Activated sludge and clarifiers: wastewater treatment plants in Oregon
38 plants · 30% of the state · 99 MGD reported by 36 plants
Klarifi identifies 38 publicly owned wastewater treatment plants with activated sludge and clarifiers in Oregon, 30% of the 125 plants in the state (99 MGD reported by 36 plants). The largest is Willow Lake WWTP in Salem at 24.62 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 Oregon
| # | Facility | City | Avg flow (MGD) | NPDES permit | Expires | Violations (3y) |
|---|---|---|---|---|---|---|
| 1 | Willow Lake WWTP | Salem | 24.62 | ORL026409 | Dec 2030 | 2 |
| 2 | Durham Waste Handling | Tigard | 18.4 | ORL028118 | Dec 2030 | 6 |
| 3 | Medford Rwrf | Central Point | 14.5 | OR0026263 | Jul 2026 | 1 |
| 4 | Gresham WWTP | Portland | 8.99 | OR0026131 | Aug 2026 | 0 |
| 5 | Albany-Millersburg WRF | Albany | 4.59 | OR0028801 | Jan 2031 | 2 |
| 6 | Grants Pass STP | Grants Pass | 4.48 | OR0028843 | Sep 2014 | 16 |
| 7 | Tryon Creek WWTP | Lake Oswego | 3.51 | OR0026891 | Apr 2029 | 2 |
| 8 | Mcminnville WWTP | Mcminnville | 2.73 | OR0034002 | Dec 2008 | 2 |
| 9 | Oak Lodge Water Reclamation Facility | Milwaukie | 1.74 | OR0026140 | Mar 2027 | 3 |
| 10 | Ashland WWTP | Ashland | 1.71 | OR0026255 | Jan 2027 | 15 |
| 11 | Lebanon STP | Lebanon | 1.63 | OR0020818 | Oct 2030 | 54 |
| 12 | Hermiston WWTP | Hermiston | 1.56 | OR0020761 | Jan 2028 | 0 |
| 13 | Dallas WWTP | Rickreall | 1.42 | OR0020737 | Oct 2030 | 13 |
| 14 | Seaside WWTP | Seaside | 1.2 | OR0020401 | Jul 2029 | 27 |
| 15 | Hood River STP | Hood River | 1.13 | OR0020788 | May 2031 | 46 |
| 16 | Canby WWTP | Canby | 0.99 | OR0020214 | Nov 2027 | 0 |
| 17 | Umatilla STP | Umatilla | 0.72 | OR0022306 | Dec 2027 | 0 |
| 18 | Sweet Home STP | Sweet Home | 0.7 | OR0020346 | Mar 2010 | 27 |
| 19 | Scappoose STP | Scappoose | 0.67 | OR0022420 | Oct 2014 | 1 |
| 20 | Florence STP | Florence | 0.64 | OR0020745 | Apr 2019 | 0 |
| 21 | Estacada STP | Estacada | 0.44 | OR0020575 | Sep 2015 | 41 |
| 22 | Odell STP | Hood River | 0.33 | OR0022471 | Aug 2029 | 7 |
| 23 | Toledo STP | Toledo | 0.32 | OR0020869 | Nov 2010 | 31 |
| 24 | Shady Cove STP | Shady Cove | 0.29 | OR0030660 | Mar 2016 | 1 |
| 25 | Bandon STP | Bandon | 0.26 | OR0020206 | Aug 2029 | 39 |
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 Oregon
Activated sludge and clarifiers in other states
Activated sludge and clarifiers in Oregon: 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.