Activated sludge and clarifiers: wastewater treatment plants in Minnesota
33 plants · 7% of the state · 89 MGD reported by 26 plants
Klarifi identifies 33 publicly owned wastewater treatment plants with activated sludge and clarifiers in Minnesota, 7% of the 470 plants in the state (89 MGD reported by 26 plants). The largest is Seneca Wastewater Treatment Plant in Eagan at 20.44 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 Minnesota
| # | Facility | City | Avg flow (MGD) | NPDES permit | Expires | Violations (3y) |
|---|---|---|---|---|---|---|
| 1 | Seneca Wastewater Treatment Plant | Eagan | 20.44 | MN0030007 | Nov 2028 | 6 |
| 2 | Met Council - Empire WWTP | Farmington | 11.65 | MNL045845 | Dec 2030 | 0 |
| 3 | Rochester Water Reclamation Plant | Rochester | 11.39 | MN0024619 | Mar 2027 | 1 |
| 4 | Saint Cloud WWTP | St. Cloud | 9.41 | MNL040878 | Dec 2030 | 0 |
| 5 | Met Council - Eagles Point WWTP | Cottage Grove | 5.99 | MN0029904 | Oct 2023 | 0 |
| 6 | Grand Rapids WWTP | Grand Rapids | 5.92 | MN0022080 | Jan 2025 | 7 |
| 7 | Owatonna WWTP | Owatonna | 3.32 | MN0051284 | May 2026 | 10 |
| 8 | Alexandria Lake Area Sanitary District | Alexandria | 2.75 | MN0040738 | Jul 2030 | 0 |
| 9 | Met Council - St Croix Valley WWTP | Oak Park Heights | 2.44 | MN0029998 | May 2027 | 0 |
| 10 | Marshall WWTP | Marshall | 2.15 | MN0022179 | Feb 2029 | 16 |
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 Minnesota
Activated sludge and clarifiers in other states
Activated sludge and clarifiers in Minnesota: 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 · Tertiary treatment · Significant industrial user · all terms