The 50 largest wastewater treatment plants in Pennsylvania
Ranked by average flow · 749 MGD combined · 73% of the state's reported flow
Philadelphia Southwest POTW in Philadelphia is the largest publicly owned wastewater treatment plant in Pennsylvania by reported average flow, treating about 182.78 million gallons per day. The 50 plants below treat 749 MGD between them, 73% of the flow reported by all 790 plants in the state, and serve about 2,386,060 people. Every plant links to its profile with permit and compliance data. Treatment technology is shown with a free Klarifi account.
| # | Facility | City | Avg flow (MGD) | Population | NPDES permit | Expires | Violations (3y) |
|---|---|---|---|---|---|---|---|
| 1 | Philadelphia Southwest POTW | Philadelphia | 182.78 | 547,807 | PAL026671 | Dec 2030 | 36 |
| 2 | Northeast WPCP | Philadelphia | 153.22 | 803,306 | PAL026689 | Dec 2030 | 0 |
| 3 | Phila Water Dept - SE STP | Philadelphia | 86 | 268,286 | PAL026662 | Dec 2030 | 1 |
| 4 | City Of Erie, Pa - Wastewater Treatment Plant | Erie | 44.59 | — | PAL026301 | Dec 2030 | 1 |
| 5 | City Of Allentown Wastewater Treatment Plant | Allentown | 31.66 | 108,967 | PA0026000 | Sep 2007 | 0 |
| 6 | Delcora-Western Regional Treatment Plant | Chester | 30.48 | 107,437 | PA0027103 | Mar 2026 | 18 |
| 7 | Reading STP | Reading | 14.02 | — | PA0026549 | Apr 2028 | 9 |
| 8 | City Of Bethlehem Wastewater Treatment Plant | Bethlehem | 10.23 | 130,303 | PA0026042 | May 2031 | 18 |
| 9 | Springettsbury Wastewater Treatment Plant | York | 9.09 | — | PAL026808 | Dec 2030 | 4 |
| 10 | Gr Hazleton Jt Sew Auth WWTP | Hazleton | 6.71 | 25,895 | PA0026921 | Feb 2027 | 6 |
| 11 | Oaks WWTP (lower Perkiomen Valley) | Oaks | 6.7 | — | PA0026964 | Nov 2030 | 5 |
| 12 | Upper Allegheny Jt Sani Auth STP | Creighton | 6.36 | — | PA0027391 | Aug 2015 | 0 |
| 13 | Washington E Washington STP | Washington | 6.15 | — | PA0026212 | Jan 2031 | 169 |
| 14 | Uniontown STP | Uniontown | 6.09 | — | PA0027219 | Jul 2027 | 6 |
| 15 | Lrbsa - Throop Plant | Throop | 5.78 | 24,066 | PA0027090 | Aug 2021 | 5 |
| 16 | Lower Bucks WWTP | Levittown | 5.71 | — | PA0026468 | May 2028 | 25 |
| 17 | Chambersburg Boro STP | Chambersburg | 5.44 | — | PAL026051 | Dec 2030 | 0 |
| 18 | Lebanon City STP | Lebanon | 5.34 | 24,997 | PAL027316 | Dec 2030 | 1 |
| 19 | Williamsport Sanitary Authority - Central Plant | Williamsport | 5.18 | — | PAL027049 | Dec 2030 | 5 |
| 20 | Log College STP | Warminster | 5.03 | 40,585 | PA0026166 | Aug 2026 | 5 |
| 21 | Latrobe Mun Auth STP | Latrobe | 5.03 | — | PA0026069 | Sep 2022 | 46 |
| 22 | Pottstown Wastewater Treatment Plant | Pottstown | 4.98 | — | PAL026786 | Dec 2030 | 16 |
| 23 | Valley Forge Sewer Authority WWTP | Phoenixville | 4.95 | — | PAL043974 | Dec 2030 | 7 |
| 24 | Sharon STP | Sharon | 4.89 | 16,686 | PAL027138 | Dec 2030 | 19 |
| 25 | Norristown Muni STP | Norristown | 4.87 | — | PA0027421 | May 2029 | 2 |
| 26 | New Stanton WPCP | Hunker | 4.84 | — | PA0038181 | Nov 2029 | 6 |
| 27 | Bradford STP | Bradford | 4.79 | — | PA0026379 | Mar 2031 | 23 |
| 28 | Clairton Mun Auth STP | Clairton | 4.78 | — | PAL026824 | Dec 2030 | 18 |
| 29 | Indiana Boro WWTP | Indiana | 4.67 | 26,569 | PA0026751 | Jun 2031 | 0 |
| 30 | Piney Fork STP | Pittsburgh | 4.65 | — | PA0027618 | Jun 2028 | 15 |
| 31 | Altoona Easterly STP | Altoona | 4.58 | — | PA0027014 | Sep 2026 | 4 |
| 32 | Upper Moreland Hatboro Jt Sew Auth/willow Grove | Willow Grove | 4.46 | 54,659 | PAL025976 | Dec 2030 | 20 |
| 33 | E Norriton Plymouth /norristown | Plymouth Meeting | 4.25 | — | PAL026816 | Dec 2030 | 7 |
| 34 | Lower Allen Twp STP | New Cumberland | 4.1 | 14,013 | PAL027189 | Dec 2030 | 0 |
| 35 | Hanover Boro STP | Mcsherrystown | 4 | — | PA0026875 | Dec 2027 | 2 |
| 36 | Allegheny Valley Joint Sewage Authority | Cheswick | 3.88 | — | PAL026255 | Dec 2030 | 34 |
| 37 | Morrisville Borough STP | Morrisville | 3.84 | — | PA0026701 | Feb 2031 | 23 |
| 38 | Dover Twp Water Sys-Admire Booster Cl | Dover | 3.82 | 15,329 | PA0020826 | May 2030 | 5 |
| 39 | Hermitage Muni Auth STP | Hermitage | 3.72 | — | PAL028487 | Dec 2030 | 1 |
| 40 | Johnstown Wastewater Treatment Plant | Johnstown | 3.64 | 78,141 | PAL026034 | Dec 2030 | 10 |
| 41 | Leonard L Nary WWTP @ Montour Run | Coraopolis | 3.49 | — | PA0028801 | Jan 2028 | 8 |
| 42 | Meadville Area STP | Meadville | 3.49 | 13,681 | PA0026271 | Feb 2031 | 4 |
| 43 | University Area Joint Authority/spring Creek Pollution Control Fac. | State College | 3.49 | — | PAL026239 | Dec 2030 | 26 |
| 44 | Kiski Vly Wpca STP | Leechburg | 3.46 | 26,401 | PA0027626 | Jun 2030 | 3 |
| 45 | Ambler Boro Ms4 Ua | Ambler | 3.39 | 5,707 | PAL026603 | Dec 2030 | 25 |
| 46 | Swatara Twp STP | Hummelstown | 3.37 | 36,105 | PA0026735 | Jan 2027 | 2 |
| 47 | West Goshen Township WWTP | West Chester | 3.35 | 17,120 | PAL028584 | Dec 2030 | 2 |
| 48 | Brush Creek STP | Irwin | 3.28 | — | PAL027570 | Dec 2030 | 4 |
| 49 | Upper Gwynedd-Towamencin Mun A | Lansdale | 3.25 | — | PAL039004 | Dec 2030 | 47 |
| 50 | Pennridge Wastewater Treatment Authority WWTP | Sellersville | 3.24 | — | PAL020460 | Dec 2030 | 34 |
Treatment technology for each plant is shown with a free Klarifi account. Create one →
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 October 26, 2026.
Wastewater terms: WWTP · POTW · MGD · NPDES permit · Tertiary treatment · Significant industrial user · 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 Pennsylvania (2026).” Updated October 26, 2026. https://klarifi.io/facilities/pennsylvania/largestNeed a custom cut of the data for a state, a county or a list of plants? Email info@klarifi.io.