How many wastewater treatment plants are there in Illinois?

Klarifi tracks 664 publicly owned wastewater treatment plants in Illinois with a combined average flow of 1,011 million gallons per day, serving about 5,851,332 residents. 93 of them treat more than 1 MGD and 13 more than 10 MGD.

What is the largest wastewater treatment plant in Illinois?

Metropolitan Water Reclamation in Chicago is the largest plant in Illinois by average flow, treating about 281.73 MGD.

What treatment technologies are common in Illinois?

471 of Illinois's plants use lagoon systems and 93 have biogas or anaerobic digestion infrastructure, based on Klarifi's aerial imagery review.

How many NPDES permits in Illinois are up for renewal?

19 permits held by Illinois plants expire in 2026 and 302 in 2027. Renewals typically bring new limits and trigger upgrade projects.

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Wastewater treatment plants in Illinois

Name: Wastewater treatment plants in Illinois
Creator: Klarifi
License: https://klarifi.io/terms-of-service

664 facilities · 1,011 MGD combined flow

Klarifi tracks 664 publicly owned wastewater treatment plants in Illinois with a combined average flow of 1,011 MGD, serving about 5,851,332 residents. 93 plants treat more than 1 MGD and 13 more than 10 MGD; 471 use lagoon systems and 93 have digesters or biogas infrastructure. The largest is Metropolitan Water Reclamation in Chicago at 281.73 MGD. 19 NPDES permits expire this year and 302 next year.

Every plant below links to a profile with average and design flow, the NPDES permit and its expiry, a three-year compliance snapshot and the capital projects planned in its city. Treatment technology and verified contacts are shown with a free Klarifi account. Showing facilities 1–200 of 664 by average flow — browse the rest with the page links below.

663 plant locations in Illinois; dot size follows average flow. Boundaries: U.S. Census Bureau.

NPDES permits and renewals in Illinois

Every plant discharges under an NPDES permit that is renewed every five years, usually with tighter limits. The renewal year is the year a plant budgets for upgrades.

All NPDES permits in Illinois →19 permits expiring in 2026 →302 permits expiring in 2027 →70 permits expiring in 2028 →Find plants near you on the map →

Largest wastewater treatment plants in Illinois

The 10 largest publicly owned wastewater treatment plants in Illinois by average flow, with NPDES permit, expiry and three-year violation count. Source: EPA ICIS-NPDES via Klarifi.
Facility	City	Avg flow (MGD)	Design (MGD)	NPDES permit	Expires	Violations (3y)
Metropolitan Water Reclamation	Chicago	281.73	—	ILL028061	Dec 2030	10
MWRDGC Terrence J O'Brien Water Reclamation Plant	Skokie	205.79	450	IL0028088	Jul 2022	16
Sanitary District Of Decatur	Decatur	34.42	—	ILL028321	Dec 2030	1
Springbrook Water Reclamation Center	Naperville	20.15	—	ILL034061	Dec 2030	0
Greater Peoria Sanitary And Sewage District	Peoria	19.22	—	ILL021288	Dec 2030	12
Spring Creek STP	Springfield	16.41	—	ILL021989	Dec 2030	29
Bloomington Normal WRD -West STP	Bloomington	16.33	—	ILL027731	Dec 2030	0
Fox River Water Reclamation Dist	Elgin	13.07	—	ILL028657	Dec 2030	50
Glenbard Wastewater Authority	Glen Ellyn	11.79	—	ILL021547	Dec 2030	27
Collinsville Wastewater Treatment Plant	Collinsville	11.53	—	ILL028215	Dec 2030	5

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

The 50 largest plants in Illinois →EPA enforcement actions in Illinois →Illinois capital improvement plans →

Illinois plants by treatment technology

Lagoon systems (471)Activated sludge and clarifiers (164)Anaerobic digesters and biogas (93)Oxidation ditches (58)

All 664 plants in Illinois

Facility	City	Flow (MGD)
Metropolitan Water Reclamation	Chicago	281.73
MWRDGC Terrence J O'Brien Water Reclamation Plant	Skokie	205.79
Sanitary District Of Decatur	Decatur	34.42
Springbrook Water Reclamation Center	Naperville	20.15
Greater Peoria Sanitary And Sewage District	Peoria	19.22
Spring Creek STP	Springfield	16.41
Bloomington Normal WRD -West STP	Bloomington	16.33
Fox River Water Reclamation Dist	Elgin	13.07
Glenbard Wastewater Authority	Glen Ellyn	11.79
Collinsville Wastewater Treatment Plant	Collinsville	11.53
Flagg Creek Water Reclamation	Burr Ridge	11.38
Downers Grove Sanitary District	Downers Grove	10.66
Elmhurst Stp, City Of	Elmhurst	10.25
Lake County Public Works Department	Buffalo Grove	9.09
Woodridge-Greene Valley WWTP	Woodridge	8.92
Joliet West Stp, City Of	Joliet	8.9
Danville Sanitary District STP	Danville	8.45
Alton Waste Water Treatment Plant	Alton	7.8
Urbana & Champaign Sd	Urbana	7.76
Galesburg Sanitary District STP	Galesburg	7.4
Wheaton Sanitary District WWTF	Wheaton	7.27
Romeoville Wastewater Treatment Facility	Romeoville	6.43
Plainfield North Stp, Village Of	Plainfield	6.07
Highland Water Reclamation	Highland	5.55
Jacksonville STP	Jacksonville	5.44
Frankfort, Village Of	Frankfort	4.97
St. Charles Wastewater Treatment Facility	Saint Charles	4.44
North Slope Treatment Plant	Moline	4.25
East Moline Wastewater	East Moline	4.16
Bloomington-Normal WRD SE WWTP	Bloomington	4.04
City Of Monmouth	Monmouth	3.88
Fox River Water Reclamation Di	Elgin	3.79
Village Of Bolingbrook STP #3	Bolingbrook	3.67
Moline South Treatment Plant	Moline	3.64
City Of East Peoria Wastwater Treatment Plant	East Peoria	3.53
Kewanee STP	Kewanee	3.5
Sycamore STP - North Plant	Sycamore	3.26
Addison Stw North 3	Addison	3.21
Edwardsville Stp, City Of	Edwardsville	3.11
Pekin STP #1	Pekin	3.05
Algonquin Stw, Village Of	Algonquin	2.89
Metropolitan Water Reclamation District	Lemont	2.85
Morton STP 2	Morton	2.7
Streator STP	Streator	2.7
Rochelle City Of	Rochelle	2.68
Geneseo Stp, City Of	Geneseo	2.68
Marion SE Stp, City Of	Marion	2.63
O Fallon STP	O Fallon	2.57
Village Of Mokena Stw	Mokena	2.56
Lake In The Hills Sd	Lake In The Hills	2.56
Bartlett Stp, Village Of	Bartlett	2.46
Woodstock Northside Wastewater Treatment Plant	Woodstock	2.44
Deerfield WRF	Deerfield	2.4
Caseyville Township East STP	O Fallon	2.36
Christian County Water Reclamation District	Taylorville	2.34
Morris - Main STP	Morris	2.33
New Lenox STP #1, Village Of	New Lenox	2.24
Yorkville-Bristol Sd STP	Yorkville	2.22
Effingham STP	Effingham	2.21
Centralia Stw Main, City Of	Centralia	2.09
Canton West Stp, City Of	Canton	2.06
A.J. Larocca Wastewater Treatment Facility	Addison	1.93
Washington STP #2	Washington	1.88
Swansea Stp, Village Of	Swansea	1.81
Itasca, Village Of - Prospect Avenue WWTP	Itasca	1.65
Crest Hill East Stp, City Of	Crest Hill	1.63
Morris WWTP #2 - Stp, City Of	Morris	1.62
Wood Dale North And South STP	Wood Dale	1.58
Bolingbrook STP #1	Bolingbrook	1.57
Robinson Wwtp, City Of	Robinson	1.57
Manteno Stw, Village Of	Manteno	1.43
Mendota Stp, City Of	Mendota	1.42
Illinois American Water - Jerseyville STP	Jerseyville	1.38
Cary Wwtp, Village Of	Cary	1.37
Harrisburg STP	Harrisburg	1.37
Herrin Stp, City Of	Herrin	1.36
Murphysboro Stp, City Of	Murphysboro	1.35
Olney Stp, City Of	Olney	1.34
Roodhouse Stp, City Of	Roodhouse	1.32
Pana STP	Pana	1.25
Woodstock South Stp, City Of	Woodstock	1.24
Braidwood Stp, City Of	Braidwood	1.23
Manhattan Stw, Village Of	Manhattan	1.22
Salem Stp, City Of	Salem	1.21
Spring Valley WWTP	Spring Valley	1.14
New Lenox-STP #2, Village Of	New Lenox	1.13
East Dundee Wwtp, Village Of	East Dundee	1.13
Huntley - West WWTP	Huntley	1.11
Watseka Stw	Watseka	1.09
St. Clair Township Lincolnshire STP	Belleville	1.08
Mascoutah, City Of	Mascoutah	1.04
Huntley East Wwtp, Village Of	Huntley	1.04
Harvard Wwtp, City Of	Harvard	1.03
Crest Hill West Stp, City Of	Crest Hill	0.99
Peru STP #2	Peru	0.97
Okawville STP	Okawville	0.96
Stookey Township WWTP	Belleville	0.94
Wilmington Stp, City Of	Wilmington	0.93
City Of Waterloo STP 3	Waterloo	0.93
Illinois American Water-Godfrey Wastewater	Godfrey	0.92
Shelbyville Stw, City Of	Shelbyville	0.91
Greenville Stp, City Of	Greenville	0.9
Elburn Wwtp, Village Of	Elburn	0.88
Cambridge Stp, Village Of	Cambridge	0.87
Aqua Illinois - Peotone STP	Peotone	0.85
Auburn Stp, City Of	Auburn	0.85
Coal City Stp, Village Of	Coal City	0.84
Beecher Stp, Village Of	Beecher	0.84
Staunton Stp, City Of	Staunton	0.83
Vandalia Stp, City Of	Vandalia	0.83
Pittsfield Stp, City Of	Pittsfield	0.81
Pingree Grove, Village Of	Pingree Grove	0.78
Milan STP	Milan	0.77
Plano Stp, City Of	Plano	0.76
Morton STP 3	Morton	0.76
Roselle-J Botterman STP	Roselle	0.75
Leroy Stp, City Of	Le Roy	0.74
Christopher Stp, City Of	Christopher	0.74
Flora Stp, City Of	Flora	0.73
Eureka WTP	Eureka	0.72
Rushville Stp, City Of	Rushville	0.71
Fairfield, City Of	Fairfield	0.7
Minonk Stw, City Of	Minonk	0.7
Sparta - Southeast Stp, City Of	Sparta	0.68
Paxton Stp, City Of	Paxton	0.68
Marshall Stp, City Of	Marshall	0.67
Wbsd Wastewater Treatment Plant	Belgium	0.66
Breese Stp, City Of	Breese	0.65
Fairbury Stw, City Of	Fairbury	0.64
Georgetown Stp, City Of	Georgetown	0.62
Chester STP	Chester	0.62
Mahomet Stp, Village Of	Mahomet	0.61
Genoa Stw, City Of	Genoa	0.6
Duquoin Stp, City Of	Du Quoin	0.6
Abingdon Stp, City Of	Abingdon	0.6
East Alton Stp, Village Of	East Alton	0.59
West Frankfort Stw, City Of	West Frankfort	0.59
Arthur Stp, Village Of	Arthur	0.59
Arcola Stp, City Of	Arcola	0.59
Lebanon Stp, City Of	Lebanon	0.58
Marissa, Village Of	Marissa	0.58
Galva Southwest STP	Galva	0.58
Carlyle Stp, City Of	Carlyle	0.57
Galena South WWTF	Galena	0.56
Cortland Stp, Town Of	Cortland, Township Of	0.55
Carthage Stp, City Of	Carthage	0.55
Brighton Stp, Village Of	Brighton	0.54
Illinois American Water - Villa Grove STP	Villa Grove	0.53
Pinckneyville STP #1	Pinckneyville	0.52
Gardner STP	Gardner	0.52
Oglesby Stp, City Of	Oglesby	0.52
Diamond Wwtp, Village Of	Diamond	0.52
Farmington Sanitary District STP	Farmington	0.52
Neoga Stp, City Of	Neoga	0.5
Mounds Stp, City Of	Mounds	0.5
Stockton Stp, Village Of	Stockton	0.5
Milford Stp, Village Of	Milford	0.5
East Peoria #3 STP	East Peoria	0.5
Carterville Stp, City Of	Carterville	0.49
Caseyville Township West STP	O Fallon	0.49
Mount Olive North STP	Mount Olive	0.48
Amboy Stp, City Of	Amboy	0.48
Casey - Northeast Stp, City Of	Casey	0.47
Johnston City STP	Johnston City	0.47
Nashville Stp, City Of	Nashville	0.47
Carrollton Stp, City Of	Carrollton	0.46
Gilman North Stp, City Of	Gilman	0.46
Orion Wastewater Treatment Plant	Orion	0.46
Windsor Stp, City Of	Windsor	0.45
St Charles Main Stw East, Stw West	Saint Charles	0.45
Crystal Lake WWTP #3	Crystal Lake	0.44
Tuscola STP	Tuscola	0.44
El Paso Stp, City Of	El Paso	0.44
Elmwood Stp, City Of	Elmwood	0.43
Marengo Stp, City Of	Marengo	0.42
Newton Stw	Newton	0.41
Sangamon Valley Pwd STP	Mahomet	0.41
Farmer City Stp, City Of	Farmer City	0.4
Tuscola - Southside STP	Tuscola	0.4
Sparland Stp, Village Of	Sparland	0.4
Virginia Stp, City Of	Virginia	0.4
Mt Sterling - Stp, City Of	Mount Sterling	0.39
Roanoke Stp, Village Of	Roanoke	0.39
Mount Sterling SE Stp, City Of	Mount Sterling	0.39
Anna Stw, City Of	Anna	0.38
Delavan Stp, City Of	Delavan	0.37
Smithton Stp, Village Of	Smithton	0.37
Fulton Wwtp, City Of	Fulton	0.37
Lakewood Stp, Village Of	Lakewood	0.36
Chillicothe Sd	Chillicothe	0.36
Glasford Stp, Village Of	Glasford	0.36
Aqua Illinois - Grant Park STP	Grant Park	0.35
Sesser Stp, City Of	Sesser	0.35
Tremont Stp, Village Of	Tremont	0.35
Lanark Stp, City Of	Lanark	0.35
Metamora North Stp, Village Of	Metamora	0.35
Rockton Stp, Village Of	Rockton	0.35
Millstadt Stp, Village Of	Millstadt	0.34
Earlville Stp, City Of	Earlville	0.34
Heyworth Stp, Village Of	Heyworth	0.33

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Wastewater treatment in Illinois: 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 · Inflow and infiltration · Sludge dewatering · 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. “Wastewater treatment plants in Illinois.” Updated October 26, 2026. https://klarifi.io/facilities/illinois

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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