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Wastewater treatment plants in Connecticut

54 facilities · 169 MGD combined flow

Klarifi tracks 54 publicly owned wastewater treatment plants in Connecticut with a combined average flow of 169 MGD, serving about 1,697,979 residents. 27 plants treat more than 1 MGD and 3 more than 10 MGD; 7 use lagoon systems and 22 have digesters or biogas infrastructure. The largest is Hartford Water Pollution Control Facility in Hartford at 44.83 MGD. 6 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.

54 plant locations in Connecticut; dot size follows average flow.

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 →6 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.
FacilityCityAvg flow (MGD)Design (MGD)NPDES permitExpiresViolations (3y)
Hartford Water Pollution Control FacilityHartford44.83—CTL000004Dec 20303
Westside Water Pollution Control FacilityBridgeport16.730CT0100056Jun 202468
Stamford Water Pollution Control FacilityStamford12.524CT0101087Dec 20238
Norwalk WPCFEast Norwalk9.418CT0101249Mar 20269
Danbury Water Pollution Control FacilityDanbury7.815.5CT0100145Jun 20265
Meriden Water Pollution Control FacilityMeriden6.4911.6CT0100315Dec 202310
Fairfield Water Pollution Control FacilityFairfield5.99CT0101044Sep 20265
Greenwich WPCFGreenwich5.412.5CT0100234Jul 20245
Stratford Water Pollution Control FacilityStratford5.0211.5CT0101036Sep 202536
Hockanum River Water Pollution Control FacilityManchester4.898.2CT0100293Nov 202812

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 (22)Lagoon systems (7)Oxidation ditches (7)

All 54 plants in Connecticut

FacilityCityFlow (MGD)
Hartford Water Pollution Control FacilityHartford44.83
Westside Water Pollution Control FacilityBridgeport16.7
Stamford Water Pollution Control FacilityStamford12.5
Norwalk WPCFEast Norwalk9.4
Danbury Water Pollution Control FacilityDanbury7.8
Meriden Water Pollution Control FacilityMeriden6.49
Fairfield Water Pollution Control FacilityFairfield5.9
Greenwich WPCFGreenwich5.4
Stratford Water Pollution Control FacilityStratford5.02
Hockanum River Water Pollution Control FacilityManchester4.89
Piacenti Wastewater Treatment PlantNew London4.66
Milford - Housatonic WPCFMilford4.5
Southington WPCFSouthington (plantsville)3.67
Enfield Water Pollution Control FacilityEnfield3.01
Torrington Water Pollution Control FacilityTorrington2.99
Killingly Water Pollution Control Fac.Danielson2.95
Branford Water Pollution Control FacilityBranford2.9
Glastonbury Water Pollution Control FacilityGlastonbury2.17
South Windsor Water Pollution Control FacilitySouth Windsor2.01
Chesire,water Pollution Control FacilityCheshire1.85
Shelton Water Pollution Control FacilityShelton1.6
Simsbury Water Pollution Control FacilitySimsbury1.58
University Of Ct Water Pollution Control FacilityStorrs1.5
Westport WPCFWestport1.46
Willimantic WPCFWillimantic1.31
Ansonia Water Pollution Control FacilityAnsonia1.3
East Hampton Water Pollution Control FacilityEast Hampton1.04
Winsted WPCFWinsted0.99
Seymour WPCFSeymour0.89
Putnam W P C FPutnam0.83
Montville Water Pollution Control FacilityMontville (uncasville)0.75
Thomaston WPCFThomaston0.7
New Canaan Wastewater Treatment PlantNew Canaan0.55
Stafford / WPCFStafford Springs0.5
Canton WPCFCanton0.49
Mystic WPCFMystic0.42
Plainfield North Water Pollution Control FacilityPlainfield0.35
Newtown /wpcfNewtown0.3
Beacon Falls Water Pollution Control FacBeacon Falls0.28
Plainfield Village Sewage Treatment PlantPlainfield0.27
Litchfield WPCFBantam0.27
Portland Water Pollution Control FacilityPortland0.24
Stonington Borough WPCFStonington0.21
Town Of Salisbury WPCFSalisbury0.21
Canaan Fire DistrictNorth Canaan0.19
Deep River Water Pollution Control FacilityDeep River0.18
Town Of Norfolk WPCFNorfolk0.11
Somers WPCFSomers0.11
Ledyard Water Pollution Control FacilityLedyard0.08
Sprague Wastewater Treatment PlantBaltic0.07
New Hartford WPCFNew Hartford0.04
Sharon Water Pollution Control FacilitySharon0.03
Redding Wastewater Treatment FacilityRedding0.03
East Haddam Water Pollution Control FacilityEast Haddam0.01

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 September 14, 2026.

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