Technologies and Costs for Removal of Arsenic From Drinking Water

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Hering et al. (1996) observed the opposite effect. In coagulation experiments with ferricchloride over the pH range of 4 to 9, pH did not appear to influence the As(V) removal. However,strong pH dependence was observed for As(III) in coagulation experiments with ferric chloride, witha minimum in removal efficiency at pH 6.0.Effect of Initial As(III)/As(V) ConcentrationLogsdon et al. (1974) conducted several jar tests on spiked well water to analyze the initialconcentration and form of arsenic, and determine the type of coagulant most effective in arsenicremoval. The study found the initial arsenic concentration to have a significant effect on removals.For initial As(V) concentrations between 0.1 and 1.0 mg/L, a dosage of 30 mg/L of either alum orferric sulfate in the optimum pH range removed over 95 percent As(V). Above an initialconcentration of 1.0 mg/L, removals decrease with increasing concentrations. For concentrations ofAs(III) greater than 0.1 mg/L, neither alum nor ferric sulfate dosed at 30 mg/L could remove As(III)to concentrations below 0.05 mg/L. In both cases, higher coagulant dosages (60 to 100 mg/L) resultedin higher removals.Hering et al. (1996) demonstrated in coagulation experiments, with ferric chloride dose of 4.9mg/L at pH 7.0 and varied initial arsenic concentration from 2 to 100 µg/L, that both As(III) and As(V)removal was independent of initial concentration. Cheng et al. (1994) showed that As(V) removalwas independent of initial concentration when treated with 20 mg/L of alum and 30 mg/L of ferricchloride while varying the initial As(V) concentration from 2.2 to 128 µg/L.Effect of Co-occurring Inorganic SolutesCo-occurring inorganic solutes, such as sulfate and calcium, may compete for surface bindingsites onto oxide surfaces and influence the adsorption of trace contaminants, such as arsenic. Heringet al. (1996) investigated the effects of sulfate and calcium on the efficiency of As(III) and As(V)removal during coagulation with 4.9 mg/L of ferric chloride. The results indicated that at pH below7.0, As(III) removal was significantly decreased in the presence of sulfate. However, only a slightdecrease in As(V) was observed. At higher pH, removal of As(V) was increased in the presence ofcalcium.2-4
Optimization Hierarchy for Coagulation/Filtration FacilitiesMcNeill and Edwards (1997a) developed a simple model for predicting As(V) concentrationduring coagulation with alum or ferric salts. Using inputs of aluminum hydroxide formed, ferrichydroxide present in the influent, ferric hydroxide formed, and a single sorption constant, the modelpredicted As(V) removal to within 13% for the 25 utility sampling events in this study. The authorssuggested an optimization hierarchy strategy for coagulation/filtration facilities which are unable tomeet arsenic removal requirements with their existing treatment scheme. If any As(III) is present inthe raw water, the most cost-effective method of improving removal is to convert poorly sorbedAs(III) to As(V). Thereafter, for facilities practicing alum coagulation, it is critical to minimizeresidual soluble aluminum to enhance the formation of aluminum hydroxide solids which mediate theAs(V) removal. Jar testing should be performed to identify pH and coagulant dosage that might bealtered to reduce aluminum residuals. The final option is to increase the coagulant dosage or toconsider changing the coagulant type.Field StudiesThe field operation of two coagulation filtration plants was studied by Battelle MemorialInstitute, with funding from EPA (EPA, June 2000). One plant (Plant A) uses ozonation coupled withcoagulation/filtration to treat up to 600 mgd. The other water system (Plant B) relies on coagulation,sedimentation, and filtration, and was designed to treat a much lower daily flow (62.5 mgd). Bothplants demonstrated the ability to consistently reduce moderately high average influent arsenicconcentrations (7.5 and 19.1Fg/L) to less than 5 Fg/L (3.5 and 4.0 Fg/L) in finished water.Furthermore, it should be noted that these plants were not using optimal coagulant and/or polymerdoses, and were not operated at the ideal pH for arsenic removal.Based on the observation of the field operation of these systems, adsorption andcoprecipitation of As(V) with iron and aluminum flocs appears to be the principal mechanism forarsenic removal at these plants. As part of this study, sludge samples were collected from both PlantA and Plant B and subjected to TCLP-testing. However, based on the results of the TCLP, thesesludges would not be characterized as hazardous wastes.SummaryCoagulation technology can successfully achieve As(V) removals greater than 90 percent. Asnoted in the field study discussed above, coagulation/filtration plants have demonstrated the capacity2-5
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
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Page 23: ends up as ferric hydroxide. In alu
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Page 33 and 34: Field StudiesSurveys of lime soften
Page 35 and 36: Effect of pHpH may have significant
Page 37 and 38: RegenerationRegeneration of AA beds
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Page 41 and 42: applicability of IX at a particular
Page 43 and 44: TABLE 2-1Typical IX Resins for Arse
Page 45 and 46: solution strength. Arsenic elutes r
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Page 51 and 52: arsenic size distribution to correl
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Page 59 and 60: TABLE 2-10Arsenic Removal with RO a
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Page 63 and 64: 2.6 ALTERNATIVE TECHNOLOGIES2.6.1 I
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Page 69 and 70: 3.0 TECHNOLOGY COSTS3.1 INTRODUCTIO
Page 71 and 72: included in the estimates presented
Page 73 and 74: Table 3-3Water Model Capital Cost B
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3.2.3 Implementing TDP Recommended
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sources. The September 1998 index v
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Amortization, or capital recovery,
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3.3 ADDITIONAL CAPITAL COSTSThe cos
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PilotingThe Technology Design Panel
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The 1993 Technology and Cost Docume
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cause disinfection by-product (DBP)
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Figure 3-1Pre-oxidation - 1.5 mg/L
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3.6 PRECIPITATIVE PROCESSES3.6.1 Co
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enhanced coagulation treatment plan
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Figure 3-4Enhanced Coagulation/Filt
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Small Systems (Less than 1 mgd)The
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Figure 3-6Coagulation Assisted Micr
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3.6.6 Enhanced Lime SofteningEnhanc
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Figure 3-8Enhanced Lime SofteningO&
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3. Empty Bed Contact Time (EBCT) is
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For design flows greater than 1 mgd
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Figure 3-9Activated AluminaCapital
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Figure 3-11Activated Alumina (pH 8
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Figure 3-13Activated Alumina (pH Ad
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3.7.2 Granular Ferric HydroxideGran
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6. The capital costs include a redu
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Figure 3-15Bed Volumes to Arsenic B
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Figure 3-17Anion Exchange (< 20 mg/
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Figure 3-19Anion Exchange (20-50 mg
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quality feed stream and often requi
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Figure 3-20Greensand FiltrationCapi
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3.11 COMPARISON OF COSTSThe April 1
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4.0 RESIDUALS HANDLING AND DISPOSAL
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mechanical dewatering processes. Wh
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Storage lagoons are best suited for
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the current Industrial Pretreatment
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4.3.3 Dewatered Sludge Land Applica
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usually determined by the Paint Fil
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for arsenic toxicity by a substanti
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The solids content of the backwash
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carbonate hardness removal produces
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Domestic sewage means untreated san
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4.4.10 Reverse OsmosisReverse osmos
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Figure 4-1Anion Exchange (< 20 mg/L
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Figure 4-3Anion Exchange (20-50 mg/
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Figure 4-9Activated Alumina (pH 7 -
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Figure 4-11Activated Alumina (pH Ad
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Figure 4-13Greensand FiltrationWast
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5.0 POINT-OF-ENTRY/POINT-OF-USE TRE
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chromatographic peaking, which occu
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5.3.1 Case Study 1: Fairbanks, Alas
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Manufacturer and laboratory data su
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Figure 5-2POU Reverse OsmosisO&M Co
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# Installation time - 1 hour unskil
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Figure 5-3POU Activated AluminaTota
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6.0 REFERENCESAmy, G.L. and P. Bran
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Cooperative Research Centres for Wa
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Fuller, C.C., J.A. Davis, G.W. Zell
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Le, X.C., and M. Ma (1998). “Dete
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Scott, K., J. Green, H.D. Do and S.
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Appendix AVery Small Systems Capita
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Table A4 - VSS Document Capital Cos
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Table B1.1 - Base Costs Obtained fr
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Table B11.1 - Base Costs Obtained f
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Table B13.1 - Base Costs Obtained f
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Appendix CW/W Cost Model Capital Co
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Table C2.1 - Base Costs Obtained fr
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Table C10.1 - Base Costs Obtained f
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APPENDIX D: BASIS FOR REVISED ACTIV
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Company case study is 18 minutes (2
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egressed against their respective v
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costs for small systems is as follo
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were based on $40/sq ft). The proce
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Basis. Capital cost components incl
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The source water at Plant D has the
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equation y = (2*10 -8 )x 2 + 0.0002
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The maximum run length is 18,500 be
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Since the available arsenic capacit
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If the first column can be operated
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which includes lighting, ventilatio
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disposal costs, if needed, are cove
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Appendix EBasis for Revised Anion E
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2. The estimated cost of the anion
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9. The capital costs have been esti
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Thus, the cost of a road and fence
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length when sulfate is at or below
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the labor rates for both large and
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2. US EPA. Technologies and Costs f
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Technologies and Costs for Removal of Arsenic From Drinking Water

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