Technologies and Costs for Removal of Arsenic From Drinking Water

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3.6.5 Lime SofteningLime softening (LS) has been widely used for reducing hardness in large water treatmentsystems. The LS removal mechanism is discussed in Chapter 2. As(III) or As(V) removal by LS islargely pH dependent, and pre-oxidation of arsenite to arsenate will significantly improve arsenicremoval efficiencies. Pre-oxidation technologies are discussed in Section 3.5.Lime softening is unlikely to be installed solely for arsenic removal. Systems consideringinstallation of this technology should design the process to operate in at a pH > 10.5 if high removalefficiency is needed for compliance. Costs are not presented for this option. Key design parametersthat can be used with the cost models are presented for systems that wish to explore this option.Considerable amounts of sludge are produced by the LS process. Large systems may find iteconomically feasible to install recalcination equipment to recover and reuse the process sludge andreduce disposal costs.Small Systems (Less than 1 mgd)The VSS Model provides no estimation methods for LS treatment. Therefore, the Water Modelwould have to be used to estimate capital and O&M costs for all LS treatment plants with less than1 mgd capacity. The following design criteria can be used in the development of capital and O&Mcost estimates:# Package plant for all small systems;# Lime dose, 250 mg/L; and# Carbon dioxide (liquid), 35 mg/L for recarbonation.Large Systems (Greater Than 1 mgd)The W/W Cost model can be used to develop capital and O&M cost estimates for large LSplants. The following design criteria can be used to estimate capital and O&M costs:# Lime dose, 250 mg/L;# Carbon dioxide (liquid), 35 mg/L for recarbonation;# Rapid mix, 1 minute;# Flocculation, 20 minutes;# Sedimentation, 1500 gpd/ft 2 using circular tanks; and# Dual media gravity filters, 5 gpm/ft 2 .3-32
3.6.6 Enhanced Lime SofteningEnhanced LS involves modifications to the typical LS treatment process to adjust the pH >10.5 by increased lime dosage and possibly increased soda ash dosage. This may result in the needfor pH adjustment of treated water via recarbonation. Source waters with high influent As(III)concentrations may require pre-oxidation for conversion of arsenite to arsenate. Pre-oxidationtechnologies are discussed in Section 3.5.For the purpose of estimating costs, it was assumed that an existing LS plant could achieve 50percent removal of arsenic from the source water prior to modification, i.e., enhancement. It was alsoassumed that the only added O&M burden would result from power and materials costs, no additionallabor was assumed to be required. Costs presented are associated with the enhancement only, andare in addition to current annual debt incurred by the utility.Small Systems (Less than 1 mgd)The Water Model was used to estimate capital and O&M costs for small enhanced LStreatment plants. The following design criteria were used in the development of capital and O&Mcost estimates:# Additional lime dose, 50 mg/L;# Chemical feed system for increased lime dose;# Additional carbon dioxide (liquid), 35 mg/L for recarbonation; and# Chemical feed system for increased carbon dioxide dose.Large Systems (Greater Than 1 mgd)The W/W Cost model was used to develop capital and O&M cost estimates for largeenhanced LS plants. The following design criteria were used to estimate capital and O&M costs:softening.# Additional lime dose, 50 mg/L;# Chemical feed system for increased lime dose;# Additional carbon dioxide (liquid), 35 mg/L for recarbonation; and# Chemical feed system for increased carbon dioxide dose.Figures 3-7 and 3-8 present cost curves and equations for removal of arsenic by enhanced lime3-33
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United StatesEnvironmental Protecti
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ACKNOWLEDGMENTSThis document was pr
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2.5.7 Reverse Osmosis .............
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5.0 POINT-OF-ENTRY/POINT-OF-USE TRE
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LIST OF FIGURES2-1 Pressure Driven
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LIST OF ACRONYMSAAAWWAAWWARFBLSBVC/
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POUpoint-of-useppbparts per billion
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# Alternative treatment processes s
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ends up as ferric hydroxide. In alu
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Optimization Hierarchy for Coagulat
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Substantial arsenic removal has bee
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Vickers et al. (1997) reported that
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was reduced to 0.05 mg/L when the i
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Field StudiesSurveys of lime soften
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Effect of pHpH may have significant
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RegenerationRegeneration of AA beds
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een developed provide important inf
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applicability of IX at a particular
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TABLE 2-1Typical IX Resins for Arse
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solution strength. Arsenic elutes r
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2.4.12 Typical Design ParametersThr
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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 71 and 72: included in the estimates presented
Page 73 and 74: Table 3-3Water Model Capital Cost B
Page 75 and 76: 3.2.3 Implementing TDP Recommended
Page 77 and 78: sources. The September 1998 index v
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Page 81 and 82: 3.3 ADDITIONAL CAPITAL COSTSThe cos
Page 83 and 84: PilotingThe Technology Design Panel
Page 85 and 86: The 1993 Technology and Cost Docume
Page 87 and 88: cause disinfection by-product (DBP)
Page 89 and 90: Figure 3-1Pre-oxidation - 1.5 mg/L
Page 91 and 92: 3.6 PRECIPITATIVE PROCESSES3.6.1 Co
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Page 95 and 96: Figure 3-4Enhanced Coagulation/Filt
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Page 103 and 104: Figure 3-8Enhanced Lime SofteningO&
Page 105 and 106: 3. Empty Bed Contact Time (EBCT) is
Page 107 and 108: For design flows greater than 1 mgd
Page 109 and 110: Figure 3-9Activated AluminaCapital
Page 111 and 112: Figure 3-11Activated Alumina (pH 8
Page 113 and 114: Figure 3-13Activated Alumina (pH Ad
Page 115 and 116: 3.7.2 Granular Ferric HydroxideGran
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Page 119 and 120: Figure 3-15Bed Volumes to Arsenic B
Page 121 and 122: Figure 3-17Anion Exchange (< 20 mg/
Page 123 and 124: Figure 3-19Anion Exchange (20-50 mg
Page 125 and 126: quality feed stream and often requi
Page 127 and 128: Figure 3-20Greensand FiltrationCapi
Page 129 and 130: 3.11 COMPARISON OF COSTSThe April 1
Page 131 and 132: 4.0 RESIDUALS HANDLING AND DISPOSAL
Page 133 and 134: mechanical dewatering processes. Wh
Page 135 and 136: Storage lagoons are best suited for
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Page 139 and 140: 4.3.3 Dewatered Sludge Land Applica
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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 4-5Coagulation Assisted Micr
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Figure 4-7Coagulation Assisted Micr
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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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