The largest lagoon wastewater treatment systems in the US
Ranked by average flow · 1,575 MGD combined
Metropolitan Water Reclamation in Chicago, Illinois tops the list at about 281.73 million gallons per day. Texas (5), Arizona (2), Tennessee (2), Michigan (2), Missouri (2) have the most plants in the top 25. Every plant links to its profile with permit and compliance data. Treatment technology is shown with a free Klarifi account.
Lagoon systems treat wastewater in large earthen ponds and are usually associated with small towns, but the largest ones treat tens of millions of gallons a day for whole regions. Big lagoon systems face the same ammonia, nutrient and sludge-accumulation pressures as small ones, at a scale that makes aeration retrofits, dredging and conversions to mechanical treatment multi-million-dollar projects.
| # | Facility | City | State | Avg flow (MGD) | NPDES permit | Expires | Violations (3y) |
|---|---|---|---|---|---|---|---|
| 1 | Metropolitan Water Reclamation | Chicago | IL | 281.73 | ILL028061 | Dec 2030 | 10 |
| 2 | Dos Rios Water Recycling Center | San Antonio | TX | 124.77 | TX0077801 | Jun 2025 | 44 |
| 3 | City Of Dallas Central WWTP | Dallas | TX | 118.1 | TX0047830 | Apr 2027 | 11 |
| 4 | Back River Wastewater Treatment Plant | Baltimore | MD | 107.68 | MDL021555 | Dec 2030 | 32 |
| 5 | Middlesex County Utilities Authority | Sayreville | NJ | 87.51 | NJ0020141 | Jun 2020 | 21 |
| 6 | 91st Avenue WWTP | Tolleson | AZ | 83.69 | AZ0020524 | Apr 2028 | 2 |
| 7 | Walnut Creek WWTP | Austin | TX | 69.41 | TX0046981 | Mar 2025 | 0 |
| 8 | Akron WRF | Akron | OH | 59.62 | OH0023833 | Aug 2028 | 0 |
| 9 | West Boise WWTP | Garden City | ID | 50.91 | ID0023981 | Jun 2027 | 10 |
| 10 | Moccasin Bend Wastewater Treatment Plant | Chattanooga | TN | 50.56 | TNR053775 | Jun 2030 | 52 |
| 11 | Neuse River Resource Recovery Facility | Raleigh | NC | 47.05 | NC0029033 | Feb 2025 | 1 |
| 12 | Albany County Sewer District - South Plant | Albany | NY | 43.24 | NY0026867 | Feb 2030 | 49 |
| 13 | City Of Grand Rapids Wastewater Treatment Plant | Grand Rapids | MI | 42.18 | MI0026069 | Oct 2029 | 9 |
| 14 | Water Pollution Control Facility | Cedar Rapids | IA | 39.59 | IA0042641 | Aug 2030 | 15 |
| 15 | Little Blue Valley Sewer District | Independence | MO | 39.13 | MOL101087 | Dec 2030 | 14 |
| 16 | Southern Regional WWTP | Boynton Beach | FL | 35 | FLL041424 | Dec 2030 | — |
| 17 | City Of Saginaw Wastewater Treatment Plant | Saginaw | MI | 34.99 | MI0025577 | Oct 2029 | 21 |
| 18 | Noman M Cole Jr Pollution Control Plant | Lorton | VA | 34.89 | VAL025364 | Dec 2030 | 0 |
| 19 | Saniatry District Of Hammond | Hammond | IN | 34.49 | IN0023060 | Apr 2027 | 21 |
| 20 | Hillebrandt WWTP | Beaumont | TX | 34.23 | TX0046990 | Apr 2029 | 22 |
| 21 | Roberto R Bustamante WWTP | El Paso | TX | 33.07 | TX0101605 | Apr 2030 | 35 |
| 22 | Whites Creek Wastewater Treatment Plant | Nashville | TN | 32.64 | TN0024970 | Oct 2025 | 40 |
| 23 | Southwest WWTP | Springfield | MO | 30.9 | MO0049522 | Jul 2025 | 0 |
| 24 | Truckee Meadows Water Reclamation Facility | Reno | NV | 29.93 | NV0020150 | May 2017 | 3 |
| 25 | Pima County - Ina Road WWTP | Tucson | AZ | 29.75 | AZ0020001 | May 2027 | 3 |
Treatment technology for each plant is shown with a free Klarifi account. Create one →
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 · FOG · Equalization tank · all terms