What is the largest wastewater treatment plant in Louisiana?

South Wastewater Treatment Plant in Baton Rouge, treating an average of 41.82 MGD under NPDES permit LA0036412. Jefferson Parish Department Of Sewerage- East Bank WWTP in Elmwood is second at 28.23 MGD.

How much wastewater do Louisiana’s largest plants treat?

The 50 largest plants treat 233 MGD combined, 83% of the flow reported by all 277 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.

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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 · 233 MGD combined · 83% 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 41.82 million gallons per day. The 50 plants below treat 233 MGD between them, 83% of the flow reported by all 277 plants in the state, and serve about 1,655,424 people. Every plant links to its profile with permit and compliance data. Treatment technology is shown with a free Klarifi account.

All plants in Louisiana →The 50 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 and three-year violation count.
#	Facility	City	Avg flow (MGD)	Population	NPDES permit	Expires	Violations (3y)
1	South Wastewater Treatment Plant	Baton Rouge	41.82	222,805	LA0036412	Jun 2029	21
2	Jefferson Parish Department Of Sewerage- East Bank WWTP	Elmwood	28.23	204,680	LA0066630	Jul 2028	0
3	Baton Rouge, City Of	Scotlandville	20.18	120,344	LA0036439	Jul 2029	33
4	Sewerage & Water Board Of New Orleans Westb Ank Sewage	New Orleans	13.61	184,212	LA0038105	Nov 2029	1
5	Wastewater Treatment Plant, Hudson Site	Alexandria	8.46	50,991	LA0041009	Dec 2030	2
6	Jefferson Parish Department Of Sewerage- Marrero WWTP	Marrero	8.08	78,085	LA0042048	Oct 2026	5
7	Monroe, City Of (wpc Cntr)	Monroe	7.62	60,381	LAL038741	Dec 2030	78
8	Hammond North STP	Hammond	7.21	31,466	LA0032328	Aug 2028	37
9	St. Bernard Parish - Munster WWTP	Chalmette	7.08	15,255	LA0040177	Aug 2031	2
10	Plant B	Lake Charles	6.53	50,000	LAL036366	Dec 2030	73
11	Lafayette Consolidated Government - Ambassador Caffery STP	Lafayette	5.29	36,723	LA0042561	Sep 2031	0
12	Red River Wastewater Treatment Plant	Bossier City	4.62	57,310	LA0053716	May 2028	0
13	Shreveport North Regional WWTP	Shreveport	3.78	42,277	LAL042188	Dec 2030	42
14	Northeast Wastewater Treatment Plant	Bossier City	3.57	18,460	LA0065978	Mar 2026	0
15	Slidell, City Of	Slidell	3.47	30,702	LA0047180	Sep 2030	4
16	Ruston, City Of- Northside Wastewater Treatment Plant	Ruston	3.31	22,371	LA0036323	Jun 2028	68
17	Wards 5 & 8 Joint Sewerage Commision	Patterson	3.17	29,807	LA0068381	Sep 2030	99
18	St. Charles Parish Council--Destrehan WWTP	Destrehan	3.1	24,633	LA0073539	Jul 2027	0
19	Denham Springs Wastewater Treatment Facility	Denham Springs	2.67	12,631	LAL045730	Dec 2030	193
20	Lafayette Consolidated Government - East WWTP	Lafayette	2.58	26,766	LAL036382	Dec 2030	1
21	Opelousas, City Of- Candy Street WWTP	Opelousas	2.52	15,786	LAL036404	Dec 2030	186
22	Thibodaux, City Of- Wastewater Treatment Facility	Thibodaux	2.43	14,907	LA0032948	Jul 2029	77
23	Abbeville Wastewater Treatment Facility	Abbeville	2.33	11,940	LAL039748	Dec 2030	1
24	Bridge City Wastewater Treatment Plant	Bridge City	2.33	51,837	LA0042064	Feb 2031	14
25	Gretna City Of Wastewater Treatment Plant	Gretna	2.25	17,807	LA0041262	Aug 2028	10
26	City Of Gonzales Water System	Gonzales	1.96	7,167	LAL109576	Dec 2030	22
27	Plaquemines Parish Government- Belle Chasse WWTP	Belle Chasse	1.9	8,711	LA0044032	Jun 2030	14
28	Crowley WWTP	Crowley	1.89	14,898	LA0041254	Oct 2030	43
29	Deridder City Of - Deridder Animal Shelter	Deridder	1.86	11,257	LA0038407	Jan 2031	39
30	St. Charles Parish Council	Hahnville	1.82	9,518	LAL073521	Dec 2030	2
31	Luling Oxidation Pond	Luling	1.66	13,687	LA0032131	Jun 2028	9
32	City Of Mandeville	Mandeville	1.64	12,095	LAL038288	Dec 2030	22
33	Covington Sewerage Treatment Facility	Covington	1.62	11,564	LA0084336	Aug 2031	2
34	Sewerage District #1 Of Iberia Parish & City Of New Iberia- Tete Bayou WWTP	New Iberia	1.6	18,626	LA0065251	Apr 2027	115
35	Ponchatoula, City Of- Wastewater Treatment Facility	Ponchatoula	1.54	7,195	LA0044695	Jan 2031	122
36	Jennings, City Of- WWTP	Jennings	1.44	9,697	LA0041769	Oct 2025	16
37	Youngsville Wastewater Treatment Facility	Youngsville	1.42	15,929	LA0055328	Apr 2018	32
38	Delhi, Town Of - WWTP	Delhi	1.41	3,138	LA0039802	Dec 2027	100
39	Donaldsonville, City Of	Donaldsonville	1.4	8,135	LA0043931	Mar 2029	18
40	Natchitoches, City Of	Natchitoches	1.35	18,039	LAL095222	Dec 2030	11
41	Rayville WWTF	Rayville	1.29	3,781	LA0020559	May 2028	156
42	St John The Baptist Parish- Reserve WWTP	Reserve	1.29	8,611	LA0127097	Dec 2027	19
43	Harahan, City Of	Harahan	1.28	1,740	LAL043940	Dec 2030	130
44	Wastewater Treatment Plant	Pineville	1.28	14,384	LA0033464	Dec 2030	59
45	Breaux Bridge Wastewater Treatment Plant	Breaux Bridge	1.21	6,997	LA0033014	Oct 2027	22
46	Bastrop Main Wastewater Treatment Facility	Bastrop	1.19	—	LAL020443	Dec 2030	394
47	Lafayette Consolidated Government - Northeast WWTP	Lafayette	1.19	8,099	LA0036391	Sep 2031	0
48	Broussard, City Of	Broussard	1.16	3,288	LA0020613	Apr 2031	19
49	Carrollton Water Purification Plant	New Orleans	1.13	—	LA0000086	Jun 2025	52
50	Oakdale, City Of	Oakdale	1.1	6,692	LA0033430	Jul 2029	87

Treatment technology for each plant is shown with a free Klarifi account. Create one →

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 October 26, 2026.

Wastewater terms: WWTP · POTW · MGD · NPDES permit · Sludge dewatering · Biological nutrient removal · 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 Louisiana (2026).” Updated October 26, 2026. https://klarifi.io/facilities/louisiana/largest

Need a custom cut of the data for a state, a county or a list of plants? Email info@klarifi.io.

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