Lagoon systems: wastewater treatment plants in Wisconsin
140 plants · 36% of the state · 29 MGD reported by 116 plants
Klarifi identifies 140 publicly owned wastewater treatment plants with lagoon systems in Wisconsin, 36% of the 394 plants in the state (29 MGD reported by 116 plants). The largest is Fox River Water Pollution Control Center in Brookfield at 10.11 MGD.
Lagoon systems treat wastewater in large earthen ponds over weeks of retention time, with or without mechanical aeration. They serve thousands of small towns because they are cheap to run, but they struggle with ammonia and nutrient limits, fill with sludge over decades and are the plants most often converted or upgraded when a permit is renewed.
The largest lagoons in Wisconsin
| # | Facility | City | Avg flow (MGD) | NPDES permit | Expires | Violations (3y) |
|---|---|---|---|---|---|---|
| 1 | Fox River Water Pollution Control Center | Brookfield | 10.11 | WI0023469 | Dec 2023 | 9 |
| 2 | Portage Wastewater Treatment Facility | Portage | 1.55 | WI0020427 | Sep 2021 | 31 |
| 3 | Arcadia Wastewater Treatment F | Arcadia | 1.25 | WI0023230 | Jun 2025 | 1 |
| 4 | Fontana-Walworth Water Pollution Control Commission | Fontana | 1.06 | WI0036021 | Dec 2023 | 20 |
| 5 | Ashland Sewage Utility | Ashland | 0.95 | WI0030767 | Mar 2022 | 1 |
| 6 | Green Lake Sanitary District | Princeton | 0.65 | WI0036846 | Sep 2022 | 18 |
| 7 | Stanley Wastewater Treatment Facility | Stanley | 0.59 | WI0021857 | Sep 2023 | 32 |
| 8 | Whitehall Wastewater Treatment Facility | Whitehall | 0.52 | WI0030970 | Sep 2024 | 9 |
| 9 | Red Cliff Band WWTF | Bayfield | 0.49 | WI0049727 | Sep 2024 | 31 |
| 10 | Tomahawk Waterworks | Tomahawk | 0.41 | WI0021946 | Dec 2023 | 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
Lagoon systems in other states
Lagoon systems 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 · Biosolids · Lift station · Inflow and infiltration · all terms