Ventilated Improved Pit Latrines通风改良坑式厕所设计建造 21

1/1VentilatedImprovedPitLatrines通风改良坑式厕所设计建造219.Superstruqtu.F%jBAmyorkforthespiralferrocement+superstructureisavailablecommerciallyinZimbabwe;itismadefrom1.8-mwidecorrugatedgalvanizedironsheetingand40mmsteelanglebars.Initiallytheformwork-,wasdesignedinthreeparts,butnowfourpartsareuse@(AnnexI).Theformworkislo=catedintheappropriatepositiononthe-cover‘slabiandcoveredwith38mmmeshchickenwire,,whichissecuredtotheformworkatbottomwith8swg(3.12mm)wire..Cementmortar(4partsbuildersand-/,11toPand_.part.cement)isthenplasteredontheformworktojustcover1themesh;afterl-2hoursasecondlayerofmortarisplasteredon,zogiveatotalthicknessof40-50mm.Aftertwodaysinmoderatelywmweather,theformworkcanberemoved.Theferrocement,onceithasdried,iscuredforaboutaweekbyregularlysoakingitwithwer.Oncetheformworkhasbeenremoved,thecoverslabisplasteredwithcementmortarsothatastepisformedattheentrance(tokeepoutrainwater)andthe*slabinalldirectionstowardsthesquathole.If,irequired/fooaddedatthisstage;currentpracticeinZimbabye,however,isfootrestsastheyarenotdemandedbytheusers1‘I20.Roof.Theroofismadetothesameshhpeasthesup50mmlargerallround.The.cqnstruction‘procedureisin~geforthecoverslab,althoughtheslabisthinneri(25mm)andmortar(3:lmix)reinforcedwitha’singlelayeqofchickenmesh.roofslabiscured,itisbeddedinontopofthesmortar.I21.VentPipe.EarlytrialsinZimbabweshowedthat100mm’diameterasbestoscementventpipesdidnotperformwell;evenwhenprovidedwithatopsectionenlargedto150mm.Howevera150,mmdiameterpipeenlargedattitslopto200mmwasfoundsatisfactoryandthishasbeenadoptedasthestandarddesign.Theeniargedtopsectionwasincorporatedintothedesigntocompensateforthereductionineffectivecross-sectionalarea(andthusgreaterairflowhead*loss)duetotheflyscreen.Twostandardventpipesarecommerciallyavailable-inZimbabwe,onemadeofasbestoscemenfitheother_’ofultravolet‘stabilizedPVC.Originallypipesweremadeofgalvanizediron,butthesetendtocorrodeafteruseforanumber’ofyears.Theasbestos,._pipecomesintwosections:withastandardcollar,alowersection,1.9mx146mminternaldiameterand‘anupperexpansion-section,0.74mlongtaperingsfrom146mmto216mminternaldiameter(seeFigures2and‘3andAnnexI).--kc-M-Thetwosectionsarecementedtogetherusing‘.Isand,1partcement).stiffceinentmortar(2*Aglass‘fiberflyscr;eenis,glued-withepoxy,resintGAY1.__thetopofthepipe,andheldinplaceby‘anasbestoscement,ring.ThePVC--.‘pipe’is2.44mlongandthemainshafthasaninternaldiameterofl-55’mmandanexternaldiameterof162mm.Theexternaldiameteroftheconedsectionis-200mm.Thepipesaresoldalreadyblack-pigmented.‘Aswiththeasbestos:,.cementpipeaglassfiberscreenisgluedwithaPVCringtothehead’of-thepipe.Thereisnorecesstocausetheaccumulationofleavesandother+,debris.Whentheflyscreenhasbeenfitted,thepipeis,fittedvertically..81/Alternatively’equalpartsofriversandandpitsandmaybeused.’In.‘Zimbabweithasbeenfoundthatriversandbyitselfdoesnotadhereeasilyto:themold,strength.andpitsandalonedoesnotpermitthemortartodevelopsufficientb,1.:e.-overtheventilationholeinthecoverslabandy’mortaredinposiE,ion;3mmz.diametergalvanizedwiretsusedtotietheventpi+tothetop‘of’thesuperstructure.iI,22.Glassfiberflyscreensareusedin‘Zimbabweas.theyhavebeenfoundtobemoredurablethanaluminumscreensandlessexpensivethanbrassor’stainless*steel.InZimbabweglassfiberscreenshavelastedforatleastsevenyearswithoutrequiringreplacement.TheflyscreenmaterialmostcommonlyusedisimportedfromAustralial!;thefiberdiameteris0.342mmandithasapproximately550‘fiberspermetlengthinonedirectionand675,Intheother(aperturesize:approximately1.5x1.2mm).23.BrickSpiralLatrines.VIPlatrineshavebeensuccessfullybuiltinZimbabwewithbricksuperstructures.In’placeoftheferrocementspiral,twentycoursesof20bricksarelaidinaspiralshape2_/;aplywoodtemplate(AnnexIisusefultoindicatethepositionofthefirstcourse.Theinteriorandexteriormayberenderedwithcementmortar,ifrequired;inZimbabweusuallyonlytheinteriorisrendered.,,Inallotherrespects,thelatrineissimilartotheferrocemytversiondescribedabove,altho’ugh’theventpipecanbemadeinbrickwork-aswell:‘twentyfivecoursesof‘6b%Fcksarelaidintheformofachimneyx225mm.BrickventpipesPdleaveaninternalcrosssectionof225mmhavetheadvantagethatthey,retainheatlongerthaneitherPVCorasbestoscementpipes-andcanthusmaintainathermallyinducedcirculationofairwellinto’the.night.RecentlyaVIPlatrinehasbeendevelopedwhichusesonlybricksandmortar,.Thecoverslabismadefntheformofanarch,withformworkmadefromlocafreeds;detailsaregiveninAnnexI.Theroofslabismadeasdescribedinparagraph20.‘Thistypeoflatrine,showninFigure5,requiresapproximately900Sbricks.‘.’1.24.‘Painting.Toprotectthecement-renderedcoverslab,itispainted.uwithafairlythickcoatofblackbitumasticpaint;ytheinteriorwallsareTalsopaintedtoaheightofaround50cm.Tokeepthesuperstructuredark,‘.Itheceilingisalsopainted.black,andinorderto-msximiz’etheabsorptionof,‘solarradiationsoistheexternalsurfaceof.theasbestoscementventpipe.,’25.LatriqeOrieptation.Itisveryimportantthattheopening.ofthespiralsuperstructureeuld:notfaceeithereastorwest’whenthemorning,oraeveningsunligh;caw.pa%a%.:,thein%ePiorofthe.superstructure.andsoprovideemergentflieswit%analternativesourceoflight.Whethertheopeningshouldfacenorth.orsouthisgenerallydecidedby‘therelativepositionsof,thehouseandthelatrine,inordertoprovidemaximumprivacy.Theventpipeshouldideallyfacetheequatorsothatitreceivesthemostsolarenergy.,.-\..--.___--._26;.---.._Thelatrineshouldbe1qate.datleast2mfromtreesoro;erhangingbranches;-%s-t.seinterkerewithperoperationof‘theventpipe.,I--..L,.j-.\1l/CycloneK-MProductsPty.Ltd.,.WireblothDivision,Melbourne,Xustr*alia.,~II.21required.Ifthebricks’arelaidonedge,only15coursesof20bricksare.*b?::-11-Figure5:VIPlatrinewithbricksuperstructure,brickventpipeandbrickarchcoverslab.(Note:thedesignha8nowbeenaltered80thatthesuperstructurevallformsonesideoftheventpipe;8eeAnnexI,drawing5)-12-..u3\iP1I.-.._I_27.4*1Maintenance.The,coverslabneedstobecleanedregularly,and+otcasionallyit.needstoberepaintedwithbitumasticpaint.Theareaarounde!Jattine-should.’bekeptfree‘fromvegetation(especially:climbingplants,whichmaystop‘solarheatingoftheventpipe)..Theflyscreenshouldbeinspectedperiodicallytocheckthat.itisstillintact.InZimbabweleavesandotheritemsrarelysettleonthe-flyscreento-#restricttheair.flow.Cobwebshavebeenobservedinpipesthathavebeenl%ft,ly,ingonthegroundpriortoconstruction;theseshouldbewashe:dthroughwithwater.-Cobwe,bsareoftenfoundaroundthetopoutsiderimpfthevent’pipebutrarely,.ifever,occludethepipeitselforthemesh.SpiderslearhIquicklythatfliesareattractedtothetopoftheventriipe,(Figure6);lizardshave’-alsolearnt_thatthisisagoodplacetowaitforfood.-L.;\..J..28.,-QzistsiCurrentmaterialscostsinZimbabweareindicated-inthescheduleofmaterialsgiveninAnnex’II;theseamounttoi.Z$63(US$96)for.theferrocementv.ersion;Z$76(US$,116)forthebrickdesignwithamass‘producedACorPVCventpipe;andZ$69(US$105)forthe.br,ickdesignwitha.i_,brickvent‘pipelI.Thecost-oftheferrocementversionassumesthat‘the.superstructureformworkcanbeusedfor-50’latrines.Dependingonthelocal‘soilconditions,betweentwoandnineman-daisofunskilledlaborarkrequired.forexcavationofa1.5mdiameterx3.’mpitandthreeandsixman-daysof‘-’!*-@y.skilledandunskilledlaborrespectivelyforthecoverslab’and.complet‘,superstructure(seeAnnexII)..*AcurrentZimbabweanrates(Z$130and30perL.monthforskilledandunskilled‘laborrespectively),thets.;,:’_BrickVIPlatrinewithAC‘.’‘Y$$’1.09US-$;166orPVCventpipeLr.BrickVIPlatrinewithbrick._’,Z$’102;_Ius+185ventpipe.-\*.,:-29.hGrotidwaterArias.In~s,oepartsofZimbabwe,thegroundwater-tableisclosetothesurfaceatcertaintimesoftheyear.Intheseareasit’hasbeenfoundthatraisingtheco?erslab0.5mabovegroundlevelisaneffectivestrategy(Figure7),‘Undersuchconditionstheventpipe,hasbeenfoundtobeSt911abletocontrolodorsandflies,evenwhenthewatertable.iisveryclosetogroundlevel.030.-’CurrqntDesignTrends.Considerationispresentlybeinggivento(a)thedesignofiLamoveablespiralsuperstructure.foruseinlow-densityurban.’*areaswherethe,reisspaceoneachplotforatleasttwoalternatingpit+-.sites;(b)acoverslabwhichfacilitatestheupgrading.ofthelatrinetoapour-flushtoilet:/;and(c)improvingtheefficiencyofdigestioninpits--by._‘2*.‘9=r/‘Zimbabweancostshave,beenconvertedattheApril.198rateofexchange;Z$1=US$1.52.ll.J.L’,:’,21-SeeAnnexIV,Volume2.tr).4:I6Figure7:VIPlatrinewithraisedsuperstructureforuseinhighgroundwatertableareas.,lining-thepitwallsandbasewithcement.mortarandconnectingthepittoasoakawaywithashortlengthofpipe(initialobservat.ionsinZimbabweofthismodifiedVIPlatrinesuggestthatitcouldbeverysuitableforperiurbanareaswherehousingdensitiesarehigh).!31.CommercialLatrineKit.AversionoftheferrocementspiralVIPlatrineiscommerciallyavailable1/inZimbabwe(Figures8and9).Thekitcomprises(aapreshapedsuperstructurespiralsheetof100mmsteelmesh(bardiameter:4mm).tightlycoveredincottonorhessianfabric;(b)a250mmventpipealsomadefrom100mmsteelmeshandsimilarlycovered;(c)a1.5mdiametercircularroofsheetof-thesamematerialandcovering;and(hformworkwithintegralreinforcingforthecoverslab(1.5mdiameter)andwithaperturesfortheventpipeandthesq.uathole.Thepitisnormallyexcavatedtoadepthof3.3mandadiameterof1.1m.Thepitislinedtoatleast1mwithcementmortarandabrickringbeamislaidasdescribedin.paragraph14.Whenthekitisdeliveredtothesite-concreteisplacedinthe.:_coverslabmold;when*theslabhascureditisplacedoverthepitandthesuperstructureandroofsteelworkthenpla,cedinposition.Cementmortar(1partcement,2partssandandaproprietaryadditivetoincreaseworkabilif!y;0.5-0.6wateY/cementratio)isapplied.bybrushtobothsidesofthesuperstructureandrooffabricinthinlayerstogiveatotalthickness..between20and25mm.Theventpipeissimilarlycoatedontheoutsideand,whendry,placedinposition;thewholelatrinesuperstructureisthengivenafinalapplicationofcementslurry.32.ThecommerciallatrinekitcostsZ$60(US$91)2/.,Labor,costsaddZ$27(US$411,assuming2man-daysforpitexcavation;materials(fourbagsofcement,sand,aggregateandbricks)addafurtheri$,21(US$32).Thus,thetotalcostofthecommercialkitlatrineisZ$108(US$164).nalSpirals33.Althoughthespirallapractice,theircostsaretooofZimbabwe,andthereforedeveloped.Theyareallbasedonapartfromtraditionalcflyscreen,nails,tyingwireanditemscostatotalofZ$5(US$8).wattlespiralsuperstructure;(d)atha-tchroof;and(e).acementrenderedventpipemadefromreeds.Aworkingdrawingandschedule*of,materialsaregiveninAnnexesIandIIrespectively,-I.v.KitformShelterb.andSanitation(ht.)4Ltd.,POBoxAY.51,’Harare.m*e2,..--Y.\.April1981prices;kitpricef.o.r.Xarireandexclusive,oflocal,salestax(currently10%).....a)/.e--:,/-,.-...LFigure8:VIPlatrinemadefromcommerciallyaa~ilablelatriiekit.-_._‘._-7-17-\\\*.\\IIIII///Concretecoverslaba..*Figure’9:SketchplanofthecommercialVIPlatrineshowninFigurei.ilfFigure10:MudandwattlespiralVIPlatrine.ThatchedroofFlys;.reenCement-renderedreedventpipe-MudandwattlesuperstructureRectangularpitTimbercoverslabtpiialIIT.Isi;I..aFigure11:ExplodedschematicdiagramofmudandwattlespiralEklatrine:....,-20-35.Thepitdimensionsar-e1.5mx0.6mx3m.Itisimportanttoensurethatthelongitudinalaxisofthe:piJliesnorth-south,topermitcorrectorientationoftheopening(seeparagraph25).Oncethepithasbeenexcavated(and,ifnecessary,linedI/,thecoverslabisformed.Thisisdonebyplacingtwologs,measurin62.1po,2.3mlongand-approximately100mmindiameter,alongthepit300mmap-art,suchthattheiruppersurfaceisflushwithgroundlevel(thisnecessitatesremovingsoilatbothendsofthe,pit).Logsmeasuring1.2mlongandrzughly10.0mmindiameter,.arethenplacedacrossthelongitudinallogswithoutgapsandnailed*ortiedtothem;aperturesfortheventpLpeand,squatholeiareformedattheappropriateplaces(seeAnnexIbyusingpairs#shorterlogswhichcometotheinneredgeofthelongitudinallogs.Thewoodenlogsusedshouldberesistanttotermiteandfungalattack;inZimbabwemopane(Co~lophospermummo.pane)andmususu(Terminaliasericea)arecommon1.yused2/.cr.*d36.Oncethelogsareinposktion,thesuperstructureisthenbuilt.Some30to40timberpoles,1.8mlongand50to80mmindiameter,are-erectedinthespiralshape,nailedtothe2overslabandtiedtogetherusing18swg(1.219mm)wire.Thelowerendsofsome,ofthepolesshouldberoughlycuttoapointsothattheymaybefirmlywedgedbetweenandnailedtothecoverslablogs.Theuppersectionsof..thepolesarekeptinplacebyfasteningringsofgreensaplingsaboundthem.Theroofisthenmadefromgumpolesabout30mmindiameterwhicharepliableandcanbeeasilyshapedto.thedesiredcircularform.Thediameteroftheroofbaseis2manditsapex0.5inabovetheplaneofthebase.Theroofismadebyweavingandtying1.2mlonggumpolesbetweenfivecirclesof.greensaplings.225mmapart.Theroofisthenthatchedwithstrawordrygrassandplacedonandtiedtothesuperstructure.ThisprocedurewasadoptedasitisthetraditionalmethodformakingroofsinruralZimbabwe.Thethatchinghastobeverydensetokeep,thesuperstructuresufficientlydarkforgoodflycontrol.37.Oncethesuperstructure,androofiscomplete,theapplicationofmud_begins;inZimbabwetraditionalpracticeintheruralareasisnott.oueAsoilfromthegroundbutfromtermitehillsasthisisfoundtohaveubetter-adhesivepropertiesandgreaterdurability.Thesuperstructureisfirstplasteredwithmud,bothinsideandoutside.Thecoverslabisthenalsoplasteredwithmudsuchthatthefloorslopesinalldirectionstothesquathole.Asthemuddries,cracks.appearandthesurfacesareplasteredw$thmudagaintofillthesecracksandtoprovideincreasedstrength.Themudjsallowedtodryoutandallsurfacesarethenplasteredwithathincoatof11Pitlining(seeparagraph14)requiresanadditionalhaJfbagofcement(Z$1.7,US$2.5).421Inruralareasofdevelopingcountrieslocalknowledgeofsuitabletimbersandtermiteprotectionmethodsisgenerallyverygood,anditisalwaysworthaskingthelocalpeoplewhattimberstheyuseandwheretheyusetheminbuildings(seeP.A.Campbell,Somedevelopmentsintropicaltimbertechnology,AppropriateTechnology,2(3),21-23,1975).InZ4mbabwelessresistantwoodssuchastheindigenousMsasa(Brachvstepiasuiciforlmis)Orgumwood(Eucalyptusipp.)arecpmmonlyprotectedagainsttermiteattackbycoatingthemwithliberalquantitiesofwoodaih,usedeng@e,oil,coarsesalt,carboliniumordieldrin.m-_.cementmortar(1partcement,6partssand).‘Thecoverslab~.isthenpaintedwithblackbitumasticpaint..i38.Theventpipeisconstructedfroma2.4mx0.9m(8ftx3ft)matoflocalreedswovenwithstringorwire.Thematisrolleduparoundfourorfive280mmdiameterringsofgreensaplings.toformaventpipeofapproximately.28cminternaldiameter(Figure121,andthe.flyscreeniswiredontooneend.Theventpipeisthenplasteredaroundhalfitscircumferencewithcementmortar;whenthishasdrieditisplacedinpositionandtiedtothesuperstructure,and‘thentherestoftheventpipeisplastered.39.Finally,theexposedpartsofthecoverslabarecoveredwithsoilwhichisplacedsoastoslopegraduallyawayfromthelatrinetothesurroundinggroundlevel.Grassisthenplantedtoprovideprotectionagainsttherain.,40.ThatchedLatrine.This-latrine,shownin.Figure13,isverysimilartothemudandwattle‘latrine,theonlydifferencebeinginthesuperstructure.Thespiralismadefromgumpolesplacedatapproximately150tmrncentres.andheldinpositionwithhorizontalsaplings,alsoat150mm-.centres,whichareinterwovenwithand_,tiedtotheverticalme,mbers.Theexteriorisdenselythatchedtoexcludelight.ThisversionoftheVIP.alatrineisespeciallysuitableinareaswhere-timberisinshortsupply.41.AnthillLatrine.Inareaswheregrassidpolesareveryscarce,thesuperstructurecanbemadeofwell-kneadedanthillsoilbuiltupintheformofsausagestothespiralshape.Theventpipeismadeinasimilarfashion’,coilsofanthillsoilbeingwoundina,ciEcletoformthetube.=42.Low-CbstBrickLatrine.Locallymadeburntbricksarecom’monyavailable:inruralareasofZimbabweandtheircostisaquarterofthatoffactory-madebricks.Theycanbesatisfactorilyusedtobuilda,spiral-superstructureovertherectangularpit;thecoverslabandthatchroofremadeasdescribedaboveinparagraphs35and36..\43.Maintenance.TheruralspiralVIPlatrinesrequireregular-*maintenancetothecoverslabandsuperstructure;thisinvolve:srepairingany~itseW~a%dteartotheslab,walls,roofandvent.pipe.Sincehearchitecturalstyleoftheselatrinesisessentiallythesameasthatoftheirhouses,thehouseholdershavethenecessaryskillstodoregularmaintenanceworkonthelatrines;normallythisisdoneonceayearaftertherainyseason.TheonlyImaintenanceworkaboutwhichinstructionisPlatrine.,-Tlieseincludethe-,following::.’4r(1)Adescriptionisincludedintheschoolcurriculum(gr,ade6);Models.arebuiltinclassrooms.Inanongoingprogram,schoolsintperural.areasarebeingservicedwithVIPlatrines.-r.E--J-_L.-23-.alci..c7(2)(3)(4)(5).%(6)-24-.TWOfilms-oneontheferrocementVIPlatrine,theotheronthemudandwattledesign-havebeenmadefortheHomeServicesMobileCinemaunit,whichhasatargetaudienceof1.5millionviewersperyearinthe.ruralareas.ThefilmsareinEnglishandthetwomostcommonlocallanguages,ShonaandNdebele;InstructionleafletsareavailableinEnglish,ShonaandNd.ebele...pHealthAssistantsoftheMinistryofHealtharetrainedinaVIPlatrineconstructiontechniques.LManydemonstrat