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CanadianJournalonEnvironmental,ConstructionandCivilEngineeringVol.1,No.3,July201058AReviewonPropertiesoftheDigestionProcessintheUp-FlowAnaerobicSludgeBed(UASB)ReactorS.A.Habeeb(a),AB.AzizBinAbdulLatiff(b),ZulkifliBinAhmad(c)FacultyOfCivilAndEnvironmentalEngineering,UniversityTunHusseinOnnMalaysia(UTHM).(a)postgraduateresearcher,email:sinan_env@yahoo.com(b)Professor,email:aziz@uthm.edu.my,(c)lecturerAbstract:TheAnaerobictreatmentisconsideredoneofthemostefficientmethodsfortreatingseveraltypesofeffluents.Thisisduetoitscopefortreatinghighrateofsimplybiodegradablematterswastewater.Severalresearcheshavebeenwidelyconductedinordertoenhancetheperformanceoftheanaerobicprocess.Theup-flowanaerobicsludgeblanket(UASB)technologywasrecentlyconsideredasthemostpopularmethodinwhichthehighestrateoforganicmaterialscanberemoved.Nonetheless,thelongstart-upintervalofUASBreactorrequiresmoreunderstandingofthebiologicalprocessinsidethereactor.ThispaperreviewsspecificallytheMethodibilityofUASBreactorasanattractivetechnology,aswellasthemostsignificantfactorscontrollingtheprocessi.e.,pH,organicloadingrate(OLR),hydraulicretentiontime(HRT),mixing,andtemperature.Intheotherhand,thispaperalsopresentsindetailssomeofthemajordrawbacksofusingthismethodfromenvironmentaloroperationalconsiderationsinordertoprovideanessentialunderstandingfortheprocessaswellastofacilitateemployingthistechnologybyresearchers.1.IntroductionThemethodofanaerobicwastewatertreatmenthasbeeninitiallyimplementedaroundonehundredyearsago.WherebyBuswetl,1957;citedinWang,1994indicatedthatitwasfirstusedbyLouisH.Mourasat1860wherewastheinventionoftheseptictanksystem(Mourasautomaticscavenger7)infrance[1].Subsequentlyseveralinvestigationshavebeenseriouslyconductedinthepastfewdecades.Sofaranaerobicwastewatertreatmentprocessesareconsideredasthemostpopulartreatmentmethodsespeciallyintropicalenvironmentcountries[2].Recently,anaerobicwastewatertreatmenthasbeenbroadlyimplementedinmostareasofwastesespecially,thehighratewastewaterwhichismainlycomprisedtheindustrialwastewater[3].Anaerobicprocessescharacterizedbyitslowproductionofsludge,anditsgenerationofenergycomparingwiththeaerobictreatment[4][2].ThedevelopmentoftheuseofanaerobicwastewatertreatmenthadbeenstartedinNetherlands,wherebyTheUASB(up-flowanaerobicsludgeblanket)systemwasfirstlyusedontreatingawastewaterfromasugarrefineryinNetherlands1978.Subsequently,ithadbeenimplementedinthetreatmentofbeverageindustry,CanadianJournalonEnvironmental,ConstructionandCivilEngineeringVol.1,No.distilleriesandfermentationindustry,foodandpaperindustrywastewateranaerobictechnologyhasbeenexpanded,whereitcomprisedthetreatmentofchemicalandpetrochemicalindustryeffluents,andtheUASBconcedomesticwastewatertreatmentespeciallyinwarmclimatesintropicalcountrieslastdecades,up-flowanaerobicsludgeblanket(UASB)technologyhasbeenall-roundperformanceforhigh-loworganiccontentwastewatertreatmentthatarespecificallymentionedinliteraturehavedirectlybeencontrolledtheprocess2.UASBbioreactorTheUASBprocesshasbeendevelopedbyDr.GatzeLettingainthelate1970'sattheWageningenUniversity(TheNetherlands).TheUASBreactorismainlyclassifiedunderthebiologicalreactors,duetoitsbiologicaltreatmentofwastewater.Recently,biologicaltreatmenthasbeenmajorlyobtainedamassiveattentionbytheresearchersduetoitssustainabilityenergydemand,simpleconstruction,lowcosteffective,andhighremovalefficiencyconfirmsitstoleranceontreatinghighrateaswellaslowratewastewaterwithvariOfthese,asurveywasdonebySankar,2007toinvestigatethemostusageofUASBreathan108researcheswasindicatedtotherelativeproportionofworkdoneduring1999in(Fig.1)[11]..Figure1:Relativeproportionofworkdoneduring1999Themainfactorsaffectingthereactorperformancecomprises:thegranulationdevelopmentinthesludgebed,thewastewatercharacteristics,theeffectofthenutrients,andtheotherenvironmentalfactors.Themostconcernfactoristhegranulationprocesprocess[12].VariousanaerobicpurebacterialhaveCanadianJournalonEnvironmental,ConstructionandCivilEngineeringVol.1,No.3,July201059dfermentationindustry,foodandpaperindustrywastewater[5].Recently,theuseofanaerobictechnologyhasbeenexpanded,whereitcomprisedthetreatmentofchemicalandpetrochemicalindustryeffluents,andtheUASBconceptisalsoconsideredmorethansuitableforthedomesticwastewatertreatmentespeciallyinwarmclimatesintropicalcountries[6].Recently,overtheflowanaerobicsludgeblanket(UASB)technologyhasbeencommonlyused,duetoitsloworganiccontentwastewatertreatment[7].Theoperationalparametersthatarespecificallymentionedinliteraturehavedirectlybeencontrolledtheprocess[8]TheUASBprocesshasbeendevelopedbyDr.GatzeLettingainthelate1970'sattheWageningenUniversity(TheNetherlands).TheUASBreactorismainlyclassifiedunderthebiologicalreactors,duetocaltreatmentofwastewater.Recently,biologicaltreatmenthasbeenmajorlyobtainedamassiveattentionbytheresearchersduetoitssustainability[9].UASBreactorcharacterizedbyitslowenergydemand,simpleconstruction,lowcosteffective,andhighremovalefficiency[10]toleranceontreatinghighrateaswellaslowratewastewaterwithvariouskindsofpollutant.