Upper Blackstone Wastewater Treatment Plant
Millbury, MA · Worcester County · Publicly Owned Treatment Works
- Average flow
- 24.1 MGD
- Design flow
- —
- NPDES permit
- MAR053209
- Expired
- Permit expires
- February 2026
- Population served
- 257,969
- CWNS 2022
Upper Blackstone Wastewater Treatment Plant is a publicly owned wastewater treatment works in Millbury, Worcester County, Massachusetts treating an average of 24.1 million gallons per day, serving about 257,969 residents. Treatment on site includes clarifiers, biological n removal, biological p removal, biosolids incineration, biosolids mechanical dewatering and other unit processes. It discharges under NPDES permit MAR053209 (expired), which expires in February 2026, with 15 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 processBiological P removal
unit processBiosolids Incineration
unit processBiosolids Mechanical Dewatering
unit processBiosolids Thickening
unit processDechlorination
unit processDisinfection, chlorine/ chloramine
unit processPrimary Clarification or Sedimentation
unit processScreening
unit processSuspended Growth, Aerobic
unit processSuspended Growth, Anaerobic
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Compliance snapshot (last 3 years)
- Total violations
- 15
- Effluent violations
- 15
Based on NPDES Discharge Monitoring Reports. Full violation history, parameters and discharge data available in the Klarifi platform.
Key contacts
4 verified contacts for Upper Blackstone Wastewater Treatment Plant, with validated emails and direct phone numbers.
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Names, validated emails and direct phone numbers for decision-makers at Upper Blackstone Wastewater Treatment Plant, plus the full compliance history and discharge data.
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Leicester · 7 mi away
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Westborough · 9 mi away
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East Douglas · 10 mi away
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Spencer · 12 mi away
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Charlton · 12 mi away
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Marlborough · 13 mi away
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North Brookfield · 15 mi away
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Upper Blackstone Wastewater Treatment Plant: 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 June 30, 2025.