What is the largest nutrient removal plant in Massachusetts?

Upper Blackstone Wastewater Treatment Plant in Millbury, treating about 24.1 MGD under NPDES permit MAR053209.

Which Massachusetts plants are planning nutrient removal upgrades?

2 plants report nutrient removal as a planned process in the EPA needs survey, including Greenfield Water Pollution Control Facility in Greenfield. Planned processes are the earliest public signal of an upgrade.

How are plants with nutrient removal identified?

From two sources: treatment structures counted in Klarifi’s review of aerial imagery (lagoons, clarifiers, oxidation ditches, digester silos and gas holders) and the unit processes each plant reports to the EPA Clean Watersheds Needs Survey. A plant is listed when either source records the technology.

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Nutrient removal: wastewater treatment plants in Massachusetts

Name: Nutrient removal wastewater treatment plants in Massachusetts
Creator: Klarifi
License: https://klarifi.io/terms-of-service

28 plants · 42% of the state · 94 MGD combined

Klarifi identifies 28 publicly owned wastewater treatment plants with nutrient removal in Massachusetts, 42% of the 66 plants in the state (94 MGD combined). The largest is Upper Blackstone Wastewater Treatment Plant in Millbury at 24.1 MGD.

Nutrient removal takes nitrogen and phosphorus out of the effluent, biologically in anoxic and anaerobic zones or chemically with metal salts. It is driven by permit limits and TMDLs on the receiving water and is the largest upgrade a plant can face, which makes these plants the best-documented market for process equipment and chemicals.

Nutrient removal plants nationwide →All plants in Massachusetts →Largest plants in Massachusetts →

The largest plants with nutrient removal in Massachusetts

The 25 largest plants with nutrient removal in Massachusetts by average flow, with permit expiry and three-year violation count.
#	Facility	City	Avg flow (MGD)	NPDES permit	Expires	Violations (3y)
1	Upper Blackstone Wastewater Treatment Plant	Millbury	24.1	MAR053209	Feb 2026	15
2	Greater Lawrence Wastewater Treatment Facility	North Andover	21.7	MAL100447	Dec 2030	10
3	Brockton Advanced Water Reclamation Fac	Brockton	9.9	MAL101010	Dec 2030	10
4	Pittsfield Wastewater Treatment Facility	Pittsfield	7	MA0101681	Oct 2026	84
5	Holyoke Water Pollution Control Facility	Holyoke	5.02	MAL101630	Dec 2030	4
6	Westborough Wastewater Treatment Plant	Westborough	4.17	MA0100412	Apr 2027	2
7	Northampton Wastewater Treatment Plant	Northampton	3.84	MA0101818	Nov 2028	40
8	Amherst Wastewater Treatment Plant	Hadley	3.33	MA0100218	Jan 2029	42
9	Billerica Wastewater Treatment Facility	Billerica	2.88	MA0101711	Feb 2029	52
10	Westfield Wastewater Treatment Plant	Westfield	2.4	MA0101800	Nov 2028	0
11	Hoosic Wastwater Treament Plant	Williamstown	2.04	MA0100510	Dec 2028	2
12	Plymouth Wastewater Treatment Facility	Plymouth	1.31	MAG590040	Oct 2027	5
13	Palmer Water Pollution Control Facility	Palmer (three Rivers)	1.2	MA0101168	Nov 2028	4
14	Westerly Wastewater Treatment Facility	Marlborough	1.16	MA0100480	Dec 2026	26
15	Uxbridge Wastewater Treatment Facility	Uxbridge	0.71	MAG590003	Oct 2027	24
16	Concord Wastewater Treatment Facility	Concord	0.68	MAG590030	Oct 2027	5
17	Orange Wastewater Treatment Plant	Orange	0.61	MAG590019	Oct 2027	508
18	Montague Wastewater Treatment Facility	Montague	0.54	MA0100137	Dec 2028	237
19	Lee Wastewater Treatment Facility	Lee	0.47	MAG590023	Oct 2027	0
20	Spencer Wastewater Treatment Plant	Spencer	0.44	MAG590010	Oct 2027	20
21	North Brookfield Waste Water Treatment Plant	North Brookfield	0.29	MAG580037	Nov 2026	20
22	Cohasset Wastewater Treatment Facility	Cohasset	0.21	MAG580033	Nov 2026	66
23	Stockbridge W W T P	Stockbridge	0.1	MAG580029	Nov 2026	0
24	Marion Wastewater Treatment Facility	Marion	0.09	MA0100030	Nov 2022	17
25	Leicester Water Supply WWTF	Leicester	0.09	MAG580027	Nov 2026	5

Plants planning nutrient removal upgrades

These plants report nutrient removal as a planned process in the EPA Clean Watersheds Needs Survey: the earliest public signal of a project.

Massachusetts plants with nutrient removal recorded as a planned process.
Facility	City	Avg flow (MGD)	NPDES permit	Expires
Greenfield Water Pollution Control Facility	Greenfield	1.44	MAG590014	Oct 2027
Spencer Wastewater Treatment Plant	Spencer	0.44	MAG590010	Oct 2027

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 Massachusetts

Lagoon systems (10)Activated sludge and clarifiers (51)Oxidation ditches (6)Anaerobic digesters and biogas (17)UV disinfection (17)Chlorine disinfection (25)

Nutrient removal in other states

Missouri (23)Virginia (20)Vermont (14)Florida (7)

Nutrient removal in Massachusetts: 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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