Mason WWTP No 2
Mason, OH · Warren County · Publicly Owned Treatment Works
- Average flow
- 5.56 MGD
- Design flow
- 13 MGD
- NPDES permit
- OH0020494
- Expired
- Permit expires
- May 2026
- Population served
- 22,496
- CWNS 2022
Mason WWTP No 2 is a publicly owned wastewater treatment works in Mason, Warren County, Ohio treating an average of 5.56 million gallons per day against a permitted design capacity of 13 MGD, serving about 22,496 residents. Treatment on site includes clarifiers, uncovered lagoons, carrousels / oxidation ditches. It discharges under NPDES permit OH0020494 (expired), which expires in May 2026, with 1 recorded violation 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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Uncovered lagoons
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Carrousels / oxidation ditches
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Compliance snapshot (last 3 years)
- Total violations
- 1
- Effluent violations
- 1
Based on NPDES Discharge Monitoring Reports. Full violation history, parameters and discharge data available in the Klarifi platform.
Key contacts
Decision-makers at Mason WWTP No 2.
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Nearby wastewater treatment plants in Ohio
Lebanon · 2 mi away
2.46 MGD
Maineville · 4 mi away
5.43 MGD
Loveland · 8 mi away
1.5 MGD
Loveland · 9 mi away
3.35 MGD
Loveland · 9 mi away
0.23 MGD
Goshen · 9 mi away
0.0051 MGD
Loveland · 9 mi away
0.09 MGD
West Chester · 10 mi away
8.34 MGD
Mason WWTP No 2: 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 23, 2025.