Wastewater Treatment Plants in Maine
84 facilities · 18 MGD combined flow
Klarifi tracks 84 publicly owned wastewater treatment plants in Maine with a combined average flow of 18 MGD, serving about 241,296 residents. 2 plants treat more than 1 MGD and 0 more than 10 MGD; 30 use lagoon systems and 22 have digesters or biogas infrastructure. The largest is Bangor Wastewater Treatment Facility in Bangor at 4.38 MGD. 3 NPDES permits expire this year and 6 next year.
Every plant below links to a profile with average and design flow, treatment technology, the NPDES permit and its expiry, a three-year compliance snapshot and the capital projects planned in its city.
84 plant locations in Maine; dot size follows average flow.
NPDES permits and renewals in Maine
Every plant discharges under an NPDES permit that is renewed every five years, usually with tighter limits. The renewal year is the year a plant budgets for upgrades.
Largest wastewater treatment plants in Maine
| Facility | City | Avg flow (MGD) | Design (MGD) | NPDES permit | Expires | Technology | Violations (3y) |
|---|---|---|---|---|---|---|---|
| Bangor Wastewater Treatment Facility | Bangor | 4.38 | 18 | ME0100781 | Jul 2031 | Clarifiers | 14 |
| Westbrook Waste Water Treatmemt Facility | Westbrook | 2.5 | 4.54 | ME0100846 | Jul 2022 | Biogas balloons | 26 |
| Old Orchard Beach Wastewater Treatment Facility | Old Orchard Beach | 0.9 | 3.5 | ME0101524 | May 2020 | Clarifiers, Biogas balloons | 11 |
| Bar Harbor WWTF Main Facility | Bar Harbor | 0.82 | 2 | ME0101214 | Jan 2021 | Biogas balloons | 9 |
| Falmouth Waste Water Treatment Facility | Falmouth | 0.7 | 1.56 | ME0100218 | Dec 2023 | — | 3 |
| York Wastewater Treatment Facility | York | 0.67 | 3 | ME0101222 | Mar 2030 | Biogas balloons | 12 |
| Old Town Wastewater Treatment Facility | Old Town | 0.63 | 3.5 | ME0100471 | Sep 2029 | Biogas balloons | 2 |
| Anson Madison Wastewater Treatment Facility | Madison | 0.6 | 7.84 | ME0101389 | Apr 2031 | Clarifiers, Aerated lagoons, Uncovered lagoons | 2 |
| Ogunquit Wastewater Treatment Facility | Ogunquit | 0.54 | 1.28 | ME0100986 | Nov 2023 | Clarifiers, Uncovered lagoons, Biogas balloons | 8 |
| Yarmouth Wastewater Treatiment Facility | Yarmouth | 0.44 | 1.31 | ME0100765 | Aug 2022 | Carrousels / oxidation ditches, Biogas balloons | 3 |
| Belfast Wastewater Treatment Facility | Belfast | 0.42 | 1.49 | ME0101532 | Feb 2021 | Biogas balloons | 0 |
| Lisbon Wastewater Treatment Facility | Lisbon | 0.37 | 2.03 | ME0100307 | Oct 2029 | Biogas silos | 4 |
| Calais Wastewater Treatment Facility | Calais | 0.34 | 1.5 | ME0100129 | Nov 2021 | Biogas balloons | 11 |
| Camden Wastewater Treatment Facility | Camden | 0.32 | 1.21 | ME0100137 | Dec 2023 | Clarifiers | 6 |
| Skowhegan Wastewater Treatment Facility | Skowhegan | 0.31 | 1.44 | ME0100625 | Apr 2031 | Clarifiers, Aerated lagoons, Biogas balloons | 90 |
| Livermore Falls WWTF | Livermore Falls | 0.27 | 2 | ME0100315 | Oct 2029 | — | 14 |
| Kennebunkport Wastewater Treatment Facility | Kennebunkport | 0.26 | 0.7 | ME0101184 | Nov 2026 | Biogas balloons | 27 |
| Madawaska WWTF | Madawaska | 0.23 | 0.6 | ME0101681 | Dec 2024 | — | 6 |
| Freeport Wastewater Treatment Facility | Freeport | 0.23 | 0.75 | ME0101036 | Feb 2021 | Biogas balloons | 4 |
| Bucksport Wastewater Treatment Facility | Bucksport | 0.23 | 0.46 | ME0100111 | Jan 2023 | Biogas silos, Biogas balloons | 9 |
| South Berwick Sd WWTF | South Berwick | 0.2 | 0.37 | ME0100820 | Jun 2030 | — | 2 |
| Ft Fairfield Wastewater Treatment Facility | Fort Fairfield | 0.16 | 0.6 | ME0100226 | May 2022 | Uncovered lagoons | 11 |
| Fort Kent WWTF | Fort Kent | 0.15 | 0.43 | ME0102369 | Dec 2021 | Aerated lagoons, Uncovered lagoons | 2 |
| Newport Wastewater Treatement Facility | Newport | 0.14 | 0.52 | ME0100447 | Mar 2028 | Aerated lagoons, Carrousels / oxidation ditches | 2 |
| South Cape Elizabeth WWTF | Cape Elizabeth | 0.14 | 0.5 | ME0102121 | Dec 2021 | Carrousels / oxidation ditches | 15 |
Maine plants by treatment technology
All 84 plants in Maine
Wastewater treatment 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 September 11, 2026.