FINALREPORT
EvaluationofWaterQualityDataChesterWaterDepartment,ChesterMA
Preparedby:
RichardW.Gullick,PhDRCAPSolutions,Inc.
June27,2019TableofContents:
1. IntroductionandObjectives2. TreatmentSystem3. Methodology4. DrinkingWaterProduction5. Filtration6. PrimaryDisinfection7. SecondaryDisinfection(DistributionSystemChlorineResidual)8. pH9. DisinfectionByproducts10. Color11. LeadandCopper12. SummaryandConclusions13. Recommendations
1.IntroductionandObjectives:TheChesterWaterDepartmentoperatesacommunitywatersupplysystem(PWSID1059000)thatservesapproximately750peoplethroughapproximately252connectionsinthissmalltownlocatedinwesternMassachusetts.ThewatersystemrecentlyexceededtheallowableMaximumContaminantLevel(MCL)forthedisinfectionbyproduct(DBP)classknownastotaltrihalomethanes(TTHMs)forthreequartersinarow–thethirdandfourthquarterof2018andthefirstquarterof2019.TheMassachusettsDepartmentofEnvironmentalProtection(MassDEP)issuedaNoticeofNoncompliance(EnforcementNumber00005564)toChesteronDecember4,2018forthethirdquarter2018TTHMMCLexceedance,andaNoticeofNoncompliance(EnforcementNumber00006424)toChesteronMay3,2019forthefourth
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quarter2018andfirstquarter2019TTHMMCLexceedances.ChesterwasalsorequiredtocompleteandsubmitanOperationalEvaluationReportforexceedingtheOperationalEvaluationLevel(OEL)limitforTTHMinthesecondandthirdquartersof2018(perMassDEPletterdatedDecember4,2018).Inaddition,inaletterdatedAugust24,2018,MassDEPrequiredChesterto“prepareawrittenreporttoaddressthe2018color,turbidity,sourcewaterquality,anddisinfectionbyproductconcerns.”Thisreportpresentsthefindings,conclusions,andrecommendationsfromanevaluationofavailablewaterqualitydata,andisintendedtohelpsatisfytheaboveMassDEPrequirements.Thisevaluationincludesthewaterqualityparameterslistedabove,aswellasobservationsandrecommendationsrelatedtootheroperationaltopics.2.TreatmentSystem:Chester’swatertreatmentsystemiscomprisedmainlyofthefollowing,intheorderpresented:
1. PresentlythesourcewaterisfromHornPond,withtheAustinBrookReservoirservingasanalternatebackupsupply.
2. Slowsandfiltration–threeslowsandfiltersareavailable,andoneincludesalayerofgranularactivatedcarbonforremovingnaturalorganicmatter(NOM),whichisaprecursortoDBPformation.
3. Disinfectionwithfreechlorine–thisisaccomplishedinthethirdsegmentoftheclearwell(thewholeclearwellisavoidedtoreducechlorinecontacttimeandthusreduceDBPformation).
4. pHadjustmentusingsodiumhydroxide(NaOH),injectedjustaftertheclearwellandbeforethewaterleavesthetreatmentplant.
5. Disinfectionwithfreechlorine–thissecondstageofprimarydisinfectionisaccomplishedinthe~1,800-footpipelineleadingfromthetreatmentplantdownthehilltotheoldchlorinatorbuilding.ChorineisaddedatthetreatmentplantjustaftertheNaOHaddition,andtheresidualismeasuredattheoldchlorinatorbuilding.Enoughchlorineresidualistargetedtomaintainaresidualinthedistributionsystem(i.e.,secondarydisinfection).Forchlorinedisinfection,thepipelinehastheadvantageofahigherbafflingfactorthantheclearwell(1.0versus0.13,respectively),butthedisadvantageofahigherpH.
6. TheoldchlorinatorbuildingisconsideredtobethePointofEntry(POE)tothedistributionsystem.FinishedwaterturbidityandpHarealsomeasuredattheoldchlorinatorbuilding.
3.Methodology:Availablewaterproductionandwaterqualitydatawerereviewedforcalendaryear2018.MostofthedatawereobtainedfromtheMonthlyOperatingReports(MORs)thataresubmittedtotheMassDEP.TheMORswereobtainedfromtheChesterWaterDepartment.Flowandwaterqualitydatawereplottedtoidentifytrends,variousdatasetswerecomparedtoidentifypotentialcorrelations,andresultswerecomparedtothecorrespondingregulatoryrequirements(e.g.,MCLs)orotherwaterqualitytargets.Inaddition,adistributionsystemchlorineresidualmappingexercisewasconductedonMarch27,2019.
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4.DrinkingWaterProduction:Thequantityofpotablewaterproducedeachdayin2018ispresentedinFigure1.ThereportedpeakhourlyflowsforeachdayarepresentedinFigure2.
Figure1.Potablewaterproducedperday(1/1/18–12/31/18)
Figure2.PeakHourlyFlowforeachday(1/1/18–12/31/18)
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Thefollowingobservationsareevidentfromthewaterproductiondata:
• In2018,dailyflowsaveraged45,691gpd.Thehighestdailyflowwas109,328gpd,andthelowestdailyflowwas32,672gpd.
• Assumingapopulationsizeof750people,theaverageproductioncorrespondsto61gpdperperson,whichisveryclosetothenationalaverageof58.6gallonspercapitaperdayforresidentialcommunities(DeOreoetal.,2016).
• In2018,peakhourlyflowsaveraged49gpm.Thehighestpeakhourlyflowwas129gpm,andthelowestpeakhourlyflowwas32gpm.
• Theratioofaveragepeakhourlyflowtoannualaverageflowis1.5(49gpmvs.31.7gpm).• Thereweresomeperiodsofabnormallyhighflow,includinglateJanuary–earlyFebruary,and
againinOctoberandthenNovember(Figure1).Theselargeincreasesinwaterproductionappearattributabletoleakingpipesthatwerediscoveredandrepaired.Forexample,theJanuary/FebruaryissuewasapipebreakonEmeryStreetthatfilledabasement.
• Chesterusesthemeasuredvalueofpeakhourlyflowfordeterminingdisinfectionperformance,insteadofthealternatemethodofassumingavalueforpeakhourlyflowbasedontheaverageannualflowandapeakingfactor.Atypicalpeakingfactorusedis3.0,whileChester’smeasuredpeakingfactorisonly1.5.ItisrecommendedthatChestercontinuetousethemeasuredpeakhourlyflowinsteadofusingthealternatepeakingfactormethod,asinthiscasethatwouldtypicallyresultinlessdisinfectionbeingrequiredthanviathepeakingfactorapproach.Thiswouldbedisadvantageousonlyincircumstanceswherethereisanabnormalamountofflow,suchasduringamainbreak.
• Nounresolvedissueswereidentifiedregardingthewaterproductiondata.5.Filtration:TheChesterWaterDepartmentusesslowsandfiltrationaspartofthetreatmentsystem.Therearethreefilters,oneofwhich(Filter#3)hasagranularactivatedcarbon(GAC)layerbetweentwosandlayers(a“carbonsandwich”)forremovingnaturalorganicmatter(NOM),whichisaprecursortoDBPformation.Anywherefromonetothreefiltersmaybeoperatingatagiventime,dependingonflowrequirementsandimpactsfromfilterheadloss.DuringtheMarch27,2019sitevisit,Filter#2wastheonlyfilterinoperation.Turbidityhasbeenmonitoredforthefinishedwater,butnotforthecombinedfiltereffluent.TheturbiditymeteriscalibratedtwiceperyearbythesystemOperator(typicallyaroundJune1andduringtheDecemberholidays).
Forslowsandfiltration,theregulatoryrequirementsincludethefollowingtwoconditions(per310CMR22.20A(4)(b):
1. Atleast95%oftheCombinedFilterEffluent(CFE)turbidityreadingsinagivencalendarmonthmustbe≤1NTU(Nephelometricturbidityunit).Giventhatonlyonesignificantdigitisusedforthatlimit,thedatashouldalsoberoundedtoonesignificantdigit.Thismeansthatavalueof1.49NTUwouldberoundeddownto1NTU,andthatwouldmeetthelimit.Avalueof1.50NTUwouldberoundedupto2NTU,andthatwouldexceedtheallowablelimit.
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2. AtnotimecantheCombinedFilterEffluentturbiditybeabove5NTU(thusallowingupto5.49NTU,butnot5.50NTU).
Thefinishedwaterturbidityfor2018isplottedinFigure3(resultswerenotavailablefortheCombinedFilterEffluent).Thefollowingobservationsweremaderegardingthefiltrationoperations:
Figure3.FinishedWaterTurbidity
• Therequiredturbiditylimitsweremetthroughout2018.Theaveragedailyvaluefor2018was0.11NTU,andthehighestdailyvaluewas0.29NTU.Assuch,therewerenoresultsneareitherthe95%limitof≤1NTUnortheabsolutelimitof≤5NTU.
• Chesterhasbeencollectingthesamplesfortheturbidityanalysesfromthetreatmentplantfinishedwater(PointofEntry,orPOE).However,theproperlocationforsamplingturbidityforregulatorycomplianceisthecombinedfiltereffluentwater,beforeanyfurthertreatmentorchemicaladdition(referredtoas“filteredwater”in310CMR22.20A(4)(b)).Typically,filtereffluentturbiditiesarelowerthanfinishedwaterturbidities.RaisingthepHofthewatercancausedissolvedmetalstoprecipitateandthusincreasetheturbidity.Thefiltereffluentturbidityvaluesshouldbeusedforregulatorycompliancereporting,andforassessingtheoperationoftheslowsandfilters.
Chester’sOperatorreportedthattypicallythefiltereffluentturbiditiesarearound0.03to0.04NTU,asopposedtotheaveragedailyfinishedwaterturbidityof0.11NTU.WhencheckedonMarch27,2019,thefilteredwaterturbiditywas0.02NTUandthefinishedwaterturbiditywas0.09NTU.
• Chestershouldinstallsampletapsforallthreeindividualfiltereffluents(IFEs)andalsotheonecombinedfiltereffluent(CFE).ThereshouldbeanonlineturbiditymeterfortheCFEsample,andthatwouldbeusedfordeterminingthemaximumturbidityvalueforeachday.
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• TherewasanincreaseinfinishedwaterturbidityinAugust2018,andthenasecondspikeoccurredforalittleoveraweekinSept2018.However,themaximumturbiditywas0.29NTU,whichiswellbelowtheregulatorylimit=.Therefore,whiletheseturbidityincreasesarenotableforoperationalpurposes,thereisnoconcernrelatedtotheregulatoryrequirementsforturbidity.Thesystemoperatordoesnotbelievethatsourcewaterqualitywasacauseoftheincreasesinturbidity,andwonderedifafilterwasperhapsbroughtonlinepriortoitbeingcompletelyripened.
Theturbiditydatashowthefollowing(Figure3):• TurbiditystartedtoincreaseonJuly31,2018,reachedamaximumonAugust16-
17,2018,andthenstarteddecreasinguntilitreachednormallevelsaroundtheendofAugust2018.
• TurbiditystartedincreasingagainonSeptember6,2018,reachingamaximumonSeptember15,andwasthenbackdowntonormalbyaboutOctober1.
AnexcerptoftheOperator’slogbookforthattimeperiodisprovidedasFigure4.Itispossiblethatthefirstturbidityspikeiscorrelated,atleastinpart,toFilter#3beingtakenoffline.ThesecondspikestartsnotlongbeforeFilter#1wastakenofflinetodrainforcleaning,andpeakedonSeptember15,onlytwodaysbeforeFilter#1camebackonlineonSept.17.
Inthefuture,anyincreaseinturbidityshouldbeinvestigatedatthetimeitoccurs.ItisnotreadilyevidentfromtheOperator’sLogwhichfiltersareonlineatagiventime,thoughitappearsthatallthreewereonlinepriortothefirstturbidityspikethatstartedonJuly31,2018.Itmaybehelpfultotracksomewhatdifferentlywhichfiltersareonline.Figure5providesasampletemplateforatabletodothat,whichwouldmakeitsomewhateasierinthefuturetotryandcorrelatefilteroperationswithturbidityspikes.
Figure4.ExcerptfromOperator’sLogbook
Day Date Filter#1 Filter#2 Filter#3
?? ?? ONLINE ONLINE ONLINE
?? ?? takenOFFLINEat9:15am;drainingforcleaning
?? ?? PutbackONLINEat11:30am
?? ?? takenOFFLINEat9:15am;drainingforcleaning
?? ?? PutbackONLINEat9:30am
Figure5.SampleFilterOperationsLog
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6.PrimaryDisinfection:TheChesterWaterDepartmentusesfreechlorineforbothprimaryandsecondary(residual)disinfection.TheregulatoryrequirementsforprimarydisinfectionforthiswatersystemarebasedontheabilitytoinactivateGiardiacysts,andrequiresaminimumof1.0-logremoval(1.0log=90%removal,and2.0logs=99%removal).ThatremovalisafunctionofthepHandtemperatureofthewater,chlorineresidualconcentration,andchlorinecontacttime.Chester’streatmentplantusestwochlorinecontactchambersformeetingthedisinfectionrequirements.Thetargetchlorineresidualsareabout0.4to0.8mg/L.Therearetablesavailableinthetreatmentplantthatprovidesuggestedchlorineresidualsforavarietyofoperatingconditions(e.g.,differenttemperaturesandpH).NoattemptwasmadebyRCAPtoverifytheaccuracyofthatinformation.Thefinishedwaterchlorineresidualsfor2018areplottedinFigure6.
Figure6.FinishedWaterChlorineResidual
Thefollowingobservationsweremaderegardingthechemicaldisinfectionoperations:
• Therequireddisinfectionperformancewasmetatalltimesin2018.• Chlorineresidualsvarymorethanisdesiredformaintainingaconsistentwaterquality.Arange
of+/-0.2mg/Lor+/-0.3fromthetargetconcentrationwouldbeareasonablegoal.ItisrecommendedthatChesterinvestigatehowtomaintainamoreconsistentfinishedwaterchlorineresidual.
• Finishedwaterchlorineresidualwasconstantat0.3mg/LfromJuly11toAugust31,2018.ThesystemOperatorwasnotabletoprovideanexplanationforthisanomaly.
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• RCAP’scalculationoftheachieveddisinfectionperformancecalculationsconfirmedthatChesteriscalculatingdisinfectionperformanceaccurately(withinreasonablevariancesforroundingdifferences).However,thepartofthecalculationinvolvingthevolumeofthechlorinecontactorwasnotchecked.RCAPwasnotabletoobtainthespecificationsusedintheSCADAcalculationstodeterminethevolumeofthechlorinecontactors(partofdeterminingchlorinecontacttime),andthuscouldnotconfirmthisaccuracy.Itisrecommendedthatthisinformationbeobtainedandreviewedforaccuracy.
• Abafflingfactorof0.13isusedforthechlorinecontactchamber.ThesystemOperatornotesthatthiswasdeterminedviaatracerstudyconductedwithassistancefromtheMassachusettsRuralWaterAssociationandalsoMikeMcGrathofMassDEP.Nodocumentationofthistracerstudywasavailable.Thetracerstudyreportshouldbelocatedandfiled,andalsoperhapsbesubjecttoareview.RCAPSolutionsisavailabletoconductthatreviewifsodesiredbytheChesterWaterDepartment.
7.SecondaryDisinfection(DistributionSystemChlorineResidual):Secondary(residual)disinfectioninvolvesmaintainingadetectablechlorineresidualinthedistributionsystem.ThisismonitoredviathechlorineresidualanalysesconductedwhensamplingmonthlyforcoliformbacteriaaspartoftheRevisedTotalColiformRule(RTCR)monitoringprogram.Whiletheregulatoryrequirementisfora“detectable”chlorineresidual,ideallychlorineresidualsconcentrationsshouldbe≥0.2mg/Lthroughoutadistributionsystem.FortheChesterdistributionsystem,chlorineresidualiscurrentlymonitoredat381HuntingtonRoad,whichisneartheendofadead-endpipeinthesoutheasternpartofthedistributionsystem.The2018distributionsystemchlorineresidualsat381HuntingtonRoadareplottedinFigure7.
Figure7.DistributionSystemChlorineResidual
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Basedonthosedata,thefollowingobservationsweremade:
• ThechlorineresidualsmonitoredmonthlyattheWheelerOillocationhavebeenlowbutdetectable,averaging0.06mg/LfromJanuary2018throughApril2019,withaminimumof0.04mg/Landamaximumof0.11mg/L(Figure7).
• Therequiredminimumrequiredchlorineresidualofa“detectable”concentrationwasmetduringallRTCRsamplingeventsin2018.
• ItwouldbehelpfultomaintainahigherchlorineresidualattheendsofthedistributionsystemsuchastheWheelerOillocation.
• Biologicalgrowthindistributionsystemscanconsumechlorine.Onemeansforperiodicallyrestoringchlorineresidualsistoconductahigh-velocityflushingprogramonceortwiceayeartohelpcleanthepipes.ThatisrecommendedforChestertohelpmaintainthechlorineresiduals.
Tofurtherinvestigatedistributionsystemchlorineresiduals,RCAPSolutionsstaffconductedachlorinemappingexerciseofthedistributionsystemonMarch27,2019.Locationswereselectedbothnearthebeginningofthedistributionsystem,inthemiddle,andparticularlyneartheedges.ResultsarepresentedinFigure8andTable1.
Figure8.DistributionSystemChlorineMappingResults(3/27/19)
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Table1.DistributionSystemChlorineMappingResults(3/27/19)
~timefreechlorine
(mg/L)~flushrate
(gpm)~flushtime
(min)~flushed
volume(gal)Location
12:15 0.48 NM NM NMPOE-lowerbuldingatWTP(formerlowerchlorinatorbuilding)
12:35 0.37 NM NM NM WTPclearwelleffluent
14:02 0.39 2 3 6 191Rte.20(ChesterVillageMarket)
14:20 0.00 7.5 12 90 381Rte.20(WheelerOil)
14:40 0.01 4.3 16 69 309Rte.20(PostOffice)
15:20 0.15 NM 4 8 260Rte.20(Richie'sGeneralService)
15:50 0.25 NM 4 8 29MainSt.(ClassicPizza/BluenoteCafé)
16:45 0.25 NM 2 4 15MiddlefieldRoad(TownHall)
17:00 0.00 5 6 30 106MiddlefieldRoad(residence)
17:40 0.17 1.4 5 7 289Rte.20(DavidShepherdresidence)NM=notmeasured
Thefollowingobservationsweremadefromthechlorinemappingstudyresults:
• Chlorineresiduallevelsinandnearthecenteroftownweresatisfactory,rangingfromahighof0.39mg/LattheChesterVillageMarketlocationtoalowof0.15mg/LatRichie’sGeneralServiceat260Rte.20.
• NochlorineresidualwasdetectedneartheendsofthedistributionsystemonbothRte.20(0.01mg/LatthePostOffice,and0.00mg/LatWheelerOilCo.)andMiddlefieldRoad(0.00mg/Lat106MiddlefieldRd.).
• TherewasasuddenchangeinthechlorineresiduallevelinaveryshortdistanceonRte.20.Specifically,aresidenceat289Rte.20had0.17mg/Lchlorine,whilethePostOfficeafewbuildingsfurtheroutonRte.20hadonly0.01mg/L.ThereasonforthatisthePostOfficeisonadead-endpartofthepiping.Afterpassing289Rte.20,thepipingsplitswithadeadendgoingtothePostOffice,andthemainpipingleavingRte.20andfollowingBayStateDrivebacktoRte.20neartheWheelerOilCo.monitoringlocationat381Rte.20andthenashortwaystotheendofthedistributionsystem.
RCAPSolutionsalsousedthedistributionsystemmaptodevelopaninventoryofthepipinginthesystem.Determiningthetotalvolumeinthedistributionsystemcomparedtothechlorinecontacttimeinthetreatmentplantcanhelpdetermineifbleedingwateroutofthedistributionsystem(e.g.,viablow-offvalvesorableederassembly)cansignificantlyhelpreduceoverallwaterageandthusshortenchlorinecontacttime.Atpresent,thechlorinecontacttank(clearwell)volumeaverages~98,000gallons,andsecondprimarydisinfectionsegmentofthe8-inchpipe(betweenthetreatmentplantandtheoldchlorinatorbuilding)is~4,363gallons.Thecombinedtotalvolumeforchlorinecontacttimeduringprimarytreatmentis~102,000gallons.Thevolumeofwaterinthedistributionsystempipingwascalculatedtobeapproximately57,000gallons.Combiningthosetwovolumes
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resultsinatotalvolumeof~159,000gallons,ofwhich64%isprimarydisinfectionand34%isinthedistributionsystem.Withanaveragedemandof45,000gpd,thatcorrespondstowateragesof2.3daysforthetreatmentsystemand1.3daysforthedistributionsystem.Thismeansthatevenifthewholedistributionsystemwasflushedout,thewateragewouldstillbe~64%ofwhatithadbeen.Solargechangesinoverallwateragearenotexpectedtoresultfrombleedingwaterattheedgesofthesystem.Nonetheless,bleedingwateroutattheedgesofthedistributionsystemmaybeapossiblemeansofimprovingchlorineresidualatthoselocations.Thatoptionmaybeconsiderediftherecommendedunidirectionalflushingprogramisnotimplementedordoesnotprovidethenecessaryresults.Ifbleedingittobeconducted,itisusefultocalculatethevolumeofwaterthatisdesiredtobewasted.Onepossiblegoalwouldbetowaste(andthusmove)avolumeofwaterequivalenttothevolumeofwaterinthepipingbetweentheendofadead-endpipeandthelocationofthenearestacceptablechlorineconcentration.UsingthatapproachandthechlorineresidualdatafromtheMarch27,2019chlorinemappingstudy,thefollowingvolumeswouldneedtobewastedfromeachofthetwodeadends:
• Rte.20:~13,500gallonsfrom289Rte.20(0.17mg/Lchlorine)aroundBaystateDriveandtotheverysoutheastendofthesystemonRte.20pastWheelerOilCo.at381Rte.20
• MiddlefieldRoad:~8,700gallonsbetweentheTownHallat15MiddlefieldRoad(0.15mg/Lchlorine)outtotheendofthepipeatthenorthendofMiddlefieldRoad
Inthefield,flushingcouldcontinueuntilallcolorisgoneandanacceptablechlorineresidualisobtained(andassumingadequatepressureremainsthroughoutthedistributionsystem).8.pH:ThefinalcomponentofthetreatmentsystemispHadjustmentwithsodiumhydroxide.Unlessotherwisespecified,drinkingwatershouldhaveapHof6.5to8.5(pertheUSEPAsecondaryMCL).OptimalCorrosionControlTreatment(OCCT)ofteninvolvesanarrowertargetrangeforpH,andistypicallyabove7.0orhigher.ThefinishedwaterpHvaluesfor2018areshowninFigure9.ThefollowingobservationsweremaderegardingpH:
• ThepHdataarerelativelyscattered,coveringarangefrombelow7.0toabove8.5,withanarithmeticaverageof7.7.ItisbestfordistributionsystemwaterqualitytomaintainamoreconstantpH.ThesystemOperatorisawareofthisissue,andhastriedtomaintainasconstantapHaspractical.ChestercouldinvestigatehowtomaintainamoreconstantpH.
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Figure9.FinishedWaterpHin2018
• RCAPSolutionsdidnotfindaspecificMassDEPrequirementforthefinishedwaterpH.
However,thesystemOperatorexplainedthatDanLaPradeofMassDEPtoldhimtouseafinishedwaterpHrangeof7.3to7.5.ThatistoonarrowarangeofpHforpracticalimplementation,especiallyforalow-alkalinitywater,andshouldbewidened.AsisshowninFigure9,thatnarrowpHtargetwasnotmetveryfrequently.
• GiventhattheregulatorycomplianceissueiswithTHMsandnotleadandcopper,raisingthepHisnotrecommendedasthatcanresultinhigherTHMs(higherpHalsoresultsinaweakerchlorinedisinfectant).
• RCAPSolutionsrecommendsatargetfinishedwaterpHof7.5+/-0.3(i.e.,pHof7.2to7.8).Thiswouldwidentheallowablerangefromadifferenceof0.2uptoadifferenceof0.6pHunits.
9.DisinfectionByproducts:Twoclassesofdisinfectionbyproducts(DBPs)areregulatedbytheDisinfectant/DisinfectionByproductRule(D/DBPR):totaltrihalomethanes(TTHM,thetotalofthefourTHMs)andthetotaloffivehaloaceticacids(HAA5).ComplianceisdeterminedbymonitoringforTHMsandHAAsatselectdistributionsystemlocationsonceperquarter,andthencalculatingtheLocationalRunningAnnualAverage(LRAA)foreachsamplesite.TheTTHMandHAA5LRAAconcentrationsateachsamplesitemustnotbeabovetheMCLsof80µg/Land60µg/L,respectively.ThecurrentDBPmonitoringlocationsareat191HuntingtonRoad(ChesterVillageMarket),whichislocatednotfarfromthewatertreatmentplant,and381HuntingtonRoad(WheelerOilCo.),whichislocatedonadead-endlinenearthesoutheastendofthedistributionsystem.
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TheLocationalRunningAnnualAverageresultsforTTHMsarepresentedinFigure10,andforHAA5inFigure11.TheindividualTTHMresultsareplottedinFigure12forthesamplesiteatWheelerOilCo.,andfortheChesterVillageMarketinFigure13.IndividualHAA5resultsareshowninFigures14and15,respectively,forWheelerOilandChesterVillageMarket.ThesedatacoverthefullperiodthattheStage2D/DBPRhasbeenineffect,sincethebeginningof2013,andupthroughthe2ndquarterof2019.ThefollowingobservationsweremaderegardingTTHMandHAA5atthetwomonitoringlocations:
• TTHMshavebeenhighestattheWheelerOilCo.location,andHAA5havebeenhighestattheChesterVillageMarket.
• Intermsofregulatorycompliance,theMCLforTTHMswasexceededattheWheelerOilCompanylocation(381HuntingtonRoad)forthreequartersinarow(thethirdandfourthquartersof2018andthefirstquarterof2019).Themostrecentquarter’sresultsareincompliancewiththeDBPlimits,asthemaximumLRAAforTTHMis79µg/L.
• WhiletherehavebeennoexceedancesoftheMCLforHAA5,theLRAAhasattimescomeclosetotheMCL(Figure11andFigure15).ThehighestLRAAforHAA5was58µg/LattheChesterVillageMarketlocation(191HuntingtonRoad)on2/20/18,closetotheMCLof60µg/L.Assuch,HAA5arealsoofconcerninadditiontoTTHMs.
• ThereappearstobeasteadyincreaseinTTHMattheWheelerOilCo.location(381HuntingtonRoad)startingin4thquarterof2016.ThathasresultedinasteadyincreaseintheLRAAforTTHMsatthatsite,increasingfrom40µg/Lin3rdquarter2017upto92µg/Linthe4thquarterof2018.HAA5alsoincreasedduringasimilartimeperiod.Thecauseoftheseincreaseshasnotbeenidentified.Itisnotedthattheflushingprogramendedsometimearoundtwoyearsago.ItisalsopossiblethatthischangewasattributableatleastinparttoswitchingsourcewaterfromAustinBrookReservoirtoHornPond,butthetimingofthatswitchcouldnotbedeterminedandthusnocorrelationcouldbemade.
• ThetrendofincreasingTTHMconcentrationovertimeduringthepasttwoyearscontrastswiththetypicalTTHMseasonalpatternwherethehighestresultsarefoundinAugustduetothewarmertemperatures,andthelowestresultsinFebruaryduetocoldertemperatures.However,fortheChesterVillageMarketlocation,thehighestTTHMvaluesince2013was100µg/LinFebruary2018(HAA5alsowasatitshighestforthatlocationinFebruary2018),andthesecond-highestvalueof87µg/LwasinNovember2018.Incontrast,theAugust2018samplewasonly38µg/L.Noexplanationwasfoundforthisanomaly.
• TheLRAAdataforTTHMsshowninFigure10suggestthattherehavebeenperiodswheretheTTHMslevelswerenotmuchdifferentbetweenthetwosamplinglocations,including2013throughearly2015,and2017throughearly2018.Givenbothsamplesitesreceivewaterfromthesamesource,theonlyfactorthatwouldbeexpectedtoimpactdifferencesintheirTTHMlevelswouldbewatertraveltime(i.e.,chlorinecontacttime).Thereappearstobeaperiodfromlate2015through2016whenthewateragedifferencemayhavebeengreater,asthereisalargerdifferencebetweenthetwosamplesitesfortheTTHMLRAAs.
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Figure10.TTHMLocationalRunningAnnualAverages
Figure11.HAA5LocationalRunningAnnualAverages
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Figure12.TTHMat381HuntingtonRoad(WheelerOilCo.)
Figure13.TTHMat191HuntingtonRoad(ChesterVillageMarket)
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Figure14.HAA5at381HuntingtonRoad(WheelerOilCo.)
Figure15.HAA5at191HuntingtonRoad(ChesterVillageMarket)
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• InthecaseofHAAs,thereisacleardifferenceinHAA5levelsatthetwomonitoringsites,withlevelsattheWheelerOilCo.nearzero.ThisdifferenceinHAA5islikelyaresultofbiodegradationofHAA5withinthedistributionsystem,andgiventhelongerwaterageatWheelerOilCo.thereismoretimeforthebiodegradationtooccur.Whilethebiodegradationiscommoninthewarmermonths,itnormallyislessimpactfulduringthecoldermonths.Inthiscase,however,forthepastfouryearsbasicallyalloftheHAA5thathadbeenformedhaddegradedbythetimethewaterreachedtheWheelerOilCompanysite(Figure14).
• AnothernotabletrendisthatthreeofthefivehighestHAA5resultsoverthepastsixyearsfortheChesterVillageMarketwereinFebruary(Figure15).Typically,HAA5wouldbehigherinMayandNovemberthaninFebruary.ThismaysuggestsubstantialbiodegradationofHAA5leadingtotheChesterVillageMarketsite(despitethepresumedrelativelyshortwaterageatthatsite),astheFebruaryresultswereoftensubstantiallyhigherthanthedatafortheotherquarters,especiallythe3rdquartersamplinginAugust.
GiventherehavebeennoMCLexceedancesforHAA5,andthatthehighestTTHMexceedancewasbyonly15percentovertheMCL(asopposedtomuchhighervalues),averylargereductioninDBPsmaynotbenecessary.SimpleoperationalimprovementsmaybesufficienttoregainandmaintaincompliancewiththeDBPMCLs.Thoseimprovementsshouldbeimplementedandevaluatedpriortoconsideringanymajorcapitaladditiontothetreatmentsystem.ThreeapproachesarerecommendedatthistimeforimprovedcontrolofDBPs:
1. Implementaregularflushingprogram:Aswasdiscussedpreviously,semi-annualunidirectionalhigh-velocityflushingofthe
distributionsystemisrecommendedtohelpmaintainchlorineresidualsneartheendsofthesystem.FlushinghasalsobeenknowntobeabletoreduceDBPs,andthusisalsorecommendedforthatpurpose,especiallyforreductionofTHMs.Flushingcouldremovesomebiofilmfromtheinteriorofthepipes,whichcouldpotentiallyreducethebiodegradationofHAAs,andthusresultinhigherlevelsofHAAs.ThatpotentialeffectshouldbelookedforwhenreceivingthequarterlymonitoringresultsforDBPs.
2. Potentiallyswitchsourcewatertoreduceinfluentnaturalorganicmatter(NOM):Twosourcewatersareavailabletofeedthetreatmentplant.Itisrecommendedthat
Chesterregularlymonitorbothsourcewatersfortotalorganiccarbon(TOC).TOCservesasasurrogateforNOM.UV-254anddissolvedorganiccarbon(DOC)arealsoavailablesurrogatesforNOM.MonthlymonitoringofTOCisrecommendedforthefirstyear,butatminimumChestershouldsamplebothsourcewatersforTOConceperquarteronthesamedaysthatsamplingforDBPsisconducted.Turbidityshouldalsobemonitored,asthedecisionofwhichsourcetousemaybepredicatedontherelativelevelsofbothturbidityandTOC.TheTOCdatamaybeusedtodeterminewhichsourcewatertouse,especiallyduringthewarmermonthswhenTTHMformationismoreofaproblem.ItisexpectedthattheTOCinAustinBrookReservoirwillbelowerthanthatintheshallowerandslower-flowingHornPond.Therawwatertapinthetreatmentplantmaybeusedforsamplingthecurrentsourcewater,whileasampleoftheothersourcewatercanbecollectednearwherethewaterexitsthepond/reservoir.
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ThesourcewaterwasmonitoredforTOCfour(4)timesTOCin2018,withvaluesrangingfrom4.3to5.0mg/L.WhilethosesampleswerelabeledasbeingfromAustinBrookReservoir,theywerereportedlyfromHornPondasthatwasthesourcewaterbeingusedatthetime.Assuch,cautionshouldbeexercisedinusinganyrecentdatabecauseoftheissuewithsomeHornPondsamplesbeinglabelledasAustinBrookReservoir.
3. Optimizeuseofthegranularactivatedcarbon(GAC)sandwichfilterforremovalofNOMthroughimprovedmonitoringofTOC:
Filter#3hasthegranularactivatedcarbon(GAC)sandwich,withalayerofGACbetweentwolayersofsand.TheGACwasaddedtothisfilterforremovalofnaturalorganicmatter(NOM),whichisaprecursortoDBPformation.ThesorptivecapacityoftheGACforNOMandotherorganicchemicalsislimited.Theextentthesorptivecapacityhasbeenexhaustedcan,inpart,bemonitoredbyperiodicallyanalyzingtotalorganiccarbon(TOC)intheinfluentandeffluentfromthisfilter.WhentheeffluentTOCapproachestheleveloftheinfluentTOC,theactivatedcarbonisnearingexhaustionforadsorbingNOM.ConsiderationshouldbegiventoreplacingtheactivatedcarbonpriortoexhaustingitscapacitytoremoveNOM.
ATOCmonitoringprogramisrecommendedtohelpoptimizeuseoftheGACsandwichinFilter#3.MonthlymonitoringofTOCisrecommendedforthefirstyear,butatminimumChestershouldsamplefilterinfluentandfiltereffluentforTOConceperquarteronthesamedaysthatsamplingforDBPsisconducted.SampleandanalyzeforTOCinthefilterinfluent,theFilter#3effluent,andeithertheFilter#1orFilter#2effluentasacontrolsample.OnlyfilterscurrentlyonlineshouldbemonitoredforTOC.Sincethefilterinfluentsampleiseffectivelythesameasthesourcewatersampleforthecurrentsourcebeingused,itwouldbeprudenttodothissamplingonthesamedaysthattherawwaterTOCissampled,asrecommendedabove.
TOCwasmonitoredforboththerawwaterandfinishedwateron9/17/18and11/26/18,withTOCremovalbeing33%and13%,respectively(averagesof4.7mg/Linfluentand3.6mg/Leffluent).ItishopedthatamorestrategicandtargeteduseofthecarbonsandwichfilterwillresultinimprovedTOCremoval.
IfthoseapproachesdonotsatisfactorilyreduceDBPs,thenotherapproacheswouldneedtobeconsidered,includingpossiblybleedingwateroutoftheendsofthesystemtoreducewaterage,installingadditionaltreatmentcapabilitytoreduceNOM,orreducingpHtodecreaseTHMformation.10.Color:Nohistoricalcolordatawerefoundduringthisinvestigation.MassDEPmentionedcolorissuesintheirAugust24,2018lettertoChester,andalsomentionedinaninternalMassDEPe-maildatedAugust16,2018thatanearlierbrownwatercomplainthadbeenresolvedupondiscoveryandrepairofaleak.ThewatersystemOperatorhasreceivedafewcomplaintsaboutthewater’sappearance,includingayellowishcolor,andalightbrownishtea-likecolor.RCAPSolutionsstaffspokewithsometownresidentsabouttheirperceptionofthewaterqualityduringasitevisitonMarch27,2019,andsomeoftheresidentsnotedthatthewaterissometimescoloredeitherlightyelloworlightbrown.RCAPstaffconductedavisualexaminationofthewatercolorfromeachlocationthatchlorineresidualwasmeasuredduringthechlorinemappingstudyconductedonMarch27,2019.ThissimpletestinvolveslookingforcolorinawatersampleinsideawhiteStyrofoamcup.Distilledwaterwasusedfor
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comparisonasneeded.Ayellowtingetothewaterwasevidentatsomeofthelocations(butnotatalllocations),anditwasalighteryellowatsomelocationsthanatothers.AnexampleoftheyellowtintisshowninFigure16,whichcomparesadistributionsystemsamplewithdistilledwater.Nocolorwasdetectedinthetreatmentplant’sfinishedwater.
Figure16.Yellow-tingedWater(3/27/19)–
Distributionsystemsampleisontheleft,distilledwaterontherightOnecommoncauseofcolorationofdistributionsystemwateristhereleaseofiron,manganese,and/orothermetalsfromtheinteriorsurfaceofthepipe.Someofthepipesaremadeofiron,whilemanganesecandepositovertimeandbeasourceofcolorifitdissolvesintothewater.Manganesecancausewatertobeyellow,brown,orevenblack,dependingontheconcentration.Irontypicallyresultsinarust-coloredwater.Onemeansforreducingthesecolorissuesistomaintainasoundflushingprogramthathelpscleandepositsoffoftheinsideofthepipes.Chesterhashistoricallyconductedadistributionsystemflushingprogramtwiceperyear,butreportedlydidnotdothatthepasttwoyears.Resumingthesemi-annualflushingprogramisrecommendedtohelpreducethecolorobservedinthewater.Theflushingprogramshouldbeconductedunidirectionally,andwithsufficientvelocitytosufficientlycleantheinteriorofthepipes.Asnotedearlier,aproperlyconductedflushingprogramcanalsohelpmaintainchlorineresidualsandreducedisinfectionbyproducts.11.LeadandCopper:TheChesterWaterDepartmentprovidespHadjustmentasacorrosioncontrolmeasure.ThefinishedwaterpHisplottedinFigure9,andwasdiscussedpreviously.TheLeadandCopperRule(LCR)distributionsystemleadmonitoringdataarepresentedinFigure17andforcopperinFigure18.Basedontheavailabledata,leadandcoppercorrosiondoesnotappeartobeanissue,asneitherActionLevelhasbeenexceeded,andallindividualsampleresultswerebelowtheActionLevels.Thoughnotoptimal,thefluctuatingpHandchlorinelevelsdonotappeartohavecausedanyLCRcomplianceissues.
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Figure17.LCRLeadMonitoringResults(2013-2017)
Figure18.LCRCopperMonitoringResults(2013-2017)
12.SummaryandConclusions:Muchofthewaterqualityisgood,butimprovementcouldbemadeinreducingTHMs,HAAs,andcolor,andalsoforincreasingchlorineresidualsattheendsofthedistributionsystem.Implementationofasemi-annualhigh-velocityunidirectionalhigh-velocityflushingprogramisrecommended,andcouldhelpachieveallfourofthosegoals.ImplementationofamonitoringprogramforTOCisalsorecommendedtohelpselectwhichsourcewatertousetominimizeinfluentNOM,andtooptimizeuseoftheactivatedcarbonsandwichfilterforremovalofNOM.
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Basedontheavailabledata,leadandcoppercorrosiondoesnotappeartobeanissue,asneitherActionLevelhasbeenexceeded,andallindividualsampleresultswerebelowtheActionLevels.Thoughnotoptimal,thefluctuatingnatureofthepHandchlorinelevelsdonotappeartohavecausedanyLCRcomplianceissues.
13.Recommendations:ThefollowinglistsummarizestheprimaryrecommendationsdevelopedduringthisevaluationtohelptheChesterWaterDepartmentimproveoperationsandwaterquality:
DBPcontrol:
1. Implementasemi-annual,unidirectional,high-velocityflushingprogramtohelpcleanthedistributionsystempipes.ThiscanhelptoreduceDBPs,maintaindistributionsystemchlorineresiduals,andreduceincidentsofcoloredwater.Thosethreeissuesshouldbemonitoredcloselyafterflushinghasbeenconducted.Formaintainingchlorineresidual,focusonthenorthendofMiddlefieldRoadandthesoutheastendofRte.20.
2. ImplementaTOCmonitoringprogramforthetwosourcewaters(monitorturbidityalso).ConsiderusingthesourcewaterwiththelowerTOCduringthewarmerseasonstoreducetheamountofinfluentNOM,aslongasturbidityisnotanissue.DetailedsamplingrecommendationsareprovidedaboveinSection9.
3. ImplementaTOCmonitoringprogramforthefiltereffluenttohelpdeterminethesaturationstatusofthegranularactivatedcarboninFilter#3.UsethesedatatooptimizetimingoftheuseofFilter#3forremovalofNOM.DetailedsamplingrecommendationsareprovidedaboveinSection9.
Additionalprimaryrecommendationsincludethefollowing:
4. IftheunidirectionalflushingdoesnotsolvetheDBPandchlorineresidualissues,thenwateragecouldbecontrolledsomeattheedgesofthedistributionsystembywastingwaterthroughblow-offassemblies(i.e.,bleedingwateroutofthedistributionsystem).ThiscouldbedoneatthenorthendofMiddlefieldRoadandattheeastendofRte.20.
5. ProperlylabelthesourcewatersamplesasHornPondorAustinBrookReservoir(theyhavebeenmislabeledrecentlyasAustinBrookReservoirwhenitreallywasHornPondthatwassampled).
6. Installsampletapsforallthreeindividualfiltereffluents(IFEs)andalsofortheonecombinedfiltereffluent(CFE).ThereshouldbeanonlineturbiditymeterfortheCFEsampletouseforregulatorycompliancereporting.
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7. TurbidityresultsreportedtoMassDEPhavebeenforthefinishedwater(i.e.,treatmentplanteffluentatthePOE),butinsteadshouldbeforthecombinedfiltereffluent(CFE).Reportingcombinedfiltereffluentshouldlowertheresultsreportedfromanaverageof~0.11NTUtoapproximately~0.03NTU.
8. ImplementanewtargetfinishedwaterpHrangeof7.5+/-0.3(i.e.,7.2to7.8).
9. InvestigatehowtomaintainamoreconsistentfinishedwaterpH.
10. Investigatehowtomaintainamoreconsistentfinishedwaterchlorineresidual.
Otherrecommendationsincludethefollowing:
11. RCAPwasnotabletoobtainthespecificationsusedintheSCADAcalculationstodeterminethevolumeofthechlorinecontactors(partofdeterminingchlorinecontacttime),andthuscouldnotconfirmthisaccuracy.Also,thetracerstudythatresultedindeterminingabafflingfactorof0.13alsowasnotlocated.Thisinformationshouldbeobtainedandreviewedforaccuracy.Thatwouldhelpconfirmchlorineisnotbeingunderdosedoroverdosedasaresultofusinganinaccuratechlorinecontacttime,andconfirmthatbothdisinfectionsegmentsarenecessary.
12. TheSCADAsystemcouldbeimprovedtoincludetrendchartsofallwaterqualitydata.
13. TheTownofChestershouldbecomemoreinvolvedinthewatersystemoperations,especiallythetreatmentsystem,toreducerelianceonthecontractedcertifiedoperator,andtogainabetterunderstandingoftheissuesfacingthewatersystem,aswellasthetimeandresourcecommitmentsthatareneededtoensureefficientandsustainableoperationsandfuturecompliancewithallapplicableregulations.
14. Improvedatamanagement,includingtabulatingandplottingallhistoricaldata.SomeoneattheTownshouldfollowthedataandcomplianceissues,notjustthecertifiedoperator.
15. Developandmaintainacustomercommentlog.
16. Developandimplementapublicrelationscampaignaboutwaterquality.
17. Formonitoringsites,includetheaddressinthesitename(e.g.,“381Rte.20”or“WheelerOilCo./381Rte.20”).
18. UpdatethenameoftheWalkerBrookStoresamplesitetothecurrentnameofChesterVillageMarket(at191Rte.20/HuntingtonRd.).