Iron and Manganese Removal Processes - hydratechnm.org

1 iron and Manganese Removal ProcessesPresentation Agenda Arsenic Background: chemistry and treatment options Treatment selection considerations Treatment options iron Removal Case studies ConclusionsArsenic Chemistry Arsenic has two primary valence states: Arsenic Occurrence by valence state Surface waters- predominately As (V) Ground waters usually found as As (III), however, concentrations of As (V) or a combination of As (III) and As (V) can be foundAs (III)As +3 ArseniteAs (V)As +5 Arsenate iron -based Arsenic Removal Processes Adsorptive properties of iron mineral toward arsenic are well known That knowledge is the basis for many arsenic treatment Processes Coagulation with iron coagulant iron -based adsorption media iron Removal processesArsenic Removal by IronAs(III) vs As(V)As(III) is removed during iron Removal and other iron -based Processes , but just not as well as As(V)As (III) OxidationAs (III) OxidationEffective!

2 ZFree ChlorinezPotassium PermanganatezOzonezSolid Oxidizing Media (MnO2solids)IneffectivezChloraminezChlor ine Dioxide zUV Radiation + SulfidezOxygenArsenic Treatment Issues Treatment complexity/cost Pre- and Post-treatment needs Residuals Disposal Issues Ion exchange & RO produce liquid wastes Adsorbent media produce wasted solids Coagulation/filtration and iron Removal Processes produce solids Filter backwash waste Sediment in contactor (pass TCLP test)Arsenic Treatment Simplified Process Selection GuideIron - - ug/L05101520253035404550As MCLFe - SMCLAIron Removal Process(Optimized for Maximium As Removal )BModified iron Removal ProcessCMedia AdsorptionIron Coag/FiltIon ExchangeIron Removal (M)RO / NF20 - 1 Fe/As ratioor aboveRemoval of 1 mg/Lof iron achievesremoval of 50 ug/Larsenic(0ptimized conditions and As[V])Arsenic Removal by iron Removal ProcessesArsenic Removal During iron Removal ConsiderationsIron in water (>20/1 Fe/As ratio)?

3 Form of arsenic, III or V? Oxidation: Type of oxidant: oxygen, chlorine, Point of application? Contact time? iron and As oxidation Arsenic adsorption How can arsenic Removal be predicted? Ways to improve arsenic Removal during iron Removal ? iron (and Mn) RemovalBasicsFiltrationparticle removalOxidationContact BasinAerationCl2,KMnO4, otherOxidation, Particle Development15 30 minutesFe(OH)3 (S)MnO2 (S)Fe IIMn IIFe IIIMn IVIron and Arsenic(and Mn) RemovalAerationCl2,KMnO4,otherFe IIAs IIIO xidationFe IIIAs VNote: Aeration will not oxidize As III to As VIron and Arsenic(and Mn) RemovalContact BasinOxidation, particle developmentFe(III)/As particles+arsenicIron and Arsenic (and Mn) RemovalFiltrationFe III/ As Particle RemovalOxidant Selection Depends on As, Fe (and Mn) Aeration Will not oxidize Mn II and As III (-) May need contact basin (-) iron particles have less surface area (-) Longer filter run lengths (+) Strong oxidants (chlorine, permanganate, etc) Address Mn and As oxidation (+) More particle surface area (+) Probably no contactor needed (+) Difficult to feed (-) Shorter filter run lengths (-)

4 Assessment ToolJar TestOxidationOxidation--Point of ApplicationPoint of ApplicationCase Study Case Study --MichiganMichiganParameterConcentration Arsenic ug/L19 - 24As III95 %As V5 %Calcium mg/L74 - 84 Magnesium mg/L30 - 33 iron - mg/L50 - 60 Silica mg/L12 - 13pH - - of ApplicationPoint of ApplicationCase Study Case Study --MichiganMichigan20 min CTWellsWellsAeration towerAeration towerPressure filtersPressure filtersCl250 % removalAs = 19-24 ug/LFe = mg/LOxidation- Point of ApplicationCase Study - Michigan20 min CTWellsAeration towerPressure filtersCl250 % removalAs = 19-24 ug/LFe = mg/LOxidation- Point of ApplicationCase Study - Michigan20 min CTWellsAeration towerPressure filtersCl275 % removalAs = 19-24 ug/LFe = mg/LOxidant Selection Depends on As, Fe (and Mn) Aeration Will not oxidize Mn II and As III (-) May need contact basin (-) iron particles have less surface area (-) Longer filter run lengths (+) Strong oxidants (chlorine, permanganate, etc) Address Mn and As oxidation (+) More particle surface area (+) Probably no contactor needed (+) Difficult to feed (-) Shorter filter run lengths (-)The Effect of Oxidant on Visual Properties of iron , PtCo units050100150200250300PO2= atm PO2=s atur at ed atm PO2+5 mg Cl2/LClO2 (2 mg/L)Fe[III] Linear reg ressionThe effect of oxidant type on colorFetot= 5 mg/L, DIC= 5 mg C/L, atm O2, effect of oxidant type on the color of iron particles collected from filter ModificationsIncreasing As RemovalIncreasing As RemovalUtility with iron Removal in place or willbe in place but can not meet MCL.

5 Change point of oxidant addition Increase iron concentration Adjust pH Replace media w/ As adsorption mediaClimax, MN iron Removal SystemClimax, MN iron Removal ProcessDate - 2004/2005 Aug Sep Oct Nov Dec Jan Feb Mar Arsenic concentration - ug/L0510152025303540455055 iron concentration - Raw Water ArsenicTreated Water Arsenic Raw Water iron mg/L Fe addedClimax, MN iron Removal SystemThe Effect of Initial Arsenic(V) Concentration on the Capacity of iron to Remove Arsenic(Fe(II)init=1 mg/L, DIC=10 mg C/L, pH=8, 24oC)Initial As, g/L 050100150200250 g As/mg Fe0204060801001201401601802001 mg Fe/L reduces 150 ug As/L by 115 ug As/L to 35 ug As/L1 mg Fe/L reduces 35 ug As/L by 23 ug As/L to 12 ug As/LThe Effect of pH, iron and Free Chlorine on Arsenic Removal 1 mg Fe/L, 100 mg As(V)/L, 5 mg C/L DIC, PO2= atm, 24 removed, %020406080100No chlorine1 mg Cl2/LRegressionFe(III), no chlorineEffect of Water Quality1 mg Fe/L, 100 ug As(V)/L, 5 mg C/L DIC, pH=8, 24 OCPhosphate, Arsenic Removal0204060801001 mg/L Chlorine0 mg/L ChlorineLidgerwood, NDTwo Wells: 100 feet deep As Raw 135 150 ug/L (mostly As III) As Finished 35 ug/L Fe Raw mg/L (9/11:1) Superfund site arsenic for grasshopper controlLidgerwood, NDExisting Treatment: Pre-chlorination Aeration Oxidation KMnO4 Filtration Aid polymer Filtration Antrasand (2 gpm/ft2) Post chlorination and fluoridationLidgerwood, NDMixing TankDetention TankAeration TowerWell 1 Well 2 FiltersClearwellBackwash tankSludge TankKMn04 Filter AidChlorineChlorineLidgerwood, NDEPA Demonstration Project.

6 Turbidmeters Additional polymer feed FeCl3 Coagulation (~1 mg/L) As Finished 7-8 ug/L Cost - $55,740 Lidgerwood, NDMixing TankDetention TankAeration TowerWell 1 Well 2 FiltersClearwellBackwash tankSludge TankKMn04 Filter Aid (2)Ferric chlorideChlorineChlorineSabin, MNTwo Wells: As Raw 45 ug/L As Finished 40 ug/L (20-25 ug/LPlant is falling apart!!Sabin, MNExisting Treatment: Chlorination Aeration Sand filtration FluoridationSabin, MNMajor Capital Improvement: Population 400 $1,200,000 Total cost $800,000 low interest loan $160,000 grant EPA Demonstration ProjectConclusions iron Removal = arsenic Removal Arsenic speciation is important Oxidant type is important Point of oxidant application is important Arsenic Removal impacted Plant operation impactedThank-youQUESTIONS TO DARREN LYTLE EPA/ORD)