Anaerobic digesters and biogas: wastewater treatment plants in California
74 plants · 39% of the state · 513 MGD reported by 44 plants
Klarifi identifies 74 publicly owned wastewater treatment plants with anaerobic digesters and biogas in California, 39% of the 192 plants in the state (513 MGD reported by 44 plants). The largest is Point Loma Wastewater Treatment Plant in San Diego at 140.8 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 California
| # | Facility | City | Avg flow (MGD) | NPDES permit | Expires | Violations (3y) |
|---|---|---|---|---|---|---|
| 1 | Point Loma Wastewater Treatment Plant | San Diego | 140.8 | CA0107409 | Apr 2031 | 1689 |
| 2 | Ccsf- Southeast Water Pollution Control Plant | San Francisco | 72.75 | CA0037664 | Sep 2018 | 10 |
| 3 | Stockton Rwcf | Stockton | 28.94 | CA0079138 | Jul 2030 | 61 |
| 4 | South Bay International WWTP | San Diego | 28.5 | CA0109045 | Jun 2026 | 2645 |
| 5 | Riverside City, Water Quality Control | Riverside | 27.97 | CA0105350 | Oct 2018 | 2 |
| 6 | Encina Water Pollution Control Facility | Carlsbad | 23.63 | CAL107395 | Dec 2030 | 11 |
| 7 | Valencia Wwrp | Valencia | 15.64 | CA0054216 | Jun 2027 | 5 |
| 8 | Aliso Creek Ocean Outfall | Dana Point | 12.64 | CA0107611 | Apr 2027 | 34 |
| 9 | Monterey Regional WWTP | Marina | 12.63 | CA0048551 | Feb 2030 | 5 |
| 10 | Oceanside Ocean Outfall | Oceanside | 10.99 | CA0107433 | Mar 2025 | 5 |
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 California
Anaerobic digesters and biogas in other states
Anaerobic digesters and biogas in California: 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 · Significant industrial user · WWTP · all terms