Anaerobic digesters and biogas: wastewater treatment plants in Washington
23 plants · 15% of the state · 264 MGD reported by 20 plants
Klarifi identifies 23 publicly owned wastewater treatment plants with anaerobic digesters and biogas in Washington, 15% of the 150 plants in the state (264 MGD reported by 20 plants). The largest is Metro West Point in Seattle at 106.93 MGD.
Anaerobic digesters stabilise sludge in sealed heated tanks and produce biogas, visible from the air as digester silos and gas holders. Plants with digesters are typically above 5 MGD and are the buyers of mixing, heating, gas handling, cogeneration and dewatering equipment.
The largest plants with anaerobic digesters in Washington
| # | Facility | City | Avg flow (MGD) | NPDES permit | Expires | Violations (3y) |
|---|---|---|---|---|---|---|
| 1 | Metro West Point | Seattle | 106.93 | WAL029181 | Dec 2030 | 275 |
| 2 | King County South WWTP | Renton | 74.4 | WAR002511 | Dec 2029 | 3 |
| 3 | Chambers Creek WWTP | University Place | 22.49 | WAR000727 | Dec 2029 | 0 |
| 4 | Lott Wastewater Treatment Plant | Olympia | 12.08 | WAG994545 | Dec 2026 | 0 |
| 5 | Yakima Regional Wastewater Facility | Yakima | 8.67 | WA0024023 | Mar 2029 | 2 |
| 6 | Richland City Wastewater Lab | Richland | 5.91 | WA0020419 | Sep 2021 | 0 |
| 7 | Puyallup WWTP | Puyallup | 5.2 | WAR313277 | Dec 2030 | 0 |
| 8 | Lakota WWTP | Federal Way | 4.96 | WA0022624 | Sep 2023 | 4 |
| 9 | Miller Creek WWTP And Compost Facility | Seattle | 3.6 | WA0022764 | Sep 2023 | 0 |
| 10 | Ellensburg WWTP | Ellensburg | 3.59 | WA0024341 | Dec 2023 | 0 |
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 Washington
Anaerobic digesters and biogas in other states
Anaerobic digesters and biogas in Washington: 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 October 26, 2026.
Wastewater terms: Anaerobic digester · Biosolids · Sludge dewatering · Centrate · Equalization tank · Ozonation · all terms