KnEMaterialsScience FibEnTech21 1stInternationalFibEnTechCongress(FibEnTech21)Newopportunitiesforfibrous materialsintheecologicaltransition Volume2022 Researcharticle WaterReuse:ARiskAssessmentModelfor WaterResources AnabelaRebelo1*,AlbertinaBentoAmaro2,andFelisbinaQuadrado1 1PortugueseEnvironmentAgency,WaterResourcesDepartment,2610-124,Amadora,Portugal 2FibEnTechandDepartmentofChemistry,UniversityofBeiraInterior,RuaMarquêsd’Ávilae Bolama,6201-001,Covilhã,Portugal Abstract. Theincreasingdemandsforwaterformultiplepurposescombinedwithclimatechange challengesareleadingtowaterscarcityandqualitydeterioration.Portugalisvulnerable totheimpactsofclimatechangeandtherefore,theuseofreclaimedwatershasbeen identifiedasasuitablealternativewatersourcefornon-potableuses,suchasirrigation, toovercomewatershortages.Inthelasttwoyears,newpoliciesforwaterreusehave beenapprovedatthePortugueseandEuropeanlevels.Thelegalframeworksare supportedintheinternationalguidelinesdevelopedbytheInternationalOrganization forStandardization,namelyforirrigation,urbanusesandhealthriskassessment. Inthisway,allreuseprojectsmustfollowafit-for-purposeapproach,i.e.,thewater qualityneedstomeettherequirementsofitsspecificend-useswithoutcompromising publichealthorthesurroundingenvironment,andallreuseprojectsmustconduct ariskassessmentforhealthandtheenvironment.Quantitative,qualitativeorsemiquantitativemodelscanbeused.Althoughaquantitativeassessmentmaybedesirable, thesemodelstendtobecomplexandpresenthighuncertainty.Furthermore,these usuallyrequireextensivedatawhichareoftennotavailable.Accordingly,thisstudy intendedtodevelopaconceptualmodeltodealwiththeriskassessmentforwater resources,namelysurfaceandgroundwaters.Asemi-quantitativeapproachwas employedfortheriskcharacterization,usingempiricalqualitativejudgmenttoassess therelativeimportanceofhazards,exposureroutes,scenariosandbarriersinplace. Theuseofastrategicassessmentallowsthequalitystandardsthatmeettheneeds ofeachprojecttobevalidated.Thedevelopedmodelwasappliedtoacasestudyto illustrateitsapplicability.
Keywords: waterreuse,waterresources,riskassessment,semi-quantitativemodel,
compoundsofemergingconcern 1.Introduction Theincreasingdemandsforwaterresourcesformultiplepurposessuchaspublicwater supply,agriculture,industry,recreationalusesandothersareleadingtowaterscarcity andqualitydeterioration.Theintensificationofsevereweatherconditionsduetoclimate change,suchasdroughts,andurbandevelopmenthasputasignificantstrainon freshwatersupplies[1].Therefore,thesearchfornewalternativewatersourceslike reclaimedwatersisrisinginseveralcountries,suchastheUnitedStatesofAmerica, AnabelaRebelo*,AlbertinaBentoAmaro,andFelisbinaQuadrado,(2022),“WaterReuse:ARiskAssessmentModelfor 1stInternationalFibEnTechCongress(FibEnTech21)Newopportunitiesforfibrousmaterialsintheecologicaltransition,KnE MaterialsScience,pages193–203.DOI10.18502/kms.v7i1.11623 Page193 CorrespondingAuthor:Anabela Rebelo;email: anabela.rebelo@apambiente.pt Published 10August2022 Publishingservicesprovidedby KnowledgeE AnabelaRebeloetal.This articleisdistributedunderthe termsofthe CreativeCommons AttributionLicense,which permitsunrestricteduseand redistributionprovidedthatthe originalauthorandsourceare credited. SelectionandPeer-reviewunder theresponsibilityofthe FibEnTech21Conference Committee.
ThecurrentpoliciesintheEuropeanUnionfortheuseofreclaimedwaterforagricultureirrigation(RegulationEU741/2020)andinPortugalformultipleuses(DecreeLaw119/2019,21���� August)emphasesontheadoptionofprojectssupportedona
However,theuseofknowledge-basedmodelsalreadyshoweditsfeasibilityand applicabilitywithsimpleoutputsthatmayprovidesupportforenvironmentalauthorities
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riskmanagementframeworkandinqualitystandardsdefinedaccordingtoafit-forpurposeapproach,basedonISOstandards16075.Thisapproachissupportedonthe productionofwaterqualitythatmeetstheneedsoftheintendedend-users.Accordingly, theEuropeanandPortuguesepoliciesestablishthatallprojectsshallfollowarisk assessmentforhumanhealthandtotheenvironment,whichincludeswaterresources. Thistypeofappraisalwillallowtoselectthequalitystandardsapplicabletoeachreuse projectandtheriskmanagementconditionsthatshouldbefollowedtoensurean associatedminimumriskvalue[3].Forhealthriskassessmentwerealreadydeveloped severalqualitative,semi-quantitativeandquantitativemethods,butforwaterresources, themostpopularmethodsarebasedoncomplexmathematicalmodelstoassess pollutantsfateandtransportonenvironmentalcompartmentsortoevaluatehydrological conditions[5].Inthequantitativemethods,theriskcharacterizationisusuallybasedon theratiobetweenthepredictedenvironmentalconcentrations(PEC)andthepredicted no-effectconcentration(PNEC)forwater,sediment,andbiota.However,thistypeof methodologypresentsseverallimitations,suchastheuseofstandardizedbioassays involvingsinglespeciesanduniquesubstances,withouttakingintoaccountthereal routesofexposureandtheeffectsofmixturesandlargeuncertaintiesinextrapolating dataacrossdoses,species,andlifestages,namelyduetothelackofdataondoseresponserelationships[6].Hence,thesetypeofapproachesrequirestheexistenceof asignificantnumberofmonitoringdatafromreuseprojectstoestablishthepredicted concentrationsassociatedwitheachexposurescenario,sinceinthispracticenodirect dischargetowateroccurs,whichlimitstheapplicabilityofthesemethodologiestowater reuseprojects.Consequently,thequalitycriteriaappliedtoacertainprojectareusual flatlegalrequirementswithouttakingintoaccountlocalconditions,suchaswaterbodies characteristics,status,andusesofsurfaceandgroundwaters.
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Singapore,Australia,Spain,Malta,Cyprus,andeveninPortugal[1-3].However,the useoftreatedwastewatersmayposesomerisks,wheremicrobialrisksareusuallythe mainfocustoprotecthumanhealth,butotheraspectsarealsocatchingattention,in particular,disinfectionby-products(DBP)andcompoundsofemergingconcern(CoC) whichcanposerisktowaterresourcesandaquaticecosystemsandthroughtheseto humans[2-4].
2000/60/EC,usuallyknownasWaterFrameworkDirective(WFD).Theclassification ofhazards,ascanbeseenintable1,ismadeaccordingtoitscharacteristics,treatmentlevel,andexpectedconcentrationsinreclaimedwaters.Fornutrientstheused criteriaarethetreatmentlevel,thelegalclassificationofwaterbodiesintermsof sensibilitytoeutrophication(Directive91/27/EEC)andvulnerabilityduetonitrates pollution(91/676/EEC)andtheecologicalstatusofwaterbodies(whentheconcern parametersareNorP).Forchemicals,theclassificationismadeaccordingtoexpected concentration,whichcanderivefrommonitoringdataorfromaproposalofaquality standardtowriteonapermit. Table 1: Hazardlevel. Nutrients Chemicalsinwaterbodies Hazard Treatmentlevel N&P(mg L−1) Unitsofconcentration H�� WithoutNandPremoval1 N > 15andP > 3 >EQS2 or >30 LoQ3,4 9 WithpartialremovalofNorP2 N ≤ 15orP ≤ 3 >10 LoQ4 7 WithpartialremovalofNorP N ≤ 15orP ≤ 3 >LoQ 5 WithpartialremovalofNandP N ≤ 10andP ≤ 3 >LoD5 3 WithadvanceremovalofNand P N ≤ 5andP ≤ 0,5 <LoD 1 DOI10.18502/kms.v7i1.11623 Page195
onthedecision-makingprocess[5,7].Takingintoaccounttheseconsiderations,this studyaimstoproposethedevelopmentofasemi-quantitativemodeltoperformwater reuseriskcharacterizationforwaterresources,includingsurfaceandgroundwater,and demonstrateitssuitabilitytovalidatethequalitystandardsforchemicalparameters,like nutrients(NandP),DBPandCoC,tobeappliedtoawaterreuseprojectandtobenoted inthewaterreusepermitsissuedbyenvironmentalauthorities[5,7-9].Theproposed modelisasite-specificassessment,supportedonthetypicaltierapproachincluding hazardidentification,exposureandpathwayassessment,andriskcharacterization[6].
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2.Methodology
Theproposedmodelwassupportedonapreviousconceptualmodeldevelopedby Rebeloetal.,namedRiskAssessmentModelforWaterResources(RAMWR)andthe ISO16075-2:2020andallfactorsaremeasuredaccordingtoanimportancescalefrom 1to9[3,7].Themodelproposedtheriskdeterminationbytheproductbetweenhazard, thevulnerabilityofwaterresourcesanddamage.
Thehazardidentification,withinthescopeofthecurrentstudy,isnutrients(nitrogen andphosphorous)andchemicals,suchasDBP,CoC,andprioritysubstances/priority hazardoussubstancesorspecificpollutantsclassifiedaccordingtotheDirective
KnEMaterialsScience FibEnTech21 1 Invulnerableareastonitratepollutionorwhenwaterbodystatusislessthan“Good” duetoparameterN,considerHazardforNequalto7andforPequalto5;Insensitive areastoeutrophicationorwhenwaterbodystatusislessthan“Good”forparameterP, consider.HazardforNequalto5andforPequalto7. 2 EQS–Environmentalqualitystandard(legalvalue)applicabletowaterbodies accordingtoitsstatusoruses 3 LoQ–Limitofquantificationoftheapplicableanalyticalmethod 4Relationshipestablishedaccordingto[10] 5 LoD–Limitofdetectionoftheapplicableanalyticalmethod Thepathwayassessmentconsidersrunofftosurfacewatersandinfiltration,leaching andpercolationtogroundwaters.Thevulnerabilityofwaterresources(V����)isgivenby equation1: V����=Vp����×fp���� +Vp����×fp���� (1) WhereVp���� andVp���� arepartialvulnerabilitiesdirectlyachievedbyFigure 1 and f��arepartialfactorsequaltofp���� =Vp���� /(Vp���� +Vp���� )andfp���� =Vp���� /(Vp���� + Vp���� ),developedaccordingtothesameprinciplesproposedbyotherauthors[7]. Fromequation1ispossibletoobtainfourdifferentvalueswhichareprioritizedthrough theimportancescaleaccordingtotable2. Infiltration rate to groundwater None Low Medium High GroundwaterSensitivity noaquiferShallowwithprotection I ۲ ٤ ٦ ٦ Deep aquifer with protectionclay II ۲ ٤ ٤ ٦ Deep aquifer protectionclaysignificantwith III ۲ ۲ ٤ ٤ No thecontinuityhydrologicalwithaquifertoarea IV ۲ ۲ ٤ ٤ Sensitivity to surface water ٦ ٦ ٤ ۲ IV III II I High Medium Low None Surface runoff Figure 1: Matrixforsurfaceandgroundwatervulnerabilityassessment(adaptedfromISO16075-1:2020). Fromtheexposureevaluationofwaterresourcesispossibletodeterminetrough equation2,theglobalvulnerability(V��). DOI10.18502/kms.v7i1.11623 Page196
KnEMaterialsScience FibEnTech21 Table 2: Waterresourcesvulnerablyexpressedinimportancefactors. ValuesforV���� givenbyequation1 N&P(mg L−1) 5,2 9 5,0 7 4,0 5 3,3 3 ����=������×∑������������������ ��������×���������� (2) Wheref����������������isthefactorapplicabletobarriersaccordingtotable3,wheref������xn�������� isanormalizationfactor,toadjustthescaletoacommonrange[11],wheren�������� is thenumberofscenariosgivenbytable4andf������isthemaximumvalueoftheused importancescale(9).Thenumberofexposurescenariosdependsonthebarriersin placesinceabarrierisameanthatreducesorpreventstheexposureofthereceiving waterstothereclaimedwaters[8,9].Inthisstudy,theproposedbarrierswereadopted fromRebeloetal.andthenumberofexposurescenariosisdisplayedintable4[3,7], Table 3: Applicablebarriersforwaterresourcesprotection Typeofbarrier Importancefactor Absenceofbarriers 9 Leakdetectionsystem 7 Partialretentioncapacity/irrigationsystemaccordingtowatercropneeds 5 Totalretentioncapacity 3 Table 4: Numberofexposurescenariosaccordingtobarriersinplace. Typeofbarrier Numberofexposurescenarios (n��������) Absenceofbarriers 1 Leakdetectionsystem 1 Partialretentioncapacity/irrigationsystemaccordingtowatercrop needs 1 Totalretentioncapacity 1 LeakdetectionsystemPartialretentioncapacityandirrigationsystem accordingtowatercropneeds 2 Leakdetectionsystemandtotalretentioncapacity 2 Thefinalsteptodeterminetheriskisthedefinitionofdamagewhichcanbeattained bytheseverityofdamage versus thelikelihoodofoccurrenceoffailureinbarriers (whichalsotranslatesthelikelihoodofexposureoccurrence).AccordingtotheISO 20426:2018,acertainlikelihoodofexposureoccurrencecanbedefineddependingon dataavailabilityascanbeseenintable5. DOI10.18502/kms.v7i1.11623 Page197
KnEMaterialsScience FibEnTech21 Table 5: Likelihoodofoccurrenceofwaterresourcesexposuretocontamination(adaptedfromISO 20426:2018). Likelihoodof occurrence Observationsaccordingtoevidence(fromotherirrigation projects)and/orliterature Value Unlikely Hasnothappenedinthepastbutmayoccurinexceptional circumstancesinthereasonableperiod 2 Possible Mayhavehappenedinthepastand/ormayoccurunderregular circumstancesinthereasonableperiod 3 Likely Hasbeenobservedinthepastand/orislikelytooccurinthe reasonableperiod 4 Almostcertain Hasoftenbeenobservedinthepastand/orwillalmostcertainly occurinmostcircumstancesinthereasonable 5 Thereasonableperiodisdefinedaccordingtothevalidityperiodofreusepermits asmentionedinthePortugueselegislation,i.e.,10years(Decree-Law119/2019,21���� August).Theseverityofdamagedependsonthecharacteristicsofthereceivingwater resources,namelyitsclassificationaccordingtoexistentlegislation(e.g.,sensitiveareas accordingtotheDirective91/271/EEC),statusofthewaterbodyaccordingtotheWFD andtherespectiveexistinguses(e.g.,drinkingwaters).Thiscorrelationispresentedin table6: Table 6: Theseverityofdamageforwaterresourcesfromexposuretocontamination. Severityof damage Observationsaccordingtowaterresourcesevidence Value Severe Waterbodywithstatuslessthangood 5 Major Waterbodyingoodstatus,withdefineduseandclassification (vulnerabletonitratepollutionorsensitivearea) 4 Moderate Waterbodyingoodstatus,withdefineduseorclassification (vulnerabletonitratepollutionorsensitivearea) 3 Minor Waterbodyingoodstatus,withoutdefineduseorclassification (vulnerabletonitratepollutionorsensitivearea) 2 Thepartialdamage(d��)associatedwiththeexposureroutesandexposurescenarios consideredisgivenbythematrixpresentedinFigure 2,bycombiningthevalues obtainedintable5withthedatafromtable6.Theglobaldamage(D)canbecalculated byequation3: ��=∑����×���������� ��������×���������� (3) Wheren��������isthenumberofexposurescenariosfromtable4andf������xn�������� isa normalizationfactorsimilartoequation2. Theriskforwaterresources(R����)isachievedbytheproductbetweenthehazard(Hz),theglobalvulnerability(V��),andassociateddamage(D),normalizedtothe maximumvalueofimportancescale(9),i.e.: ������= ����×����×�� �������� = ����×����×�� 9 (3) DOI10.18502/kms.v7i1.11623 Page198
KnEMaterialsScience FibEnTech21 Unlikely Possible Likely Almostcertain Likelihood of occurrence of barrier failure 2 3 4 5 Minor damageofSeverety 2 2 4 4 5 Moderate 3 4 4 6 7 Major 4 4 6 8 9 Severe 5 5 7 9 9 Figure 2: Expressionofpartialdamage(di)associatedwiththebarrierfailure(adaptedfromRebeloetal. [3]). TheR���� valuevariesfromaminimumvalueabovezero(0)tonine(9)dependingon thenumberofscenarios,barriersandthecharacteristicsofwaterbodies.TheprioritisationisaccomplishedbyconversionoftheR���� resultsintoathree-levelqualitativescale asfollows:DespicableRisk(R���� <3),AcceptableRisk(3≤R���� <7),andUnacceptable Risk(R����≥7),similartodescriptionsusedbyotherauthors[3,7].Whentheriskpresents anunacceptable,theprocessshouldberepeatedconsideringadditionalminimization measures,suchasadditionalbarriersorincreaseoftreatmentlevelandasaresult alowerlevelofhazard(Hz),whichmeansaproposalforaqualitystandardmore restricted.Nevertheless,aprojectmaynotbeviableifitisnotpossibletobelow theR���� atleasttoanacceptablelevel.Similartootherriskmanagementoptions, theproposedmethodologyfollowsastrategicappraisalwhereareassessmentwill allowdefiningthebestmanagementoptions[3,7,12].Wheneverpossible,therisklevel shouldbedespicablealthoughsomeprojectsmaybeapprovedwithanacceptablerisk ifsupportedontheevidencethatfurtherreductionwouldbehighlydisproportionateto thebenefitgained. 3.Resultsanddiscussion Themodelwasappliedtoacasestudy,agolfcoursethatintendstoreusewaterfor irrigation.Thecourseislocatedinanareaclassifiedasvulnerabletonitratepollution. Thehydrogeologicalconditionsdeterminethatisalocalwithahighinfiltrationrate forgroundwaterandthereisanaquiferwithsomeclayprotection,intheareaof thesportsfield.Theaquiferisalsoclassifiedasastrategicreserveforpublicwater DOI10.18502/kms.v7i1.11623 Page199
KnEMaterialsScience FibEnTech21 supply.BothsurfaceandgroundwaterpresentGoodStatusaccordingtotheRiver BasinManagementinforce.Theeffluentstreatmentlevelinplaceisasecondary plusdisinfection(UV),andaccordingthemonitoringdata,fromtheEuropeanPollutant ReleaseandTransferRegister,thetreatedwastewatersalsopresentanannualaverage belowthelimitofquantificationforDi(2-ethylhexyl)phthalate(DEHP).Themethodology wasusedtodefinethequalitystandardstobeappliedtonitrogenandDEHPandthe possibleneedsofadditionaltreatment,takingintoaccountthatnobarriersareinplace. FromtheabovedescriptionispossibletodefineHazard(Hz)levelforDEHP,whichis equaltothree(3),andfornitrogen,sincenonutrientremovalisinplace,theH�� levelis nine(9),Thehydrogeologicaldescriptionallowstounderstandthatpartialvulnerabilities forsurfaceandgroundwaters(Vp���� andVp���� )are2and6,respectively.Bythe applicationofequation1andtable2,ispossibletoobtainavalueofseven(7)tothe V����.Theabsenceofbarriersdeterminesaf���������� thatmatchesthemaximumlevelof importance(9)andasinglescenarioofexposure,leadingtoaglobalvulnerabilityvalue equaltoseven(7).Inthesameway,theabsenceofbarriersdeterminesan“almost certain”likelihoodofexposureoccurrence,whichtranslatestoavalueoffive(5).The waterbodyasmentionedpresentsagoodstatus,hasadefinedusesinceisareservefor drinkingwaters,andisalsoclassifiedasvulnerabletonitratepollution,whichdetermines theseverityofdamagewithamajorlevelwithavalueoffour(4).Therefore,thepartial damage(d��)revealsavalueofnine(9)andtheglobaldamagewillthenbeequaltoone (1).Allresultsarepresentedintable7whereispossibletoseethatfortheconsidered hazards(DEHPandN),theriskassessmentrevealsadespicablelevelforDEHP(2,3) andanunacceptablelevelfornitrogen(7,0).Consequently,intermsofDEHPtherisk leveldefinesthatthereisnoneedtoestablishaqualitystandardforthisparameter. However,fornitrogen,anincreaseoftreatmentlevelcouldbedesirable.Adefinitionof aqualitystandardlevelequaltoorbelow5mgL−1 willresultinadespicableriskwhile standardequaltoorbelow15mgL−1 willpromoteanacceptablerisk.However,thefinal solutionshouldbeadoptedbasedonanitrogenbalancestudy,sincenotallthenitrogen inthereclaimedwatersisimmediatelyavailableforconsumptionbythecrop,namely theorganicfractionwillonlybeaccessibleafterthemineralizationprocess,whichnot onlydependsonthetreatmentlevelbutalsotheretentiontimeinthestoragesystem. Hence,besidesthepreviousriskassessment,thefinalqualitystandardtobedefined shouldtakeintoaccountthemaximumamountofnitrogenfromreclaimedwatersthat canbeadsorbedbythecrop(grassandotherornamentalcropsonthegolfcourse)to minimizetheuseofsyntheticfertilizers[13]. DOI10.18502/kms.v7i1.11623 Page200
KnEMaterialsScience FibEnTech21 Table 7: Riskassessmentresults Hazard V���� Damage Risk RiskLevel Nitrogen 9 7 1 7,0 Unacceptable Nitrogen(reassessmentoption1) 7 5,4 Acceptable Nitrogen(reassessmentoption2) 1 0,8 Despicable DEHP 3 2,3 Despicable Ifapost-chlorinationisproposed,theuseofDBPformationmodelscanalsobeused topredictpossiblerisklevelsforthesetypesofpollutants[14].Forinstance,usingthe modeldevelopedbyotherauthors[14],theuseofatypicalchloridedoseof5mg L−1 andareactiontimebetween5to15minwillinduceaformationoftrichloromethanefrom 3,7a4,6µg L−1,abovetheEQSof2,5µg L−1,previewedontheDirective2008/105/EC and2013/39/UE.TheseresultsreflectaHzofmaximumleveland,thus,anunacceptable risk.However,isquitecommontheuseofaLoQforthissubstancebelow5µg L−1,and realsamplingresultsmayresultinadespicablerisk.Thus,specialattentionshouldbe paidtoLoQandEQSwhenresultsaredisplayedasbelowLoQandfurtherresearch couldbeusefultoimprovethemodelforthistypeofpollutants,namely,toapplyto centralizedsystemsforamoresustainableurbanwatermanagement[15]. 4.Conclusions TopromoteandincreasewaterreusepracticesinEuropeandPortugal,newpolicies, supportedontheinternationalguidelines,suchasISOstandards,wereadoptedandone ofitsmostcriticalfeaturesistheapplicationofaflexibleapproachwithoutjeopardizing thehealthandenvironmentalsafety.Themainstrengthoftheproposedmodelisits simplicity.Theapplicationofthemethodologytoacasestudyallowedtodemonstrate itsapplicabilityandrespectivestrengths,suchastheuseofastrategicassessment, thatallowstoevaluatetherisksinvolvedineachwaterreuseprojectforsurfaceand groundwaterandhelpsauthorities,withsimpleoutputs,onthevalidationprocessofthe appropriatequalitystandardstobenotedonwaterreusepermitsand,subsequently, helpsthemonthedecision-makingprocessnamelyontheimpositionofminimization measures.Althoughthemodelallowsthedeterminethequalitystandardsforreclaimed waters,theseresultsshouldalwaysbeseenwithothermanagementoptions,namely fornutrientstominimizetheuseofsyntheticfertilisers. DOI10.18502/kms.v7i1.11623 Page201
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