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Lagoon systems: wastewater treatment plants in New Hampshire

15 plants · 33% of the state · 9 MGD reported by 14 plants

Klarifi identifies 15 publicly owned wastewater treatment plants with lagoon systems in New Hampshire, 33% of the 46 plants in the state (9 MGD reported by 14 plants). The largest is Concord Wastewater Treatment Facility in Concord at 3.2 MGD.

Lagoon systems treat wastewater in large earthen ponds over weeks of retention time, with or without mechanical aeration. They serve thousands of small towns because they are cheap to run, but they struggle with ammonia and nutrient limits, fill with sludge over decades and are the plants most often converted or upgraded when a permit is renewed.

Lagoon systems plants nationwide →All plants in New Hampshire →Largest plants in New Hampshire →

The largest lagoons in New Hampshire

The 15 largest plants with lagoon systems in New Hampshire by average flow, with permit expiry and three-year violation count.
#FacilityCityAvg flow (MGD)NPDES permitExpiresViolations (3y)
1Concord Wastewater Treatment FacilityConcord3.2NH0100901Aug 20279
2Rochester Wastewater Treatment FacilityRochester2.35NH0100668Jun 20283
3Derry, Town Of, Wastewater Treatment PlantDerry1.17NH0100056Feb 201617
4Exeter Wastewater Treatment FacilityExeter1.1NHG58A004Jan 202618
5Hooksett Wastewater Treatment FacilityHooksett0.68NH0100129Sep 20181
6Lancaster Wastewater Treatment FacilityLancaster0.23NH0100145Sep 202537
7Penacook Wastewater Treatment PlantConcord0.18NH0100331Jul 20255
8Waterville Valley Wastewater Treatment PlantWaterville Valley0.14NH0100781Mar 20276
9Epping Wasterwater Treatment FacilityEpping0.13NHG580012Nov 2026122
10Whitefield Wastewater Treatment FacilityWhitefield0.09NHG580002Nov 202621
11W Swanzey WWTFSwanzey0.05NHG580015Nov 2026208
12Charlestown Wastewater Treatment PlantCharlestown0.03NH0100765Sep 202521
13Northumberland Village Water Pollution Control FacilityGroveton0.02NHG581206Nov 202622
14Lisbon Wastewater Treatment FacilityLisbon0.02NHG580421Nov 202625
15Ashland Wastewater Treatment FacilityAshland—NH0100005Jan 20275

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.

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Other technologies in New Hampshire

Activated sludge and clarifiers (19)Oxidation ditches (5)Anaerobic digesters and biogas (15)

Lagoon systems in other states

Iowa (632)Illinois (481)Texas (373)Minnesota (341)Missouri (290)Kansas (288)Ohio (260)Arkansas (238)Oklahoma (197)North Dakota (195)Indiana (189)Michigan (182)

Lagoon systems 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.

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