Westerly Wastewater Treatment Facility
Marlborough, MA · Middlesex County · Publicly Owned Treatment Works
- Average flow
- 1.16 MGD
- Design flow
- 2.89 MGD
- NPDES permit
- MA0100480
- Effective
- Permit expires
- December 2026
- Population served
- 40,085
- CWNS 2022
Westerly Wastewater Treatment Facility is a publicly owned wastewater treatment works in Marlborough, Middlesex County, Massachusetts treating an average of 1.16 million gallons per day against a permitted design capacity of 2.89 MGD, serving about 40,085 residents. Treatment on site includes clarifiers, biological n removal, biosolids mechanical dewatering, biosolids thickening, chemical addition, ferric chloride and other unit processes. It discharges under NPDES permit MA0100480 (effective), which expires in December 2026, with 26 recorded violations in the last three years.
Treatment technology
Treatment structures identified at this facility. Exact unit counts are available in Klarifi.
Clarifiers
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Biological N removal
unit processBiosolids Mechanical Dewatering
unit processBiosolids Thickening
unit processChemical Addition, Ferric Chloride
unit processChemical P Removal
unit processDisinfection, UV
unit processPrimary Clarification or Sedimentation
unit processScreening
unit processSuspended Growth, Aerobic
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Compliance snapshot (last 3 years)
- Total violations
- 26
- Effluent violations
- 19
Based on NPDES Discharge Monitoring Reports. Full violation history, parameters and discharge data available in the Klarifi platform.
Key contacts
17 verified contacts for Westerly Wastewater Treatment Facility, with validated emails and direct phone numbers.
Unlock 17 verified contacts (14 more than shown)
Names, validated emails and direct phone numbers for decision-makers at Westerly Wastewater Treatment Facility, plus the full compliance history and discharge data.
Nearby wastewater treatment plants in Massachusetts
Westborough · 4 mi away
4.17 MGD
Hudson · 6 mi away
0.78 MGD
Marlborough · 6 mi away
2.04 MGD
Millbury · 13 mi away
24.1 MGD
Wayland · 13 mi away
0.03 MGD
Concord · 17 mi away
0.68 MGD
Leicester · 17 mi away
0.09 MGD
North Oxford · 18 mi away
0.17 MGD
Westerly Wastewater Treatment Facility: frequently asked 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; facility record last updated May 19, 2025.