Activated sludge and clarifiers: wastewater treatment plants in Maine
46 plants · 50% of the state · 26 MGD combined
Klarifi identifies 46 publicly owned wastewater treatment plants with activated sludge and clarifiers in Maine, 50% of the 92 plants in the state (26 MGD combined). The largest is Bangor Wastewater Treatment Facility in Bangor at 7.09 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 Maine
| # | Facility | City | Avg flow (MGD) | NPDES permit | Expires | Violations (3y) |
|---|---|---|---|---|---|---|
| 1 | Bangor Wastewater Treatment Facility | Bangor | 7.09 | ME0100781 | Jul 2031 | 14 |
| 2 | Westbrook Waste Water Treatmemt Facility | Westbrook | 3.05 | ME0100846 | Jul 2022 | 26 |
| 3 | Brewer Wastewater Treatment Facility | Brewer | 1.47 | ME0100072 | Nov 2029 | 2 |
| 4 | Sanford Wastewater Treatment Facility | Sanford | 1.42 | ME0100617 | Jul 2023 | 4 |
| 5 | Old Town Wastewater Treatment Facility | Old Town | 1.09 | ME0100471 | Sep 2029 | 2 |
| 6 | Old Orchard Beach Wastewater Treatment Facility | Old Orchard Beach | 0.99 | ME0101524 | May 2020 | 13 |
| 7 | Gardiner WWTF | Gardiner | 0.97 | ME0101702 | Oct 2021 | 1 |
| 8 | Bar Harbor WWTF Main Facility | Bar Harbor | 0.91 | ME0101214 | Jan 2021 | 9 |
| 9 | Falmouth Waste Water Treatment Facility | Falmouth | 0.89 | ME0100218 | Dec 2023 | 3 |
| 10 | Anson Madison Wastewater Treatment Facility | Madison | 0.67 | ME0101389 | Apr 2031 | 2 |
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 Maine
Activated sludge and clarifiers in other states
Activated sludge and clarifiers in Maine: 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 · MGD · Lift station · all terms