CarbonFibreReinforcementofCeramicWaterFilters by DianaNicholson AThesis Presentedto TheUniversityofGuelph Inpartialfulfillmentofrequirements forthedegreeof MasterofAppliedSciences in EnvironmentalEngineeringandInternationalDevelopmentStudies Guelph,Ontario,Canada DianaNicholson,August2012
DianaRachelleNicholson UniversityofGuelph,2012 ABSTRACT CARBONFIBREREINFORCEMENTOFCERAMICWATERFILTERS Advisor: ProfessorEdwardMcBean Thisresearchstrivedtoexaminethepotentialforcarbonfibretoimprovethestrength characteristicsofceramicwaterfilters(cwfs)toimprovetheirlengthofuseinthefieldwhile maintaining,orimproving,existingflowandbacteriaattenuationcapabilities.model@scalecwf discsweremadeexploringseveralconfigurationsofcarbonfibrereinforcementandweretested forflow@throughrates,ecoliattenuation,andequi@biaxialflexuralstrength.itwasdetermined that,whiletheparticularcarbonfibreconfigurationsexploredinthisstudydidnotincreasethe strengthofthecwfdiscs,theydidprovidebenefitssuchasimprovingflow@throughrateswhile minimallydetractingfrombacteriaremoval.thisindicatesthatthereinforcementofcwfshas potentialandfurtherresearchshouldbeconductedtodetermineanappropriatereinforcement configurationtoimprovetheirstrengthcharacteristics.giventhatcwfsaregainingmore widespreaduseinmanycountriesworldwide,extendingtheirlifespanofusewouldhave significantvalue.
Acknowledgements Iwouldliketothankmyadvisor,Dr.EdwardMcBean,fortheguidance,advice,andlightningfast responsetimehehasprovidedmethroughoutthepasttwoyears.iwouldalsoliketothanka numberofpeoplewithoutwhomthiswouldnothavebeenpossible:mirnaderghazali,joanne Ryks,RyanSmith,BarryVerspagen,CarlyGenn,JordanVallis,BillMorton,andSteveWilson.I wouldliketosayaspecialthankyoutobarrday,inc.ofcambridge,ontarioandthecanadian WildRiceMercantileofThunderBay,Ontariofortheirgenerousdonationsofcarbonfibreand ricehulls,respectively. Tomyfriendsandfamily(new,old,andreacquainted):thankyouforyourencouragementand support. iii
TableofContents 1. Introduction...2 1.1. ResearchObjectives...3 1.2. ThesisOrganization...3 1.3. References...4 2. LiteratureReview...7 2.1. CurrentStateofDrinkingWaterAccessWorldwide...7 2.1.1. TheRolesofPOUWaterTreatment...9 2.1.2. POUWaterTreatmentTechnologies...10 2.1.3. FiltrationTechnologies...10 2.2. CeramicWaterFilters...12 2.2.1. EffectivenessofCeramicWaterFilters...14 2.2.2. OperationalIssueswithCWFs...17 2.3. FibreReinforcedCeramicMatrixComposites...18 2.3.1. FactorsAffectingStrengthening...22 2.3.2. FlexuralTestingofFibre@ReinforcedCeramics...24 2.4. VibrioCholeraeattenuationbyCeramicWaterFilters...26 2.4.1. CausesandSymptoms...28 2.4.2. PreventionandControlMeasures...30 2.4.3. RemovalofVibrioCholeraefromDrinkingWater...31 2.5. TheUseofCeramicWaterFiltersinEmergencyResponse...32 2.6. References...39 3. StudyDesignandMethods...48 3.1. CeramicWaterFilterDiscDesign...48 3.2. FlowRateTesting...52 3.3. BacteriaAttenuationTesting...54 3.4. Equi@biaxialFlexuralStrengthTesting...59 3.5. Limitations...62 3.6. References...63 4. Results...65 4.1. StudyObjectives...65 4.2. Results...66 4.2.1. FlowTestData...67 4.2.2. BacteriaAttenuationData...71 4.2.3. Equi@biaxialFlexuralTestData...79 4.3. References...86 5. ConclusionsandRecommendations...88 5.1. Summary...88 5.2. Conclusions...89 5.3. Recommendations...91 iv
ListofTables Table2@1:SummaryofworldwidetestingonCWFsfrom2000@2010(modifiedfromSimonisand Basson,2011)...16 Table3@1 CWFDiscDesignScenarios...48 Table4@1:CWFDiscRecipes...66 Table4@2:Summaryofflowtestdata...68 Table4@3:SummaryofEcoliattenuationdata...72 Table4@4:Summaryofmeansamplettestsbetweendisctypes...72 Table4@5:Summaryofequibiaxialflexuraltestresults...81 ListofFigures Figure2@1:CeramicWaterFilterSchematic...13 Figure2@2:ExampleofaCeramicWaterFilter(Murphyetal.,2009,Brown,2007)...14 Figure2@3:Schematicshowingvarioustypesofreinforcement:(a)particles,(b)platelets,(c) whiskers,(d)unidirectionalcontinuousfibres,(e)cross@plycontinuousfibres,and(f) woventowsoffibres.(a)to(d)showplanviewwhile(e)and(f)areedgeviews. (SmithandYeomans,nodate)...20 Figure2@4:Comparisonofstress@straincurvesforbendinginglassandcarbonfibre@reinforced glass(davidge,1987)...22 Figure3@1:RiceHullsbeforemilling(left)andafter(right)...49 Figure3@2:Themixeddryingredientsbeforewaterisadded...50 Figure3@3:Discsair@dryingpriortofiring...51 Figure3@4:Mufflefurnaceusedforfiringdiscs...52 Figure3@5:Discsafterfiring...52 Figure3@6:ApparatusfortestingCWFdiscs...53 Figure3@7:Flowtestapparatusset@up...54 Figure3@8:Serialdilutionsandpetridishesforplatingsamples...57 Figure3@9:Membranefiltrationlabequipmentset@up...58 Figure3@10:ExampleofEcolicoloniesafterincubation(NDCright,countablecoloniescentre, andtntcleft)...59 Figure3@11:Sectionviewofbasicequipmentsetupforequibiaxialtesting(ASTM2009)...60 Figure3@12:Loadingfixturefortheequibiaxialflexuralstrengthtesting...61 Figure3@13:Equibiaxialflexuraltestsetup...62 Figure4@1:FlowRateVariationbyWeightofCarbonFibreperDisc...70 Figure4@2:FlowRateVariationbyIndividualCarbonFibreLengths...71 Figure4@3:GraphicalrepresentationofEcoliattenuationresults...73 v
Figure4@4:PercentRemovalofEcolibyDiscType...75 Figure4@5:PercentEcoliRemovalbyWeightofCarbonFibreperDisc...76 Figure4@6:PercentEcoliRemovalbyLengthofIndividualCarbonFibres...77 Figure4@7:Discweightvs.logreductionvalue...78 Figure4@8:Flowratevs.logreductionvalue...79 Figure4@9:Typicalload@extensioncurve...80 Figure4@10:Typicalfaileddiscpoststructuraltest...80 Figure4@11:Equi@biaxialFlexuralStrengthbyWeightofCarbonFibreperDisc...82 Figure4@12:Equi@biaxialFlexuralStrengthbyLengthofIndividualCarbonFibres...83 Figure4@13:Brokendiscshowingsurfacecracksanddisbondedcarbonfibre...85 ListofAppendices AppendixA:CarbonFibreSpecificationSheet AppendixB:CompleteDataSet vi
ChapterOne: Introduction 1
1. Introduction AccordingtoUNICEFandtheWorldHealthOrganization(WHO),theMillenniumDevelopment Goal7C,tohalveby2015,theproportionofthepopulationwithoutsustainableaccesstosafe drinkingwater,hasbeenreachedasof2010.however,hugedisparitiesexistbetweenaccessby therichversusthepoor.additionally,780millionpeople,morethanonetenthoftheglobal population,stilldonothaveaccesstoapotabledrinkingwatersource.(unicefandwho,2012) Withoutdirectaccesstowaterinthehome,watermustbecollectedelsewhereandthen transportedto,andstoredin,thehomepriortouse.microbialcontaminationofwaterduring thecollection,transportation,andstorageofwaterislikely.anumberofstudieshaveshown thatwaterstoredinthehometendstobemorecontaminatedthanthesourcewater(wrightet al.,2004;clasenandbastable,2003;jagalsetal.,2003).householdorpoint@of@use(pou)water treatmenttechnologieshavebeenidentifiedassuccessfulinterventionsforfillingtheservice gapofprovidingpotablewatertohouseholdswherecentralized,pipedwatersystemsarenot possible,orwherewateriscollectedelsewhereandstoredinthehome(thompsonetal.,2003; Sobsey,2006).AccordingtoaWHOreview,decentralized,simple,low@costwatertreatment interventionsarecapableofdramaticallyimprovingthemicrobialwaterqualityatthe householdlevelandreducingtheriskofdiarrhealdisease(sobsey,2002;who,2007). Theresearchpresentedinthisthesisinvolvestheinvestigationandmodificationofawidely usedpouwatertreatmenttechnology,theceramicwaterfilter(cwf).thesefiltershavebeen showntobeeffectiveatattenuatingpathogensfromdrinkingwaterandreducingtheincidence ofdiarrhealdisease,however,thecwfstypicallyonlylastapproximatelytwoyearsmainlydue 2
tobreakage,eitheroftheceramicfilterelement,thespigot,orthecontainercoupledwith limitedavailabilityofreplacementpartsincommunities.(brown,2007)thisresearchspecifically focusesonmodifyingthecwfrecipebyaddingcarbonfibrereinforcementinordertoattempt toimprovethemechanicalcharacteristicsoftheceramicfilterelementandimproveitslengthof useinthefield.giventhatthesefiltersaregainingmorewidespreaduseinanumberof countriesworldwide,extendingtheirlifespanofusewouldhavesignificantvalue.thisresearch willaddtothepresentliteratureexaminingcwfsandtheuseofadditivesineffortstoimprove theircharacteristics. 1.1. ResearchObjectives Thisresearchstrivestoexaminetheuseofarecipeadditive,carbonfibre,toimprovethe mechanicalcharacteristicsofcwfswhilemaintainingorimprovingexistingflowandbacteria attenuationabilities.therearefourprimaryobjectivesofthisresearch: 1. Createmodel@scaleCWFdiscsexploringseveralrecipes; 2. Assessimplicationstoflow@throughrates; 3. PerformE.coliattenuationtestingontheCWFdiscstodeterminebacteriaremoval characteristics;and, 4. PerformstructuraltestingontheCWFdiscstodeterminestrengthcharacteristics. 1.2. ThesisOrganization Thisthesisconsistsofthefollowingchapters: 3
Chapter2: LiteratureReview Thischapterpresentsaliteraturereviewondrinkingwaterresourcesinthedevelopingworld, CWFsandtheircurrentuse,fibre@reinforcedceramics,CWFuseinemergencyreliefandCWF andcholeraattenuation,asapplicabletothecurrentresearch. Chapter3: StudyDesignandMethods Thischaptersummarizesthestudysetupanddesignandthedatacollectionmethodsusedin thisresearch. Chapter4: Results Chapterfourpresentstheresultsfromtheflow,E.coliattenuationandequibiaxialflexural strengthtestsperformedonthecwfdiscs.statisticalrelationshipsbetweenvariousfactorsare examined. Chapter5: ConclusionsandRecommendations Thefinalchapterofthisthesissummarizesthefindingsoftheresearchpresentedandprovides overallrecommendationsandareasofapplicablefutureresearch. 1.3. References Brown,J.M.(2007).Effectiveness*of*Ceramic*Filtration*for*Drinking*Water*Treatment*in* Cambodia.Unpublished.DoctorofPhilosophy.UniversityofNorthCarolina.ChapelHill. Clasen,T.F.,andBastable,A.(2003).Faecal*contamination*of*drinking*water*during*collection* and*household*storage:*the*need*to*extend*protection*to*the*point*of*use.journalofwater andhealth.01:109@115. 4
Jagals,P.,Jagals,C.,andBokako,T.C.(2003).The*effect*of*container?biofilm*on*the* microbiological*quality*of*water*used*from*plastic*household*containers.journalofwaterand Health.1(3):101@108. Sobsey,M.(2002).Managing*water*in*the*home:*accelerated*health*gains*from*improved*water* supply.who/sde.wsh/02.07.who,geneva,switzerland. Sobsey,M.(2006).Drinking*water*and*health*research:*a*look*to*the*future*in*the*United*States* and*globally.journalofwaterandhealth04:s17@s21. Thompson,T.,Sobsey,M.,andBartram,J.(2003).Providing*clean*water,*keeping*water*clean:* an*integrated*approach.internationaljournalofenvironmentalhealthresearch.13:s89@s94. UNICEFandWHO.(2012).Progress*on*Drinking*Water*and*Sanitation:*2012*Update.NewYork, NewYork:UNICEF. Wright,J.,Gundry,S.,andConroy,R.(2004).Household*drinking*water*in*developing*countries:* A*systematic*review*of*microbiological*contamination*between*source*and*point?of?use. TropicalMedicineandInternationalHealth.9(1):106@117. 5
ChapterTwo:LiteratureReview 6
2. LiteratureReview 2.1. CurrentStateofDrinkingWaterAccessWorldwide AccordingtoUNICEFandtheWorldHealthOrganization(WHO),theMillenniumDevelopment Goal7C,tohalveby2015,theproportionofthepopulationwithoutsustainableaccesstosafe drinkingwater,hasbeenreachedasof2010.however,hugedisparitiesexistbetweenaccessby therichversusthepoor.additionally,780millionpeople,morethanone@tenthoftheglobal population,stilldonothaveaccesstoapotabledrinkingwatersource.(unicefandwho,2012) Inadequateaccesstopotabledrinkingwatercontributestothestaggeringburdenofdiarrheal diseaseworldwide.diarrhealdiseaseisendemicincommunitiesthatlackaccesstoimproved watersupplies.accordingtothewho,88%ofthe4billioncasesofdiarrheathatoccurannually areattributedtocontaminatedwaterandinadequatesanitationandhygiene(who,2007). Diarrhealdiseasesremainamongthetoptencausesofdeathinadultsoflowandmiddle@ incomecountries,andamongthetopthreecausesofdeathinchildrenundertheageoffive causingupto1.6 2.5milliondeathsperyear(Lopezetal.,2006;Koseketal.,2003).Drinking contaminatedwatercanalsoreducepersonalproductivetimewithwidespreadeconomic effects.diarrhealdiseasesareassociatedwithawiderangeofconsequences,including decreasedfoodintakeandnutrientabsorption,malnutrition,reducedresistancetoinfection, andimpairedphysicalgrowthandcognitivedevelopment, (CDC,2008).Additionally,water@ relateddiseasesmaypreventchildrenfromattendingschool,resultingin443millionmissed schooldaysperyear(undp,2006).problemsassociatedwithunsafedrinkingwaterare significantbarrierstodevelopment,bothhumanandeconomic. 7
Althoughdrinkingwaterisonlyoneofseveralpossiblepathwaysformostwaterborne pathogens,ithasbeenshownthatinterventionstoimprovewaterqualityaregenerallyeffective inreducingdiarrhealdiseaserates.therefore,microbialcontaminationofdrinkingwaterin communitieslackingimprovedwatersuppliesislikelytocontributesignificantlytotheburden ofdiarrhealdisease.evidencehasshownthatatleastaone@thirdreductionindiarrhealdisease morbiditymaybepossiblethroughtheuseofwaterqualityimprovementsalone(clasenet al.,2007).sobsey(2002)foundawiderangeofdiarrhealdiseasereductionsrangingfrom6 90%,dependingonthetypeofHWTintervention,exposedpopulationandlocalconditions.As such,theprovisionofpotabledrinkingwaterisclaimedtobethepovertyreductionintervention thathasthegreatestoverallimpactonnationaldevelopmentandpublichealth(who,2006). Centralizedwatertreatmentanddeliverysystemshavemanyadvantagesintermsofwater safetyandaccesshowevermaybedecadesawayfromimplementationinmanyareasofthe world.theinstallationofcommunalfacilitiessuchasboreholes,standpipes,andimprovedwells representamajorstrategyforsecuringaccesstoimprovedwatersourcesinareaswithout centralizedsystems.however,withoutdirectaccesstowaterinthehome,watermustbe collectedelsewhereandthentransportedto,andstoredin,thehomepriortouse.microbial contaminationofwaterduringthecollection,transportation,andstorageofwaterislikely.a numberofstudieshaveshownthatwaterstoredinthehometendstobemorecontaminated thanthesourcewater(wrightetal.,2004;clasenandbastable,2003;jagalsetal.,2003). Householdorpoint@of@use(POU)watertreatmenttechnologieshavebeenidentifiedas successfulinterventionsforfillingtheservicegapofprovidingpotablewatertohouseholds 8
wherecentralized,pipedwatersystemsarenotpossible,orwherewateriscollectedelsewhere andstoredinthehome(thompsonetal.,2003;sobsey,2006).accordingtoawhoreview, decentralized,simple,low@costwatertreatmentinterventionsarecapableofdramatically improvingthemicrobialwaterqualityatthehouseholdlevelandreducingtheriskofdiarrheal disease(sobsey,2002;who,2007).theyarebeingpromotedbecausetheyreducetheriskof contaminationbetweenthetimeofwatercollectionandconsumption. 2.1.1. TheRolesofPOUWaterTreatment POUwatertreatmenttechnologiesareanyofarangeofdevicesormethodsusedforthe purposesoftreatingwaterinthehomeoratthepointofuseinothersettings.mostpou technologiesareintendedtoreducemicrobialpathogens,althoughsomealsoreducechemical andradiologicalcontaminants.pousystemscomprisearangeofaccessibletechnologieswith thegoalofincreasingaccesstopotablewateratthelowestpossiblecosttoindividualsand communities.thesesystemsareincreasinglypromotedaspracticalsolutionstoproblemsof contaminateddrinkingwaterqualityinpoorareaswherecollectingwateroutsidethehomeand storingitforhouseholduseistypical(sobsey,2006).theuseofpousystemsmaycontributeto acceleratedhealthgains fromimprovedaccesstocleandrinkingwaterwherecentralized watertreatmentanddeliverysystemsareunavailableorinadequate(sobsey,2002). POUtreatmentisalsosuitedtocrisisinterventionswhereemergencysuppliesofpotablewater areneeded(curtisetal.,2000;mongetal.,2001;who,2005).breakdownsinwatersupply systemscanoccurasaresultofnaturaldisasters,warandhumanconflict,orsimplyinadequate maintenanceofinfrastructure(curtisetal.,2000).poutreatmentcanalsobeusedin 9
temporarysettlementssuchasrefugeecampsorshelters(robertsetal.,2001;who,2006; DoocyandBurnham,2006).ThistopicisexploredfurtherinSection2.5. 2.1.2. POUWaterTreatmentTechnologies KeyreviewsofPOUwatertreatmentandproperstoragetechnologieshaveadvancedthe currentknowledgeoftheseinterventionsandtheiruseinpoorareasofcountriesworldwide (Sobsey,2002;Lantagneetal.,2006;HIP,2006;IRC,2005).PhysicalmethodsforPOUwater treatmentincludeboiling,heating(usingfuelandsolar),filtering,settling,andultraviolet(uv) radiation(solarorultravioletlamps).chemicalmethodsincludecoagulation@flocculationand precipitation,ionexchange,chemicaldisinfectionwithgermicidalagents(primarilychlorine), andadsorption.combinations,ormultiplebarriers,ofthesemethodssimultaneouslyor sequentiallysuchascoagulationcombinedwithdisinfectionoftenyieldpromisingresults (Souteretal.,2003).Thesuccessoftheseinterventionsishighlycontextspecificwithnoone technologyormethodrepresentingauniversalbestsolution.availabilityofmaterials,qualityof rawwateravailable,culturalfactorsandpreferencesorcostmaydeterminewhereeachof theseismostsuited(sobsey,2002). 2.1.3. FiltrationTechnologies POUfiltrationtechnologiesincludeclothorfibrefilters,membranefilters,porousceramic filters,andgranularmediafilters.thesefiltersreducemicrobesbyacombinationofphysical andchemical(and,insomecases,biological)processesincludingphysicalstraining, sedimentationandadsorption.filtrationtechnologiesareincreasinglybeingusedinpoorareas 10
wherechemicaldisinfectionorboilingmaynotalwaysbepracticaloreffective(colwellet al.,2003). Traditionalmembranetechnologyisgenerallyexpensiveandthereforelargelyunknownfor small@scaledrinkingwatertreatmentindevelopingcountries.clothfilters,suchasthoseofsari cloth,havebeenrecommendedforreducingvc*inwaterwhentheseareassociatedwith copepodsorothereukaryotesinwater(colwelletal.,2003).theseclothswillnotsignificantly retaindispersedbacterianotassociatedwithcopepods,othercrustaceans,suspended sediment,orlargeeukaryotesbecausetheporesoftheclothfabric(>20μm)arenotsufficiently smalltoexcludebacteria,butwhereappropriatethesefilterscanhavesignificanthealth impacts. Granularmediafiltersincludethosecontainingsand,diatomaceousearthorothersusing discreteparticlesaspackedbedsorlayersofsurfacesthroughwhichwaterispassed.other granularmediafiltersarebiologicallyactivebecausetheydeveloplayersofmicrobesonthe surfaceoforwithinthegranularmediummatrix.thisbiologicallyactivelayerretainsmicrobes andoftenleadstotheirinactivationandbiodegradation.ahousehold@scalefilterwitha biologicallyactivesurfacelayerthatcanbedosedintermittentlywithwaterhasbeendeveloped calledthebiosandfilter,whichisanintermittentlyoperatedslowsandfilter(iossf)(stauberet al.,2006). 11
Onefiltrationtechnology,ceramicwaterfilters(CWF),hasgainedwidespreaduseasan inexpensivemethodtotreatmicrobiallycontaminatedwater.thefilterelementsaremadefrom porousfiredclayandcomeinavarietyofconfigurations. 2.2. CeramicWaterFilters Ceramicwaterfilters(CWF)areusedforpoint@of@use(POU)watertreatmentinmanycountries worldwideincludingcambodia,kenya,guatemala,nicaragua,ghana,etc.theyaremadefrom locallyavailableclay,sand,andanorganicmaterialsuchassawdustorricehusks.theorganic materialisusedtofacilitateflowratesthroughthefilterasitburnsoutduringthefiringprocess leavingbehindsmall,interconnectedpores.alayerofsilvernitrateorcolloidalsilverisapplied to the surfaces of the filter to provide an additional disinfection mechanism and to prevent growthofbacteriawithinthefilteritself(lantagneetal.,2010). Thepot@shapedceramicfilterelementisplacedinaplasticcontainerwithaspigottoprovidea proper storage reservoir as shown in Figure 2@1 and Figure 2@2. Water passes through the porous ceramic filter element by gravity at 1 to 3 L/hr, into the receiving container. Treated water is then dispensed from the receiving container by a tap to prevent post@filtration contaminationofthewater.theceramicfiltercanholdapproximately10lofwaterwhilethe plasticreceptaclestores20loftreatedwater. 12
Figure2W1:CeramicWaterFilterSchematic Locallyproducedceramicfiltershavetheadvantagesofbeinglightweight,portable,relatively inexpensive,andlow@maintenance.unlikechemicalorthermaldisinfection,ceramicfiltersdo notsignificantlychangewatertasteortemperatureanddoreduceturbidity:aesthetic improvementsthatmaybestrongmotivatorsforuseofthetechnologytotreathousehold water.(brown,2003;roberts,2004;clasenetal.,2004)therawmaterialsusedtomanufacture thefilterelementsaresourcedlocallywiththeexceptionofthesilversolution.silverisobtained fromaninternationalsupplier,yetrepresentsasmallfractionofthetotalcostofthefilter (aboutus$0.20perfilter).filterscostbetweenus$5andus$30andhaveanaveragelifespan oftwotothreeyears.(kallmanetal.,2011)aretrospectivestudyoffiltersdistributedin Cambodiafromtwolocalfilterfactoriesfoundthat:50%ofpeoplehadfunctionalfilters18 monthsafterdistribution,and20%hadfunctionalfilters36monthsafterdistribution.(brownet al.,2007)theceramicfilterelementsurfaceiscleanedthroughperiodicscrubbingtoreduce surfacedepositsthatslowfiltrationrates. 13
Figure2W2:ExampleofaCeramicWaterFilter(Murphyetal.,2009,Brown,2007) 2.2.1. EffectivenessofCeramicWaterFilters CWFsvarybyoveralldesign,productionmethod,clayandothermaterials,qualityassurance andqualitycontrolprocedures,typeofburnoutmaterial,firingtemperaturesandmethods, chemical(e.g.,colloidalsilver)amendmentsandapplicationmethod,flowrateconsidered acceptable,andmannerinwhichtheflowrateismeasured,andothercharacteristics. (Sobsey,2002;Cheesman,2003;Dies,2003;Lantagne,2010)Duetothefactthatthedesign, materialsavailable,andmethodsusedvariesfromcountrytocountryitisdifficulttomake generalitiesaboutcwfsasawhole.pathogenattenuationdataforonefilterdesignmaynotbe comparabletootherdesignsand,insomecases,separatebatchesfromthesamefactorymay vary. Pathogenattenuationviaceramicfiltrationmayinvolvetwoprimarymechanisms,physical removalandinactivation.filtrationbysizeexclusionremoveslargermicroorganismssuchas 14
protozoansandsomebacteriaandisattributabletotheinitialfilterporesizes.poresizesvary withceramicmaterial,organicmaterial,firingtemperatureandprocess,etc.surfaceassociation andthefiltercakethatdevelopswithfilterusemayalsoremovesmallerbacteriaandviruses. (Bielefeldtetal.,2009)Microbeorchemicalinteractionssuchassorptionwiththefilter s ceramicsurfacemayalsoeffectreductionsofkeycontaminants.additionally,theapplicationof silversolutionsincreasespathogenattenuationbyinactivatingbacteriaandvirusesand inhibitingbiologicalgrowthwithinthefilter.(lantagne,2001a) Several studies have quantified the CWF attenuation of bacteria, such as fecal coliform or Escherichia coli, which serve as indicators of pathogenic microorganism disinfection. Simonis andbasson(2011)createdasummarytable(table2@1)ofworldwidetestingdoneoncwffrom 2000@2010. 15
Table2W1:SummaryofworldwidetestingonCWFsfrom2000W2010(modifiedandadditional dataaddedtosimonisandbasson,2011) References Parameter Reduction % LRV(log 10 ) Remarks Dies(2001) Escherichiacoli >98 Katadynfilter Sagara(2000) Escherichiacoli NepaleseCWF Giardialamblia 4.6 Lantagne(2001) Cryptosporidium parvum 4.3 Totalcoliform 98.2 PottersforPeace(PFP)Nicaragua Fecalcoliform 97 Fecal streptococcus 82 Hwang(2002) Escherichiacoli 97.6 49PFPfiltersinNicaraguaover6 Totalcoliform 89.3 months Lantagne(2001), Escherichiacoli GM98 Brown(2007):90@99% Roberts(2004), Diarrhealdisease Mean46 Dukeetal.(2006) Totalcoliform 94@99.9 Terafilfilter(Low2002) AndHwang(2003) Escherichiacoli 88 WhiteClayCWF Dies(2003) Escherichiacoli >98 WhiteClayCWFwithcolloidalsilver Escherichiacoli >98 HongPhucCWF Coulbert(2005) Escherichiacoli 99.8 PozzaniCWF Franz(2005) Escherichiacoli 92@100 Tested5typesofcommercialfilters McAllister(2005) Bacteria 99 PFPwithcolloidalsilver Viruses 20 Clasenetal.(2006) Diarrhealdisease Mean39@44 VanHalem(2006) Escherichiacoli 3@6.8 Clostridumspores 3.3@4.9 Baumgartner Escherichiacoli 99.8 Filtronwithcolloidalsilver (2006) Totalcoliform 99.4 WSP(2007) Escherichiacoli upto98 1.7 Diarrhealdisease 50 Brown(2007) Escherichiacoli 1.8@2.4 Laboratorystudies Bacteriophage MS2 1.3@1.9 Oyanedel@Craver Escherichiacoli >97.8 andsmith(2008) Viruses >90 BrownandSobsey Escherichiacoli Mean99 2.1@2.9 (2010) Bacteriophage MS2 90@99 1.2@4.1 Murphy(2010) Escherichiacoli 0.5@2 SurfacewaterfieldtestsinCambodia Non@peerreviewedstudiesbyRoberts(2004),Lantagne(2001a),Dukeetal.(2006b),VanHalem (2006),Mattelet(2006)andothershavesuggestedthatlow@costceramicwaterfiltersdohave thepotentialtoprovidemicrobiologicallyimprovedwatertousersasindicatedbyareductionin surrogatesfordiseasecausingmicrobes.theaveragebenchmarkstandardforescherichiacoli 16
effectivenesswas97±3%,whereasvirustestingeffectivenesswaslimited.theattenuationdata thatexistsprovidesastartingpointforestablishingausefulguidelinefortestinglowcostcwfs andmakesitclearthatcwfs,usedatalocallevel,greatlyimprovethemicrobialqualityof householdwaterresultinginadramaticdecreaseindiarrhealinfectionratesanddeath. (SimonisandBasson,2011) 2.2.2. OperationalIssueswithCWFs Somepathogenattenuationstudiescompletedinthefieldhavefoundmorebacteriainthe effluentthaninthesourcewater.lantagne(2001)reportedeffluentwaterconcentrationsof 4900,4320,and1920CFU/100mLoftotalcoliform,fecalcoliform,andE.coli,respectively, comparedto124,70,and0intheinfluent.incambodia,17%ofallfiltersampleshadhigher concentrationsofecoliintheeffluentthanintheinfluent,someuptoa3@logincrease.(brown 2007)InastudycompletedinNicaragua,Hwang(2002)foundhigherEcoliandtotalcoliform concentrationsintheeffluentintwoandfour,respectively,of49filtersinhomes.thishasbeen attributedtobacteriagrowthintheplasticreceptacletank.thespigotisnotlocatedatthevery bottomofthetanksoitdoesnotdraincompletelywithnormaloperation,whichcouldallow regrowthofpathogensinthestagnantwater.(bielefeldtetal.,2009) Astudy(Brown2007)conductedover44monthsinCambodiareviewedtherateandreasonsfor filterdisuseoverthetestperiod.approximately2000householdfilterswereintroducedbytwo non@governmentalorganizationsinthreeprovincesbeginninginjuly2002.therateoffilter disusewasfoundtobeapproximately2%permonthafterthefilterswereimplementedandthe mainreasonwasduetobreakage,eitheroftheceramicfilterelement,thespigot,orthe 17
containercoupledwithlimitedavailabilityofreplacementpartsincommunities.otherreported reasonsfordisuseincludedthefilterbeingtoosloworotherwiseunabletomeetthehousehold drinkingwaterdemand,thefilterhadpasseditsrecommendedusefullifeasindicatedbythe manufacturer(somemanufacturersimprintan expirydate ontothesurfaceoftheirfilters) andsoitwasassumedtobenolongereffective,orusersgaveorsoldittoafriendorrelative. Onaveragefiltersareusedfortwoyears. 2.3. FibreReinforcedCeramicMatrixComposites Ceramicmaterialsoftenexhibitacombinationofusefulphysicalandmechanicalproperties, includinghighrefractoriness(abletoretainphysicalshapeandchemicalidentityathigh temperatures)andcompressivestrength.however,theirapplicationsarerestrictedduetotheir brittlebehaviour.(donaldandmcmillan,1976)thedevelopmentoffibre@reinforcedceramics waspromptedbytheneedformaterialswiththeadvantagesofceramicscombinedwith increasedtoughnessandtensilestrength,andareducedvariabilityofstrength.(phillips,1989) Theideaoffibrereinforcementingeneralsuggeststhatsignificantstrengtheningwillonlyoccur iftheelasticmodulus(theratioofaforceexerted linearstress totheresultantdeformation linearstrain)ofthereinforcingfibresisgreaterthanthatofthematrix,andiftensilestresses canbetransmittedfromthematrixtothefibres.iffibresoflowerelasticmodulusareused,the ultimatefailurestresswillbereducedbecausethematrix,ratherthanthefibres,willcarrya greaterproportionoftheappliedload.(bowen,1968;donaldandmcmillan,1976; Davidge,1987)Thematrixbondswiththefibres,protectsthemfromsurfacedamagedueto abrasionorcorrosion,separatesthefibresandminimizesthepropagationofbrittlecracks 18
betweenthefibres.stressesmaythenbetransmittedtothefibresthroughthebondwiththe matrixbyplastic(non@reversiblechangesofshape)orelastic(reversiblechangesofshape) deformationofthematrix.(donaldandmcmillan,1976)thefibrereinforcementmayalso increasethespallingresistanceofthematrix. Thereinforcingphaseinacompositematerialcanbepresentinanumberofdifferentformats: continuousfilament,shortfibre,platelet,sphereorirregular(figure2@3)andistypically classifiedbylengthandlayoutwithinthematrix.(smithandyeomans,nodate)thedegreeof strengtheningabletobeachieveddependsonthelengthandorientationofthereinforcing fibres.thecompositeisstrongeralongthedirectionoforientationofthefibresandweakestina directionperpendiculartothefibre.therearegenerallythreeclassifications:continuousfibre, discontinuousfibreandrandomlyorientedfibres.acontinuousfibre@reinforcedcompositeis definedasacompositeinwhichthereinforcingphaseconsistsofacontinuousfibre,continuous yarn,orawovenfabric.(astmc1337)adiscontinuousfibre@reinforcedcompositeisdefinedas acompositeinwhichthereinforcingfibresarediscontinuouswithinthematrixorhaveoneor bothendsinsidethestressfieldunderconsideration.(astmd3878)randomlyorientedfibres consistoffibresthatarenotarrangedinadeliberatepatternwithinthematrix.discontinuous fibrescanberandomlyorientedwithinthematrix. 19
Figure2W3:Schematicshowingvarioustypesofreinforcement:(a)particles,(b)platelets,(c) whiskers,(d)unidirectionalcontinuousfibres,(e)crosswplycontinuousfibres,and(f)woven towsoffibres.(a)to(d)showplanviewwhile(e)and(f)areedgeviews.(smithand Yeomans,nodate) Continuousfibrereinforcementsbringaboutthelargestchangesinpropertiesduetothe homogeneityofthereinforcement.(smithandyeomans,nodate)thefibres,ideally,areatleast 15timeslongerthanthecriticallength(theminimumlengthnecessarysuchthattheentireload istransmittedfromthematrixtothefibres).thepropertiesofcontinuousfibre@reinforced compositesareveryanisotropicandfrequentlyspecialfabricationmethodshavetobeused. Morecomplexvariantsofthistypeincludemulti@layerlaminatesandwovenstructures. (Davidge,1987)Fordiscontinuousreinforcementthefibresareshorterthanthecriticallength andarethereforelesseffectiveinstrengtheningthematerial,howevertheycanbefabricated intocomplicatedshapesmorequickly,easilyandatalowercostthancontinuousfibre reinforcedcomposites.randomlyarrayedfibrereinforcementsaretheleasteffectivein 20
strengtheningthematerialsincetheproportionoffibresalignedinthedirectionofstressis reduced,howeverthematerialisisotropicandcheapertofabricate.(donaldand McMillan,1976;Davidge,1987)Additionally,somefibreswilllieapproximatelyperpendicularto thetensileaxisandmayactasstress@concentrationsites,particularlyifbondingisweak,thereby reducingthestrengthofthecomposite.(donaldandmcmillan,1976) Themainpurposeofreinforcingceramicsistoincreasestrengthintheformoftoughness. Toughnesshasbeendefinedastheabilityofamaterialtowithstandthermalandmechanical shockwithoutbreaking.(bowen,1968)the workoffracture isdefinedastheworkdoneper unitareainpropagatingacrack(donaldandmcmillan,1976)andisfrequentlytakenasa measureoftoughnessofamaterial.(bowen,1968)ceramicswithnoreinforcementexhibitlow workoffracturevaluesduetotheeaseatwhichcrackscanpropagatethroughthem.fibre reinforcementisabletolimitthegrowthofcracks,therebyincreasingtheworkoffracture,by restrictingthecracklengthtothedistancebetweenfibresand,wheretransversefibresbridge thecrack,bylimitingtheextenttowhichthecracksurfacescanseparatetothedegreeofelastic straininthefibres.(bowen,1968)anothercontributiontotheworkoffractureisthework requiredtopullthefibreendsoutofthematrixagainstthebondingforcesofthematrixtothe reinforcingfibres. Thechangeinthemechanicalresponseofceramicswithfibrereinforcementaddedisbelieved tobetheresultofacomplexmicrofailureprocessinthematrix.insuchcomposites,thefirst fractureeventisconsideredtobeaveryimportantpartofthebehavior,becausetheapplication rangeissometimeslimitedbythefirstfracturebehaviorofthecomposites.(gotoand 21
Kagawa,1994)Thestress@strainbehaviourofatypicalcompositeisshowninFigure2@4.The failurestrainofthematrixislessthanthatofthereinforcingfibresand,referringtothelettered pointsonthecurve,theusualsequenceofeventsisasfollows: A:initialcrackformationinthematrix, A@B:continuedmicrocrackingofthematrixtoformlongcracks(bridgedbyafibre), B:initialfailureofthefibrereinforcement,and B@C:stressrelaxationinbrokenfibrespluspulloutoffibresfromwithinthematrix. (Davidge1987;GotoandKagawa1994) Figure2W4:ComparisonofstressWstraincurvesforbendinginglassandcarbonfibreWreinforced glass(davidge,1987) 2.3.1. FactorsAffectingStrengthening Indesigningapracticalceramiccompositeanumberoffactorsneedconsidering:thermal expansionofthematrixandreinforcingfibres,chemicalcompatibility,andthenatureof interfacialbonding.(bowen,1968;caoetal.,1990)thedifferentialthermalexpansionofthe 22
matrixandreinforcingfibresisaveryimportantfactorincompositematerialsasitdetermines theresidualstress@straindistributionsafterfabricationandcanhavesignificanteffectsonthe resultantmechanicalproperties.(donaldandmcmillan,1976;caoetal.,1990)sincetheyare causedbytheinherentpropertiesofthecompositecomponents,theseresidualstressescannot beavoided.theymayresultinpositiveornegativeeffectsdependingontheirdirectionand magnitude.(kuntzetal.,1993)residualstressesinfluencematrixfractureintwoways:stresses paralleltothefibressuperimposedirectlyontotheappliedstressandmaycausematrixcracks, andstressesperpendiculartothefibresaffectthefrictionalforcesbetweenthefibresandthe matrix.(marshallandevans,1985;kuntzetal.,1993)ifthereinforcingfibrecontractsmorethan thematrix(providedthefibreremainsbondedtothematrix)thefibrewillbesubjectedtoa residualtensilestressandthematrixtoaresidualcompressivestressandviceversa.itis preferableifthethermalexpansionvalueofthereinforcingfibresandthematrixarekeptas similaraspossiblebut,ifnot,itispreferableifthethermalexpansionofthefibreisgreaterthan thematrixasthefibreismorecapableofwithstandingtensilestrains.(davidge,1987) Anotherconsiderationisthechemicalcompatibilitybetweenthematrixandthereinforcing fibres.thefibrediameterisanimportantparameterinthiscase:theratesofanychemical interactionsgenerallyincreasemarkedlywithdecreasingfibrediameterasthisincreasesthe interfacetovolumeratio.(davidge,1987)indesigningafibrereinforcedceramic,chemical compatibilityofthefibresandmatrixmayimposesevererestrictionsonappropriatematerial combinations.(bowen,1968) 23
Theinterfacialpropertiesbetweenthefibreandmatrixarecrucialindeterminingthe mechanicalbehaviourofacomposite.ifthematrixbondsverystronglytothereinforcingfibres, thecompositebehavesmoresimilarlytoanunreinforcedceramicandcrackswillbeableto propagateunimpededthroughthematrix.(donaldandmcmillan,1976)however,astronger fibre@matrixinterfacelowersthecriticallengthasitdependsontheinterfacialshearstress.a discretegapattheinterfaceoraweakenedinterfaceisideal,asthiswillcauseapropagating cracktodeflectlocallyalongtheinterfacesothatthematerialbehavesasa tough composite. (Davidge,1987)Aweakerfibre@matrixinterfaceallowsthestrengtheningmechanismssuchas fibrebridging,crackdeflection,matrixmicrocracking,fibredebonding,andfibrepull@outtobe combinedtoreduceresidualstressesandeliminatecatastrophicfailures.(donaldand McMillan,1976;Caoetal.,1990;Murthyetal.,1996)Aninterfacethatistooweakwillallow debondingtooccurtooreadily.acompromisebetweenaweakorstrongfibre@matrixmustbe reachedtoachieveoptimalstrengthening.(donaldandmcmillan,1976;davidge,1987; Chiang,2001) 2.3.2. FlexuralTestingofFibreWReinforcedCeramics Withinabrittlematerial,thereisamultitudeofmicroscopicstructuralandmaterialdefectsin theformofinterstitialcavities,fracturedparticles,inter@particularboundaries,etc.these defectsactasminutestressconcentrationsinthematerialandastheappliedloadisincreased, fracturewillinitiateandpropagatefromoneofthem.sincethedefectsarerandomly distributedthroughoutthematerialandareofrandomseverity,thereisaninevitableinherent variabilityinthestrengthofnominallyidenticalbrittlespecimensoverandabovethatwhich maybepresentbecauseofvariationsincompositionordetailsofmanufacture.(stanley,2001) 24
Duetotheirbrittlenature,bothunreinforcedandreinforcedceramicsaredifficulttotestin puretension,compression,orshear,primarilyduetodifficultiesingrippinganduniformly loadingthebrittlespecimen. Thetensilestrengthofthematerialcanbeverysensitivetoflawsanddefects,includingthose inducedduringspecimenfabricationaswellasstressconcentrationsinducedbythegripping method.purecompressivestrengthisdifficulttoobtainbecausebrittlematerialstendtobe muchstrongerincompressionthaninshear.eveninapurecompressiontest,theshearstresses thatoccurat45degreestothedirectionoftheappliedcompressiveforcemaycausepremature shearfailure.(adams,2008) Instead,aflexuraltestisoftenusedasthespecimensimplyrestsonasupportandisloadedin anappropriatemannerdependingonthespecimenshape.inaflexuraltest,thestressstateis neitherpure(itvariesfromtensionononesurfacetocompressionontheotherwithshear presentaswell)noruniform(itvariesalongthelengthofthespecimen).intheflexuraltest,a brittlematerialwillusuallyfailatitstensilesurfaceand,assuch,thetestmeasuresthetensile strength.thesensitivitytodefectsinthematerialisconfinedtothetensilesurfaceintheregion ofthehigheststressand,becausearelativelysmallvolumeofmaterialisinvolved,thetest resultstypicallyexhibitlessdatascatter.(adams,2008)examplesofflexuraltestconfigurations includeathree@pointtestorfour@pointtestforbeam@shapedspecimens,oraconcentricringon ringorballonthree@ballconfigurationfordiscshapedspecimens.itisessentialthatthe geometryandloadingofthetestconfigurationmustbesuchthatacalculablestressstate 25
prevailsatthesectionwherefractureoccurssothatthefracturestresscanreadilybecalculated fromthefractureload.(stanley,2001) Intheconcentricringconfiguration,thediscisuniformlysupportedonaconcentriccircularring andloadedbyasecondconcentricring.withinthecentralportionofthering@loaded,ring@ supporteddiscspecimen,thereisauniformequi@biaxialstressstatethatvarieslinearlyfrom tensiononthelowersurfacethroughzeroonthemid@surfacetocompressionontheupper surface.again,thevalueofthetensilefracturestressobtainedfromthistestisnottobeseen asstrictlyequivalenttothatobtainedfromothertestmethods;thevaluerelatestotheequi@ biaxialstressconditionandisreferredtoastheequi@biaxialtensilefracturestress. (Stanley,2001) 2.4. VibrioCholeraeattenuationbyCeramicWaterFilters Althoughtypicallyabsentfromwealthycountries,theglobalimpactofcholeraremains significant.theworldiscurrentlyexperiencingits7 th cholerapandemicandhasbeensince 1961.Withunstablerefugeeandinternallydisplacedpersonssituations,naturaldisasters,and lackofcleanwaterandsanitationinmanypartsoftheworld,thediseasehasreachedepidemic proportionsonsixcontinents.(colwell,2000)in2006,52countriesofficiallyreportedtothe WHOatotalof236,896choleracasesincluding6,311deaths,howeverthesenumbersdonot reflectthetrueburdenofcholeraduetolimitationsinthesurveillanceandnotificationsystems ofmanycountrieswherethediseaseisendemicaswellaswidespreadunderreportingdueto fearoftravelandtrade@relatedsanctions.(deenetal.,2008)thewho(2010)estimatesthere areactuallythreetofivemillioncholeracasesannuallycausing100,000to120,000deaths. 26
CholeraisanacuteintestinaldiseasecausedbythebacteriumVibrio*cholerae*O1orO139*(the twopathogenicstrainsareabbreviatedtogetheras VC ).VCexistasnaturalinhabitantsof aquaticecosystems,thusmakingthemfacultativehumanpathogens.(lobitzetal.,2000;reidl andklose,2002)thequantitiesofvcsuspendedinwateraregenerallylow(<50cfu/lforo1); howevervcmultipliesrapidlyinpoorlystoreddrinkingwaterandmaybefoundinlarge numbersattachedtoaquaticspeciessuchascyanobacteria,algae,zooplankton,and27articular (upto10 5 VCorganismsmeasuredattachedtotheirsurfaces).Thereexistsacorrelation betweencholeraoutbreaksandalgalblooms.(huqetal.,1996;reidlandklose,2002)the prevalenceofvchistoricallyispartlyduetoitsabilitytore@emergewithsignificantgenetic variation,givingrisetonewclonessuchas01eltorin1994ando139in1995and2002. (Gubala,2006)Itcausesdiseasebycolonizing,proliferatingandsecretingtoxinsintheintestine oftheinfectedperson.(wangetal.,2010)thistoxincauseswaterydiarrheaofsuchexceptional volumethathypotensiveshock(abnormallylowbloodpressure)anddeathcanoccurwithin12 hoursofthefirstsymptom.passageofvcthroughthehumangastrointestinaltractinducesa hyperinfectiousstatethatisperpetuatedevenafterbeingflushedintonaturalaquaticreservoirs forupto24hours.eradicationofcholeraisunlikelybecauseithasenvironmentalreservoirsthat willprobablycontinuetocausesporadiccasesforanindefiniteperiod.thetoxigenico1and O139strainssurviveinwaterbyenteringintoarestingstateknownas viablebutnot culturable (VNBC).CellsintheVBNCstatecanretaintheirviabilityandinfectivepotentialinthe environmentoverayearwhilealsomaintainingtheirassociatedpathogenicgenesalongwith theintegrityoftheirchromosomes.(chomvarinetal.,2007) 27
2.4.1. CausesandSymptoms Commonsourcesofinfectionincludecontaminateddrinkingwater,ice,orfood.Drinkingwater thathasbeencontaminatedatitssource(ex.byfecallycontaminatedsurfacewaterenteringan incompletelysealedwell)orduringstorage(ex.bycontactwithhandssoiledbyfeces),andice madefromcontaminatedwateraretypicalsourcesofinfection.anothermajorsourceisfood contaminatedduringorafterpreparation.(who,1994)seafood(particularlyshellfishtaken fromcontaminatedwaterandeatenraworinsufficientlycooked),andfruitandvegetables grownatorneargroundlevelandfertilizedwithnight@soil(humanexcrementcollectedatnight frombucketsandouthouses,sometimesusedasmanure),irrigatedwithwatercontaining humanwaste,orfreshenedwithcontaminatedwater,andtheneatenraw.(usfda,2001) VC*infectionresultsfromingestionoftheorganism.Dependingonthevulnerabilityofthe personwhohasbeenexposed,theincubationperiodforvc*infectioncanrangefrom12to72 hours.(naidooandpatric,2002)thesmallintestineistheprimarysiteofinfectionwithvcand isthesourceofthesecretorydiarrhoeaduringcholera.inpatientswithseverevcinfection,the volumeofsmallintestinefluidreachingthecolonfarexceedsthemaximumresorptivecapacity ofthecolon,whichissixlitresaday.thiscausestheprofusewaterydiarrheathat 28articular28ticholera.(Cashetal.,1974)Choleraisadiseasethatdoesnotdiscriminateonceit infiltratesaparticulararea.duringcholeraoutbreaksinnewlyaffectedareas,peopleofallages maycontractthedisease,however,choleraisamoreseverediseaseinpregnantwomen causinghighratesoffetallosseveninwomenwhoreceiveadequaterehydration.(bennish, 1994) 28
Inmorethan90%ofcases,choleraismild.PersonswhohaveingestedVCmayhaveno symptomsoronlymilddiarrhea.wherecholeraispresentbutnotepidemic(awidespread occurrenceinacommunityataparticulartime),itcausesfewerthan5%ofallcasesofacute diarrhea.(swerdlowandisaacson,1994)themostdistinctivefeaturesofcholeraarethe productionofavoluminouswaterystool.inpatientswithhighpurgingrates,thestoolinitially containsfaecalmatter,butquicklybecomeswhiteandopalescentwithafishyodour(commonly referredtoasricewater).vomitingcommonlyaccompaniesthediarrhoea,especiallyearlyin theillness.(naidooandpatric,2002)thispurgingcausesseveredehydrationinpatients recognizableby:anincreaseinpulserateandadecreaseinpulsevolume;hypotension;an increaseinrespiratoryrate;sunkeneyesandcheeks;drymucousmembranes;decreaseinskin turgor;adecreaseinurineoutput;lethargy;weakness;irritability;andthirst.someofthese symptomsarealsoobservedinmalnourishedchildren(decreasedskinturgor,sunkeneyes, lethargy)makingdiagnosisofdehydrationsometimesunreliableinpoorareas.(bennish,1994) Newer,rapiddiagnosticmethodsbasedondetectionofbacterialantigensorcholeratoxinin stoolsamplesarecurrentlybeingdevelopedandused.(gubala,2006;chomvarinetal.,2007) Themostimportanttreatmentofcholeraisrehydrationeitherintravenouslyororallyand consistsofpromptreplacementofthewaterandelectrolyteslostthroughtheseverediarrhea andvomiting.whenfluidsareadministeredearlyinthecourseofillness,theycanprevent dehydrationfromoccurring.whenadministeredlaterintheillness,afterdehydrationhas developed,theyareessentialforrestoringfluidbalanceandpreventingdeath.(naidooand Patric,2002)Insomecasesaneffectiveantibioticcanreducethevolumeofdiarrhoeain patientswithseverecholera,andshortentheperiodduringwhichvcisexcreted.inaddition,it 29
willusuallystopthediarrheawithin48hours,thusshorteningtheperiodof30articular30tion. (Rahmanetal.,1988)Antimicrobialtherapycanusuallyreducethelengthofthediarrhoeafrom aboutfourtosixdays(withouttherapy)toabouttwotothreedays.forinexpensive antimicrobialagents,thistypeoftherapycanbeextremelycosteffectiveasitreducesthe durationofhospitalstay,andreducesthevolumeofintravenousandoralfluidsrequiredfor hydration.(naidooandpatric,2002) 2.4.2. PreventionandControlMeasures Newoutbreaksofcholeracanoccursporadicallyinanypartoftheworldwherewatersupplies, sanitation,foodsafetyandhygienepracticesareinadequate.theinhabitantsofoverpopulated communitieswithpoorsanitationandcontaminateddrinkingwatersuppliesaremost frequentlyaffected.floods,earthquakesoranydisastersinpoorcountriesoftheworldare predisposedtocholeraoutbreaks.theonlysuremeansofprotectionagainstcholeraepidemics areadequatewatersuppliesandsanitation.(naidooandpatric,2002)accordingtothewho (1994),thereisnosubstitutefordrinkingonlypotablewater,practicinggoodpersonalhygiene, andpreparingfoodsafely.accesstopotablewaterisabasicrequirementforhealth,especially intimeswhencholerathreatens.sincecontaminatedwaterisacommonsourceofcholera infection,alleffortsmustbemadetoprovidepotabledrinkingwater,aswellaswaterfreefrom pathogensforfoodpreparationandbathing.aspreviouslydescribedinsection2.1,potable waterisnotalwaysreadilyaccessibleandtreatmentmustbedoneatthepoulevelbyboiling, disinfecting,filtering,etc.goodsanitationcanmarkedlyreducetheriskoftransmissionof intestinalpathogens,includingvc,especiallywherelackofgoodsanitationmayleadto contaminationofcleanwatersourcesandfood.highpriorityshouldbegiventoobservingthe 30
basicprinciplesofsanitaryhumanwastedisposal,aswellasensuringtheavailabilityofpotable watersupplies.appropriatefacilitiesforhumanwastedisposalareabasicneedofall communities;intheabsenceofsuchfacilitiesthereisahighriskofcholera.(naidooandpatric, 2002) Choleravaccinationshaverecentlybeendevelopedandareconsideredamongthetoolsto preventcholerainpopulationsbelievedtobeatriskofacholeraepidemicwithinsixmonths, andnotexperiencingacurrentepidemic.suchhigh@riskpopulationsmayinclude,butarenot limitedto,refugeesandurbanslumresidents.however,vaccinationsshouldbeundertakenonly inconcertwithothercholerapreventionandcontrolmeasures.(naidooandpatric,2002) 2.4.3. RemovalofVibrioCholeraefromDrinkingWater Asoneofthemainpreventionmeasuresforcholeraistheadequatesupplyofpotabledrinking water,investigatingtechnologiesormethodstoremovevcfromdrinkingwaterishighly relevant.afewstudieshavebeencompletedtodeterminepossibleattenuationmethodsforvc. BasedonthediscoverythatVCisfrequentlyassociatedwithzooplankton,astudy(Colwellet al.,2002)wasconductedusingasimplefiltrationmethodinvolvingasariclothfoldedfourto eighttimes.thissimplefilteriscapableofremovingzooplanktonandparticulates>20μm, effectivelyachieving99%removal(2log)ofvc.thestudywascompletedin65ruralvillagesin Bangladeshinvolvingapproximately133,000individualsfromSeptember1999throughJuly 2002anda48%reductionincholerawasobserved. 31
Aseparatestudy(Berneyetal.,2006)conductedtodeterminetheefficacyofsolardisinfection (SODIS)forentericpathogensincludingVCdeterminedthatthebacteriaareverysusceptibleto SODIS.VCweremeasuredtobetheleastresistanttosunlightandthemostsusceptibletomild watertemperatures(above40 C)oftheentero@pathogenicstrainsstudied. CWFshavebeenshowntoeffectivelyremoveEcolifromdrinkingwater.Ecoliisarod@shaped, gram@negative,flagellated,facultativebacillusabout2@4μmlongand0.6@1.0μmindiameter. (ZaritskyandWoldringh1978)VCisacomma@shaped,gram@negative,flagellated,aerobic bacilluswhosesizevariesfrom1@3μminlengthby0.5@0.8μmindiameter.(handa2010)dueto theirsimilaritiesitispostulatedthatcwfswillalsobeabletoeffectivelyremovevcfrom drinkingwater.duetosizeexclusion,cwfscaneasilyfilteroutzooplanktonfromwaterfurther addingtotheprobabilitythatvccanbeattenuatedbycwfs.additionally,ascholeraoutbreaks arecommonintimesofdisasterandemergency,cwfscouldbequicklymobilizedtohelp preventanoutbreakfromoccurring.thisconceptisfurtherdiscussedinsection2.5. 2.5. TheUseofCeramicWaterFiltersinEmergencyResponse Adisasterisdefinedasaseriousdisruptionaffectingacommunityorpopulationcausingdeaths, injuries,ordamagetoproperty,livelihoods,ortheenvironmentandthatexceedstheabilityof theaffectedcommunitytocopeusingitsownresources.naturaldisastersincludeearthquakes, floods,windstorms,famine,droughts,epidemics,massdisplacementofpeople,andconflicts. (Iain2010)Aspopulationdensitieshaveexpandedandthenumbersofpeoplelivinginareas pronetonaturaldisasterhavemultiplied,theimpactofdisastershasincreased.(aghababian 32
andteuscher,1992)additionally,climatechangeandenvironmentaldegradationarechanging theoccurrenceofweather@relatedhazardssuchasfloods,droughtsandstorms.(iain,2010) Whiledisastersthreateneveryone,inpractice,theyproportionallyhurtpoorcountriesmore thanwealthycountries.(iain,2010)inresource@richcountrieswithadequatepublichealth infrastructure,post@disasterinfectiousdiseasesurveillancehasonlyoccasionallydetected relativelysmallincreasesinlifethreateninginfectiousdiseasesafternaturaldisasters.in comparison,inresource@poornations,largeroutbreaksofinfectiousdiseases,includingcholera, typhoid,acuterespiratoryinfectionsandleptospirosisafterdisastersarenotinfrequent.(ivers andryan,2006)forexample,high@incomecountriesaccountfor39%oftheexposuretotropical cyclonesbutonly1%ofthemortalityrisk,whereaslow@incomecountriesrepresentonly13%of theexposurebut81%ofthemortality.(iain,2010) Theavailableliteratureondisastersindicatesthatepidemicsofcommunicablediseasesdonot alwaysoccurafternaturaldisasters.iftheydooccur,itisusuallynotthenaturaldisasteritself butthesecondaryeffectsofdisasters,suchasdestructionofwater,sanitationandhealthcare services,overcrowdingandpopulationdisplacementintoartificial,crowdedcommunitiesthat mayleadtoincreasedinfectiousdiseases.(wilder@smith,2005;howardetal.,1996;watsonet al.,2007)naturaldisasters(regardlessoftype)thatdonotresultinpopulationdisplacementare rarelyassociatedwithoutbreaks.(watsonetal.,2007) Displacedpopulationsincampsettingsareathighriskofinfectiousdiseasesduetothe secondaryeffectsofdisastersmentionedabove.deathratesofover60timesthebaselinehave 33
beenrecordedinrefugeesandinternallydisplacedpeople,withoverthree@quartersofthese deathscausedbycommunicablediseases.(wilder@smith,2005)epidemicpronediseasesin refugeesettingsarediarrhoealdiseases,respiratoryinfections,measles,meningitisand, dependingonthecountry,malaria.hiv/aidsandtuberculosisarealsobecomingincreasingly important.(wilder@smith,2005)diarrhoealdiseasesareamajorcauseofmorbidityand mortalityindisasters.incampsituations,diarrhoealdiseaseshaveaccountedformorethan40% ofthesedeathsintheacutephaseofanemergency,withover80%ofthesedeathsoccurringin childrenagedlessthantwoyears.(wilder@smith,2005) Outbreakinvestigationshaveshownthatcommonsourcesofinfectionsincludepollutedwater sources(byfaecalcontaminationofsurfacewaterenteringincompletelysealedwells), contaminationofwaterduringtransportandstorage(throughcontactwithhandssoiledby faeces),sharedwatercontainersandcookingpots,scarcityofsoapandcontaminatedfoods. (Wilder@Smith,2005)Therefore,themostcommonexposurepathwaycausingdiarrhoeal diseasesisthefaecal@oralpathway.lackofcleanwater,overcrowding,insufficient understandingofpersonalanddomestichygiene,nutritionaldeficiency,andoverallpoor sanitationarethemajorcontributingfactorsforthespreadofdiarrhealdiseases.(duet al.,2010) Potabledrinkingwaterisanimmediatepriorityinemergencies.Whennormalwatersupplies areinterruptedorcompromisedduetonaturaldisasters,complexemergenciesoroutbreaks, affectedpopulationsareoftenencouragedtoboilordisinfecttheirdrinkingwatertoensureits microbiologicalintegrity.recently,pouwatertreatmenttechnologiesverifiedinthe 34
developmentcontexthavebeenrecommendedforuseinemergenciessuchassodium hypochlorite,flocculant/disinfectionpowder,sodis,cwfandbiosandfiltration.these technologiesmaybeespeciallyeffectiveduringtheinitialphaseofanemergencywhen responderscannotyetreachtheaffectedpopulationwithlonger@termsolutions.(lantagneand Clasen,2009)However,themajorityofresearchonPOUtechnologieshasoccurredinthe developmentcontext,andnottheemergencycontext.differencesbetweenthesetwocontexts mayimpacttheeffectivenessofpoutechnologiesinemergencyresponse. CWFhavebeenshowntobeeffectiveinthedevelopmentcontext;however,theyhavenotbeen widelyevaluatedinemergencies.threearticlesdescribingcwfinterventionsinemergencies werereviewedincludingareportfromfromthedominicanrepublicafterfloodingin2003 (Clasen,2006a),fromHaitiafterfloodingin2003(Caens,2005)andfromSriLankaafterthe tsunamiin2004(palmer,2005).additionally,adocumentsummarizingthebestpractices learnedbypottersforpeacefromestablishing17filter@manufacturingfacilitiesworldwide (Lantagne,2006a)wasalsoreviewed.Thefollowingsummarizesthemainlessonslearnedfrom theseinterventionsaswellasinterventionsofotherpoutechnologiesthatareapplicable. 1) CWFcanbeaneffectiveinterventioninsomeemergenciestoimprovewaterquality CWFhavebeenshowntobeeffectiveatimprovingwaterqualityandreducingthe incidenceofdiarrhealdisease.themicrobiologicalimprovementofwaterdocumented inthedominicanrepublicinterventionsuggeststhattheseimprovementscanalsobe seeninemergencyandpost@emergencycontexts.(clasen,2006a) 35
2) CWFshouldonlybeusedinanappropriateemergencysituation CWFappeartobemoreeffectiveaftertheacuteemergencyhaspassedwhenrecipients aremovingfromtransitionaltomorepermanentlivingstructures.asenseof permanencyallowsformoretimeandreceptivitytotrainingontheoperationand maintenanceofthefilters.inthesrilankatsunamiintervention,lackoflivingspacewas identifiedasabarriertotheiruse,andrecipientslivinginanemergencysheltertypewas associatedwithhavingagreaternumberofproblemswiththefilter.(palmer,2005) Additionally,CWFinterventionsshouldbetargetedtocontextsmostatriskof waterbornediseasebasedonemergencytypeandstage,locationandsituation. (LantagneandClasen,2009) 3) UserpreferenceshouldbeconsideredwhendecidingwhatPOUtechnologyto implement Asuseracceptanceandtraininghavebeenidentifiedasthemostdifficultfactorsin implementationitisanticipatedthatifuserpreferencewereconsideredintheoption selectiondecisionthatuseracceptabilityofthechosenproductwouldincrease. (LantagneandClasen,2009) 4) Trainingiscrucialforproperusageandmaintenance Inthedevelopmentcontext,higherlevelsofuseradoptionhavebeendocumented whenpoutechnologiesarepromotedinschoolsorhealthclinicsandwhenmotivational interviewingandsocialmarketingareemployedasbehaviourchangecommunications strategies.(lantagneandclasen,2009)whileitcanbemoredifficulttoconductin 36
emergencies,trainingisanecessarycomponentoftheemergencyimplementation strategy.trainingwasidentifiedasafactorcontributingtothehigherusageofcwfin boththesrilankatsunamianddominicanrepublicfloodinginterventions.althoughthe trainingwasnotextensive,andfollow@upvisitswerenotneededtoensurecontinued usage,sometrainingattheoutsetonoperationandmaintenanceofthefilterswas identifiedas vital.(palmer,2005;clasen,2006a)itshouldbenotedthatallrecipients mustbeprovidedwithallthematerialsnecessarytouseandmaintainthecwf includingthefilterelement,plasticreceptacle,brushforcleaningtheelement,etc.in thedevelopmentcontext,pouwatertreatmenttechnologyinterventionsselect culturallyappropriateoptions,distributetheproductsreliablyandworkwithtrusted localcommunityeducatorstoencouragehealthywaterpractices.itappearsasifthese factorstranslateintotheemergencycontextanditisrecommendedthatmaterialsbe developedspecificallyfortheemergencycontexttoassistorganizationsinconducting thetrainingnecessarytoensureprojectsuccess.(lantagneandclasen,2009) 5) Continuedusepost@emergencyaswellasbeyondcanoccur Iftheabove@mentionedfactorsareimplementedinemergencyinterventions,continued useofthepoutechnologycanoccurpost@emergency.infollow@upstudiesconductedin communitieswherecwfweredistributed,itwasfoundthatinonesrilankantsunami responsecommunity,23%ofpeoplewereusingtheceramicfilterthreemonthsafter distribution,inthedominicanrepublic,48.7%ofhouseholdshadcorrectlyoperating filters16monthsafterdistributionwith54%ofwatersamplesfromoperatingfilters (26.1%oftotal)freeofthermotolerantcoliform.(Palmer,2005;Clasen,2006a)InHaiti, 37
usersexpressedadesiretocontinueusingthefilter.(caens,2005)thesestudies highlightthataone@timedistributionofcwfaccompaniedwithtrainingcanleadtothe long@termusageofpouwatertreatment. 6) Adequateproductstocksarenecessaryforemergencyresponse TheabilitytoobtainanddistributeCWFiscriticaltointerventionsuccessin emergencies.additionally,theimportanceofaccesstoreplacementcwfpartsfor recipientsinpost@emergencysituationsdependsontheprojectgoalsoftheorganization andthetypeofemergencyandthereforemaybeconsideredeitherunimportantor vital.intheinstanceswherethegoalistoprovideemergencyreliefthattranslatesinto long@termdevelopmentinterventions,establishingareplacementpartsupplychainis necessaryforthesustainabilityofsuchaproject.ithasalreadybeenshownthatthe provisionofcwfinemergenciescanleadtouptakepost@emergency.inthesecases CWFshouldonlybeimplementedifthenecessarymaterialstomanufacture replacementpartsarelocallyorreadilyavailable.abenefitofproductsthatarelocally availablepriortoemergenciesisthat,ifadequatestocksaremaintained,thefilterscan bedeployedquicklyandefficiently.pottersforpeacehasestablished17cwf manufacturingfacilitiesworldwideandhasidentifiedfourkeyelementstofacility successincluding:thepartnerngo sexperiencewithmarketingandhealthtosupport thefilterproductionwithfilterdistribution,traininganddemandcreation;the availabilityoftechnicalsupportandamountofincountryvisitsbypottersforpeace;the understandingoflocalsituationsthatimpactthefilterfacilityincludingcountrystability; 38
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Wang,D.,Xu,X.,Deng,X.,andChen,C.(2010).Detection*of*Vibrio*cholerae*O1*and*O139*in* Environmental*Water*Samples*by*Immunofluorescent?Aggregation*Assay.Appliedand EnvironmentalMicrobiology.76:5520@5525. Watson,J.,Gayer,M.,andConnolly,M.(2007).Epidemics*after*Natural*Disasters.Emerging InfectiousDiseases.13(1):1@5. Wilder@Smith,A.(2005).Tsunami*in*South*Asia:*What*is*the*Risk*of*Post?disaster*Infectious* Disease*Outbreaks?.Annals,AcademyofMedicineSingapore.34(10):625@631. WorldHealthOrganization(WHO).(1994).GuidelinesforCholeraControl.Geneva:WorldHealth Organization. WorldHealthOrganization(WHO).(2005).Household*water*treatment*and*safe*storage* following*emergencies*and*disasters.geneva:worldhealthorganization. WorldHealthOrganization(WHO).(2006).WHO*Guidelines*for*Drinking*Water*Quality,*3 rd * edition.geneva:worldhealthorganization.availableonlineathttp://www.who.int. WorldHealthOrganization(WHO).(2007).Combatingwaterbornediseaseatthehousehold level.geneva:worldhealthorganization. Wright,J.,Gundry,S.,andConroy,R.(2004).Household*drinking*water*in*developing*countries:* A*systematic*review*of*microbiological*contamination*between*source*and*point?of?use. TropicalMedicineandInternationalHealth.9(1):106@117. Zaritsky,A.,andWoldringh,C.(1978).Chromosome*replication*rate*and*cell*shape*in*Escherichia* coli:*lack*of*coupling.journalofbacteriology.135(2):581@587. 46
ChapterThree: StudyDesignandMethods 47
3. StudyDesignandMethods 3.1. CeramicWaterFilterDiscDesign TherecipeusedforcreatingtheCWFdiscswasmodeledafterthatusedbyResource DevelopmentInternational Cambodia(RDIC).(Haganetal.,2008)Atotalofsevendesign scenarioswerecreatedbyvaryingboththeamountofcarbonfibreaddedtotherecipeaswell asthelengthoftheindividualfibres.thesevendesignscenariosaredetailedintable3@1below. RicehullswereobtainedfromTheCanadianWildRiceMercantileofThunderBay,Ontarioand carbonfibrewasobtainedfrombarrday,inc.ofcambridge,ontario.aspecificationsheetfor thecarbonfibreisincludedinappendixa.theclayusedwasepkkaolincontainingahigh amountofkaolinite(approximately97%,chemicalcomposition:al 2 Si 2 O 5 (OH) 4 )obtainedfrom Tucker spotterysupplies,inc.ofrichmondhill,ontario. Table3W1 CWFDiscDesignScenarios Material Disc1 Disc2 Disc3 Disc4 Disc5 Disc6 Disc7 EPKClay 1200g 1191g 1191g 1188g 1188g 1194g 1194g MilledRice Husks 355.5g 355.5g 355.5g 355.5g 355.5g 355.5g 355.5g Water (48approx.) 750mL 750mL 750mL 750mL 750mL 750mL 750mL Carbon Fibre None 9g 9g 12g 12g 6g 6g Carbon FibreLength None 6cm 3cm 6cm 3cm 6cm 3cm Thecarbonfibrewasvariedbyweight(0%,0.5%,0.76%and1%ofclayweight)andbylength(3 cmand6cmindividualfibrelengths).thericehullsweremilledusinganikamf10grinderwith a1mmscreen(figure3@1).priortomixingthericehullsweresievedusingano.16(1.19mm mesh)sieve. 48
Figure3W1:RiceHullsbeforemilling(left)andafter(right) Clay,ricehullsandcarbonfibrewerecombinedinacontainerandmixedthoroughlyforfive minutes(figure3@2).duetothemethodologyusedatrdic,thecarbonfibrewasmixedin looselywiththeclayandriceratherthanplacedinagridinordertoreplicatehowitwouldmost likelybeaddedinthefield.theuseofapot@shapedmoldandahydraulicpresstoformthefilter elementslimitstheabilitytoplacethecarbonfibreuni@directionallyorinagridwithinthefilter element.thewaterwasthenquicklyandevenlyaddedandthemixturewaskneadedforatleast 20minutes.Thesidesofthecontainerwereoccasionallyscrapedtoensurealltheingredients weremixedinthoroughly.oncemixed,approximately660gwereweighedandroughlyhand pressedintoadiscshape. 49
Figure3W2:Themixeddryingredientsbeforewaterisadded Thediscmoldwasplacedontoaflatsurfaceandlinedwithathinplasticbagtopreventtheclay mixturefromsticking.theclayballwasaddedtothemoldandthenthetopofthemoldwas pressedfirmlydownformingthediscshape.onceformed,thediscswereremovedfromthe moldandallowedtoairdryforthreetofourhours.afterthistime,thesurfacesofthediscs werescrapedusingaplasticputtyknifetoremoveirregularitiesandsmooththesurfaces. 50
Figure3W3:DiscsairWdryingpriortofiring Thediscswerethenair@driedforsevendays(Figure3@3)priortofiringinamufflefurnace (Figure3@4).AsshowninFigure3@3,thecharacterofthecarbonfibrewithinthediscsisthatthe fibresarenotunidirectionalandstraightbutrathercrimpedandbentwithintheclaymatrix. Theyexhibitarandom,three@dimensionalarray.Thetemperaturewassetto100 Cfortwo hoursandthenincreasedforeighttotenhoursto866 C.Thetemperaturewasheldatthis temperatureforninehoursandthenallowedtocoolfor24hours.oncefired,a0.55%solution ofsilvernitratewasappliedtoallsurfacesofeachdiscwithapaintbrush(figure3@5).someof thediscscameoutofthefurnacewithblackcarbonstainsasaresultofthericehullsburning andturningintocharcoal.thisisshowninfigure3@5.threediscsofeachdesignscenariowere manufactured.theaveragediscdiameteris155mm±1.6mmandthickness17.86mm±0.62 mm.theaveragediscweightafterfiringis300g±11.3g.accordingtoastmstandard TerminologyforCompositeMaterials(D3878@07),theCWFdiscscanbedefinedas discontinuousfibre@reinforcedcomposites. 51
Figure3W4:Mufflefurnaceusedforfiringdiscs Figure3W5:Discsafterfiring 3.2. FlowRateTesting Inordertotestthediscs,anapparatuswasdesignedtoallowflowofwaterthroughthem.Each discwasfastenedintoamachinedpvcringwithsiliconetopreventwaterfromshort@circuiting throughthering.oncethediscswerefastenedintotheirringstheyhadaneffectivesurface 52
areaof120mm±3.2mm.threeapparatusesweremanufacturedfrompvcpipetoallowfor thetestingofthreediscsatonce(figure3@6).theapparatustopsandbottomswerenumbered toensurethesameset@upwasusedconsistentlythroughout. Figure3W6:ApparatusfortestingCWFdiscs Theflowtestwasconductedbyfirstinstallingthediscsintotheapparatuses.3Loftapwaterat approximatelyroomtemperaturewasaddedintothetopofeachapparatusandwaterwas allowedtoflowthroughfor30mintoensureeachdiscwasfullysaturated.theeffluentfrom eachapparatuswascollectedinlargeerlenmeyerflasks.attheendofthe30minthewaterwas toppedupto3landtheflowteststarted.after3hrtheeffluentvolumewasrecorded. 53
Figure3W7:FlowtestapparatussetWup 3.3. BacteriaAttenuationTesting Tobegin,threediscswererandomlyselectedtobetestedsothatdiscsofthesamedesign scenariowerenottestedatthesametime.priortotesting,eachoftheapparatusesandthe discstobetestedwerecleanedwitha1:10dilutionofhouseholdbleach(6%sodium hypochlorite)andthoroughlyrinsedwithdechlorinatedtapwater.therinsingbothremovedthe chlorineasevidencedbyameasuredchlorineconcentrationof0mg/lintheeffluentandserved topre@saturatethefilters.thechlorineconcentrationwastestedusingachlorinetestkit.ifthe effluentoftherinsewatermeasuredchlorineresidual,sodiumthiosulphatewasaddedtothe rinsewaterandallowedtoflowthroughfortenminutesatwhichpointtheeffluentwas 54
retestedforchlorine.ifthechlorineconcentrationmeasured0mg/l,aneffluentsamplefrom thepre@saturationwaterwasplatedtoconfirmthatthefilterswerefreefrombacterial contaminationpriortoinitiatingtheexperiments. Thenon@pathogenictestmicrobeEscherichia*coli*(Ecoli)ATCC700891wasusedasasurrogate forbacterialpathogenspotentiallypresentindrinkingwatersources.ecoliisagramnegative, rodshapedbacteriumoriginatinginthegutofwarm@bloodedanimals.itssizeandmorphology istypicalofpathogenicbacteriapresentindrinkingwatersuchaspathogenicstrainsofecoli, Salmonella,Shigella,CampylobacterandVibrio.Thisparticularstrainwasusedduetoitsrelative easeofproductioninthelaboratory. Ecoliwasculturedinautoclavedtrypticsoybroth(TSB)byadding0.1mLofEcolistockto10mL ofpreparedtsbinasteriletesttube.thetsbmediumwas15gtrypticsoybrothper500ml milli@qwater,sterilized,andallowedtocoolovernight.thetesttubewasincubatedat37º Celsiusfor22@24hours.Thecontentsofthetesttubewereaddedtoapproximately8Lof dechlorinatedtapwatertoserveastheinfluentspikewater.toensureacompletetransferof theculturetothespikewater,thetesttubewasrinsedthreetimesintothespikewaterwith autoclavedmilli@qwater.aninfluentsamplewastakenforeachtestandtheresultinginfluent concentrationsrangedfrom10 7 10 8 CFU/100mL(averageof1.14x10 8 CFU/100mL).This bacterialconcentrationishigherthantypicallevelsmeasuredinsurfacewaterusedfordrinking water,toensurethattherewouldbemeasureableconcentrationsintheeffluenttoenable percentremovalcalculations.approximately2.5loftheinfluentspikewaterwasaddedtoeach apparatusandthespikewaterwasallowedtoflowthroughthediscsfor30minutespriorto 55
startingthetesttoensureeachdiscwasfullysaturated.afterthe30minutes,200mlof effluentwascollectedinanautoclavedflaskfromeachdisc.if200mlwasstillnotcollected after60minutes,theexistingamountineachflaskwasused.asecondinfluentsamplewas takenoncethethreeeffluentsampleswerecollected. ThemembranefiltrationmethodwasusedtoenumeratetheEcoliinundilutedanddiluted influentandeffluentsamples.underalaminarflowhood,serialdilutionswereperformedon thecollectedsamplestoensurethattheplateswouldbewithinthecountablerange(30 300 colonyformingunits,cfu).thesedilutionsrangedfrom10 @4 to10 @6 fortheinfluentsamplesand 10 0 to10 @4 fortheeffluentsamples.inordertoperformthedilutions,9mlofautoclavedmilli@q waterwasaddedtosteriletesttubes.thecollectedsamplesweremixedthoroughlyandthen 10mLwasaddedtothefirsttesttubeinthedilutionseries.Twoinfluentsamplesandtwo effluentsamplesfromeachdiscweredilutedandplatedforenumeration.1mlofthe10 0 test tubewasthenaddedtothe10 @1 testtubeusingafresh,disposablepipettetocreatetheinitial dilution.aftermixingusingavortexmachine,1mlofthe10 @1 testtubewasthenaddedtothe 10 @2 testtubeandsoon,untilallthetesttubesweredilutedwith10%oftheprevioussolution. 47mmpetridisheswithsterileabsorbentpadswerelabelledforeachofthedilutionstobe plated.2mloftsbwereaddedtoeachofthedishesusingafresh,disposablepipettetoensure nocontamination.thelidsofthepetridisheswerereplacedimmediatelyafterthebrothwas added. 56
Figure3W8:Serialdilutionsandpetridishesforplatingsamples Apieceofmanufacturer@certified,pre@sterilized0.45µmfiltrationpaperwasutilizedforthe filteringofe.coli.usingsterilizedtweezers,thefilterpaperwasplacedonanautoclavedfilter topthatwassealedontopofa1lfilteringflask,andattachedtoanelectricvacuumpump. Autoclavedmilli@Qwaterwasusedtowetthefilterpaperbeforethedilutedsamplewasadded. Next,thevacuumwasturnedonfor30seconds,andthenturnedoff.Thesamplewasspread evenlyacrossthesurfaceofthefilterpaper,withthevacuumbeingturnedonfor30seconds, andthenturnedoff.thetesttubewasrinsedthreetimeswithautoclavedmilli@qwaterto ensurethepropertransferofthesampletothefilterpaper.thevacuumwasthenturnedonfor afinaltimefor30seconds,andshutoff.thefilteredsamplewasasepticallytransferredtothe Petridishusingsteriletweezers,thecoverreplaced,andthebottomofthePetridishtapped severaltimesuntilairbubbleswerefullyremoved.thefilteringandplacementwerethen repeatedforalldilutions,inverted,andplacedintheincubatoratatemperatureof37 C+/@.2 C. 57
Figure3W9:MembranefiltrationlabequipmentsetWup After24hours(+/@2hours)ofincubation,thecolonieswerecountedifbetween30and300 coloniesperplate(standardmethods9222).thenumberofcolonieswasthenrecorded,while TNTCrepresentedplatesthathadcolonies TooNumerousToCount,whileNDCrepresented NoDiscernibleColonies (Figure3@10).Allglasswareandequipmentwasthenautoclavedand propercleanupmethodsfollowed.intotal,twoinfluentsamples,twoeffluentsamplesfrom eachdisc,onecontrolsamplefromeachdisctocheckforbacterialcontaminationpriorto addingthespikewater,onecontrolsamplefromthetsbandonecontrolsamplefromthe autoclavedmilli@qwaterusedforthedilutionswereplatedforeachsetoftestscompleted.two replicatesoftheecoliattenuationtestingwerecompletedforeachofthe21cwfdiscs. 58
Figure3W10:ExampleofEcolicoloniesafterincubation(NDCright,countablecoloniescentre, andtntcleft) 3.4. EquiWbiaxialFlexuralStrengthTesting InordertocomparethestrengthoftheCWFdiscdesignscenariostodeterminetheeffectof addingcarbonfibre,astmc1499@09standardtestmethodformonotonicequi@biaxialflexural StrengthofAdvancedCeramicsatAmbientTemperaturewasfollowedascloselyaspossible. Flexuralstrengthisamechanicalparameterforabrittlematerialdefinedasthematerial sability toresistdeformationunderload.thetestmethodusesaconcentricringtestconfiguration undermonotonicuniaxialloading.equi@biaxialflexuralstrengthisdefinedasthemaximum stressamaterialiscapableofsustainingwhensubjectedtoflexurebetweentwoconcentric rings.thediscisplacedontoalargersupportringandcompressedbyasmallerloadringas generallyshowninfigure3@11. 59
Figure3W11:Sectionviewofbasicequipmentsetupforequibiaxialtesting(ASTM2009) TwotypesoftestspecimensareconsideredinASTMC1499, machined and as@fired,which havealimiteddegreeofwarpage.theflatnesstoleranceforas@firedtestspecimensis0.1mmin 25mm.Thediscsfabricatedasdescribedabovehaveanaveragethicknessof17.86mm± 0.62mmanddonotmeetthisrequirementthereforetheresultsgeneratedmustbeusedfor comparisonpurposesonly. TheloadingfixtureusedinthetestwasmachinedoutofsteelasshowninFigure3@12and installedconcentricallyonaninstron5969universaltestingmachine.thesupportringhasa diameterof120mmandthicknessof5mmandtheloadringhasadiameterof60mmand thicknessof5mm.accordingtoastmc1499theratiooftheloadringdiameter,d L tothatof thesupportring,d S is0.2 D L /D S 0.5.TheratioofD L /D S forthetestingfixtureusedis0.5.the 60
supportringdiametershouldbewithin2 (D@D S )/h 12where D isthediscdiameterand h isthediscthickness.theratioof(d@d S )/hforthistestis2.inordertominimizetheeffectsof testspecimen@ringmisalignmentasheetofsiliconewasplacedbetweenthediscandthe supportring. Figure3W12:Loadingfixturefortheequibiaxialflexuralstrengthtesting Fiveofthefabricateddiscswerebrokenpriortobeginningthestructuraltestingthereforeonly 16discsweretested.SomeofthediscswerebrokenwhileremovingthemfromthePVCrings theyweresealedintoandsomeofthemwerebrokenwhiledeterminingwhichstructuraltestto useandunderwhatconditions.priortotestingtheremainingdiscs,thediameterandthickness ofeachweremeasuredatsixequallyspacedlocationsaroundthedisc.theloadandsupport ringswerethencleanedandinspectedforanynicksorimperfections.thesiliconeringwasthen placedontothesupportringandthediscwasplacedontoptakingcaretocenteritonthering. 61
Thediscwaspreloadedbyloweringthecrossheaduntiltheloadringwasjusttouchingthe surfaceofthediscandthevalueofthepreloadrecorded.thedisplacementoftheloadringwas settozeroandthetestinitiated.thedisplacementrateofthecrossheadwassetto10mm/s. Thetestwassettoendoncethedisplacementofthecrossheadreached20mmtoensurethe discwouldfailbeforetheendofthetest.thedatacollectedfromeachtestincludestime(s), extension(mm)andload(kn)atarateof13.33hz. Figure3W13:Equibiaxialflexuraltestsetup 3.5. Limitations Theprimarylimitationsofthestudywerethesmallnumberoffilterstestedforeachdesign scenario(threereplicateswerefabricatedforeachdesignscenario),theas@builtconditionofthe 62
filtersandtheshortdurationoftestingperfilter(tworeplicatesofthebacteriaattenuation testingwerecompleted). Duetotimeandrawmateriallimitationsonlythreediscsofeachdesignscenariocouldbe fabricatedlimitingthenumberofreplicatesthatcouldbecompletedforalltests.additionally, accordingtoastmc1499,aminimumoftentestspecimensisrequiredforthepurposeof estimatingameanbiaxialflexuralstrength. Themethodofdiscfabricationresultedinsomewarpageandunevensurfaces,whichcanresult innon@uniformloadingandcontactstressesthatresultinincorrectestimatesoftheequibiaxial flexuralstrength.thediscsurfacesincontactwiththetestingringsshouldbeasflataspossible forsuccessfulequibiaxialtests. Thetestingofthediscswascompletedoverarelativelyshorttimeduration.Inordertobetter characterizetheimpactsofaddingcarbonfibretothestandardcwfrecipecontinuingtesting overalongertimeperiodwouldbepertinentascwfstendtoneedreplacingafteronetotwo years. 3.6. References ASTMC1499.(2009).Standard*Test*Method*for*Monotonic*Equibiaxial*Flexural*Strength*of* Advanced*Ceramics*at*Ambient*Temperature.ASTMInternational.WestConshohocken, Pennsylvania,UnitedStates. Hagan,J.,Harley,N.,Pointing,D.,Sampson,M.,andSoam,V.(2008).Resource*Development* International*?*Cambodia*Ceramic*Water*Filter*Handbook.PhnomPenh,Cambodia. 63
ChapterFour:Results 64
4. Results 4.1. StudyObjectives Asindicatedpreviously,CWFshavebeenshowntobeeffectiveatattenuatingpathogensfrom drinkingwaterandreducingtheincidenceofdiarrhealdisease;however,thecwfstypicallyonly lastapproximatelytwoyearsmainlyduetobreakage,eitheroftheceramicfilterelement,the spigot,orthecontainercoupledwithlimitedavailabilityofreplacementpartsincommunities. (Brown,2007)Giventhatthesefiltersaregainingmorewidespreaduseinanumberofcountries worldwide,extendingtheirlifespanofusewouldhavesignificantvalue.inanefforttoimprove thissituation,thisresearchspecificallyinvestigatesthepotentialforresiliencyofthecwf elementtobeimprovedthroughtheadditionofcarbonfibretotherecipe.thischapter summarizestheeffectsofaddingcarbonfibretolowcostcwfs,includingexaminingimpactson flowrate,ecoliattenuation,andbiaxialflexuralstrength.theobjectivesinclude: 1. Creatingmodel@scaleCWFdiscsexploringseveralrecipes; 2. Assessingimplicationstoflow@throughrates; 3. PerformingE.coliattenuationtestingontheCWFdiscstodeterminebacteriaremoval characteristics;and, 4. PerformingstructuraltestingontheCWFdiscstodeterminestrengthcharacteristics. SevendiscdesignscenariosareasoutlinedinTable4@1.Thecarbonfibrewasvariedbyweight (0%,0.5%,0.76%and1%ofclayweightwhichequatesto0g,2g,3gand4gofcarbonfibreper disc,respectively)andbylength(3cmand6cmindividualfibrelengths).theweightofcarbon fibrewasvariedtoexplorearangeofamountsinanattempttocapturetheminimumrequired 65
toachievethepotentialbenefitswhileensuringalowfabricationcost.thelengthsusedwere approximately20%and40%ofthediscdiameterinanattempttocharacterizetheimpactsof variedreinforcingfibrelengths. Table4W1:CWFDiscRecipes DiscType DesignScenario 1 nocarbonfibre 2 3gofcarbonfibreperdisc,6cmlengths 3 3gofcarbonfibreperdisc,3cmlengths 4 4gofcarbonfibreperdisc,6cmlengths 5 4gofcarbonfibreperdisc,3cmlengths 6 2gofcarbonfibreperdisc,6cmlengths 7 2gofcarbonfibreperdisc,3cmlengths 4.2. Results AlldatafromthecompletedtestswereenteredintoMicrosoftExcelforMac2011andanalyzed usingstandardexcelfunctions. Ecolipercentreductionwascalculatedasfollows: %Removed=[(Conc EF Conc IN )/Conc IN ]X100 Log 10 reductionvalue(lrv)wascalculatedasfollows: Where: %Removed=Ecolipercentreduction(%) Conc IN =influentconcentration(cfu/100ml) Conc EF =effluentconcentration(cfu/100ml) LRV=Log 10IN Log 10EF Where: LRV=Log 10 reductionvalue Log 10IN =Log 10 ofinfluentconcentration Log 10EF =Log 10 ofeffluentconcentration 66
EcoliattenuationdatawerealsoenteredintoJMP10andanalysiscompleted.Incomparing Ecoliattenuationacrossalldisctypes,ANOVAwasused.Statisticalsignificance(α=0.05)was assessedusingthestudent st@testforeachpairofdisctypes.summarytablesofthedataare presentedhere;individualresultsareincludedinappendixb. 4.2.1. FlowTestData Two3hrflowtestswereconductedasdescribedinSection3.2oneachofthediscs;however, themeasuredflowratethroughallofthediscsfabricatedforeachdisctype(i.e.all21discs) increasedgreatlyatthecompletionofthefirsttwotests(theflowmeasuredintest1wasmuch lowerthantheflowmeasuredintest2).twoadditionaltests(tests3and4)wereconducted and,asthemeasuredflowratesstabilized,onlytheseresultswereretainedforcalculationand analysis.theincreaseinflowratemaybeattributabletotheflushingofbothdustfromthe firingprocessandresidualsilvernitrate.asummaryoftheflowtestdataisincludedintable4@ 2. Test3 and Test4 refertothetwoteststhatwereconductedaftertheflowratethroughthe discsstabilized. STD referstostandarddeviationand RSD% referstorelativestandard deviation. 67
Table4W2:Summaryofflowtestdata Disc Apparatus Test3 Test4 Average Average TotalAverage (ml/3hr) (ml/hr) (ml/hr) STD RSD% 1A 2 225 225 225 75 1B 3 250 250 250 83 85 10.5 12.4 1C 1 275 300 288 96 2A 3 1300 1275 1288 429 2B 1 1225 1250 1238 413 432 21.0 4.86 2C 2 1400 1325 1363 454 3A 2 1650 1625 1638 546 3B 3 1625 1575 1600 533 531 16.8 3.2 3C 1 1525 1550 1538 513 4A 1 2000 2175 2088 696 4B 3 1575 1550 1563 521 586 95.6 16.3 4C 2 1575 1675 1625 542 5A 2 1600 1600 1600 533 5B 1 2125 2125 2125 708 600 94.6 15.8 5C 3 1650 1700 1675 558 6A 1 1500 1600 1550 517 6B 2 1825 1825 1825 608 526 77.5 14.7 6C 3 1350 1375 1363 454 7A 2 1150 1225 1188 396 7B 3 950 1025 988 329 360 33.7 9.4 7C 1 1075 1050 1063 354 4.2.1.1. Analysis Duetothedesignofthetestingapparatus(Figure3@6),theeffectivesurfaceareaoftheCWF discswasapproximately113cm 2 withamaximumvolumeof3labletobeaddedtothetopof eachapparatus.inordertocharacterizetheimpacttheadditionofcarbonfibrehadontheflow ratescomparisonsweremadebetweentherecipewithoutcarbonfibre(disctype1)andthose withcarbonfibre(disctypes2through7). Whengenerallycomparingtheflowtestresultsofdiscswithandwithoutcarbonfibre,the resultsshowthatthecarbonfibreadditiontothediscsincreasedtheflowratebyanaverageof 595%.Theaverageflowrateofdiscswithoutcarbonfibre(DiscType1)is85mL/hrandthe 68
averageflowrateofdiscswithcarbonfibre(disctypes2through7)is506ml/hr.lookingat eachdisctypeindividually,theadditionofcarbonfibreincreasedtheflowratebyarangeof 424%(comparingDiscType1withDiscType7:2gofcarbonfibreat3cmlengths)to706% (comparingdisctype1withdisctype5:4gofcarbonfibreat3cmlengths)dependingonthe amountaddedandthelengthofindividualfibres. Theamountofcarbonfibreaddedtoeachdesignscenariowasvariedbyweight(0.5%,0.76% and1%ofclayweight)andbylength(3cmand6cmindividualfibrelengths).inordertobetter understandtheimpactofeachofthesevariations,comparisonsofmeasuredflowratesare madebetweendiscswithoutcarbonfibre(disctype1)andthosewithvaryingamountsof carbonfibre(2g DiscTypes6and7,3g DiscTypes2and3,and4g DiscTypes5and6of carbonfibreperdisc)andthosewithvaryinglengthsofindividualfibres(3cm DiscTypes3,5, and7,and6cm DiscTypes2,4,and6).Theaveragemeasuredflowratebyweightofcarbon fibreaddedperdiscisasfollows:2g=443ml/hr,3g=482ml/hr,and4g=593ml/hrimplying thattheflowrateincreaseswithanincreaseincarbonfibreperdisc.figure4@1showsa graphicalrepresentationofthedata.thesquaredatapointssignifythemeasuredflowratesfor eachdisctypeandthediamonddatapointsaretheaverages.fromthegraphitcanbeseenthat thereisastronglinearrelationship(r 2 =0.93)betweentheamountofcarbonfibreaddedand theflowrate.also,thevariationintheflowrateappearstodecreasewithanincreasingquantity ofcarbonfibre. 69
FlowRateVs.CarbonFibreWeightperDisc 625 FlowRate(mL/hr) 575 525 475 425 375 y=75.00x+280.79 R²=0.93 325 2 3 4 WeightofCarbonFibreperDisc(g) Figure4W1:FlowRateVariationbyWeightofCarbonFibreperDisc Whencomparingtheflowratebetweendiscswithvaryinglengthsofindividualcarbonfibres,it isobservedthattheaverageflowrateisasfollows:3cm=497ml/hrand6cm=515ml/hr. Thisimpliesthatapositiverelationshipexistsbetweentheflowrateandthelengthoffibres;as theflowrateincreaseswithincreasesinfibrelength.however,asshowninfigure4@2,this relationshiponlyholdstrueforthosediscswith2gofcarbonfibreperdiscand,infact,theflow ratedecreaseswithincreasingfibrelengthforthosediscswith3gand4gofcarbonfibrein them.therefore,itcannotbestatedconclusivelythatincreasingthelengthoffibreswill increasetheflowrate.additionally,itdoesappearthatvariationsinflowratedecreasewiththe longerlengthofindividualfibres. 70
FlowRateVs.LengthofIndividualCarbonFibres 650 FlowRate(mL/hr) 600 550 500 450 400 350 Average 2g 3g 4g Linear(Average) Linear(2g) Linear(3g) Linear(4g) 300 3 6 LengthofIndividualCarbonFibres(cm) Figure4W2:FlowRateVariationbyIndividualCarbonFibreLengths 4.2.2. BacteriaAttenuationData AsummaryofresultsforlaboratorytestingoftheCWFdiscsforEcolireductionsfromspiked watersareprovidedintable4@3.thediscswithoutcarbonfibre(disctype1)reducedecoliby ameanlrvof4.0whilethediscswithcarbonfibre(disctypes2through7)reducedecolibya meanlrvrangingfrom2.2 3.0,withtheinfluentE.coliconcentrationsasreportedin Section3.3.AnANOVAcomparisonofdifferencesbetweendisctypesshowedsignificant differencesforthereductionofecoli(p=0.0005);however,twomeansamplecomparison(t) testsbetweendisctypes(table4@4)indicatedthatonlyeightofthe21discpairingsshowed significantdifferencesinecolireduction(1@6,2@6,3@6,5@6,7@6,1@4,7@4,and1@3)witha95% significance.agraphicalrepresentationoftheecoliattenuationresultsisincludedinfigure4@3. 71
Table4W3:SummaryofEcoliattenuationdata DiscScenario 1 2 3 4 5 6 7 %Removal 99.99 99.83 99.67 99.56 99.82 99.33 99.88 StdDev 0.0109 0.0859 0.4241 0.2811 0.0878 0.9062 0.0833 StdErrMean 0.0029 0.0230 0.1133 0.0812 0.0235 0.2616 0.0223 LRV 4.0 2.8 2.6 2.4 2.7 2.2 3.0 n 14 14 14 12 14 12 14 Table4W4:Summaryofmeansamplettestsbetweendisctypes DiscType Pair Difference pvalue 1@6 0.6655024 <0.0001* 7@6 0.5557667 0.0003* 2@6 0.5080167 0.0010* 5@6 0.4983452 0.0012* 1@4 0.4363107 0.0044* 3@6 0.3422452 0.0243* 7@4 0.3265750 0.0314* 1@3 0.3232571 0.0267* 2@4 0.2788250 0.0652 5@4 0.2691536 0.0749 4@6 0.2291917 0.1427 7@3 0.2135214 0.1402 1@5 0.1671571 0.2470 2@3 0.1657714 0.2509 1@2 0.1574857 0.2752 5@3 0.1561000 0.2795 3@4 0.1130536 0.4509 1@7 0.1097357 0.4463 7@5 0.0574214 0.6899 7@2 0.0477500 0.7400 2@5 0.0096714 0.9464 *Starredvaluesindicatethatasignificant differenceexistsforecolireductionbetween thedisctypesintheindicatedpair 72
Figure4W3:GraphicalrepresentationofEcoliattenuationresults 73
4.2.2.1. Analysis Theremovalratesachievedduringthelaboratorytestingforalldisctypesarewithintherange ofthosefoundintheliterature(asdescribedinsection2.2.1,theaveragebenchmarkstandard forecoliremovaleffectivenessis97±3%,simonisandbasson,2011),whichshowsthatthe fabricateddiscsarecomparabletolowcostcwfscurrentlybeingused. Whencomparingdiscswithoutcarbonfibre(DiscType1)tothosewithcarbonfibre(DiscTypes 2through7),Figure4@4showsthatDiscType1hashigherpercentremovalratesandless variationthantheotherdisctypes.theanovatestindicatedthatasignificantdifferenceexists betweentheremovalratesofthedisctypes,however,thettests(table4@4)revealedthatonly threedisctypes(disctypes3,4,and6)outofthesixwithcarbonfibreactuallyhavesignificant differencesbetweenmeanecoliremovalrates.figure4@4revealsthatthesedisctypesarethe oneswiththelowestecoliremovalratesaswellasthehighestvariation.thisisanoteworthy observationasthismeansthattheadditionofcarbonfibreincertainquantitiesandlengths doesnotsignificantlychangetheecoliremovalrateofthediscs.thettestsalsoindicatethat DiscType6hassignificantlydifferentmeanEcoliremovalratesthanmostoftheotherdisc types(disctypes1,2,3,5,and7).thiscouldbebecausetheresultsfromdisctype6(2gof carbonfibreof6cmindividualfibrelengths)werehighlyvariableanddisctype6hasthe higheststandarddeviation(0.9062)ofallsevendisctypes. 74
PercentRemovalofEcolibyDiscType 100.20 %EcoliRemoval 99.90 99.60 99.30 99.00 98.70 98.40 1 2 3 4 5 6 7 DiscType Figure4W4:PercentRemovalofEcolibyDiscType Inordertobettercharacterizetheimpactofaddingcarbonfibretothediscs,comparisonsof percentremovalratesaremadebetweendiscswithoutcarbonfibre(disctype1)andthose withvaryingquantitiesofcarbonfibreperdisc(2g DiscTypes6and7,3g DiscTypes2and 3,and4g DiscTypes5and6)andthosewithvaryinglengthsofindividualfibres(3cm Disc Types3,5,and7,and6cm DiscTypes2,4,and6).Theaveragepercentremovalrateby weightofcarbonfibreaddedperdiscisasfollows:2g=99.61%,3g=99.78%,and4g=99.68%. Thisindicatesthatthebacteriaattenuationratedoesnotvaryconsistentlywithincreasing amountsofcarbonfibreperdisc.figure4@5showsagraphicalrepresentationofthedata.the squaredatapointssignifythepercentecoliremovalratesforeachdisctypeandthediamond datapointsaretheaverages.thevariationinremovalratesdoesnotappeartoincreaseor decreaseconsistentlywithachangeinamountofcarbonfibreperdisc. 75
PercentEcoliRemovalVs.WeightofCarbonFibreper Disc %EcoliRemoval 100.00 99.90 99.80 99.70 99.60 99.50 99.40 99.30 99.20 y=0.0386x+99.574 R²=0.20376 2 3 4 WeightofCarbonFibreperDisc(g) Figure4W5:PercentEcoliRemovalbyWeightofCarbonFibreperDisc WhencomparingthepercentremovalratesofEcolibetweendiscswithvaryinglengthsof individualcarbonfibres,itisobservedthattheaverageremovalrateisasfollows:3cm=99.81% and6cm=99.57%.thisimpliesthatanegativerelationshipexistsbetweentheecoliremoval rateandthelengthoffibres;theecoliremovalratedecreaseswithanincreaseinfibrelength. However,asshowninFigure4@6,thisrelationshipdoesnotholdtrueforthosediscswith3gof carbonfibreperdiscastheremovalrateincreaseswithincreasingfibrelength.therefore,it cannotbestatedconclusivelythatincreasingthelengthofcarbonfibreswilldecreasetheecoli attenuationrate.additionally,itdoesappearthatthevariationinremovalrateincreaseswith thelongerlengthofindividualfibres.anadditionalfactorinbacteriaremovalisporetortuosity. Voidspacesthataremoretortuousarebetteratretainingbacteriathanvoidspacesthatare cylindricalinshape.theadditionofcarbonfibremaybecreatingvoidspacesthataremore cylindricalshaped. 76
99.94 PercentEcoliRemovalVs.LengthofIndividualCarbonFibres %EcoliRemoval 99.83 99.72 99.61 99.50 99.39 Average 2g 3g 4g Linear(Average) Linear(2g) Linear(3g) Linear(4g) 99.28 3 6 LengthofIndividualCarbonFibres(cm) Figure4W6:PercentEcoliRemovalbyLengthofIndividualCarbonFibres OthertrendsinthedatawerealsoexploredincludingcomparingdiscweighttoEcoliLRV (Figure4@7)andcomparingflowratetoLRV(Figure4@8).Inbothfigures,thediamonddata pointsindicatediscswithoutcarbonfibrereinforcement,andthesquaredatapointsindicate discswithcarbonfibrereinforcement.incomparingdiscweighttolrv,apositiverelationship (R 2 =0.72)wasfoundforthediscswithoutcarbonfibrereinforcementwhilenocorrelation(R 2 = 0.003)wasfoundforthediscswithcarbonfibrereinforcement.Thisindicatesthatdiscweight, andthereforediscthickness,isanimportantfactorinthebacterialrvfortraditionalcwfs withoutreinforcement.theadditionofcarbonfibremakesthecwfdiscslesssensitivetodisc weightmeaningthatusinglessrawmaterialispossiblewhileachievingsimilarbacterialrvs.in comparingflowratewithbacterialrv,nostrongcorrelationwasobservedeitherforthediscs withoutcarbonfibrereinforcement(r 2 =0.02)orwithcarbonfibrereinforcement(R 2 =0.25). 77
Theweaknegativerelationshipobservedforthediscswithcarbonfibrereinforcementimplies thatthehigherflowratesarepotentiallycausedbysomelargervoidspacesthatwouldallow bacteriatoflowthroughthediscsmorereadily. 5 DiscWeightvs.LogReduceonValue LogReduceonValue 4.5 4 3.5 3 2.5 2 y=0.003x+1.831 R²=0.003 y=0.07x@18.60 R²=0.72 1.5 285 290 295 300 305 310 315 320 325 330 DiscWeight(g) Figure4W7:Discweightvs.logreductionvalue 78
FlowRatevs.LogReduceonValue LogReduceonValue 5 4.5 4 3.5 3 2.5 2 y=0.01x+3.64 R²=0.02 y=@0.00x+3.61 R²=0.25 1.5 50 150 250 350 450 550 650 750 FlowRate(mL/hr) Figure4W8:Flowratevs.logreductionvalue 4.2.3. EquiWbiaxialFlexuralTestData Atypicalload@extensioncurvefromthedatatakenduringtheequi@biaxialflexuraltestingis includedinfigure4@9.thebreakingloadwascharacterizedastheinitialpeakonthecurveand thisvaluewasusedtocalculatetheequi@biaxialflexuralstrengthforeachdisc.moredatathan wasneededwasrecordedastheend@of@testwassettobewhenthecrossheadextension reached20mm.thepeaksofthecurvecreatedaftertheinitialwereduetothebrokendisc piecesshiftingandresistingtheloadringasitcontinuedtoextendtowardthesupportring.the discstypicallyfailedwithcrackpatternsanexampleofwhichisshowninfigure4@10. 79
LoadWExtensionCurveforDisc2C 0.25 Load(kN) 0.2 0.15 0.1 0.05 0 0 2 4 6 8 10 12 14 16 18 20 Extension(mm) Figure4W9:TypicalloadWextensioncurve Figure4W10:Typicalfaileddiscpoststructuraltest 80
Oncethebreakingloadforeachdiscwasdeterminedfromthedatacollecteditwasusedto calculatetheequi@biaxialflexuralstrengthusingthefollowingequationfromastmc1499.the valueofpoisson sratiousedwas0.24.thisvaluewasobtainedbyaveragingvaluesusedfor similarclaymaterialsfoundatwww.memsnet.org.thecalculatedvaluesforequi@biaxialflexural strengthareincludedintable4@5below. where: σ f =equi@biaxialflexuralstrength(mpa) F=breakingload(N) h=discthickness(mm) ν=poisson sratio D S =diameterofsupportring(mm) D L =diameterofloadring(mm) Table4W5:Summaryofequibiaxialflexuraltestresults DiscType 1 2 3 4 5 6 7 Equi@biaxialStrength (Mpa) 0.293 0.203 0.320 0.188 0.153 0.222 0.231 StandardDeviation 0.053 0.006 0.057 0.051 0.045 0.092 0.030 n 3 2 2 2 2 3 2 4.2.3.1. Analysis Whencomparingtheequi@biaxialflexuralstrengthofthediscswithoutcarbonfibre (DiscType1=0.293MPa)totheaverageofthosewith(DiscTypes2through7=0.220MPa)the datasuggeststhataddingcarbonfibremakesthediscslessstrong.inordertobetter characterizetheimpactofaddingcarbonfibretothediscs,comparisonsofequi@biaxialflexural strengtharemadebetweendiscswithoutcarbonfibre(disctype1)andthosewithvarying amountsofcarbonfibre(2g DiscTypes6and7,3g DiscTypes2and3,and4g DiscTypes 5and6ofcarbonfibreperdisc)andthosewithvaryinglengthsofindividualfibres(3cm Disc 81
Types3,5,and7,and6cm DiscTypes2,4,and6).Theaverageflexuralstrengthbyweightof carbonfibreaddedperdiscisasfollows:2g=0.227mpa,3g=0.262mpa,and4g=0.170.this indicatesthattheequi@biaxialflexuralstrengthdoesnotvaryconsistentlywithincreasing amountsofcarbonfibreperdisc.figure4@11showsagraphicalrepresentationofthedata.the squaredatapointssignifytheflexuralstrengthforeachdisctypeandthediamonddatapoints aretheaverages.thevariationsinstrengthwithineachamountofcarbonfibreaddeddonot appeartoincreaseordecreaseconsistentlywithachangeinamountofcarbonfibreperdisc. EquiWbiaxialFlexuralStrength(MPa) 0.335 0.300 0.265 0.230 0.195 0.160 FlexuralStrengthVs.WeightofCarbonFibreperDisc Figure4W11:EquiWbiaxialFlexuralStrengthbyWeightofCarbonFibreperDisc Whencomparingtheequi@biaxialflexuralstrengthbetweendiscswithvaryinglengthsof individualcarbonfibres,itisobservedthattheaveragestrengthisasfollows:3cm=0.235mpa and6cm=0.205mpa.thisimpliesthatanegativerelationshipexistsbetweentheflexural strengthandthelengthoffibres;asinthestrengthdecreaseswithanincreaseinfibrelength. However,asshowninFigure4@12,thisrelationshipdoesnotholdtrueforthosediscswith4gof 82 y=@0.03x+0.30 R²=0.37 0.125 2 3 4 WeightofCarbonFibreperDisc(g)
carbonfibreperdiscastheflexuralstrengthincreaseswithincreasingfibrelength.therefore,it cannotbestatedconclusivelythatincreasingthelengthofcarbonfibreswilldecreasetheequi@ biaxialflexuralstrength.additionally,itdoesappearthatthevariationinflexuralstrength decreaseswiththelongerlengthofindividualfibres. FlexuralStrengthVs.LengthofIndividualCarbonFibres EquiWbiaxialFlexuralStrength(MPa) 0.34000 Average 0.29000 2g 3g 0.24000 4g Linear(Average) 0.19000 Linear(2g) Linear(3g) 0.14000 Linear(4g) 3 6 LengthofIndividualCarbonFibres(cm) Figure4W12:EquiWbiaxialFlexuralStrengthbyLengthofIndividualCarbonFibres 4.2.3.2. Commentary Theprecedingresultsareunexpected.Theoretically,theadditionofareinforcingfibretothe CWFdiscmatrixshouldhaveincreasedtheequi@biaxialflexuralstrengthofthediscsduetoload transferringfromtheclaymatrixtothereinforcingcarbonfibres.eventhoughrandomlyarrayed fibrereinforcementsaretypicallyleasteffectiveatstrengtheningmaterials,somestrength enhancementwasexpected.arandomarraywasselectedasitishowitwouldbeimplemented atthecwffactoryincambodiathatthesediscsweremodeledafter.randomlyarrayed 83
reinforcementsmakeanisotropiccompositethatischeapertofabricatethancompositeswith continuousfibrereinforcement. Oneexplanationforthereductioninstrengthisresidualstress@straindistributionsafter fabricationcausedbydifferentialthermalexpansion,whichwaspotentiallyobservedinthe smallcracksthatwereconsistentlypresentonallsurfacesofthediscsafterfiring(figure4@13). Thethermalexpansioncoefficientforcarbonfibreis2.15x10 @6 K @1 (PerformanceComposites Ltd.,nodate)whilethatofkaoliniteis18.6x10 @6 K @1 (McKinstry,1965).Inthiscasethethermal expansionvalueofthematrixishigherthanthatofthecarbonfibrecausingstrainmismatches. Thisisnotidealasthecarbonfiberisbetterabletowithstandtensilestrains.Thediffering thermalexpansionpotentiallyimpactedtheinterfacialpropertiesbetweenthekaolinitematrix andthecarbonfibreleadingtoafibre/matrixbondthatwastooweak.thisreferstoan adhesivefailurebetweenthecarbonfibreandclayleadingtodisbanding(figure4@13).anideal fibre/matrixbondisabalancebetweenweakandstrongasastrongfibre/matrixinterface lowersthefibrecriticallengthbutaweakerfibre/matrixinterfaceallowsstrengthening mechanismstooccursuchasfibrebridging,fibrepull@out,matrixmicrocracking,etc.that minimizecatastrophicfailures.inthiscaseitappearsasiftheinterfacialbondbetweenthe carbonfibrereinforcementandthekaoliniteclaymatrixwastooweaktherebyreducingthe equi@biaxialflexuralstrengthofthecwfdiscs. 84
Figure4W13:Brokendiscshowingsurfacecracksanddisbondedcarbonfibre Theapproximatecostofthecarbonfibreusedinthisstudy(6Ktow)isUS$0.036/50cm.The totallengthofcarbonfibreusedis500cm 1000cmperdisc,dependingontherecipe,ora costofus$0.36@us$0.72perdisc.aspreviouslymentioned,potstylecwfsrangeincostfrom US$5@US$30.Comparingtheweightofclaymixtureperdiscinthisstudy(660g)totheamount perpotusedbyrdic(8000g)allowsanestimateofscaletobemade.thediscsare approximately12timessmallerthanthepotsmadebyrdicmeaningthatthecostofcarbon fibreperpotwouldrangefrom$4.32@$8.64.thisisasignificantcostincreaseandcould potentiallylimittheaccesstothesefiltersbythepoor. 85
4.3. References Brown,J.(2007).Effectiveness*of*Ceramic*Filtration*for*Drinking*Water*Treatment*in*Cambodia. DoctorofPhilosophy.UniversityofNorthCarolina.ChapelHill. McKinstry,H.(1965).Thermal*Expansion*of*Clay*Minerals.TheAmericanMineralogist.50:212@ 222. PerformanceCompositesLtd.(Nodate).Mechanical*Properties*of*Carbon*Fibre*Composite* Materials,*Fibre/Epoxy*Resin.http://www.performance@ composites.com/carbonfibre/mechanicalproperties_2.asp.accessedonlinejuly31,2012. Simonis,J.,andBasson,A.(2011).Evaluation*of*a*low?cost*ceramic*micro?porous*filter*for* elimination*of*common*disease*microorganisms.physicsandchemistryoftheearth.36:1129@ 1134. 86
ChapterFive:ConclusionsandRecommendations 87
5. ConclusionsandRecommendations 5.1. Summary Whilepeopleworldwidehavemadesignificantgainsinrecentyearsinaccesstopotable drinkingwater,hugedisparitiesexistbetweenaccessbytherichandthepoor.withoutdirect accesstowaterinthehome,watermustbecollectedelsewhereandthentransportedto,and storedin,thehomepriortouse.microbialcontaminationofwaterduringthecollection, transportation,andstorageofwaterislikely.anumberofpoutechnologiesexisttotreatwater inthehomepriortouse.cwfsareahouseholdleveltechnologythathavebeenshowntobe effectiveatremovalofpathogensfromdrinkingwaterandreducingtheincidenceofdiarrheal disease;however,thecwfstypicallyonlylastapproximatelytwoyearsmainlyduetobreakage. Thisresearchstrivedtoexaminethepotentialforcarbonfibretoimprovethemechanical characteristicsofthecwfelementtoimproveitslengthofuseinthefieldwhilemaintaining,or improving,existingflowandbacteriaattenuationcapabilities.giventhatcwfsaregainingmore widespreaduseinmanycountriesworldwide,extendingtheirlifespanofusewouldhave significantvalue.thefourprimaryobjectivesofthisresearchareto: 1. Createmodel@scaleCWFdiscsexploringseveralrecipes; 2. Assessimplicationstoflow@throughrates; 3. PerformE.coliattenuationtestingontheCWFdiscstodeterminebacteriaremoval characteristics;and, 4. PerformstructuraltestingontheCWFdiscstodeterminestrengthcharacteristics. 88
Sevendisctypeswerecreatedbyvaryingthequantityofcarbonfibreperdisc(0.5%,0.76%,and 1%ofclayweightwhichequatesto2g,3g,and4gofcarbonfibreperdisc,respectively)andby length(3cmand6cmindividualfibrelengths).threereplicatesofeachofthesevendisctypes werefabricated,testswereconducted,thedatawascollectedandanalyzed,andtheresultsare presentedhere. 5.2. Conclusions Relationshipsofdisctypesandflowrate,bacteriaattenuation,andflexuralstrengthwere evaluatedinthisstudy.asummaryofthefindingsfromthisstudyinclude: Flow%Rate%Through%the%Discs% TheCWFdiscswithcarbonfibrereinforcementhadanaverageflowrateapproximately 6timeshigherthanthediscswithoutcarbonfibrereinforcement. Astrongpositive,linearrelationship(R 2 =0.93)existsbetweentheweightofcarbon fibreperdiscandflowrate. Arelationshipcouldnotconclusivelybemadebetweenthelengthofindividualfibres andflowrate. Adecreaseinflowratevariabilitywasobservedwithanincreaseinboththeweightof carbonfibreperdiscandlengthofindividualfibres. E%coli%Attenuation%Characteristics% Thediscswithoutcarbonfibrehadhigherpercentremovalratesandlessvariationthan theotherdisctypes;however,thettestsrevealedthatonlythreedisctypes(disctypes 89
3,4,and6)outofthesixwithcarbonfibreactuallyhavesignificantdifferencesbetween meanecoliremovalrates.thismeansthattheadditionofcarbonfibreincertain quantitiesandlengthsdoesnotsignificantlydetractfromtheecoliremovalrateofthe discs.therewerenostrongcorrelationsfoundbetweenecoliremovalandweightof carbonfibreperdiscorindividuallengthofcarbonfibres. AdecreaseinEcoliattenuationvariabilitywasobservedwithanincreaseinlengthof individualreinforcingfibres. Apositiverelationship(R 2 =0.72)wasobservedbetweendiscweightandEcoliremoval forthediscswithoutcarbonfibrereinforcement,butnotforthereinforceddiscs meaningthatthesediscsarelesssensitivetodiscweightandusinglessrawmaterialis possiblewhileachievingsimilarbacterialrvs. NostrongcorrelationswereobservedbetweenflowrateandEcoliremovalforanyof thedisctypes. Equi8biaxial%Flexural%Strength%Characteristics% Theflexuralstrengthdataindicatethattheaddition(aspertheprocedureofaddition usedherein)ofcarbonfibreinanyweightorfibrelengthconfigurationmakesthediscs lessstrong. Itwasobservedthatthevariationinflexuralstrengthdecreaseswiththelongerlength ofindividualfibres. Thereductioninstrengthispotentiallyexplainedbyresidualstress@straindistributions causedbydifferentialthermalexpansionduringfiring.kaolinitehasamuchhigher 90
thermalexpansioncoefficientthancarbonfibre,makingthefibre/matrixbondtooweak forthestressloadtotransferfromtheclaymatrixtothereinforcingcarbonfibres. 5.3. Recommendations IncreasingtheusablelifespanofCWFswouldbenefitmanypeoplebyincreasingthebreak@ resistanceandhenceprovidingaccesstowaterwithreducedconcentrationsofpathogensfora longerperiod.inlightofwhatwaslearnedinthisstudy,thattherearebenefitstoadding reinforcingfibrestocwfelementsincludingtheincreaseinflowratewithoutalways significantlyreducingbacteriaremovalcapabilities,furtherworkcanbecompletedtobuildon thisresearchandcomeupwithanappropriatereinforcingconfigurationtoimproveboththe mechanicalcharacteristicsofcwfswhilemaintainingbacteriaremovalcapabilitiesatalowcost. Futurestudiesshouldinvestigate: Removalmechanismanalysis Inordertodeterminewhichremovalmechanismsareplayingaroleinattenuating bacteriaandtobettercharacterizetheimpactofaddingcarbonfibrereinforcement, testsshouldbeconductedusingasetsofsamplesbothwithandwithoutsilvernitrate. Differentfibreconfigurations Perhapsincreasingtheamountofreinforcingfibresperdiscwouldstrengthenthe clay/fibrematrixandallowstrengtheningmechanismstooccur.determiningawayto placethereinforcingfibresinamoreuniformconfigurationcost@efficientlymayalso helpmakethebenefitsofaddingreinforcementmoreevident. 91
Differentfibretype DuetothefabricationoftheseCWFsrequiringfiringathightemperatures,usingan alternativefibrewithathermalexpansioncoefficientthatmorecloselymatchesthatof theclaywouldreducetheresidualstress@straindistributioncausedduringfabrication andimprovetheinterfacialpropertiesofthefilter.analternativefibremaybemore costeffectiveaswell. 92
AppendixA CarbonFibreSpecificationSheet 93
Cytec Carbon Fibers LLC 7139 Augusta Road Piedmont, SC 29673 Thornel Carbon Fiber Property Data Date: 20-Aug-2010 Customer: Customer Order No: Product: Cytec Order No: Total Quantity Shipped: BARRDAY CORPORATION 2-117437 T-300 6K 309 NT 603008910/10/0 417.00 lb Based on random lot samplings, listed are the average physical properties of the lots included in this shipment. Trace Number: RG6G0801 Quantity Shipped: 417 lb Mfg Date: 03-Aug-2010 Yield Fiber Density Tensile Strength Sacma Modulus Young's Modulus Elong** Sizing g/m g/cc ksi Msi Msi % Strain % AVG 0.3994 1.752 594 32.4 33.9 1.7419 1.0 The material shipped on this order is in compliance with Cytec Carbon Fibers' PAN property data requirements. **Elongation is a calculated value based on Tensile Strength / Modulus x 100. Report Number: SC_PROP-0002438 Page 1 of 1