水污染处理文献综述英文.docx

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,easy