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World wastewater treatment plant observatory · data as reported by each inventory

Wastewater treatment plants in United States · Washington

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262 inventory records · EPA Clean Watersheds Needs Survey 2022

Data years: 2022. The inventory date does not establish current operation.

262 results

CompareNameNative sizeYear
WEST POINT WWTPSeattle215 MGD (million gallons per day)2022
King County South Treatment PlantRenton122 MGD (million gallons per day)2022
TACOMA CENTRAL STP #1Tacoma60 MGD (million gallons per day)2022
Spokane Riverside Park POTWSpokane51 MGD (million gallons per day)2022
Brightwater Treatment PlantWoodinville40.9 MGD (million gallons per day)2022
Westside Treatment FacilityVancouver31.46 MGD (million gallons per day)2022
Everett WWTPEverett31.3 MGD (million gallons per day)2022
BELLINGHAM POST POINT TPBellingham30 MGD (million gallons per day)2022
Cowlitz Water Pollution Control PlaLongview26 MGD (million gallons per day)2022
Yakima Regional POTWYakima21.5 MGD (million gallons per day)2022
CHAMBERS CREEKUniversity Place18 MGD (million gallons per day)2022
Budd Inlet Treatment PlantOlympia17 MGD (million gallons per day)2022
Marine Park WWTFVancouver16.1 MGD (million gallons per day)2022
SALMON CREEK STPVancouver14.95 MGD (million gallons per day)2022
MARYSVILLE LAGOONMarysville13.3 MGD (million gallons per day)2022
EDMONDS STPEdmonds11.8 MGD (million gallons per day)2022
RICHLAND STPRichland11.4 MGD (million gallons per day)2022
Bremerton West Plant STPBremerton10.1 MGD (million gallons per day)2022
LAKOTA STPFederal Way10 MGD (million gallons per day)2022
WALLA WALLA STPWalla Walla9.6 MGD (million gallons per day)2022
KENNEWICK POTWKennewick9.3 MGD (million gallons per day)2022
MIDWAY SEWER DISTRICT WWTPKent9 MGD (million gallons per day)2022
Spokane County Regional WWTPSpokane7.68 MGD (million gallons per day)2022
OTHELLO SEWAGE LAGOONSOthello7.5 MGD (million gallons per day)2022
LYNNWOOD TREATMENT SYSTEMEdmonds7.4 MGD (million gallons per day)2022
MILLER CREEK STPNormandy Park7.1 MGD (million gallons per day)2022
TACOMA #3 STP NORTHTacoma7.1 MGD (million gallons per day)2022
SALMON CREEK STP #1Burien6.88 MGD (million gallons per day)2022
PASCO STPPasco6.5 MGD (million gallons per day)2022
Camas Wastewater Treatment PlantCamas6.1 MGD (million gallons per day)2022
MOUNT VERNON TREATMENTMount Vernon6.037 MGD (million gallons per day)2022
CHEHALIS STPChehalis6 MGD (million gallons per day)2022
CENT. KITSAP REG. STPPoulsbo6 MGD (million gallons per day)2022
REDONDO STPRedondo5.6 MGD (million gallons per day)2022
WENATCHEE POTWWenatchee5.5 MGD (million gallons per day)2022
ANACORTES STPAnacortes4.5 MGD (million gallons per day)2022
ABERDEEN STPAberdeen4.485 MGD (million gallons per day)2022
LAKE STEVENS STPEverett4.32 MGD (million gallons per day)2022
PULLMAN STPPullman4.2 MGD (million gallons per day)2022
Puyallup WWTP (EPA)Puyallup4.06 MGD (million gallons per day)2022
HOQUIAM WASTEWATER TREATMENT PLANTHoquiam4 MGD (million gallons per day)2022
Sand Dunes WWTPMoses Lake4 MGD (million gallons per day)2022
ELLENSBURG STPEllensburg3.85 MGD (million gallons per day)2022
EAST WENATCHEE STPEast Wenatchee3.8 MGD (million gallons per day)2022
BURLINGTON TREATMENTBurlington3.79 MGD (million gallons per day)2022
Upper Kittitas County Regional WWTFCle Elum3.6 MGD (million gallons per day)2022
GRANDVIEW STPGrandview3 MGD (million gallons per day)2022
MONROE STPMonroe2.84 MGD (million gallons per day)2022
Snohomish Wastewater SystemSnohomish2.8 MGD (million gallons per day)2022
SUNNYSIDE POTWSunnyside2.8 MGD (million gallons per day)2022
CENTRALIA STPCentralia2.7 MGD (million gallons per day)2022
FERNDALE STPFerndale2.7 MGD (million gallons per day)2022
CHENEY S/T FACILITYCheney2.7 MGD (million gallons per day)2022
Chelan City of POTWChelan2.64 MGD (million gallons per day)2022
SUMNER STPSumner2.62 MGD (million gallons per day)2022
Big Gulch WWTPMukilteo2.61 MGD (million gallons per day)2022
OAK HARBOR STPOak Harbor2.5 MGD (million gallons per day)2022
PORT ANGELES WWTPPort Angeles2.5 MGD (million gallons per day)2022
GIG HARBOR STPGig Harbor2.38 MGD (million gallons per day)2022
WASHOUGAL S/T FACILITYWashougal2.24 MGD (million gallons per day)2022
CLARKSTON STPClarkston2.2 MGD (million gallons per day)2022
ARLINGTON TREATMENTArlington2.02 MGD (million gallons per day)2022
SELAH S/T FACILITYSelah2 MGD (million gallons per day)2022
LIBERTY LAKE STPLiberty Lake2 MGD (million gallons per day)2022
Martin Way Reclaimed Water PlantLacey2 MGD (million gallons per day)2022
OCEAN SHORES STPOcean Shores1.96 MGD (million gallons per day)2022
South Kitsap Water Reclamation FacilityPort Orchard1.93 MGD (million gallons per day)2022
MEDICAL LAKE STPMedical Lake1.85 MGD (million gallons per day)2022
PROSSER WWTPProsser1.8 MGD (million gallons per day)2022
SEDRO WOOLLEY TREATMENTSedro Woolley1.759 MGD (million gallons per day)2022
SEQUIM STPSequim1.67 MGD (million gallons per day)2022
COLLEGE PLACE WWTPCollege Place1.65 MGD (million gallons per day)2022
STANWOOD S/T FACILITYStanwood1.5 MGD (million gallons per day)2022
WEST RICHLAND POTWWest Richland1.5 MGD (million gallons per day)2022
ENUMCLAW WWTPEnumclaw1.48 MGD (million gallons per day)2022
COLVILLE STPColville1.45 MGD (million gallons per day)2022
PORT TOWNSEND STPPort Townsend1.44 MGD (million gallons per day)2022
BIRCH BAY STPBlaine1.44 MGD (million gallons per day)2022
TOPPENISH TREATMENTToppenish1.35 MGD (million gallons per day)2022
Duvall WWTPDuvall1.3 MGD (million gallons per day)2022
CHEWELAH S/T FACILITYChewelah1.2 MGD (million gallons per day)2022
ORTING S/T FACILITYOrting1.2 MGD (million gallons per day)2022
SHELTON STPShelton1.2 MGD (million gallons per day)2022
WAPATO STPWapato1.1 MGD (million gallons per day)2022
CASHMERE STP FACILITYCashmere1.1 MGD (million gallons per day)2022
Yelm Wastewater Treat and ReclaimYelm1.06 MGD (million gallons per day)2022
ILWACO WASTEWATER TREATMENT PLANTIlwaco1.01 MGD (million gallons per day)2022
OMAK STPOmak1.01 MGD (million gallons per day)2022
Cascadia Water Treatment PlantBonney Lake1 MGD (million gallons per day)2022
Buckley WWTFBuckley1 MGD (million gallons per day)2022
WINLOCK STPWinlock1 MGD (million gallons per day)2022
Airway Heights WWTPAirway Heights1 MGD (million gallons per day)2022
GRANITE FALLS STPGranite Falls0.865 MGD (million gallons per day)2022
Leavenworth City of POTWLeavenworth0.84 MGD (million gallons per day)2022
Castle Rock WWTPCastle Rock0.8 MGD (million gallons per day)2022
Kalama Wastewater Treatment PlantKalama0.8 MGD (million gallons per day)2022
Long Beach WWTPLong Beach0.791 MGD (million gallons per day)2022
PE ELL STPPe Ell0.79 MGD (million gallons per day)2022
DAYTON STPDayton0.75 MGD (million gallons per day)2022
MOSES LAKE STPMoses Lake0.75 MGD (million gallons per day)2022

Regulatory context

General reference. This is not an exhaustive review of applicable law.

United States: Clean Water Act / NPDES

NPDES regulates pollutant discharges from point sources to waters of the United States. The permit sets limits and monitoring conditions. A CWNS code identifies an inventory record, not an NPDES permit.

  • Permit identifier and permitting authority: EPA or an authorized state.
  • Outfall and receiving water; sewer connections follow a different control route.
  • Current permit conditions, limits and dated measurements; these are not included in CWNS.

References reviewed: 2026-11-06. Individual applicability: undetermined. This profile does not establish authorization or compliance.