What is the largest wastewater treatment plant in Pennsylvania?

Allegheny Cnty Sani Auth/allegheny Cnty in Pittsburgh, treating an average of 152.8 MGD under NPDES permit PAL025984. Phila Water Dept - SE STP in Philadelphia is second at 77 MGD.

How much wastewater do Pennsylvania’s largest plants treat?

The 50 largest plants treat 505 MGD combined, 71% of the flow reported by all 783 publicly owned plants in Pennsylvania.

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 Pennsylvania

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

Ranked by average flow · 505 MGD combined · 71% of the state's reported flow

Allegheny Cnty Sani Auth/allegheny Cnty in Pittsburgh is the largest publicly owned wastewater treatment plant in Pennsylvania by reported average flow, treating about 152.8 million gallons per day. The 50 plants below treat 505 MGD between them, 71% of the flow reported by all 783 plants in the state, and serve about 937,418 people. Every plant links to its profile with permit, technology and compliance data.

All plants in Pennsylvania →The 100 largest US plants →Pennsylvania NPDES permits →

The 50 largest publicly owned wastewater treatment plants in Pennsylvania by average flow (MGD), with population served, NPDES permit, expiry, treatment technology and three-year violation count.
#	Facility	City	Avg flow (MGD)	Population	NPDES permit	Expires	Technology	Violations (3y)
1	Allegheny Cnty Sani Auth/allegheny Cnty	Pittsburgh	152.8	—	PAL025984	Dec 2030	—	1
2	Phila Water Dept - SE STP	Philadelphia	77	268,286	PAL026662	Dec 2030	—	1
3	City Of Allentown Wastewater Treatment Plant	Allentown	31.07	108,967	PA0026000	Sep 2007	Clarifiers, Carrousels / oxidation ditches, Biogas silos, Biogas balloons	0
4	Delcora-Western Regional Treatment Plant	Chester	27.54	107,437	PA0027103	Mar 2026	Clarifiers	18
5	City Of Erie, Pa - Wastewater Treatment Plant	Erie	24.1	—	PAL026301	Dec 2030	Clarifiers	1
6	Wyoming Valley Sani Auth Wilkes Barre	Wilkes Barre	17.3	—	PAL026107	Dec 2030	Clarifiers, Carrousels / oxidation ditches	1
7	Reading STP	Reading	14.09	—	PA0026549	Apr 2028	Clarifiers, Carrousels / oxidation ditches, Biogas silos, Biogas balloons	9
8	City Of Bethlehem Wastewater Treatment Plant	Bethlehem	9.97	130,303	PA0026042	May 2031	Clarifiers, Biogas silos, Biogas balloons	18
9	Springettsbury Wastewater Treatment Plant	York	7.61	—	PAL026808	Dec 2030	Clarifiers, Aerated lagoons, Biogas silos	4
10	Lrbsa - Throop Plant	Throop	5.7	24,066	PA0027090	Aug 2021	Clarifiers, Biogas balloons	6
11	Oaks WWTP (lower Perkiomen Valley)	Oaks	5.54	—	PA0026964	Nov 2030	Clarifiers, Biogas silos	5
12	Lower Bucks WWTP	Levittown	5.34	—	PA0026468	May 2028	Clarifiers, Biogas silos	25
13	Lebanon City STP	Lebanon	5.22	24,997	PAL027316	Dec 2030	Clarifiers, Biogas silos, Biogas balloons	1
14	Chambersburg Boro STP	Chambersburg	5.16	—	PAL026051	Dec 2030	Clarifiers, Biogas silos	0
15	Gr Hazleton Jt Sew Auth WWTP	Hazleton	5.15	25,895	PA0026921	Feb 2027	Clarifiers, Biogas silos	6
16	Valley Forge Sewer Authority WWTP	Phoenixville	4.66	—	PAL043974	Dec 2030	Clarifiers, Biogas silos	8
17	Washington E Washington STP	Washington	4.51	—	PA0026212	Jan 2031	Clarifiers, Biogas silos	174
18	Lower Allen Twp STP	New Cumberland	4.33	14,013	PAL027189	Dec 2030	Clarifiers, Biogas silos, Biogas balloons	0
19	Upper Allegheny Jt Sani Auth STP	Creighton	4.3	—	PA0027391	Aug 2015	—	0
20	Uniontown STP	Uniontown	4.2	—	PA0027219	Jul 2027	Clarifiers, Biogas silos	6
21	Norristown Muni STP	Norristown	3.96	—	PA0027421	May 2029	Clarifiers, Biogas silos	2
22	Log College STP	Warminster	3.78	40,585	PA0026166	Aug 2026	Clarifiers, Biogas silos	7
23	Upper Moreland Hatboro Jt Sew Auth/willow Grove	Willow Grove	3.68	54,659	PAL025976	Dec 2030	Biogas silos	20
24	Hanover Boro STP	Mcsherrystown	3.65	—	PA0026875	Dec 2027	Clarifiers, Carrousels / oxidation ditches, Biogas silos	2
25	E Norriton Plymouth /norristown	Plymouth Meeting	3.6	—	PAL026816	Dec 2030	Clarifiers, Biogas silos	7
26	Indiana Boro WWTP	Indiana	3.43	26,569	PA0026751	Jun 2031	Clarifiers, Uncovered lagoons, Biogas silos	0
27	Clairton Mun Auth STP	Clairton	3.42	—	PAL026824	Dec 2030	Uncovered lagoons, Biogas balloons	19
28	Pottstown Wastewater Treatment Plant	Pottstown	3.34	—	PAL026786	Dec 2030	Clarifiers	16
29	Piney Fork STP	Pittsburgh	3.22	—	PA0027618	Jun 2028	Clarifiers, Biogas balloons	15
30	Morrisville Borough STP	Morrisville	3.21	—	PA0026701	Feb 2031	Clarifiers	23
31	New Stanton WPCP	Hunker	3.14	—	PA0038181	Nov 2029	Clarifiers, Biogas silos	6
32	West Goshen Township WWTP	West Chester	3.12	17,120	PAL028584	Dec 2030	Clarifiers, Aerated lagoons, Biogas silos	2
33	Latrobe Mun Auth STP	Latrobe	3.1	—	PA0026069	Sep 2022	Clarifiers	46
34	Williamsport Sanitary Authority - Central Plant	Williamsport	3.06	—	PAL027057	Dec 2030	Clarifiers, Biogas silos	6
35	Swatara Twp STP	Hummelstown	2.91	36,105	PA0026735	Jan 2027	Clarifiers, Biogas silos	2
36	Sharon STP	Sharon	2.89	16,686	PAL027138	Dec 2030	Clarifiers, Biogas balloons	23
37	Upper Gwynedd-Towamencin Mun A	Lansdale	2.85	—	PAL039004	Dec 2030	Clarifiers	47
38	Altoona Easterly STP	Altoona	2.82	—	PA0027014	Sep 2026	Clarifiers, Uncovered lagoons	5
39	University Area Joint Authority/spring Creek Pollution Control Fac.	State College	2.82	—	PAL026239	Dec 2030	Clarifiers	28
40	Hampden Twp Roth Lane STP	Mechanicsburg	2.79	—	PAL080314	Dec 2030	Clarifiers	6
41	Lititz Boro-Well #5 House	Lititz	2.78	—	PAL020320	Dec 2030	Clarifiers, Biogas silos	2
42	Matsunk STP	King Of Prussia	2.57	—	PA0026085	Jun 2029	Clarifiers	1
43	Leonard L Nary WWTP @ Montour Run	Coraopolis	2.56	—	PA0028801	Jan 2028	Clarifiers, Biogas silos	8
44	Dover Twp Water Sys-Admire Booster Cl	Dover	2.51	15,329	PA0020826	May 2030	—	5
45	Hermitage Muni Auth STP	Hermitage	2.42	—	PAL028487	Dec 2030	Uncovered lagoons, Biogas balloons	1
46	Allegheny Valley Joint Sewage Authority	Cheswick	2.41	—	PAL026255	Dec 2030	Clarifiers, Biogas silos	34
47	Bradford STP	Bradford	2.4	—	PA0026379	Mar 2031	—	23
48	Brush Creek STP	Irwin	2.4	—	PAL027570	Dec 2030	Clarifiers, Biogas balloons	4
49	Shippensburg STP	Shippensburg	2.35	—	PA0030643	Aug 2028	Clarifiers, Uncovered lagoons	2
50	Kiski Vly Wpca STP	Leechburg	2.33	26,401	PA0027626	Jun 2030	—	3

Largest plants in Pennsylvania: 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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