水污染处理文献综述英文.docx
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水污染处理文献综述英文.docx
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水污染处理文献综述英文
Applicationofmulti-soil-layersystem(MSL)inruralwastewatertreatment
Abstract:
withthecontinuousimprovementoflivinginruralfarmers,thewaterconsumptionofresidentsisincreasing,ruralsewageemissionswillcontinuetoincrease,ifnottreateffectively,thewaterenvironmentinruralareaswillbeseriousdeteriorated,andinfluencethelifequalityofruralresidents.Inthiscasethispaperpresentsadecentralizedsewagetreatmentsystem,multi-soil-layersystemtechnology(MSL)applicationintheruralsewagetreatment,thispapersummarizesthenewtechnology,youcanbetterunderstandandpractice,especiallyinthedevelopingcountrieswhereisinneedofthistechnology.Intheforeseeablefuture,itcanprotectpublichealthandthesustainabledevelopmentoftheenvironment,anditalsoprovidesanewwayforruralsewagetreatment.
Keywords:
ruralsewage;multi-soil-layeringsystem;distributed
1.Introduction
Inrecentyears,withthecontinuousdevelopmentofeconomy,people'slivingstandardscontinuetoimprove,ruraleconomicdevelopmentisalsoveryrapid,buttheruraleconomicdevelopmentandenvironmentaldevelopmentisnotsynchronized,seriousruralwaterpollution.Whilehightechnicalsewagetreatmentplants,suchascentralizedsewagetreatmentplantsareinvolvedinlargeinvestmentcosts,highoperatingcosts,Becauseofeconomicconstraints,suchsystemsarelesssuitableforlivestockfarmsandsmallcommunitiesinruralareas.Whilethemulti-media-soillayersystem(MSL)sewagetreatmentsystem,thisdecentralizedsewagetreatmentsystem,ithaslessinvestment,lowoperatingcosts,highhandlingload.Besides,theutilitymodelovercomesthedefectsofthepriorsoilpercolationwhichiseasytobeblockedfromthespacestructure.ThesewagetreatmentsystemisonekindofthepurificationtechnologyofseweragetreatmentsoildevelopedinJapanintwentiethCentury,thesoilsystemwillbemodularized,andthemoduleissetuparoundthewaterinthesoillayertoavoidclogging,andaddingnaturalorganicmaterialstosoilmodulescanimprovethepurificationabilityofthesystem.
TheMSLsystemconsistsofaPermeablelayer(PL)andasoilmixinglayerblock(SMB),ThePermeablelayerisusuallycomposedoflargerparticlesfillerssuchasgravel,pumice,perliteandzeolite.Higherporositycaneffectivelypreventcloggingofthesoilwaterlayer.Atthesametime,theformationofaerobicenvironmentisconducivetoorganicdegradation.Themixedlayersoilismainlypackingsoilmixedwithother20%-30%othermaterialssuchasactivatedcarbon,wood,ironandothermaterialorsoilwithlocalresources.Theorganicmaterialaddedinthesoilmixedlayercanimprovethebiologicaldecompositionandadsorptioncapacityofthesystem,andcanalsoimprovethesupplyofhydrogenintheprocessofnitrogenremovalandpromotetheremovalofnitrogen.
TherearemanyresearchesonMSLsystemtreatingurbansewage,livestockwastewaterandriverwaterathomeandabroad.ResearchersinChina,YeHaietal[1]studiedtheeffectofsurfaceloadonpollutedriverwatertreatedbymulti-soil-layersystem.SongYing[2]hadstudiedthetreatmenteffectofmultimediumsoilinfiltrationsystemforturtlebreedingwastewater.ZouJun[3]alsopointedoutthatmulti-soil-layermaterialselectionwillhaveacertainimpactonthedomesticsewagetreatmentefficiency.Inforeigncountries,especiallyinJapan,ThailandandIndonesia,MSLsystemshavebeenusedtohandlevarioustypesofwastewater,butthedomesticofthistechnologyinsewagetreatmentinruralareasthereisnocomprehensivestudy,ThisarticlethroughtotheMSLsystemtechnologyprocessingruraldomesticsewageresearch,inordertoprovidesometechnicalsupportfortheMSLsysteminthepracticalapplicationofruralsewagetreatment.
2.1characteristicsofruralsewage
Foralongtime,China'spollutioncontrolonruralattentionandinvestmentfarlessthanthecity,96%ofthevillageswithoutdrainagepipenetworkandsewagetreatmentsystem,Therandomdischargeofdomesticsewagehasbecomeoneofthemainreasonsforthedeteriorationofwaterqualityinthebasin,andisalsoanimportantfactorcausingtheruralwaterenvironmentpollutionandlakeeutrophication.Atthesametime,itseriouslyaffectsthesafetyofproductionandlivingintheruralareas,andseriouslyaffectstheeconomicdevelopment.ThemainfeaturesofruralsewageinChinaare:
(1)Theamountishugeandincreasesyearbyyear.Statisticsshowthatin2002.Thereare3.205milliontonsofnationalruraldomesticsewagedailyemissions.Thetotalnitrogenemissionisabout283.1t,totalphosphorusdailyemissionisabout56.6t,basicallywithoutanytreatmentdirectlydischarged.
(2)Waterqualityandwaterquantityfluctuationarehuge.Ruralsewagewaterisnotstable,differentperiodshavedifferentwaterquality,generallydonotcontainheavymetalsandtoxicandharmfulsubstances,butcontainsmoresyntheticdetergentandbacteria,viruses.
(3)Moresources.Inadditiontohumanfeces,kitchengeneratedsewage,therearehouseholdcleaning,domesticwastelandfillleachategeneratedsewage,whichwillthenentertheriverpartofthesewage,willcausegreaterpollution.
(4)Lowtreatmentrate.Partofthesystemcannotrunlowtemperature,ruralsewagedailyvariationcoefficientandseasonalvariationcoefficient,thesystemafewtimehighloadoperation,ifthereislittlesewage,itwillstoprunning[4].
(5)Wideandscattered.Scatteredgeographicaldistributionofvillagescausedsewagedispersionanditisdifficulttocollect.
2.2themainsourceofruralsewage
Ruralsewagereferstotheformationofsewageoftheruralareasinthelifeandproductionprocess,includingruralproductionwastewaterandruraldomesticsewagetwoaspects.Ruraldomesticsewagereferstotheresidentslivingintheprocessoftoiletdischargeofsewage,bath,laundryandkitchensewage,etc.Ruralproductionsewagereferstolivestockandpoultrybreeding,aquaculture,agriculturalproductsprocessingandotherhighconcentrationoforganicwastewater.BecauseChina'srurallivingisscattered,ruraldomesticsewageshowedasmallamountandwidedispersion.Lackofappropriatesewagecollection,treatmentfacilities,domesticsewagewithouttreatmentwillbefreetodischarge,thehealthofruralresidentstobringgreaterharm.Atthesametime,ruralsewageproductionalsoposesagreaterthreattotheruralecologicalenvironment.
2.3maintechnologiesofdecentralizeddomesticsewagetreatment
Beginningin1970s,Japan,theUnitedStates,Europeandotherdevelopedcountriesontheuseofdecentralizedsewagetreatmentofruralsewagetreatment,hasaccumulatedalotofexperience,achievedgoodresults.TheUnitedStatessincethemid-20thcenturybegantheconstructionofruralsewagetreatmentfacilities,in1972promulgatedthefirstcompletecleanwater,thenaccordingtothedistributedprocessingtechnologyin2002promulgatedthedecentralizedsewagetreatmentsystemapplicationmanual[5].1987,InDenmarkpromulgatedadecentralizedsewagetreatmentguidelines[6].Germanyfrom2003toimplementthedecentralizedneedleinfrastructuresystemprojectresearch,usemembranebioreactorpurificationtotreatremoteruralsewage[7].Australiaproposedasewagetreatmentlandusesystem[8].WhileresearchandapplicationofruralsewagedecentralizedtreatmentinChinabeganinlate1980s,Comparedwithdevelopedcountriesandregions,therearestillmanygapsinlawsandregulationssystem,technicalstandardsystemandmanagementandservicesystem.Inrecentyears,domesticscholarshavedonealotofresearchonruraldomesticsewage,andputsforwardsomematureprocessingtechnology,includingaerobicbiologicaltreatment,anaerobicbiologicaltreatmenttechnology,soilinfiltrationtechniqueandphysicalandchemicalprocessingtechnologyetc.Therearemanyscholarsinthemulti-soil-layersystemimprovementandapplicationdevelopmentoftheJapanese,ithasalsodonealotofresearch,somescholarsfoundthroughexperiments:
toearthwormsoilinfiltrationlayercanalsosolvetheproblemofblockageofMSLsystem,butalsocanguaranteethewinteroperationeffectinwinter[9-10].
2.4Multi-soil-layersystem(MSL)technology
2.4.1Structuralcharacteristicsofmulti-media-soillayersystem
Multi-soil-layertreatment(MSL)systemisakindoflandsewagetreatmentsystem.MainlycomposedofPermeablelayer(PL)andasoilmixinglayerblock(SMB),Fromtoptobottomarewaterprooflayer,gravellayer,soillayerandmixedlayer(twoalternatelyarranged),inaddition,theMSLtechnologyhasacertainterrainfallfromtheinlettotheoutlet,mainlybythedropletwatercanautomaticallyflowinthesystem,atthesametimetopurify[11].
2.4.2Purificationmechanismofmulti-soil-layersystem
WastewatercontainshighconcentrationsofBOD,COD,ammonianitrogen,phosphateionsandorganicmatter.WhenthewastewaterintotheMSLsystem,theorganicmatterinwastewatercanbeadsorbedonthesurfaceofzeoliteandsoilthroughphysicalandchemicaleffects,followedbydecompositionofsoillayerinmicroorganism,andphosphorusremovalismainlythroughthesoillayerofironisoxidizedtoferrichydroxideaftertheformationofinsolubleiron,thenadsorptioninwastewatertheformationofphosphatecoprecipitation.Nitrogenremovalismainlythroughnitrificationanddenitrificationbyammoniaion,andfinallyreducedtonitrogendischargesystem.
2.4.3Advantagesofmulti-soil-layersystem
Multi-media-soillayersystemisusedtotreatwastewaterfromtraditionalsoilinfiltrationsystem.Ithasthedisadvantagesoflowtreatmentload,largeground,eas
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