What is the largest wastewater treatment plant in Connecticut?

Hartford Water Pollution Control Facility in Hartford, treating an average of 56.89 MGD under NPDES permit CTL000004. Westside Water Pollution Control Facility in Bridgeport is second at 17.54 MGD.

How much wastewater do Connecticut’s largest plants treat?

The 50 largest plants treat 214 MGD combined, 100% of the flow reported by all 55 publicly owned plants in Connecticut.

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 Connecticut

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

Ranked by average flow · 214 MGD combined · 100% of the state's reported flow

Hartford Water Pollution Control Facility in Hartford is the largest publicly owned wastewater treatment plant in Connecticut by reported average flow, treating about 56.89 million gallons per day. The 50 plants below treat 214 MGD between them, 100% of the flow reported by all 55 plants in the state, and serve about 1,722,201 people. Every plant links to its profile with permit and compliance data. Treatment technology is shown with a free Klarifi account.

All plants in Connecticut →The 50 largest US plants →Connecticut NPDES permits →

The 50 largest publicly owned wastewater treatment plants in Connecticut 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	Hartford Water Pollution Control Facility	Hartford	56.89	224,822	CTL000004	Dec 2030	3
2	Westside Water Pollution Control Facility	Bridgeport	17.54	139,728	CT0100056	Jun 2024	65
3	Stamford Water Pollution Control Facility	Stamford	13.83	148,520	CT0101087	Dec 2023	11
4	Norwalk WPCF	East Norwalk	11.32	109,654	CT0101249	Mar 2026	13
5	Meriden Water Pollution Control Facility	Meriden	9.93	61,647	CT0100315	Dec 2023	10
6	Danbury Water Pollution Control Facility	Danbury	9.24	54,876	CT0100145	Jun 2026	5
7	Fairfield Water Pollution Control Facility	Fairfield	7.87	61,949	CT0101044	Sep 2026	4
8	Stratford Water Pollution Control Facility	Stratford	7.32	48,887	CT0101036	Sep 2025	37
9	Piacenti Wastewater Treatment Plant	New London	6.48	64,095	CT0100382	Apr 2027	8
10	Greenwich WPCF	Greenwich	6.44	63,514	CT0100234	Jul 2024	4
11	Milford - Housatonic WPCF	Milford	5.85	42,914	CT0101656	Oct 2024	32
12	Hockanum River Water Pollution Control Facility	Manchester	5.55	64,245	CT0100293	Nov 2028	11
13	Eastside Water Pollution Control Facility	Bridgeport	5.24	45,555	CT0101010	Apr 2026	36
14	Southington WPCF	Southington (plantsville)	4.5	43,500	CT0100536	Sep 2023	3
15	Torrington Water Pollution Control Facility	Torrington	4.35	40,865	CT0100579	Oct 2025	0
16	Enfield Water Pollution Control Facility	Enfield	3.97	42,031	CT0100200	Jul 2024	0
17	Branford Water Pollution Control Facility	Branford	3.44	28,176	CT0100048	Jan 2025	0
18	Killingly Water Pollution Control Fac.	Danielson	3.4	21,011	CT0101257	Dec 2022	0
19	Chesire,water Pollution Control Facility	Cheshire	2.51	7,997	CT0100081	Sep 2022	12
20	South Windsor Water Pollution Control Facility	South Windsor	2.51	26,767	CT0100510	May 2030	7
21	Glastonbury Water Pollution Control Facility	Glastonbury	2.5	35,054	CT0100226	Apr 2026	8
22	Shelton Water Pollution Control Facility	Shelton	2.12	41,474	CT0100714	Dec 2025	123
23	Westport WPCF	Westport	1.84	27,128	CT0100684	Jul 2024	0
24	Ansonia Water Pollution Control Facility	Ansonia	1.71	18,815	CT0100013	Nov 2022	8
25	Simsbury Water Pollution Control Facility	Simsbury	1.66	27,536	CT0100919	Feb 2024	2
26	Willimantic WPCF	Willimantic	1.64	24,966	CT0101001	Oct 2023	1
27	East Hampton Water Pollution Control Facility	East Hampton	1.4	26,210	CT0024694	Sep 2025	15
28	Winsted WPCF	Winsted	1.33	10,226	CT0101222	Oct 2021	2
29	University Of Ct Water Pollution Control Facility	Storrs	1.25	2,012	CT0101320	May 2023	3
30	Montville Water Pollution Control Facility	Montville (uncasville)	1.25	18,478	CT0100935	Oct 2024	59
31	Seymour WPCF	Seymour	1.12	19,233	CT0100501	Mar 2026	6
32	Putnam W P C F	Putnam	1.01	9,529	CT0100960	Aug 2022	1
33	Thomaston WPCF	Thomaston	0.92	7,453	CT0100781	Jun 2022	1
34	New Canaan Wastewater Treatment Plant	New Canaan	0.87	20,732	CT0101273	Jan 2026	2
35	Stafford / WPCF	Stafford Springs	0.76	12,619	CT0101214	Sep 2022	3
36	Plainfield North Water Pollution Control Facility	Plainfield	0.55	9,541	CT0100447	May 2022	23
37	Canton WPCF	Canton	0.53	13,007	CT0100072	Apr 2027	3
38	Mystic WPCF	Mystic	0.52	5,341	CT0100544	Aug 2022	10
39	Litchfield WPCF	Bantam	0.46	8,944	CT0100803	Jun 2021	18
40	Portland Water Pollution Control Facility	Portland	0.36	9,462	CT0101150	Oct 2028	10
41	Plainfield Village Sewage Treatment Plant	Plainfield	0.36	5,918	CT0100439	Sep 2022	4
42	Beacon Falls Water Pollution Control Fac	Beacon Falls	0.34	6,033	CT0101061	Apr 2031	207
43	Newtown /wpcf	Newtown	0.34	3,517	CT0101788	Aug 2021	33
44	Town Of Salisbury WPCF	Salisbury	0.31	4,112	CT0100498	Sep 2025	13
45	Canaan Fire District	North Canaan	0.29	1,078	CT0100064	Aug 2024	5
46	Town Of Norfolk WPCF	Norfolk	0.2	1,587	CT0101231	Sep 2025	7
47	Deep River Water Pollution Control Facility	Deep River	0.18	4,663	CT0101745	Nov 2028	20
48	Stonington Borough WPCF	Stonington	0.17	4,406	CT0101281	Aug 2025	18
49	Ledyard Water Pollution Control Facility	Ledyard	0.13	1,509	CT0101681	Jun 2025	4
50	Somers WPCF	Somers	0.05	865	CT0101605	Sep 2025	62

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

Largest plants 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 · 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 Connecticut (2026).” Updated October 26, 2026. https://klarifi.io/facilities/connecticut/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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