Anaerobic digesters and biogas: wastewater treatment plants in New Hampshire
15 plants · 33% of the state · 22 MGD reported by 14 plants
Klarifi identifies 15 publicly owned wastewater treatment plants with anaerobic digesters and biogas in New Hampshire, 33% of the 46 plants in the state (22 MGD reported by 14 plants). The largest is Nashua WWTP in Nashua at 9.2 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 New Hampshire
| # | Facility | City | Avg flow (MGD) | NPDES permit | Expires | Violations (3y) |
|---|---|---|---|---|---|---|
| 1 | Nashua WWTP | Nashua | 9.2 | NH0100170 | May 2020 | 87 |
| 2 | Wrbp Franklin Wastewater Treatment Plant | Franklin | 3.53 | NH0100960 | Jun 2029 | 22 |
| 3 | Pierce Island Wastewater Treatment Plant | Portsmouth | 2.38 | NH0100234 | Nov 2028 | 47 |
| 4 | Merrimack WWTF | Merrimack | 1.37 | NHR053094 | Feb 2026 | 9 |
| 5 | Claremont Wastewater Treatment Facility | Claremont | 1.2 | NH0101257 | Sep 2021 | 0 |
| 6 | Berlin Pollution Control Facility | Berlin | 1.12 | NH0100013 | Jun 2029 | 5 |
| 7 | Hanover Wastewater Treatment Facility | Hanover | 0.99 | NH0100099 | Jan 2021 | 45 |
| 8 | Lebanon Wastewater Treatment Facility | Lebanon | 0.89 | NHR053176 | Feb 2026 | 2 |
| 9 | Milford Wastewater Treatment Facility | Milford | 0.78 | NH0100471 | Oct 2025 | 191 |
| 10 | Newmarket, Town Of - WPCF | Newmarket | 0.35 | NHG580013 | Nov 2026 | 17 |
| 11 | Littleton Wastewater Treatment Plant | Littleton | 0.27 | NH0100153 | Oct 2025 | 17 |
| 12 | Sunapee, Town Of-WWTP | Sunapee | 0.22 | NHG580017 | Nov 2026 | 27 |
| 13 | Henniker Wastewater Treatment Facility | Henniker | 0.11 | NHG580018 | Nov 2026 | 75 |
| 14 | Hinsdale Wastewater Treatment Plant | Hinsdale | 0.07 | NHG580016 | Nov 2026 | 6 |
| 15 | Ashland Wastewater Treatment Facility | Ashland | — | NH0100005 | Jan 2027 | 5 |
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 New Hampshire
Anaerobic digesters and biogas in other states
Anaerobic digesters and biogas in New Hampshire: 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.