Technologies and Costs for Removal of Arsenic From Drinking Water

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water characteristics must be considered when evaluating POE and POU devices for arsenic removal.To be effective these devices should work with minimal attention and be relatively inexpensive forthe user. Reverse osmosis, activated alumina, and ion exchange are three treatment techniques thathave been evaluated and shown to be effective. This chapter looks at the removals achieved by eachof these three treatment techniques, and presents total costs for each treatment option.5.2 VARIABLES AFFECTING REMOVAL EFFICIENCY5.2.1 SpeciationArsenic speciation is critical to the removal efficiency of every technology presented in thisdocument. As previously discussed, inorganic arsenic occurs in two primary forms, arsenite (AsIII)and arsenate (AsV). Arsenite is removed less efficiently because it predominantly occurs in theuncharged (H 3 AsO 3 ) state in source waters with a pH of less than 9.0. The dominant arsenate forms2-are anionic species, H 2 AsO 4 and HAsO 4- . Identification of the ionic form of arsenic is necessary forselection and design of a removal process. All technologies discussed in this document removearsenate more effectively than arsenite. Therefore, if arsenite is the predominant species present,oxidation to arsenate may be required to achieve the desired removal.5.2.2 pHAs previously stated, pH plays a significant role in determining the removal efficiency of aparticular technology. Most processes are relatively unaffected by pH in the range of 6.5 to 9.0.However, activated alumina studies have shown the optimum pH for arsenic removal to be between5.5 and 6.0, and reverse osmosis processes may require pH adjustment to prevent precipitation ofsalts on the membrane surface.5.2.3 Co-occurrenceCo-occurrence of inorganic contaminants, such as sulfate and silica, as well as suspendedsolids, can cause interference with arsenic removal. Sulfate is preferentially adsorbed relative toarsenic by ion exchange processes. This preference can result in another phenomenon known as5-2
chromatographic peaking, which occurs when arsenic is displaced on the resins by the sulfate causingeffluent concentrations in excess of the influent levels.A slight decrease in activated alumina performance has been seen in waters with high sulfateconcentration; however, the effect is not as great as in ion exchange processes. At higher treatmentpH levels silica may also be preferred relative to arsenic.5.3 POE/POU DEVICE CASE STUDIESSeveral field studies conducted to evaluate the effectiveness of POE and POU treatment unitsfor arsenic removal indicate that POE and POU systems can be effective alternatives to centralizedtreatment options. These studies evaluated reverse osmosis (RO), activated alumina (AA), and ionexchange (IX) processes.The following sections present the results of two of these studies. Table 5-1 summarizessource water quality and influent arsenic concentrations. Table 5-2 summarizes the arsenic removalsachieved by each of the technologies evaluated.5-3
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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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2.5.2 Important Factors for Membran
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arsenic size distribution to correl
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AWWARF (1998) also performed UF pil
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presumably due to changes in electr
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RO performance is adversely affecte
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TABLE 2-10Arsenic Removal with RO a
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eversal is the decreased potential
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2.6 ALTERNATIVE TECHNOLOGIES2.6.1 I
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20 mg As per gram of iron was remov
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The most significant weakness of th
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3.0 TECHNOLOGY COSTS3.1 INTRODUCTIO
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included in the estimates presented
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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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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
Page 141 and 142: usually determined by the Paint Fil
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Page 145 and 146: The solids content of the backwash
Page 147 and 148: carbonate hardness removal produces
Page 149 and 150: Domestic sewage means untreated san
Page 151 and 152: 4.4.10 Reverse OsmosisReverse osmos
Page 153 and 154: Figure 4-1Anion Exchange (< 20 mg/L
Page 155 and 156: Figure 4-3Anion Exchange (20-50 mg/
Page 157 and 158: Figure 4-5Coagulation Assisted Micr
Page 159 and 160: Figure 4-7Coagulation Assisted Micr
Page 161 and 162: Figure 4-9Activated Alumina (pH 7 -
Page 163 and 164: Figure 4-11Activated Alumina (pH Ad
Page 165 and 166: Figure 4-13Greensand FiltrationWast
Page 167: 5.0 POINT-OF-ENTRY/POINT-OF-USE TRE
Page 171 and 172: 5.3.1 Case Study 1: Fairbanks, Alas
Page 173 and 174: Manufacturer and laboratory data su
Page 175 and 176: Figure 5-2POU Reverse OsmosisO&M Co
Page 177 and 178: # Installation time - 1 hour unskil
Page 179 and 180: Figure 5-3POU Activated AluminaTota
Page 181 and 182: 6.0 REFERENCESAmy, G.L. and P. Bran
Page 183 and 184: Cooperative Research Centres for Wa
Page 185 and 186: Fuller, C.C., J.A. Davis, G.W. Zell
Page 187 and 188: Le, X.C., and M. Ma (1998). “Dete
Page 189 and 190: Scott, K., J. Green, H.D. Do and S.
Page 191: Appendix AVery Small Systems Capita
Page 194 and 195: Table A4 - VSS Document Capital Cos
Page 197 and 198: Table B1.1 - Base Costs Obtained fr
Page 207 and 208: Table B11.1 - Base Costs Obtained f
Page 209 and 210: Table B13.1 - Base Costs Obtained f
Page 211: Appendix CW/W Cost Model Capital Co
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Table C6.1 - Base Costs Obtained fr
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Table C8.1 - 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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