Lagoon systems: wastewater treatment plants in Louisiana
78 plants · 28% of the state · 74 MGD reported by 69 plants
Klarifi identifies 78 publicly owned wastewater treatment plants with lagoon systems in Louisiana, 28% of the 277 plants in the state (74 MGD reported by 69 plants). The largest is Wastewater Treatment Plant, Hudson Site in Alexandria at 8.46 MGD.
Lagoon systems treat wastewater in large earthen ponds over weeks of retention time, with or without mechanical aeration. They serve thousands of small towns because they are cheap to run, but they struggle with ammonia and nutrient limits, fill with sludge over decades and are the plants most often converted or upgraded when a permit is renewed.
The largest lagoons in Louisiana
| # | Facility | City | Avg flow (MGD) | NPDES permit | Expires | Violations (3y) |
|---|---|---|---|---|---|---|
| 1 | Wastewater Treatment Plant, Hudson Site | Alexandria | 8.46 | LA0041009 | Dec 2030 | 2 |
| 2 | Monroe, City Of (wpc Cntr) | Monroe | 7.62 | LAL038741 | Dec 2030 | 78 |
| 3 | Hammond North STP | Hammond | 7.21 | LA0032328 | Aug 2028 | 37 |
| 4 | Shreveport North Regional WWTP | Shreveport | 3.78 | LAL042188 | Dec 2030 | 42 |
| 5 | Wards 5 & 8 Joint Sewerage Commision | Patterson | 3.17 | LA0068381 | Sep 2030 | 99 |
| 6 | Denham Springs Wastewater Treatment Facility | Denham Springs | 2.67 | LAL045730 | Dec 2030 | 193 |
| 7 | Thibodaux, City Of- Wastewater Treatment Facility | Thibodaux | 2.43 | LA0032948 | Jul 2029 | 77 |
| 8 | City Of Gonzales Water System | Gonzales | 1.96 | LAL109576 | Dec 2030 | 22 |
| 9 | Crowley WWTP | Crowley | 1.89 | LA0041254 | Oct 2030 | 43 |
| 10 | Luling Oxidation Pond | Luling | 1.66 | LA0032131 | Jun 2028 | 9 |
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 Louisiana
Lagoon systems in other states
Lagoon systems in Louisiana: 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 · Biosolids · Equalization tank · Centrate · all terms