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Removal of metals white paper

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Innovative Resources Group
Innovative Resources Group

IRG Systems offers an improved metals removal process using tubular membrane filters (TMF) that results in more effective solids separation and high-quality effluent. TMF provides excellent heavy metals reduction through absolute filtration and fouling resistance. It requires less space than conventional methods and is more conducive to automation. The process involves equalization, chemical addition, solids separation via TMF, dewatering, and filtration. Testing of four waste streams showed the process effectively reduced metals levels to non-detectable amounts or below discharge standards.

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Innovative Resources Group MetalsRemovalProcessCharleston,SouthCarolina Removalof metalsfrom wastewater canbeaccomplishedeffectivelyby precipitatingthemetalsby various chemicalmeansandremovingtheprecipitateswithclarificationmethods.IRG Systems offers an improvedversion of the proven processby usingtubularmembranefilters(TMF).Thisresultsina moreeffective andreliablesolidsseparationprocessandprovidesexceptionaleffluentquality.Use of TMF alsoeliminatesthebulkyclarifierstypicallyusedin the processandmakesit possibleto provide the entire system as a portablecontainerizedsolution. Background Industrial processescanoftenresult in wastewater contaminatedwithheavymetals(suchas Hg, Pb, Zn, Ni, Cr, Cu, and Cd)that requiretreatmentpriorto dischargeorreuse.Basic treatmenttechnology for metalsremovalis chemicalprecipitation.Byaddingspecific chemicalreagentstothe wastestream, the chemicalsreactwithheavy metalsto form insolubleprecipitates.Theseprecipitatescanthenbe separatedfrom the water with the appropriate solid/liquidseparationprocess.Conventionalseparation equipmenttypicallyinvolves gravity separationmethods suchasan inclinedplateclarifier.Butgravity settlinghas somedisadvantagesdueto the separationprinciple:  A chemicalcoagulanthasto be fed into the wastewaterto form largersuspended particlesto enhancetheseparation process.Coagulantsbringthreeproblems: higheroperationcost,largersludge volume,and the possiblepresenceof impuritiesinthe coagulants.  Separationperformanceislesseffective dueto a lackof an absolutebarrier.  Separationperformanceisaffectedby changesinflowand temperature. Tubularmembranefilter(TMF)modulesincombinationwithchemical precipitationprovideexcellent reductionofheavy metalsdueto their absolutefiltration(0.1 micron)capabilityandtheir abilityto resist fouling. TMF productwater(referredto as filtrate) is readyfor eitherdisposalinto existing municipal waste systems or further treatment for plantreuse. Treatedeffluentlevelsof lessthan 1 ppm suspendedsolidsandless than0.1 ppm metalsare typical.  Treatedfiltrateis readyfor reuse, not just for discharge.  Removalefficiencyis excellentwithtreatmentlevels morethanadequateto meetstringent dischargestandards.  Less spaceisrequiredandsystem expansionisrelatively easy, often simplyby adding membranemodules.  Less coagulantisrequired.  TheTMF filtrationprocessis muchmoreconduciveto automationasopposedtoclarification. It canalso be started andstopped easilywithoutdegradationof treatedwater quality.
MetalsRemovalProcessCharleston,SouthCarolina 2 ProcessDescription Themetalsremovalprocessiscomprisedofthe followingsteps:equalization,chemicaladditionand reaction,solidsseparation,solidsdewatering,filtrateneutralization, andmembranecleaning.Eachis explainedinmoredetail belowandon the attachedflowdiagram.Pleasenotethis is a general descriptionaseachsystem mayvary dependinguponthenatureof the waste stream and the metalsto be removed.  Equalization-An equalizationtankis used to holdinfluentwastewater allowingfluctuationsin water chemistryandflow to equalize. Volumeof this tank dependsuponinfluentwater quantity, qualityandfluctuation.  Chemical Addition and Reaction -Severalmethodsmaybe usedfor chemicaladditionto the waste stream dependinguponthenatureof the wastestream andthe types of metalsto be removed.It maybe doneelectrolyticallyby meansofan electrocoagulationstep.Orit may be doneby injectionofthe necessarychemical IndividualTMF Module reagentsfollowedby mixing.Typically,oneor two reactiontanks are requiredafterchemicaladditionforpH adjustment,oxidation/reductionreactions(onlyfor certainmetals),coagulantfeeding,etc.  SolidsSeparation -After sufficientchemical reactiontime,thewastestream enters a recirculationtankwhich allowsthewastewaterwiththe precipitatedsolidstobe recirculated throughthe TMF modules.Therecirculation tankisnormallydesignedtohave 2 to 5 minutes of hydraulic retentiontime.Therecirculationpumpissized to provide enoughflowto maintain a sufficientvelocityin the membranemoduletubestominimizemembranefouling. Therefore the recirculationpumpcapacityismuchhigherthanactualsystem capacity.TheTMF modules are connectedinserieswithmultipletrainsofmodulescomprisingthecompletesystem.The numberof TMF modulesinseriesandthe quantity of separatetrains are determinedbywaste stream conditions,flowrate, and selected membranefluxvalue.  SolidsDewatering -Thewastestream isrecirculatedthroughtheTMF modulesuntilthe solidsconcentration reaches3%to5%. A portion of the concentratedwastestream isthen transferred to a sludgethickenerequipped withafilter pressor centrifugeto separatethe dewateredsolids.Supernatantfrom the dewateringprocessis transferred backto the recirculationtank.  EffluentNeutralization -Manymetalsremovalapplicationsrequiretheadditionofchemical reagentsthat raisethe pH of the waste stream. In those cases,the filtrate mustbe pH adjustedby addingcarbondioxideorotheracid.  MembraneCleaning -As is the casewithany membrane treatmentprocess,themembrane doesneed to be cleaned periodically.Thesystem is thereforeequippedwithanintegral membranecleaninplace(CIP)system. TheCIP system is comprisedofcleaningtanks,a cleaningpump,andrelatedpipingandvalves.
MetalsRemovalProcessCharleston,SouthCarolina 3 ProcessOperation TheTMF system hasthree operationmodes:service,backpulse,andchemicalcleaning.Asimple descriptionofeachoperationmodeisdescribedbelow.Again,pleasenote this is a generaldescription as eachsystem mayvary dependinguponthenatureof the waste stream andthe metalsto be removed. ServiceMode -Thewastestream flowsby gravity or is pumpedfrom theequalizationtank into the reaction tankswith relevant chemical dosing andnecessarypH/ORP monitoring. Gravity flow into the recirculation tankthen takes place.Thewaterwith precipitatedmetals is drawnout of the tank by the process (recirculation)pump.Themembranefiltration processseparatesthe suspended solidsfrom the liquid.Thesuspended solidsareretainedby the membranes,concentratedinthere- circulating stream,andreturnedto the recirculationtank.Filtratethat has passedthru the membranes goesto addedprocessing(suchasneutralization)ordischarge.Sludgeintherecirculationtankissent to a sludgethickenerandthen to a filter press or centrifugebypneumatic diaphragmpump. BackpulseMode -After the system runs undernormalconditionsfora set periodof time, usually5-30 minutes,the recirculationpumpisshutdownandan automatic valve on the filtrate pipingisclosed.A solenoidvalve opens,allowing7-15psiof air to pushfiltrate from the backpulsecolumn,installedon filtrate piping,into the moduletrain for approximately10seconds.Becausethetrainis flooded,the air pressureinto the pipingforcesfilteredwater throughthe membranetubesintheoppositedirectionof the normalfiltrationflow, dislodgingsuspendedsolidsthat mayhave collectedonthemembrane surface. Chemical Cleaning -After the system hasbeen runfor several days or weeks,filtrate flowrate will decreasedueto normalmembranefoulingthatis not removedby the backpulsemode.When degradationofperformancehas MultipleTMF Trainsreachedaspecifiedlimit,chemicalcleaningis executedmanuallyor automaticallyto regainpropermembrane performance.DuringCIP,chemical solutionsare circulatedthroughthemembranemodulesviathe cleaningpump. Cleaningchemicals includingsodiumhypochlorite,acids,andsodium hydroxidearetypicallyused to dissolve contaminants from the membranesurface.
MetalsRemovalProcessCharleston,SouthCarolina 4 EffectivenessofTreatmentMethod Thetablebelowlistsactualtest resultsfrom four separatewaste streams.Pleasenote that actual results willvary with eachapplication. WasteStream 1 WasteStream 2 WasteStream 3 WasteStream 4 Influent pH: 2.63 Cu: 36.6 mg/l Ni: 0.993 mg/l Cr: 0.464 mg/l Fe: 0.418 mg/l Conductivity: 2590 μs/cm pH: 8.34 Cu: 0.075 mg/l Ni: 87.1 mg/l Conductivity: 454 μs/cm pH: 2.99 Cu: 0.821 mg/l Ni: 0.18 mg/l Cr: 221.6 mg/l Fe: 1.054 mg/l Conductivity: 846 μs/cm pH: 3.16 Cu: 12.2 mg/l Ni: 81.5 mg/l Cr: 293.1 mg/l Fe: 0.692 mg/l Conductivity: 2940 μs/cm Filtratepriorto Neutralization pH: 11.07 Cu: not detected Ni: not detected Cr: not detected Fe: not detected Conductivity: 1303 μs/cm pH: 9.12 Cu: not detected Ni: 0.107 mg/l Conductivity: 512 μs/cm pH: 11.78 Cu: 0.01 mg/l Ni: not detected Cr: not detected Fe: not detected Conductivity: 2610 μs/cm pH: 9.99 Cu: not detected Ni: 0.088 mg/l Cr: 0.211 mg/l Fe: not detected Conductivity: 3770 μs/cm SystemCapacity Dueto the availableTMF modulesizes,the maximumcapacityof one individualtrainis limitedto approximately250,000gallonsperday. However, multipletrainscancompriseasinglesystem. Therefore virtuallyanysize system is possibleupwardsofseveral milliongallonsperday.
MetalsRemovalProcessCharleston,SouthCarolina 5

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Removal of metals white paper

  • 1. Innovative Resources Group MetalsRemovalProcessCharleston,SouthCarolina Removalof metalsfrom wastewater canbeaccomplishedeffectivelyby precipitatingthemetalsby various chemicalmeansandremovingtheprecipitateswithclarificationmethods.IRG Systems offers an improvedversion of the proven processby usingtubularmembranefilters(TMF).Thisresultsina moreeffective andreliablesolidsseparationprocessandprovidesexceptionaleffluentquality.Use of TMF alsoeliminatesthebulkyclarifierstypicallyusedin the processandmakesit possibleto provide the entire system as a portablecontainerizedsolution. Background Industrial processescanoftenresult in wastewater contaminatedwithheavymetals(suchas Hg, Pb, Zn, Ni, Cr, Cu, and Cd)that requiretreatmentpriorto dischargeorreuse.Basic treatmenttechnology for metalsremovalis chemicalprecipitation.Byaddingspecific chemicalreagentstothe wastestream, the chemicalsreactwithheavy metalsto form insolubleprecipitates.Theseprecipitatescanthenbe separatedfrom the water with the appropriate solid/liquidseparationprocess.Conventionalseparation equipmenttypicallyinvolves gravity separationmethods suchasan inclinedplateclarifier.Butgravity settlinghas somedisadvantagesdueto the separationprinciple:  A chemicalcoagulanthasto be fed into the wastewaterto form largersuspended particlesto enhancetheseparation process.Coagulantsbringthreeproblems: higheroperationcost,largersludge volume,and the possiblepresenceof impuritiesinthe coagulants.  Separationperformanceislesseffective dueto a lackof an absolutebarrier.  Separationperformanceisaffectedby changesinflowand temperature. Tubularmembranefilter(TMF)modulesincombinationwithchemical precipitationprovideexcellent reductionofheavy metalsdueto their absolutefiltration(0.1 micron)capabilityandtheir abilityto resist fouling. TMF productwater(referredto as filtrate) is readyfor eitherdisposalinto existing municipal waste systems or further treatment for plantreuse. Treatedeffluentlevelsof lessthan 1 ppm suspendedsolidsandless than0.1 ppm metalsare typical.  Treatedfiltrateis readyfor reuse, not just for discharge.  Removalefficiencyis excellentwithtreatmentlevels morethanadequateto meetstringent dischargestandards.  Less spaceisrequiredandsystem expansionisrelatively easy, often simplyby adding membranemodules.  Less coagulantisrequired.  TheTMF filtrationprocessis muchmoreconduciveto automationasopposedtoclarification. It canalso be started andstopped easilywithoutdegradationof treatedwater quality.
  • 2. MetalsRemovalProcessCharleston,SouthCarolina 2 ProcessDescription Themetalsremovalprocessiscomprisedofthe followingsteps:equalization,chemicaladditionand reaction,solidsseparation,solidsdewatering,filtrateneutralization, andmembranecleaning.Eachis explainedinmoredetail belowandon the attachedflowdiagram.Pleasenotethis is a general descriptionaseachsystem mayvary dependinguponthenatureof the waste stream and the metalsto be removed.  Equalization-An equalizationtankis used to holdinfluentwastewater allowingfluctuationsin water chemistryandflow to equalize. Volumeof this tank dependsuponinfluentwater quantity, qualityandfluctuation.  Chemical Addition and Reaction -Severalmethodsmaybe usedfor chemicaladditionto the waste stream dependinguponthenatureof the wastestream andthe types of metalsto be removed.It maybe doneelectrolyticallyby meansofan electrocoagulationstep.Orit may be doneby injectionofthe necessarychemical IndividualTMF Module reagentsfollowedby mixing.Typically,oneor two reactiontanks are requiredafterchemicaladditionforpH adjustment,oxidation/reductionreactions(onlyfor certainmetals),coagulantfeeding,etc.  SolidsSeparation -After sufficientchemical reactiontime,thewastestream enters a recirculationtankwhich allowsthewastewaterwiththe precipitatedsolidstobe recirculated throughthe TMF modules.Therecirculation tankisnormallydesignedtohave 2 to 5 minutes of hydraulic retentiontime.Therecirculationpumpissized to provide enoughflowto maintain a sufficientvelocityin the membranemoduletubestominimizemembranefouling. Therefore the recirculationpumpcapacityismuchhigherthanactualsystem capacity.TheTMF modules are connectedinserieswithmultipletrainsofmodulescomprisingthecompletesystem.The numberof TMF modulesinseriesandthe quantity of separatetrains are determinedbywaste stream conditions,flowrate, and selected membranefluxvalue.  SolidsDewatering -Thewastestream isrecirculatedthroughtheTMF modulesuntilthe solidsconcentration reaches3%to5%. A portion of the concentratedwastestream isthen transferred to a sludgethickenerequipped withafilter pressor centrifugeto separatethe dewateredsolids.Supernatantfrom the dewateringprocessis transferred backto the recirculationtank.  EffluentNeutralization -Manymetalsremovalapplicationsrequiretheadditionofchemical reagentsthat raisethe pH of the waste stream. In those cases,the filtrate mustbe pH adjustedby addingcarbondioxideorotheracid.  MembraneCleaning -As is the casewithany membrane treatmentprocess,themembrane doesneed to be cleaned periodically.Thesystem is thereforeequippedwithanintegral membranecleaninplace(CIP)system. TheCIP system is comprisedofcleaningtanks,a cleaningpump,andrelatedpipingandvalves.
  • 3. MetalsRemovalProcessCharleston,SouthCarolina 3 ProcessOperation TheTMF system hasthree operationmodes:service,backpulse,andchemicalcleaning.Asimple descriptionofeachoperationmodeisdescribedbelow.Again,pleasenote this is a generaldescription as eachsystem mayvary dependinguponthenatureof the waste stream andthe metalsto be removed. ServiceMode -Thewastestream flowsby gravity or is pumpedfrom theequalizationtank into the reaction tankswith relevant chemical dosing andnecessarypH/ORP monitoring. Gravity flow into the recirculation tankthen takes place.Thewaterwith precipitatedmetals is drawnout of the tank by the process (recirculation)pump.Themembranefiltration processseparatesthe suspended solidsfrom the liquid.Thesuspended solidsareretainedby the membranes,concentratedinthere- circulating stream,andreturnedto the recirculationtank.Filtratethat has passedthru the membranes goesto addedprocessing(suchasneutralization)ordischarge.Sludgeintherecirculationtankissent to a sludgethickenerandthen to a filter press or centrifugebypneumatic diaphragmpump. BackpulseMode -After the system runs undernormalconditionsfora set periodof time, usually5-30 minutes,the recirculationpumpisshutdownandan automatic valve on the filtrate pipingisclosed.A solenoidvalve opens,allowing7-15psiof air to pushfiltrate from the backpulsecolumn,installedon filtrate piping,into the moduletrain for approximately10seconds.Becausethetrainis flooded,the air pressureinto the pipingforcesfilteredwater throughthe membranetubesintheoppositedirectionof the normalfiltrationflow, dislodgingsuspendedsolidsthat mayhave collectedonthemembrane surface. Chemical Cleaning -After the system hasbeen runfor several days or weeks,filtrate flowrate will decreasedueto normalmembranefoulingthatis not removedby the backpulsemode.When degradationofperformancehas MultipleTMF Trainsreachedaspecifiedlimit,chemicalcleaningis executedmanuallyor automaticallyto regainpropermembrane performance.DuringCIP,chemical solutionsare circulatedthroughthemembranemodulesviathe cleaningpump. Cleaningchemicals includingsodiumhypochlorite,acids,andsodium hydroxidearetypicallyused to dissolve contaminants from the membranesurface.
  • 4. MetalsRemovalProcessCharleston,SouthCarolina 4 EffectivenessofTreatmentMethod Thetablebelowlistsactualtest resultsfrom four separatewaste streams.Pleasenote that actual results willvary with eachapplication. WasteStream 1 WasteStream 2 WasteStream 3 WasteStream 4 Influent pH: 2.63 Cu: 36.6 mg/l Ni: 0.993 mg/l Cr: 0.464 mg/l Fe: 0.418 mg/l Conductivity: 2590 μs/cm pH: 8.34 Cu: 0.075 mg/l Ni: 87.1 mg/l Conductivity: 454 μs/cm pH: 2.99 Cu: 0.821 mg/l Ni: 0.18 mg/l Cr: 221.6 mg/l Fe: 1.054 mg/l Conductivity: 846 μs/cm pH: 3.16 Cu: 12.2 mg/l Ni: 81.5 mg/l Cr: 293.1 mg/l Fe: 0.692 mg/l Conductivity: 2940 μs/cm Filtratepriorto Neutralization pH: 11.07 Cu: not detected Ni: not detected Cr: not detected Fe: not detected Conductivity: 1303 μs/cm pH: 9.12 Cu: not detected Ni: 0.107 mg/l Conductivity: 512 μs/cm pH: 11.78 Cu: 0.01 mg/l Ni: not detected Cr: not detected Fe: not detected Conductivity: 2610 μs/cm pH: 9.99 Cu: not detected Ni: 0.088 mg/l Cr: 0.211 mg/l Fe: not detected Conductivity: 3770 μs/cm SystemCapacity Dueto the availableTMF modulesizes,the maximumcapacityof one individualtrainis limitedto approximately250,000gallonsperday. However, multipletrainscancompriseasinglesystem. Therefore virtuallyanysize system is possibleupwardsofseveral milliongallonsperday.