Activated sludge and clarifiers: wastewater treatment plants in Wisconsin
85 plants · 22% of the state · 251 MGD reported by 66 plants
Klarifi identifies 85 publicly owned wastewater treatment plants with activated sludge and clarifiers in Wisconsin, 22% of the 394 plants in the state (251 MGD reported by 66 plants). The largest is EPA Superfund Site: Madison Metropolitan Sewerage District Lagoons in Madison at 39.37 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 | EPA Superfund Site: Madison Metropolitan Sewerage District Lagoons | Madison | 39.37 | WIG009756 | Sep 2026 | 2 |
| 2 | Green Bay Metropolitan Sewerage District | Green Bay | 36.81 | WIL065251 | Dec 2030 | 7 |
| 3 | Racine Wastewater Treatment Facility | Racine | 20.89 | WI0025194 | Sep 2019 | 6 |
| 4 | Neenah-Menasha Sewerage Commission WWTF | Menasha | 12.33 | WI0026085 | Jun 2022 | 194 |
| 5 | Janesville Wastewater Utility | Janesville | 11.03 | WI0030350 | Jun 2025 | 0 |
| 6 | Oshkosh Wastewater Treatment F | Oshkosh | 10.56 | WI0025038 | Dec 2023 | 33 |
| 7 | La Crosse City | La Crosse | 10.21 | WI0029581 | Dec 2020 | 0 |
| 8 | Fox River Water Pollution Control Center | Brookfield | 10.11 | WI0023469 | Dec 2023 | 9 |
| 9 | Appleton City WWTF | Appleton | 9.3 | WI0023221 | Mar 2022 | 7 |
| 10 | Grand Chute-Menasha West Sewer | Neenah | 6.52 | WI0024686 | Jun 2022 | 3 |
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 October 26, 2026.
Wastewater terms: Activated sludge · Biological nutrient removal · Equalization tank · Sludge dewatering · Tertiary treatment · all terms