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Control of hydrogen sulfide from groundwater using packed-bed anion exchange and other technologies

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Control of hydrogen sulfide from groundwater using packed-bed anion exchange and other technologies
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Cotrino, Camilo Romero
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Drinking water treatment
Groundwater
Conversion
Removal
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Dissertations, Academic -- Environmental Engineering -- Masters -- USF
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theses   ( marcgt )
non-fiction   ( marcgt )

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Abstract:
ABSTRACT: Hydrogen sulfide imparts odors and taste to drinking water and can be corrosive to distribution systems. Groundwater sources used to produce drinking water tend to have sulfide concentrations ranging from below 0.1 to over 3 mg/L. Under anaerobic conditions, hydrogen sulfide can be formed from reduction of sulfate and elemental sulfur through chemical or biological reactions. Therefore, to decrease the potential for hydrogen sulfide in water systems, control of all forms of sulfur should be consistent.Hydrogen sulfide in groundwater can be controlled through conversion or removal mechanisms. Conversion reactions result from chemical or biological reactions that oxidize hydrogen sulfide to elemental sulfur or sulfate, depending on the reaction conditions. Removal reactions include stripping, anion exchange, or formation of a precipitate that can be removed through solid/liquid separation processes.In many groundwater treatment systems, hydrogen sulfide is controlled through ^aeration, chlorine oxidation, or a combination of these two methods. In addition to chlorine, other oxidizers can be used including hydrogen peroxide, UV, ozone, or potassium permanganate. The main factors that influence whether hydrogen sulfide is oxidized to elemental sulfur and/ or sulfate are pH, temperature, and the type and dose of oxidant.In recent years alternative treatments technologies such as anion exchange, have become available. It is interesting to note that this technology was proposed as early as the middle of last century. Although large scale anion exchange has not been implemented, its application for the removal of hydrogen sulfide is feasible based on anion exchange principles.This research was designed to evaluate feasible options for controlling hydrogen sulfide from groundwater sources. The feasibility of using anion exchange was investigated through pilot-scale testing of four groundwater sources. In addition, the performance of typical and alternative chemic al oxidizers to control hydrogen sulfide was evaluated.
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Thesis (M.A.)--University of South Florida, 2006.
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Includes bibliographical references.
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by Camilo Romero Cotrino.
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Document formatted into pages; contains 117 pages.

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ABSTRACT: Hydrogen sulfide imparts odors and taste to drinking water and can be corrosive to distribution systems. Groundwater sources used to produce drinking water tend to have sulfide concentrations ranging from below 0.1 to over 3 mg/L. Under anaerobic conditions, hydrogen sulfide can be formed from reduction of sulfate and elemental sulfur through chemical or biological reactions. Therefore, to decrease the potential for hydrogen sulfide in water systems, control of all forms of sulfur should be consistent.Hydrogen sulfide in groundwater can be controlled through conversion or removal mechanisms. Conversion reactions result from chemical or biological reactions that oxidize hydrogen sulfide to elemental sulfur or sulfate, depending on the reaction conditions. Removal reactions include stripping, anion exchange, or formation of a precipitate that can be removed through solid/liquid separation processes.In many groundwater treatment systems, hydrogen sulfide is controlled through ^aeration, chlorine oxidation, or a combination of these two methods. In addition to chlorine, other oxidizers can be used including hydrogen peroxide, UV, ozone, or potassium permanganate. The main factors that influence whether hydrogen sulfide is oxidized to elemental sulfur and/ or sulfate are pH, temperature, and the type and dose of oxidant.In recent years alternative treatments technologies such as anion exchange, have become available. It is interesting to note that this technology was proposed as early as the middle of last century. Although large scale anion exchange has not been implemented, its application for the removal of hydrogen sulfide is feasible based on anion exchange principles.This research was designed to evaluate feasible options for controlling hydrogen sulfide from groundwater sources. The feasibility of using anion exchange was investigated through pilot-scale testing of four groundwater sources. In addition, the performance of typical and alternative chemic al oxidizers to control hydrogen sulfide was evaluated.
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Control of Hydrogen Sulfide from Groundwat er Using Packed-Bed Anion Exchange and Other Technologies by Camilo Romero Cotrino A thesis submitted in partial fulfillment of the requirements for the degree of Master of Science in Environmental Engineering Department of Civil and Environmental Engineering College of Engineering University of South Florida Major Professor: Audrey D. Levine, Ph.D. Robert P. Carnahan, Ph.D. James Griffin, Ph.D. Date of Approval: April 10, 2006 Keywords: drinking water treatment, gr oundwater, conversion, removal, areation Copyright 2006, Camilo Romero Cotrino

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Dedication I would like to dedicate this work to my family. Although they reside far from me, their support and prayers brings them clos e to my heart and ha s made the challenge of the work found within this thesis easier.

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Acknowledgements I would like to first expre ss my gratitude to my major professor Dr. Levine who has provided the opportunity to work and lear n from her. Her dedication to her students and to the advancement the field of environmen tal engineering is admirable. I would also like to thanks Dr. Robert P. Carnahan and Dr James Griffin for agr eeing be on my thesis committee I wish to express my thanks to Aaron Roberts who helped during the process of data collection. Similarly, I would like to ac knowledge those who a ssisted me with the laboratory analysis of the samples who we re: Rochelle Minnis, Mindy Decker, Erin McMahan, Francis Eshun, and Mark Velasquez. Finally, I want to thanks my aunt and uncle for their support, patience, and love during the last year and half. They ma de my life easier in this country. I would like to recognize Al oha Utilities, Inc for funding the main project and Tonka Equipment for proving the columns, resin, and technical support.

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i Table of Contents List of Tables................................................................................................................. ....iii List of Figures................................................................................................................ .....v Abstract....................................................................................................................... .....viii Introduction................................................................................................................... ......1 Objectives..................................................................................................................... ......4 Background..................................................................................................................... ....5 Sulfur Cycle............................................................................................................5 Sulfide Species in Groundwater..............................................................................7 Regulations Pertaining to the Control Hydrogen Sulfide.......................................8 Treatment Options for Control Hydrogen Sulfide..................................................9 Conversion Options..................................................................................10 Removal Options......................................................................................14 Removal of Hydrogen Sulfide from Gr oundwater Using Packed-Bed Anion Exchange Technology…………………………………………………………….20 Introduction...........................................................................................................21 Background...........................................................................................................21 Regulations...............................................................................................22 Influencing Factors on Treatment Options...............................................23 Anion Exchange........................................................................................25 Materials and Methods..........................................................................................28 Strong Base Anion Resin..........................................................................29 Pilot Scale Test.........................................................................................29 Source Water Quality................................................................................33 Results...................................................................................................................34 Hydrogen Sulfide and Other Anions Removal.........................................35 Influencing Factors...................................................................................37 Discussion.............................................................................................................40

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ii Conclusions...........................................................................................................42 Acknowledgements...............................................................................................43 Comparison of Alternative Technologies for Control of Hydrogen Sulfide from Groundwater Sources…………………………………………………………………….44 Introduction...........................................................................................................45 Background...........................................................................................................46 Sulfur Transformations.............................................................................47 Regulatory Framework for Cont rol of Hydrogen Sulfide.........................47 Water Quality Variables of Importa nce for the Control of Hydrogen Sulfide.......................................................................................................48 Aeration.....................................................................................................50 Anion Exchange........................................................................................51 Oxidation Technologies for Control Hydrogen Sulfide............................52 Methodology.........................................................................................................55 Sampling...................................................................................................56 Pilot-Scale Test.........................................................................................59 Anion Exchange........................................................................................60 Oxidation Tests.........................................................................................61 Water Quality............................................................................................62 Results and Discussion.........................................................................................64 Anion Exchange........................................................................................64 Pilot-Scale Testing of Oxidation Reactions..............................................67 Water Quality Comparison of Technologies............................................73 Conclusions...........................................................................................................77 Acknowledgments.................................................................................................78 Conclusions.................................................................................................................... ...80 Engineering Implications..................................................................................................82 Additional Research..........................................................................................................84 References..................................................................................................................... ....86 Appendices..................................................................................................................... ...91 Appendix A: Pilot Column Design.......................................................................92 Configuration............................................................................................92 Operating and Regenerating Procedure....................................................94 Brine Mixing Instructions.........................................................................96 Appendix B: Summary of Raw Wate r Quality and Anion Exchange..................97

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iii List of Tables Table 1. Oxidation States fo r Common Sulfur Compunds.................................................6 Table 2. FDEP Hydrogen Sulfide Treatment Recommendations.......................................9 Table 3. Main Characteristics of Aerators Using to Control Hydrogen Sulfide...............15 Table 4. Anionic and Cationi c Resin Characteristics.......................................................16 Table 5. Possible Treatments Options to Control the Presence of Hydrogen Sulfide (FDEP chapter 62-555.315(5))..............................................................23 Table 6. Treatment Options and Infl uencing Efficiency Factors......................................24 Table 7. SBA Resin Selectivity........................................................................................28 Table 8. Tulson A-72 MP Resin Characteristics...........................................................29 Table 9. Summary of the Analytical Methods Used for Water Analysis.........................32 Table 10. Regeneration Steps...........................................................................................33 Table 11. Overview of Variable Tested in the Project......................................................34 Table 12. Comparison of Stoichiometric Chemical Reactions for Oxidation of Hydrogen Sulfidea............................................................................................53 Table 13. Summary of Analyt ical Methods Used for Ch aracterization of Water Samples from Pilot-Scale Testing....................................................................58 Table 14. Parameters of Anion Exchange Resins Tested in this Project (From Manufacturers Literature and MSDS Sheets).................................................61 Table 15. Summary of Oxidation Tests Conducted on Water from the System...............62 Table 16. Qualitative Comparison of Im pacts of Treatment Technologies on Water Quality...................................................................................................76 Table 17. Raw Water Quality Summary from Well A.....................................................98 Table 18. Raw Water Quality Summary from Well B......................................................99 Table 19. Raw Water Quality Summary from Well C....................................................100 Table 20. Raw Water Quality Summary from Well D...................................................101 Table 21. Anion Exchange Data from Well A................................................................102

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iv Table 22. Anion Exchange Data from Well B................................................................104 Table 23. Anion Exchange Data from Well C................................................................106 Table 24. Anion Exchange Data from Well D................................................................110 Table 25. Chlorine Demand Test for Raw Water from Well A......................................112 Table 26. Chlorine Demand Test for Ani on Exchange Effluent from Well A...............113 Table 27. Chlorine Demand Test for Raw Water from Well B......................................114 Table 28. Chlorine Demand Test for Ani on Exchange Effluent from Well B...............115 Table 29. Chlorine Demand Test for Raw Water from Well D......................................116 Table 30. Chlorine Demand Test for Ani on Exchange Effluent from Well D...............117

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v List of Figures Figure 1. Simplified Sulfur Cycle. Ad apted from Sawyer et al (2003)..............................7 Figure 2. Sulfate Species Distribution in Groundwater as Function of pH........................8 Figure 3. Sulfur Species Predominance Area as Function of Oxidation Potential (pE) and pH.......................................................................................................10 Figure 4. Surface Strong Ba se Resin Micrographs...........................................................17 Figure 5. pH Impacts in the Aeration and Anion Exchange Technologies......................25 Figure 6. Theoretic Sulfur Species Distri bution in Function of the Water pH.................26 Figure 7. Anion Exchange Column Photogr aphs. a) Control Panel Allows the Operation of all Anion Exchange Cycles; b) Anion Exchange Overall View..................................................................................................................30 Figure 8. Comparison Between the Average BV and the H2S Concentration for Each Well..........................................................................................................35 Figure 9. Comparison Chlorine Demand in Raw Water and Anion Exchange Effluent for Each Well......................................................................................36 Figure 10. Chlorine Demand as Functi on of Influent Hydrogen Sulfide Concentration..................................................................................................37 Figure 11. Comparison Between the Average BV for Runs With Air and Without in Wells A and B.............................................................................................38 Figure 12. Predictor BV Model Based on the Initial Hydrogen Sulfid e and Sulfate Concentrations in meq/L for Run With and Without Air...............................39 Figure 13. Scanning Electron Micrographs from a), b), c) Resin From Well B, and d) Resin From Well A.....................................................................................40 Figure 14. Theoretical Distribution of Hydr ogen Sulfide and Polysulfides in Wter as a Function of pH Asuming Polysu lfides are in Equilbrium With HS(Equilibrium constants from Morse et al. 1987, Stumm and Morgan 1996 )................................................................................................49 Figure 15. Scanning Electron Micrograph of Anion Exchange Resin Used for Testing Sulfide Removal.................................................................................52

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vi Figure 16. Predominance Area Diagram Showing the Theoretical Equilibrium Forms of Sulfur as a Function of Oxidation Potential (pE) and pH. Thermodynamic Constants from Stumm and Morgan 1999. (pE is Equal to the Log of the Equilibri um Constant Normalized to One Electron Transfer)...........................................................................................54 Figure 17. Comparison of Oxidation Pote ntials Associated With Oxidant Chemicals Used for Chemical Oxidation of Hydrogen Sulfide. The Oxidation Potential is Reported in Terms of Volts Per Single Electron Transfer...........................................................................................................55 Figure 18. Photograph of Inside of Pilot Treatment Trailer Showing Anion Exchange Contact Tanks, UV Reactor, Brine Thank, and Pipeline Reactors...........................................................................................................60 Figure 19. Comparison of the Important Wate r Quality Parameters of a) Hydrogen Sulfide, b) Sulfate, c) TOC, d) Ch loride, e) pH, and f) Turbidity. Data from 1998-2005..............................................................................................63 Figure 20. Comparison of Impacts of Anion Ex change (AE) on a) Hydrogen Sulfide, Organic Carbon (TOC) and b) Sulfate, and Chloride in Pilot Tests Conducted on Water from We ll 9 During the Summer of 2005............65 Figure 21. Percent Sulfide Removal Followi ng Anion Exchange Treatment of Water from Well 9 as a Function of Volume of Water Treated in Pilot Treatment Unit. Influent Sulfide Concentrations Ranged from 2 to 3 mg/L................................................................................................................66 Figure 22. Comparison of Incremental pH Change Associated With Addition of Chlorine to Water from Well 9 Following Treatment by Anion Exchange.........................................................................................................67 Figure 23. Comparison of the Concentration of Sulfide Oxidized and the Concentration of Turbidity in Chlorinated Water from Wells 2, 3, 4, 8, and 9 Based on Pilot-Plant Testin g Using Sodium Hypochlorite at Ambient pH.....................................................................................................68 Figure 24. Impact of Hydrogen Peroxide and Chlorine Oxidation of Hydrogen Sulfide on Levels of Total Sulfide and Turbidity in Water from Well 9 at Ambient pH.................................................................................................70 Figure 25. Impact of Hydrogen Peroxide and Chlorine Oxidation of Hydrogen Sulfide on Levels of Total Sulfide and Turbidity in Water from Well 9 at Elevated pH (~ pH 8.3)...............................................................................70 Figure 26. Impact of Using Ultraviolet ( UV) Irradiation Coupled With Chlorine Oxidation of Hydrogen Sulfide on Levels of Total Sulfide and Turbidity in Water from Well 9......................................................................72 Figure 27. Impact of Using Hydrogen Per oxide Coupled With Ultraviolet (UV) Irradiation Followed by Chlorine Oxidation on Levels of Total Sulfide and Turbidity in Water from Well 9..............................................................73

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vii Figure 28. Effectiveness of Aeration, Anion Exchange, and Oxidation for Reduction of Hydrogen Sulfide a nd Chlorine Demand Associated..............74 Figure 29. Impact of Aeration, Anion Exchange, and Oxidation on Organic Carbon (TOC) and Sulfate Levels in Treated Water......................................75 Figure 30. Anion Exchange Control Panel.......................................................................93

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viii Control of Hydrogen Sulfide from Groundwater Using Packed-Bed Anion Exchange and Other Technologies Camilo Romero Cotrino ABSTRACT Hydrogen sulfide imparts odors and taste to drinking water and can be corrosive to distribution systems. Groundwater sources used to produce drinking water tend to have sulfide concentrations ra nging from below 0.1 to over 3 mg/L. Under anaerobic conditions, hydrogen sulfide can be formed from reduction of sulfate and elemental sulfur through chemical or bi ological reactions. Therefore, to decrease the potential for hydrogen sulfide in water systems, control of al l forms of sulfur should be consistent. Hydrogen sulfide in groundwater can be controlled through conversion or removal mechanisms. Conversion reactions result from chemical or biological reactions that oxidize hydrogen sulfide to elemental sulfur or sulfat e, depending on the reaction conditions. Removal reactions include stripping, anion exchange, or formation of a precipitate that can be removed through solid/liqui d separation processes.

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ix In many groundwater treatment systems, hydrogen sulfide is controlled through aeration, chlorine oxidation, or a combinat ion of these two methods. In addition to chlorine, other oxidizers can be used in cluding hydrogen peroxide, UV, ozone, or potassium permanganate. The main factors th at influence whether hydrogen sulfide is oxidized to elemental sulfur a nd/ or sulfate are pH, temperat ure, and the type and dose of oxidant. In recent years alternative treatments t echnologies such as anion exchange, have become available. It is inte resting to note that this techno logy was proposed as early as the middle of last century. Although larg e scale anion exchange has not been implemented, its application for the removal of hydrogen sulfide is feasible based on anion exchange principles. This research was designed to evaluate feasible options for controlling hydrogen sulfide from groundwater sources. The f easibility of using anion exchange was investigated through pilot-scale testing of four groundwater sources. In addition, the performance of typical and alte rnative chemical oxidizers to control hydroge n sulfide was evaluated.

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1 Introduction The concentration of dissolved hydrogen sulfide in the Floridian aquifer ranges from less than 0.1 to over 3 mg/L (Dell’Or co et al. 1999). A major concern associated with the presence of hydrogen sulfide in potable water sources is that it can impart taste and odor to water and it also contributes to corrosion. The presence of hydrogen sulfide in groundwater is mainly due to the reducti on of sulfate by anaerobi c bacteria. Exposure to this gas at concentrations from 10 to 20 ppm can result in eye irritation and a sore throat. Hydrogen sulfide gas can be fatal at concentrations over 700 ppm. Reduced forms of sulfur in groundwater include: hydrogen sulf ide, bisulfide, sulfide, and polysulfides. The distribution of reduced sulfur species in groundwater depends on the pH. For pH values below 6, non-ionized hydrogen sulfide is the predominant species. Typicall y, the pH of groundwater ra nges between 6 and 8. The non-ionized hydrogen sulfide decreas es as the pH increases ab ove the pK value of 7 to the point of being negligible at pH 8, and at the same time the concentration of ionized bisulfide increases up to 80%. The polysulfide concentration starts to approach 100% around pH 12. Between pH values of 12 and 14 polysulfide decreases at the same rate that ionized sulfide increases. There are several approach es that can be used to control hydrogen sulfide in potable water. Conversion t echnologies involve chemical or biological oxidation of hydrogen sulfide to elemental sulf ur or sulfate. Alternativel y, treatments technologies can be designed to remove hydrogen sulfide through ga s exchange or ion exchange. It is also possible to use a combination of conversi on and removal by converting the dissolved

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2 hydrogen sulfate to colloidal su lfur that can be removed th rough solid/liquid separation technologies. The addition of chemical oxidizers resu lts in an increase of the water oxidation potential that allows the transformation of the hydrogen sulfide to elemental sulfur or sulfate. The effectiveness of chemical oxidation of hydrogen sulfide is influenced by the pH, oxidizer oxidation potential, and temperatur e of the water source. Typical oxidants include chlorine, oxygen, hydrogen per oxide, oxygen, ozone, and potassium permanganate. Aeration takes advantage of the vola tile nature of the hydrogen sulfide by displacing the gaseous form from water with air. This option is highly dependant on the pH because nonionized hydrogen sulfide is pr esent in low percentages at typical groundwater pH ranges (Thompson et al. 1995 ). Decreasing the pH to 6 or less can increase aeration efficiency. However, the use of aerators may result in biological growth and also promote the formation of colloidal sulfur that increases turbidity and interferes with the effectiveness of disinfection. Anion exchange is an alternative treatment approach that is effective for removing anionic forms of hydrogen sulfide. In addi tion, anion exchange technology is able to remove sulfate, reduce disinfection byproducts precursors, and decrease the chlorine demand in the effluent (Levine et al 2005). This was tested successfully in the removal of nitrate, arsenic, and organic matter (Liang et al 1999, Ghurye et al. 1999, Korngold et al. 2001, and Bolto et al.2002). Additional considerations, apart from a water quality perspectives, need to be analyzed when a hydrogen sulfide treatment is implemented. These considerations include land availability, proximity to ne ighborhoods, chemical delivery, implementation costs, and technical issues such a re-pressurization requirements.

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3 In this re search, pilot tests of an ion exchange packed-bed treatment systems were conducted to evaluate the removal of hydrogen sulfide from groundwater The feasibility of using chemical oxidation was also investig ated. The results and discussion are given in two articles. In the first article, the app lication of anion excha nge technology for the removal of hydrogen sulfide is presented. A comparison between the effectiveness of aeration, anion exchange, and the chemical oxida tion using pilot tests is discussed in the second paper.

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4 Objectives This project was conducted to evaluate th e effectiveness of a bed-packed anion exchange for removal of hydrogen sulfide from groundwater, and to id entify factors that affect process performance. Ion exchange was compared to more traditional hydrogen sulfide control technologies such as ae ration and chemical oxidation. The specific objectives are listed below. 1. Evaluate the effectiveness of a commercial strong base anion resin for removal of hydrogen sulfide from groundwater in west-central Florida. 2. Identify factors that impact th e performance of anion exchange. 3. Test the effectiveness of several chemical oxidants for the oxidation of hydrogen sulfide. 4. Compare the effectiveness of aeration, anion exchange, and chemical oxidation for control of hydrogen sulfide based on water quality parameters.

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5 Background Development of optimum methods for control of hydrogen sulfide depends on water quality, site constraints, and cost. In this secti on, background information related to the sulfur cycle, sulf ur species in groundwater, a nd regulations is provided. Background information about the treatme nt options is also presented. Sulfur Cycle Natural sources of sulfur exist in ro cks and sediments. Biochemical reactions result in transformation of sulfur through different oxida tion states. According to Mardigan and Martinko (2005), only three su lfur oxidation states in nature are significant: 0 (elemental sulfu r), -2 (hydrogen sulfide), and 6 (sulfate). Common sulfur species and their oxidation states are shown in Table 1.

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6Table 1. Oxidation States for Common Sulfur Compunds Compound Oxidation State Organic S (R-SH) -2 Sulfide (H2S) -2 Elemental sulfur (S0) 0 Thiosulfate (S2O3 2-) +2 Sulfur dioxide (SO2) +4 Sulfite (SO3 2-) +4 Sulfate (SO4 2-) +6 Adapted from Mardigan and Martinko (2005) Generation of hydrogen sulfide in groundwat er is a product of biological sulfate reduction or the reduction of el emental sulfur (anaerobic respir ation). Sulfate reduction is carried out by bacteria including Desulfovibrio and Desulfobacter. Sulfate reduction reaction is shown in equation 1. Sulfate reduction can also be represented as part of the sulfur cycle (Figure 1). Microorganisms use assimilative metabolism to convert the elemental sulfur into an amino acid. Dissi milative metabolism produces hydrogen sulfide as the final product of the sulfate reduction. The reduction of elemental sulfur into hydrogen sulfide is an important process among the hyperthermophilic archaea, which are at an optimum at a temperature ra nge between 65 and 110 C (Mardigan and Martinko, 2005). Chemical sulfat e reduction reaction is possible. However, this reaction is only possible at temperatures around 250 C which makes it difficult to occur in groundwater systems that are only one or two centigrade degrees higher that the air temperature (Dohnalek and FitzPatrick, 1983). SO4 2+ 8H+ H2S + 2H2O + 2OH(Equation 1)

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7 Figure 1. Simplified Sulfur Cycle. Adapted from Sawyer et al (2003) Sulfide Species in Groundwater The distribution of reduced sulf ur species as a function of pH is shown in Figure 2. Hydrogen sulfide is the only non-ionized sulfur species pres ent in groundwater. It is the major species in water when the pH is less than 7. The ionic forms of sulfur species in groundwater are bisulfide (HS-) and sulfide (S2-) which are found in waters with pH from neutral to basic. Polysulfides are intermediate products formed through sulfate oxidation (Kotronarou and Hoffman, 1991). The most comm on polysulfide species are: tetrasulfide, and pentasulfide (O-Brien and Birkner, 1977). Sulfide: H2S, HS-, S2Sulfite: SO2, SO3 2Elemental Sulfur, S0 Sulfate: SO3, SO4 2Aerobic Bacteria Anaerobic Bacteria Anaerobic Bacteria Sulfur oxidizing Bacteria S + O2 SO2 O2 Sulfur oxidizing Bacteria

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8 Figure 2. Sulfate Species Distribution in Groundwater as Function of pH Regulations Pertaining to th e Control Hydrogen Sulfide Currently hydrogen sulfide in drinking wa ter is not regulated directly. However, it is regulated in the Safe Dr inking Water Act (SDWA) thr ough secondary standards based on odor with a maximum contaminant level of 3 threshold odor units. In 2003, the Florida Department of Environmental Protec tion (FDEP) issued a new rule under chapter 62-555.315(5) Control of Copper Pipe and Black Water. Under this rule, groundwater from new or altered wells that contains tota l sulfide levels above 0.3 mg/L cannot treated using only chlorine. FDEP treatment recomm endations related to the control of hydrogen sulfide as a function of concentration and pH are shown in Table 2. This rule does not obligate the utilities to appl y the treatment solution proposed if they can demonstrate similar efficacy using an alternative treatment.

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9Table 2. FDEP Hydrogen Sulfide Treatment Recommendations Treatment Sulfide concentration range, mg/L pH Maximum Efficiency Chlorination < 0.3 Independent 100% Conventional Aeration 0.3 0.6 7.2 40 – 50% Conventional Aeration plus pH adjustment 0.3 0.6 > 7.2 40 – 50% Forced Draft aeration 0.6 – 3 7.2 90% Forced Draft aeration plus pH adjustment 0.6 – 3 7.2 90% Packed tower plus pH adjustment > 3.0 Independent > 90% Adapted from FDEP Chapter 62-555.315(5) Treatment Options for Control Hydrogen Sulfide Treatment options to cont rol hydrogen sulfide can be divided into two groups: conversion and removal options. Conversion t echnologies are based on transformation of the sulfide into another more oxidized form through the use of chemicals or biological reactions. Removals options consist of the re moval of sulfide as a gas, solid, or liquid (Levine et al. 2005). Those include aera tion (Dell’Orco, et al. 1998, Wells, 1954), microfiltration (Thompson et al. 1995), a nd anion exchange (Levine et al. 2005, Thompson and McGavey, 1953). It is possible to use a combination of those options i.e., aeration followed by chlorination without filtra tion, which is used widely in the US (Lyn and Taylor 1991) or oxidation followed by f iltration and chlorination (Levine et al, 2004).

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10 Conversion Options Conversion reactions result in the transformation of the hydrogen sulfide to a more oxidized form of sulfur. These oxidi zed species include sulfate and elemental sulfur. The effect of the oxidizer can be explained using a predominance area diagram for sulfur species (Figure 3). The addition of the oxidizing agent increases the oxidation potential and promotes the formation of elemen tal sulfur or sulfate. Chemical oxidation is one of the most common options to control H2S. The main advantages for chemical oxidation are minimal space requirements, in -line operating, and oxidants can serve as disinfectants. Typical oxidants include chlorine, o xygen, hydrogen peroxide, ozone, ferrate, and potassium permanganate. Pr oducts depend on pH, reaction rates, and chemical equilibrium (Levine et al. 2005, Lyn and Taylor 1991, Dohnalek and FitzPatrick 1983). -10 -5 0 5 10 15 20 246810 pHH2S SO4 2HS S H2O O2H2 Oxidant additon pH Control Oxida addition Elemental Sulur Figure 3. Sulfur Species Predominance Area as Function of Oxidation Potential (pE) and pH pE

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11 Chlorine Oxidation Chlorine can oxidize hydrogen sulfide and act as a disinfectant. Black and Goodson (1952) described the stoichiometric equation that represents the reaction between hydrogen sulfide and chlorine (Equations 2 and 3) The chemical reaction is highly dependant on pH, and temperature. Fr om the stoichiometric reaction, conversion of 1 mg of H2S to elemental sulfur requires 2.08 mg Cl2 whereas 8.33 mg of Cl2 are needed to form sulfate. The initial reaction between chlorine and sulfides is fast and typically the chemical equilibrium is reached within 5 minutes (Cadena and Peters 1988). However, complete transformation to sulfate or elemental sulfur re quires higher chlorine doses because of the possible chlorine reac tions with other compounds present in the water. Concerns about using chlorine in clude the potential to form disinfection byproducts (Dohnalek and FitzPatric, 1983) w ith the additional pot ential for sulfur turbidity formation (Lyn and Taylor, 1991). H2S + Cl2 S0 + 2HCL pH<8 (Equation 2) H2S + 4H2O + 4Cl2 H2SO4 + 8HCL pH>8 (Equation 3) Levine et al. (2005) observed an importa nt increment in the turbidity once the chlorine demand was satisfied. For pH levels between 7.5 and 8.5 the turbidity increased with contact time. Sulfide turb idity is produced at all pH hi gher than 3.8, this turbidity can not be removed with an increment in su rface loading rates, decrease in chlorine dosages, or increments in the contact time (L yn and Taylor, 1991). In waters with high hydrogen sulfide concentrati ons (20 – 30 ppm) treated using aeration followed by chlorination “milky” water is observed (F oxworthy and Gray 1958, and Schiller 1955).

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12 Hydrogen Peroxide Hydrogen peroxide is a power ful oxidant. Its oxidation potential is 1.78 V. The oxidation of hydrogen sulfide reaction is dependa nt on pH. If the pH is below 8, the final product of the reaction of hydrogen peroxide and hydrogen sulfide is elemental sulfur, whereas, at pH levels above 8 in basic so lution the product is su lfate (Dohnalek and FitzPatric, 1983). The effect of the add ition of hydrogen peroxide can be understood using Figure 3. The stoichiometric reactions th at describe hydrogen pe roxide oxidation of hydrogen sulfide are shown in Equations 4 and 5. H2S + H2O2 S0 + 2H2O pH< 8 (Equation 4) H2S + 4H2O2 SO4 2+ 4H2O + H+ pH>8 (Equation 5) According to Hoffman (1977) the optimal dosage of hydrogen peroxide is equal to two times the hydrogen sulfide concentr ation. The reason for this excess is to compensate for hydrogen peroxide decomposition if the pH< 8. The main advantages of the use of hydrogen peroxide are: the end pr oducts of the reaction are oxygen and water, its liquid nature, and it does not produce corr osion or toxic fumes. According to Cadena and Roberts (1988), the reaction between hydroge n peroxide and sulfides is slow (0.120 1/min) in comparison with chlorine or pot assium permanganate which provides an extended sulfide protection. In a study conducted using hydr ogen peroxide and chlorine in a two stage process, Levine et al. (2005) found 50 to 70% of the hydrogen sulfid e was oxidized within three minutes at ambient temperatures and pH levels from 7.5 to 8.3. Excess hydrogen peroxide was consumed by the chorine in th e second stage of the process and generation of turbidity decreased with increasing pH.

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13 Ozone Ozone is a strong oxidant with an oxida tion potential equal to 2.07 V. It is between the strongest oxidizer (hydroxyl radical) and hydrogen peroxide. It is widely used as disinfectant and can aid in the reduction of taste and odors problems. The stoichiometric reactions that describe ozone oxidation of hydrogen sulfide are shown in Equations 6 and 7. The ozone demand ma y be higher than the stoichiometric requirements because of the presence of other reduced compounds (Crittenden et al. 2005). The major advantage of the ozone is th at no residual products are associated with its use (Dohnalek and FitzPatrick, 1983). H2S + O3 S0 + O2 + H2O (Equation 6) S2+ 4O3 + 4H2O SO4 2+ 4O2 (Equation 7) Potassium Permanganate According to stoichiometric reactions, the dosages of potassium permanganate necessary to oxidize hydrogen su lfide are 3.09 and 12.39 mg/ mg H2S and to form elemental sulfur or sulfate respectively. Over dose imparts pink color to the water and can cause formation of black deposits in th e water distribution systems and in-house plumbing fixtures. Stoichiometric reactions between potassium permanganate and the hydrogen sulfide are given in Equations 8 and 9. 3H2S + 2KMnO4 3S0 + 2H2O + 2MnO2 + 2KOH pH<7.5 (Equation 8) 3H2S + 8KMnO4 8MnO2 + 3K2SO4 + 2H2O + 2KOH pH>7.5 (Equation 9)

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14 Removal Options Removal options are able to withdraw hydrogen sulfid e from the aqueous phase using physical and/or chemical reactions. It is possible to rem ove hydrogen sulfide in gaseous, liquid, or solid from the water matrix. Aeration and anion exchange are discussed in this section. Aeration Aeration is a common option used to treat groundwater sources that contain hydrogen sulfide. It is also used to rem ove other volatile constituents such as carbon dioxide, organics, and methane (Crittenden et al. 2005 and Schiller 1955). Aeration also serves to oxidize reduced iron. In addition to volatilization, dissolved oxygen can act to oxidize hydrogen sulfide or serve as an elec tron acceptor for microbial sulfur oxidation (Levine, 2005). As a result of aeration, nui sance odors are generated and scrubbers may be needed if aeration towers are near to residential neighborhoods (Thompson et al. 1995 and Jewell 2002). In general, aerators promote the growth of microbial colonies, and may result in increased turbidity (Dell’Orco et al. 1998). The efficiency of hydrogen sulfide removal through ae ration depends on the pH of the influent (Figure 1). N onionized hydrogen sulfide is pres ent in high percentages in groundwater sources with a pH less than 7. The ionized sulfide fracti on is not susceptible to removal using aeration. To increase the ove rall process efficiency the pH should be reduced to 6 (Dell’Orco et al 1998, Thom pson et al. 1995). Duranceau et al. 1999 found an increment in the efficiency from 70% to 95% in packed towers when the pH was decreased to 6. However, high removals of hydrogen sulfide can be achieved without pH reduction, because of the presence of sulfide oxi dizing bacteria in the aerators (Jewell, 2002). A problem associated with the presence of these microbial populations is turbidity

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15 formation that may decrease disinfection eff ectiveness (Dell’Orco et al 1998). Other important factors that impact the aeration efficiency include: temperature, air-water ratio, and the type of aerator (Levine et al. 2005). According to the method of gas introduction, aeration systems can be divided into: spray aerators, na tural convection, induced draft, a nd forced draft. Typical aerators used to control hydrogen sulfide are compared in Table 3. Table 3. Main Characteristics of Aera tors Using to Control Hydrogen Sulfide Type Method of gas introduction Hydraulic head required, ft Air to water ratio Hydraulic loading Practical efficiency* Problems Spray aerator Natural convection 5 – 25 Large installations, weather Spray Tower Forced draft 5 – 25 50 -70% Packed Tower Forced draft 10 – 40 80-120 to 1 25 – 30 gpm/ft2 50 – 90% Multiple Tray Natural or forced daft 5 -10 30–80 to 1 7 – 15 gpm/ft2 30 – 50% Ventilation Conventional aerator with forced draft 12-16 to 1 7 – 15 gpm/ft2 50 – 70% Adapted from Levine et al. 2005 and Crittenden et al. 2005 Efficiency is affected by pH and temperature Usually chlorine is used to co mplete the oxidation of sulfides and to disinfect the water. According to Sheppard et al. 1948, aerat ion in combination with pH adjustment is not able to achieve 100% removal.

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16 Possible problem associated with the use of aerators is th e depressurization of the system that requires re-pressurization to re-i ntroduce water into th e system. The use of aeration could be a problem in places where th e well extraction rates are not constant and limited space is available to accommodate the equipment (Levine, 2005). Anion Exchange Ion exchange technology is base d on the reversible intercha nge of ions with other ions of similar charge from a solid phase (resin) to aqueous phase (Crittenden et al. 2005). Ion exchange resins can be divided into cationic and anionic resins. Cationic resins are subdivided into strong acid or weak acid, while ani onic resins are classified as either strong base or weak base. Those di visions are based on th e functional group linked to the resin backbone (Critte nden et al. 2005). In the case of strong base resin, these can be divided into two types: t ype I and type II. Type I has three methyl groups, and type II has two methyl groups and one ethanol group. A comparison of resin characteristics is shown in table 4. The exhaustion point of the resin is reached when the influent is in equilibrium with the complete bed (Liang et al. 1999). An electron micrograph of a surface of a strong base re sin is shown in Figure 4. Table 4. Anionic and Cationic Resin Characteristics Resin RegenerantpK Capacity, meq/mL Strong-base anion, type I Clor OH> 13 1 – 1.4 Strong-base anion, type II Clor OH> 13 2 – 2.5 Weak-base anion OH5.7 – 7.32 – 3 Strong-acid cation H+ or Na+ <0 1.7 – 2.1 Weak-acid cation H+ 4 – 5 4 – 4.5 Adapted from Crittenden et al. 2005

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17 Figure 4. Surface Strong Base Resin Micrographs The main advantages of the use of anion exchange are: operation with demand of the system, short contact time, zero level of c ontaminant is possible, variety of resins, and the reuse of regenerant (Clifford, 1999). The ma in disadvantages are: high concentrations of sulfate that can inte rfere with the removal of the targ et anion, and a brine waste stream is generated (Clifford 1999, Bae et al. 2002, Li ang et al. 1999, and Korngold et al. 2001). The most important characteristics of anion exchange resins are: exchange capacity, selectivity or preferen ce, swelling, moisture content, density, and particle size. Those characteristics are reflected in the resi n performance. Exchange capacity is defined as the total number of ions per resin volume. It can be e xpressed as total capacity or effective or operating capacity. The total ca pacity is defined in terms of the total exchangeable counter ions. Anion exchange resins do not exchange di fferent ions at the same rate. According to Waxhiski and Etzel (1997), the preference of the resin for certain anions depends on: the ion valence and atomic weight. The selectiv ity of anions for strong base resins are: PO4 3> SO4 2> HAsO4 2> NO3 > Cl(Crittenden et al. 2005 and Ghurye et al. 1999). This means that sulfate is preferred over the majority of anions listed. However, some resins do not follow the selectiv ity sequence (Liang et al. 1999).

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18 The particle size of the resin is a very important parameter because it influences the available surface, the kinetics and hydr aulic of the system. The inverse of the diameter is directly proportional to the rate of exchange. The particle size range varies from 1.2 to 0.04 mm. Higher head loss is associat ed with small particles. It makes more difficult pass the water through the bed (Waxhiski and Etzel 1997). After breakthrough occurs, regeneration of the resin is required. Regeneration consists of the following steps: backwash, brining, and rinse (slow and fast). The purpose of the backwash is to remove all suspende d material retained during the operation and reclassify the resin in the column through the media expansion, which is between 50 and 70%. The majority of the problems in ion exch angers are associated with an insufficient backwash (Wachinski and Etzel 1997). The average duration of the backwash ranges between 5 and 15 minutes. The purpose of the br ining process is to allow the interchange of ions that accumulate in the resin duri ng the normal operation and the ions in the aqueous phase. Currently the main anion exchange applic ations include: arseni c (Korngold et al. 2001, Kim and Bejamin 2004, and Ghurye et al. 1999), nitrate (Liang et al. 1999, Namasivayam and Hll 2005, and Bae et al. 200 2), and organics (Fetting 1999, Kim and Symons 1991, and Bolto et al. 2002). Other a pplications include the removal of cadmium (Zhao, et al. 2002), reactive dyes (Karcher et al. 2002), and hydrogen sulfide (Thompson and McGravey 1953 and Levine et al. 2005). The application of anion exch ange technology for the removal of Natural Organic Matter (NOM) has shown very impressive results. According to Feting (1999) the percentage of non removable NOM ranges between 10-40%, and it out performs the results obtained from activated carbon system s (Afcharian et al 1997). Kim and Symons (1991) studied the removal of trihalometha ne (THM) precursors using anion exchange technology. They found that the fraction with apparent molecular weigh less than 0.5 produced most of the THMs in presence of ch lorine. At the same time, the removal of

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19 this fraction using anion exchange range d from 20% to 25% after the sulfate breakthrough. As a consequence they recommended the measurements of the sulfide to determine its breakthrough. Pilot test studies allow the evaluation and compare resin performance in terms of capacity and regeneration. It is possible desi gn full scale systems if the loading rate and empty contact time at the same. (Crittenden et al. 2005). This type of test is able to answer the majority of the design questions in a fast and inexpensive way (Wachinski and Etzel, 1997). All technologies options presented in this section are able to control the presence of hydrogen sulfide from groundwater sources. However, comparative advantages among the options in terms of water quality, current regulations, practical is sues, cost, and size constraints impacts the selection of the right alternative.

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20 Removal of Hydrogen Sulfi de from Groundwater Using Packed-Bed Anion Exchange Technology Camilo Romero Cotrino; Audrey D. Levine University of South Florida Department of Civil and Environmental Engineering 4202 East Fowler Ave.; Tampa, FL 33620 cromeroc@mail.usf.edu; levine@eng.usf.edu Abstract: The presence of hydroge n sulfide in potable water ca n result in taste, odor, and corrosion problems. Typical approaches for controlling hydrogen sulfide include oxidation and aeration. The effectiveness of these treatment options depends on the concentration of hydrogen sulfide, and the pH The use of packed bed anion exchange allows for removal of the anionic forms of hydrogen sulfide and has the added advantage of controlling other anionic constituents in water such as organics, sulfates, and particulate matter. The efficacy of using a packed-bed anion exchanger for the treatment of groundwater was evaluated in this study. Pilot scale test s were conducted at four well sites in westcentral Florida over a four month period. H ydrogen sulfide concentrations among the wells varied from 1 to 2.5 mg/L as S2-. Sulfate concentrations varied from 1 to 40 mg/L and total organic carbon (TOC) varied from 1 to 3 mg/L. The capacity of the anion exchange system for removal of sulfide was evaluated. Anion exchange is effective for the removal of hydrogen sulfide a nd other anions from groundwater.

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21 Keywords: Hydrogen sulfide; anion exchange r; sulfate; TOC; groundwater treatment; removal. Introduction The presence of hydrogen sulfide in groundwater results in undesirable characteristics including an offensive odor metal corrosion, and high chlorine demand. Control of hydrogen sulfide is typically accomplished by a combination of oxidation and/or aeration (Sammons 1959, Sheppard and von Lossberg 1948, Lyn and Taylor 1991, and Dell’Orco et al. 1998). Microfiltration (T hompson et al., 1995), biological oxidation, and anion exchange (Levine et al., 2005) are possible tr eatment alternatives for controlling hydrogen sulfide. In the 1950’s, anion exchan ge technology for the removal of hydrogen sulfide was proposed (Thompson and McGarvey, 1953). However, limited information on the use of anion exchange has been reported. The objectives of this pa per are: evaluate the effectiveness of bed-packed anion exchange for removal of hydrogen sulfide, and to identify factors that influence resin capaci ty for the removal of hydrogen sulfide from groundwater. Background The possible treatment technology to cont rol the presence of hydrogen sulfide in groundwater sources should count the current re gulation and if it is possible it should be able to anticipate its possible changes in th e future. At the same time it is important to

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22 recognize the limiting factors that affect the performance of each technology. In this sections a review of the current regulation, factors that influence treatment options and anion exchange technology are discussed. Regulations Hydrogen sulfide is not di rectly regulated under the Safe Drinking Water Act. However, odor and taste are the secondary stan dards that indirectly control the presence of hydrogen sulfide in water. Additionally, the promulgation of the Stage 2 Disinfectant and Disinfection Byproducts rule (USEPA, 2006) will have an indirect impact on the control of hydrogen sulfide. Th e possible impact of the stag e 2 rule is based on the cooccurrence of the hydrogen sulfide and orga nics in groundwater sources. Although the stage 2 does not decrease the maximum contam inants levels, it became stricter in sampling. Now sampling points of a system ar e considering as indi vidual points instead systemwide. It may limit the use of chlorine as oxidizer to control hydrogen sulfide in presence of organic matter in groundwater. In addition, the Florida Depart ment of Environmental Pr otection (FDEP) issued a new rule under chapter 62-555.315( 5) in 2003 concerning the cont rol of total sulfide in groundwater sources. Recommendations about th e possible treatment options are based on the pH and the total sulfide concentration (Table 5).

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23Table 5. Possible Treatments Options to Co ntrol the Presence of Hydrogen Sulfide (FDEP chapter 62-555.315(5)) Treatment Sulfide concentration range, mg/L pH Maximum Efficiency Chlorination < 0.3 Independent 100% Conventional Aeration 0.3 0.6 7.2 40 – 50% Conventional Aeration plus pH adjustment 0.3 0.6 > 7.2 40 – 50% Forced Draft aeration 0.6 – 3 7.2 90% Forced Draft aeration plus pH adjustment 0.6 – 3 7.2 90% Packed tower plus pH adjustment > 3.0 Independent > 90% Adapted from FDEP Chapter 62-555.315(5) Influencing Factors on Treatment Options Treatment options for the control of hydrogen sulfide can be divided into removal and conversion options. Removal options consis t of the withdraw the dissolved hydrogen sulfide from the aqueous phase using phys ical and chemical reactions. Conversion options transform the hydrogen sulfide into elem ental sulfur or sulf ate through the use of chemical oxidizers and/or biological activ ity. The most common treatment technologies and the factors that influence the efficiency for each type of treatment are summarized in Table 6.

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24Table 6. Treatment Options and Influencing Efficiency Factors Treatment option Influencing factors Removal Aeration pH, temperature, air flowrates, and air to water ratio Anion Exchange pH, temperature, resin properties, competing anions Conversion Chemical oxidation pH, temperature, chemical dosage, reaction time, oxidant demand Biological sulfide oxidation pH, temperatur e, dissolved oxygen, reactio n time, microbial activity Conversion and removal Oxidation and filtration Particle size, turbidity, filtration Chemical precipitation pH, temperature, chemical dose, particle size, filtration parameters The most important factor that affects the control of hydr ogen sulfide is the sulfur species distribution as a func tion of the pH which is show n in Figure 5. The only portion of the sulfur species susceptible to rem oval by aeration is non-i onized hydrogen sulfide which is abundant at pH < 6. To increase the efficiency of the aeration process, a decrease in the pH to 6 is required.

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25 0 25 50 75 100 5 678 9 Groundwater pHMaximum process efficiency, percen t Anion Exchange Aeration Figure 5. pH Impacts in the Aeration and Anion Exchange Technologies Anion Exchange The major applications of th e anion exchange for drinking water are: removal of arsenic, nitrate, and organics (Korngold et al 2001, Ghurye et al. 1999, Jaeshim and Benjamin 2004, Liang et al. 1999, and Bolto et al. 2002). Other applications include removal of cadmium (Zhao et al. 2002), reactive dyes (Karcher et al. 2002), and hydrogen sulfide (Thompson and McGarvey, 1953). Ion exchange resins consist of a crosslinked polymer with functional groups attached to the resin backbone. For anion exchange those functional groups are: quaternary amine and tertiary amine for Str ong Base Anion (SBA) and Weak Base Anion

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26 (WBA) respectively. It is possi ble to replace of one methyl group to an ethanol group in quaternary amine in the SBA resin. This type of SBA resin is cal led Type II, and the purpose of this replacement is the reduction of the resin’s affinity for the hydroxide ions. (Crittenden et al. 2005). Type I cons erves the original amine structure. It is possible to appl y anion exchange technology for the removal of hydrogen sulfide since the anionic form of the sulf ides is the most common form at typical groundwater pH. Ionized sulfid e range is between 50% and more than 80% for a pH between 7 and 8 (Figure 6). In addition, anion exchange has provided excellent results in the removal of other constituents such as color and organic matter. According to Fettig (1999) and Liang (1999), the range of natural organic matter removal for ion exchange is a range between 60 and 90 percent. 0% 20% 40% 60% 80% 100% 02468101214 pH H2S Polysulfides Sn -2 HS-S-2 Figure 6. Theoretic Sulfur Species Distribution in Function of the Water pH

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27 The removal of the dissolved an ions is affected by severa l factors such as initial anionic concentration and SBA resin preference (Liang, et al. 2005). According to Crittenden et al. (2005) and Liang et al. (1999), the vale nce, atomic weight, and molecular radii are the most important charact eristics that define th e preference of the Strong Base Anion resin for so me anions. The selectivity co efficient is equal to the equilibrium constant of the reversible bina ry stoichiometric reaction between the ions exchangeable in the resin and aqueous phase (Equations 10 and 11) (Ghurye et al. 1999). Selectivity coefficients of the different ani ons for SBA resin are listed in Table 7. The resin preference is proportional to the value of selectivity. A B B A (Equation 10) B A A B B AC q C q K (Equation 11) Where: B AK= Selectivity coefficient for ion B exchanging with ion A onto resin Bq = Resin-phase concentr ation of ion B (eq/L) AC= Aqueous-phase concentration of ion A (eq/L) Aq = Resin-phase concentr ation of ion A (eq/L) BC= Aqueous-phase concentration of ion B (eq/L)

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28Table 7. SBA Resin Selectivity Anion Selectivity HCO3 0.4 CH3COO0.2 SO4 20.15 F0.1 OH0.06 CO3 20.03 HPO4 20.01 Adapted from Crittenden et al. (2005) Complete mixed reactors and packed bed are the two t ypes of applicable anion exchange configuration. However, there are some concerns about the use of complete mixed reactors for groundwater applications. The main disadvantages of the complete mixed reactors are: continued waste generati on, space constraints, re-pressurization, and the need for possible filtration. In contrast packedbed does not have any of those problems. The most important advantage of th e packed-bed columns is that it decreases the net of sulfur species in the water matr ix. A re-equilibration be tween non-ionized and ionized sulfide is promoted af ter the first sulfide exchange. This cycle is continuous and allows for the rapid decrease of the hydrogen sulfide in the effluent. Materials and Methods During this project, pilot columns with a SBA resin were using to evaluate the effectiveness of bed-packed anion exchange in the removal of hydrogen sulfide. In this section the resin characteristics, pilot test and source water quality is provided.

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29 Strong Base Anion Resin The resin used is a comm ercial macrosporous strong base anion exchange (Tulsion A-72 MP (Cl-)). A summary of the main resin characteristics is presented in Table 8. Table 8. Tulson A-72 MP Resin Characteristics Parameter Characteristic or Value Matrix Structure Cross linked polystyrene Physical form Moist spherical beads Particle size 0.3 to 1.2 mm Moisture (approx.) 58% Solubility Insoluble in all common solvents Backwash settled density 42 to 45 lbs/ft3 (670 to 720 g/l) Temperature stability (max) 195 F (90C) pH range 0 to 14 Ionic form Chloride Functional group Quaternary ammonium Type I Total exchange capacity 1.0 meq/Ml Swelling (approx.) Clto OH21% Adapted from Tulson A-72 MP Brochure Pilot Scale Test Pilot scale tests were conducted using plexi-glass packed-bed columns (2 inch diameter) designed to accommodate 0.065 ft3 of resin with a beddepth of 3 ft and a freeboard of 18 inches (Figure 7). The pilo t system was operated at empty bed contact

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30 time (EBCT) between 0.07 and 0.27 minutes, su rface loading rate equal to 6 gpm/ft2, Bed Volume (BV) equal to 0.486 gallons, and a volumetric loading of 2.0 gpm/ft3. Figure 7. Anion Exchange Column Photographs. a) Control Panel Allows the Operation of all Anion Exchange Cycles; b) Anion Exchange Overall View Anion exchange columns were operated w ith or without air between 2 and 8 gph and at pressures ranging from 12 to 15 psi. The columns were operated in consort with well pumps which turn on in response to pres sure demand within the distribution system. The connection between the well pump and the AE column was made using a ” garden hose. The capacity of the resin was tested with the volume of untreated water that the resin was able to treat be fore sulfide breakthrough. Untreated water and the AE effluent were monitored regularly. The tests conducted and method detection limits are give n in Table 9. All sample containers were submerged in nitric acid bath at 1% for at least 24 hours, rinsed with Nanopure™ water and then sampled. Hydrogen sulfide measur ements were conducted using a flowing sample device with a submerged sample port. Tests were conducted di rectly in the field (pH, conductivity, temperature, hydrogen sulfide, dissolved oxygen, chlorine demand, a b Influent Effluent

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31 and oxidation reduction potential) and at the University of South Florida (USF) environmental engineering laboratory (sulfa te, chloride, alkalinity, UV-254 absorbance, and Total Organic Carbon (TOC)). Glass bottles were used to transport samples for TOC and UV-254 absorbance tests. Other samples we re transported in pl astic bottles to the laboratory. A summary of water quality test is presented in Table 5. In addition samples for the Scanning Electron Microscopy (S EM) and Energy Dispersive Spectroscopy (EDS) analysis were taken. The samples were preserved in a 2.5% glutaraldehyde solution for a minimum of 24 hours. Particul ate matter was concentrated by filtration through a 47 mm nylon filter with a pore size of 0.1 m. Samples were dehydrated using a graded series of ethanol (30%, 50%, 70%, 95%, and 100 %). Finally, samples were decanted off and dried overnight at 50C. A chlorine demand test was also conducted. This test can be used as an indirect measurement of oxidizing material availa ble in the water source (Standard Methods, 1998). The test was conducted in all wells on tw o different days. The contact time used to carry out this test wa s 30 minutes. An initial chlorine concentration added to the raw water was 30 mg/L and 10 mg/L as Cl2 to the anion exchanger effluent.

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32Table 9. Summary of the Analytical Methods Used for Water Analysis Test Field or Laboratory Method Reference Number Detection Limit Hydrogen Sulfide Field 4500-S-2 D Methylene Blue Method; HACH Portable Spectrophotometer DR/2400 0.1 mg/L as S Sulfate Lab-Field 4500 SO4 -2E. Turbidimetric Method; HACH Spectrophotometer DR/4000 0.1 mg/L as SO4 2Chloride Lab 4500 Cl Argentometric titration 1 mg/L Total Organic Carbon Lab 5310C Persulfate-Ultraviolet Oxidation Method; Sievers 800 TOC analayzer 0.05 mg/L pH Field HACH Platinum pH Electrode, Model 51910 HACH Portable Multiparameter Meter Sension 156 0.01 pH units Temperature Field HACH Platinum pH Electrode, Model 51910 HACH Portable Multiparameter Meter Sension 156 0.01 C Conductivity Field HACH Conductivity Probe, Model 51975-03 20 S/cm Dissolved Oxygen Field 4500O G. Membrane Electrode Method. WTW Oxi 3000 0.01 mg/L Oxidation Reduction Potential Field 2580 B. Oxidation-Reduction Pote ncial Measurement in Clean water; HACH Pocket Pal ™ ORP 1 mV Alkalinity Lab 2320B Tritation/Bromocresol green methyl red 20 mg/L as CaCO3 Total Chlorine Field 4500-Cl G Colorimetric Method; HACH Spectrophotometer DR/4000 0.01 mg/L as Cl2 Turbidity Field 2130B Nephelometric Turbidity; HACH Turbidimeter 2100N 0.01 NTU UV-254 Absorbance Lab 5910 B. Ultraviolet Absoption Method; HACH Spectrophotometer DR/4000 0.001 cm-1 Once breakthrough of hydrogen sulfide in the effluent occurs regeneration of the column is required. Columns were regenerate d using a brine solution of 15% salt. The regeneration process consisted of six steps: Backwash, Drain Down, Brine, Drain Down,

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33 Slow Rinse, and Fast Rinse as defined in Ta ble 10. An extended contact time (more than 12 hours) between a SBA resin and the brine solution was allowed. Table 10. Regeneration Steps Step Duration (min) Flow rate (gph) Backwash 10 4 Drain down Variable Variable Brine exposures 720 or extended None Drain down Variable Variable Slow rinse 25 1.2 Fast rinse 10 8 Source Water Quality A summary of water quality for raw water from four wells is given in Table 11. The values in this table correspond to the averages obtained during the summer-fall of 2005 at four well sites.

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34Table 11. Overview of Variable Tested in the Project Well A Average (Range) B Average (Range) C Average (Range) D Average (Range) Anions Sulfur Species Sulfide (mg/L as S2-) 2.64 (2.033.23) 1.64 (1.34 – 2.45) 1.07 (0.82 – 1.51) 0.94 (0.56 – 1.23) Sulfate (mg/L as SO4 2-) 37.38 (26.0 – 49.7) 7.27 (UDL* – 18.6) 14.75 (0.7 79) 1.08 (UDL* – 3.2) Chloride (mg/L as Cl-) 14.67 (10.09-28.44) 14.67 (10.09 28.44) 24.47 (10.09 – 46.70) 14.62 (8.17 21.65) TOC (mg/L) 2.78 (1.5-6.87) 2.68 (1.73-3.46) 2.37 (1.49-2.61) 3.08 (2.79-3.35) UV-254 Absorbance (cm-1) 0.09 (0.03-0.13) 0.08 (0.07-0.14) 0.12 (0.04-0.12) 0.10 (0.04-0.13) Alkalinity (mg/L as CaCO3) 163.5 (100 – 250) 180.3 (100 260) 180 (120 – 190) 147.88 (30 – 250) Exchangeable characteristics Exchangeable Anions (meq/L)+ 5.56 4.59 3.88 3.99 H2S/ Exchangeable Anions+ (0.03-0.04) 0.02 0.02 0.01 Other Characteristics pH 7.39 (6.79 – 7.55) 7.35 (6.58 – 7.52) 7.38 (7.2 – 7.63) 7.44 (6.03 – 7.61) Temperature ( C) 23.70 (11.7 – 27.1) 23.4 (11.1 – 28.30) 24.9 (23.1 – 26.80) 24.21 (12 – 27.7) Conductivity ( S/cm) 463.71 (341 – 570) 427.33 (449 – 520) 384.6 (285 – 502) 377.48 (232 – 454) Turbidity (NTU) 0.32 (0.07-1.51) 0.6 (0.07-4.03) 0.53 (0.10-3.12) 0.24 (0.07-1.25) Cl2 demand (mg/L) 17.08 14.25 10.39 10.8 UDL, Under Detection Limits + Correspond to the averages of the runs Results In this section, an evaluation of the effectiveness of anion exchange in the removal of hydrogen sulfide, other important anions, a chlorine demand test, and the factor that influence the performance of the anion exchange are discussed.

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35 Hydrogen Sulfide and Other Anions Removal The treatment effectiven ess was evaluated based on the removal of hydrogen sulfide through the anion exchange. The br eakthrough concentration of hydrogen sulfide concentration was defined as a 0.5 mg/L as S2-. Results suggest a relationship between the initial concentra tion of hydrogen sulfide and the br eakthrough volume. The average BVs and the concentration of hydrogen sulfide in the influent for all four wells are shown in Figure 8. In comparison with well A th e increments in BV were 329%, 232%, and 385% for wells B, C, and D respectively. However, well C seems to be influencing by another factor that reduces its performan ce in comparison with well B. The difference between the BV obtained in wells B and C ma y be explained by the dissimilarity in sulfate concentration. In the case of well B the averag e concentration was 7.27 mg/L and 14.75 mg/L as SO4 2for well C. 0 100 200 300 400 500 ABCDBV0.00 0.50 1.00 1.50 2.00 2.50 3.00Hydrogen sulfide, mg/ L BV H2S, mg/L Figure 8. Comparison Between the Average BV and the H2S Concentration for Each Well

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36 Sulfate levels varied from 1 to over 30 mg/l as SO4 2on the well sites. Sulfate breakthrough did not occur in any of the te sts. The results of the sulfate removal correspond with expected results according to the resin selectivity. The sulfate removal was typically over 90% among the wells. During the study period the average initial TOC concentrations for the four wells varied between 2.3 to 3.1 mg/L. 80% of the TOC was removed by the anion exchange vessels. Average decreases in the chlorine de mand for wells A, B, C, and D were 81.1, 79.1, 76.6, and 81.3 percent respectively. The chlori ne demand of the influent water at ambient pH and the chlorine demand in the anion exchange effluent are shown in Figure 9. The anion exchange demand range from 2.0 to 3.23 mg/L. As expected the chlorine demand varies in function of hydrogen sulfide (Figure 10). 0 5 10 15 20 ABCDChlorine demand mg/L as Cl2 Raw water Anion exchange effluent Figure 9. Comparison Chlorine Demand in Ra w Water and Anion Exchange Effluent for Each Well

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37 y = 3.0119x + 9.2513 R2 = 0.8236 0 5 10 15 20 0.51.01.52.02.53.0 Hydrogen sulfide, mg/L as SChlorine demand mg/L as Cl2 Figure 10. Chlorine Demand as Function of Influent Hydrogen Sulfide Concentration Influencing Factors In addition to the water qua lity, the presence of air in the column, and the development of microbial colonies in th e resin influenced the performance. It was observed that resin cap acity increased when a sma ll amount of air was induced. Comparison between average runs in well A and B where the presence of air was observed or measured is shown in Figure 11. The increments in the number of BV were 155 % and 88 % for wells A and B respectively. These differences motivated two separated the results into thes e two groups. BV averages for a ll wells as a function of the combined affects of the hydroge n sulfide and sulfate is show n in Figure 12. The intercept with the BV axes was 354 to runs without air and 503 for runs with air. Increase in BV is equal to 42%. On the other hand, slopes di d not show significant difference between them. The P value equals to 0.92. These trends allow the creation of model to predict the treat volume before hydrogen sulfide breakthroug h is obtained. However, the application

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38 of this model is limiting the initial concen tration of sulfate or sulfide to very low concentrations. If only hydrogen sulfide is present the model becomes zero at concentrations equals to 26.47 and 20.05 mg/L as S2for runs with the presence of air and without it respectively. In th e case of sulfate th e maximum concentrations are 74.76 and 56.65 mg/L as SO4 2-. To create an applicable model to predict the performance of the resin under any circumstances is necessary th e use water with a sp read water quality characteristics. 0 100 200 300 400 500 600 ABBV NO AIR AIR Figure 11. Comparison Between the Average BV for Runs With Air and Without in Wells A and B

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39 y = -323.02x + 503.11 R2 = 0.768 y = -299.82x + 353.59 R2 = 0.9977 0 100 200 300 400 500 600 0.00.20.40.60.81.0 Hydrogen Sulfide + Sulfate, meq/LBV Air presence Air abscence Figure 12. Predictor BV Model Based on the Initial Hydrogen Sulfide and Sulfate Concentrations in meq/L for Run With and Without Air Since the TOC concentrations among the wells are similar, the relatively high impact that sulfate concentrations have on th e performance of the re sin i.e., well A, and based on the preference of the SBA resin it is possible that the phenomenon is drove by the sulfate. During the course of this study an incr eased capacity was observed in some wells in conjunction with the devel opment of a white layer on the top of the resin. Samples of resin and water were analyzed using Sca nning Electron Microscopy (SEM) coupled with Energy Dispersive Spectroscopy (EDS) (Fi gure 9). The presence of bacteria was observed. Further study is required to understa nd their possible role in the removal of sulfides from groundwater.

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40 Figure 13. Scanning Electron Micrographs from a), b), c) Resin From Well B, and d) Resin From Well A Discussion Packed-bed anion exchange has directly impact in the wate r quality, operational procedures and practical issues. As the main objective of this project, Anion exchange technology demonstrated an effective contro l of hydrogen sulfide fr om groundwater with no odors or noise production. Sulfur species have the ab ility of oxidation or reduction by chemical and/or biological reactions in the distribution systems and stor age tanks under the correct a b c d

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41 environment. It makes possible the re-appear ance of the hydrogen sulfide if the net mass of sulfur is no remove from the water matrix. While aeration and oxidation do have the potential to remove other sulfur species diffe rent from hydrogen sulfide, anion exchange eliminates the possibility of the reformati on of hydrogen sulfide removing other anionic sulfur species such a sulfate, and bisulfate. Because of the nature of the or ganic matter, it is susceptible to be removed using anion exchange technology. High removal percen tages have been found with use of anion exchange while the others alte rnatives do not have the abil ity of organic reduction. Anion exchange decreases the potential forma tion of DBPs with the removal of high percentages of TOC. Anions are responsible for a la rge part of the consumption of chlorine during the oxidation. The removal of these anions redu ces the chlorine demand. Reductions in the chlorine dosages impact directly the potenti al formation of DBPs. In addition, reductions in operational cost will be obtaine d by reducing the chlorine dosages. Usually aeration and disinfec tion are associated with the potential production of turbidity that is responsible of decrease di sinfection efficacy and cr eates aesthetic issues. The absence of turbidity formation and its abil ity to remove negativel y colloidal particles make highly competitive anion exchange technologies. As a consequence of the removal of turbidity the disinfection effectiveness may increase. Another substantial advantag e of the use of anion exchange technology is the elimination of chemicals additions. Anion ex change operates at ambient pH that makes unnecessary the addition of acids to decrease the pH to incr ease the efficiency of the system. As a consequence reduction in opera tional cost will be obtained. In addition, decreases the possible heath impacts on the ope rators in that they have less need to handle chemicals.

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42 Anion exchange technology elimin ates the necessity of re-pressure the treat water. This fact eliminates the possibility of cont amination during the air contact, storage, and contributes to the reduction of the operational cost. Small treatment plants can be located in resident ial areas. Consequently, concerns regarding the availability of land and the production of odors and noise become important issues. Packed-bed anion exchange does not require a larg e amount of space or produce odors or noise. Thus it is can be a particularly important technology where wellsites are located in close proximity of communities and space is limited. Conclusions Based on the data generated th rough this project, the fo llowing conclusions can be drawn: 1. Anion exchange technology is an e ffective technology for removing hydrogen sulfide from groundwater sources. 2. Resin capacity was related to the concentration of exchangeable anions. 3. Supplemental benefits of anion exchange include removal of TOC, sulfate, and reduction of the chlorine demand. 4. Initial concentrations of sulfate seem to have a big impact in the resin performance. 5. The introduction of air impacts the performa nce of the resin increments the treat volume before the hydrogen sulf ide breakthrough is reached.

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43 Acknowledgements This study was supported by Aloha Utilities, Inc. Tonka Equipment Company provided the pilot columns and resin. The assi stance of Aaron Robert s with the collection of the data is appreciated. Mike McDonald pr ovided us with valuable field support. The assistance of Mindy Decker, Erin McMaha n, Francis Eshun, and Mark Velasquez is appreciated.

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44 Comparison of Alternative Technologies for Control of Hy drogen Sulfide from Groundwater Sources Audrey D. Levine1, Camilo Romero Cotrino1, and Rochelle J. Minnis2 1Department of Civil and E nvironmental Engineering; University of South Florida. 4202 East Fowler Ave., Tampa, FL 33620 2 HDR Engineering, Inc. 2202 N. West Shore Blvd. Suite 250; Tampa, FL 33607 levine@eng.usf.edu; cromeroc@mail.usf. edu; rochelle.minnis@hdrinc.com Abstract: Control of hydrogen sulfide can be accomplished through removal technologies such as aeration or anion exchange or conve rsion technologies such as oxidation. All of these technologies are capable of contro lling hydrogen sulfide, however, there are differences among the technologies in terms of their impact on treated water quality. There are also operational differences that influence process selection. Pilot scale test were conducted to evaluate efficacy of the anion exchange technology and chemical oxidation for removal hydrogen sulfid e from groundwater. The effectiveness of aeration, anion exchange, and chemical oxidation was compared. For small scale systems, anion exchange was the most co mpetitive alternative to control hydrogen sulfide. Additional benefits from use of anion exchange include removal of other sulfur species reducing the eventual reformati on of hydrogen sulfid e, organic carbon compounds, and chlorine demand was reduced.

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45 Key works: Hydrogen sulfide; aeration; anion exchange; chemical oxidation; groundwater treatment. Introduction The technologies for controlling hydrogen sulfide in groundwater sources can be divided into two categories, removal and conversion. Treatment technologies can be designed to remove hydrogen sulfide through gas exchange, ion exchange. Conversion technologies capitalize on the fact that hydr ogen sulfide can be transformed from one oxidation state from another. This conversion can be carried out by bi ological activity or chemical reactions. Oxidation can be combined with filtration. In general, control of hydrogen sulfide is affected by: pH turbidity, temperature, and alkalinity. The distribution of different fo rms of sulfides in groundwater sources is highly dependant of the pH. At pH between 7 and 8 the concen tration of nonionized hydrogen sulfide ranges between 50 and 20%. pH also influence the kinetics of the chemical reactions. Turbidity can compromise the effectiveness of chemical oxidation with a possible increment in the oxidant demand. In addition, it can compromise the efficacy of the disinfection. Temperature is mainly related to r eaction rates during the chemical oxidation. The use of acid to decrease the pH during the aeration process could have an important impact in the alkalinity cap acity of the water source i.e., sulfuric acid (Duranceau, 1999). Aeration is able to volat ize the nonionized hydrogen sulf ide through exposure the water to air. Aeration by itself is not able to remove the ionized forms. The efficiency of the procedure is affected by the distribution of sulfide as a function of pH. Parallel to volatilization of hydrogen sulfide, oxygen is absorbed by the water. Aeration systems provide a good environment for developing of microbial populati ons (Dell’Orco, 1999)

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46 that can also transform resulting in increased tu rbidity in the aerator effluents. Inspite of these problems, aeration is one of the most common treatments to remove hydrogen sulfide. Alternative approaches have been proposed to remove hydrogen sulfide such as gas exchange or anion exchange. Anion exchan ge uses a strong base resin in a bed or completely mixed reactor. The resin is able to exchange chloride for the anionic target contaminant while a contact between wate r and resin is promoted. Once the resin capacity is exhausted regeneration with brine solution is required. Chemical oxidation is used to convert dissolved hydrogen sulfide to another more oxidized sulfur form (elemental sulfur or su lfate). This transformation is dictated by the type of oxidizer and the pH of the water. The most common oxidizers used to control the presence of hydrogen sulfide in groundwat er sources are: chlorine, oxygen, hydrogen peroxide, ozone, and potassium permanganate. The purpose of this paper is compared treatment options of hydrogen sulfide and the impact on some key water qua lity parameters of each technology. Background S ulfur transformations, general informa tion on regulatory issues, water quality parameters relevant for controlling sulfid es, aeration, anion exchange, and chemical oxidation are discussed in this section.

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47 Sulfur Transformations The dominant forms of sulf ur in the environment are controlled by biological, chemical, and geochemical reactions that resu lt in the cycling of su lfur between various oxidation states and complexation with organi c and inorganic constituents. The sulfur cycle is dynamic and the turnover rate for each stage is controlled by water quality and microbial characteristics. Sulfides are the main product of sulfate respiration by an aerobic bacteria and are also released by desulfuration of organic compounds. Sulfides can be converted to elemental sulfur or sulfate by biological or chemical oxidatio n. In addition to biological reactions mediated by microorganisms presen t in the environment, chemical oxidation reactions can convert sulfides to elemental sulf ur or sulfate. Oxidizing agents available in the environment include oxygen, iron, or manganese. Regulatory Framework for Control of Hydrogen Sulfide While the need for controll ing hydrogen sulfide in water systems has been widely recognized (Jacobs et al. 1998, Stumm 1960, Wells, 1954, White 1999 ), historically there have been relatively few re gulations that address treatme nt requirements. Under the requirements of the Safe Drinking Water Ac t (SDWA) hydrogen sulfide is indirectly regulated through the secondary drinking water standard for taste and odor. However, there are no monitoring requireme nts for hydrogen sulfide in e ither treated or untreated water. Tampa Bay Water, a wholesale prov ider of water in west-central Florida,

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48 developed a performance goal for their me mber governments of 0.1 mg/L for hydrogen sulfide in treated water. In 2003, the Florida Department of Environmental Protection (FDEP) implemented a new rule pertaining to hydrogen sulfide removal under Chapter 62555.315(5). This rule applies to the permitti ng process for new or altered wells in community water systems. Treatment recomme ndations are defined based on the level of total sulfide in the untreated water and th e ambient pH. Those recommendations include: chlorination, conventional aeration with and wi thout pH adjustment, forced draft aeration with and without pH adjustment, and forced dr aft aeration. The rule also allows utilities to use alternate treatment t echnologies as long as the treatment effectiveness is comparable to the treatment recommendations specified. Water Quality Variables of Importance for the Control of Hydrogen Sulfide The efficiency of the treatment systems options for control of hydrogen sulfide is influenced by several water quality variab les including pH, alkalin ity, temperature, and turbidity. The presence of ir on, manganese, organic carbon or other constituents that might impose an oxidant demand can also imp act process performanc e and treated water quality. From the perspective of hydroge n sulfide control, pH affects the degree to which the sulfide is ionized or noni onized. The technologies discuss in this paper that allow for removal of hydrogen sulfide are highly pH dependent. Aeration is only effective for removal of nonionized hydrogen sulfide. As sh own in Figure 4, at pH 7, about half of the sulfide is in the nonionized form, while at pH 5, almost all of the sulfide is nonionized (H2S). However, the oxygen introduced into the water can act to oxidize the sulfide to

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49 elemental sulfur or sulfate. Conversely, ani on exchange is targeted at removal of the ionized forms of sulfide, which increase with increasing pH. Anion exchange technology also removes other negatively charged consti tuents from water including sulfate, organic carbon, and negatively charged (anionic) partic ulate matter. Oxidation technologies are effective over the entire pH range, however the products of oxidation (elemental sulfur versus sulfate or polysulfi des) are impacted by pH. 0% 20% 40% 60% 80% 100% 02468101214 pH H2S Polysulfides Sn -2 HS-S-2 Figure 14. Theoretical Distribution of Hydrogen Sulfide and Polysulfides in Wter as a Function of pH Asuming Polysulfides are in Equilbrium With HS(Equilibrium constants from Morse et al. 1987, Stumm and Morgan 1996 ) The presence of turbid ity in untreated water ca n affect the performance efficiency of hydrogen sulfide control techno logies based on oxidation and filtration. The particles suspended in groundwater tend to be relatively small (< 10 m) and negatively charged. There is potential for groundwater particles to exert an oxidant demand impacting chemical dosage requirements. In addition, the presence of particles in the water can compromise the eff ectiveness of disinf ection by shielding

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50 microorganisms from the action of disi nfectant chemicals (e.g. chlorine and chloramines). It is important to consider the potential impacts of turbidity on the performance of treatment technologies for hydrogen sulf ide control. In general, oxidation technologies may be impacted by additional oxi dant demand associated with the presence of particles. The performance of anion exchange is not likely to be impacted by turbidity. However, it is interesting to note that, sinc e particles in water tend to be negatively charged, it is possible to achieve some particle removal through anion exchange systems. There are no particle removal mechanisms associated with the other treatment technologies evaluated for this project. Aeration The form of hydrogen sulfid e removed in stripping reactions is nonionized hydrogen sulfide (H2S). In addition to stripping r eactions, secondary reactions occur within aeration systems due to the introduction of dissolved oxygen. Oxidation reactions that occur in aeration systems include hydr ogen sulfide oxidation (to either elemental sulfur or sulfate), and iron and manganese oxidation to form oxidi zed precipitates. Microbiological growth can also occur with in aeration systems due to the warm, moist environment and the presence of oxygen and nutrients. Products of the secondary reactions include biofilms and deposits consisti ng of iron, manganese, and sulfur particles that can foul the internal surfaces of aerat ion systems and potentially introduce turbidity into the treated water. Sulfates and el emental sulfur formed through biological or chemical oxidation have the potential to re vert to hydrogen sulfide under the correct environment conditions.

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51 The overall efficiency of aer ation technologies depends on several factors including: the ratio of air to water, wa ter pH, temperature, and aerati on system design. Chemicals can be injected to reduce the pH (carbon dioxide or a mineral acid) prior to aeration. Anion Exchange Ion exchange technology is a treatment pr ocess that removes constituents from water that are charged (ions) by reversibly entrapping the ions on a solid surface or resin. Ions entrapped on the surface are exchanged w ith other ions. Typically, ion exchange technologies are designed to remove positivel y charged ions (cations) or negatively charged ions (anions). Resi ns have a finite capacity fo r exchanging ions and once the resin is saturated, it can be regenera ted and put back into service. Over the past ten years, spurred by increasingly stringent water quality requirements coupled with advances in re sin production, the use of anion exchange technology has been adopted by many water ut ilities to remove negatively charged constituents including nitrates, arsenic, organic compounds, and/or other anionic contaminants such as perchlorate. In mo st anion exchange systems used for drinking water applications, chloride is exchanged fo r anionic constituents in the water. An electron micrograph of the characteristics of one of the anion exchange resins tested in this project is shown in Figure 1. The resi n consists of macroporous spherical particles ranging in size from about 100 to 800 m. The majority of ion exchange reactions occur on the resin surface and the avai lable surface area impacts the ca pacity of the system for removing anions from water. There is some potential for surface adso rption to occur, but it is difficult to quantify thes e reactions (Crittenden et al 2005, Crepaldi et al. 2000, HDR 2005, Letterman et al. 1999, Owens 1995).

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52 Figure 15. Scanning Electron Micrograph of Anion Exchange Resin Used for Testing Sulfide Removal For removal of hydrogen sulfide from water, the use of anion exchange capitalizes on the fact that, under pH ranges typical of groundwater, the majority of the sulfides are in an anionic form (HS-, S-2 , polysulfides, thiosulfate, sulfite). There are a variety of anion exchange resins commercially available that have been used in water treatment applications and have been approved by the National Sanitation Foundation (NSF). Oxidation Technologies for Control Hydrogen Sulfide A summary of hydrogen sulfid e oxidation reactions is shown in Table 12. The most common oxidant used for groundwater tr eatment is chlorine. Other chemicals that are effective for oxidation of hydrogen sulfid e include ferrate, hydrogen peroxide, ozone, and potassium permanganate. For drinking water applications, ozone and potassium permanganate have been used at various loca tions. Hydrogen peroxide is widely used in

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53 industrial applications and is also used in some drinking water systems in conjunction with ozone or UV irradiation in advanced oxidation processes for oxidation of trace organics. Ferrate has been used in indus trial applications (Sharma et al. 1997). Table 12. Comparison of Stoichiometric Chemical Reactions for Oxidation of Hydrogen Sulfidea Oxidant Oxidation Reaction Dose, Mg/mg H2S Chlorine H2S + Cl2 So + 2HCl 2.08 H2S + 4H2O + 4 Cl2 H2SO4 + 8 HCl 8.33 Ferrate 4H2S + 3HfeO4 + 7H+ 3Fe+2 + S2O3 -2 + 2So + 9H2O 2.66 16H2S + 20HfeO4 + 10H2O 20Fe(OH)3 + 3H2S2 + SO3 -2 + 3S2O3 -2 + 3SO4 -2 + 6OH4.44 Hydrogen peroxide H2S + H2O2 So + 2H2O 1.03 HS+ 4H2O2 SO4 -2 +4H2O +H+ (pH>8) 4.11 Oxygen HS+ 2O2 SO4 -2 + H+ 1.88 2HS+ 2 O2 S2O3 -2 + H2O 0.94 H2S + 3/2O2 SO3 -2 + 2H+ 1.41 2H2S + O2 2So + 2H2O 0.47 Ozone H2S + O3 S0 + O2 + H2O S-2 + 4O3 + 4H2O SO4 -2 + 4O2 2.82 5.64 Potassium Permanganate 3H2S + 2KmnO4 3So + 2MnO2 2KOH + 2H2O 3.09 3S-2 + 8KmnO4 + 4H2O 8MnO2 + 3SO4 -2 +8KOH 12.39 aFrom Black and Goodson (1952), Cadena a nd Peters (1988), Chen and Morris 1972, Dohnalek et al.(1983), Hoffman et al. (1977), Morse et al. (1 987), Sharma et al. (1997), and Sullivan et al. (1988)

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54 Because sulfur can exist in se veral oxidation states, the final form of oxidized sulfur is dependent on an array of factors. A predominance area diagram for some sulfur species is shown in Figure 2. In predomin ance area diagrams, the dominant form of each constituent is identified for all combinations of oxidation potential (represented as pE) and pH (Benjamin 2002, Stumm and Morgan 199 6). It should be noted that these diagrams do not provide information on the re lative concentrations of each constituent, but rather provide insight into the species that are thermodynamically favored at equilibrium under specific pE and pH conditions As shown, elemental sulfur tends to be favored in a fairly narrow range of pH and oxidation potential. -10 -5 0 5 10 15 20 246810 pHH2S SO4 2HS S H2O O2H2 Oxidant additon pH Control Oxidant addition Elemental Sulur Figure 16. Predominance Area Diagram Showi ng the Theoretical Equilibrium Forms of Sulfur as a Function of Oxidation Potential (pE) and pH. Thermodynamic Constants from Stumm and Morgan 1999. (pE is Equal to the Log of the Equilibrium Constant Normalized to One Electron Transfer) The addition of oxidant chemi cals serves to increase th e oxidation potential (pE) of water, thus causing a vertical shift upw ards in Figure 16. The extent of increase pE

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55 depends on the type of chemical added, the dos e, and water quality constituents that may react with the oxidant reducing the net oxidation potenti al available for control of hydrogen sulfide. Different oxidant chemical s have different oxidation potentials. A comparison of the oxidation potential of chem icals appropriate for use in groundwater systems is shown in Figure 17. Figure 17. Comparison of Oxidation Potentials Associated With Oxidant Chemicals Used for Chemical Oxidation of Hydrogen Sulfide. The Oxidation Potential is Reported in Terms of Volts Per Single Electron Transfer Methodology This project involved wa ter quality testing of unt reated water and technology evaluation. Anion exchange and oxidation was c onducted at the treatment sites associated

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56 with each well. Water quality tests were either conducted in the field using field test kits or in the USF laboratory. Sampling Samples were collected of untreat ed water and following indi vidual stages of pilotscale tests. Special precautions were take n for the collection of samples for sulfide analysis. A sampling device modified from a graduated cylinder was used to prevent exposure of the sample to air and potential vol atilization. Water enters the device at the bottom of the sampler and overflows from th e top. Samples for sulfide analysis are collected from the submerged tube and anal yzed directly using field test methods (titration, methylene blue colorimetric test, or specific ion electrode). Field tests on all samples in cluded sulfide analysis, pH, temperature, alkalinity, and conductivity. Chlorinated water for the p ilot-scale tests was test ed in the field for total and free chlorine using the DPD met hod. Field analyses we re also conducted for turbidity, color, UV-254 absorbance, iron, sulfate, and chloride for some of the bench and pilot scale tests. For analyses other than su lfides, samples for field testing were collected in pre-cleaned glass or plastic containers that were pre-rinsed with each sample. Probes (pH, conductivity, and sulfide) were calib rated regularly. For spectrophotometric measurements of color and UV-254 absorbance, sa mples were syringe filtered in the field using a filter with a pore size of 0.2 m. Samp les for laboratory analysis were collected in pre-labeled containers. Glass containers were used for tota l organic carbon (TOC) samples, plastic containers were used for samples for metal and anion analysis. Samples were transported to the USF lab and stored at 4 oC until analysis.

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57 A summary of the water quality tests used in this project is given in Table 13. Field analyses were conducted at the well si te and laboratory analys es were conducted in the USF environmental engineering laboratory.

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58Table 13. Summary of Analytical Methods Used for Characterization of Water Samples from Pilot-Scale Testing Test Field or Laboratory Method Reference Number (Standard Methods); Instrument Detection Limit/sensitivity Alkalinity Field and Lab 2320 B Titration /Bromocresol green/ methyl red 20 mg/L as CaCO3 Chlorine, total and free Field 4500-Cl F DPD Colorimetric Method; Pocket Colorimeter II 0.01 mg/L as Cl2 Conductivity Field and Lab HACH Conductivity Probe; Model 51975-03 20 S/cm Hydrogen Sulfide Field 4500-S-2 D Methylene Blue Method; Hach Field Spectrophometer Dr/2400 0.1 mg/L as S Ph Field and lab HACH Platinum pH Electrode, Model 51910; HACH Portable Multiparameter Meter Sension 156 0.01 pH units Temperature Field HACH Platinum pH Electrode, Model 51910 0.01 o C Turbidity Field and Lab 2130B Nephelometric Turbidity 0.01 NTU Nitrogen Ammonia Lab HACH-8155 0.01 mg/L Nitrate Lab HACH-8192 0.1 mg/L Anions Chloride Field and Lab 4140 B. Capillary Electrophoresis with indirect UV detection; Beckman P/ACE 5000 CE or 4500 CL Argentometric titration 1 mg/L Sulfate Field and Lab 4140 B. Capillary Electrophoresis with indirect UV detection; Beckman P/ACE 5000 CE or 4500 SO4 turbidity method 1 mg/L Metals Calcium Lab 3111 Metals by Flame Atomic Absorption Spectrometry; Perkin Elmer Aanalyst 100 0.01 mg/L Magnesium Lab 3111 Metals by Flame Atomic Absorption Spectrometry; Perkin Elmer Aanalyst 100 0.01 mg/L Iron (total and dissolved) Lab 3111 Metals by Flame Atomic Absorption Spectrometry; Perkin Elmer Aanalyst 100 0.01 mg/L Manganese Lab 3111 Metals by Flame Atomic Absorption Spectrometry; Perkin Elmer Aanalyst 100 0.01 mg/L Copper (total) Lab 3111 Metals by Flame Atomic Absorption Spectrometry; Perkin Elmer Aanalyst 100 0.01 mg/L Total Organic Carbon Lab 5310C Persulfate-Ultraviolet Oxidation Method; Sievers TOC analyzer 0.05 mg/L Particle characterization Lab Electron Microscopy/ Energy Dispersive Spectroscopy 0.5% (5000 ppm), 1 nm spot size

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59 Pilot-Scale Test Pilot scale tests were conduc ted using a pilot-test tr ailer constructed by Aloha Utilities for this project. The pilot system was designed to accommodate flowrates up to 2 gpm. The pilot plant consisted of an infl ow connection, chemical feed ports, treatment equipment, and sample ports. Clear plastic pipe s (2 inch diameter) were used to convey water through the system a nd provide for observation of air leakage, and turbidity formation. The hydraulic residence time of the system was 25 minutes at 1 gpm. The treatment units that were installed in the pi lot plant included two anion exchange tanks, a UV reactor, and a pipeline reactor for in-p ipe chemical treatment. The UV unit from Trojan was operated at a flowrate of 1 gpm (model 02AM15, 3 amps, 30 mJ/cm2 @95% UV transmittance). Bypass lines were installe d to allow for bypass of anion exchange, UV, or chemical feeds. Chemical feed por ts and pumps were located immediately after the water intake and at four downstream loca tions. In-line mixers were installed at the chemical injection ports to ensure adequate chemical di spersion. Sampling ports were located upstream and downstream of each treatme nt step. A photograph of the pilot plant is shown in Figure 18.

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60 Figure 18. Photograph of Inside of Pilot Treatment Trailer Showing Anion Exchange Contact Tanks, UV Reactor, Brine Thank, and Pipeline Reactors Anion Exchange The anion exchange contactors used in this study is shown in Figure 18 (Sta Rita; Park International; Long Beach, CA, model RT-948, Serial number 120604B: Regeneration model 5600). The units are 48 in ches high with a 9 inch diameter. Each was filled with about 1 cubic foot of resi n with a bed depth of about 2 ft. The characteristics of the resins are given in Table 14. The systems were operated at a flowrate of 1 to 2 gallons per minute resulti ng in a hydraulic loading rate of 2 to 4 gpm/ft2 with an empty bed contact time (EBCT) of less than one minute. UV Reactor Anion Exchan g e Reactors Pipeline Reactor Brine Tan k

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61 Table 14. Parameters of Anion Exchange Resins Tested in this Project (From Manufacturers’ Literature and MSDS Sheets) Parameter Resin A Resin B Matrix structure Macroporous Strong-base Crosslinked polystyrene Porous Styrene with divinyl benzene (DVB) Functional Group Quarternary ammonium R-N-(CH3)3 +ClExchange capacity 1 meq/mL not given Each of the contactors was operated semi-continuously over a several week period. Chlorine was added downstream of ani on exchange to evaluate chlorine demand and pH impacts associated w ith chloramination. The resins were regenerated using a brine solution. Oxidation Tests As part of this project, the impacts of using sodium hypochlorite on hydrogen sulfide reactions were evaluated under different pH conditions. In addition, the efficacy of using alternative oxidants, hydrogen pe roxide and UV irradiat ion was tested. A summary of the oxidation test s conducted for this proj ect is given in Table 15.

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62Table 15. Summary of Oxidation Test s Conducted on Water from the System Oxidant pH Goal Sodium hypochlorite Ambient & 8-8.5 Develop baseline kinetics for sodium hypochlorite oxidation of hydrogen sulfide; Evaluate chlorine demand; Assess turbidity formation Hydrogen peroxide followed by chlorine 7.5-8.5 Develop reaction kinetics as a function of pH; Assess characteristics or particulate matter formed in process UV followed by chlorine Ambient Develop reaction kinetics as a function of pH; Assess characteristics or particulat e matter formed in process Hydrogen peroxide followed by UV 7.5-8.5 Develop reaction kinetics as a function of pH; Assess characteristics or particulate matter formed in process Hydrogen peroxide followed by UV followed by chlorine 7.5-8.5 Develop reaction kinetics as a function of pH; Assess characteristics or particulate matter formed in process Water Quality A summary of the most important water qu ality parameters in the untreated water are provided in Figure 19 in boxplot format. The boxes represent 50% of the data and the horizontal lines represen t the median value. The height of the box reflects the variability of the data. These data collected between 1998 and 2005.

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63 Figure 19. Comparison of the Important Water Quality Parameters of a) Hydrogen Sulfide, b) Sulfate, c) TOC, d) Chloride, e) pH, and f) Turbidity. Data from 1998-2005 0 10 20 30 40 Well 1Well 2Well 3Well 4Well 6Well 7Well 8Well 9Chloride, mg/L 1 2 3 4 5 Well 1Well 2Well 3Well 4Well 6Well 7Well 8Well 9TOC, mg/L 0 10 20 30 40 Well 1Well 2Well 3Well 4Well 6Well 7Well 8Well 9Sulfate, mg/L 0 1 2 3 4 Well 1Well 2Well 3Well 4Well 6Well 7Well 8Well 9Turbidity, NTU 6.0 6.5 7.0 7.5 8.0 Well 1Well 2Well 3Well 4Well 6Well 7Well 8Well 9Field pH, Standard Units 0 1 2 3 4 Well 1Well 2Well 3Well 4Well 6Well 7Well 8Well 9Total Sulfide, mg/L a f e d c b

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64 Results and Discussion An anion exchange and chemical oxidation pilot test results are presented in this section. Finally a comparison among the al ternatives options is provided. Anion Exchange. Both of the resins that were test ed in the screening tests were effective at removal of hydrogen sulfide. A summary of water quality changes due to anion exchange is shown in Figure 7. The resins were effectiv e at reducing hydrogen su lfide and sulfate to below detection levels. Organic ca rbon removal ranged from 70-85%.

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65 0 1 2 3 4 Initial SulfideAE SulfideInitial TOCAE TOCSulfide or TOC, mg/L 0 20 40 60 Untreated SulfateAE SulfateUntreated ChlorideAE chlorideSulfate or Chloride, mg/L Figure 20. Comparison of Impacts of Anion Exchange (AE) on a) Hydrogen Sulfide, Organic Carbon (TOC) and b) Sulfate, and Chloride in Pilot Tests Conducted on Water from Well 9 During the Summer of 2005 A comparison of the removal efficiency of one of the anion exchange resins for hydrogen sulfide, organic carbon (TOC), and turb idity is shown in Figure 21. The initial sulfide level for these tests ranged from 2 to 3 mg/L and the hydrogen sulfide in the effluent was at or near the detection limits. TOC remova l was fairly consistent and ranged from 70 to 80% over the testing period. Turbidity removal was more variable due to the fluctuations in par ticle characteristics (size, concentration, and composition) associated with the untreated water. It s hould be noted that the system used for these preliminary tests was not hydraulically optimi zed. Further testing is in progress to evaluate the service cycl e of the resin for each of the source waters. a b

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66 0% 25% 50% 75% 100% 050010001500 Cumulative volume treated, g al/ft3Percent Removal Sulfide T OC T urbidity Figure 21. Percent Sulfide Removal Following Anion Exchange Treatment of Water from Well 9 as a Function of Volume of Water Treate d in Pilot Treatment Unit. Influent Sulfide Concentrations Ranged from 2 to 3 mg/L Another benefit of using anion exchange to remove hydrogen sulfide is a net reduction in the chlorine demand. Over the course of this study, the chlorine demand after anion exchange varied from about 0.2 to 6 mg/L for samples containing no detectable hydrogen sulfide as compared to chlorine demand levels of over 24 mg/L for the untreated water. Another issue that wa s evaluated in the preliminary tests was the impact of chlorination on pH. A summary of pH changes associated with addition of chlorine to water from well 9 that had been treated by anion exchange is shown in Figure 22 as a function of chlorine dose and chlo rine demand. As shown, the maximum pH increase was less than about 0.3 pH units.

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67 Figure 22. Comparison of Incremental pH Change Associated With Addition of Chlorine to Water from Well 9 Following Treatment by Anion Exchange Pilot-Scale Testing of Oxidation Reactions In this section the results of the chlorine, hydrogen peroxide, hydrogen peroxidechlorine, ultraviolet irradiati on-chlorine, and hydrogen peroxi de-ultraviolet irradiation are provided. Chlorine Oxidation A comparison of the concentr ation of hydrogen sulfide removed and the finished water turbidity is shown in Figure 23. As shown, the highe st turbidity levels were observed in water from well 9, however, ther e was not a direct relationship between

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68 hydrogen sulfide removal and turbidity formati on. Over the pH range tested, there did not appear to be a strong relationship betw een pH and turbidity formation, most likely due to other confounding variab les such as organic carbon an d variations in turbidity levels associated with the source water. 0 1 2 3 4 Well 2 Well 3 Well 4 Well 8 Well 9Total Suflide, mg/L or Turbidity, NTU Sulfide removed Final turbidity Chlorine at ambient pH Figure 23. Comparison of the Concentration of Sulfide Oxidized and the Concentration of Turbidity in Chlorinated Water from Wells 2, 3, 4, 8, and 9 Based on Pilot-Plant Testing Using Sodium Hypochlorite at Ambient pH Hydrogen Peroxide-Chlorine Oxidation Pilot-scale tests were de veloped using a 2 to 3 minute contact time for hydrogen peroxide followed by chlorine addition. Te sts were conducted at ambient pH and with pH adjustment either before or after hydroge n peroxide addition. Hydrogen peroxide was dosed at a rate of about 0.5 mg per mg of hydrogen sulfide.

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69 A summary of hydrogen su lfide removal and turbid ity generation through the two-stage oxidation process at ambient pH is shown in Figure 24. As shown, about half of the hydrogen sulfide was oxidized by hydr ogen peroxide and the remainder was oxidized by chlorine. However, significant le vels of turbidity were generated following the addition of chlorine. In contrast to the ambient pH condition, the water was pre-treated with caustic soda (sodium hydroxide) to raise the pH to about 8 prior to th e two-stage oxidation process. Results from the elevated pH testing are summarized in Figure 25. A lower quantity of hydrogen sulfide was oxidized by hydr ogen peroxide. In addition, turbidity levels associated with each stage of treatment were lower. It should be noted that the untreated water contained turbidity levels that varied over the course of this testing. If oxidation processes are conducted in-line, there are no mechanisms for removal of turbidity (unless the particulate matter is solubilized through oxidation). Obviously, some of the turbidity carrie s over through treatmen t, however additional turbidity is generated through the sequential reactions.

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70 Figure 24. Impact of Hydrogen Peroxide and Chlorine Oxidation of Hydrogen Sulfide on Levels of Total Sulfide and Turbidity in Water from Well 9 at Ambient pH Figure 25. Impact of Hydrogen Peroxide and Chlorine Oxidation of Hydrogen Sulfide on Levels of Total Sulfide and Turbidity in Wat er from Well 9 at Elevated pH (~ pH 8.3) 0 1 2 3 4Turbidity, NTU Well 9 NaOH-H2O2-NaOCl-NH4OH3 min 7 minInitial PostPostH2O2 Chlorine 0 1 2 3 4Total sulfide, mg/L Well 9 NaOH-H2O2-NaOCl-NH4OH3 min 7 minInitial PostPostH2O2 Chlorine 0 1 2 3 4Total sulfide, mg/L Well 9 H2O2-NaOCl-NH4OH3 min 7 minInitial PostPostH2O2 Chlorine 0 1 2 3 4Turbidity, NTU Well 9 H2O2-NaOCl-NH4OH3 min 7 minInitial PostPostH2O2 Chlorine

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71 Based on these results, th e optimum approach for applying this two-stage oxidation treatment is to elevate the pH prio r to hydrogen peroxide addition. The main advantage of using the two-stage oxidation is that it reduces the ne t chlorine demand of the water and could potentially form more st able reaction products. Turbidity levels associated with the two-stage oxidation were lo wer than levels associ ated with the use of sodium hypochlorite alone. Even though tu rbidity is not currently regulated in groundwater systems, it would be advantage ous to minimize the amount of particulate matter introduced into the water distribution system. Ultraviolet Irradiation-Chlorine Oxidation Results from pilot testing conducted at well 9 are shown in Figure 26. As shown, the decrease in hydrogen sulfide levels a ssociated with UV irradiation surpassed oxidation efficiencies associated with hydroge n peroxide. However, turbidity levels formed through the UV reactor and from chlorination were higher than turbidity associated with the other tr eatment scenarios evaluated.

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72 0 1 2 3 4InitialUV ChlorineTurbidity, NTU > 4 NTU > 4 NTU Well 9 UV-NaOCl3 min 7 min 0 1 2 3 4InitialUV ChlorineTotal sulfide, mg/L Well 9 UV-NaOCl3 min 7 min Figure 26. Impact of Using Ultraviolet (UV) Irradiation Coupled With Chlorine Oxidation of Hydrogen Sulfide on Levels of Total Sul fide and Turbidity in Water from Well 9 Hydrogen Peroxide – Ul traviolet Irradiation In this project the combin ation of hydrogen peroxide with UV was tested under different pH conditions. Results from hydrogen peroxi de-UV oxidation followed by chlorination and ammonia addition are su mmarized in Figure 27. As shown, the combination of hydrogen peroxide and UV was ef fective at reducing th e concentration of hydrogen sulfide. However, significant turbidity was ge nerated through the process.

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73 0 1 2 3 4Total sulfide, mg/L Well 9 H2O2-UV-NaOCl-NH4OH3 min 7 minInitial PostPostH2O2-UV Chlorin e 0 1 2 3 4Turbidity, NTU Well 9 H2O2-UV-NaOCl-NH4OH3 min 7 minInitial PostPostH2O2-UV Chlorine> 4 NTU > 4 NTU Figure 27. Impact of Using Hydrogen Peroxide Coupled With Ultraviolet (UV) Irradiation Followed by Chlorine Oxidation on Levels of Total Sulfide and Turbidity in Water from Well 9 Water Quality Comparison of Technologies A comparison of the imp act of each of the candida te technologies on hydrogen sulfide, organic carbon, sulfat e, turbidity, and chloride is given in Figures 28-29. For purposes of comparison, water quality parame ters are compared to untreated water quality from well 9. While the trends are likely to be similar, water from other wells may not reflect the exact same relationships. Each of the technologies is effective for reduction of hydrogen sulfide. In addition, the use of chlorine disinfecti on downstream of hydrogen sulfide control provides supplemental treatment capacity by reacting with residual hydrogen sulfide as needed, providing an additional hydrogen sulfide control measure. In consort with control of hydrogen sulfide, th e chlorine demand of the wate r is reduced by all of the technologies (except chlorine oxidation). Th e extent of the chlorine demand reduction

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74 depends on the amount of residual hydrogen su lfide associated with each technology. Data shown in Figures 28 and 29 are derive d from pilot-scale and bench-scale tests conducted during this project. 0 1 2 3 4Sulfide, mg/L Well 9 Aeration Anion Oxidation Untreated Exchange 0 10 20 30Chlorine Demand, mg/L as Cl2 Well 9 Aeration Anion Oxidation Untreated Exchange Figure 28. Effectiveness of Aeration, Anion Exchange, and Oxidation for Reduction of Hydrogen Sulfide and Chlorine Demand Associated Anion exchange is the only one of the candidate technologies that is effective for reduction of sulfate and organic carbon. The levels of sulfate and organic carbon shown in Figure 16 are derived from preliminary pi lot-scale tests conducted on water from well 9. Aeration and oxidation are not expected to impact sulf ate or organic carbon levels.

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75 0 10 20 30 40Sulfate, mg/L as SO4 Well 9 Aeration Anion Oxidation Untreated Exchange 0 1 2 3 4TOC, mg/L Well 9 Aeration Anion Oxidation Untreated Exchange Figure 29. Impact of Aeration, Anion Exchange, and Oxidation on Organic Carbon (TOC) and Sulfate Levels in Treated Water The impacts of each technology on turbidity are variable depending on the turbidity characteristics associated with the untreated water. Aeration and oxidation technologies do not have any mechanism for re moval of turbidity, thus it is anticipated that turbidity levels will not decrease using these technologi es. Turbidity may increase through treatment due to the formation of mine ral precipitates and organic particles. Biological growth within the aeration tower ma y also contribute intermittent turbidity to aerated water. Anion exchange has the capac ity to remove particles depending on their size, surface charge, and physical properties. A qualitative comparison of th e water quality impacts of the candidate hydrogen sulfide control technologies is given in Ta ble 16. As shown, while all technologies are effective at controlling hydrogen sulfide levels anion exchange offers additional water quality advantages for reduction of su lfates, organic ca rbon, and turbidity.

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76Table 16. Qualitative Comparison of Impacts of Treatment Technologies on Water Quality Water Quality Parameter Packed-Towera Aeration with pH control Fixed-Bed Anion Exchange Oxidation Sulfide >90% removal/conversion >90% removal >90% conversion Sulfate No impact >90 % removal No impact, minor increase due to sulfate formation (2.8 mg sulfate /mg sulfide oxidized Organic Carbon No impact 60-80% removal No impact Turbidity No removal mechanism; potential increase due to sloughing of biomass and chemical precipitates from oxidation/precipitation reactions that occur in the aeration tower Removal of negatively charged colloidal particles; no mechanism for turbidity formation No removal mechanisms; potential formation due to mineral and organic oxidation (iron, sulfur, organic colloids, etc.) Chloride No impact Increases 1 mg/mg sulfide removed and 0.7 mg/mg sulfate removed Chlorine oxidation results in 5-8 mg of chloride per mg of sulfide converted; Other oxidants have no impact on chloride levels pH Controlled upstream and downstream of process No impact Upstream control Dissolved oxygen Increase up to oxygen saturation No impact Slight increase Chlorine demand Reduction proportional to sulfide removal Reduction proportional to sulfide removal Reduction proportional to sulfide oxidation. Supplemental chlorine demand due to partially oxidized organics and presence of residual oxidant Potential for hydrogen sulfide reformation Minor impact because only one form of sulfur is removed: nonionized hydrogen sulfide Major impact because most forms of sulfur are removed Minor impact; Hydrogen sulfide is converted to more stable form, but not removed. aPacked tower aeration includes supplying air through forced draft (or induced draft)

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77 Conclusions This study has provided the opportunity to evaluate the control of hydrogen sulfide from groundwater using packed-bed anion exchange and ch emical oxidation. The major conclusions of this project are: 1. The co-occurrence of other water quality constituents, particularly organic carbon and turbidity, should be considered in a ssessing the efficacy of various hydrogen sulfide control technologies. 2. Aeration technology provides an effectiv e approach for removing and oxidizing hydrogen sulfide. Air stripping serves to remove nonionized hydrogen sulfide. The oxygen introduced through aeration serves as an oxidant that can react with hydrogen sulfide and other reduced mine rals. Biological oxidation of hydrogen sulfide can also occur within aeration systems. There is potential for turbidity to be generated through the aera tion process due to biologi cal activity coupled with chemical oxidation of sulfur and other minerals. The use of aeration also requires on-site storage of chemicals for pH control and repressurization of the water prior to disinfection and introd uction of the treated water into the distribution system. 3. Fixed-bed anion exchange technology is effective for removing hydrogen sulfide from the Seven Springs source water. Additional benefits of anion exchange technology include coincident removal of ot her forms of sulfur including sulfates, polysulfides, thiosulfates, and sulfites. In addition, negatively charged (anionic) forms of organic carbon, color-comp ounds, and turbidity are removed through treatment. Anion exchange technol ogy does not generate nuisance odors or

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78 noise, thus imposing minimal impact to neighboring property owners. Another advantage of fixed-bed anion exchange is that treatment systems can be designed to be compatible with existing site cons traints, thus reducing the costs and time needed for implementation. Because the wa ter is treated direc tly from the wells, the implementation of anion exchange technology would not require repressurization. 4. Oxidation technology is effective fo r control of hydrogen sulfide through conversion reactions, however the presence of organics in the untreated water poses water quality complications that result in the genera tion of turbidity upon the addition of chlorine fo r disinfection. Oxidation t echnology requires additional on-site storage of chemicals and process controls for chemical dosing and water quality monitoring. Oxidation technology is essentially an “in-pipe” treatment and does not require repressuri zation prior to introduction of the treated water into the distribution system. Acknowledgments The assistance from the staff at Aloha Utilities in constructing the pilot plant and helping with start-up and operation is apprecia ted. Jack Burke, Mike McDonald, and Charlie Painter provided valuable assistan ce with pilot-plant op eration. Pam Yacobelli provided assistance with background informa tion, data, and facilitating schedules for operation of the pilot plant. The assistan t of Barbara Dodge as the Environmental Engineering Laboratory Manager is appreciate d. Several USF students participated in the project by providing supplemental field and laboratory assistance including Salah Al Bustami, Allen Hunter, Mindy Decker, Erin McMahan, Lisa Rhea, and Cecilia Claudio; their assistance with this project is appr eciated. Mike Fagan and Dan Kile of US

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79 Peroxide provided technical support for the hydrogen peroxide tes ting. Tom Davis and Amelia Jordan of Tonka Equipment and Chuck Hvalach of EnviroSales provided technical support for anion exchange testi ng. Peter Meyers and Phil Adams of Resin Tech provided technical insight on anion exchange resins.

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80 Conclusions The research results presented in this thesis suggest that packed-bed anion exchange is a viable option for the contro l of hydrogen sulfide from groundwater sources. The major conclusions drawn from this research are listed below. 1. Bed-packed anion exchange is effect ive in removing hydrogen sulfide from groundwater sources. 2. Anion exchange reduces the total mass of su lfur in water, thereby decreasing the potential for re-formation of hydrogen sulfide in the distribution system. 3. Anion exchange is capable of removi ng 50-70% of the dissolved organic carbon. Reduction of TOC can help to meet requireme nts of new regulations that relate to the disinfection byproduct s (Stage 2 D/DBP) 4. Removal of hydrogen sulfid e through anion exchange reduces the chlorine demand. Reduction in chlorine demand decrea ses the potential risks for formation of DBPs and chemical cost. 5. More measurements using diverse water qua lity sources are n ecessary to develop a reliable model that can predict the re sin performance. The model developed for this project was validated for sulfide le vels ranging from 1 to 2.6 mg/L as S2and sulfate levels ranging from 1 to 37 mg/L as SO4 2-.

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81 6. Hydrogen sulfide can be effectively oxidi zed using several different chemical oxidizers. However, filtration is needed downstream to remove particulate matter generated during oxidation.

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82 Engineering Implications The potential use of anion exchange for the removal of hydrogen sulfide was studied starting in the 1950’s (Thompson and Mc Garvey 1952). However, little attention has been paid to its application. This study provides insight into the application, performance, as well as factors that influen ce the use of bed-packed anion exchange for the removal of hydrogen sulfide from groundwater resources. The data generated by this study have verified the effectiveness of anion exchange for hydrogen sulfide control. Curren tly, the use of aeration is recommended as the most effective hydrogen sulfide cont rol strategy (FDEP, 2003). However, in comparison to aeration, anion exchange can achieve higher removal rates at typical groundwater pH, reduce corrosion problems, decr ease turbidity generation, and eliminate noise and nuisance odors. Another benefit of the use of anion exchange technology is that it allows for the removal of other forms of sulfur in the final effluent. Because of the nature of the sulfur cycle, the re-formation of hydrogen sulfide is possible under anaerobic conditions. An example of the latter would be the re -formation of the hydrogen sulfide from the oxidation of the sulfate in the distribution system. A major benefit of using ani on exchange is that it is effective at reducing the levels of disinfection byproducts precursors In this study, ani on exchange technology removed up to 70% of the TOC. The improved water quality can result in lower cost for

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83 operation of treatment facilities. Anion ex change technology can d ecrease the chlorine demand in treated water, thereby reducing th e chemical dosages needed for disinfection. In addition to water quality im provements, there are other advantages to the use of packed-bed anion exchange. Because it is a closed system, re-pressurization is not required. In addition, the footprint of the pro cess is smaller than aeration systems. The use of anion exchange decreases the ch lorine demand and therefore reduces the possibility of health risks to operators in handling chemicals, and decreases the amount of space needed for chemical storage. However, the impact of th e waste stream from the anion exchange is not well understood. High concentrations of sulfur species, chlorides, a nd organics are expected in the regenerant waste stream. Optimal dosages of salt and a decrease in the regeneration frequency process are required to diminish the production of waste. A combination of different factors such as an injection of air in the column and the presence of sulfide oxidizing bacteria are likely to have a positive effect increasing the resin capacity.

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84 Additional Research Recommendations for further research fo r the application of bed-packed anion exchange technologies for the removal of hydrogen sulfide from groundwater sources should include: 1. Evaluate the impact of air presence in the column to improve the resin capacity. The air presence in the column improved the resin capacity in the present study. An indepth study will be required to understand the implication that this injection will have on the kinetics of th e system. The immediate impact can be the reduction of the frequency of the regeneration process. 2. Examine the role of sulfide oxidizing bact eria in the removal process. The growth of this type of bacteria was observed. This population may impact the removal of the hydrogen sulfide in the column. The presence of these microorganisms can improve the resin performance. 3. Optimize the salt concentration duri ng the column regeneration process. Reductions in the salt concentration may k eep the resin capacity inalterable and it can result in a re duction of the associated cost. 4. Evaluate the impact of the addition of the brine solution on the microbial population. Determine the microbial suscepti bility to salt, and its presence after the regeneration process. It is also important to determine the required time to repopulation the microorganism.

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85 5. Determine which organic fraction is removed by the use of anion exchange technology. This helps to determine if anion exchange can help prevent the formation of DBPs. 6. Evaluate the possible presence of phototr ophic sulfide oxidizing bacteria. This provides insight if the speci fic pilot test design promotes the growing of these kinds of bacteria, and if this phenomenon can be reproduced in full scale treatment. 7. Use different combinations of brine solution. Thompson and McGravey (1953) suggest the use of a brine solution w ith 90% of salt and 10% of sodium bicarbonate for water with a pH between 7 and 8. 8. Evaluate the use of other oxidants su ch an ozone, ferrate, and potassium permanganate as an alternative trea tment to control hydrogen sulfide.

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86 References American Water Works Association and Ameri can Society of Civil Engineers. (1998). Water Treatment Plant Design. New York: McGraw Hill. Anderson, C.T., and Maier, W.J. (1979) Trace Organic Removal by Anion Exchange Resin. Journal American Water Works Association, 71, 278. Bae, B., Jung, Y., Han, W., and Shin, H. (2002). Improved Brine Recycling During Nitrate Removal Using Anion Exchange. Water Research, 36,3330-3340. Black, A.P., and Goodson, J.B. (1952). The Oxidation of Sulfides by Chlorine in Dilute Aqueous Solutions. Journal American Water Works Association, 44, 309. Bolto, B., Dixon, D., Eldridge, R., King, S., a nd Linge, K. (2002). Removal of Natural Organic Matter by Ion Exchange. Water Research 36, 5057-5065. Cadena, F., and Peters, R.W. (1988) Evalua tion of Chemical Oxidizers for Hydrogen Sulfide Control. Journal Water Polluti on Control Federation, 60, 1259-1263. Chen, K.Y., and Morris, J.C., (1972) Kine tics of Oxidation of Aqueous Sulfide by Oxygen, Environmental Science and Technology, 6,6,529-537. Clifford, D. (1999). Water Quality and Treatment. A Handbook of Community Water Supplies. New York: McGraw Hill. Crepaldi, E.L., Pavan, P.C., and Valim, J.B. (2000) Anion Exchange in Layered Double Hydroxides by Surfactant Salt Formation, Journal of Materials Chemistry, 10,1337-1343. Crittenden, J.C., Trussell, R.R., Hand, D. W., Howe, K.J., and Tchobanoglous, G. (2005). Water Treatment. Principles and Design. Second Edition, New Jersey: John Wiley & Sons. Dell’Orco, M., Chadik, P., Bitton, G., and Neumann, R.P. (1998) Sulfide-Oxidizing Bacteria: Their Role During Air Stripping. Journal American Water Works Association, 90, 107-115.

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87 Dohnalek, D.A., and FitzPatrick, J.A. (1983) Chemistry of Reduced Sulfur Species and Their Removal from Groundwater Supplies. Journal American Water Works Association,75, 298-308. Droste, RL. (1997). Theory and practice of water and wastewater treatment. New York: John Wiley & Sons. Duranceau, S.T., Anderson, R.K., and Teegarde n, R.D. (1999) Comparison of Mineral acid. Pretreatments for sulfide removal. Journal American Water Works Association, 91, 85-96. Fettig, J. (1999). Removal of Humic S ubstances by Adsorption/Ion Exchange. Water Science Technology, 40, 173-182. Flentje, M.E. (1937) Aeration. Journal American Water Works Association, 29, 872. Foxworthy, J.E., and Gray, H.K. (1958) Removal of Hydrogen Sulfide in High Concentrations from Water. Journal American Wate r Works Association, 50, 873-878. Ghurye, G., Clifford, D., and Tripp, A. ( 1999). Combined Arsenic and Nitrate Removal by Ion Exchange. Journal American Water Works Association, 91, 8596. HDR Engineering, Inc., (2005) Handbook of Public Water Systems, John Wiley and Sons, New York,. Hoffman, M.R. (1977). Kinetics and Mechanis m of Oxidation of Hydrogen Sulfide by Hydrogen Peroxide in Acidic Solution. Environmental Science and Technology, 11, 61-66. Jacobs, S., Reiber, S., and Edwards, M. (1998) Sulfide Induced Copper Corrosion, Journal American Water Works Association, 90,7, 62-73. Jewell, B.S. (2002) Hydrogen Sulfide Re moval from Groundwater: A Case Study. Honors’ Thesis. Univ. of South Florida. Karcher, S., Kornmller, A., and Jekel. ( 2002). Anion Exchange Resin for Removal of Reactive Dyes from Textile Wastewaters. Water Research, 36, 4717-4724. Kim, J., and Benjamin, M.M. (2004). M odeling a Novel Ion Exchange Process for Arsenic and Nitrate Removal. Water Research, 38, 2053-2062. Korngold, E., Belayev, N., and Aronov, L. (2001) Removal of Arsenic from Drinking Water by Anion Exchangers, Desalination, 141, 81-84.

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88 Kotronarou, A., and Hoffman, M. (1991) Cata lytic Autooxidation of Hydrogen Sulfide in Wastewater, Environmental Science and Technology, 25,6,1153-1160. Letterman, R., editor (1999) Water Quality and Treatment, Fifth Edition, McGraw Hill, N.Y. Levine, A.D., Minnis, R.J., Bustami, S. A., Romero, C., and Dodge, B.M. (2005). Evaluation of Alternative Technologies for Control of Hydrogen Sulfide from Groundwater Sources in the Seven Spring Service Area. Project Final Report. Aloha Utilities, Inc. New Port Richey, FL. Levine, A.D., Raymer, B.J. and Jahn, J. (2004b) Evaluation of Biological Hydrogen Sulfide Oxidation Coupled with Two-St age Upflow Filtration for Groundwater Treatment Journal of Environmental Science and Health, Part AToxic/Hazardous Substances & Environmental Engineering, Vol. A39, No. 5, 1263-1279. Liang, S., Mann, M.A, Guter, G.A., Kim, P.H., and Hradan, D.L.Chan. (1999). Nitrate Removal from Contaminated Groundwater. Journal American Water Works Association, 91, 79-91. Lyn, T.L., and Taylor, J.S. (1992) Assessi ng Sulfur Turbidity Formation Following Chlorination of Hydrogen Sulfide in Groundwater. Journal American Water Works Association 84, 103-112. Madigan, M.T., and Martinko, J.M. (2006) Brock Biology of Microorganism. Eleven Edition, New Jersey: Pearson Prentice Hall. Matson, M.D. (1937) Mill Effluent Br eathes Easier With Carbon Dioxide. Water Engrg & Mgmt, 135, 38. Morse, J.W., Millero, F.J., Cornwell, J.C., a nd Rickard, D.(1987) "The Chemistry of the Hydrogen Sulfide and Iron Sulfide Systems in Natural Waters, Earth Science Reviews, 24, 1-42 1987. Namasivayam, C., and Hll, W.H. (2005) Qu aternized Biomass as Anion Exchange for the Removal of Nitrate and Other Anions from Water. Journal of Chemical Technology and Biotechnology, 80, 164-168. O’Brien, Dd.J., and Birkner, F.B. (1977) Ki netics of Oxygenation of Reduced Sulfur Species in Aqueous Solution, Environmental Science and Technology, 11,12,1114-1120.

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89 Owens, D.L. (1995) Practical Principl es of Ion Exchange, Tall Oaks Publishing, Littleton, CO. Powell, S.T., and Von Lossberg, L.G. (1948) Removal of Hydrogen Sulfide from Well Water. Journal American Water Works Association, 40, 1277-1290. Roe, F.C. (1935) Aeration of Water by Air Diffusion. Journal American Water Works Association, 27, 897. Sammons, L.L. (1959). Removal of Hydroge n Sulfide from a Ground Water Supply. Journal American Water Works Association, 51, 1275-1276. Schiller, B. (1955) Vacuum Degasification of Water for Taste and Odor Control. American Water Works Association, 47, 124-128. Sharma, V.K., Smith, J.O., and Millero, F.J. (1997) Ferrate Oxidation of Hydrogen Sulfide, Environmental Science and Technology, 31,9,2486-2491. Sheppard, T., and von Lossberg, L.G. (1948) Removal of Hydrogen Sulfide from Well Water. Journal American Water Wo rks Association, 40, 1277-1289. Stumm, W. (1960). Investigation of the Corrosive Behavior of Waters, Journal of the Sanitary Engineering Division, ASCE, 86, SA6, 27-45. Stumm, W., and Morgan, J.J. (1996) Aquatic Chemistry, John Wiley & Sons, NewYork. Sullivan, P.J., Yelton, J.L., and Reddy, K. (1988) Iron Sulfide Oxidation and the Chemistry of Acid Generation Environ. Geol. Water Sci., 11, 3, 289-295. Thompson, J., and McGarvey, F.X. (1953). IonExchange Treatment of Water Supplies. Journal American Water Works Association, 45, 145-152. Thompson, M.A., Kelkar., U.G., and Vickers, J.C. (1995) The Treatment of Groundwater Containing Hydrogen Sulfid e Using Microfiltration. Desalination,102, 287-291. U.S. Environmental Protection Agency (2006). Ground Water & Drinking Water. http://www.epa.gov/ogwdw/mdbp/st2f r29.html. Accessed March 2006. Wachinski, A.M, and Etzel, J.E. (1997). Environmental Ion exchange. Principles and Design. New York. Lewis Publishers. Wells, S.W. (1954) Hydrogen Sulfide Problems of Small Water Systems Journal American Water Works Association, 46,160-170. White, G.C.(1999) Handbook of Chlorination and Alternative Disinfectants, John Wiley.

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90 Zhao, X., Hll, W.H., and Yun, G. (2002). E limination of Cadmium Trace Contaminants from Drinking Water. Water Research, 36, 851-858.

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91 Appendices

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92 Appendix A: Pilot Column Design Configuration A/R. Air valve BRI. Brine valve BWE. Backwash effluent BWI. Backwash influent FRE. Fast rinse/ Brine effluent ISO. Isolation valve RWI. Raw water influent. TWE. Treated water effluent

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93 Appendix A: (Continued) Figure 30. Anion Exchange Control Panel Main Valve RWI FRE BWI ISO BWE TWE

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94 Appendix A: (Continued) Operating and Regenerating Procedure 1. Service Mode a) Open Main Valve b) Set pressure reduced to 12 – 15 psi c) Open RWI d) Open ISO e) Open TWE. Operate the column between 2 – 8 gph f) Close all valves when the run is complete 2. Regeneration mode a) Backwash Close all valves Set the pressure reduce to 12 – 15 psi Open Main valve Open BWI Open BWE. Leave open for 10 minutes at 4 gph Close BWI and BWE b) Drain Down Open FRE Open A/R Close FRE when the water level is 3” above the resin c) Brine Open BRI

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95 Appendix A: (Continued) Pour diluted brine solution into the funnel Open FRE Close FRE and leave the resin in c ontact with the re sin for the ` chose contact time Open FRE let the brine drain until br ine level is 3” above the resin Close BRI d) Slow Rinse Open RWI Close A/R once the water come out Open FRE. Leave open for 25 minutes at 2 gph e) Fast Rinse Change the flow rate of FRE to 8 gph for 10 minutes Close FRE Close RWI Return to the operating mode

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96 Appendix A: (Continued) Brine Mixing Instructions 1. Add three pound of non-i odized salt to 1 gall on of distilled water 2. Stir the solution 3. Measure 940 ml of solution in grad uated cylinder in plastic recipient 4. Measure 940 ml of distilled wa ter and add to brine solution 5. Shake the diluted solution 6. Pour the diluted solution into the anion exchanger funnel.

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97 Appendix B: Summary of Raw Water Quality and Anion Exchange These data correspond to raw water and anion ex change effluent. The data were collected between September 1, 2005 and January 26, 2006.

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98 Table 17. Raw Water Qualit y Summary from Well A Parameter Median Mean Minimum Maximum Std. Deviation Std. Error Skewness Kutorsis Sample variance N Sulfide (mg/L as S-) 2.75 2.64 2.03 3.23 0.26 0. 05 -0.34 0.23 0.07 30 Ph 7.41 7.39 6.79 7.55 0. 15 0.03 -2.87 9.53 0.02 31 Temperature (C) 22.90 23.70 11.70 27.10 2.94 0.53 -2.40 8.50 8.67 31 DO (mg/L as O2) 1.50 1.49 0.01 6.20 1. 77 0.56 2.45 6.94 3.12 10 ORP, (mV) -202.0 -189.6 -244.0 -137.0 38.53 12.84 0.24 -1.43 1484.7 9 Sulfate (mg/L as SO4 2-) 38.90 37.38 26.00 49.70 7.04 1.36 0.23 -1.10 49.60 27 Chloride (mg/L as Cl-) 17.80 19.72 10.09 44.77 8. 26 1.56 2.02 4.77 68.19 28 Alkalinity (mg/L as CaCO3) 200.00 163.50 100.00 250.00 53.99 11.02 0.11 -1.57 2914.87 24 Conductivity ( S/cm) 491.00 463.71 341.00 570.00 54.55 9. 80 -0.46 -0.23 2975.21 31 Turbidity (NTU) 0.31 0.32 0.07 1.51 0.33 0.06 2.37 5.84 0.11 31 A Color (mg/L Pt.Co) 8.00 9.82 0.00 28.00 7.64 2.30 1.34 2.47 58.36 11 T Color (mg/L Pt.Co) 7.00 5.64 -2. 00 14.00 5.01 1.51 -0.15 -0.83 25.05 11 TOC (mg/L) 2.66 2.78 1.54 6. 87 0.84 0.16 4.30 21.55 0.71 29 UV-254 (cm-1) 0.09 0.13 0.03 1.06 0. 19 0.03 4.76 23.97 0.03 30 Aluminum (mg/L) 0.00 0.00 0. 00 0.00 0.00 0.00 2.24 5.00 0.00 5 Silica (mg/L) 10.50 0.67 7.50 9. 98 1.50 8.11 -1.51 2.11 2.26 5 Copper (mg/L) -0.01 0.00 -0.03 0.07 0.04 0.02 1.00 -0.97 0.00 6 Calcium (mg/L) 67.44 66.07 59.26 68.64 3.53 1.44 -1.94 3.83 12.44 6 Magnesium (mg/L) 9.13 8.86 7.46 9.19 0.69 0.28 -2.43 5.92 0.47 6 Sodium (mg/L) 7.67 0.10 7.27 7. 57 0.23 7.28 -0.54 -2.60 0.05 5 A pp endix B: ( Continued )

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99 Table 18. Raw Water Quality Summary from Well B Parameter Media Mean Minimu m Maximu m Std. Deviation Std. Error Skewnes s Kutorsi s Sample variance N Sulfide (mg/L as S-) 1.61 1.64 1.34 2.45 0. 22 0.04 1.74 5.33 0.05 27 pH 7.38 7.35 6.58 7.52 0. 17 0.03 -3.74 16.67 0.03 27 Temperature (C) 25.10 24.11 11.10 28.30 3.26 0.63 -2.69 9.55 10.65 27 DO (mg/L as O2) 209.50 207.67 -241.00 -158.00 32.20 13. 14 0.51 -0.56 1036.67 6 ORP (mV) 0.54 0.62 0.00 1.53 0.62 0.20 0.32 -1.76 0.38 10 Sulfate (mg/L as SO4 2-) 8.15 7.27 -0.40 18.60 4. 44 0.89 4.41 21.26 222.38 25 Chloride (mg/L as Cl-) 13.94 14.67 10.09 28.44 4. 29 0.81 1.39 2.67 18.38 28 Alkalinity (mg/L as CaCO3) 200.00 180.30 100.00 260.00 52.11 10. 03 -0.36 -1.40 2715.37 27 Conductivity ( S/cm) 449.00 427.33 323.00 520.00 52.83 10. 17 -0.56 -0.84 2790.54 27 Turbidity (NTU) 0.20 0.60 0.07 4.03 0.89 0.17 2.76 8.46 0.79 27 A Color (mg/L Pt.Co) 9.00 14.55 -1 .00 51.00 15.27 4.60 1.72 2.68 233.07 11 T Color (mg/L Pt.Co) 7.00 8.00 16.00 44.00 14.09 4.25 1.41 5.22 198.40 11 TOC (mg/L) 2.65 2.68 1.73 3. 46 0.27 0.05 -0.68 6.93 0.07 29 UV-254 (cm-1) 0.08 0.08 0.07 0.14 0. 02 0.00 1.53 3.47 0.00 26 Aluminum (mg/L) 0.00 0.01 0. 00 0.02 0.01 0.00 1.48 1.41 0.00 8 Silica (mg/L) 9.60 9.64 7.80 11. 40 1.47 0.52 0.01 -2.13 2.16 8 Copper (mg/L) -0.03 -0.04 -0. 13 0.02 0.05 0.02 -0.88 0.18 0.00 7 Calcium (mg/L) 55.57 56.84 50.33 63.45 5.43 1.92 0.23 -1.98 29.51 8 Magnesium (mg/L) 7.02 7.35 4.05 9.04 1.80 0.68 -0.97 0.80 3.24 7 Sodium (mg/L) 6.76 0.07 6. 71 6.81 0.13 6.49 1.47 0.02 3 A pp endix B: ( Continued )

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100 Table 19. Raw Water Qualit y Summary from Well C Parameter Median Mean Minimu m Maximu m Std. Deviation Std. Error Skewness Kutorsi s Sample variance N Sulfide (mg/L as S-) 1.02 1.07 0.82 1.51 0. 20 0.05 0.74 0.27 0.04 13 pH 7.39 7.38 7.20 7.63 0. 10 0.03 0.31 2.88 0.01 13 Temperature (C) 25.30 24.90 23.10 26.80 1.14 0.32 -0.22 -0.88 1.29 13 DO (mg/L as O2) 0.02 0.00 0.02 0.02 24.21 1 ORP (mV) Sulfate (mg/L as SO4 2-) 6.40 14.75 0.70 79.00 21. 68 6.01 2.58 6.97 470.03 13 Chloride (mg/L as Cl-) 19.72 24.47 10.09 46.70 11.68 3.24 0.87 -0.53 136.48 13 Alkalinity (mg/L as CaCO3) 180.0 13.6 120.0 166.0 128. 1 -1.04 -0.42 930.00 5 Conductivity ( S/cm) 397.50 384.5 8 285.00 502.00 54.85 15.83 0.20 1.43 3008.45 12 Turbidity (NTU) 0.17 0.53 0.10 3.12 0.89 0.27 2.94 8.99 0.79 11 A Color (mg/L Pt.Co) 14.00 19.00 12.00 38.00 10.14 4.14 1.75 2.75 102.80 6 T Color (mg/L Pt.Co) 9.00 2.10 1.00 8.00 2.18 -0.80 0.07 22.00 5 TOC (mg/L) 2.46 2.37 1.49 2. 61 0.32 0.10 -2.78 8.26 0.10 10 UV-254 (cm-1) 0.09 0.12 0.04 0.38 0. 11 0.04 2.52 6.70 0.01 8 Aluminum (mg/L) 0.00 0.00 0. 00 0.00 0.00 0.30 -4.32 0.00 4 Silica (mg/L) 6.50 0.41 5.80 6.55 5.25 0.10 -5.27 0.67 4 Copper (mg/L) -0.07 0.02 -0.10 -0.05 -0.12 1.16 0.45 0.00 5 Calcium (mg/L) 56.27 59.97 51.06 77.50 10.35 4.22 1.18 0.39 107.08 6 Magnesium (mg/L) 5.65 0.45 4. 02 5.62 4.37 -1.05 1.70 1.01 5 Sodium (mg/L) A pp endix B: ( Continued )

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101 Table 20. Raw Water Quality Summary from Well D Parameter Median Mean Minimum Maximu m Std. Deviation Std. Error Skewnes s Kutorsis Sample variance N Sulfide (mg/L as S-) 0.93 0.94 0.56 1.23 0.15 0.03 -0.39 0.15 0.02 35 pH 7.49 7.44 6.03 7.61 0. 26 0.05 -5.19 28.58 0.07 33 Temperature (C) 24.40 24.21 12.00 27.70 2.66 0.46 -3.03 13.90 7.06 33 DO (mg/L as O2) 1.39 3.76 0.80 24.90 6. 87 1.98 3.14 10.15 47.15 12 ORP (mV) -150.50 147.9 2 -232.00 -14.00 67.58 19. 51 0.54 -0.48 4567.72 12 Sulfate (mg/L as SO4 2-) 1.00 1.08 -0.60 3.20 0. 75 0.13 0.86 2.12 0.56 32 Chloride (mg/L as Cl-) 13.94 14.62 8.17 21.65 3.91 0.67 0.27 -0.64 15.27 34 Alkalinity (mg/L as CaCO3) 160.00 147.8 8 30.00 250.00 47.10 8.33 -0.24 -0.15 2218.82 32 Conductivity ( S/cm) 397.00 377.4 8 232.00 454.00 50.49 8.79 -1.49 1.68 2548.76 33 Turbidity (NTU) 0.17 0.24 0.07 1.25 0.23 0.04 3.22 11.51 0.05 33 A Color (mg/L Pt.Co) 12.00 12.44 5. 00 22.00 6.11 2.04 0.25 -1.47 37.28 9 T Color (mg/L Pt.Co) 9.00 10.38 2.00 19.00 5.18 1.83 0.15 0.29 26.84 8 TOC (mg/L) 3.08 3.08 2.79 3. 35 0.14 0.02 0.13 0.07 0.02 32 UV-254 (cm-1) 0.10 0.10 0.04 0.13 0.02 0.00 -1.78 4.79 0.00 31 Aluminum (mg/L) 0.01 0.00 0.00 0.00 0.00 -0.01 -0.33 0.00 3 Silica (mg/L) 7.00 1.41 6.10 7.93 2.44 1.88 1.47 5.94 3 Copper (mg/L) -0.08 0.02 -0.09 -0.06 0.04 -0.11 2.04 4.27 0.00 5 Calcium (mg/L) 76.39 7.45 48.17 66. 45 16.66 45.76 -0.57 -3.27 277.66 5 Magnesium (mg/L) 5.60 0.32 4.08 5.35 0.72 4.46 -2.11 4.57 0.51 5 A pp endix B: ( Continued )

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102 Table 21. Anion Exchange Data from Well A Run 1 1 1 1 1 1 1 1 1 1 Date 10/28/05 10/28/05 10/28/05 10/28/05 10/28/05 10/28/05 10/28/05 10/28/05 10/28/05 10/28/05 Volume 1.68 1.75 2.625 1.56 1.56 1.56 3.12 3.12 3.12 3.12 Accumulate Volume (gal) 1.68 3.43 6.055 7.615 9.175 10.735 13.855 16.975 20.095 23.215 Flow rate (gph) 3.51 3.51 3.14 3.14 3.14 3.14 3.14 3.14 3.14 3.14 Sulfide (mg/L as S-) 1.534 0.635 1.302 0.6 0.43 0.32 0.16 0.17 0.19 0.215 pH 6.54 6.5 6.45 6.46 6. 42 6.43 6.43 6.46 6.54 6.61 Temperature (C) 14.2 16.9 19 20.3 22.4 24 24.5 23.2 24 23.4 ORP (mV) DO (mg/L as O2) Sulfate (mg/L as SO4 2-) 0.5 0 0.1 0 0.2 0 0 0 0 0 Chloride (mg/L as Cl-) 187.34 197.25 177.98 235.78 255.05 216.51 274.31 139.45 235.78 235.78 Alkalinity (mg/L as CaCO3) Conductivity ( S/cm) 529 573 583 629 636 655 701 635 634 614 Turbidity (NTU) 3.17 0.809 0.52 0.52 0.48 0.401 0.36 0.67 0.39 0.362 TOC (mg/L) 2.99 2.14 2.81 3. 77 0.526 1.09 0.526 0.606 0.541 UV-254 (cm-1) 0.001 0.034 0.021 0.023 -0.004 0.006 UDL* 0.005 0.017 0.016 UDL*, Under Detection Limit A pp endix B: ( Continued )

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103 Table 21. Continued Run 2 2 2 2 2 2 2 3 3 3 Date 10/31/05 11/01/05 11/01/05 11/01/05 11/01/05 11/02/05 11/04/05 12/05/05 12/06/05 12/07/05 Volume 0 26.28 6.93 10.98 5.49 14.88 43.66 0 61.07 72.05 Accumulate Volume (gal) 0 26.28 33.21 44.19 49.68 64.56 119.51 0 61.07 133.12 Flow rate (gph) 2 5.46 5.46 5.46 5.46 5.46 3.82 6.65 6.89 Sulfide (mg/L as S-) 0.445 0.185 0.27 0.495 0.74 1.095 1.905 0.205 0.39 0.66 pH 7.19 6.83 6.79 7.03 7.1 7.43 6.9 7.04 7.31 Temperature (C) 24.1 19.4 21. 5 22.9 23.5 20.7 22.8 19 21.2 21.9 ORP (mV) 140 -174 -192 DO (mg/L as O2) 0.6 2.7 0.03 7.07 Sulfate (mg/L as SO4 2-) 0.6 2.4 6.5 0.5 3.8 Chloride (mg/L as Cl-) 235.78 197.25 120.18 123.76 106.42 71.74 193.12 94.86 52.48 Alkalinity (mg/L as CaCO3) 230.00 230.00 240.00 Conductivity ( S/cm) 574 583 584 580 389 524 657 552 506 Turbidity (NTU) 1.36 1.23 0.994 0.802 0.515 3 17.10 2.28 1.94 TOC (mg/L) 0.528 0.54 0.651 0.564 0.429 0.498 0.582 0.496 UV-254 (cm-1) UDL* UDL* 0.045 UDL* UDL* UDL* 0.041 0.0036 0.0136 UDL* UDL*, Under Detection Limit A pp endix B: ( Continued )

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104 Table 22. Anion Exchange Data from Well B Run 1 1 1 1 1 2 2 2 2 Date 11/17/05 11/18/05 11/18/05 11/18/05 11/21/05 11/7/05 11/8/05 11/8/05 11/9/05 Volume 3.775 53.23 11.325 11.88 39 0.82 0.57 19.2 Accumulate Volume (gal) 3.775 57.005 68.33 80.21 119.21 0.82 1.39 20.59 Flow rate (gph) 7.55 7.92 7.92 7.92 7.32 1.37 1.73 5.9 Sulfide (mg/L as S-) 0.376 0.029 0.063 0.147 0. 842 0.188 0.8 0.995 0.075 pH 6.36 6.84 6.91 7.26 6.47 6.27 6.38 Temperature (C) 25.4 21.5 21.7 23.1 24.8 29.3 28.2 24.1 ORP (mV) -200 DO (mg/L as O2) 0.53 0.03 0.05 Sulfate (mg/L as SO4 2-) 0.3 0.3 0.1 1.2 4.8 2.4 6.7 0.5 Chloride (mg/L as Cl-) 173.85 177.71 102.57 94.86 23.58 166.15 171.93 162.29 Alkalinity (mg/L as CaCO3) 260 260 285 250 165 150 140 160 Conductivity ( S/cm) 669 524 520 526 511 760 668 587 Turbidity (NTU) 0.449 0.249 0. 184 0.308 2.04 7.97 2.49 0.087 TOC (mg/L) 0.929 0.415 0.54 0.502 0.565 1.92 0.488 0.462 UV-254 (cm-1) 0.0146 0.0034 0.0096 0.0034 0.006 0.0162 0.012 0.008 A pp endix B: ( Continued )

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105 Table 22. Continued Run 2 2 2 2 2 2 3 3 3 Date 11/9/05 11/10/05 11/11/05 11/12/05 11/14/05 11/16/05 9/30/05 10/3/05 10/5/05 Volume 2.6 32.09 43.71 45 105.46 141.09 30 123 206 Accumulate Volume (gal) 23.19 55.28 98.99 143.99 249.45 390.54 30 153 359 Flow rate (gph) 1.57 2.37 3.28 3.47 3.28 3.28 2.39 3.74 Sulfide (mg/L as S-) 0.074 0.145 0.074 0.046 0. 149 1.415 0.068 0.674 0.74 pH 6.57 6.84 7 7.2 7. 42 7.31 7.16 6.72 6.91 Temperature (C) 23.5 21.9 22. 1 23.2 22.8 25.9 30.6 11.5 18.7 ORP (mV) DO (mg/L as O2) 0.04 0 0 0.16 0 Sulfate (mg/L as SO4 2-) 1 0.3 1.6 9.4 3.5 3.4 2.3 Chloride (mg/L as Cl-) 158.44 69.82 60.18 21. 65 21.65 56.33 21.65 21.65 Alkalinity (mg/L as CaCO3) 150 135 100 225 250 84 106 116 Conductivity ( S/cm) 557 522 496 472 445 483 368 421 412 Turbidity (NTU) 0.185 0.212 0. 157 0.542 0.57 0.457 0.516 0.23 0.378 TOC (mg/L) 0.496 0.422 0. 477 0.52 0.681 0.691 0.564 3.46 UV-254 (cm-1) 0.0056 0.0108 0. 0084 0.0096 0.0064 UDL* 0.017 0.012 UDL*, Under Detection Limit A pp endix B: ( Continued )

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106 Table 23. Anion Exchange Data from Well C Run 1 1 1 1 1 1 1 1 1 1 Date 10/14/05 10/14/05 10/14/05 10/14/05 10/14/05 10/14/05 10/14/05 10/14/05 10/14/05 10/28/05 Volume (gal) 0 Accumulate Volume (gal) 0 0.55 1.1 1.65 2.2 2.75 3.3 4.4 6.6 6.6 Flow rate (gph) 6.79 6.79 6.79 6.79 6.79 6.79 6.79 6.79 6.79 7.09 Sulfide (mg/L as S-) 0.269 0.378 0.424 0.402 0.34 0.348 0.318 0.261 0.152 0.379 pH 6.21 6.26 6.31 6.32 6. 28 6.26 6.23 6.18 6.26 6.94 Temperature (C) 23.9 ORP (mV) DO (mg/L as O2) Sulfate (mg/L as SO4 2-) 1 Chloride (mg/L as Cl-) 143.03 Alkalinity (mg/L as CaCO3) Conductivity ( S/cm) 796 Turbidity (NTU) 0.107 TOC (mg/L) 0.771 UV-254 (cm-1) 0.038 A pp endix B: ( Continued )

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107 Table 23. Continued Run 1 1 1 1 1 1 1 1 1 1 Date 10/28/05 10/28/05 10/28/05 10/28/05 10/28/05 10/28/05 10/28/05 10/28/05 10/28/05 10/28/05 Volume (gal) 3.68 1.23 1.84 0. 61 0.61 1.80 2.45 2.45 3.07 3.07 Accumulate Volume (gal) 10.28 11.51 13.35 13.96 17.03 18.83 21.28 23.73 26.80 29.87 Flow rate (gph) 7.09 7.09 7.09 7.09 7.09 7.09 7.09 7.09 7.09 7.09 Sulfide (mg/L as S-) 0.372 0.248 0.151 0.108 0.073 0.064 0.041 0.036 0.025 0.039 pH 6.62 6.27 6.29 6.2 6. 16 6.19 6.2 6.3 6.36 6.45 Temperature (C) 22 22.9 22. 5 22.9 23.5 23 24.6 25 23.9 24.3 ORP (mV) DO (mg/L as O2) Sulfate (mg/L as SO4 2-) 15 14 54 39 12 7 28 Chloride (mg/L as Cl-) 125.69 143.03 162.29 121.83 148.81 135.32 133.39 Alkalinity (mg/L as CaCO3) Conductivity ( S/cm) 504 522 506 518 516 524 536 533 522 522 Turbidity (NTU) 0.186 0.125 0.139 0.171 0.167 0.091 0.086 TOC (mg/L) 0.632 0.559 0.494 0.527 0.405 UV-254 (cm-1) 0.028 0.028 0.017 0.058 0.068 A pp endix B: ( Continued )

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108 Table 23. Continued Run 1 1 1 1 1 2 2 2 2 2 Date 10/28/05 10/28/05 10/28/05 10/28/05 10/29/05 10/31/05 11/1/05 11/1/05 11/2/05 11/3/05 Volume (gal) 3.07 3.07 4.02 4.91 110 0 27.42 6.09 53.06 26.88 Accumulate Volume (gal) 32.93 39.07 43.09 48.00 158.00 0.00 27.42 33.51 86.57 113.45 Flow rate (gph) 7.09 7.09 7.09 7.09 6.89 2.61 2.40 6.09 2.38 2.49 Sulfide (mg/L as S-) 0.042 0.042 0.055 0.059 1.09 0.023 0.027 0.07 0.365 0.365 pH 6.53 6.79 7.02 7.02 7. 35 6.74 6.6 7.1 7.34 Temperature (C) 24.6 26 26 24.9 22 24 23.9 24.4 21.4 ORP (mV) DO (mg/L as O2) Sulfate (mg/L as SO4 2-) 79 28 79 76 3 35 1.3 20 Chloride (mg/L as Cl-) 125.69 129.54 110.27 98.72 37. 06 137.25 83.30 75.60 Alkalinity (mg/L as CaCO3) Conductivity ( S/cm) 519 525 518 501 410 486 310 416 Turbidity (NTU) 0.096 0.114 0.124 0.096 0.395 0.259 0.453 0.284 0.069 TOC (mg/L) 0.397 0.388 0.98 0.998 0.42 0.556 0.498 1.97 UV-254 (cm-1) 0.047 0.023 0.114 0.04 UDL* UDL* UDL* UDL*, Under Detection Limit A pp endix B: ( Continued )

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109 Table 23. Continued Run 2 Date 11/4/05 Volume (gal) 53.47 Accumulate Volume (gal) 166.92 Flow rate (gph) 2.42 Sulfide (mg/L as S-) 0.574 pH 7.35 Temperature (C) 21.5 ORP (mV) DO (mg/L as O2) 0 Sulfate (mg/L as SO4 2-) 14 Chloride (mg/L as Cl-) 37.06 Alkalinity (mg/L as CaCO3) Conductivity ( S/cm) 392 Turbidity (NTU) 0.054 TOC (mg/L) 0.431 UV-254 (cm-1) 0.02 A pp endix B: ( Continued )

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110 Table 24. Anion Exchange Data from Well D Run 1 1 1 1 1 1 2 2 2 2 Date 9/16/05 9/17/05 9/18/05 9/19/05 9/20/05 9/21/05 10/13/05 10/14/05 10/15/05 10/17/05 Volume (gal) 30 25.74 30.64 30.00 29.36 0 150 150 328 Accumulate Volume (gal) 30 55.74 86.38 116.38 145.74 150 300 628 Flow rate (gph) 7.43 7.99 7.43 Sulfide (mg/L as S-) 0.049 0.03 0.166 0.381 0.462 0.571 0.181 0.839 0.8225 0.842 pH 6.51 6.79 7.02 7. 23 6.63 7.32 7.5 7.52 Temperature (C) 26.7 30. 6 26.1 31 32.4 27.7 24.1 24.5 ORP (mV) DO (mg/L as O2) Sulfate (mg/L as SO4 2-) 0.4 1 0.5 1.4 0.4 3.8 0 Chloride (mg/L as Cl-) 123.76 102.57 58.26 141.10 40.92 17.80 17.80 Alkalinity (mg/L as CaCO3) 50 70 50 70 70 160 200 180 Conductivity ( S/cm) 352 380 378 362 415 469 405 410 Turbidity (NTU) 0.062 0.131 0.117 0.159 0.9 0.09 0.213 0.073 A Color (mg/L Pt.Co) -2 6 -1 1 T Color (mg/L Pt.Co) -1 2 -1 -3 TOC (mg/L) 0.392 0.407 0. 376 0.478 3.26 0.915 0.488 0.709 UV-254 (cm-1) UDL* 0.014 UDL* 0.006 UDL* UDL* UDL* 0.04 UDL*, Under Detection Limit A pp endix B: ( Continued )

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111 Table 24. Continued Run 3 3 3 3 3 4 4 4 4 4 Date 12/7/05 12/8/05 12/9/05 12/10/05 12/12/05 1/17/06 1/18/06 1/19/06 1/20/06 1/23/06 Volume (gal) 0 0 60.22 83.79 128.92 0 64.13 63.55 74.14 244.91 Accumulate Volume (gal) 0 0 60.22 144.01 272.93 0 64.13 127.68 201.82 446.73 Flow rate (gph) 3.14 5.23 5. 22 5.03 5.11 2.76 2.98 3.25 3.6 Sulfide (mg/L as S-) 0 0 0.02 0.002 0.855 0.241 0.012 0.057 0 0.751 pH 7.14 6.74 7.19 7.55 6.55 6.43 7.05 7.36 7.43 Temperature (C) 20.3 22.9 23. 8 21.2 22 24.3 22.1 17.7 19.2 23.4 ORP (mV) 13.29 8.2 0.7 2.15 2.35 0.82 2.09 2.51 1.72 1.68 DO (mg/L as O2) 2 97 137 4 -187 -163 8 -8 114 -108 Sulfate (mg/L as SO4 2-) 0.7 0.5 1.1 1.6 0.7 0 0 2.1 0.9 1.6 Chloride (mg/L as Cl-) 135.32 131.47 110.27 52.48 15.87 225.87 114.13 133.39 131.47 15.87 Alkalinity (mg/L as CaCO3) 200 220 180 160 30 150 55 90 105 170 Conductivity ( S/cm) 510 509 487 417 384 582 465 387 413 395 Turbidity (NTU) 0.095 0.079 0.088 0.063 0.071 0.129 0.137 0.124 0.133 0.187 A Color (mg/L Pt.Co) T Color (mg/L Pt.Co) TOC (mg/L) 0.699 0.434 0. 434 0.838 0.426 0.427 0.428 0.514 UV-254 (cm-1) UDL* 0.009 UDL* 0.014 0.0082 0.001 UDL* UDL* 0.0018 UDL*, Under Detection Limit A pp endix B: ( Continued )

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112 Table 25. Chlorine Demand Test for Raw Water from Well A Date 12/9/2005 12/11/2005 Sulfide (mg/L as S-) 2.65 2.74 pH 7.43 7.46 Temperature (C) 22.4 20.7 DO (mV) 0.60 1.53 ORP (mg/L as O2) -184 -202 Sulfate (mg/L as SO4 2-) 29.5 29.8 Chloride (mg/L as Cl-) 15.87 12.02 Alkalinity (mg/L as CaCO3) 110 200 Conductivity ( S/cm) 465 441 Turbidity (NTU) 0.754 0.198 TOC (mg/L) 2.59 2.68 UV-254 (cm-1) 0.134 0.115 Stock Concentration (mg/L as Cl2) 5000 5100 Contact Time (min) 30 30 Chlorine Concentration (mg/L as Cl2) 30 30 Volume added (mL) 1.76 1.76 Total Chlorine A (mg/L as Cl2) 12.2 12.5 Total Chlorine B (mg/L as Cl2) 13 14 Chlorine Demand A (mg/L as Cl2) 17.8 17.5 Chlorine Demand B (mg/L as Cl2) 17 16 Average Chlorine Demand (mg/L as Cl2) 17.4 16.75 A pp endix B: ( Continued )

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113 Table 26. Chlorine Demand Test for Anion Exchange Effluent from Well A Date 12/9/2005 12/11/2005 Sulfide (mg/L as S-) 0.149 0.027 pH 6.52 6.99 Temperature (C) 22.4 18 DO (mV) 0.46 0.83 ORP (mg/L as O2) 176 164 Sulfate (mg/L as SO4 2-) 0.3 1.9 Chloride (mg/L as Cl-) 177.71 150.73 Alkalinity (mg/L as CaCO3) 110 170 Conductivity ( S/cm) 623 500 Turbidity (NTU) 1.65 9.83 TOC (mg/L) 0.467 0.541 UV-254 (cm-1) 0.008 0.008 Stock Concentration (mg/L as Cl2) 5000 5100 Contact Time (min) 30 30 Chlorine Concentration (mg/L as Cl2) 10 10 Volume added (mL) 0.60 0.58 Total Chlorine A (mg/L as Cl2) 6.2 7 Total Chlorine B (mg/L as Cl2) 7.4 6.5 Chlorine Demand A (mg/L as Cl2) 3.8 3 Chlorine Demand B (mg/L as Cl2) 2.6 3.5 Average Chlorine Demand (mg/L as Cl2) 3.2 3.25 A pp endix B: ( Continued )

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114 Table 27. Chlorine Demand Test for Raw Water from Well B Date 12/11/2005 1/18/2006 Sulfide (mg/L as S-) 1.675 1.475 pH 7.26 7.32 Temperature (C) 18.5 21.8 DO (mV) 1.53 1.37 ORP (mg/L as O2) -187 -241 Sulfate (mg/L as SO4 2-) 6.9 6.7 Chloride (mg/L as Cl-) 15.87 17.80 Alkalinity (mg/L as CaCO3) 210 110 Conductivity ( S/cm) 409 460 Turbidity (NTU) 0.23 1.24 TOC (mg/L) 2.65 2.64 UV-254 (cm-1) 0.137 0.0914 Stock Concentration (mg/L as Cl2) 5100 4200 Contact Time (min) 30 30 Chlorine Concentration (mg/L as Cl2) 30 30 Volume added (mL) 1.76 2.11 Total Chlorine A (mg/L as Cl2) 17.5 13 Total Chlorine B (mg/L as Cl2) 17 15.5 Chlorine Demand A (mg/L as Cl2) 12.5 17 Chlorine Demand B (mg/L as Cl2) 13 14.5 Average Chlorine Demand (mg/L as Cl2) 12.75 15.75 A pp endix B: ( Continued )

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115 Table 28. Chlorine Demand Test for Anion Exchange Effluent from Well B Date 12/11/2005 1/18/2006 Sulfide (mg/L as S-) 0.021 UDL* pH 7.42 6.84 Temperature (C) 16.4 19.7 DO (mV) 0.97 177 ORP (mg/L as O2) 158 7.8 Sulfate (mg/L as SO4 2-) 1.9 0 Chloride (mg/L as Cl-) 131.47 119.91 Alkalinity (mg/L as CaCO3) 170 40 Conductivity (mS/cm) 494 518 Turbidity (NTU) 2.02 0.969 TOC (mg/L) 0.461 0.47 UV-254 (cm-1) 0.009 UDL* Stock Concentration (mg/L as Cl2) 5100 4200 Contact Time (min) 30 30 Chlorine Concentration (mg/L as Cl2) 10 10 Volume added (mL) 0.58 0.7 Total Chlorine A (mg/L as Cl2) 7 7.6 Total Chlorine B (mg/L as Cl2) 7.5 6 Chlorine Demand A (mg/L as Cl2) 3 2.4 Chlorine Demand B (mg/L as Cl2) 2.5 4 Average Chlorine Demand (mg/L as Cl2) 2.75 3.2 UDL*, Under Detection Limit A pp endix B: ( Continued )

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116 Table 29. Chlorine Demand Test for Raw Water from Well D Date 1/20/2006 1/26/2006 Sulfide (mg/L as S-) 0.995 1.08 pH 7.49 7.49 Temperature (C) 22.7 21.6 DO (mV) 1.14 1.25 ORP (mg/L as O2) -112 -113 Sulfate (mg/L as SO4 2-) 0.3 1 Chloride (mg/L as Cl-) 13.94 15.87 Alkalinity (mg/L as CaCO3) 100 110 Conductivity (mS/cm) 394 380 Turbidity (NTU) 0.223 0.174 TOC (mg/L) 3.12 3.35 UV-254 (cm-1) 0.0974 0.086 Stock Concentration (mg/L as Cl2) 4200 4200 Contact Time (min) 30 30 Chlorine Concentration (mg/L as Cl2) 30 30 Volume added (mL) 2.11 2.11 Total Chlorine A (mg/L as Cl2) 18.48 20.24 Total Chlorine B (mg/L as Cl2) 17.8 20.28 Chlorine Demand A (mg/L as Cl2) 11.52 9.76 Chlorine Demand B (mg/L as Cl2) 12.2 9.72 Average Chlorine Demand (mg/L as Cl2) 11.86 9.74 A pp endix B: ( Continued )

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117 Table 30. Chlorine Demand Test for Anion Exchange Effluent from Well D Date 1/20/2006 1/26/2006 Sulfide (mg/L as S-) UDL* 0.065 pH 7.36 7.16 Temperature (C) 19.2 17.5 DO (mV) 1.72 2 ORP (mg/L as O2) 114 -6 Sulfate (mg/L as SO4 2-) 0.9 0.9 Chloride (mg/L as Cl-) 131.47 73.67 Alkalinity (mg/L as CaCO3) 105 55 Conductivity ( S/cm) 413 401 Turbidity (NTU) 0.133 0.065 TOC (mg/L) 0.428 0.405 UV-254 (cm-1) UDL* UDL* Stock Concentration (mg/L as Cl2) 4200 4200 Contact Time (min) 30 30 Chlorine Concentration (mg/L as Cl2) 10 10 Volume added (mL) 0.7 0.7 Total Chlorine A (mg/L as Cl2) 8.42 7.38 Total Chlorine B (mg/L as Cl2) 8.44 7.9 Chlorine Demand A (mg/L as Cl2) 1.58 2.62 Chlorine Demand B (mg/L as Cl2) 1.56 2.1 Average Chlorine Demand (mg/L as Cl2) 1.57 2.36 UDL*, Under Detection Limit A pp endix B: ( Continued )