The 50 largest wastewater treatment plants in California
Ranked by average flow · 1,122 MGD combined · 95% of the state's reported flow
Hyperion Treatment Plant in Playa Del Rey is the largest publicly owned wastewater treatment plant in California by reported average flow, treating about 222.56 million gallons per day. The 50 plants below treat 1,122 MGD between them, 95% of the flow reported by all 192 plants in the state, and serve about 14,722,559 people. Every plant links to its profile with permit and compliance data. Treatment technology is shown with a free Klarifi account.
| # | Facility | City | Avg flow (MGD) | Population | NPDES permit | Expires | Violations (3y) |
|---|---|---|---|---|---|---|---|
| 1 | Hyperion Treatment Plant | Playa Del Rey | 222.56 | 2,800,773 | CA0109991 | Apr 2028 | 42 |
| 2 | Joint Water Pollution Control Plant | Carson | 154.69 | 3,353,576 | CA0053813 | Jun 2028 | 19 |
| 3 | Point Loma Wastewater Treatment Plant | San Diego | 140.8 | 2,222,389 | CA0107409 | Apr 2031 | 1689 |
| 4 | Orange County Sanitation District Plant 1 | Fountain Valley | 99.43 | — | CA0110604 | Jul 2026 | 0 |
| 5 | Ccsf- Southeast Water Pollution Control Plant | San Francisco | 72.75 | 585,360 | CA0037664 | Sep 2018 | 10 |
| 6 | Stockton Rwcf | Stockton | 28.94 | 335,503 | CA0079138 | Jul 2030 | 61 |
| 7 | South Bay International WWTP | San Diego | 28.5 | 146,085 | CA0109045 | Jun 2026 | 2645 |
| 8 | Riverside City, Water Quality Control | Riverside | 27.97 | 366,930 | CA0105350 | Oct 2018 | 2 |
| 9 | Encina Water Pollution Control Facility | Carlsbad | 23.63 | 94,500 | CAL107395 | Dec 2030 | 11 |
| 10 | Colton/san Bernardino Stp, Rix | Colton | 20.79 | 403,461 | CA8000304 | Jul 2018 | 0 |
| 11 | La City , Pub Works Dept | Van Nuys | 19.79 | 919,987 | CA0056227 | Jan 2028 | 43 |
| 12 | Regionwide Water Recycling System - Temescal Creek Discharge | Lake Elsinore | 19.76 | 175,686 | CA8000188 | Sep 2020 | 34 |
| 13 | Combined Wastewater Treatment Plant | Sacramento | 16.24 | — | CA0079111 | Sep 2025 | 4 |
| 14 | Valencia Wwrp | Valencia | 15.64 | 168,637 | CA0054216 | Jun 2027 | 5 |
| 15 | Aliso Creek Ocean Outfall | Dana Point | 12.64 | 45,723 | CA0107611 | Apr 2027 | 34 |
| 16 | Monterey Regional WWTP | Marina | 12.63 | 409,354 | CA0048551 | Feb 2030 | 5 |
| 17 | Oceanside Ocean Outfall | Oceanside | 10.99 | 38,102 | CA0107433 | Mar 2025 | 5 |
| 18 | Chino | Chino | 10.94 | 125,940 | CA8000409 | Jul 2027 | 519 |
| 19 | Whittier Narrows Water Reclamation Plant | South El Monte | 10.72 | 297,390 | CA0053716 | Jul 2026 | 14 |
| 20 | Escondido City Of | Escondido | 10.14 | 180,000 | CA0107981 | May 2023 | 2 |
| 21 | City Of Tracy Waste Water Treatment Plant | Tracy | 9.33 | 79,920 | CAL079154 | Dec 2030 | 11 |
| 22 | Forest Shade Sewage Lift Station | Crestline | 9.22 | 90,953 | CA0077691 | Jul 2029 | 18 |
| 23 | Groundwater Reliability Improvement Project - Advanced Water Treatment Facility | Pico Rivera | 8.87 | — | CA0064645 | Jan 2029 | 579 |
| 24 | Western Riverside Co Reg WWTP | Corona | 8.49 | 113,419 | CA8000316 | Jul 2020 | 46 |
| 25 | Victor Valley Wastewater Reclamation Authority | Victorville | 8.44 | 230,482 | CA0102822 | May 2025 | 7 |
| 26 | Corona WWTP 1 | Corona | 7.32 | 104,926 | CA8000383 | Jun 2025 | 9 |
| 27 | Simi Vly Cnty Sanitation | Simi Valley | 7.12 | 114,190 | CA0055221 | Jul 2031 | 36 |
| 28 | Long Beach Water Reclamation Plant | Long Beach | 6.98 | 189,973 | CA0054119 | Mar 2027 | 5 |
| 29 | Manteca Wwqcf | Manteca | 6.91 | 67,537 | CA0081558 | Jul 2031 | 7 |
| 30 | Clear Creek WWTP | Anderson | 6.72 | 65,424 | CA0079731 | Jul 2027 | 16 |
| 31 | Lompoc Wastewater Plant | Lompoc | 6.37 | 53,937 | CA0048127 | Apr 2027 | 11 |
| 32 | San Luis Obispo WWTP | San Luis Obispo | 5.6 | 40,960 | CAL049224 | Dec 2030 | 23 |
| 33 | Watsonville WWTF | Watsonville | 5.28 | 58,713 | CA0048216 | Jul 2019 | 8 |
| 34 | Yuba City Wastewater Treatment Facility | Yuba City | 5.16 | 47,700 | CA0079260 | Mar 2024 | 20 |
| 35 | Ventura Water Reclamation Facility | Ventura | 4.94 | 102,082 | CAC458580 | Mar 2029 | 58 |
| 36 | Water Reclamation Plant No. 4 | Thermal | 4.75 | — | CA0104973 | Apr 2028 | 11 |
| 37 | Goleta Sd WWTP | Goleta | 4.28 | 74,129 | CAL048160 | Dec 2030 | 10 |
| 38 | Redding Stillwater Wastewater Treatment Plant | Anderson | 4.24 | 21,375 | CA0082589 | May 2028 | 6 |
| 39 | Camarillo Sanitary Dist Water Reclamation Plant | Camarillo | 3.96 | 62,737 | CA0053597 | Dec 2024 | 88 |
| 40 | Saugus Wwrp | Saugus | 3.87 | 49,393 | CA0054313 | Jun 2027 | 9 |
| 41 | Woodland WPCF | Woodland | 3.86 | 53,100 | CA0077950 | Mar 2030 | 2 |
| 42 | Davis Water Pollution Control Plant | Davis | 3.8 | 62,764 | CA0079049 | Jul 2030 | 41 |
| 43 | Henry N. Wochholz Wastewater Treatment Facility | Yucaipa | 3.8 | 58,500 | CA0105619 | Oct 2020 | 9 |
| 44 | Linda County WWTP | Marysville | 3.74 | 16,927 | CA0079651 | Jan 2028 | 22 |
| 45 | Merced WWTF | Merced | 3.61 | 83,700 | CA0079219 | May 2025 | 5 |
| 46 | El Centro WWTP | El Centro | 3.52 | 39,493 | CA0104426 | Mar 2024 | 15 |
| 47 | Beaumont WWTF | Beaumont | 3.44 | 35,798 | CA0105376 | Oct 2027 | 12 |
| 48 | Sewerage Commission - Oroville Region | Oroville | 3.13 | 48,631 | CA0079235 | Sep 2026 | 0 |
| 49 | Brentwood Wastewater Treatment Plant | Brentwood | 2.88 | 46,800 | CA0082660 | May 2029 | 17 |
| 50 | Ironhouse Sd WWTP | Oakley | 2.81 | 39,600 | CA0085260 | Jul 2029 | 9 |
Treatment technology for each plant is shown with a free Klarifi account. Create one →
Largest plants 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: WWTP · POTW · MGD · NPDES permit · Biosolids · Filter press · all terms
Cite this page
Journalists, researchers and educators are welcome to quote these figures. Please credit Klarifi as the source and link to this page.
Klarifi. “Largest wastewater treatment plants in California (2026).” Updated October 26, 2026. https://klarifi.io/facilities/california/largestNeed a custom cut of the data for a state, a county or a list of plants? Email info@klarifi.io.