Fundamentals of Electrodeionization (EDI) Technology

? Applied Water Solutions – reproduction prohibitedFundamentals of Electrodeionization (EDI) Technology By Chris GallagherApplied Water Solutions, Inc.WQA 2008? Applied Water Solutions – reproduction prohibitedElectrodeionization Process• EDI is not a filter but an electrochemical process that removes ionized and ionizable species• EDI can replace mixed bed ion exchange• EDI performance is directly effected by:– Total ionic load in the feed water– Temperature– Needs a DC voltage source to create an electric current– Flow rate• Current Efficiency governs all EDIs? Applied Water Solutions – reproduction prohibitedYear 0 1 2 3 4 5 6 7 8 9 10MaintenanceEvaluation IssuesConsiderations/RecommendationsFilter replacement every 6 monthsCleaning frequency increases through timeReplace CarbonPump SealsCalibrationMembraneReplacementReplace Motor Replace PumpUpdate InstrumentsReplace ValvesDecrease in ThroughputVariability in Feed SourceStricter Water StandardsNew regulations prohibiting certain dischargeIncrease Demand for High Purity WaterRevise PM program Revise PM programMembrane ReplacementNew System InvestmentRebuild Existing SystemReevaluate technologiesReduce Chemical UseEnvironmental IssuesMaintenance CostsReliabilityInitial CapitalInvestmentLife of a Water System? Applied Water Solutions – reproduction prohibitedType of EDIsThick Cell• Introduced in 2001• Plate and frame Spiral Wound• Limited market share • Higher efficiencyCircular Enclosure• Innovative design• Plate and frame Thin Cell• Introduced in late 80s• Plate and frame• First sold to OEMsCourtesy: ElectropureCourtesy: Ionpure TechnologiesCourtesy: OmexellCourtesy: Ionpure TechnologiesThick Cell• Introduced in 1996• First thick cell sold to OEMs• Plate and frame Courtesy: GE Water? Applied Water Solutions – reproduction prohibitedProcess PrinciplesANODE (+)CATHODE (-)EXCHANGE MEMBRANE EXCHANGE MEMBRANE PurifyingConcentratePurifyingConcentrateConcentratePurifyingPurifyingCl-HCO3-OH-CO3-HCO3-Ca++Mg++Na+H+Cl-CO3-HCO3-Mg++Na+H+ElectrodeElectrodeCa++HCO3-HCO3-HCO3-Ca++OH-OH-Ca++Na+H+OH-? Applied Water Solutions – reproduction prohibitedFlow Path of EDIsANODE (+)CATHODE (-)Conc Purifying ConcEDEDI Dilute FilledEDI All FilledANODE (+)CATHODE (-)Conc Purifying ConcANODE (+)CATHODE (-)Conc Purifying Conc? Applied Water Solutions – reproduction prohibitedSpiral Wound EDI – Design #1Courtesy: Dow Chemical? Applied Water Solutions – reproduction prohibitedSpiral Wound EDI – Design #1Courtesy: Dow Chemical? Applied Water Solutions – reproduction prohibitedSpiral Wound – Design #2Courtesy: Christwater? Applied Water Solutions – reproduction prohibitedEDI System DesignMultiple Stack vs. Single Stack• 50 gpm standard• 15 gpm standard• 10 gpm standard• <10 gpm standardCourtesy: GE Infrastructure, Water & Process Technologies? Applied Water Solutions – reproduction prohibitedEDI System Design• Multiple Stack vs. Single StackCourtesy: Ionpure Technologies? Applied Water Solutions – reproduction prohibitedFeed Water Requirements for EDI Supplier 1 Supplier 2 Supplier 3 Supplier 4Source: RO water RO water RO water RO waterFeed Conductivity:< 40 µS/cm 4-30 µS/cm < 40 µS/cm naConcentrate Conductivity:> 20 µS/cm(varies)> 10 µS/cm(varies)na 250 - 1000 µS/cmHardness: < 0.25 ppm as CaCO3< 1.0 ppm < 1.0 ppm < 2.0 ppmSilica: < 1.0 ppm < 0.5 ppm < 1.0 ppm < 1.0 ppmTOC: < 0.5 ppm < 0.5 ppm < 0.5 ppm < 0.5 ppmPressure: 20 to 50 psi < 60 psi 20 to 100 psi 36 to 100 psiTemperature: 10 to 35oC 5 to 35oC 5 to 45oC 5 to 38oCpH: 4 to 10 5 to 9.5 4 to 11 5 to 9Chlorine: < 0.1 ppm < 0.05 ppm < 0.02 ppm < 0.05 ppmFe, Mn, Sulfide: < 0.01 ppm < 0.01 ppm < 0.01 ppm < 0.01 ppmCO2 < 10 ppm < 5 ppm na < 10 ppm? Applied Water Solutions – reproduction prohibitedFeed Water Concentration LimitsParameter RO EDRTDS (as NaCl) rejection rates 97-99% removal ~50% removalIron (dissolved) 0.3 mg/l 0.3 mg/lManganese (dissolved) 0.05 mg/l 0.1 mg/lH2S 0.1 mg/l 0.1 mg/lAluminum 0.1 mg/l 0.1 mg/lFree Chlorine ( RO Composite Polyamide Membranes)Homogeneous Ion Exchange Membranes < 0.1 mg/l 0.5 mg/l cont30.0 mg/l max shockFree Chlorine (Max, Cellulose Acetate Blend Membranes) 1.0 mg/l NAOil 0.0 mg/l 2.0 mg/lCOD 4 – 18 mg/l (as O2) 50 mg/l (as O2)TOC < 2.0 mg/l 15.0 mg/lTurbidity 0.1 – 0.4 NTU 0.5 – 2.0 NTUSDI15 (Continuous) < 3.0 10-12SDI15 (Max, Intermittent) 4.0 – 5.0 15? Applied Water Solutions – reproduction prohibitedTypical GuidelinesWater Standards / Guidelines Microelectronics Power ASTM Pharmaceutical electronics grade QR 1.2 Type I Type II USP27 Conductivity (?S/cm) .0546 <0.10 <0.056 <1.0 <1.3 Resistivity (M?-cm) 18.2 >10.0 18.0 >1.0 >0.769 TOC (ppb) <50 100 50 <500 Silica (ppb) <5 <10 <3 <3 none Bacteria (cfu/ml) <10 none <100 Chloride (ppb) <0.1 <10 1 5 none Sulfate (ppb) 0.1 <10 none Sodium (ppb) <0.5 <10 1 5 none ? Applied Water Solutions – reproduction prohibitedConcentrate Compartment• Recirculation– Concentration of reject– Flow rate considerations• Brine Injection– Addition of NaClPurifying Conc100 gpm90 gpmPurifying ConcRejectPurifying ConcRejectReject5-10 gpm? Applied Water Solutions – reproduction prohibitedHydraulic/ Pressure Considerations• Reverse Osmosis Design– RO Pump Sizing– Permeate Back Pressure• Break Tanks– Pre EDI– Post EDI• EDI– Pressure drop across EDI varies with manufacturer – EDI back pressure varies with manufacturer? Applied Water Solutions – reproduction prohibitedSystem DesignROEDISTORAGEROEDISTORAGEROSTORAGEHigh PressurePumpHigh PressurePumpEDI FeedPump? Applied Water Solutions – reproduction prohibitedSystem DesignROEDISTORAGEROSTORAGEBoosterPumpROEDISTORAGERAWWATEREDI RejectHigh PressurePumpHigh PressurePumpEDI FeedPump? Applied Water Solutions – reproduction prohibitedCurrent Efficiency• Current Efficiency governs all EDIs• Voltage is only a potential• Current does the workOhm’s LawE=IR? Applied Water Solutions – reproduction prohibitedCurrent Efficiency• Detailed Equation (1)Where? ? current utilization efficiency, %z = charge of ionF = Faraday’s constant, 96,485 Amp-s/molQf = diluate flow rate, L/s (=gpm/15.85)Cdinlet = diluate ED cell inlet ion concentration, mol/LCdoutlet = diluate ED cell outlet ion concentration, mol/LN = number of cell pairsI = applied current, AmpsSource: Ionpure? Applied Water Solutions – reproduction prohibitedCurrent Efficiency• Simplified EquationSource: Ionpure? Applied Water Solutions – reproduction prohibitedVariables to be Monitored• Pressure• Temperature• Flow rates– Dilute– Concentrate– Electrode• Voltage• Amperage• Conductivity• Resistivity? Applied Water Solutions – reproduction prohibitedPerformance Data Collection• Daily• Weekly• Monthly• Seasonal EffectsRO Conductivity(EDI Feed)TemperatureEDIROEDI Conductivity(Quality)? Applied Water Solutions – reproduction prohibited• Some conditions that effect system performance:– Water temperature– Feed salinity• Normalization adjusts data to fit specific operating conditions.• Changes in normalized performance represent a real change in system performance.• Normalization makes it easy to see real changes in the performance of a system.Normalization? Applied Water Solutions – reproduction prohibitedSeasonal Effects• Geography• Naturally occurring events• Feed water source variability– Chlorine– Chloramines– Hardness– pH– Temperature? Applied Water Solutions – reproduction prohibitedTroubleshootingPretreatmentOrganicFoulingParticulateFoulingBiofoulingOxidationAttackScalingSymptoms•Decrease in performance•Increase in electrical resistanceMost notable in the diluting compartment•Decrease in flow•Increase in pressure drop•Decrease in performanceMost notable in the diluting compartment•Decrease in flow•Increase in pressure drop•Decrease in performanceMost notable outside of active membrane area•Decrease in flow•Increase in pressure drop•Decrease in performance•Increase in electrical resistanceAn oxidation attack will irreversibly damage EDI•Decrease in flow•Increase in pressure drop•Decrease in performanceMost notable in the concentrate department? Applied Water Solutions – reproduction prohibitedOrganic FoulingCurrent at Constant VoltageTimeEDIEDI Product Resistivity? Applied Water Solutions – reproduction prohibitedScaling?P in Concentrateand ElectrodeTimePressureCurrentCurrent? Applied Water Solutions – reproduction prohibitedOxidation?P in DiluteTimePressureCurrentCurrent? Applied Water Solutions – reproduction prohibitedThree Important Factors of CE• Flow Rate– Higher flow rates, less residence time– Kinetics change– Pressure drop• Feed Water– Total ionic load– Temperature• Current– Voltage– Directly affects performanceCASE E (Volts) I (Amps) R (Ohms) Quality (Meg-ohm)Initial Condition300 3#1 300 2 ?#2 400 3 ?#3 200 3 ?#4 400 4 No Change15?No ChangeNo Change?? Applied Water Solutions – reproduction prohibited“Bringing Clarity to the Turbid Waters of Technology”SMby Chris Gallaghercgallagher@appliedwatersolutions.comQuestions?DisclaimerThe speaker represented the information included in this presentation as being valid at the time it was presented. Applied Water Solutions makes every effort to provide timely and accurate information. Nevertheless, mistakes and confusions may occur. Applied Water Solutions and the author does not assume liability for the accuracy or reliability of the information provided in here.