Nutrient removal: wastewater treatment plants in Massachusetts
28 plants · 43% of the state · 93 MGD combined
Klarifi identifies 28 publicly owned wastewater treatment plants with nutrient removal in Massachusetts, 43% of the 65 plants in the state (93 MGD combined). The largest is Upper Blackstone Wastewater Treatment Plant in Millbury at 30.02 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.
The largest plants with nutrient removal in Massachusetts
| # | Facility | City | Avg flow (MGD) | NPDES permit | Expires | Violations (3y) |
|---|---|---|---|---|---|---|
| 1 | Upper Blackstone Wastewater Treatment Plant | Millbury | 30.02 | MAR053209 | Feb 2026 | 19 |
| 2 | Brockton Advanced Water Reclamation Fac | Brockton | 14.52 | MAL101010 | Dec 2030 | 10 |
| 3 | Pittsfield Wastewater Treatment Facility | Pittsfield | 9.85 | MA0101681 | Oct 2026 | 85 |
| 4 | Holyoke Water Pollution Control Facility | Holyoke | 6.07 | MAL101630 | Dec 2030 | 4 |
| 5 | Westborough Wastewater Treatment Plant | Westborough | 4.86 | MA0100412 | Apr 2027 | 2 |
| 6 | Northampton Wastewater Treatment Plant | Northampton | 4.21 | MA0101818 | Nov 2028 | 41 |
| 7 | Amherst Wastewater Treatment Plant | Hadley | 3.36 | MA0100218 | Jan 2029 | 44 |
| 8 | Billerica Wastewater Treatment Facility | Billerica | 3.3 | MA0101711 | Feb 2029 | 51 |
| 9 | Hoosic Wastwater Treament Plant | Williamstown | 3.26 | MA0100510 | Dec 2028 | 2 |
| 10 | Westfield Wastewater Treatment Plant | Westfield | 2.95 | MA0101800 | Nov 2028 | 0 |
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.
| Facility | City | Avg flow (MGD) | NPDES permit | Expires |
|---|---|---|---|---|
| Greenfield Water Pollution Control Facility | Greenfield | 2.2 | MAG590014 | Oct 2027 |
| Spencer Wastewater Treatment Plant | Spencer | 0.66 | 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.
Other technologies in Massachusetts
Nutrient removal in other states
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 October 26, 2026.
Wastewater terms: Biological nutrient removal · Tertiary treatment · Activated sludge · Sludge dewatering · Significant industrial user · all terms