Wastewater treatment plants in New Hampshire
47 facilities · 49 MGD combined flow
Klarifi tracks 47 publicly owned wastewater treatment plants in New Hampshire with a combined average flow of 49 MGD, serving about 499,193 residents. 16 plants treat more than 1 MGD and 0 more than 10 MGD; 12 use lagoon systems and 15 have digesters or biogas infrastructure. The largest is Nashua WWTP in Nashua at 9.77 MGD. 29 NPDES permits expire this year and 4 next year.
Every plant below links to a profile with average and design flow, the NPDES permit and its expiry, a three-year compliance snapshot and the capital projects planned in its city. Treatment technology and verified contacts are shown with a free Klarifi account.
47 plant locations in New Hampshire; dot size follows average flow. Boundaries: U.S. Census Bureau.
NPDES permits and renewals in New Hampshire
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 New Hampshire
| Facility | City | Avg flow (MGD) | Design (MGD) | NPDES permit | Expires | Violations (3y) |
|---|---|---|---|---|---|---|
| Nashua WWTP | Nashua | 9.77 | 16 | NH0100170 | May 2020 | 78 |
| Wrbp Franklin Wastewater Treatment Plant | Franklin | 5.19 | 11.5 | NH0100960 | Jun 2029 | 26 |
| Concord Wastewater Treatment Facility | Concord | 3.5 | 10.1 | NH0100901 | Aug 2027 | 8 |
| Pierce Island Wastewater Treatment Plant | Portsmouth | 3.28 | 4.8 | NH0100234 | Nov 2028 | 47 |
| Rochester Wastewater Treatment Facility | Rochester | 2.88 | 5 | NH0100668 | Jun 2028 | 3 |
| Leavitt E. Magrath Wastewater Treatment Facility | Hampton | 2.24 | 4.7 | NH0100625 | Feb 2026 | 29 |
| Huckleberry Hill Wastewater Treatment Facility | Dover | 2.18 | 4.7 | NHG58A003 | Jan 2026 | 30 |
| Keene Wastewater Treatment Facility | Keene | 1.87 | 6 | NH0100790 | Nov 2026 | 8 |
| Berlin Pollution Control Facility | Berlin | 1.75 | — | NH0100013 | Jun 2029 | 5 |
| Derry, Town Of, Wastewater Treatment Plant | Derry | 1.46 | 4 | NH0100056 | Feb 2016 | 16 |
Treatment technology for each plant is shown with a free Klarifi account. Create one →
New Hampshire plants by treatment technology
All 47 plants in New Hampshire
Wastewater treatment 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 October 26, 2026.
Wastewater terms: WWTP · POTW · MGD · NPDES permit · Tertiary treatment · Significant industrial user · all terms
Cite this page
Journalists, researchers and educators are welcome to quote these figures. Please credit Klarifi as the source and link to this page.
Klarifi. “Wastewater treatment plants in New Hampshire.” Updated October 26, 2026. https://klarifi.io/facilities/new-hampshireNeed a custom cut of the data for a state, a county or a list of plants? Email info@klarifi.io.