waste Water Treatment Plant | Waukesha | 3.15 | WI0029971 | Jun 2018 | 3 |
| 12 | Rib Mountain Sewage Dist | Wausau | 2.94 | WI0035581 | Dec 2023 | 3 |
| 13 | Watertown Wastewater Treatment | Watertown | 2.81 | WI0028541 | Sep 2025 | 0 |
| 14 | Stevens Point Wastewater Treatment Facility | Stevens Point | 2.59 | WI0029572 | Dec 2023 | 2 |
| 15 | Delafield Hartland Pollution C | Delafield | 2.33 | WI0032026 | Sep 2025 | 1 |
| 16 | Wisconsin Rapids WWTF | Wisconsin Rapids | 2.32 | WI0025844 | Jun 2023 | 1 |
| 17 | Heart Of The Valley Metro Sewage District | Kaukauna | 2.21 | WI0031232 | Dec 2023 | 1 |
| 18 | South Milwaukee Wastewater Tre | South Milwaukee | 2.18 | WI0028819 | Dec 2020 | 1 |
| 19 | Reedsburg Wastewater Treatment Facility | Reedsburg | 2.02 | WI0020371 | Jun 2023 | 3 |
| 20 | Chippewa Falls WWTP | Chippewa Falls | 1.81 | WI0023604 | Sep 2025 | 11 |
| 21 | Shawano Lake Sanitary District 1 | Shawano | 1.71 | WI0028452 | Sep 2022 | 2 |
| 22 | Wpsc Marinette Mgp | Marinette | 1.55 | WI0026182 | Sep 2022 | 34 |
| 23 | Portage Wastewater Treatment Facility | Portage | 1.52 | WI0020427 | Sep 2021 | 32 |
| 24 | Monroe Wastewater Treatment Facility | Monroe | 1.5 | WI0020362 | Dec 2025 | 17 |
| 25 | Rice Lake Wastewater Plt | Rice Lake | 1.45 | WI0021865 | Dec 2025 | 0 |
Contacts and project signals for every plant on this list
Klarifi adds verified decision-maker contacts, permit limits, discharge monitoring data and the capital projects planned in each city, filterable by technology, size and compliance record.
Other technologies in Wisconsin
Activated sludge and clarifiers in other states
Activated sludge and clarifiers 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.