Multiphase Extraction for Soil and Groundwater Remedation.ppt

multiphaseextractionforsoilandgroundwaterremediation nickswigerspring2007 introduction contaminantreleases whenacontaminantisreleasedintotheenvironment itwillpartitionintofourphases bulkliquidifinsoluble lnaplordnapl adsorbtosoilparticlesvaporphaseinsoilgasdissolveintosoilmoisturetoeffectivelyremediatetheenvironmentfromachemicalspill allphaseswillneedtoberecovered typesofremediationsystemshavegreatlyevolvedinlast20yearsaseveryoneisalwayslookingforamoreeffectiveandefficientprocess multiphaseextractionisarelatively new enhancementtosoilvaporextraction whatismultiphaseextraction extractionsofmultiplephasesoffluidsfromthesubsurface fairlyrecentenhancementfortheincreasedrecoveryandefficiency inrightsubsurfaceconditions ofsoilvaporextractions twotypes dualphaseextraction notfocusedoninpaper presentation extractionofmultiplephasesoffluidsutilizingseparatepumpsandconduits forexample installingasubmersiblepumpinawelltolowertheelevationofthegroundwatertoenhanceanexistingsoilvaporextractionsystem multiphaseextractionextractionofmultiplephasesoffluidsutilizingonepumpandoneconduit typicalschematicofmultiphaseextraction multiphaseextractionvs soilvaporextraction bothvaporandhydraulicconductivityareafunctionofmoisturecontentinthevadosezone vaporconductivitydecreaseswithincreasingmoisturecontent withmanychemicalreleases theywillmigrateverticallyuntilalowerpermeabilityunitisreachedorthesurfaceofthesaturatedsoilisreached capillaryfringeabovethegroundwater chemicalswithalowerdensitythanwater lnapl withstopatthesaturatedsoil chemicalswithahigherdensitythanwater dnapl withstopatalowerpermeabilityunitorforcebalance i e capillary hydrostatic etc multiphaseextractionvs soilvaporextractioncont inbothcases theareastypicallywiththemajorityofthecontaminantshaveahighmoisturecontent thedecreasedvaporconductivityintheareaswiththemajorityofthecontaminantsmakessoilvaporextractionlessefficient theincreasedmoisturecontentalsolimitsthemasstransferofcontaminantsfromtheliquidphasetovaporphase multiphaseextractionvs soilvaporextractioncont themasstransferlimitedsystemsarelessefficientthanflowlimitedsystems masstransferinhighmoisturecontentdominatedbyhenry slawkh cv cl conc vapor conc liquid exponentialdecreasevs lineardecrease multiphaseextractionvs soilvaporextractioncont bytheremovalofmultiplephasesoffluidsitforcessystemstobeflowlimited time monthlymassremoved typicalusesofmultiphaseextraction aswithsoilvaporextraction thevolatilecompoundsthattendnottoadheretothesoilareamenabletomultiphaseextraction thefollowingchemicalpropertiesaretypicallyusedforindicators relativelylowdistributioncoefficient ratioofconcentrationinsoiltoconcentrationinliquid kd cs clrelativelyhighvaporpressure pressureexertedbyvaporinequilibriumwithbulkfluid indicativeofthecompoundsvolatilityortendencytoexistingaseousphase multiphaseextractionismostefficientinporousmediawithmoderatepermeability allowsremovalofbothphaseswiththegreatestremedialinfluence highlypermeablemedia thedominantphaseremovedwillbewaterandtherewillbelessinfluenceonthesoilgas neartheaquifer mostlygroundwaterremovedwithverylittlesoilgas lowpermeablemedia thedominantphaseremovedwillbegas butthewaterwillhavemuchlessinfluence nearaquifer therewillbemuchdrawdown withlittleinfluenceonthevadosezone contaminantremovalwithmultiphaseextraction phaseremovalcanbeaccomplishedbytwomechanisms overcominghydrostaticpressure staticlift entrainingtheliquidsinthevapordependantonvaporvelocity contaminantremovalwithmultiphaseextraction forthestaticlift hydrostaticpressure thevacuumappliedmustbeabletoliftthemostdensephasefluid waterwithanlnaplspillandcontaminantwithadnaplspill tothesurfaceandovercomemajorandminorlosses p gh h heightoflift headloss contaminantremovalwithmultiphaseextraction fortheliquidtoberemovedviavaporentrainment thevaporvelocityforces drag fd andvaporsurfaceforces fv mustovercomegravityforces fg fg fd fvfg w v g mgfd 0 5 cd a v2 afv a a v2 contaminantremovalwithmultiphaseextraction threedifferentschemesofmultiphaseflowinwell basedonvelocityofthevapor multiphaseextractionoperations twoextractionconfigurationsaretypicallyutilizedandarebasedonthelocationoftheappliedvacuum vacuumcanbeapplieddowninthewellwiththeuseofa stinger or drop tube vacuumcanbeappliedtothetopofthewell multiphaseextractionoperations the stinger tubeconfigurationwouldbemostapplicableverynearoratthewatertable thevacuumconfigurationwouldbemoreapplicablethehighmoisturecontentsoilinthevadosezone multiphaseextractionoperations thefluidremovalisprovidedbyafan compressorblower orpumpdependingonthesubsurfaceconditions i e flowrateneeded vacuumneeded etc withallfans blowers andcompressorsthefluidstreammustberoutedthroughatank commonlycalledaknockouttank astheyarenotdesignedforliquidmovement liquidringpumpsdonotneedtohaveaknockouttank designedformultiplephasefluids multiphaseextractionoperations allphasesoffluidswillhavetobetreatedpriortodischarge forthemostpart dependingonregulations however withnonaqueousphasecontaminants therewillbeminimaltreatmentofwaterasthevaporactsasinsituairstripping multiplewaystotreatthefluidssuchaschemical i e oxidationwithozoneorperoxide physical i e carbonadsorption andbiological i e bioreactors determiningtreatmentarea eachextractionpointwillhaveaset areaofinfluence or radiusofinfluence ifradialflowisassumed darcy slawcanbeusedinboththesaturatedandunsaturatedmediatoapproximateradiusofinfluence capture integrated steadystatedarcy slawforunconfinedaquifers q k2 ho2 hw2 ln ri rw where ho originalwaterelevationhw waterelevationinextractionwellri radiusofinfluencerw radiusofextractionwell determiningtreatmentarea forthevadosezone thedarcy sflux relatedtopressurechanges insteadofhead is q k dp dx usingtheaboveandflowequationsforradialflowtowells jeffkuoinpracticaldesigncalculationsforsoilandgroundwaterremediationpresentedthefollowing uw k 2 pw rw ln rw ri 1 pri pw 2 where uw vaporfluxattheextractionwellpw pressureattheextractionwellpri pressureattheradiusofinfluencerw radiusoftheextractionwellri radiusofinfluenceur k 2 pw r ln rw ri 1 pri pw 2 1 1 pri pw 2 ln r rw ln rw rri 0 5 where ur vaporvelocityatrr radialdistancer determiningtreatmentarea thetwoequationscanbeutilizedtofindthecaptureareainthevadosezoneandvaporvelocityatcertainradialpointswithinthevadosezone maysoilandgroundwaterremediationengineersutilizeonlythe radiusofinfluence asthesoilgascapture thisprovidestheextentofcapture butnotnecessarilytheextentofremediation summary multiphaseextractionisaenhancementthatcanbemadetosoilvaporextractionsystemtoincreaseeffi