Which wastewater plant serves the most people?

Joint Water Pollution Control Plant in Carson, California serves about 3,353,576 residents according to the Clean Watersheds Needs Survey 2022.

How is "largest" measured?

By average daily flow in million gallons per day (MGD) as reported to the EPA in discharge monitoring reports, ranked from the most recent reporting period. Design capacity, shown alongside, is the permitted maximum.

How often is this ranking updated?

The underlying snapshot is refreshed from EPA data on every release of klarifi.io; the refresh date is shown at the bottom of the page.

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The 100 largest wastewater treatment plants in the United States

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

Ranked by average flow · 6,657 MGD combined

GLWA Water Resource Recovery Facility in Detroit, Michigan is the largest publicly owned wastewater treatment plant in the United States by reported average flow, treating about 349 million gallons per day. The 100 plants below together treat 6,657 MGD. New York has 17, Texas has 14, California has 9, Ohio has 5 and Michigan has 4 of them.

Flow is the average discharge reported to the EPA over the most recent monitoring period, not the plant's design capacity, so wet-weather plants and combined-sewer systems rank by what they actually treat. Population served comes from the Clean Watersheds Needs Survey 2022. Plants whose reported flow fails a plausibility check against their design capacity or population (a unit error in the source data) are left out until the record is corrected; MWRD Chicago's Stickney plant, the largest in the country by capacity, is one of them. Every plant links to its profile with permit, technology, compliance and capital-project data.

The 100 largest publicly owned wastewater treatment plants in the United States by average flow, from EPA ICIS-NPDES discharge monitoring records and the Clean Watersheds Needs Survey, via Klarifi. Refreshed on every release.
#	Facility	City	State	Avg flow (MGD)	Design (MGD)	Population	Technology	Violations (3y)
1	GLWA Water Resource Recovery Facility	Detroit	MI	349	—	2,844,020	Clarifiers	38
2	Deer Island Wastewater Treatment Facility	Winthrop	MA	233.7	480	2,317,098	Biogas silos, Biogas balloons	3
3	Hyperion Treatment Plant	Playa Del Rey	CA	214	450	2,800,773	Clarifiers	42
4	Central District Wastewater Treatment Plant	Key Biscayne	FL	194.6	143	—	Biogas silos, Biogas balloons	67
5	Newtown Creek Water Pollution Control Plant	Brooklyn	NY	188	310	1,109,558	Clarifiers, Biogas silos, Biogas balloons	5
6	Met Council Metropolitan WWTP	Saint Paul	MN	180	—	2,033,541	Biogas silos	0
7	NYC-DEP Wards Island WPCP	Manhattan	NY	174	275	1,102,853	Clarifiers, Biogas silos	25
8	MWRDGC Terrence J O'Brien Water Reclamation Plant	Skokie	IL	170	450	946,333	Clarifiers, Biogas balloons	18
9	Joint Water Pollution Control Plant	Carson	CA	162.85	400	3,353,576	—	19
10	Allegheny Cnty Sani Auth/allegheny Cnty	Pittsburgh	PA	152.8	—	—	—	1
11	Village Creek Reclamation Facility	Arlington	TX	142	166	1,136,072	Clarifiers, Biogas silos, Biogas balloons	3
12	Point Loma Wastewater Treatment Plant	San Diego	CA	137	240	2,222,389	Biogas silos	1689
13	Back River Wastewater Treatment Plant	Baltimore	MD	114.1	—	432,114	Clarifiers, Uncovered lagoons, Biogas silos, Biogas balloons	32
14	NYC-DEP North River WPCP	New York	NY	110	—	611,675	—	2
15	Hunts Point Water Pollution Control Plant	Bronx	NY	109	200	711,199	Clarifiers, Biogas silos	11
16	Dos Rios Water Recycling Center	San Antonio	TX	105.32	125	1,161,197	Clarifiers, Aerated lagoons, Biogas silos	48
17	City Of Dallas Central WWTP	Dallas	TX	104	200	744,579	Clarifiers, Aerated lagoons, Uncovered lagoons, Biogas silos	10
18	Milwaukee Metro Sew Dist Combi	Milwaukee	WI	95.1	123	531,068	—	392
19	Nycdep - Bowery Bay WRRF	Astoria	NY	94	150	881,328	Clarifiers, Biogas silos	10
20	Metropolitan St. Louis Sewer District Bissell Point WWTP	St. Louis	MO	90.1	—	304,678	Clarifiers, Biogas balloons	14
21	Metro Central Wastewater Treatment Plant	Nashville	TN	88.2	—	649,235	Clarifiers	62
22	Owls Head Water Pollution Control Plant	Brooklyn	NY	88	120	787,493	Biogas silos	9
23	Indianapolis Belmont WWTP	Indianapolis	IN	83.83	125	959,530	Biogas balloons	116
24	Coney Island Water Pollution Control Plant	Brooklyn	NY	83	110	619,523	—	8
25	Southerly Wastewater Treatment Plant	Lockbourne	OH	82.1	—	706,507	Clarifiers, Biogas silos	7
26	Metropolitan St. Louis Sewer District Lemay WWTP	St. Louis	MO	79.3	—	453,428	Clarifiers, Biogas silos	0
27	91st Avenue WWTP	Tolleson	AZ	78.71	230	—	Clarifiers, Uncovered lagoons, Carrousels / oxidation ditches, Biogas silos	2
28	Wilmington Wastewater Treatment Plant- 12th St & Hay Rd, Wilmington	Wilmington	DE	78.67	—	530,079	Clarifiers, Uncovered lagoons	5
29	Southerly Wastewater Treatment Center	Cleveland	OH	78.11	—	555,185	Clarifiers, Biogas balloons	3
30	Middlesex County Utilities Authority	Sayreville	NJ	77.42	147	924,565	Clarifiers, Uncovered lagoons, Biogas silos	17
31	Orange County Sanitation District Plant 1	Fountain Valley	CA	77.37	332	—	Clarifiers	0
32	Phila Water Dept - SE STP	Philadelphia	PA	77	—	268,286	—	1
33	Wilson Creek Regional Wastewater Treatment Plant	Mc Kinney	TX	70.77	24	244,117	Clarifiers, Carrousels / oxidation ditches, Biogas balloons	24
34	Jamaica Water Pollution Control Plant	Jamaica	NY	70	100	756,447	Clarifiers, Biogas silos	10
35	Richmond WWTP	Richmond	VA	63.4	—	278,696	Clarifiers, Biogas silos	31
36	Bergen County Utilities Authority	Little Ferry	NJ	63.2	94	575,131	Clarifiers, Uncovered lagoons, Biogas silos	176
37	Cedar Creek WPCP	Wantagh	NY	62.2	72	653,795	Clarifiers, Biogas silos, Biogas balloons	12
38	West Boise WWTP	Garden City	ID	62	24	380,979	Clarifiers, Uncovered lagoons, Biogas silos	9
39	Tallman Island Wastewater Treatment Plant	Queens	NY	57	80	426,793	Clarifiers, Biogas balloons	2
40	Walnut Creek WWTP	Austin	TX	56.6	100	400,000	Clarifiers, Uncovered lagoons	0
41	Msd, Morris Forman Plant	Louisville	KY	56.18	120	569,690	Clarifiers, Uncovered lagoons, Biogas balloons	221
42	Westchester Co Of - Yonkers Joint Waste Water Treatment Plant	Yonkers	NY	55	120	495,659	Biogas silos	29
43	Southwest WWTP	Houston	TX	50.14	60	100,000	Clarifiers	68
44	Patapsco Wastewater Treatment Plant	Baltimore	MD	49.01	—	293,367	Clarifiers, Biogas silos, Biogas balloons	22
45	Bay Park Sewage Treatment Plant	East Rockaway	NY	48.5	70	584,105	Clarifiers, Biogas balloons	4
46	Hillebrandt WWTP	Beaumont	TX	47.3	46	140,984	Clarifiers, Aerated lagoons, Uncovered lagoons	24
47	Neuse River Resource Recovery Facility	Raleigh	NC	47.06	75	570,019	Clarifiers, Aerated lagoons, Uncovered lagoons, Biogas silos, Biogas balloons	1
48	Ccsf- Southeast Water Pollution Control Plant	San Francisco	CA	45.87	400	585,360	Clarifiers, Biogas silos	13
49	Albany County Sewer District - South Plant	Albany	NY	45.11	29	101,989	Clarifiers, Uncovered lagoons, Biogas silos	49
50	Essex & Union Cnty Joint Meeting STP	Elizabeth	NJ	44.93	220	421,182	Clarifiers, Carrousels / oxidation ditches, Biogas silos	145
51	Akron WRF	Akron	OH	44.82	90	321,892	Clarifiers, Uncovered lagoons	0
52	South Austin Regional WWTP Electrical	Del Valle	TX	43.8	75	457,525	Clarifiers, Biogas balloons	0
53	Delaware #1 Water Pollution Control Facility	Camden	NJ	43.19	185	468,135	Biogas silos, Biogas balloons	6
54	NYC DEP 26 Ward WPCP	Brooklyn	NY	43	85	294,453	Biogas silos	13
55	Derek R Guthrie WQTC MSD	Louisville	KY	39.73	60	109,588	Clarifiers	16
56	City Of Toledo Division Of Water Reclaimation	Toledo	OH	39.6	—	289,101	Clarifiers, Uncovered lagoons, Biogas silos, Biogas balloons	3
57	Okc South Canadian Wwt	Oklahoma City	OK	39.41	80	40,017	—	189
58	City Of Dayton Water Reclamation Facility (0857100983)	Dayton	OH	38.22	72	184,008	Clarifiers, Biogas silos, Biogas balloons	17
59	South Mesquite Regional Wastewater Treatment Plant	Mesquite	TX	37.57	41	354,544	Clarifiers, Biogas silos	23
60	Moccasin Bend Wastewater Treatment Plant	Chattanooga	TN	36.67	—	262,562	Clarifiers, Aerated lagoons, Uncovered lagoons, Biogas silos	53
61	23rd Avenue Wastewater Treatment Plant	Phoenix	AZ	35.67	63	1,604,039	Clarifiers, Biogas silos	2
62	Noman M Cole Jr Pollution Control Plant	Lorton	VA	34.8	—	369,668	Clarifiers, Aerated lagoons	0
63	City Of Grand Rapids Wastewater Treatment Plant	Grand Rapids	MI	33.4	—	344,538	Clarifiers, Aerated lagoons, Biogas silos, Biogas balloons	9
64	Augusta WWTP	Augusta	GA	33.2	46.1	172,073	Clarifiers, Biogas silos, Biogas balloons	10
65	South Wastewater Treatment Plant	Baton Rouge	LA	33	54	222,805	Clarifiers, Biogas silos, Biogas balloons	20
66	Roberto R Bustamante WWTP	El Paso	TX	32.92	39	377,670	Clarifiers, Uncovered lagoons, Biogas silos, Biogas balloons	35
67	Gary Sanitary District	Gary	IN	32.6	60	195,005	Clarifiers, Biogas silos, Biogas balloons	24
68	Leon Creek Water Recycling Center	San Antonio	TX	32	46	165,587	Clarifiers	5
69	Pima County - Ina Road WWTP	Tucson	AZ	31.89	50	400,657	Clarifiers, Uncovered lagoons, Biogas silos	3
70	Riverside Park Water Reclamation Facility	Spokane	WA	31.72	—	185,960	Clarifiers, Biogas silos	4
71	Salt Lake City Water Reclamation Plant	Salt Lake City	UT	31.1	56	—	Clarifiers, Biogas silos	1
72	City Of Allentown Wastewater Treatment Plant	Allentown	PA	31.07	40	108,967	Clarifiers, Carrousels / oxidation ditches, Biogas silos, Biogas balloons	0
73	Dekalb County Department Of Watershed Management (snapfinger Creek Awtf)	Decatur	GA	30.42	36	243,846	Clarifiers, Biogas silos, Biogas balloons	1
74	Pole Bridge Creek Advanced Wastewater Facility	Lithonia	GA	30.42	20	109,554	Clarifiers, Carrousels / oxidation ditches	4
75	Pecan Creek Water Reclamation Plant	Denton	TX	30.27	21	148,099	Clarifiers, Biogas silos	8
76	Water Pollution Control Plant	Fort Wayne	IN	29.9	74	312,389	Clarifiers, Biogas silos, Biogas balloons	2
77	Metro Wastewater Treatment Plant	Columbia	SC	29.87	60	314,797	Clarifiers, Uncovered lagoons, Biogas silos	7
78	Little Blue Valley Sewer District	Independence	MO	29.2	—	39,046	Clarifiers, Aerated lagoons, Covered lagoons, Carrousels / oxidation ditches, Biogas silos, Biogas balloons	14
79	Stockton Rwcf	Stockton	CA	29.2	55	335,503	Clarifiers, Uncovered lagoons, Biogas silos	57
80	Valley Creek Wastewater Treatment Plant	Bessemer	AL	29.2	—	214,985	Clarifiers, Biogas silos, Biogas balloons	1
81	South Bay International WWTP	San Diego	CA	29	25	146,085	Clarifiers, Biogas silos	3159
82	City Of Houston	Houston	TX	28.8	25	100,000	Clarifiers	3
83	San Jose Creek Water Reclamation Plant	Whittier	CA	28.38	100	936,523	—	26
84	Nycdep - Red Hook WPCP	Brooklyn	NY	28	60	199,521	Biogas silos	2
85	Riverside City, Water Quality Control	Riverside	CA	27.72	46	366,930	Clarifiers, Aerated lagoons, Uncovered lagoons, Biogas silos, Biogas balloons	2
86	Delcora-Western Regional Treatment Plant	Chester	PA	27.54	44	107,437	Clarifiers	18
87	Green Bay Metropolitan Sewerage District	Green Bay	WI	27.53	—	—	Clarifiers, Carrousels / oxidation ditches, Biogas silos, Biogas balloons	7
88	South Columbus Water Resource Facility	Columbus	GA	27.02	42	212,000	Clarifiers, Biogas silos	2
89	Plum Island WWTP	Charleston	SC	27	36	232,756	Clarifiers, Biogas balloons	3
90	Wyandotte Wastewater Plant	Wyandotte	MI	26.9	—	—	Clarifiers, Biogas silos, Biogas balloons	5
91	Bergen Point STP & Bergen Ave Dock	W Babylon	NY	26.7	30.5	400,000	Clarifiers, Uncovered lagoons, Biogas silos	81
92	Blue Lake Wastewater Treatment Plant	Shakopee	MN	26.54	42	339,518	Biogas silos, Biogas balloons	0
93	Sanitary District Of Decatur	Decatur	IL	26.53	—	78,304	Clarifiers, Biogas silos, Biogas balloons	1
94	Saniatry District Of Hammond	Hammond	IN	25.83	37.8	156,645	Clarifiers, Uncovered lagoons, Biogas silos	21
95	Nycdep - Oakwood Beach WPCP	Staten Island	NY	25.4	39.9	254,445	Biogas silos, Biogas balloons	6
96	Southwest WWTP	Springfield	MO	25.32	—	206,375	Clarifiers, Aerated lagoons, Uncovered lagoons, Carrousels / oxidation ditches, Biogas silos, Biogas balloons	0
97	New Vince Bayou WWTF	Pasadena	TX	25	14	113,435	Clarifiers, Carrousels / oxidation ditches	139
98	Kalamazoo Water Reclamation Plant	Kalamazoo	MI	24.94	—	166,409	Clarifiers, Biogas silos, Biogas balloons	37
99	Truckee Meadows Water Reclamation Facility	Reno	NV	24.7	—	71,000	Clarifiers, Uncovered lagoons, Biogas silos	1
100	Willow Lake WWTP	Salem	OR	24.62	—	284,938	Clarifiers, Carrousels / oxidation ditches, Biogas silos	2

Looking for a specific state? Browse all 50 state directories →

Largest wastewater plants: 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.

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