Actiflo+Steel+Plant+Paper.docx

Actiflo+Steel+Plant+Paper.docx

《Actiflo+Steel+Plant+Paper.docx》由会员分享，可在线阅读，更多相关《Actiflo+Steel+Plant+Paper.docx（9页珍藏版）》请在冰豆网上搜索。

Actiflo+Steel+Plant+Paper

TREATMENTOFSTEELPLANTEFFLUENT

WITHHIGHSPEEDMICROSANDSETTLING

CharlesD.BlumenscheinandKashiBanerjee

USFilterCorporation

NorthAmericanTechnologyCenter

Pittsburgh,PA15108

INTRODUCTION

Totalsuspendedsolids（TSS）andoilandgrease（O&G）aretwomajorpollutantsthatarepresentinthewastewatergeneratedfromthesteelmakingoperations.Thereleaseofthesesubstancesintotheenvironmentmustbecontrolledtominimizeeffectsonaquaticlifeanddownstreamuses.IncreasinglystringentenvironmentalregulationspertainingtodischargescontainingTSSandO&Gnecessitatethedevelopmentoftechnicallyandeconomicallyfeasibleprocessesfortheremovalofthesepollutantsfromindustrialwastewaterpriortodischarge.

IronoralumcoagulationfollowedbyconventionalclarificationisacommonprocessforremovalofTSSandO&Gfromindustrialwastewater.Theoverflowrateofaconventionalclarificationsystemrangesbetween0.25and1.0gallonsperminutepersquarefoot（gpm/sf）.Thisdesigncriterionoftenresultsinalargesystemfootprint.Additionally,conventionaltreatmentmethodscannothandlesuddenincreasesinhydraulicloadingthatmaybecausedbystormevents.Directdischargeofcontaminatedstormwatercanbeavoidedbybuildinglargestoragereservoirsatthefacilityandtreatingthewatergradually,orbytreatingthepeakflowcontinuously.Typically,installationofalargestoragetankiscostprohibitive.

VivendiWater/USFilterCorporationhasdevelopedacost-effectivesystem,knownasActiFlo,fortreatingwastewater.Theprocesshasanextremelysmallfootprint,typicallyrequiringlessthan10%ofthespaceneededforaconventionalsedimentationprocess.Evenatahighwastewaterflowrate,thisprocessiscapableofproducingexcellenttreatedwaterquality.Pilot-scaleoperationofthissystemwasconductedtoverifytheapplicabilityoftheActiFloprocessforefficientlyhandlingwastewaterfromasteelmakingfacility.TheprimaryobjectivesofthisstudyweretodemonstratetheeffectivenessofthisballastedcoagulationprocessfortheremovalofTSSandO&Ginacontinuous-flowsystemaswellastodeterminethedesiredoperatingconditionsoftheActiFlosystem.

PROCESSDESCRIPTION

ActiFloisacompact,conventional-typewaterclarificationsystemthatutilizesmicrosandasaseedforflocformation.Themicrosandprovidessurfaceareathatenhancesflocculationandactsasaballastorweight.Theresultingsand-ballastedflocdisplaysuniquesettlingcharacteristics,whichallowforclarifierdesignswithhighoverflowratesandshortdetentiontimes.Thesedesignsresultinsystemfootprintsthatarebetween5and20timessmallerthanconventionalclarificationsystemsofsimilarcapacity.Theuseofmicrosandalsopermitstheunittoperformwellunderdramaticallychangingflowrateswithoutimpactingfinaleffluentquality.Theoverflowratecanvaryfrom20gpm/sftoashighas60gpm/sfwithinshortperiodsoftime（lessthanone-halfhour）withoutsacrificingperformance.

RawwaterenterstheActiFlosysteminthefirstflashmixtank（coagulationtank）.Here,chemicalcoagulant（alum,ferricion,etc.）isaddedtodestabilizesuspendedsolidsandcolloidalmatterintheinfluentstream.Typicalhydraulicdetentiontimeinthecoagulationtankisaroundtwominutes.Thecoagulatedwaterthenpassesintothesecondflashmixtank（injectiontank）wherepolymericflocculantandmicrosandareaddedtoinitiateflocformation.Theseserveas“seed”forflocformationanddevelopmentinthenextprocessstep.

ActiFlotreatmentcontinuesaswaterpassesthroughtheunderflowpassagefromtheinjectiontankintothematurationtank.Inthematurationtank,relativelygentlermixingprovidesidealconditionsfortheformationofpolymerbridgesbetweenthemicrosandandthedestabilizedsuspendedsolids.Thisprocessisfurtheraugmentedbythelargespecificsurfaceareaofthemicrosand,whichprovidesenhancedopportunityforpolymerbridgingandenmeshmentofmicrosandandflocalreadyinsuspension.

Thefullyformedballastedflocsleavethematurationtankandenterthesettlingtank.Here,laminarupflowthroughthelamellarsettlingzoneprovidesrapidandeffectiveremovalofthemicrosand/sludgeflocs.ClarifiedwaterexitstheActiFlosystemviaaseriesofcollectiontroughsorweirs.

Theballastedflocsand-sludgemixtureiscollectedatthebottomofthesettlingtankandwithdrawnusingarubber-linedcentrifugalslurrypump.Thesand-sludgemixtureisthenpumpedtothehydrocycloneforseparation.Energyfrompumpingiseffectivelyconvertedtocentrifugalforceswithinthebodyofthehydrocyclone,causingthesludgetobeseparatedfromthehigherdensitymicrosand.Onceseparated,themicrosandisconcentratedanddischargedfromthebottomofthehydrocyclone,andre-injected