The largest lagoon wastewater treatment systems in the US
Ranked by average flow · 2,282 MGD combined
Back River Wastewater Treatment Plant in Baltimore, Maryland tops the list at about 114.1 million gallons per day. Texas (16), Michigan (7), Ohio (6), California (6), Oklahoma (6) have the most plants in the top 100. Every plant links to its profile with permit, technology and compliance data.
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 | Technology | Violations (3y) |
|---|---|---|---|---|---|---|---|---|
| 1 | Back River Wastewater Treatment Plant | Baltimore | MD | 114.1 | MDL021555 | Dec 2030 | Clarifiers, Uncovered lagoons, Biogas silos, Biogas balloons | 32 |
| 2 | Dos Rios Water Recycling Center | San Antonio | TX | 105.32 | TX0077801 | Jun 2025 | Clarifiers, Aerated lagoons, Biogas silos | 48 |
| 3 | City Of Dallas Central WWTP | Dallas | TX | 104 | TX0047830 | Apr 2027 | Clarifiers, Aerated lagoons, Uncovered lagoons, Biogas silos | 10 |
| 4 | 91st Avenue WWTP | Tolleson | AZ | 78.71 | AZ0020524 | Apr 2028 | Clarifiers, Uncovered lagoons, Carrousels / oxidation ditches, Biogas silos | 2 |
| 5 | Wilmington Wastewater Treatment Plant- 12th St & Hay Rd, Wilmington | Wilmington | DE | 78.67 | DEL020320 | Dec 2030 | Clarifiers, Uncovered lagoons | 5 |
| 6 | Middlesex County Utilities Authority | Sayreville | NJ | 77.42 | NJ0020141 | Jun 2020 | Clarifiers, Uncovered lagoons, Biogas silos | 17 |
| 7 | Bergen County Utilities Authority | Little Ferry | NJ | 63.2 | NJ0020028 | Mar 2030 | Clarifiers, Uncovered lagoons, Biogas silos | 176 |
| 8 | West Boise WWTP | Garden City | ID | 62 | ID0023981 | Jun 2027 | Clarifiers, Uncovered lagoons, Biogas silos | 9 |
| 9 | Walnut Creek WWTP | Austin | TX | 56.6 | TX0046981 | Mar 2025 | Clarifiers, Uncovered lagoons | 0 |
| 10 | Msd, Morris Forman Plant | Louisville | KY | 56.18 | KY0022411 | Sep 2004 | Clarifiers, Uncovered lagoons, Biogas balloons | 221 |
| 11 | Hillebrandt WWTP | Beaumont | TX | 47.3 | TX0046990 | Apr 2029 | Clarifiers, Aerated lagoons, Uncovered lagoons | 24 |
| 12 | Neuse River Resource Recovery Facility | Raleigh | NC | 47.06 | NC0029033 | Feb 2025 | Clarifiers, Aerated lagoons, Uncovered lagoons, Biogas silos, Biogas balloons | 1 |
| 13 | Albany County Sewer District - South Plant | Albany | NY | 45.11 | NY0026867 | Feb 2030 | Clarifiers, Uncovered lagoons, Biogas silos | 49 |
| 14 | Akron WRF | Akron | OH | 44.82 | OH0023833 | Aug 2028 | Clarifiers, Uncovered lagoons | 0 |
| 15 | City Of Toledo Division Of Water Reclaimation | Toledo | OH | 39.6 | OH0027740 | Jan 2029 | Clarifiers, Uncovered lagoons, Biogas silos, Biogas balloons | 3 |
| 16 | Moccasin Bend Wastewater Treatment Plant | Chattanooga | TN | 36.67 | TNR053775 | Jun 2030 | Clarifiers, Aerated lagoons, Uncovered lagoons, Biogas silos | 53 |
| 17 | Noman M Cole Jr Pollution Control Plant | Lorton | VA | 34.8 | VAL025364 | Dec 2030 | Clarifiers, Aerated lagoons | 0 |
| 18 | City Of Grand Rapids Wastewater Treatment Plant | Grand Rapids | MI | 33.4 | MI0026069 | Oct 2029 | Clarifiers, Aerated lagoons, Biogas silos, Biogas balloons | 9 |
| 19 | Roberto R Bustamante WWTP | El Paso | TX | 32.92 | TX0101605 | Apr 2030 | Clarifiers, Uncovered lagoons, Biogas silos, Biogas balloons | 35 |
| 20 | Pima County - Ina Road WWTP | Tucson | AZ | 31.89 | AZ0020001 | May 2027 | Clarifiers, Uncovered lagoons, Biogas silos | 3 |
| 21 | Metro Wastewater Treatment Plant | Columbia | SC | 29.87 | SC0020940 | May 2023 | Clarifiers, Uncovered lagoons, Biogas silos | 7 |
| 22 | Little Blue Valley Sewer District | Independence | MO | 29.2 | MOL101087 | Dec 2030 | Clarifiers, Aerated lagoons, Covered lagoons, Carrousels / oxidation ditches, Biogas silos, Biogas balloons | 14 |
| 23 | Stockton Rwcf | Stockton | CA | 29.2 | CA0079138 | Jul 2030 | Clarifiers, Uncovered lagoons, Biogas silos | 57 |
| 24 | Riverside City, Water Quality Control | Riverside | CA | 27.72 | CA0105350 | Oct 2018 | Clarifiers, Aerated lagoons, Uncovered lagoons, Biogas silos, Biogas balloons | 2 |
| 25 | Bergen Point STP & Bergen Ave Dock | W Babylon | NY | 26.7 | NY0104809 | Dec 2019 | Clarifiers, Uncovered lagoons, Biogas silos | 81 |
| 26 | Saniatry District Of Hammond | Hammond | IN | 25.83 | IN0023060 | Apr 2027 | Clarifiers, Uncovered lagoons, Biogas silos | 21 |
| 27 | Southwest WWTP | Springfield | MO | 25.32 | MO0049522 | Jul 2025 | Clarifiers, Aerated lagoons, Uncovered lagoons, Carrousels / oxidation ditches, Biogas silos, Biogas balloons | 0 |
| 28 | Truckee Meadows Water Reclamation Facility | Reno | NV | 24.7 | NV0020150 | May 2017 | Clarifiers, Uncovered lagoons, Biogas silos | 1 |
| 29 | Atlantic County Utilities Authority POTW | Atlantic City | NJ | 24.52 | NJL024473 | Dec 2030 | Clarifiers, Uncovered lagoons, Biogas silos | 0 |
| 30 | Jea Buckman WWTP | Jacksonville | FL | 24.34 | FL0026000 | Dec 2030 | Clarifiers, Uncovered lagoons, Biogas silos, Biogas balloons | 69 |
| 31 | Anthony Ragnone Wastewater Treatment Plant | Montrose | MI | 23.04 | MI0022977 | Oct 2023 | Clarifiers, Uncovered lagoons, Biogas silos | 3 |
| 32 | Waco Metropolitan Area Regional Sewarge System | Waco | TX | 21.83 | TX0026506 | Jul 2030 | Clarifiers, Uncovered lagoons, Biogas silos | 48 |
| 33 | Whites Creek Wastewater Treatment Plant | Nashville | TN | 21.51 | TN0024970 | Oct 2025 | Clarifiers, Aerated lagoons, Biogas balloons | 39 |
| 34 | Colton/san Bernardino Stp, Rix | Colton | CA | 21.06 | CA8000304 | Jul 2018 | Aerated lagoons | 0 |
| 35 | City Of Billings Wastewater Treatment Plant | Billings | MT | 20.31 | MTR000459 | Jan 2028 | Clarifiers, Uncovered lagoons, Biogas silos | 7 |
| 36 | Tmua South | Tulsa | OK | 18.57 | OK0026239 | May 2029 | Aerated lagoons | 21 |
| 37 | Durham Waste Handling | Tigard | OR | 18.4 | ORL028118 | Dec 2030 | Clarifiers, Uncovered lagoons, Biogas silos | 6 |
| 38 | Macon Water Authority (rocky Creek Wrf) | Macon | GA | 18.26 | GAIS01201 | May 2027 | Clarifiers, Aerated lagoons | 40 |
| 39 | Northside Wastewater Treatment Plant | Tulsa | OK | 17.9 | OK0026221 | Feb 2028 | Clarifiers, Aerated lagoons, Uncovered lagoons, Biogas silos | 19 |
| 40 | River Road Wastewater Treatment Plant | Wichita Falls | TX | 16.92 | TX0047686 | Jul 2028 | Clarifiers, Aerated lagoons, Biogas silos | 2 |
| 41 | Boca Raton, City Of - WWTP | Boca Raton | FL | 16.29 | FL0026344 | Sep 2028 | Clarifiers, Aerated lagoons, Biogas silos, Biogas balloons | 8 |
| 42 | Lafayette WWTP | Lafayette | IN | 15.2 | IN0032468 | Jul 2028 | Clarifiers, Uncovered lagoons, Biogas silos | 0 |
| 43 | Medford Rwrf | Central Point | OR | 14.5 | OR0026263 | Jul 2026 | Clarifiers, Uncovered lagoons, Biogas silos | 1 |
| 44 | City Of Wyoming Clean Water Plant | Grandville | MI | 14.38 | MI0024392 | Oct 2030 | Clarifiers, Uncovered lagoons, Biogas silos | 74 |
| 45 | H L Mooney Water Reclamation Facility | Woodbridge | VA | 14.17 | VA0025101 | Oct 2030 | Clarifiers, Aerated lagoons, Biogas silos, Biogas balloons | 0 |
| 46 | Ok City Water Util Trst-Deer Ck | Oklahoma City | OK | 14.07 | OK0027561 | Aug 2029 | Clarifiers, Uncovered lagoons, Biogas balloons | 39 |
| 47 | Denton Creek Regional WWTF | Roanoke | TX | 13.6 | TX0104957 | Apr 2029 | Clarifiers, Uncovered lagoons | 0 |
| 48 | City Of Saginaw Wastewater Treatment Plant | Saginaw | MI | 13.41 | MI0025577 | Oct 2029 | Clarifiers, Uncovered lagoons | 21 |
| 49 | City Of Longview Main WWTP | Longview | TX | 13.3 | TX0022217 | Sep 2026 | Clarifiers, Aerated lagoons, Uncovered lagoons, Biogas silos | 11 |
| 50 | East Chicago Sanitary District | East Chicago | IN | 13.24 | IN0022829 | Jun 2026 | Clarifiers, Aerated lagoons, Carrousels / oxidation ditches | 44 |
| 51 | Wcrsa Mauldin Road Wastewater Treatment Plant | Greenville | SC | 12.8 | SC0041211 | Jun 2008 | Clarifiers, Uncovered lagoons, Biogas silos | 24 |
| 52 | Southwest District WWTF | Jacksonville | FL | 12.59 | FL0026468 | Aug 2029 | Clarifiers, Aerated lagoons, Uncovered lagoons | 4 |
| 53 | Met Council - Empire WWTP | Farmington | MN | 12.05 | MNL045845 | Dec 2030 | Clarifiers, Uncovered lagoons, Biogas silos, Biogas balloons | 0 |
| 54 | Haikey Creek Wastewater Treatment Plant | Broken Arrow | OK | 11.94 | OK0034363 | Apr 2030 | Clarifiers, Uncovered lagoons, Carrousels / oxidation ditches | 3 |
| 55 | Lima WWTP | Lima | OH | 11.44 | OH0026069 | Jun 2028 | Aerated lagoons, Uncovered lagoons, Cooling towers | 35 |
| 56 | Persigo Wastewater Treatment Plant | Grand Junction | CO | 11.4 | CO0040053 | Dec 2022 | Clarifiers, Aerated lagoons, Uncovered lagoons, Biogas silos | 1 |
| 57 | Dallas Salmon WWTP | League City | TX | 11.35 | TX0085618 | Apr 2029 | Clarifiers, Uncovered lagoons | 4 |
| 58 | Lawton, City Of | Lawton | OK | 11 | OK0035246 | Sep 2030 | Clarifiers, Uncovered lagoons, Biogas silos | 182 |
| 59 | Clinton River WRRF | Pontiac | MI | 10.99 | MI0023825 | Oct 2025 | Clarifiers, Uncovered lagoons, Biogas silos, Biogas balloons | 3 |
| 60 | Sod Run Wastewater Treatment Plant | Perryman | MD | 10.81 | MDL056545 | Dec 2030 | Clarifiers, Uncovered lagoons, Biogas silos, Biogas balloons | 0 |
| 61 | Bloomington Normal WRD -West STP | Bloomington | IL | 10.71 | ILL027731 | Dec 2030 | Clarifiers, Aerated lagoons, Uncovered lagoons, Biogas silos, Biogas balloons | 0 |
| 62 | Norman (main) Wwt | Norman | OK | 10.7 | OK0029190 | Oct 2030 | Clarifiers, Uncovered lagoons, Biogas silos | 61 |
| 63 | Grand Island Wastewater Trtmnt | Grand Island | NE | 10.67 | NE0043702 | Dec 2024 | Clarifiers, Aerated lagoons | 11 |
| 64 | Rapid City Water Reclamation Facility | Rapid City | SD | 10.62 | SD0023574 | Jun 2022 | Clarifiers, Uncovered lagoons, Biogas silos, Biogas balloons | 4 |
| 65 | City Of Texas City | Texas City | TX | 10.53 | TX0023949 | Jul 2030 | Clarifiers, Aerated lagoons, Uncovered lagoons | 5 |
| 66 | Jackson WWTP | Jackson | MI | 10.52 | MI0023256 | Oct 2027 | Clarifiers, Uncovered lagoons, Biogas silos | 41 |
| 67 | West Rankin Utility Authority WWTF | Richland | MS | 10.32 | MS0061743 | Feb 2030 | Clarifiers, Uncovered lagoons | 4 |
| 68 | City Of Huntsville | Madison | AL | 10.29 | AL0049531 | Jun 2030 | Clarifiers, Aerated lagoons, Uncovered lagoons, Carrousels / oxidation ditches | 2 |
| 69 | Joco Douglas Smith Mid Basin | Overland Park | KS | 10.2 | KS0119601 | Feb 2027 | Aerated lagoons, Biogas silos, Biogas balloons | 0 |
| 70 | City Of Warren Water Pollution Control | Warren | OH | 10.13 | OH0027987 | Nov 2028 | Clarifiers, Uncovered lagoons | 68 |
| 71 | Pine Bluffs Wastewater Lagoon | Pine Bluffs | WY | 10 | WY0032212 | Apr 2029 | Uncovered lagoons | 273 |
| 72 | A. Manning Lynch Wastewater Treatment Facility | Spartanburg | SC | 9.82 | SCG570017 | Dec 2030 | Clarifiers, Aerated lagoons, Uncovered lagoons, Biogas silos | 2 |
| 73 | City Of Nederland Wastewater Treatment Plant | Nederland | TX | 9.82 | TX0026476 | Jan 2031 | Clarifiers, Uncovered lagoons | 20 |
| 74 | City Of Cookeville Department Of Water Quality Control (wwtp) | Cookeville | TN | 9.62 | TN0024198 | Jun 2027 | Clarifiers, Uncovered lagoons, Carrousels / oxidation ditches | 27 |
| 75 | Huntington WWTP | Huntington | WV | 9.5 | WVL023159 | Dec 2030 | Uncovered lagoons | 72 |
| 76 | South Mission 1 WWTP | Mission | TX | 9.49 | TX0070017 | Apr 2028 | Clarifiers, Aerated lagoons, Uncovered lagoons, Carrousels / oxidation ditches | 0 |
| 77 | Victor Valley Wastewater Reclamation Authority | Victorville | CA | 9.48 | CA0102822 | May 2025 | Clarifiers, Aerated lagoons, Uncovered lagoons, Biogas silos | 7 |
| 78 | Joco Mill Creek Regional Wtf | Shawnee | KS | 9.47 | KS0088269 | Jan 2030 | Clarifiers, Aerated lagoons, Uncovered lagoons | 0 |
| 79 | Conroe Southwest Regional WWTP | Conroe | TX | 9.4 | TX0022268 | Oct 2029 | Clarifiers, Uncovered lagoons | 9 |
| 80 | Greeley WWTP | Greeley | CO | 9.4 | COL040258 | Dec 2030 | Clarifiers, Aerated lagoons, Uncovered lagoons, Biogas silos, Biogas balloons, Cooling towers | 13 |
| 81 | Appleton City WWTF | Appleton | WI | 9.25 | WI0023221 | Mar 2022 | Clarifiers, Uncovered lagoons, Biogas silos, Biogas balloons | 7 |
| 82 | Sumter Pocataligo River WWTP | Sumter | SC | 9.15 | SC0027707 | Mar 2026 | Clarifiers, Aerated lagoons, Uncovered lagoons, Biogas silos | 49 |
| 83 | East Lansing Wastewater Treatment Plant | East Lansing | MI | 9.13 | MI0022853 | Oct 2027 | Clarifiers, Aerated lagoons, Biogas silos, Biogas balloons | 1 |
| 84 | Fox River Water Pollution Control Center | Brookfield | WI | 8.95 | WI0023469 | Dec 2023 | Clarifiers, Uncovered lagoons, Biogas silos, Biogas balloons | 10 |
| 85 | Massillon WWTP | Massillon | OH | 8.87 | OH0020516 | May 2031 | Clarifiers, Aerated lagoons, Biogas silos | 0 |
| 86 | Grand Forks City Of | Grand Forks | ND | 8.82 | ND0022888 | Dec 2028 | Uncovered lagoons | 7 |
| 87 | Bob Derrington Water Reclamation Plant | Odessa | TX | 8.79 | TX0072800 | Jul 2025 | Clarifiers, Uncovered lagoons, Carrousels / oxidation ditches | 92 |
| 88 | Dillman Waste Water Treatment Plant | Bloomington | IN | 8.64 | IN0035718 | Aug 2029 | Uncovered lagoons | 7 |
| 89 | Lower Berkeley Wastewater Treatment Plant | Goose Creek | SC | 8.6 | SC0046060 | Apr 2024 | Clarifiers, Uncovered lagoons, Carrousels / oxidation ditches | 1 |
| 90 | Annapolis WRF | Annapolis | MD | 8.48 | MD0021814 | Jan 2030 | Clarifiers, Uncovered lagoons, Biogas silos | 6 |
| 91 | Cibolo Creek Municipal Authority WWTP | Schertz | TX | 8.42 | TXR05FI55 | Aug 2026 | Clarifiers, Uncovered lagoons, Biogas silos | 1 |
| 92 | Upper Mill Creek Water Reclamation Facil | West Chester | OH | 8.34 | OH0072087 | Dec 2023 | Clarifiers, Aerated lagoons, Carrousels / oxidation ditches, Biogas balloons | 33 |
| 93 | Fulton County - Johns Creek Environmental Campus | Alpharetta | GA | 8.2 | GA0038831 | Dec 2029 | Aerated lagoons | 2 |
| 94 | Hill Canyon WWTP | Camarillo | CA | 8.09 | CA0056294 | Jul 2031 | Clarifiers, Uncovered lagoons, Biogas silos | 3 |
| 95 | Bismarck City Of (potw) | Bismarck | ND | 7.66 | ND0023434 | Jun 2028 | Uncovered lagoons, Biogas balloons | 0 |
| 96 | Corona WWTP 1 | Corona | CA | 7.64 | CA8000383 | Jun 2025 | Clarifiers, Aerated lagoons, Carrousels / oxidation ditches, Biogas silos | 9 |
| 97 | Pine Bluff WW Utility-Boyd Pt | Pine Bluff | AR | 7.62 | ARL033316 | Dec 2030 | Aerated lagoons, Uncovered lagoons | 16 |
| 98 | Springettsbury Wastewater Treatment Plant | York | PA | 7.61 | PAL026808 | Dec 2030 | Clarifiers, Aerated lagoons, Biogas silos | 4 |
| 99 | MSD Lower Meramec WWTP | St. Louis | MO | 7.6 | MO0127949 | Aug 2031 | Clarifiers, Aerated lagoons, Uncovered lagoons, Biogas silos, Biogas balloons | 0 |
| 100 | Spring Creek STP | Springfield | IL | 7.59 | ILL021989 | Dec 2030 | Clarifiers, Uncovered lagoons, Biogas silos | 28 |
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.