Technologies and Costs for Removal of Arsenic From Drinking Water

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ends up as ferric hydroxide. In alum coagulation, however, a significant portion of the addedaluminum remains as soluble complexes. Because only particulate metal hydroxides can mediatearsenic removal, alum plants must carefully consider aluminum solubility when arsenic removal isrequired. Aluminum complexes can pass through filters and decrease overall arsenic removal.Effect of Coagulant DosageIn general, higher removal efficiencies can be achieved with increased coagulant dosages(Cheng, et al., 1994; Edwards, 1994; Gulledge and O’Conner, 1973). Hering et al. (1996)demonstrated in coagulation experiments with ferric chloride at pH 7.0 that both As(III) and As(V)removal were dependent on coagulant dosage. “Complete” removal of As(V) was observed forcoagulant dosages above 5 mg/L ferric chloride. “Complete” removal of As(III) was not observedunder the range of conditions examined.Predictions based on existing data and the use of a diffuse-layer model indicated that As(III)removals by coagulation were primarily controlled by coagulant dosage, whereas the converse wastrue for As(V) (Edwards, 1994). A database compiled by Edwards (1994) containing muchpreviously published work on arsenic coagulation indicated that, at all dosages greater than 20 mg/Las ferric chloride or 40 mg/L as alum, greater than 90 percent removal of As(V) was always achieved.At lower coagulant dosages there was considerable scatter in the data attributed to poor particleremoval, high initial As(V) concentrations, and possible interferences from other anions in thedifferent waters tested.Effect of Coagulation pHSorg and Logsdon (1978) demonstrated that arsenic removal with alum coagulation is mosteffective at pH 5 to 7, and ferric coagulation is most effective at pH 5 to 8. As discussed earlier,Edwards (1994) summarized that at significant coagulant dosages As(V) removal was similar for bothalum and ferric coagulants at pH 7.6 or lower. At pH values greater than 7.6, however, the averageremovals were 87 percent for 10 mg/L ferric chloride and only 67 percent for 20 mg/L alum.Analyzing previously collected research data for As(III) removal by iron and aluminumcoagulation, Edwards (1994) demonstrated that removal of As (III) is much higher during ironcoagulation when compared with that of alum. Furthermore, As(III) removal by adsorption ontoaluminum hydroxides decreases markedly above pH 8.0.2-3
Page 1: United StatesEnvironmental Protecti
Page 5: ACKNOWLEDGMENTSThis document was pr
Page 8 and 9: 2.5.7 Reverse Osmosis .............
Page 10 and 11: 5.0 POINT-OF-ENTRY/POINT-OF-USE TRE
Page 12 and 13: LIST OF FIGURES2-1 Pressure Driven
Page 14 and 15: LIST OF ACRONYMSAAAWWAAWWARFBLSBVC/
Page 16 and 17: POUpoint-of-useppbparts per billion
Page 18 and 19: # Alternative treatment processes s
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Page 24 and 25: Hering et al. (1996) observed the o
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Page 28 and 29: This analysis suggests that sulfate
Page 30 and 31: Note that post-treatment pH adjustm
Page 32 and 33: A survey of full-scale plants by Mc
Page 34 and 35: Arsenic in the pentavalent arsenate
Page 36 and 37: Effect of Competing IonsLike ion ex
Page 38 and 39: treated flow of 13,730 gpd. In fact
Page 40 and 41: 2.4 ION EXCHANGE2.4.1 IntroductionI
Page 42 and 43: 2.4.4 Resin TypeAs stated earlier,
Page 44 and 45: “counter-current flow” method a
Page 46 and 47: 2.4.10 EBCTA few studies have been
Page 48 and 49: oader range of constituents than lo
Page 50 and 51: TABLE 2-4Typical Recovery for Membr
Page 52 and 53: TABLE 2-5As(V) and As(III) Removal
Page 54 and 55: surface water treatment is typicall
Page 56 and 57: the remainder of the 80-day period.
Page 58 and 59: TABLE 2-9Summary of Arsenic Removal
Page 60 and 61: TABLE 2-11Arsenic Removal with RO a
Page 62 and 63: communities (New Mexico State Unive
Page 64 and 65: appear to present some competition
Page 66 and 67: Table 2-14Adsorption Tests on GFHUn
Page 68 and 69: 2.6.5 Photo-OxidationResearchers at
Page 70 and 71: All three models rely on flows to c
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Table 3-2VSS Capital Cost Breakdown
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Table 3-5W/W Cost Model Capital Cos
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3.2.3.2 Water Model1. The Water mod
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TABLE 3-9Chemical CostsChemical Cos
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3.2.6 Flows Used in the Development
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of California Water Agencies indica
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two technologies. Redundancy for th
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3.4.2 Use of Blending in Cost Estim
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3.5.2 ChlorinationAs previously sta
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Figure 3-2Pre-oxidation - 1.5 mg/L
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Small Systems (Less than 1 mgd)The
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Figure 3-3Enhanced Coagulation/Filt
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3.6.3 Direct FiltrationDirect filtr
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Figure 3-5Coagulation Assisted Micr
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3.6.5 Lime SofteningLime softening
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Figure 3-7Enhanced Lime SofteningCa
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3.7 ADSORPTION PROCESSES3.7.1 Activ
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11. The capital costs estimated in
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Adjustment in staffing or shifting
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Figure 3-10Activated Alumina (pH 7
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Figure 3-12Activated Alumina (pH Ad
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The costs in both the April 1999 Te
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For design flows greater than 1 mgd
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Figure 3-16Anion Exchange (< 20 mg/
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Figure 3-18Anion Exchange (20-50 mg
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3.9 SEPARATION PROCESSES3.9.1 Micro
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emovals are needed the ratio needs
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Figure 3-21Greensand FiltrationO&M
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This page was intentionally left bl
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4.l.2 Methods for Estimating Residu
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The use of evaporation ponds and dr
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EPA has established water quality c
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equates to a total (municipal and i
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Landfill disposal requires that res
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ackwash streams to a sanitary sewer
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handling by other mechanical or non
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of these sludges, however, are gene
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following dewatering, the dry sludg
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Selection of Handling and Disposal
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4.5 RESIDUALS HANDLING AND DISPOSAL
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Figure 4-2Anion Exchange (< 20 mg/L
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Figure 4-4Anion Exchange (20-50 mg/
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Figure 4-10Activated Alumina (pH 8
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Figure 4-14Greensand FiltrationWast
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water characteristics must be consi
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TABLE 5-1Source Water Summary - Poi
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solids (1,500 mg/L). San Ysidro is
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Figure 5-1POU Reverse OsmosisTotal
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5.5 ION EXCHANGEIon exchange (IX) h
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# Minimally skilled labor - $14.50
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Figure 5-4POU Activated AluminaO&M
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Chang, S.D., W.D. Bellamy and H. Ru
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EPA (1997). Annotated Outline for T
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Hund, R., E. Lomaquahu, A. Eaton an
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Mortazavi, S., K. Volchek, A. Tremb
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WMA, Inc. (1995). Arsenic: Impact S
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Table A1 - VSS Document Capital Cos
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Appendix BWater Model Capital CostB
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Table B2.1 - Base Costs Obtained fr
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Table B10.1 - Base Costs Obtained f
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Table C1.1 - Base Costs Obtained fr
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Table C11.1 - Base Costs Obtained f
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Appendix DBasis for Revised Activat
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much more oversight than most small
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Basis. An old activated alumina des
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Basis. The Water Model provided con
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systems could underestimate the nee
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For design flows greater than 1 mgd
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The source water at Plant C has the
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length of 10,000 BV for 7 # pH < 8
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The arsenic loaded onto the column
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column. The Phase 3 Report noted th
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The lower bound run length at pH 6
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Basis. The labor requirements when
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23. The disposal cost for the spent
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8. US EPA. Guide for Implementing P
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APPENDIX E: BASIS FOR REVISED ANION
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6. The capital costs include a redu
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Table E-2Percentage of Ground Water
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12. The building cost to house the
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15. The second major component in t
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Arsenic in the regeneration brine w
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12. Clifford, D.A. G. Ghurye et al.
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Technologies and Costs for Removal of Arsenic From Drinking Water

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