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生物膜法处理有机废气英语精编文档doc
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Biofilmtreatmentoforganicwaste
LiRuixueCaiShenjianShenCheng
Abstract:
Hazardorganicwastehasbecometheconsensus,treatmentoforganicwastepollutionisoneofthekeyenvironmentalwork.Thispaperdescribesthesourcesoforganicwasteandhazards,describestheprinciplesofbiofilmtreatmentoforganicwaste,advantagesanddisadvantages,discusseditsresearchstatusanddevelopmenttrends.
Keyword:
Biofilm;Organicwaste;Treatment
1:
Preface
Boiofilmorganicgasmainlycomesfromthepetroleum,thechemicalindustryintheproductionprocessemissions.Ithasthecharacteristicthattheorganicmattercontentofupsanddowns,withcombustible,haveacertaintoxicityandtherewillbesomeodor.Chlorofluorocarbonemissionswillcausethedestructionoftheozonelayer.Petrochemicalproductionprocessandstorageequipment,printingandotherrelatedtopetroleumandchemicalindustry,theuseoforganicsolvents.,Petroleumproductsforavarietyoftransportationfuelsallabovethesewillcauseorganicgas.【1】
Themaincomponentsoforganicwasteareformaldehyde,acetone,aceticacid,ethyl-ester,additiveandotherorganicgasescontainingcarbonandoxygenandsoon.
Organicgasdamageplantleaftissueanddestroytheozonelayer,Fortheharmtohumanbodyisreflectedinmanyaspects.Benzeneishighlytoxicsolvents,evensmallamountscancauselong-termdamagetothehumanbody,itcanaccumulateinthebonemarrowandthenervoussystem,damagehematopoietictissueandnervoussystem,causeneurologicaldisorders,reducetheamountofwhitebloodcellsintheblood,platelet,worseissufferingfromleukemia.PAHandorganiccompoundshavestrongcarcinogenesis.Benzoicacidcanmaketheproteininacelldeformationorsolidification,thesystemicpoisoning.Nitrilescancausebreathingdifficulties,cancausesuffocationseriously,lossofconsciousnessuntildeath.Glycolethersolventinthehumanbodycanbeformedafterthemetabolismoftoxic,causepermanentdamagetothecirculatoryandnervoussystemofthebody.Femalereproductivesystemwouldalsobeaffected,seriouscanleadtoinfertility.Organicphosphoruscompoundscanreducebloodcholinesteraseactivity,resultinginnervoussystemdisorders.Aboutorganicsulfurcompounds,lowconcentrationofthiolcancausephysicaldiscomfort,butdeathathighconcentration.Toluenediisocyanatewithlowvaporpressure,haveastrongstimulatingeffectonthehumancornea,causingeyeirritation.Steamintothehumanbody,willdamagethefunctionofhumanliver,kidney,long-termexposuretotoluenediisocyanatesteamhighconcentrationsofcarcinogenic.
Therearetwomaintypestotreatorganicwastegas:
oneisrecovery.Therecoverymethodisphysicalmethod,weusetheadsorbentandselectivelypermeablemembranetoseparatevolatileorganiccompoundsinacertaintemperatureandpressureincludingactivecarbonadsorption,condensationmethod,Pressureswingadsorptionmethodandbiofilm..Anotheriseliminatetheseorganicwasteweturnorganicmatterintocarbondioxideandwaterusingoflight,heat,catalystandmicrobes,likelightdecompositionmethod,thethermaloxidationmethod,catalyticcombustionmethod,biologicaloxidation,coronamethod,plasmadecompositionandsoon.【2】
2:
Biofilmtreatmentoforganicwaste
2.1Mechanismofbiofilmtreatmentoforganicwaste
MechanismofbiofilmtreatmentoforganicwastewasfirstputforwardbyOttengraffromNetherlands.Thebiofilmtheorybiochemicalmethodoforganicwastegaspurificationprocessintothreesteps:
(1)First,theorganicpollutantsintheexhaustgasoncontactwithwateranddissolvedinwater.Thatis,bydiffusionintothefilmbytheFilm.
(2)Dissolvedintheliquidfilmoftheconcentrationdifferencebetweentheuseoforganicpollutantsingredientsspreadtothebiofilm,andwasoneofthemicroorganismstocaptureandabsorb.
(3)Microorganismsintoorganiccontaminantsinmicrobialmetabolicprocessesastheirenergyandnutrientsarebrokendownbybiochemicalreactionsandeventuallyconvertedintoharmlesscarbondioxideandwater.
Later,SunPeiShi,whonotedthatsomedonotdissolveinwaterorwater-solubleorganicmatter,difficulttousefilmdiffusionmethodtoexplain.Sotheyproposedadsorption-BiofilmTheory.Andbasedonthetreatmentoflowconcentrationsoftoluenegasexperimentstoestablishadynamicmodel.【3】Highlightsofthetheoryis:
(1)Organicpollutantsintheexhaustgasreachesthemembranebydiffusionandadsorptiontothemoistbiofilmsurface.
(2)Organicmatteriscapturedandabsorbedbymicrobes.
(3)Microbialdecomposescontaminantsandfinallyturnintocarbondioxideandwater.
2.2Advantagesofbiofilmtreatmentoforganicwaste
(1)Biodiversity:
Bothaerobicandanaerobicbacteria
(2)Biofilmlowmoisturecontent,alargebiomassperunitvolumemakeithaslargerprocessingcapacity.
(3)Processismorestable,lessconsumption,highremovalefficiency.
2.3Thedevelopmentoforganicwastegastreatment
Atpresent,processingtechnologyoforganicwastegasgeneraldevelopmentintotwocategories:
decompositioneliminationandconcentrationandrecovery.Decompositionisusedasthelight,electricity,eliminatingheat,plasmaandmicroorganismsoftheorganiccompoundsintocarbondioxideandwater.Concentrationandrecoveryisbyadsorption,absorption,condensationandmembraneseparation,theorganicmatterconcentrationrecycling.
Decompositionofeliminatingtreatmentwithoutrecyclingoforganicwastegasvalue,itstechnologyincludingdirectcombustion,catalyticcombustionmethod,coronamethod,plasmamethodandbiologicalmethod.Concentrationandrecoveryfortreatmentofhighconcentrationorganicwasteandrecyclingvalue,itstechnologyabsorptionmethod,adsorption,condensationandmembraneseparationmethod.
Organicwastegastreatmentnorecyclingvalue,suchasodorgasbycatalyticcombustionmethod,althoughthecleaningisthorough,butthecostisrelativelyhigh,butalsotheexistenceoftwopollution;corona,plasmatechnologyhasabetterapplicationprospect,buttherearestillsomedistancefromthepracticalaspects;biologicalmethodofsavingenergy,lowoperationcost,rarelyformedtwopollution,treatmentoflowconcentrationorganicwastegas(<3g/m-3)effectisbetter,inEuropeandtheUnitedStates,Japanandothernationshavebeenputintoindustrialoperation.Thetreatmentoforganicwastegasbyusingbiologicalmethodalthoughlate,buttheprospect,becauseofthelowconcentrationorganicindustrialwastegastreatmentandlackofeconomicalandeffectivemeasures,biologicalmethodcanplayarolein[4]isveryimportant.
Biologicalmethodsmainlyincludebiologicalfiltration,biologicalwashingmethodandbiologicaltricklingfilterprocessofthreetypes,includingbiologicalfiltrationandbiologicaltricklingthroughsurfacemembranebiologicalfillerinmicrobialtreatmentoforganicwastegas,sothesetwokindsofmethodsareknowncollectivelyasthebiologicalmembranemethod[5].
2.4Themainprocessform
Therearetwoformstotreatorganicgas:
Biofiltration,Biotricklingfiltration
(1)Biofiltration.Process:
organicwaste-humidifier-biofilter-purgegasemissions.Themaindeviceisahumidifierandbiofilter.Organicwastegetswetfirstinahumidifier,andthenintothebiofilter,Fillerlayerinthefilterisattachedwiththebiofilm,Liquidsubstantiallystaysstationaryorslow-speedflow.Moisture,pH,nutrientcanbesuppledifitisneeded.Mustensuregasgoesthroughfiltercontinuously.Thefillercanbesoil,plasticfilter,ceramicfilter,granularactivatedcarbon,peat,compost,etc.Thicknessisabout1m,theareaisdesignedbythegasflowandtheeffectoftreatment.
(2)Biotricklingfiltration.Vaporflow:
organicwaste-Biologicalfiltrationtowerbottom-purgegasemissions.LiquidFlow:
Circulatingfluid-Biologicalfiltrationtowerbottom-Circulatingliquidtank-Biologicalfiltrationtowerbottom(cycle).Instructure,biologicalfiltrationtowerbottomissimilartobiofilterbutwhatdifferentisbiologicaltricklingfilterthecirculatingfluidsprayingfromthetopdown,theflowthroughtheinsideofthefillerlayer.Organicwastefromthebottomtoenter,afterpassingthroughthepackinglayeroutthroughthetoprow.Becausebiologicaltricklingfilterporeslargerthanpackingbiofilter,sothesmallertheresistanceofthegasthroughthebed.Sincetheliquidflowiseasytocontrolthereactionconditions(suchaspH,nutrientconcentrations,etc.).Biologicaltricklingfiltertreatmentofhighloadoforganicwasteisstrongerthantheeffectofbiologicalfiltration.
3:
Majordesignandcraftparameters
3.1Filter
Biofilmfillerchosenshouldmeetthefollowingcriteria:
(1)Bettersurfacepropertiesofthefiller,suitableforthegrowthofmicroorganisms;
(2)Thelargesurfaceareaoffiller;
(3)Therearecertainstructuralstrengthandcorrosionresistance;
(4)Hasahighporosityandlowbulkdensity;
(5)Easiertoobtainandlonglife.
Therearetwomainfilters:
naturalfillersandartificialfillers.Naturalfillersincludesoil,compost,peatsubstancecontainingnutrientsingeneral;Artificialfillerlikeactivatedcarbon,diatomaceousearth,coke,polystyreneandpolyurethanefoambeadsneedanadditionaladding,becauseitdoesnotcontainnutritiousmatter.Somenewlydevelopedfillersuchasactivatedcarbonfibersandadheredtotheporoushydrophobicpolypropylenefilm.Further,addingactivatedcarbon,coke,etc.Intheconventionalfiller,thefillercanimprovetheperformanceandextendthelifeofuse.
Fillershouldbeusedtocontrolthehumidity,thehumidityistoolow,willmakemicrobialinactivation,fillersshrinkagecracking