What is the largest wastewater treatment plant in Louisiana?

South Wastewater Treatment Plant in Baton Rouge, treating an average of 33 MGD under NPDES permit LA0036412. Jefferson Parish Department Of Sewerage- East Bank WWTP in Elmwood is second at 20.66 MGD.

How much wastewater do Louisiana’s largest plants treat?

The 50 largest plants treat 172 MGD combined, 84% of the flow reported by all 259 publicly owned plants in Louisiana.

How is plant size measured?

By reported average daily flow in million gallons per day (MGD) from EPA discharge monitoring reports, the standard measure of a plant’s size. Design capacity, the flow a plant is permitted to treat, is usually higher and is shown on each profile.

Try for free Log in

The 50 largest wastewater treatment plants in Louisiana

Name: Largest wastewater treatment plants in Louisiana
Creator: Klarifi
License: https://klarifi.io/terms-of-service

Ranked by average flow · 172 MGD combined · 84% of the state's reported flow

South Wastewater Treatment Plant in Baton Rouge is the largest publicly owned wastewater treatment plant in Louisiana by reported average flow, treating about 33 million gallons per day. The 50 plants below treat 172 MGD between them, 84% of the flow reported by all 259 plants in the state, and serve about 1,585,712 people. Every plant links to its profile with permit, technology and compliance data.

All plants in Louisiana →The 100 largest US plants →Louisiana NPDES permits →

The 50 largest publicly owned wastewater treatment plants in Louisiana by average flow (MGD), with population served, NPDES permit, expiry, treatment technology and three-year violation count.
#	Facility	City	Avg flow (MGD)	Population	NPDES permit	Expires	Technology	Violations (3y)
1	South Wastewater Treatment Plant	Baton Rouge	33	222,805	LA0036412	Jun 2029	Clarifiers, Biogas silos, Biogas balloons	20
2	Jefferson Parish Department Of Sewerage- East Bank WWTP	Elmwood	20.66	204,680	LA0066630	Jul 2028	Clarifiers, Biogas silos	0
3	Baton Rouge, City Of	Scotlandville	11	120,344	LA0036439	Jul 2029	Clarifiers, Biogas silos, Biogas balloons	30
4	Sewerage & Water Board Of New Orleans Westb Ank Sewage	New Orleans	10.13	184,212	LA0038105	Nov 2029	Clarifiers, Biogas balloons	1
5	Jefferson Parish Department Of Sewerage- Marrero WWTP	Marrero	6.19	78,085	LA0042048	Oct 2026	Clarifiers, Biogas balloons	5
6	Monroe, City Of (wpc Cntr)	Monroe	6.09	60,381	LAL038741	Dec 2030	Clarifiers, Aerated lagoons, Uncovered lagoons, Biogas balloons	78
7	Plant B	Lake Charles	5.74	50,000	LAL036366	Dec 2030	Clarifiers, Carrousels / oxidation ditches	73
8	Hammond North STP	Hammond	4.87	31,466	LA0032328	Aug 2028	Aerated lagoons, Uncovered lagoons, Carrousels / oxidation ditches	36
9	Red River Wastewater Treatment Plant	Bossier City	4.48	57,310	LA0053716	May 2028	Clarifiers, Carrousels / oxidation ditches	0
10	Lafayette Consolidated Government - Ambassador Caffery STP	Lafayette	4.38	36,723	LA0042561	Oct 2024	Carrousels / oxidation ditches, Biogas silos	0
11	St. Bernard Parish - Munster WWTP	Chalmette	3.77	15,255	LA0040177	Oct 2025	—	2
12	Northeast Wastewater Treatment Plant	Bossier City	3.76	18,460	LA0065978	Mar 2026	Clarifiers, Carrousels / oxidation ditches	0
13	Carrollton Water Purification Plant	New Orleans	3.38	—	LA0000086	Jun 2025	Uncovered lagoons, Biogas silos	53
14	Ruston, City Of- Northside Wastewater Treatment Plant	Ruston	3.22	22,371	LA0036323	Jun 2028	Clarifiers, Carrousels / oxidation ditches	81
15	Slidell, City Of	Slidell	2.95	30,702	LA0047180	Sep 2030	Clarifiers	3
16	Shreveport North Regional WWTP	Shreveport	2.71	42,277	LAL042188	Dec 2030	Clarifiers, Aerated lagoons, Carrousels / oxidation ditches	42
17	Wards 5 & 8 Joint Sewerage Commision	Patterson	2.55	29,807	LA0068381	Sep 2030	Aerated lagoons, Uncovered lagoons	99
18	Denham Springs Wastewater Treatment Facility	Denham Springs	2.39	12,631	LAL045730	Dec 2030	Clarifiers, Aerated lagoons, Uncovered lagoons, Carrousels / oxidation ditches	207
19	Lafayette Consolidated Government - East WWTP	Lafayette	2.36	26,766	LAL036382	Dec 2030	Clarifiers, Carrousels / oxidation ditches, Biogas silos	1
20	St. Charles Parish Council--Destrehan WWTP	Destrehan	2.27	24,633	LA0073539	May 2027	Clarifiers	0
21	Thibodaux, City Of- Wastewater Treatment Facility	Thibodaux	2.1	14,907	LA0032948	Jul 2029	Clarifiers, Aerated lagoons, Biogas silos	77
22	Opelousas, City Of- Candy Street WWTP	Opelousas	1.98	15,786	LAL036404	Dec 2030	—	191
23	Abbeville Wastewater Treatment Facility	Abbeville	1.9	11,940	LAL039748	Dec 2030	Carrousels / oxidation ditches	1
24	Broussard, City Of	Broussard	1.68	3,288	LA0020613	Apr 2031	Uncovered lagoons	19
25	Jennings, City Of- WWTP	Jennings	1.61	9,697	LA0041769	Oct 2025	Clarifiers, Uncovered lagoons	16
26	Bridge City Wastewater Treatment Plant	Bridge City	1.59	51,837	LA0042064	Feb 2031	Clarifiers	14
27	St. Charles Parish Council	Hahnville	1.43	9,518	LAL073521	Dec 2030	Clarifiers, Aerated lagoons	2
28	Plaquemines Parish Government- Belle Chasse WWTP	Belle Chasse	1.34	8,711	LA0044032	Jun 2030	Clarifiers	14
29	Donaldsonville, City Of	Donaldsonville	1.34	8,135	LA0043931	Mar 2029	Aerated lagoons	18
30	Breaux Bridge Wastewater Treatment Plant	Breaux Bridge	1.32	6,997	LA0033014	Sep 2027	Uncovered lagoons	31
31	Sewerage District #1 Of Iberia Parish & City Of New Iberia- Tete Bayou WWTP	New Iberia	1.27	18,626	LA0065251	Apr 2027	Clarifiers, Aerated lagoons	108
32	Ponchatoula, City Of- Wastewater Treatment Facility	Ponchatoula	1.24	7,195	LA0044695	Jan 2031	Aerated lagoons	131
33	Bastrop Main Wastewater Treatment Facility	Bastrop	1.23	—	LAL020443	Dec 2030	Clarifiers	394
34	Harahan, City Of	Harahan	1.17	1,740	LAL043940	Dec 2030	—	124
35	Gretna City Of Wastewater Treatment Plant	Gretna	1.17	17,807	LA0041262	Aug 2028	Clarifiers, Uncovered lagoons	10
36	Youngsville Wastewater Treatment Facility	Youngsville	1.17	15,929	LA0055328	Apr 2018	Clarifiers, Aerated lagoons, Uncovered lagoons	32
37	Lafayette Consolidated Government - Northeast WWTP	Lafayette	1.16	8,099	LAL036391	Dec 2030	Clarifiers, Uncovered lagoons, Carrousels / oxidation ditches	0
38	Natchitoches, City Of	Natchitoches	1.13	18,039	LAL095222	Dec 2030	Clarifiers, Uncovered lagoons, Carrousels / oxidation ditches	23
39	Delhi, Town Of - WWTP	Delhi	1.1	3,138	LA0039802	Nov 2027	Clarifiers, Uncovered lagoons, Carrousels / oxidation ditches	104
40	Crowley WWTP	Crowley	1.1	14,898	LA0041254	Oct 2030	Aerated lagoons, Uncovered lagoons	43
41	Oakdale, City Of	Oakdale	1.07	6,692	LA0033430	Jul 2029	Clarifiers, Aerated lagoons, Uncovered lagoons	90
42	Rayville WWTF	Rayville	1.05	3,781	LA0020559	May 2028	Aerated lagoons, Uncovered lagoons	180
43	Village Of Parks WWTF	Parks	0.92	—	LA0050006	Jul 2026	—	114
44	St John The Baptist Parish- Reserve WWTP	Reserve	0.91	8,611	LA0127097	Nov 2027	—	11
45	Luling Oxidation Pond	Luling	0.84	13,687	LA0032131	May 2028	Aerated lagoons, Uncovered lagoons	7
46	Leesville, City Of	Leesville	0.81	9,211	LA0043575	Aug 2028	Uncovered lagoons, Carrousels / oxidation ditches	124
47	Scott Wastewater Treatment Facility	Scott	0.77	8,729	LA0034495	Aug 2028	Uncovered lagoons	181
48	Deridder City Of - Deridder Animal Shelter	Deridder	0.7	11,257	LA0038407	Jan 2031	—	40
49	New Roads, City Of- Wastewater Treatment Plant	New Roads	0.7	5,900	LA0038555	Apr 2027	Uncovered lagoons	63
50	Town Of Iowa Sd #1	Iowa	0.65	2,649	LA0043605	Jan 2031	—	75

Largest plants 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 September 11, 2026.

Try Klarifi for free

Create your own trial account and explore how Klarifi can help you.

Try for free