Anaerobic digesters and biogas: wastewater treatment plants in Washington
21 plants · 17% of the state · 60 MGD reported by 7 plants
Klarifi identifies 21 publicly owned wastewater treatment plants with anaerobic digesters and biogas in Washington, 17% of the 125 plants in the state (60 MGD reported by 7 plants). The largest is Riverside Park Water Reclamation Facility in Spokane at 31.72 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 | Riverside Park Water Reclamation Facility | Spokane | 31.72 | WA0024473 | Aug 2027 | 4 |
| 2 | Chambers Creek WWTP | University Place | 17.07 | WAR000727 | Dec 2029 | 0 |
| 3 | Richland City Wastewater Lab | Richland | 6.31 | WA0020419 | Sep 2021 | 0 |
| 4 | Camas STP | Camas | 2.62 | WA0020249 | Jul 2030 | 19 |
| 5 | Sunnyside STP | Sunnyside | 1.31 | WA0020991 | Jan 2020 | 1 |
| 6 | Toppenish Wastewater Treatment Plant | Toppenish | 0.67 | WA0026123 | Dec 2030 | 29 |
| 7 | Tekoa STP | Tekoa | 0.05 | WA0023141 | May 2019 | 35 |
| 8 | Burlington WWTP | Burlington | — | WA0020150 | Jan 2023 | 0 |
| 9 | Ellensburg WWTP | Ellensburg | — | WA0024341 | Dec 2023 | 0 |
| 10 | King County South WWTP | Renton | — | WAR002511 | Dec 2029 | 3 |
| 11 | Lott Wastewater Treatment Plant | Olympia | — | WAG994545 | Dec 2026 | 0 |
| 12 | Lynden STP | Lynden | — | WA0022578 | Oct 2022 | 6 |
| 13 | Metro West Point | Seattle | — | WAL029181 | Dec 2030 | 275 |
| 14 | Port Angeles WWTP | Port Angeles | — | WA0023973 | Jan 2021 | 0 |
| 15 | Port Orchard WWTP | Port Orchard | — | WAG994523 | Dec 2026 | 4 |
| 16 | Prosser City WWTP | Prosser | — | WAR303447 | Dec 2020 | 9 |
| 17 | Salmon Creek WWTP | Seattle | — | WAG994551 | Dec 2026 | 0 |
| 18 | Salmon Creek WWTP | Vancouver | — | WAR000728 | Dec 2029 | 0 |
| 19 | Walla Walla Water Reclamation Facility | Walla Walla | — | WA0024627 | Jun 2017 | 19 |
| 20 | Wenatchee Wastewater Treatment Plant | Wenatchee | — | WA0023949 | Aug 2015 | 10 |
| 21 | Yakima Regional Wastewater Facility | Yakima | — | WA0024023 | Mar 2029 | 1 |
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 September 11, 2026.