How many wastewater treatment plants are there in Connecticut?

Klarifi tracks 55 publicly owned wastewater treatment plants in Connecticut with a combined average flow of 214 million gallons per day, serving about 1,743,534 residents. 32 of them treat more than 1 MGD and 4 more than 10 MGD.

What is the largest wastewater treatment plant in Connecticut?

Hartford Water Pollution Control Facility in Hartford is the largest plant in Connecticut by average flow, treating about 56.89 MGD.

What treatment technologies are common in Connecticut?

5 of Connecticut's plants use lagoon systems and 23 have biogas or anaerobic digestion infrastructure, based on Klarifi's aerial imagery review.

How many NPDES permits in Connecticut are up for renewal?

7 permits held by Connecticut plants expire in 2026 and 2 in 2027. Renewals typically bring new limits and trigger upgrade projects.

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Wastewater treatment plants in Connecticut

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

55 facilities · 214 MGD combined flow

Klarifi tracks 55 publicly owned wastewater treatment plants in Connecticut with a combined average flow of 214 MGD, serving about 1,743,534 residents. 32 plants treat more than 1 MGD and 4 more than 10 MGD; 5 use lagoon systems and 23 have digesters or biogas infrastructure. The largest is Hartford Water Pollution Control Facility in Hartford at 56.89 MGD. 7 NPDES permits expire this year and 2 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.

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

NPDES permits and renewals in Connecticut

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 Connecticut →7 permits expiring in 2026 →Find plants near you on the map →

Largest wastewater treatment plants in Connecticut

The 10 largest publicly owned wastewater treatment plants in Connecticut 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)
Hartford Water Pollution Control Facility	Hartford	56.89	—	CTL000004	Dec 2030	3
Westside Water Pollution Control Facility	Bridgeport	17.54	30	CT0100056	Jun 2024	65
Stamford Water Pollution Control Facility	Stamford	13.83	24	CT0101087	Dec 2023	11
Norwalk WPCF	East Norwalk	11.32	18	CT0101249	Mar 2026	13
Meriden Water Pollution Control Facility	Meriden	9.93	11.6	CT0100315	Dec 2023	10
Danbury Water Pollution Control Facility	Danbury	9.24	15.5	CT0100145	Jun 2026	5
Fairfield Water Pollution Control Facility	Fairfield	7.87	9	CT0101044	Sep 2026	4
Stratford Water Pollution Control Facility	Stratford	7.32	11.5	CT0101036	Sep 2025	37
Piacenti Wastewater Treatment Plant	New London	6.48	10	CT0100382	Apr 2027	8
Greenwich WPCF	Greenwich	6.44	12.5	CT0100234	Jul 2024	4

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

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

Connecticut plants by treatment technology

Activated sludge and clarifiers (35)Anaerobic digesters and biogas (23)Oxidation ditches (7)Lagoon systems (5)

All 55 plants in Connecticut

Facility	City	Flow (MGD)
Hartford Water Pollution Control Facility	Hartford	56.89
Westside Water Pollution Control Facility	Bridgeport	17.54
Stamford Water Pollution Control Facility	Stamford	13.83
Norwalk WPCF	East Norwalk	11.32
Meriden Water Pollution Control Facility	Meriden	9.93
Danbury Water Pollution Control Facility	Danbury	9.24
Fairfield Water Pollution Control Facility	Fairfield	7.87
Stratford Water Pollution Control Facility	Stratford	7.32
Piacenti Wastewater Treatment Plant	New London	6.48
Greenwich WPCF	Greenwich	6.44
Milford - Housatonic WPCF	Milford	5.85
Hockanum River Water Pollution Control Facility	Manchester	5.55
Eastside Water Pollution Control Facility	Bridgeport	5.24
Southington WPCF	Southington (plantsville)	4.5
Torrington Water Pollution Control Facility	Torrington	4.35
Enfield Water Pollution Control Facility	Enfield	3.97
Branford Water Pollution Control Facility	Branford	3.44
Killingly Water Pollution Control Fac.	Danielson	3.4
Chesire,water Pollution Control Facility	Cheshire	2.51
South Windsor Water Pollution Control Facility	South Windsor	2.51
Glastonbury Water Pollution Control Facility	Glastonbury	2.5
Shelton Water Pollution Control Facility	Shelton	2.12
Westport WPCF	Westport	1.84
Ansonia Water Pollution Control Facility	Ansonia	1.71
Simsbury Water Pollution Control Facility	Simsbury	1.66
Willimantic WPCF	Willimantic	1.64
East Hampton Water Pollution Control Facility	East Hampton	1.4
Winsted WPCF	Winsted	1.33
University Of Ct Water Pollution Control Facility	Storrs	1.25
Montville Water Pollution Control Facility	Montville (uncasville)	1.25
Seymour WPCF	Seymour	1.12
Putnam W P C F	Putnam	1.01
Thomaston WPCF	Thomaston	0.92
New Canaan Wastewater Treatment Plant	New Canaan	0.87
Stafford / WPCF	Stafford Springs	0.76
Plainfield North Water Pollution Control Facility	Plainfield	0.55
Canton WPCF	Canton	0.53
Mystic WPCF	Mystic	0.52
Litchfield WPCF	Bantam	0.46
Portland Water Pollution Control Facility	Portland	0.36
Plainfield Village Sewage Treatment Plant	Plainfield	0.36
Beacon Falls Water Pollution Control Fac	Beacon Falls	0.34
Newtown /wpcf	Newtown	0.34
Town Of Salisbury WPCF	Salisbury	0.31
Canaan Fire District	North Canaan	0.29
Town Of Norfolk WPCF	Norfolk	0.2
Deep River Water Pollution Control Facility	Deep River	0.18
Stonington Borough WPCF	Stonington	0.17
Ledyard Water Pollution Control Facility	Ledyard	0.13
Somers WPCF	Somers	0.05
Sharon Water Pollution Control Facility	Sharon	0.04
New Hartford WPCF	New Hartford	0.04
Redding Wastewater Treatment Facility	Redding	0.03
East Haddam Water Pollution Control Facility	East Haddam	0.01
Sprague Wastewater Treatment Plant	Baltic	—

Wastewater treatment in Connecticut: 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 · Activated sludge · Oxidation ditch · 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 Connecticut.” Updated October 26, 2026. https://klarifi.io/facilities/connecticut

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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