PerformanceanalysisoftheRichlandChamberstreatmentw

EcologicalEngineering37(2011)176–190ContentslistsavailableatScienceDirectEcologicalEngineeringjournalhomepage:∗,JamesS.Baysb,LorettaE.Mokryc,DarrelAndrewsd,MarkR.ErnstdaWetlandManagementServices,6995WestbourneDrive,Chelsea,MI48118,USAbCH2MHILL,4350W.CypressSt.,Tampa,FL33607,USAcAlanPlummerAssociates,Inc.,1320SUniversityDr.,FortWorth,TX76107,USAdTarrantRegionalWaterDistrict,P.O.Box4508,FortWorth,TX76106,USAarticleinfoArticlehistory:Received9February2010Receivedinrevisedform14September2010Accepted19September2010Availableonline30November2010Keywords:TreatmentwetlandsTSSNitrogenPhosphorusHydrologyWildlifeabstractTheTarrantRegionalWaterDistrict(TRWD)issupplementingtheflowstoRichland-ChambersReservoir,tomeetfuturewatersupplyneedsofDallas-Ft.Worth,TX.TheTrinityRiveristhenewsource,butqualityisnotadequate.TRWDhasconstructedandinvestigatedtreatmentwetlandfacilitieslocatednearthereservoirtoupgraderiverwaterquality,fromaneight-yearstudyata0.72hapilotsite,andafive-yearstudyata102hafield-scalesite.Bothsystemshadasedimentationbasinfollowedbywetlandcellsinseries.Thepilothadtwobasinsfeedingthreetrainsofthreewetlandcellseach,whilethefield-scalesystemhadonebasinfollowedbyfourwetlandcellsinseries.Waterdepthswereabout30cmforthepilot,and40cmforthefield-scale.Designnominaldetentiontimeswereroughly5and9daysforpilotbasinsandwetlandtrains;and1.5and8daysforthefield-scale.Thesystemsranyear-round,suppliedwithwaterpumpedfromtheriver,whichattimeswaspredominantlytreatedwastewaterfromtheDallas-FortWorthmetroplex.Theprimarytargetcontaminantsweresuspendedsolids,nitrogen,andphosphorus.Nitrogenformsinpumpedflowsfromtheriverweredominatedbyoxidizednitrogen,whichwasmostlynitratenitrogen.Pilotnitrateremovalfromtheriverwaterwas92%,and61%forphosphorus,whilesedimentremovalwas97%.Field-scalenitrateremovalfromtheriverwaterwas77%,and45%forphosphorus,whilesedimentremovalwas96%.Thefield-scaleprojectislocatedonlandownedbytheTexasParksandWildlifeDepartment,andtheyparticipateinmanagementofthewetlandsforthesecondarypurposeofwildlifehabitat.©2010ElsevierB.V.Allrightsreserved.1.IntroductionAssuringadequatesuppliesofpotablewaterisamatterofincreasingconcernforlargemetropolitanareasintheUnitedStates.TheTarrantRegionalWaterDistrict(TRWD)istaskedwithmeetingtheneedsofthe1.7millionresidentsinthewesternpor-tionoftheDallas-FortWorth,Texasmetroplex.Tomeettherawwatersupplyneeds,theDistricthasconstructedandoperatesfourmajorsurfacewaterreservoirs.Waterdemandsareexpectedtoincreasebyabout35%by2050.Inordertomeetfuturewatersupplyrequirements,TRWDispursuingseveraloptionsincludingdivertingTrinityRiverwaterintotwooftheDistrict’sreservoirslocated100kmdownstreamofDallas-FortWorth.However,priortoaddingTrinityRiverwatertothereservoirs,thequalitymustbeimproved,toatleastmatchthatofexistingtributariestothereser-voirs.DuringperiodswhentheTrinitybasinreceiveslittlerainfall,theriverflowisgreaterthan95%secondarilytreatedoutflowfrom∗Correspondingauthor.Tel.:[phone].E-mailaddress:[e-mail](R.H.Kadlec).themetroplex.Conventionalwatertreatmentsystemswereeval-uated,butTRWDconcludedthataconstructedwetlandsystemwouldprovideanappropriateleveloftreatmentforthelargeflowsrequired,andwouldcostlessthanconstructinganewwatersupplyreservoir.Constructedtreatmentwetlandshavebeeninvestigatedovertheperiod1992topresent,withthegoalofdevelopingdesignguidelinesandgainingconstructionandoperationalexperience.Thefirststudyspannedmorethaneightyears,andinvolvedtheoperationofapilotsystem,whichreceivedpumpedTrinityRiverwater(Andrewsetal.,1994;APAI,1995,1996,2002).Thesecondstudyconsideredascaled-upsystem(100×),whichalsoreceivedpumpedTrinityRiverwater.Thatstudyisongoing,withresultsfromthefirstfiveyearsunderconsiderationhere.Eachofthepri-marywaterqualityparametersofconcern,totalsuspendedsolids(TSS),totalnitrogen(TN),andtotalphosphorus(TP)wereevalu-atedrelativetoriverwaterqualityduringpumping.ThemedianconcentrationforTP,theprimaryconstituentofconcern,wasover1.0mg/Lforthe0to60m3/sflowrange(i.e.,lowflowor“baseflow”)intheTrinityRiver.Thesimulatedrequiredpumping,neededtoaugmentreservoirsupplies,willrangefromzero(16%ofthetime)toamaximumof5.0m3/s.0925-8574/$–seefrontmatter©2010ElsevierB.V.Allrightsreserved.doi:10.1016/j.ecoleng.2010.09.003R.H.Kadlecetal./EcologicalEngineering37(2011)176–190177SB1SB23W1W2W3W4W5W6W7W8W9RiverSBWC1WC2WC3WC4RiverFig.1.Layoutschematicofthepilotsystem(upperpanel)andfieldscalesystem(lowerpanel).Thefield-scaleconstructedwetlandprojectinvolvedawork-ingpartnershipbetweentheDistrictandtheTexasParksandWildlifeDepartment(TPWD).The100-hafield-scaleprojectisconstructedonTPWDpropertyunderaMemorandumofUnder-standingbetweentheDistrictandTPWD(Frossardetal.,2006).ThewetlandsarelocatedwithintheRichlandCreekWildlifeManage-mentArea(RCWMA)whichwascreatedtocompensateforhabitatlossesassociatedwiththeconstructionofRichland-ChambersReservoir.TheRCWMAisownedbyTPWDandmanagedtoprovidequalityconsumptiveandnon-consumptivepublicuse