Activated sludge and clarifiers: wastewater treatment plants in Ohio
303 plants · 36% of the state · 768 MGD reported by 299 plants
Klarifi identifies 303 publicly owned wastewater treatment plants with activated sludge and clarifiers in Ohio, 36% of the 837 plants in the state (768 MGD reported by 299 plants). The largest is Southerly Wastewater Treatment Plant in Lockbourne at 82.1 MGD.
Activated sludge is the standard mechanical process for cities: aeration basins where bacteria consume organic matter, followed by clarifiers that settle the biomass out. These plants are identified by their circular or rectangular clarifiers and by the suspended-growth process code, and they are the main market for blowers, diffusers, clarifier mechanisms and instrumentation.
The largest activated sludge plants in Ohio
| # | Facility | City | Avg flow (MGD) | NPDES permit | Expires | Violations (3y) |
|---|---|---|---|---|---|---|
| 1 | Southerly Wastewater Treatment Plant | Lockbourne | 82.1 | OHL024741 | Dec 2030 | 7 |
| 2 | Southerly Wastewater Treatment Center | Cleveland | 78.11 | OHL024651 | Dec 2030 | 3 |
| 3 | Akron WRF | Akron | 44.82 | OH0023833 | Aug 2028 | 0 |
| 4 | City Of Toledo Division Of Water Reclaimation | Toledo | 39.6 | OH0027740 | Jan 2029 | 3 |
| 5 | City Of Dayton Water Reclamation Facility (0857100983) | Dayton | 38.22 | OH0024881 | Apr 2027 | 17 |
| 6 | Metropolitan Sewer Dis Little Miami WWTP | Cincinnati | 21.87 | OH0025453 | Jun 2030 | 8 |
| 7 | City Of Springfield Wastewater Treatment | Springfield | 12.27 | OH0027481 | Feb 2030 | 39 |
| 8 | Middletown Wastewater Treatment Plant | Middletown | 11.69 | OH0026522 | Dec 2026 | 82 |
| 9 | Maumee River Wastewater Treatment Plant | Waterville | 11.65 | OH0034223 | Dec 2027 | 15 |
| 10 | Lakewood WWTP | Lakewood | 11.52 | OH0026018 | Jul 2026 | 5 |
| 11 | City Of Warren Water Pollution Control | Warren | 10.13 | OH0027987 | Nov 2028 | 68 |
| 12 | Gary L Kron Water Reclamation Facility | Mentor | 9.35 | OH0043559 | Mar 2027 | 29 |
| 13 | Massillon WWTP | Massillon | 8.87 | OH0020516 | May 2031 | 0 |
| 14 | Upper Mill Creek Water Reclamation Facil | West Chester | 8.34 | OH0072087 | Dec 2023 | 33 |
| 15 | Muddy Creek WWTP | Cincinnati | 7.73 | OH0025470 | Mar 2030 | 18 |
| 16 | Black River Wastewater Treatment Plant | Lorain | 7.69 | OH0026093 | Nov 2027 | 6 |
| 17 | Western Regional WRF | West Carrollton | 7.67 | OH0026638 | Oct 2026 | 2 |
| 18 | Sandusky WPC | Sandusky | 7.47 | OH0027332 | Apr 2031 | 0 |
| 19 | Beavercreek WRRF | Dayton | 7.3 | OH0025381 | Nov 2030 | 47 |
| 20 | Findlay WPCF | Findlay | 7.22 | OH0025135 | Oct 2029 | 1 |
| 21 | North Regional Wastewater Treatment Plan (0857143037) | Dayton | 7.07 | OH0049646 | Feb 2027 | 47 |
| 22 | Mansfield Wastewater Treatment Plant | Mansfield | 6.67 | OH0026328 | Mar 2030 | 428 |
| 23 | Newark WWTP | Newark | 6.66 | OH0026671 | Jun 2031 | 594 |
| 24 | City Of Zanesville Wastewater Treatment Plant | Zanesville | 5.91 | OH0028240 | Mar 2028 | 12 |
| 25 | Medina County - Liverpool WWTP (sd #500) | Valley City | 5.85 | OH0043567 | Nov 2030 | 6 |
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 Ohio
Activated sludge and clarifiers in other states
Activated sludge and clarifiers in Ohio: 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.