Anaerobic digesters and biogas: wastewater treatment plants in Maine
26 plants · 28% of the state · 16 MGD combined
Klarifi identifies 26 publicly owned wastewater treatment plants with anaerobic digesters and biogas in Maine, 28% of the 92 plants in the state (16 MGD combined). The largest is Westbrook Waste Water Treatmemt Facility in Westbrook at 3.05 MGD.
Anaerobic digesters stabilise sludge in sealed heated tanks and produce biogas, visible from the air as digester silos and gas holders. Plants with digesters are typically above 5 MGD and are the buyers of mixing, heating, gas handling, cogeneration and dewatering equipment.
The largest plants with anaerobic digesters in Maine
| # | Facility | City | Avg flow (MGD) | NPDES permit | Expires | Violations (3y) |
|---|---|---|---|---|---|---|
| 1 | Westbrook Waste Water Treatmemt Facility | Westbrook | 3.05 | ME0100846 | Jul 2022 | 26 |
| 2 | Brewer Wastewater Treatment Facility | Brewer | 1.47 | ME0100072 | Nov 2029 | 2 |
| 3 | Sanford Wastewater Treatment Facility | Sanford | 1.42 | ME0100617 | Jul 2023 | 4 |
| 4 | Old Town Wastewater Treatment Facility | Old Town | 1.09 | ME0100471 | Sep 2029 | 2 |
| 5 | Old Orchard Beach Wastewater Treatment Facility | Old Orchard Beach | 0.99 | ME0101524 | May 2020 | 13 |
| 6 | York Wastewater Treatment Facility | York | 0.99 | ME0101222 | Mar 2030 | 12 |
| 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 | Ellsworth Water Pollution Control Facility | Ellsworth | 0.74 | ME0102865 | Dec 2022 | 0 |
| 10 | Belfast Wastewater Treatment Facility | Belfast | 0.59 | ME0101532 | Feb 2021 | 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 Maine
Anaerobic digesters and biogas in other states
Anaerobic digesters and biogas 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: Anaerobic digester · Biosolids · Sludge dewatering · Centrate · FOG · Equalization tank · all terms