Bromate Formation and Control During Ozonation of Low Bromide ...

AWWA Microbial/DisinfectionResearch By-Products ResearchFoundation councilBromate Formationand Control DuringOzonation of LowBromide WatersSubject Area:Water Treatment

Bromate Formationand Control DuringOzonation of LowBromide Waters

The mission of the Awwa Research Foundation is to advance the science of water to improvethe quality of life. Funded primarily through annual subscription payments from over 1,000 utilities, consulting firms, and manufacturers in North America and abroad, AwwaRF sponsorsresearch on all aspects of drinking water, including supply and resources, treatment, monitoringand analysis, distribution, management, and health effects.From its headquarters in Denver, Colorado, the AwwaRF staff directs and supports the effortsof over 500 volunteers, who are the heart of the research program. These volunteers, serving onvarious boards and committees, use their expertise to select and monitor research studies to benefit the entire drinking water community.Research findings are disseminated through a number of technology transfer activities, including research reports, conferences, videotape summaries, and periodicals.

Bromate Formationand Control DuringOzonation of LowBromide Waters___Prepared by:Thomas Gillogly, Issam NajmMontgomery Watson, Pasadena, California 91101Roger Minear, Benito Marinas, Mark Urban, Jae Hong Kim, Shinya EchigoUniversity of Illinois at Urbana-Champaign, Urbana, Illinois 61801Gary Amy, Christopher Douville, Brian DawUniversity of Colorado at Boulder, Boulder, Colorado 80309Robert Andrews, Ron HofmannUniversity of Toronto, Toronto, Ontario, M5S 1A4, CanadaandJean-Philippe CroueUniversite de Poitiers, 86022 Poitiers Cedex, FranceSponsored by:Microbial/Disinfection By-Products Research CouncilJointly funded by:Awwa Research Foundation6666 West Quincy AvenueDenver, CO 80235-3098U.S. Environmental Protection AgencyWashington, DC 20460andCalifornia Urban Water Agencies455 Capitol Mall, Suite 705Sacramento, CA 95814Published by theAwwa Research Foundation andAmerican Water Works Association

DisclaimerThis study was jointly funded for the Microbial/Disinfection By-Products Research Council (M/DBP) by the Awwa ResearchFoundation (AwwaRF) the U.S. Environmental Protection Agency (USEPA), and the California Urban Water Agencies (CUWA)under Cooperative Agreement No. CX819540. AwwaRF, M/DBP, USEPA and CUWA assume no responsibility for the contentof the research study reported in this publication or for the opinions or statements of fact expressed in the report. The mentionof trade names for commercial products does not represent or imply the approval or endorsement of AwwaRF, M/DBP, USEPA,or CUWA. This report is presented solely for informational purposes.Library of Congress Cataloging-in-Publication Data has been applied for.Copyright 2001byAwwa Research FoundationandAmerican Water Works AssociationPrinted in the U.S.A.ISBN 1-58321-155-1Printed on recycled paper

CONTENTSLIST OF TABLES......................................................................................................................ixLISTOFnOURES...........................................................................................................-........^!PREFACE ...........................................................................................................................xvFOREWORD ..........................................................................................................................xviiACKNOWLEDGMENTS.........................................................................................................xixEXECUTIVE SUMMARY....................................................................................................... xxiCHAPTER 1. INTRODUCTION................................................................................................ 11.1 Regulatory Background....................................................................................................... 11.2 Ozone Doses for Cryptosporidium Inactivation.................................................................. 11.2.1 Semi-Batch Cryptosporidiumparvum Inactivation..................................................... 11.2.2 Multi-Utility Cryptosporidium Inactivation Study...................................................... 21.3 Ozone Reaction Chemistry Background............................................................................. 31.4 Information Gaps................................................................................................................. 51.5 Project Objectives ............................................................................................................... 61.6 Approach............................................................................................................................. 6CHAPTER 2. MATERIALS AND METHODS.......................................................,.................?2.1 Source Waters ..................................................................................................................... 72.2 Reactors ..............................................................................................................................72.2.1 True-Batch Reactors.................................................................................................... 82.2.2 Semi-Batch Reactor................................................................................................... 112.2.3 Laboratory-Scale Continuous-Flow Ozone Contactor.............................................. 112.2.4 Full-Scale and Pilot-Scale Los Angeles Aqueduct Filtration Plant OzoneContactors.................................................................................................................. 132.2.5 Pilot-Scale Britannia Water Purification Facility Ozone Contactor.......................... 152.3 Calculation of Ozone Contact........................................................................................... 162.4 Analytical Methods........................................................................................................... 162.4.1 Bromide and Bromate................................................................................................ 172.4.2 Organic Bromine .......................................................................................................172.4.3 Total and Dissolved Organic Carbon......................................................................... 182.4.4 Ultraviolet Absorbance.............................................................................................. 182.4.5 NOMFractionation.................................................................................................... 182.4.6 Size Exclusion Chromatography ............................................................................... 192.4.7 Alkalinity...................................................................................................................192.4.8 Ammonia................................................................................................................... 202.4.9 pH ............................................................................................................................202.4.10 Ozone......................................................................................................................... 202.4.11 Cryptosporidium parvum.. .........................................................................................202.4.12 Quality Assurance and Quality Control..................................................................... 212.5 Model Development.......................................................................................................... 25

2.5.1 Cryptosporidiumparvum Inactivation Kinetics ........................................................ 252.5.2 Ozone Decomposition and Bromate Formation Mechanisms................................... 262.5.3 Ozone Contactor Modeling........................................................................................ 29CHAPTER 3. BROMATE SURVEY....................................................................................... 313.1 Participation...................................................................................................................... 313.2 Organization......................................................................................................................323.3 Details of Analyses............................................................................................................ 343.4 Results ............................................................................................................................353.4.1 Individual Survey Rounds ......................................................................................... 353.4.2 Composite Survey Database...................................................................................... 423.5 Discussion .........................................................................................................................453.5.1 United States Bromate Formation Survey................................................................. 453.5.2 Comparison to European Bromate Formation Survey............................................... 45CHAPTER 4. TRUE-BATCH INFLUENCE OF NOM AND TEMPERATURE ONBROMATE FORMATION................................................................................ 494.1 Influence of NOM on Bromate Formation........................................................................ 494.1.1 Source Waters............................................................................................................ 504.1.2 True-Batch Ozonation Experiments.......................................................................... 504.1.3 Results.......................................................................................................................^!4.1.4 Statistical Analysis..................................................................................................... 644.2 Temperature Effects on Bromate Formation and Disinfection......................................... 654.2.1 Temperature Controlled True Batch Ozonation........................................................ 654.2.2 Results........................................................................................................................ 664.2.3 Discussion.................................................................................................................. 674.3 Summary ...........................................................................................................................68CHAPTER 5. EFFECT OF WATER QUALITY AND MINIMIZATION APPROACHESON BROMATE FORMATION......................................................................... 705.1 Bromate Formation ...........................................................................................................705.1.1 Effect of Cryptosporidium Inactivation..................................................................... 705.1.2 Temperature Effects................................................................................................... 735.2 Bromate Minimization...................................................................................................... 755.2.1 pH Depression ...........................................................................................................755.2.2 Ammonia Addition.................................................................................................... 775.2.3 Cumulative Effects of Ammonia Addition and pH Depression................................ 805.2.4 Hydroxyl Radical Scavenger Addition...................................................................... 825.3 Summary........................................................................................................................... 82CHAPTER 6. HYDRODYNAMIC IMPACTS ON BROMATE FORMATION.................... 856.1 True-Batch Staged Ozonation........................................................................................... 866.2 Pilot-Scale Staged Ozonation............................................................................................ 896.3 Co-Current Versus Counter-Current Ozonation ............................................................... 926.4 Summary........................................................................................................................... 95CHAPTER 7. A COMPARISON OF BROMATE FORMATION WITHIN DIFFERENTSCALES OF OZONE CONTACTORS............................................................. 977.1 Los Angeles Aqueduct Filtration Plant............................................................................. 97VI

7.1.1 Testing Plan...............................................................................................................977.1.2 True-Batch Ozone Reactor........................................................................................ 987.1.3 Laboratory-Scale Continuous-Flow Ozone Contactor............................................ 1007.1.4 Full-Scale and Pilot-Scale Ozone Contactors.......................................................... 1017.1.5 Comparison of Full-, Pilot-, and Bench-Scales....................................................... 1057.2 Neuilly sur Marne Water Treatment Plant...................................................................... 1067.3 Britannia Water Purification Facility.............................................................................. 1097.4 Conclusions..................................................................................................................... IllCHAPTER 8. OZONE CONTACTOR MODELING............................................................. 1138.1 Batch and Semi-Batch Reactor Modeling....................................................................... 1138.2 Bench-Scale Flow-through Ozone Contactor Modeling................................................. 1148.3 Pilot-Scale Ozone Contactor Modeling........................................................................... 1188.4 Full-scale ozone contactor modeling............................................................................... 1218.5 Summary......................................................................................................................... 122CHAPTER 9. SUMMARY AND CONCLUSIONS............................................................... 124APPENDIX .......................................................................................................................... 127REFERENCES......................................................................................................................... 147ABBREVIATIONS.................................................................................................................. 153vn

LIST OF TABLESTable 1.1: Proposed CTs Required for the Inactivation of Cryptosporidium parvum oocystsWith Ozone Applied to a Semi-Batch Reactor................................................................... 2Table 1.2: Proposed CTs Required for the Inactivation of Cryptosporidium parvum OocystsWith Ozone Applied to a Continuous-Flow Reactor.......................................................... 3Table 2.1: Source Water Quality Parameters................................................................................. 8Table 2.2: Source Water Quality Parameters After Dilution with Stock Ozone Solution........... 10Table 2.3: Experimental Matrix #1.............................................................................................. 11Table 2.4: Experimental Matrix #2 .............................................................................................. 12Table 2.5: First Round-Robin Results.......................................................................................... 21Table 2.6: Second Round-Robin Results..................................................................................... 22Table 2.7: Third Round-Robin Bromate Results ......................................................................... 23Table 2.8: Third Round-Robin Bromide Results......................................................................... 24Table 2.9: Analytical Method Reporting Levels and Coefficients of Variation.......................... 24Table 2.10: Experimental Quality Control for Laboratory-Scale Continuous-Flow OzoneContactor........................................................................................................................... 25Table 2.11: Ozone Decomposition and Bromate Formation Mechanism.................................... 26Table 3.1: Qualitative Summary of Survey Participants.............................................................. 33Table 3.2: Survey Utility Participant Ozonation Information...................................................... 34Table 3.3: Water Quality and Treatment Condition Summary of Sampling Round One............ 36Table 3.4: Water Quality and Treatment Condition Summary of Sampling Round Two ........... 36Table 3.5: Water Quality and Treatment Condition Summary of Sampling Round Three ......... 37Table 3.6: Pearson Correlation Matrix for Sampling Round One................................................ 38Table 3.7: Pearson Correlation Matrix for Sampling Round Two...............................................39Table 3.8: Pearson Correlation Matrix for Sampling Round Three............................................. 40Table 3.9: Top Five Highest Correlating Parameters to Bromate for Single-LinearRegression Analysis of Round One ..................................................................................41Table 3.10: Top Five Highest Correlating Parameters to Bromate for Single-LinearRegression Analysis of Round Two..................................................................................41Table 3.11: Top Five Highest Correlating Parameters to Bromate for Single-LinearRegression Analysis of Round Three................................................................................ 41Table 3.12: Cumulative Water Quality and Treatment Condition Summary .............................. 42Table 3.13: Cumulative Pearson Correlation Matrix...................................................................44Table 3.14: Top Five Highest Correlating Parameters to Bromate for Single-LinearRegression Analysis of the Cumulative Data.................................................................... 44Table 3.15: Water Quality and Treatment Condition Summary of European Union BromateSurvey................................................................................................................................46Table 3.16: Pearson Correlation Matrix for European Union Bromate Survey........................... 47Table 4.1: NOM Characterization of Raw Source Waters........................................................... 52Table 4.2: Summary of Bromate Formation Potentials and Ozone Exposure Results ................ 56Table 4.3: True-Batch Post-Ozonation Water Quality Parameters.............................................. 59Table 4.4: Estimated Bromate Formation for Cryptosporidium Inactivation (20 C, pH 7)........ 62Table 4.5: Pearson Correlation Matrix for Bromate Formation Potential Experiments .............. 63Table 4.6: Results for True-Batch Ozonation at 10 C................................................................. 66IX

LIST OF FIGURESFigure 1.1: Bromate Formation Pathways.....................:................................................................4Figure 2.1: True-Batch Ozonation Equipment Setup..................................................................... 9Figure 2.2: How-Through Reactor Schematic............................................................................. 13Figure 2.3: Schematic of the Full-Scale Ozone Contactor at the Los Angeles AqueductFiltration Plant................................................................................................................... 14Figure 2.4: Schematic of Pilot-Scale Ozone Contactor at the Los Angeles AqueductFiltration Plant................................................................................................................... 14Figure 2.5: Britannia Water Purification Facility Pilot-Scale Ozone Contactor.......................... 15Figure 3.1: Participation Map for Survey Participants................................................................. 32Figure 3.2: Cumulative Distribution of Bromate Formation in 78 Samples................................ 43Figure 4.1: Source Water Ultraviolet Adsorbance Spectra.......................................................... 53Figure 4.2: Source Water DOC and SUVA Values..................................................................... 53Figure 4.3: Distribution of NOM Fractions ................................................................................. 54Figure 4.4: Size Exclusion Chromatography Chromatograms for CCD Water........................... 55Figure 4.5: Low DOC Source Water Ozone Decay Curves (DOC 3 mg/L)............................. 57Figure 4.7: ASUVA Spectra of Ozonated Project Waters............................................................ 58Figure 4.8: Linear Relationship Between Bromate Formation and Ozone Exposure (LAW)..... 60Figure 4.9: Bromate Formation Potential and Ozone Exposure (20 C, pH 7)............................. 61Figure 4.10: Ozone Exposure versus Bromate Formation Potential for 2-LogCryptosporidium Inactivation at 10 and 20 C .................................................................. 68Figure 5.1: Impact of Ozone Exposure, Expressed as Log-Cryptosporidium Inactivation, onBromate Formation in the Laboratory-Scale Continuous-Flow Ozone Contactor (pH7. 15 C)............................................................................................................................. 71Figure 5.2: Impact of Ozone Exposure, Expressed as Log-Cryptosporidium Inactivation, onBromate Formation in the Laboratory-Scale Continuous-Flow Ozone Contactor (pH8. 15 C)............................................................................................................................. 72Figure 5.3: Impact of Ozone Exposure, Expressed as Log-Cryptosporidium Inactivation, onthe Percent Conversion of Bromide to Bromate (pH 7,15 C).......................................... 72Figure 5.4: Effect of Temperature on Bromate Formation (2-Log CryptosporidiumInactivation, pH 7)............................................................................................................. 73Figure 5.5: Effect of Temperature on Bromate Formation (1-Log CryptosporidiumInactivation, pH 8)............................................................................................................. 74Figure 5.6: Effect of pH on Bromate Formation (2-Log Cryptosporidium Inactivation, 15 C).. 76Figure 5.7: Effect of pH on Bromate Formation (1-Log Cryptosporidium Inactivation, 15 C).. 76Figure 5.8: Effect of pH on TOBr Formation (2-Log Cryptosporidium Inactivation, 15 C)...... 77Figure 5.9: Effect of Ammonia Addition on Bromate Formation (2-Log CryptosporidiumInactivation, 15 C, pH 7).................................................................................................. 78Figure 5.10: Effect of Ammonia Addition on Bromate Formation (1-Log CryptosporidiumInactivation, 15 C, pH 8).................................................................................................. 78Figure 5.11: Effect of Ammonia on Bromate Formation (Ottawa Pilot Plant, 0.5 C, pH 8.5,0.1 mg/L Bf)..................................................................................................................... 80XI

Figure 5.12: Effect of pH Depression and Ammonia Addition on Bromate Formation inCCD (1-Log Cryptosporidiwn Inactivation, 15 C).......................................................... 81Figure 5.13: Effect of pH Depression and Ammonia Addition on Bromate Formation inSPW (1-Log Cryptosporidium Inactivation, 15 C).......................................................... 81Figure 5.14: Effect of a Radical Scavenger (Tertiary Butanol) Addition on BromateFormation in the Laboratory-Scale Continuous-Flow Ozone Contactor (15 C).............. 82Figure 6.1: Impact of Staged Ozonation on Bench-Scale Batch Bromate Formation................. 89Figure 6.2: Ozone Profile Through Britannia Pilot Ozone Contactor During StagedOzonation (pH 8.5, 0.5 C)................................................................................................ 90Figure 6.3: Cumulative CT Through Britannia Pilot Ozone Contactor During StagedOzonation (pH 8.5,0.5 C)................................................................................................ 91Figure 6.4: Bromate Formation Through Britannia Pilot Ozone Contactor During StagedOzonation (pH 8.5, 0.5 C)................................................................................................ 91Figure 6.5: Bromate Formation as a Function of CT(pH 8.5, 0.5 C)..:...................................... 92Figure 6.6: Ozone Profile Versus Contactor Depth for Counter- and Co-Current Operation ..... 93Figure 6.7: Bromate Profile Across Contactor Depth For Counter- and Co-Current Operation. 93Figure 6.8: Calculated Crfor Co-and Counter-Current Ozonation............................................94Figure 6.9: Bromate Concentration as a Function of CT for Co- and Counter-CurrentOzonation..........................................................................................................................95Figure 7.1: Bromate Formation in a True-Batch Reactor (LAW, pH 7, 20 C)........................... 99Figure 7.2: True-Batch Reactor Bromide Reaction and Bromate Formation (LAW, pH 7,20 C)................................................................................................................................. 99Figure 7.3: Bromate Formation in Laboratory-Scale Continuous-Flow Reactor....................... 100Figure 7.4: Bromide Reaction and Bromate Formation in a Laboratory-Scale Continuous-How Contactor................................................................................................................ 101Figure 7.5: Effect of CT Calculation of Bromate Formation Trends......................................... 103Figure 7.6: Los Angeles Aqueduct Filtration Plant Bromate Production.................................. 103Figure 7.7: Los Angeles Aqueduct Filtration Pilot Plant Bromate Production.......................... 104Figure 7.8: CTALL-ISO Development Along Full-Scale Contactor............................................... 104Figure 7.9: CTALL-t50 Development Along Pilot-Scale Contactor.............................................. 105Figure 7.10: Results of Los Angeles Aqueduct Filtration Plant Multiple-Scale ComparisonStudy................................................................................................................................ 106Figure 7.11: Neuilly sur Marne Comparison of Ozone Contactors (May 1998)....................... 108Figure 7.12: Neuilly sur Marne Comparison of Ozone Contactors (October 1998).................. 108Figure 7.13: Britannia Water Purification Facility Ozone Contactor Comparison (October1999, pH 8)...................................................................................................................... 110Figure 7.14: Temperature Effect on Laboratory-Scale Reactors (August 1999, pH 8)............. IllFigure 8.1: Effect of pH on Experimental and Fitted Kinetics of the Inactivation ofCryptosporidiumparvum Oocysts (20 C, Semi-Batch Reactor).................................... 113Figure 8.2: Batch Ozone Decay Kinetics for Selected Natural Waters (pH 7, 20 C)................ 114Figure 8.3: Fitted Batch Reactor Bromate Formation Potential................................................. 115Figure 8.4: Tracer Test Results for the Bench-Scale Flow-Through Reactor andCorresponding ADR Modeling....................................................................................... 116Figure 8.5: Cryptosporidium parvum Inactivation Results and Corresponding ModelPredictions for the Laboratory-Scale Continuous-Flow Ozone Contactor..................... 117xn

Figure 8.6: Bromate Formation and Prediction for the Bench-Scale Flow-Through OzoneContactor (LAW & OTT Spiked to 90 ug/L Br') ............................................................117Figure 8.7: Britannia Pilot Plant Counter-Current Tracer Test and Corresponding ADRModeling (Qwater = 5L/min,Qgas= 1-42 L/min,0.5 C)....................................................119Figure 8.8: Britannia Pilot Plant Measured and Predicted Bromate Formation, Ozone Profileand Cryptosporidium Inactivation (pH 8.2,100 jig/L Br", 2.6 mg/L DOC, 0.5 C,Qwater = 5L/min, Qgas - 1.42 L/min).................................................................................120Figure 8.9: Los Angeles Aqueduct Filtration Plant Tracer Tests and Corresponding ADRModeling (Qwa,er = 85 MOD, Qgas = 17.8 scfh)................................................................121Figure 8.10: Los Angeles Aqueduct Filtration Plant Measured and Predicted Ozone Profile,Bromate Formation and Cryptosporidium Inactivation (pH 8.2, 33 |ag/L Br", 1.9 mg/LDOC, 9 C Q^er = 85 MOD, Qgas = 17.8 scfh)................................................................122xni

PREFACEThe Microbial/Disinfection By-Products Research Council was established in 1995 as avehicle for the selection and funding of research to provide scientific information in the areas ofhealth effects, exposure assessment, risk assessment, and prevention and control ofcontamination by microbes and disinfection by-products in drinking water. The council iscomposed of representatives designated by the U.S. Environmental Protection Agency (USEPA),the Awwa Research Foundation (AwwaRF) Board of Trustees, the Association of State DrinkingWater Administrators, the National Resources Defense Council, the National EnvironmentalHealth Association, or their designees. Sources of funding for this research include the USEPAand AwwaRF, along with other interested parties. The council disburses these funds for researchdeemed to be of the highest urgency and importance in resolving critical research issues indrinking water.xv

FOREWORDThe Awwa Research Foundation is a nonprofit corporation that is dedicated to theimplementation of a research effort to help utilities respond to regulatory requirements andtraditional high-priority concerns of the industry. The research agenda is developed through aprocess of consultation with subscribers and drinking water professionals. Under the umbrella ofa Strategic Research Plan, the Research Advisory Council prioritizes the suggested projectsbased upon current and future needs, applicability, and past work; the recommendations areforwarded to the Board of Trustees for final selection. The foundation also sponsors researchprojects through the unsolicited proposal process; the Collaborative Research, ResearchApplications, and Tailored Collaboration programs; and various joint research efforts withorganizations such as the US Environmental Protection Agency, the US Bureau of Reclamation,and the Association of California Water Agencies.This publication is a result of one of these sponsored studies, and it is hoped that its findings willbe applied in communities throughout the world. The following report serves not only as ameans of communicating the results of the water industry's centralized research program but alsoas a tool to enlist the further support of the nonmember utilities and individuals.Projects are managed closely from their inception to the final report by the foundation's staff andlarge cadre of volunteers who willingly contribute their time and expertise. The foundationserves a planning and management function and awards contracts to other institutions such aswater utilities, universities, and engineering firms. The funding for this research effort comesprimarily from the Subscription Program, through which water utilities subscribe to the researchprogram and make an annual payment proportionate to the volume of water they deliver andconsultants subscribe based on their annual billings. The program offers a cost-effective and fairmethod for funding research in the public interest.A broad spectrum of water supply issues is addressed by the foundation's research agenda:resources, treatment and operations, distribution and storage, water quality and analysis,toxicology, economics, and management. The ultimate purpose of the coordinated effort is toassist water suppliers to provide the highest possible quality of water economically and reliably.The true benefits are realized when the results are implemented at the utility level. Thefoundation's trustees are pleased to offer this publication as a contribution toward that end.Strategies for minimizing bromate formation under ozone dosages capable of inactivatingCryptosporidium remain a challenge. Since the median level of bromide in U.S. drinking watersis approximately 100 ng/L, it is important to know if ozonating natural waters with bromidelevels less than 100 ng/L would form bromate in excess of the 10 jag/L MCL. The datagenerated form this research should help water utilities understand some of the factorscontrolling bromate formation and identify selected methods to minimize its formation.Edmund G. Archuleta, P.E. James F. Manwaring, P.E.Chair, Board of Trustees Executive DirectorAwwa Research Foundation Awwa Research Foundationxvn

ACKNOWLEDGMENTSThe authors would like to recognize the numerous agencies and people that were involved in thisproject. The project would not have been possible without the cooperation and support of thefollowing 13 water agencies that participated in the study:• Alameda County Water District• City of Amarillo• City of Ann Arbor• City of Dallas• City of Fan-field• City of Houston• Compagnie Generale des Eaux• Contra Costa Water District• Los Angeles Department of Water and Power• Metropolitan Water District of Southern California• Municipality of Ottawa• New Jersey American Water Company• Palm Beach County Public Utility DepartmentThe authors would also like to express their gratitude to all of the 24 water agencies thatanonymously participated in the survey of ozonation facilities.The authors also gratefully acknowledge the support and assistance of Kenan Ozekin, AwwaRFProject Officer, and the AwwaRF Project Advisory Committee (PAC): Michael Elovitz(Environmental Protection Agency, Cincinnati, OH); Rengao Song (Louisville Water Company,Louisville, KY); and William Soucie (Central Lake County Joint Action Water Agency, LakeBluff, IL). The contributions of Elaine Archibald, CUWA Project Officer, and the CUWA PAC:Stuart Krasner (Metropolitan Water District of Southern California, La Verne, CA), Susan Teefy(Alameda County Water District, Freemont, CA) and Larry McCollum (Contra Costa WaterDistrict, Concord, CA), are greatly appreciated.xix

EXECUTIVE SUMMARYIn 1992, the Environmental Protection Agency (EPA) initiated a negotiated rulemaking processthat eventually led to the Stage 1 Disinfectants and Disinfection By-Products (D/DBP) Rule(Federal Register, December 16, 1999). Included in the Stage 1 D/DBP rule was a maximumcontaminant level (MCL) for bromate (BrO3~) of 10 ug/L and an MCL Goal (MCLG) of zero.Based on available information, EPA determined that the theoretical 10~4 cancer risk estimate forbromate was 5 ug/L. The MCL of 10 ug/L, therefore, represents a risk level higher than EPA'sapproach of regulating carcinogens within the 10"4 to 10"6 risk range.While the 10 ug/L MCL is anticipated to impact a limited number of water agencies currentlyusing ozone as the primary disinfectant to inactivate Giardia and viruses, a greater number ofwater agencies will be impacted by this MCL when compliance with the Long-Term 2 EnhancedSurface Water Treatment Rule (LT2ESWTR) is required. The agreement in principle for thisrule recommends additional treatment requirements for up to 2.5-log reduction inCryptosporidium, beyond that already required by the Interim Enhanced Surface WaterTreatment Rule. Ozone was one of the treatment tools identified that could be used to inactivateCryptosporidium. While the Cryptosporidium inactivation tables have not yet been establishedby the EPA, preliminary information suggests CT values 5 to 30 times higher than that requiredfor Giardia inactivation will be required depending on the temperature of the water (Renneckeret al 1999; Oppenheimer et al., 2000).To address some of the concerns related to the use of ozone for disinfection, several researchershave examined the influences of water quality and water treatment variables on bromateformation with a focus on process modifications to minimize bromate formation duringozonation (Amy et al., 1997; Glaze et al., 1993; Krasner et al., 1993). However, most of theresearch on understanding bromate formation and control has utilized source waters containingmedium to high levels of bromide (>100 ug/L) ozonated at low to medium Os doses (

• Comparing bench-, pilot- and full-scale bromate formation trends at facilities orparticipating utilities having two or more scales available.BROMATE SURVEYA survey of operating ozone facilities in North America and Europe was initially conducted tounderstand bromate occurrence under current levels of ozone application. The average bromateconcentration at 24 full-scale ozonation plants, based on 78 samples from three separatesampling campaigns for the existing levels of ozonation, was 3.9 ug/L. The average percentconversion of bromide to bromate was 6.7 percent. The 10th, 50th (median), and 90th percentilebromate values was determined to be 0.2, 1.2, and 13 ug/L, respectively. The survey indicatedthat there were some bromate issues with current ozonation practices at the full-scale (whichcurrently target Giardia inactivation). Specifically, several utilities were forming bromate atlevels in excess of the Stage 1 D/DBP Rule MCL of 10 ug/L; 11 percent of the samples analyzedwould be considered out of compliance. Future compliance may be difficult for a greaternumber of utilities when operating at disinfection levels capable of Cryptosporidiuminactivation.BROMATE FORMATION AND MINIMIZATIONThe background natural organic matter of 14 natural waters was characterized by measurementsof the DOC, UV254 absorbance and UV2oo-soo absorbance. The NOM was also fractionated intohydrophobic, hydrophilic and transphilic fraction using macroporous, nonionic resins. Sizeexclusion chromatography was also used to determine the apparent molecular weight of thenatural organic matter. These various parameters were then statistically correlated to bromateformation under a set of standard ozonation conditions (true-batch ozone reactor; temperature =20°C; ozone dose = 1 mg ozone per mg DOC). For the 14 waters studied, the DOCconcentrations ranged from 1.4 to 7.3 mg/L and had a median bromide concentration of 42 ug/L.The SUVA values ranged from 1.4 to 3.8 L/mg-m. The average hydrophobic fraction accountedfor 50 percent of the NOM, with the transphilic and hydrophilic fractions averaging 21 and 29percent of the NOM, respectively. While all of the NOM fractions exerted an ozone demand, thehydrophobic fraction was found to exert the highest demand per unit DOC. Based on thestandard bromate formation testing the hydrophobic fraction was negatively correlated withbromate formation, while the transphilic and hydrophilic fractions were positively correlated.Bromate formation in these waters was evaluated over a range (0.5-log to 3.0-logs) of predictedCryptosporidium inactivation levels. At 1-log Cryptosporidium inactivation, approximately halfof the waters were expected to produce bromate in excess of 10 ug/L. It was noted that whilethese waters had a range of water qualities and bromide concentrations, the higher theconcentration of bromide the higher the percent of the bromide that was converted to bromate.To reduce the concentration of bromate formed, pH depression, ammonia addition and hydroxylradical scavenger addition were evaluated. By depressing the pH from 8 to 7 to 6, a generalreduction in bromate formation of 30 to 50 percent per unit decrease in pH was observed. Thisreduction in bromate formation resulted in an increase in the concentration of total organicxxn

omide formed. The addition of 0.5 mg/L ammonia-nitrogen to these waters resulted in areduction in bromate formation for all of the waters that would normally form over 10 ug/L ofbromate. Increasing the ammonia concentration to 1.0 mg/L ammonia-nitrogen resulted in someadditional reduction in bromate formation. It was estimated that ammonia addition might be aneffective bromate formation control strategy for those waters within 10 to 20 |ig/L of the MCL.It was also revealed that the cumulative effects pH depression together with ammonia additioncould be used for waters in which bromate formation was particularly problematic.A preliminary investigation of the addition of a hydroxyl radical scavenger revealed the additionof 1 mM of t-butanol prevented bromate formation. While the addition of t-butanol to municipaldrinking water supply might not currently be an acceptable practice, it does illustrate theeffectiveness of this approach. This illustrates the need for additional research to identify anacceptable hydroxyl radical scavenger and determine the minimum amount necessary toeffectively inhibit bromate formation. It was just as important to note that since the addition of ahydroxyl radical scavenger completely inhibited bromate formation, it appeared that bromateformation in natural waters does not proceed through the "direct pathway" as discussed by Songet al. (1997), but must proceed through pathways in which hydroxyl radicals are needed.Consequently, the radical scavenging by natural organic matter likely plays a significant role inthe differences observed in bromate formation between natural waters.The temperature was observed to reduce bromate formation in true-batch, semi-batch andcontinuous-flow laboratory reactors. However, its impacts on the amount of bromate formed fora given level of Cryptosporidium disinfection varied between these reactors. In the true-batchexperiments, decreasing the temperature from 20°C to 10°C resulted in about a 40 percentreduction in the bromate formed for 2-logs of Cryptosporidium inactivation. Using thelaboratory-scale continuous flow reactor, decreasing the temperature from 25°C to 5°C, resultedin a 15 to 72 percent increase in the amount of bromate formed for 2-logs of Cryptosporidiuminactivation. An approximate 50 percent increase in the amount of bromate formed for 2-logs ofCryptosporidium inactivation was also observed in a semi-batch reactor as the temperature wasdecreased from 22°C to 7°C. It is unclear why different results were observed for these differentreactors.HYDRODYNAMIC IMPACTSIn addition to chemical approaches to bromate minimization, hydrodynamic strategies were alsoinvestigated. However, through bench-scale and pilot-scale experiments, no compelling reasonwas identified to employ staged/tapered ozonation for bromate minimization. It was alsodiscovered that bromate formation could not be reduced by operating the ozone contactors ineither a co-current or counter-current mode. Nevertheless, the operation of the ozone contactorin a co-current mode might have provided subtle opportunities for optimizing disinfection.These tests provided additional indications that bromate formation in natural waters ispredominantly controlled by chemical conditions and not hydraulic parameters.xxin

COMPARISON BETWEEN REACTOR SCALESMany of the bromate formation trends were developed through bench-scale tests. Concerns overthe applicability of these results to larger scale (pilot-scale and full-scale) reactors wereaddressed through a series of comparability tests. It was shown that bench-scale reactors couldprovide reasonable simulations of pilot-scale and full-scale bromate formation results providedan accurate estimate of the amount of ozone contact at the larger scale could be generated. Assuch, the approximation of ozone contact by CT, as defined by the SWTR, resulted in a lack ofcomparability. By calculating ozone contact with the hydraulic retention time instead of tio, andby giving credit to the first cell of the pilot-scale and full-scale reactors correlations to the benchscaleresults could be developed. Likewise, pilot-scale simulations could be used to provideapproximations of full-scale results. Such simulations could be useful in assessing tradeoffsbetween bromate formation and disinfection (CT) under various scenarios. However, theseresults also illustrated that while the simulations could be used for trending purposes, the specificbromate concentrations formed for given amounts of ozone contact do not always match betweendifferent contactors. The results from these tests also lent additional credence to the theory thatchemical conditions, as opposed to hydraulic conditions, control the formation of bromate.INTEGRATED MODELThe results of these reactor scale comparability tests were also used to validate the performanceof a series of integrated models. These models could be used to predict ozone decomposition,bromate formation and Cryptosporidium inactivation, and were presented for four different typesof reactors: true-batch ozone reactor, laboratory-scale continuous-flow ozone contactor withinternal recirculation, pilot-scale ozone contactor and full-scale ozone contactor. Profiles ofozone concentration, bromate formation and Cryptosporidium inactivation through the BritanniaWater Purification Facility pilot-scale ozone contactor and the Los Angeles Aqueduct FiltrationPlant full-scale ozone contactor revealed similar trends to the experimental data. It wasrecognized that while limitations existed, the model simulations could be used to understand theperformance of the ozone contactors at various configurations and operating conditions.xxiv

CHAPTER 1. INTRODUCTION1.1 REGULATORY BACKGROUNDIn 1992 the Environmental Protection Agency (EPA) initiated a negotiated rulemaking processthat eventually led to the proposed Stage 1 Disinfectants and Disinfection By-Products (D/DBP)Rule (Federal Register, July 29 1994). Included in the proposed Stage 1 D/DBP rule was aproposed maximum contaminant level (MCL) for bromate (BrCV) of 10 ug/L and an MCL Goal(MCLG) of zero. Based on available information, EPA determined that the theoretical 10cancer risk estimate for bromate was 5 ug/L. The proposed MCL of 10 ug/L, therefore,represented a risk level higher than EPA's approach of regulating carcinogens within the 10"4 to10"6 risk range. In part, this decision was driven by available analytical methods that EPAconsidered, which had a practical quantification limit (PQL) of 10 |ig/L. In the preamble to theproposed Stage 1 D/DBP Rule, EPA requested public comment on whether the PQL for bromatecould be lowered and whether a lower MCL could be established, hi 1997, EPA formed a newAdvisory Committee and the consensus from that committee was that there was no newinformation currently available to justify lowering the MCL. Consequently, the final bromateMCL was promulgated at 10 ng/L (Federal Register, December 16,1999).While the 10 |ng/L is anticipated to impact a limited number of utilities currently using ozone asthe primary disinfectant to inactivate Giardia and viruses, a greater number of utilities will beimpacted by this MCL when compliance with the Long-Term 2 Enhanced Surface WaterTreatment Rule (LT2ESWTR) is required. In September 2000, an EPA Federal AdvisoryCommittee signed an agreement in principle for recommendations of the LT2ESWTR. In thisagreement, additional treatment requirements for reductions in Cryptosporidium are identified.Beyond the Cryptosporidium reduction requirements identified in the Interim Enhanced SurfaceWater Treatment Rule, up to an additional 2.5-logs of Cryptosporidium reduction may berequired based on source water monitoring. Ozone was one of the treatment tools identified thatcould be used to inactivate Cryptosporidium. While the Cryptosporidium inactivation tableshave not yet been established by the EPA, preliminary information suggests CT values 5 to 30times higher than that required for Giardia inactivation will be required (Rennecker et al. 1999;Oppenheimer et al., 2000).1.2 OZONE DOSES FOR CRYPTOSPORIDIUM INACTIVATION1.2.1 Semi-Batch Cryptosporidium parvum InactivationThe kinetics of Cryptosporidium parvum inactivation with ozone have been investigated byseveral research groups (Peeters et al., 1989; Perrine et al, 1990; Korich et al., 1990; Finch etal., 1993; Liyanage et al, 1997; Rennecker et al, 1999) in batch or semi-batch reactors. Untilrecently, there has been lack of consistency among the various results reported presumably due

to disparities in the methods used to assess oocyst viability. In-vitro excystation methods havetypically produced slower inactivation rates than those based on animal infectivity assays (Finchet al., 1993; Owens et al., 1994). However, a modified in-vitro excystation approach based onsporozoites enumeration has been shown to be consistent with animal infectivity data presentedin the literature for the same C. parvum strain (Rennecker et al., 1999). The CTs required for0.5-log to 3-logs inactivation of Iowa strain C. parvum oocysts in distilled-deionized water forthe temperature range from 0.5°C to 30°C obtained by modified in-vitro excystation (Renneckeret al,. 1999) are presented in Table 1.1.Table 1.1: Proposed CTs Required for the Inactivation of Cryptosporidium parvum oocystsWith Ozone Applied to a Semi-Batch ReactorTemperature(°C)-Log(AWV0)0.51.01.52.02.53.00.51932445668805111825313845Source: Adapted from Rennecker et al., 199910 15 20CT [mg-min/L]5.9 3.2 1.89.5 5.2 2.913 7.3 4.117 9.3 5.221 11 6.324 13 7.51.2.2 Multi-Utility Cryptosporidium Inactivation StudyOppenheimer et al. (2000) have extended the Cryptosporidium inactivation findings of otherresearchers obtained for ozone in laboratory-grade water and static- or semi-batch reactors, tonatural water conditions. For this study, sixteen different North American and European naturalwaters were seeded with viable Cryptosporidium parvum (C. parvum) oocysts. Inactivation wasthen measured by animal infectivity following the application of different disinfectants ordisinfectant combinations. The results presented here focus on the ozone disinfection portion ofthe study. All of the C. parvum inactivation experiments by ozone were conducted using atemperature controlled continuous flow contacting system that was designed to simulate thehydraulic conditions of full-scale ozone contacting systems.Analysis of data from these experiments showed that modeling the results by the linear ChickWatson model, the non-linear Chick Watson model or the Horn model, yielded similar modelfits. As a result the simple, one-parameter, linear Chick Watson model was used to compare theresults obtained for each of the water sources. Using the linear Chick Watson inactivationconstants derived for several of the project waters at more than one experimental temperature, itwas calculated that the CT requirements more than quadrupled (4.6 multiplier) for every 10°Cdecrease in temperature. This impact of temperature on ozone inactivation of C. parvum may beseverely underestimated if the temperature corrections used for the ozone inactivation of Giardialamblia are used (i.e. a doubling of the CT requirements for every 10°C decrease in temperature).The results obtained were used to generate a set of CT values for Cryptosporidium parvuminactivation between 0.5-log and 3.0-logs at temperatures ranging from 1 to 30°C (see Table1.2).251.01.72.33.03.64.3300.61.01.41.72.12.5

Table 1.2: Proposed CTs Required for the Inactivation of Cryptosporidium parvum OocystsWith Ozone Applied to a Continuous-Flow ReactorTemperature(°C)-Log(AWVo)0.51.01.52.02.53.0. 111213242536355.71117232934Source: Adapted from Oppenheimer et al., 200010 15 20CT [mg-min/L]2.7 1.2 0.65.3 2.5 1.28.0 3.7 1.711 5.0 2.313 6.2 2.916 7.5 3.5Obvious differences exist between the data presented in the literature, and numerous hypotheseswhy these differences exist. As the specific levels of ozone CT required to achieve a specificlevel of Cryptosporidium inactivation was not the focus of this study, the differences between theproposed data presented above and in the literature will not be debated here. For the purposes ofthis study, a range of CT values will be used to illustrate the impacts of the increased levels ofozone exposure. Additionally, the modeling efforts presented in this study utilized the highervalues proposed by Rennecker et al. (1999) as a conservative estimate of the levels of CTrequired for Cryptosporidium inactivation.1.3 OZONE REACTION CHEMISTRY BACKGROUNDThe move to non-chlorine disinfection processes has not eliminated the production ofhalogenated by-products. Much of the recent attention has focused on the presence of bromateion resulting from alternative disinfection processes, including but not limited exclusively toozonation (Siddiqui et al., 1995). Considerable effort has been directed towards investigatingbromate formation during the ozonation of bromide (Br~) containing waters. A number ofmodels have been proposed for the corresponding reaction mechanisms (Yates and Stenstrom,1993; von Gunten andHoigne, 1993, 1995; Westerhoff, 1995; Song, 1996; Song et al, 1997).Bromate, formed during the ozonation of source waters containing bromide ion (bromide), hasbeen reported to be affected by both water quality and treatment conditions. The water qualityconditions that have been reported as having either a positive or negative effect on bromateformation have included: natural organic matter (NOM); bromide; pH; carbonate alkalinity;temperature; and ammonia-nitrogen (NHs-N). Influential treatment conditions include:transferred ozone (Os) dose; hydraulic residence time (HRT); dissolved ozone residual (DOs);CT; acid addition; and ammonia addition.Bromate formation has been well defined in laboratory water (Milli-Q water: deionized, carbonfiltered,0.45 um filtered water) by recent efforts. These studies have shown that bromateformation resulted from a complex combination of molecular ozone and free radical mechanismsinitiated by the hydroxyl radical (-OH) formed through ozone decomposition. Experimentalresults were explained quite well with a deterministic modeling approach (Song, 1996). Asshown in Figure 1.1, Song et al. (1997) identified three distinct pathways with prominent250.30.50.81.11.41.6300.10.30.40.50.60.8

contributions to bromate formation in laboratory water. These pathways included a truemolecular ozone route and two combination pathways, one initiated by molecular ozone and theother initiated by the hydroxyl radical.OBrVHOBr < °3— Br" ——^1—* OBrVHOBrOH I OHOBr . Br BrO2"Disproportionation Q3BKV OBr Br°BrOs" Br02-DisproportionationBrO3'Direct/Indirect Indirect/Direct DirectPathway Pathway PathwaySource: Song et al. 1997. Reprinted from Journal AWWA, Vol. 89, No. 6 (June 1997), bypermission. Copyright ©1997, American Water Works AssociationFigure 1.1: Bromate Formation PathwaysThe deterministic approach has been complicated in natural waters by the presence of organicsubstances. Organic compounds become involved in the ozone and free radical reactions, as wellas the bromine reaction pathway through the formation of organic bromine compounds.Consequently, in addition to bromate formation concerns, the background organic substancesmay also provide a sink for bromide. Based on results with radical scavengers in the presence ofNOM, the true molecular ozone pathway loses significance or is eliminated (Song, 1996).Several researchers have recently examined the influences of water quality and water treatmentvariables on bromate formation with a focus on process modifications to minimize bromateformation during ozonation (Amy et al., 1997; Glaze et al., 1993; Krasner et al., 1993). Thiswork has led to the observation that in many cases, there is a trade-off between bromatereduction and increases in total organic bromide (TOBr) formation. Furthermore, thecomposition of the TOBr formed has been poorly characterized which has hampered efforts toassess the toxicity of this group of brominated DBFs (Bull et al., 1995). It has beendemonstrated by Song (1996), that TOBr may form rapidly from hypobromous acid (HOBr). Inaddition, the production of HOBr from ozonation is also rapid and the resultant HOBr can persistlong after the ozone has dissipated. This has been indirectly demonstrated through the cessationof bromate formation with the depletion of the residual ozone concentration, while TOBrcontinues to form thereafter (Westerhoff, 1995; Song, 1996).

1.4 INFORMATION GAPSUntil now, an ozone dose of 1 mg Os for every mg dissolved organic carbon (DOC) hasgenerally been accepted by the water industry as an upper limit for meeting Giardia and virusinactivation requirements under the Surface Water Treatment Rule. At these ozone doses, waterswith low concentrations of bromide (e.g. < 50 ug/L) generally would meet a 10 ug/L bromateMCL. However, most of the research on understanding bromate formation and control hasutilized source waters containing medium to high levels of bromide (>100 |o.g/L) ozonated at lowto medium Oa doses (

1.5 PROJECT OBJECTIVESThe primary objective of this research was to evaluate the formation of bromate and the efficacyof control strategies for low to moderate (

CHAPTER 2. MATERIALS AND METHODSTo accomplish the objectives of the research, many analytical methods and experimentalprocedures were employed. Analytical methods were used to assess organic and inorganic waterquality parameters. Experimental procedures were used to operationally characterize NOM, andevaluate bromate formation under true-batch ozonation, staged ozonation, and temperaturecontrolledozonation conditions. During the course of research, the methods and procedureswere subjected to quality control to identify variability/error within the analytical andexperimental results.2.1 SOURCE WATERSFourteen different North American and European natural water sources were utilized for thebench-scale, pilot-scale and full-scale tests performed as a part of this study. These surfacewater, groundwater, and surface/groundwater mixed sources included the following:• Lake Houston (HOU), Houston, Texas• Colorado River (CRW), La Verne, California• Los Angeles Aqueduct (LAW), Los Angeles, California• Marne River (CGE), Paris, France• Delaware River (NJA), New Jersey• Lake Meredith and Ogallala Aquifer mix (AMA), Amarillo, Texas• Trinity River-Ehn Fork (DAL), Dallas, Texas• State Project (SPW), La Verne, California• Sacramento River (SAC), California• Sacramento/San Joaquin Delta (CCD), Concord, California• Huron River (ANN), Ann Arbor, Michigan• Ottawa River (OTT), Ottawa, Canada• South Bay Aqueduct (ACD), Fremont, California• Floridian Aquifer (WPB), West Palm Beach, FloridaSource water quality parameters are summarized in Table 2.1. All waters were untreated, exceptfor the DAL and OTT samples, which were taken immediately prior to the point of intermediateozonation within municipal drinking water treatment facilities.2.2 REACTORSThroughout this study, several different types and scales of reactors were utilized. A descriptionof each type of reactor and its operation is given below.

Table 2.1: Source Water Quality ParametersIDBromideAmbientpHAlkalinity(mg/L as CaCO3)Ammonia-N(mg/L)DOC(mg/L)UVA254(cm" 1 )SUVA(L/mg-m)AMAWPBSPWCRWANNACDCCDLAWCGEHOUNJADALOTTSACMeanMedianStd DevRange200170145726555393323212121178.26436628.2 - 2007.97.07.48.18.47.58.17.97.57.36.98.16.17.07.57.50.66.1 - 8.41832307213033151821102102838754567104796728 - 2300.020.770.030.060.140.070.060.070.010.20.230.530.060.090.170.070.220.01 - 0.772.810.42.82.72.53.31.81.91.59.43.04.42.61.73.62.82.81.5 - 10.40.0400.3900.0670.0440.0480.0710.0620.0440.0370.3300.0800.0890.0560.0440.1000.0590.1120.037 -0.3901.43.82.41.61.92.23.42.32.53.52.72.02.12.62.52.40.71.4-3.82.2.1 True-Batch Reactors2.2.1.1 True-Batch OzonationThe true-batch ozonation procedure consisted of the transfer of an aliquot of ozone stock solutioninto a completely-mixed batch reactor, resulting in a 100 percent transfer efficiency of aqueousozone to the sample. The addition of ozone stock, however, incurs a dilution of the originalsample and alters the concentrations of the solutes in the sample. This batch reactor simulatesthe conditions of a plug-flow reactor (PFR). By modeling kinetic data derived from the truebatchreactor over time, concentration versus distance profiles for plug-flow reactors could bedeveloped.The true-batch reactor consisted of a 500-mL glass graduated cylinder fitted with a glasssampling port at the bottom (Figure 2.1). Experiments were carried out by initially buffering(1.0 mM PC'43-) and adjusting the pH of a natural water sample to 7.0 ±0.1. Calculated volumesof the prepared natural water and ozone stock solution were sequentially added to the reactor.Ozone stock was transferred to the reactor via a glass pipette and nalgene tubing. The totalvolume added to the reactor was 500 mL, with an ozone to DOC dose of Img O3/mg DOC. Anadjustable Teflon disc was then placed on the top of the water surface to prevent gas transfer at

the air-water interface (i.e., no headspace). Ozone decomposition kinetics were monitored byanalyzing aliquots of the solutions for the residual dissolved ozone concentration atpredetermined times. A magnetic stir bar and plate were used to provide continuous mixing ofthe ozonated sample.Teflon DiskOzone StockRaw Water Sample(adj usted/bufferedto pH = 7.0)Stir BarFigure 2.1: True-Batch Ozonation Equipment SetupOnce the measured ozone concentrations were observed to decay below 0.05 mg/L, the Teflondisc was removed from the reactor and the sample was allowed to rapidly mix for a period of 5to 10 minutes to dissipate the remaining residual ozone concentration. Aliquots of the ozonatedsample were then collected in 40-mL amber vials, labeled and stored at 4°C until they wereanalyzed for bromate concentration.While the majority of these tests were performed at 20°C, selected true-batch experiments wereperformed at 10 ± 1°C to assess the effects of low temperature on bromate formation. For theseexperiments, the temperature was controlled by recirculating chilled water through a water jacketsurrounding the glass reactor.The addition of the ozone stock solution to samples of natural water resulted in dilutions of theoriginal water quality parameters summarized in Table 2.1. The indicated dilution percentagesand "diluted" water quality characteristics are summarized in Table 2.2 for bromide, DOC,ammonia, and alkalinity. The parameter pH was not shown since all true-batch ozonation

experiments were performed at a constant buffered pH (7.0 ±0.1). Subsequent data analyseswere based on these diluted water quality characteristics.Table 2.2: Source Water Quality Parameters After Dilution with Stock Ozone SolutionIDAMAWPBSPWCRWANNACDCCDLAWCGEHOUNJADALOTTSACMeanMedianStd DevRangeBromide Alkalinity Ammonia(ug/L) (mg/L as CaCO3) (mg/L)182119131666048373022151818154758425115-182 167161651203013277101200203365416391715720 - 200 0.020.540.030.060.130.060.060.060.010.140.200.460.050.080.140.0630.160.01 - 0.54* Based on assumption of Beer's Law applicabilityDOC(mg/L)2.557.282.522.482.312.881.701.751.436.772.643.782.341.603.02.51.81.4-7.3UVA254(cm' 1 )*0.0360.2730.0600.0400.0440.0620.0590.0410.0350.2340.0700.0760.0500.0410.0800.0600.0720.036 - 0.273Dilution(%)8.730.09.77.77.713.06.18.24.828.013.013.08.96.0129.37.54.8 - 30Ozone stock solutions were prepared in Milli-Q water. To do this, a stream of ozone gasgenerated (OREC: Model O3V5-O, Phoenix, AZ) from medical grade oxygen, was continuouslypassed through ice-cooled Milli-Q water for a minimum of 120 minutes. The resultant aqueousozone concentrations ranged from 20 to 35 mg/L.2.2.1.2 Staged-Batch OzonationStaged true-batch ozonation consisted of applying aliquots of ozone stock solution in two stagesto assess the difference in bromate formed as compared to the single-stage true-batch ozonationexperiments. In this procedure, an aliquot of ozone stock solution was added to the sampleduring the first stage at a 0.5:1 ozone to DOC mass ratio. As in the procedure described above,ozone decay was tracked using ozone residual measurements at timed intervals. Once the ozoneresidual had decayed to below detection limits, the sample was allowed to continue to react for aperiod of 5 to 10 minutes before the samples were collected in 40-mL amber vials.10

For the second stage, the new DOC concentration was calculated based on the diluted DOC ofthe sample after the addition of ozone stock in stage one. An aliquot of ozone stock solutionswas once again added at a dose of 0.5:1 ozone to DOC (mg/mg). As with the first stage, ozoneresiduals were recorded over time. Once the system had been allowed to react for 5 to 10minutes after the ozone residual had decayed to below detection limits, samples were collected inamber vials, labeled and stored at 4°C until the bromate analyses could be performed.2.2.2 Semi-Batch ReactorThe inactivation kinetics of C. parvum oocysts and selected bromate formation results withOttawa River water were determined by performing semi-batch experiments. Similar proceduresto those described by Hunt and Marinas (1997) were followed. A reactor containing 200 mL of0.01M phosphate buffer solution at pH 6.5, 7.5, or 8.5 was immersed in a 20°C water bath. Aconcentration of dissolved ozone inside the reactor was kept constant by continuous bubbling ofozone gas. The ozone gas, generated (PCI Ozone Corp: Model GL-1, NJ) from 99.9% pureoxygen, was passed through an 8-L reservoir bottle to dampen any fluctuations in ozoneconcentration during the experiment. When the dissolved ozone concentration inside the reactorreached a steady value of about 0.5 mg/L, approximately 7xl05 oocysts were injected. Eachinactivation experiment was stopped after a predetermined contact time to target a specific CTvalue by adding a 2-mL aliquot of a 1.67 percent (w/v) sodium thiosulfate solution to the reactor.This procedure was repeated at various CTs to cover an inactivation range between 0 and 99.5percent.2.2.3 Laboratory-Scale Continuous-Flow Ozone ContactorA number of experiments were performed on each source water in a laboratory-scale continuousflowozone contactor to develop an orthogonal matrix to evaluate bromate formation under avariety of pH, temperature and ammonia conditions. This same contactor was used in a limitednumber of C. parvum inactivation experiments. A subset of radical scavenger additionexperiments was completed using two concentrations of tertiary butanol. Two slightly differentorthogonal matrices were employed. The first matrix, as shown as Table 2.3, was used for LakeHouston water (HOU), Los Angeles Aqueduct water (LAW), Delaware River water (NJA),Trinity River water (DAL), Sacramento/San Joaquin Delta water (CCD), Huron River water(ANN), Ottawa River water (OTT), and Floridian Aquifer water (WPB). The correspondingmatrix for Colorado River water (CRW), State Project water (SPW), Sacramento River water(SAC), and South Bay Aquifer water (ACD) is listed in Table 2.4.Table 2.3: Experimental Matrix #1Parameter_________________Value (* denotes baseline value)______pH 6, 7*, 8Temperature 5,15*,25°CAmmonia Ambient*, 0.5,1.0 mg/L-NLog Inactivation_____________1,2*, 3 log__________________________11

Table 2.4: Experimental Matrix #2Parameter________________Value (* denotes baseline value)pH 6, 7, 8*Temperature 5,15*, 25°CAmmonia Ambient*, 0.5, l.Omg/L-NLog Inactivation_____________0.5, 1.0*, 1.5 log_________2.2.3.1 Sample PreparationFor all of these tests, each natural water sample was initially adjusted to the desired temperature,and then pH. For the two ammonia addition experiments with each water, enough ammoniumchloride (NILjCl) was added to achieve total ammonia concentrations of 0.5 and 1.0 mg/L as N.The ammonia concentration was measured immediately before ammonia addition by the methoddescribed in Section 2.4.8. For the radical scavenger addition experiments, tertiary butanol wasadded to achieve concentrations of 1 or 3 mM.2.2.3.2 ApparatusThe continuous-flow ozone contactor consisted of several components: bubble contactor, simpledosing column, ozone generator, sample feed pump, sample recirculation pump, water bath,back-flow catch flask, and KI trap. A schematic of the system is shown in Figure 2.2. Thecontactor was 1.2m long and had an inner diameter of 0.02 m. The contactor column andinternal recirculation line had volumes of 440 mL and 85 mL, respectively. A water jacketsurrounding the contactor was used for temperature control. A glass-frit gas-diffuser placed atthe bottom of the contactor was secured in place by a plastic fitting with a Teflon o-ring.Another glass elbow fits into the top of the column. This elbow simply accepts the off-gas fromthe column. The simple dosing column was a 1.2-m long glass tube with an inner diameter of0.02 m. A glass diffuser and off-gas elbow identical to those for the contactor column fit into thebottom and top of the simple column. The simple dosing column was used only for calibrationof the system.In this reactor bulk, undiluted water samples were continuously passed through and ozonated bya co-current stream of bubbles created by a frit at the base of the contactor. The ozonated waterwithin the contact column was recirculated at a rate approximately ten times the sample feedrate. A flow meter was used to regulate the amount of ozone gas that entered the contactor fromthe ozone generator. Water was pumped into the bottom of the reactor and exited at the top.The system was allowed to stabilize in terms of experimental temperature and liquid and gaseousflow rates. It was determined that true system stability had been achieved once the ozoneconcentration at each of three sample ports along the length of the column was the same andconstant (stable) with time. Once the ozone residual had stabilized, an aliquot of the ozonatedwater sample exiting the reactor was quenched with sodium thiosulfate (two times the theoreticalstoichiometric amount) and stored in the dark at 4°C until the bromate analyses could beperformed.12

——— Liquid Flow•—••••• Gas FlowO Two way valveO Three way valveI Gas sampling portQ.,Ozone Exhaust KITraplie ^•m........... .1^Water BathtSampleFeed Pump npSampleReservoir"5 -: rS-*-* •*g \t— l ts *il———— !". §feKO ^; ,Q^ ft-.-I' |iri:;l1 "' " •t- •~!- .'T^*$"'$?•':"*iI^''"-

with the full-scale contactor, ozone gas was introduced into the first cell and traveled upwards,counter-current to the flow of the water. The height of the columns was much greater than thecolumn's diameter, creating near plug-flow hydrodynamics.CelllCell 2 Cell 3Cell 4Rapid MixersContactor"Influent.* .v'~y-v'.'«..;-. .•'?*!• :•rf .""' •"' I*."- •' .'-;!.' '•'"•••'-•'«> £ .' 7 ;.•._'.-• •':''.'};.-TapC>TapF4 iL b»PaF >GrhTap!i»&&&&?Tap A4TapDOzone IntroductionContactorEffluentFigure 2.3: Schematic of the Full-Scale Ozone Contactor at the Los Angeles AqueductFiltration PlantContactorInfluent«»« >i>^ 1-ContactorEffluent/ ^\/\ /te e0 »°.rn< >Ozone Introductioni»« >4 >•Sample TapLocationFigure 2.4: Schematic of Pilot-Scale Ozone Contactor at the Los Angeles AqueductFiltration Plant14

For both the full- and pilot-scale contactors, the tio/tso ratio was provided as information aboutthe hydrodynamics of the contactors. Because an ideal plug-flow reactor (PFR) has a tio/tso ratioof 1.0, it was determined that the pilot-scale system was hydraulically similar a PFR (tio/tso of0.87 based on tracer study information). The full-scale contactor, however, hydraulicallybehaved more like a continuous-stirred tank reactor (CSTR) with a tio/tso of 0.49.2.2.5 Pilot-Scale Britannia Water Purification Facility Ozone ContactorPilot-scale experiments were also conducted at the Britannia Water Purification Facility (Ottawa,Canada). The ozone contactor consisted of three glass columns operated in series (3 m high and0.15 m diameter). Ozone could then be selectively applied to either, or both, of the first twocolumns, as shown in Figure 2.5. The water used was plant clarified (alum and activated silicacoagulation, fiocculation, and sedimentation) to represent mid-train ozonation. Experimentswere conducted at both the ambient pH (6.1), and at pH 8.5. Elevating the pH to 8.5 wasachieved by adding a caustic (NaOH) solution via a peristaltic pump to the feed linesimmediately upstream of the contactor. The alkalinity of the pH 8.5 experiments was alsoincreased from the ambient 10 mg/L to 75 mg/L as CaCOs using NaHCOs. CT values rangingfrom 3 to 45 mg-min/L were obtained by varying the water flow rate (8 and 5 L/min) and ozonegas concentration (0.45 to 2.09 % by weight). Ozone was produced from pure oxygen using aModel GL-1 Generator (PCI Ozone and Control System Inc., West Coldwell, NJ).Water OutFigure 2.5: Britannia Water Purification Facility Pilot-Scale Ozone Contactor15

Prior to sample collection, the system was allowed to stabilize for a minimum of four HRTs.Samples for bromate and bromide were collected from ports located at the outlet of each column.These samples were quenched with using a 10:1 stoichiometric addition of ethylenediaminesolution. Ozone residuals were measured by the indigo method, as described in Section 2.4.10.Samples for determining the dissolved ozone concentration were taken from approximately thebottom, middle, and top of each column, using a 10-mL bottle-top dispenser attached to Teflontubing submerged in the columns.2.3 CALCULATION OF OZONE CONTACTThe terms ozone exposure (OE) and CTwere both used to represent levels of ozonation, and thedifferences between the two must be clarified. The term OE was used to describe the results ofthe true-batch experiments and represented a complete time-based integration of the ozone decaycurve. OE was also used to describe the laboratory-scale continuous-flow ozone contactor. Dueto the high rate of recirculation, the ozone residual measured at multiple points along the heightof the contactor were almost identical. As a result, OE was calculated by multiplying the steadystatereactor effluent ozone residual by the theoretical HRT.The term CT was used to describe the results derived from contactors where there was not acomplete spatial profile of ozone through the contactor, but rather only discrete measurements ofozone residuals corresponding to sampling locations. CT values for pilot- and full-scalecontactors were calculated according to four different methods: (i) conventional CT (CTswiR-tio)using tio contact time times and effluent ozone residual for each cell of the ozone contactorexcluding the first cell; (ii) all-cells CT (CTALL-tio) using an "all cells" approach where CT creditfor the first cell (effluent ozone residual multiplied by the first cell tio) was added to the CTswiRtio;(iii) CTswTR-t50 using tso (HRT) instead of tio for the corresponding contact time for each cellexcluding the first, multiplied by the corresponding cell's effluent ozone residual; and (iv)CTALL-ISO, calculated by summing the tso multiplied by the effluent ozone residual for each cell inthe contactor. The Surface Water Treatment Rule (SWTR) guidelines do not allow for CT creditfrom the first cell (USEPA, 1989; USEPA, 1990), however, CTSWTR-tio is a conservativeindicator of ozonation because there is some disinfection occurring within the first cell of anozone contactor and hence the additional use of CTALL-UO- Meanwhile, the use of tio versus tso isalso a conservative approach and hence the comparative use of CTswra-tso and CTALL-tso-2.4 ANALYTICAL METHODSAnalytical methods and procedures follow the accepted standards as set forth in StandardMethods and Procedures for Analysis of Water and Wastewater (APHA, AWWA, and WEF,1998). All samples to be analyzed for various water quality parameters were stored in amberglass containers at 4°C. All standards and solutions were prepared using reagent-gradechemicals and Milli-Q water. Milli-Q water was the product of tap water passed through deionizingcartridges (Millipore, Bedford, MA) followed by a carbon adsorber and a 0.2-ummembrane filter. This treated water consistently tested at 0.2 mg/L for dissolved organic carbon.16

Adjustments to pH for analytical purposes were made using phosphoric acid or 2.5% sodiumhydroxide.2.4.1 Bromide and BromateBromide and bromate samples were prepared for analysis by filtering the samples with 0.2-umsyringe filters. Dionex silver (OnGuard-Ag) and hydrogen-exchange (OnGuard-H) filters wereused to reduce chloride interference with bromate detection; however, the filters also removebromide. Thus, separate aliquots of the samples were analyzed to determine bromide andbromate concentrations. The detection limits for bromate and bromide were 2.0 ng/L and 10Hg/L, respectively. If the peak for bromate was not detected or unresolved from other peaks, apost-column derivatization method was performed (Echigo et al., 2000) to lower the detectionlimit to 0.3The ion chromatographic conditions for the conductivity method were as follows: analyticalcolumn, lonPac® AS9-HC (4 x 250 mm, Dionex, Sunnyvale, CA); guard column, lonPac® AG9-HC (4 x 50 mm, Dionex); eluent, 9 mM Na2COs; eluent flow rate, 1.0 mL/min; sample loop size,500 ]iL; detector, PED-2 (Dionex); suppressor, ASRS-Ultra (Dionex); suppression mode,external water mode. Samples of high chloride or carbonate concentrations, were pretreated withOn Guard-H and On Guard-Ag pretreatment cartridges and sparged with nitrogen gas for 5 min(at 3 psi).For the post-column derivatization analysis, the same ion chromatographic conditions as theconductivity method were used except for the detection method. The following conditions wereused for the derivatization and detection: post-column derivatization reagent, 1.0 M NaBrsolution containing 10 mg/L of NOa"; reagent flow rate, 1.0 mL/min; acidification, 1.5 M HaSO^reagent delivery, a gradient pump (GMP-2, Dionex) with 50/50 delivery; reaction coil size, 375uL; reaction temperature 68°C; UV detector path length, 6 mm; detection wavelength, 267 nm.2.4.2 Organic BromineBased on Standard Method 5320 (APHA, AWWA, and WEF, 1998), the analysis of total organicbromine (TOBr) was measured using a Dohrman Model DX-20A TOX analyzer with a granularactivated carbon (GAC) adsorption module. All the glassware was washed in an acid bath (1:1nitric acid) to minimize background interference, and then dried in an oven at 100°C. Tominimize background contamination, the GAC, packing material, and packing tools were storedin a desiccator under vacuum, and columns were packed in a room of relatively low organicbackground level.Sodium thiosulfate was used as the quenching agent for excess bromine. Eliminating theheadspace in the sample vials minimized the loss of volatile DBFs. The sample was thenacidified to a pH less than 2 to convert many of the acidic constituents of TOBr to theirprotinated (non-ionic) form. After acidification, 140 mL of sample was passed through twoGAC columns in series. The carbon column was then washed with 5 mL of 5,000 mg/L sodiumnitrate solution to remove inorganic halides trapped in the columns. The GAC was subsequently17

combusted at 800PC for 12 minutes. The HBr from the pyrolysis of brominated organiccompounds was trapped in a 70% aqueous acetic acid solution, and quantified bymicrocoulometric titration, yielding a minimum TOBr reporting level of 10 ug/L.2.4.3 Total and Dissolved Organic CarbonDissolved organic carbon (DOC) is operationally defined as the portion of the total organiccarbon (TOC) that passes through a 0.45 |im filter. Both TOC and DOC were analyzed as perStandard Method 5310C (APHA, AWWA, and WEF, 1998), using a Sievers (Boulder, CO) 800portable total organic carbon analyzer. The Sievers analyzer uses the ultraviolet-persulfateoxidation method, yielding measurements of total organic carbon, inorganic carbon and totalcarbon (sum of preceding measurements). TOC and DOC were reported in mg of carbon perliter (mg-C/L), each with a minimum reporting levels of 0.1 mg-C/L.2.4.4 Ultraviolet AbsorbanceUltraviolet absorbance (UVA) at 254 nm was used as a surrogate measurement of NOMaromatic character, as it responds to aromatic and carbon-carbon double bonds. A Shimadzu(Columbia, MD) UV160U UV-visible recording spectrophotometer was used to analyze UVA254using a 1-cm path length, as described in Standard Method 5910 (APHA, AWWA, and WEF,1998). As part of the characterization of NOM, UVA254 (measured in cm" 1) was measured for0.45 um filtered water samples. In addition, the ultraviolet spectrum from 200 to 400 nm(UV2oo-40o)was recorded to provide an untreated water "signature" to compare with ozonatedwater spectra.Specific UVA (SUVA) is a correlative parameter of the UVA normalized by the DOCconcentration of the sample, and is reported as L/(mg-m). Both UVA and SUVA were used toobserve changes in NOM character due to ozonation.In addition, differential UVA254 (AUVA254) and differential UVA spectra (AUVA2oo-40o)wereused to characterize the change in NOM as a result of ozonation. These different values weredetermined by mathematically subtracting one value (UVA254) or a spectrum (UVA2oo-40o) fromanother, resulting in a positive values when the after-ozone UVA254 value or spectrum (UVA2oo-400) was subtracted from the before-ozone values. A change in UVA spectra implies reactivity ofthe NOM with ozone.2.4.5 NOM FractionationNOM was fractionated using macroporous, nonionic resins (Amberlite XAD-4 and XAD-8)according to the method described by Aiken et al. (1988). Filtered (0.45 urn), acidified (pH = 2)samples are passed sequentially through XAD-8 and XAD-4 resin columns, at flow rates of 1.3to 2.0 mL/min and 1.0 to 1.5 mL/min, respectively. These conditions provided an adsorptioncoefficient, k, of 50. Samples from the effluent of each column were collected after the samplewas processed. Pre-XAD, XAD-8 effluent and XAD-4 effluent samples were analyzed forNOM, operationally defined by the DOC results of the sample analyses.18

2.4.12 Quality Assurance and Quality ControlQuality assurance (QA) and quality control (QC) for the project consisted of a series ofcomparative analyses for bromate and bromide through a round robin procedure among all of theproject research laboratories and the internal evaluations of replication error for analyses andexperimental reproducibility.2.4.12.1 Interlaboratory ComparisonsFormal comparisons of bromate and bromide analysis were administered through a series ofround robin tests, which served as a quality assurance and quality control check between the fouruniversities. After preliminary method comparisons, three comprehensive round robin tests wereconducted during the data collection period of this project.For the first two round robin tests, samples were prepared by the University of Illinois (UI) andsent blindly to the University of Colorado (UC), University of Toronto (UT) and University ofPoitiers (UP), for bromate and bromide analysis. Natural and Milli-Q water samples were spikedwith different levels of bromide, bromate and selected interfering ions. Samples werecategorized in terms of initial water matrix, presence of interfering ions (chloride - Cl", andsulfate - SC

Sample1234567891012345678910Milli-QMilli-Q + SaltsfMilli-QMilli-Q + Salts1Milli-QMilli-Q + Salts1Lake Houston Blank*Lake Houston *Lake Houston*Lake Houston*Milli-QMilli-Q + SaltsfMilli-QMilli-Q + Salts1Milli-QMilli-Q + SaltsfLake Houston Blank*Lake Houston *Lake Houston*Lake Houston*Table 2.6: Second Round-Robin ResultsSpikeBromate1.31.36.46.43838-+1.3+6.4+38Bromide5515155050-+5+15+501(ug/L)1.21.15.45.6333328252957(Hg/L)5.410549.737356.3191565* Preozonated2'f 50 mg/L Cr + 1 00 mg/L SO42* Insufficient sample volume for analysisUniversity2 3

particular interferences. If interferences were detected, standard additions were used to minimizethe error of analysis.For the samples with low bromate concentrations, less than the minimum reporting level resultsfrom several of the labs were considered generally accurate for electrical conductivity detection.For these same samples, the post-column reaction system worked reasonably well.For the third comprehensive round robin test, blind samples were prepared by MontgomeryWatson and sent to UI, UC, UT and UP for bromate and bromide analysis. In addition to theseblind samples, two sets of standard bromate solutions were included by Montgomery Watson.The first series of standard bromate solutions were prepared from known masses of sodiumbromate salt. The second set of standard solutions were prepared from a concentrated bromatesolution used in the European Community (EC) interlaboratory bromate comparability study.The universities were asked to calculate the bromate concentrations of the blind samples using:1) their own standard solutions, 2) the Montgomery Watson standard solutions, and 3) the ECstandard solutions. No additional bromide standard solutions were provided by MontgomeryWatson. The blind samples were Milli-Q water spiked with different levels of bromide, bromateand/or interfering ions (chloride and sulfate).Interlaboratory agreement was generally good for bromate analyses, with and without interferingions, even at these low concentrations of bromate (Table 2.7 and Table 2.8). There were somepreviously acknowledged temporary difficulties with the bromide analysis at the University ofIllinois during the period that the round robin results were being sent out. It is believed that thisproblem was quickly rectified. During this time of difficulty, the samples for bromide analysiswere sent from University of Illinois to University of Colorado. The other three universitiesshowed good interlaboratory agreement for these bromide analyses.Sample Spike(US/L)A 1.4BC 8.3D 5.3E 2.9Table 2.7: Third Round-Robin Bromate Results11 MWT EC1.9 2.0 2.0nd nd nd9.4 10.1 9.76.4 6.9 6.63.3 3.6 3.4Univi;rsity22 MWT EC1.0 1.1 1.1nd nd nd7.9 8.3 8.95.4 5.6 6.02.5 2.6 2.8A - Deionized water + 54 mg/L NaCl + 51 mg/L NaSO4B - Deionized water + 54 mg/L NaCl + 51 mg/L NaSO4C - Deionized water + 54 mg/L NaCl + 51 mg/L NaSO4D - Deionized water + 54 mg/L NaCl + 51 mg/L NaSO4E - Deionized waterMontgomery Watson33 MWT EC1.1 1.4 1.3nd nd nd6.8 7.4 7.54.2 4.8 4.22.9 3.2 2.744 MWT EC

2.4.12.2 Individual Research LaboratoriesQuality control was undertaken during the project to assess analytical and experimental error.Coefficients of variation (CV) were calculated using the means and standard deviations ofanalytical and experimental results. Table 2.9 represents the calculated CVs. Analytical errorwas assessed by measuring 10 percent of the analyses in triplicate.Sample ID*ABCDETable 2.8: Third Round-Robin Bromide ResultsSpikeGig/L)102129-11926409.6ndUniversity2 31123292.11818A - Deionized water + 54 mg/L NaCl + 51 mg/L NaSO4B - Deionized water + 54 mg/L NaCl + 51 mg/L NaSO4C - Deionized water + 54 mg/L NaCl + 51 mg/L NaSO4D - Deionized water + 54 mg/L NaCl + 51 mg/L NaSO4E - Deionized water1224322.0214122127

experiments, a relatively high degree of reproducibility was observed for both bromate and totalorganic bromine given the inherent difficulties in attaining the exact same OE value and otherexperimental conditions.Table 2.10: Experimental Quality Control for Laboratory-Scale Continuous-Flow OzoneContactorReplicate12345*6*789101112OE(mg-min/L)112.3102.519.419.657.364.156.866.062.861.863.862.819.620.018.119.160.456.760.364.964.568.720.820.4Bromate(Hg/L)21.322.35.75.413.39.14.82.41.21.70.71.138.440.224.123.642.448.313.315.83.03.2116.292.4Total OrganicBromine(Hg/L)789116ND169351334401348109NDND7898NDNDNDND* Note: Replicates 5 and 6 were performed on DAL whichhas a high ambient TOX due to chlorinated compounds.2.5 MODEL DEVELOPMENT2.5.1 Cryptosporidium parvum Inactivation KineticsThe Chick-Watson law has been widely used for the mathematical representation of thedisinfection kinetics of various microorganisms. However, the inactivation kinetics of C.parvum oocysts have been shown by some researchers to deviate from the Chick-Watson law.Rennecker et al. (1999) presented C. parvum inactivation curves characterized by an initial lag25

phase during which little or no inactivation occurred followed by a pseudo first-order rate lawinactivation. Several empirical expressions have been suggested for inactivation kinetics thathave an initial time lag (Collins and Selleck, 1972; Haas 1980; Severin et al., 1984; Rennecker etal., 1999). The delayed Chick-Watson model (Equation 2.1) proposed by Rennecker et al.(1999) was used in this study for modeling purposes.JLNnNnifCT>CTIag = --(2.1)Where: N/No - survival ratio; N\INo - lag phase factor; fa = pseudo first-orderinactivation rate constant [I/M^T" 1 ]; CT/ag = CT required to overcome theinitial time lag [MTL~3]. The parameters that determine inactivation kinetics,such as Ni/No and fa, can be obtained from fitting experimental data obtainedfrom a semi-batch reactor.2.5.2 Ozone Decomposition and Bromate Formation MechanismsOzone in aqueous phase decomposes through a chain of reactions including initiation byhydroxide ion attack followed by propagation steps involving superoxide radical, ozonideradical, and hydroxyl radical as intermediate species. The ozone decomposition mechanismdeveloped by Staehelin and Hoigne (1982), Biihler et al. (1984), and Staehelin et al. (1984) wasadopted (Reactions 1-11, Table 2.11) with minor modification. In this study, the species HCV,whose existence was suggested by Staehelin et al. (1984) as an intermediate for the reaction ofOs and -OH ultimately producing HCV and 62, was neglected due to the lack of evidenceshowing that this hypothetical species exists.Table 2.11: Ozone Decomposition and Bromate Formation MechanismNo. Reaction Rate Constant* ReferencesOzone Decomposition1 O3 + OH' -> O2'- + HO2 -k, = 70Staehelin and Hoigne (1982)2 HO2 - O2-> H+pKa = 4.8Staehelin and Hoigne (1982)3 O3 + O2-- -> O3"- + O2ka = 1.6x 109 Buhlere/a/.(1984)4 HO3 - H202 + O2k9 = 5 x 109 Staehelin et al. (1984)10 O2'- + HO3 - -» OH' + 2O2k, 0 =l x 10 10 Staehelin et al. (1984)11 HO3 - + HO3 - -» H2O2 + 2O2 k,, = 5x io9 Staehelin et al (1984)(continued)26

Table 2.11: Ozone Decomposition and Bromate Formation Mechanism (cont'd)No. Reaction Rate Constant* ReferencesMolecular Ozone Pathway20 Br" + O3 -» O2 + OBr"k20 =16021 OBr" + O3 -» 2O2 + Brk21 = 33022 OBr" + O3 -> BrO2" + O2k22 =10023 BrO 2" + O 3 -» BrO 3" + O2k23 =lx!0 5Hydroxyl Radical Pathway24a Br + -OH-> BrOH"-24b BrOH"- -» Br" + -OH25a BrOH"- -» Br- + OH"25b Br- + OH" -> BrOH'-26 BrOH"-+ H+ -> Br- + H2O27 BrOH"- + Br" -» Br2"- + OH"28a Br- + Br' -» Br2"-28b Br2'- -> Br- + Br"29 Br2"- + Br2"- -> Br3" + Br"30a Br3" -> Br2 + Br"30b Br2 + fir" -> Br3"31a Br2 + H2O-» HOBr + H+ + Br"3 Ib HOBr + H+ + Br" -» Br2 + H2O32 HOBr BrO" + H+33 O3 + Br- -> O2 + BrO-34 Br- + OBf -> BrO- + Br"35 -OH + OBr" -» BrO- + OH"36 -OH + HOBr -> BrO- + H2O37 O2"- + HOBr -» O2 + Br- + OH"38 2BrO- +H2O->. OBr" +BrO2" + 2iT39 BrO- + BrO2" -» OEf + BrO2 -40 Br2"- + BrO2 " -> OBr" + BrO- + Br"41 -OH + BrO2- -> BrO2 - + OH'42 -OH + BrO2 - -» BrO3 " + H*43a BrO2 - + BrO2 - -> Br2O443b Br2O4 -> BrO2 - + BrO2 -44 Br2O4 +OH" -^ BrO3" + BrO2" + H+Carbonate50 H2CO3* H+ + HC03"51 HCXV

Table 2.11: Ozone Decomposition and Bromate Formation Mechanism (cont'd)No. ReactionPhosphate Buffer60 H3PO4

omate reduction potential of adding ammonia or J-butanol was incorporated into the modelwith the Reactions 80-82 and Reaction 90, respectively. Finally, the influence of natural organicmatter on ozone decomposition and bromate formation was empirically formulated throughReactions 100-102, which are modified from those proposed in previous studies (Staehelin andHoigne, 1985; Bezbarua and Reckhow, 1996; Westerhoff et al, 1997). The rate constants for allthe reactions in Table 2.11 were used as reported in the literature. However, the empiricalparameters that reflect the characteristics and the quantity of NOM in natural waters, such as a,P, and y, were determined from fitting the experimental ozone decomposition and bromateformation data collected from the true-batch reactor experiments.2.5.3 Ozone Contactor Modeling2.5.3.1 Batch Ozone ContactorA total of N chemical species undergoing chemical reactions in an ideal batch reactor can berepresented mathematically with a system of N coupled first-order nonlinear ordinary differentialequations with the general form:=/,.(C 1 ,C 2 ,--.,C JV ) i = l,2,---,N (2.2)Where: C, [ML"3] = concentration of chemical species; [M] = mass; [L] = length; t [T] =time;fj = overall rate function corresponding to the relevant chemical reactions.Though commercially available software, such as Acuchem, have been widely used for solvingrate expressions for the sets of chemical reactions, their application is confined only to the batchreactor configuration. Therefore, software that could also be used to represent chemicalreactions in flow-through reactor systems was developed as a part of this study. The abovesystem of ordinary differential equations was solved by a semi-implicit extrapolation method toaddress the stiffness problem that was experienced when applying explicit methods, such asRunge-Kutta. The solver algorithm was designed to provide an adaptive step size control overthe period of integration in order to achieve desired accuracy with minimal computational effort.Major integration routines were taken from Press et al. (1992), modified, and encoded for C++programming language. The program code is included in the appendix.2.5.3.2 Continues -Flow ContactorThe computer code for the batch reactor was modified to obtain the steady-state solution for anozone bubble-diffuser reactor with internal recirculation. In this case, both the reactor (mainbubble column) and the recirculation line were modeled as ideal plug-flow reactors (PFRs).Specifically, calculation along the bubble column and recirculation line was iterated untilsufficient convergence criteria were met at the inlet of the reactor. Additional mass balances forgaseous phase ozone and the interface mass transfer of gaseous phase ozone to liquid phase werealso incorporated into the model. The overall volumetric mass transfer coefficient for thespecific operating conditions were estimated from the empirical correlations described byMarinas et al. (1993). Average bubble size in the bubble-diffuser column, one deciding29

parameter in mass transfer evaluation, was measured photographically. The program code isincluded in the appendix.2.5.3.3 Pilot- and Full-Scale Ozone ContactorsEach chamber of a multi-chamber bubble diffuser contactor can be modeled as an axialdispersion reactor (ADR), where a single parameter (i.e. dispersion number) determines anoverall characteristic of the non-ideal reactor hydrodynamics. In general, the steady-state massbalance for each chemical species can be represented by the following second-order non-linearordinary differential equation as follows:dz dzC2 ,--,CN ) i = l,2,--,N (2.3)Where: d [dimensionless] = dispersion number; z [dimensionless] = normalizeddownward distance from the water surface; 9 [T] = hydraulic residence time inthe chamber. In the case of a bubble-diffuser column, interface mass transferterms are included in the reaction ft for the gas and liquid phases as described inMarinas et al. (1993). The sign of the second term was determined by theoperation mode (i.e. counter-current or co-current). In this model, it wasassumed that d = 0 in gas phase (and thus the equation is first-order) and the gasvolume fraction throughout the bubble-diffuser column was negligible. Theabove set of second order non-linear ordinary differential equation was subject to2N-1 boundary conditions of the form:i = l,2,-, AT (2.4)dC:outlet= 0 i =1,2,-, AT (2.5)Each second order ordinary differential equation except that for gas phase wasreplaced by a set of two first-order ordinary differential equations by introducingthe auxiliary variable d*.dz d(2.7)The resulting set of 2N-1, first-order differential equations were substituted with finite-differenceequations on a mesh of points that covered the range of integration. An iterative calculation wasperformed until the deviations from the finite-difference approximation of each equation at eachmesh point were sufficiently small. The calculation algorithm, called the relaxation method, wasadopted mostly from Press et al. (1992) and modified and programmed with C++ programminglanguage. The code is included in the appendix.30

CHAPTERS. BROMATE SURVEYA North American and European survey of ozonation utilities was conducted to understandbromate occurrence (formation) at full-scale water treatment plants under current levels of ozoneapplication. While bromate occurrence information was the primary intent of the survey,additional information was extracted from a large water quality and treatment conditiondatabase. Specifically, relationships between key water quality parameters and bromateformation were investigated.3.1 PARTICIPATIONA list of candidate participants was established by using two existing water treatment plantdatabases that identify ozonation facilities: the American Water Works Association (AWWA)WaterStats database and the International Ozone Association (IOA) database. A master list ofover sixty potential survey candidates was generated. A survey participation letter andquestionnaire was sent to each candidate, explaining the survey's intent and outlining the detailsof participation. Two rounds of solicitation by mail resulted in the participation of twenty-fourutilities, yielding a response rate of 40 percent. At the request of the majority of the utilities,participation was kept anonymous.The goal of the survey solicitation was to assemble a representative cross-section of ozonationutilities as participants. A geographic distribution of survey participants is presented in Figure3.1. There was a reasonable distribution among the participating utilities. Of the twenty-fourutilities that responded, twenty-one were located in the United States and three were located inFrance. While participation from California appears to be geographically biased, the largernumber of participants is somewhat justified due to the number of utilities that utilize ozonewithin the state.Survey participation was also summarized in terms of type of ozonation (i.e. point of ozoneapplication) and source water type. A qualitative summary of utility participation can be foundin Table 3.1. Pre-ozonation (ozonation before coagulation) was the dominant type of ozonationrepresented, and the majority of participants were ozonating surface waters.In order to provide some background in terms of the physical configuration of each utility'sozone process, the main details of the individual ozone contactors were summarized. Thisinformation is displayed in Table 3.2 in terms of location of ozone application, contactor type,and number of cells. All of the participating utilities utilized various configurations of finebubble diffusers to transfer the ozone into the bulk water; no use of other contactor types (i.e.turbine, packed column, direct injection or deep U-tube) was reported. Some contactors had upto six cells or individual chambers, while others consisted of a single column or a single largebasin, where ozone gas was applied. While many utilities have the capability for multi-stageozonation (i.e. multiple locations of ozone addition within one contactor), almost all of thecontactors are operated in a single-stage fashion.31

= utility location24 utilities total (21 U.S. and 3 French)Figure 3.1: Participation Map for Survey Participants3.2 ORGANIZATIONAfter responses to the survey questionnaire were received, the sampling effort was launched.The survey was organized into three rounds. The three separate sampling campaigns (June 1998,November 1998, and June 1999) were administered to obtain sample pairs of before and afterozone application and evaluate seasonal variability. The before-ozonation samples werecollected from the influent of the ozone contactor immediately prior to ozonation, and the afterozonationsamples were collected from the effluent of the ozone contactor. Thus, the true effects32

of the ozone contactor could be investigated, without the cumulative effect of multiple treatmentprocesses.Table 3.1: Qualitative Summary of Survey ParticipantsType of ozonation:Pre-ozonationIntermediate-ozonationDual-ozonation (2 points of application)Post-ozonationGeographic distribution:North-WestSouth-WestNorth-CentralSouth-CentralNorth-EastSouth-EastFranceSource water type:Surface water, river or aqueductSurface water, lake or reservoirGroundwater* 24 participants total in 3 sampling campaignsNumber of participants*11571The first and third rounds of samples were collected and analyzed in the late spring/earlysummer, which is generally representative of primarily late runoff conditions for surface watersupplies. The second round of sampling and analysis took place in late fall/early winter, whensurface-water hydrologic systems generally experience baseflow conditions. Because the thirdround of the survey was administered during the same time of year as the first round, these twodata sets were used to evaluate potential year-to-year temporal variation in source water quality.The second round of sampling could be compared to round one and/or three to examine seasonalvariability.While there were twenty-four survey participants, the number of samples received during eachround was less than this value. Round one included twenty-two utilities, round two had twentyoneparticipants, and round three received a response from twenty-two utilities. Two sample setswere requested from the dual-ozonation facilities. Both influent and effluent ozone sampleswere obtained for each of the two points of ozone application in an attempt to further understandthe stepwise bromate formation in this facility. This fluctuating number was due tocircumstantial inclusion or withdrawal of utilities from one round to another. Nineteen of theutilities participated in all three rounds of the survey.5442423138333

Table 3.2: Survey Utility Participant Ozonation InformationID A B C D E F G H I J K L M N 0 Type of OzonationPre Pre/Int Pre Pre Pre Pre/Int Pre Post Pre Pre Pre/Int Pre Pre/Int Int Int Contactor Type Diffuse bubble Diffuse bubble Diffuse bubble Diffuse bubble Diffuse bubble Diffuse bubble Diffuse bubble Diffuse bubble Diffuse bubble Diffuse bubble Diffuse bubble Diffuse bubble Diffuse bubble Diffuse bubble Diffuse bubble Flow ConfigurationOver/under Over/under Over/under Over/under Over/under Over/under Over/under Over/under Over/under Counter-current Cross-flow Over/under Over/under Over/under Over/under Cells' 2 4/4 5 4 6 2/6 4 5 3 1 1/1 5 4/4 3 5 Comments2 contactors in parallelCan apply Os in first 3 cells2 contactors in parallel4 contactors in parallelSingle-stage ozonation2 contactors in parallelCan apply Os in any of 4 cellsOzone is primary disinfectantMulti-stage applicationSingle columnSingle large undivided contact basin4 contactors in parallelSingle-stage ozonationSingle-stage ozonationCan apply Os in first 3 cellsP Int Diffuse bubble Over/under 4 Can apply Os in first 2 cellsQ Pre Diffuse bubble Over/under 2 Can apply Os in first 2 cellsR Pre Diffuse bubble Over/under 6 Ozone applied in first cellS T U Pre/Int Pre/Post Pre Diffuse bubble Diffuse bubble Diffuse bubble Over/under Over/under Over/under 4/4 4/4 6 Multi-stage application2nd Os application after filtersOzone is primary disinfectantV Int Diffuse bubble Over/under 4 Can apply Os in first 2 cellsw Pre/Int Diffuse bubble Over/under 1/4 Can apply Os in first 2 cells of int cont.X Int Diffuse bubble Over/under 3 Can apply Os in first 2 cellsnumber of cells in contactor; two numbers reflect pre- and int-(or post-)ozonation3.3 DETAILS OF ANALYSESThe information derived from the survey was organized into two groups: water qualityparameters and treatment conditions. Measured water quality parameters consisted of pH,temperature, DOC, UVA254, alkalinity, ammonia-nitrogen, bromide, and bromate. Calculatedwater quality parameters included SUVA, AUVA254, and percent bromide conversion to bromate.The percent bromide conversion to bromate was calculated as follows:% Bromide Conversion to Bromate = (BrO3 ~ as Br~) / Br"before * 100% (3.1)After receiving the samples, analyses of DOC, alkalinity and ammonia were performed on theinfluent sample only; UVA254 and bromide were conducted on the both the influent and effluentsamples; and bromate was only analyzed for in the effluent sample. Since the effluent sampleswere not quenched at the time of sampling, it is important to note that the data reflect thebromate formation after complete dissipation of ozone residual. These bromate values would be34

generally be representative unless the utility practiced ozone residual quenching (utilities werenot queried about quenching). Values for pH and temperature were measured by the respectiveutilities at the time of sampling.Treatment conditions monitored and provided by the utility included ozone dose (either astransferred dose or applied dose with estimated percent transfer efficiency) and hydraulicresidence time (HRT). When available, dissolved ozone concentrations at the exit of each cell ofthe ozone contactor and tio contact time estimates from each cell were provided. Also, estimatesof CT were requested. If CT was not provided, but adequate ozone residual and tio data wereavailable, CTswia was calculated by SWTR guidelines (Oa residual x tio for each cell, excludingthe first cell). Although some informative data were obtained, the feedback from utility to utilityvaried in terms of type of information and degree of detail. For example, some utilities simplyprovided an overall HRT of the contactor along with transferred ozone dose, while othersprovided a complete breakdown of tio contact times and dissolved ozone residuals for each cellwithin the ozone contactor.3.4 RESULTSResults from the survey are presented for each round of sampling. Also, an overall summarywas created based on all three sampling campaigns. A collection of descriptive statistical tools,as well as simple-linear regression, was used to analyze each data set. The number of samplesreported for each round was greater than the number of participants because of the dualozonationutilities. For the dual-ozonation utilities, the influent to each ozone contactor wascharacterized in terms of water quality and treatment conditions. For statistical purposes, anynon-detect measurement was assigned a value of one-half times the minimum detection limit.3.4.1 Individual Survey Rounds3.4.1.1 Descriptive Statistical AnalysisInitially, a variety of descriptive statistics was used to summarize the data from each of thesampling rounds. The number of samples, the sample mean, standard deviation, and range invalues (minimum to maximum), as well as the 10th, 50th (median), and 90th percentile values ofall the survey parameters were summarized. The results of the descriptive statistics are presentedin Table 3.3, Table 3.4, and Table 3.5, for sample rounds one, two and three, respectively. Theparameter of CT was not requested during round one of sampling and, therefore, was not a partof the statistical analysis for that round.The average bromate was highest during round three (4.7 ug/L), followed by round one (4.1ug/L) and lowest during round two (2.7 ug/L). Average percent bromide conversion to bromatefor rounds one, two and three were 7.3, 5.3, and 6.7 percent, respectively.35

Table 3.3: Water Quality and Treatment Condition Summary of Sampling Round OneParameterTemperature (°C)Br (ug/L)BrO3 " (ug/L)10th % 50th % 90th %Br effluent (ug/L)Br' conversion to BrO3"(%) PHAlkalinity (mg/L as CaCO3) NH3-N (mg/L)O3 dose (mg/L)Mean 21 66 4.1 62 7.3 7.7 111 0.17 1.9 Std. Dev.4.9525.653140.7690.191.0HRT (min)18 18CTswiR (mg/L-min)*- -DOC (mg /L)UVA254(cm- 1 )SUVA (L/mg-min)UVAeffluent (cm" 1)AUVA254 (cm' 1 )3.1 0.069 2.1 0.032 0.037 1.50.0500.70.0160.041* data not collected during the first roundRange8.8 - 272.5 - 1800.2- 182.5-1800.2 - 726.5 - 10.68.7 - 2700.01 - 0.700.5 - 5.02.0 - 82-1.3-8.60.012 - 0.2600.9 - 3.40.011-0.079-0.010-0.18114140.27.90.27.1290.020.83.0-1.50.0231.20.0170.00121541.6472.27.71100.082.015-2.70.0542.00.0280.0272717014170168.32000.522.730-4.50.1203.00.0520.098Table 3.4: Water Quality and Treatment Condition Summary of Sampling Round TwoParameterTemperature (°C)Br- (ug/L)Br03- (ug/L)10th % 50th % 90th %Br effluent (ug/L)Br" conversion to BrO3"(%)pHAlkalinity (mg/L as CaCO3)NH3-N (mg/L)O3 dose (mg/L)HRT (min)CTswiR (mg/L-min)*DOC (mg/L)UVA254(cm- 1 )SUVA (L/mg-min)UVAeffluent (cm' 1 )AUVA254 (cm' 1)Mean17492.7465.37.7950.141.5231.23.00.0682.10.0350.033Std. Dev.4.4407.039120.8610.230.9141.61.90.0580.630.0340.027Range7.0 - 243.7-1500.1-366.4-1500.08 - 536.3 - 9.96.8-2800.01 - 1.10.3-3.14.2 - 540.0 - 4.71.0-8.90.017 - 0.2470.9 - 3.26.011-0.1540.002-0.1169.0110.28.00.36.6390.010.3100.01.50.0241.40.0130.01018360.6331.67.6840.071.3180.32.50.0542.30.0240.022221204.1120198.31600.332.7463.54.90.0902.90.0670.065Slightly higher average transferred ozone doses were observed during rounds one and three (1.9mg/L and 2.0 mg/L, respectively), when compared to round two (1.5 mg/L). The vast majorityof participants reported transferred ozone dose as opposed to applied dose with percent transferefficiency. HRT is a characterization of the contactor volume for a given flow, and served as abasis from which ti 0 contact data were derived. The limited amount of tio data provided for36

individual cells of contactors was determined from tracer tests and was dependent on the specifichydrodynamics of the individual contactors. The average HRT for each round ranged from 18 to23 minutes. The reported CTswiR averaged 1.23 mg-min/L and 0.68 mg-min/L for rounds twoand three, respectively. These averages were calculated from all of the available data, though notall of the utilities responded to all the questions.Table 3.5: Water Quality and Treatment Condition Summary of Sampling Round ThreeParameterTemperature (°C)Bf (ug/L)Br03" (ug/L)10th % 50th % 90th %Br'effluent (Hg/L)Br" conversion to BrO3~(%)PHAlkalinity (mg/L as CaCO3)NH3-N (mg/L)O3 dose (mg/L)HRT (min)CTswxR (mg/L-min)*DOC (mg /L)UVA254(cm~ 1)SUVA(L/mg-min)UVAgffluent (cm" 1)AUVA254 (cm' 1 )Mean21454.7456.77.5930.222.0210.73.00.0712.30.0410.031Std. Dev.4.7381037110.7610.321.59.90.91.80.0540.60.0280.028Range9.0-27 .2.0 - 1300.2 - 403.2-1100.12-486.2 - 9.46.5 - 2800.01 - 1.20.1-7.96.8 - 490.0-3.10.8 - 8.40.013 -0.2441.1 -3.20.011 -0.1160.002-0.128135.90.28.10.26.5290.030.5120.01.30.0181.50.0130.00522291.1262.57.7780.071.9190.22.60.0652.30.0360.0252610022110278.31700.913.0352.25.00.1183.10.0860.052The organic characterization of the survey samples was limited to measurements of DOC,UVA254, SUVA, and AUVA254. Based on these four indicators, the average organic character ofthe ozone contactor influent samples did not appear to vary significantly between the samplingrounds. Mean values were very similar for DOC (from 3.01 to 3.10 mg/L), UVA (from 0.068 to0.071 cm" 1), and SUVA (from 2.08 to 2.25 L/mg-m). Even the average AUVA254, whichembodies the oxidative effects of ozonation, did not appear to change significantly (from 0.031to 0.037 cm" 1).3.4.1.2 Single-Linear Regression AnalysisSpecific relationships between water quality parameters and treatment conditions were exploredusing simple-linear regression. The direct relationship of each parameter compared to everyother parameter was evaluated through the development of a Pearson correlation matrix. Theresultant symmetric correlation matrix lists correlation coefficients (r values) for each parameteras a result of individual linear regression on a variable per variable basis. The Pearsoncorrelation matrices for rounds one, two, and three are shown in Table 3.6, Table 3.7, and Table3.8, respectively. The importance of the correlation coefficients was not only in the magnitudeof the value but also the sign, which relays a direct (positive value) or inverse (negative value)relationship between parameters.37

Table 3.6: Pearson Correlation Matrix for Sampling Round OneooParameter 0.73 0.87 -0.350.70 0.96 -0.370.39 0.74 -0.32DOC UVA254 SUVA NH3-N Alk Br" Temp pH O3 dose HRT CTSWTR Br'efnuent Br-conver UVA254 efnuent AUVA254 BrO3"DOC 1.00 0.940.25 -0.09 0.69 -0.10 n/a 0.01 -0.21 UVA2S4 1.000.18 -0.22 0.71 -0.12 n/a -0.15 -0.23 SUVA-0.05 -0.32 0.46 -0.23 n/a -0.21 -0.20 NH3-NAlkalinityBrTemperaturePHO3 doseHRTCTs\VTRBr effluentD_-01 converUVA2 54_efflUentAUVA2S40.48 0.58 0.29 0.250.72 0.47 0.22 0.091.00 0.190.10 0.151.00 0.26 0.611.00 0.391.000.540.140.351.000.24-0.050.310.341.00BrO/Samples 26 26 26 26 26 26 26 26 25 25 26 26 26 26 26n/a = not applicable0.470.320.170.330.051.00-0.27-0.02-0.28-0.64-0.22-0.101.00n/an/an/an/an/an/an/an/a0.490.190.930.280.37-0.07-0.33n/a1.00-0.26-0.13-0.33-0.40-0.36-0.180.73n/a-0.321.000.370.240.240.00-0.100.46-0.05n/a0.06-0.281.000.430.180.020.21-0.240.70-0.13n/a-0.20-0.170.471.00-0.130.410.180.030.050.110.10n/a0.130.30-0.38-0.301.00

Table 3.7: Pearson Correlation Matrix for Sampling Round TwoOJParameter 0.92 0.87 -0.040.95 0.92 -0.130.43 0.61 -0.250.88 0.61 -0.050.24 0.25 0.090.52 0.40 0.200.51 0.44 -0.020.29 0.14 0.090.52 0.61 0.230.01 0.05 -0.07-0.41 -0.54 0.560.44 0.30 0.13-0.12 -0.15 0.501.00 0.75 -0.091.00 -0.17DOC UVA254 SUVA NH3-N Alk Br Temp pH 6^HRT CTSWTR Kr emaent Br-conver UVA254emuent AUVA254 BrO3doseDOC 1.00 0.96 0.31 0.82 0.28 0.57 0.52 0.27 0.61 -0.04 -0.43 0.48 -0.16 UVA254 1.00 0.55 0.81 0.26 0.50 0.51 0.24 0.60 0.03 -0.48 0.41 -0.14 SUVANH3-NAlkalinity1.00 0.20 1.00 0.06 0.14 0.02 0.53 1.00 0.05 1.00 0.16 0.49 0.11 0.38 0.07 0.39 0.04 0.44 0.41 0.49 0.02 0.70 0.03 0.02 -0.22 -0.13 -0.63 -0.26 -0.16 -0.39 0.13 0.53 -0.16 0.94 -0.01 -0.18 -0.24 -0.23 TemperaturepHO3 doseHRTCTswTR1.00 0.11 1.00 0.25 0.23 1.00 0.05 -0.33 0.04 1.00 -0.37 -0.29 -0.38 0.48 1.00 0.28 0.54 0.67 -0.18 -0.37 -0.44 -0.29 0.03 0.25 0.41 Br effluent1.00 -0.23 **'" conver1.00 UVA254.efnuentAUVA254_________________________________________________________________________________1.00Samples_____25 25 25 25 25 25 24 25 24 21 17 25 25_____25______25 25

Table 3.8: Pearson Correlation Matrix for Sampling Round ThreeParameter UVA2S4 efnuent AUVA254 BrO3'0.94 0.87 -0.150.95 0.95 -0.170.49 0.55 -0.080.73 0.46 -0.22DOC UVA254 SUVA NH3-N Alk Br' Temp pH O3 dose HRT Br'effluent DOC 1.00 0.96 0.31 0.65 0.34 0.36 0.27 0.45 0.25 0.15 -0.31 0.35 -0.25 UVA2S4 1.00 0.54 0.62 0.34 0.28 0.20 0.39 0.22 0.15 -0.28 0.26 -0.28 SUVA1.00 0.26 0.09 0.06 -0.08 0.19 0.12 0.04 -0.07 0.05 -0.19 NH3-N1.00 0.03 0.20 0.33 0.48 0.13 -0.03 -0.34 0.34 -0.29 Alkalinity1.00 0.43 0.15 0.23 -0.18 0.07 0.01 0.26 0.19 BrTemperaturepHO 3 doseHRTCTswTRBr effluent"1" converAUVA254Br031.00 0.24 1.00 0.29 0.20 1.00 0.12 -0.04 -0.11 1.00 0.07 -0.40 -0.48 0.63 1.00 0.35 -0.33 -0.16 -0.18 0.32 1.00 0.93 0.24 0.43 0.15 -0.02 0.30 1.00 -0.06 0.19 0.03 -0.05 0.02 0.30 -0.17 1.00 0.31 0.30 0.27 0.45 0.18 0.10 -0.35 0.30 -0.37 1.00 0.34 0.23 0.11 0.30 0.23 0.19 -0.19 0.19 -0.17 0.81 1.00 0.190.320.250.130.140.070.500.190.82-0.25-0.071.00Samples 27 27 27 27 27 27 27 27 26 20 23 27 27 27 27 27

A ranking scheme for the correlation coefficients was developed to qualitatively identify the topfive most influential parameters on bromate formation. An r value with a magnitude of 0.65 orgreater received a triple index ranking (+++ or —), an r value between 0.40 and 0.65 received adouble index rank (++ or --), and values less than 0.40 received a single index rank (+ or -). Thefive most influential parameters, along with their corresponding r values, are listed in Table 3.9,Table 3.10, and Table 3.11, for sampling rounds one, two and three, respectively. Since percentbromide conversion to bromate represents an alternative way to express bromate formation, itwas not included in the ranking. For round one, alkalinity showed the highest correlation tobromate (r = 0.41), while CTSWTR had the highest correlation with bromate for rounds two andthree with r values of 0.56 and 0.50, respectively. Even though these correlations were thelargest for each of the three rounds, none of these relationships were considered strong.Table 3.9: Top Five Highest Correlating Parameters to Bromate for Single-LinearRegression Analysis of Round OneParameter Rank Correlation Index r valueAlkalinity I ++ 0.41UVAeffluent 2 - -0.38UVA 3 - -0.37DOC 4 - -0.35SUVA_____________5__________-_______-0.32Table 3.10: Top Five Highest Correlating Parameters to Bromate for Single-LinearRegression Analysis of Round TwoParameterCTsWTRSUVAOzone DoseBromideAUVA254Rank12345Correlation Index r value++ 0.56-0.25+ 0.23+ 0.20-0.17Table 3.11: Top Five Highest Correlating Parameters to Bromate for Single-LinearRegression Analysis of Round ThreeParameter Rank Correlation Index r valueCTswiR 1 ++ 0.50Bromide 2 + 0.32Temperature 3 + 0.25UVA254-effluem 4 - . -0.25Alkalinity___________5__________+_______0.19In general, the results from the simple-linear regression analysis revealed that there were nooverwhelming trends between any one variable and bromate formation for the waters studied.However, the promotive or inhibitive trends from each parameter with respect to bromate41

formation were consistent. For example, bromide (+), SUVA (-), and CTswra (++) were shownin multiple rounds to be similarly correlated to bromate formation. Also, trends of temperature(+) and ozone dose (+) were shown as expected. DOC was relatively influential, as identifiedduring the first sampling round correlation ranking, and displayed a slight inhibitive effect onbromate formation.3.4.2 Composite Survey Database3.4.2.1 Descriptive Statistical AnalysisAs with each of the individual rounds, the cumulative survey database was summarized in theform of descriptive statistics. Table 3.12 displays the summary of these statistical indicators forthe overall pool of 78 samples. The average water temperature and pH were 20°C and 7.7,respectively. The average ammonia (0.18 mg/L as N) and alkalinity (100 mg/L as CaCO3) levelswere considered to be moderate and comparable to national averages for these parameters.Table 3.12: Cumulative Water Quality and Treatment Condition SummaryMean Std. Dev. Range10th % 50th % 90th %20 5.0 7.0 - 27 12 20 2653 44 2.0-180 6.0 42 1203.87 7.7 0.1-40.0 0.2 1.2 12.751 44 2.5 - 180 8.0 39 1206.5 13 0.1-72 0.2 2.0 187.7 0.7 6.2- 11 6.6 7.7 8.3100 63.3 6.5-280 30 98 1800.18 0.25 0.01 - 1.22 0.02 0.08 0.511.8 1.2 0.1-7.9 0.5 1.5 3.00.06 0.10 0.00 - 0.50 0.00 0.02 0.2021 15 2.0 - 82 5.0 18 350.9 1.3 0.0 - 4.7 0.0 0.3 3.03.1 1.73 0.8 - 8.9 1.5 2.6 4.80.069 0.053 0.012 - 0.260 0.023 0.061 0.1202.2 0.63 0.9 - 3.4 1.4 2.1 2.90.036 0.027 0.011-0.154 0.013 0.029 0.0660.034 0.032 -0.010-0.181 0.005 0.025 0.078ParameterTemperature (°C)Br" (ug/L)Br03'(ng/L)Br effluent (Ug/L)Br conversion to BrO3~(%)pHAlkalinity (mg/L as CaCO3)NH3-N (mg/L)O3 dose (mg/L)O3 residual (mg/L)HRT (min)CT SWTR (mg/L-min)*DOC (mg/L)UVA254(cm- 1)SUVA (L/mg-min)T *~> T\/ v -^effluent A r-ri ( v^/iil r*Tf\ ~ \ ^AUVA254 (cm' 1 )data not collected during the first sampling roundBromate levels varied significantly, from below the detection limit of 0.3 ug/L to an upper limitof 40 ug/L, with an average bromate concentration of 3.9 ug/L. Bromide conversion rangedfrom 0.1 to 72 percent, with an average conversion of 6.5 percent. In order to gain a betterunderstanding of bromate occurrence, a cumulative frequency distribution graph was developedfor each of the three rounds as well as the cumulative survey database. The graph, which isshown in Figure 3.2, plots bromate concentration (log-scale) on the abscissa and cumulativedistribution percentile on the ordinate. Percentile values of bromate occurrence can bedetermined from the plot as the percentage of values less than or equal to a given percent. The42

50l percentile value for the cumulative database is 1.2 ug/L, while the individual roundsproduced 50th percentile values of 1.6, 0.6,.and 1.1 ug/L. The average bromide concentrationwas determined to be 53 ug/L.10080 -60I 400>CM2000.1 1 10Bromate ConcentrationSecond Sampling Round° Third Sampling Round• First SampKg RoundAll Three Rounds100Figure 3.2: Cumulative Distribution of Bromate Formation in 78 SamplesThe waters in this study (at the point of ozonation) were not high in humic content, asrepresented by the average SUVA of 2.2 L/mg-min. DOC values ranged from 0.8 mg/L to 8.9mg/L, with an average value of 3.1 mg/L.3.4.2.2 Single-Linear Regression AnalysisLinear regression was performed on the cumulative database, and the results were againpresented in the form of a Pearson correlation matrix. The correlation matrix for all theparameters of the sample pool is listed in Table 3.13. Similar to the individual rounds, the topfive correlating parameters were identified using the +/- ranking scheme (as before, bromideconversion was excluded). The summary of the correlation index ranking is listed in Table 3.14;the overall most influential parameter was CTSWTR-CTswTR was shown to have the highest correlation with bromate as represented by an r value of0.48. None of the other parameters show a statistically significant correlation with bromate.These results indicate that bromate formation may be simultaneously dependent on numerousparameters.43

Table 3.13: Cumulative Pearson Correlation MatrixParameter DOC UVA2S4 SUVA NH3-N Alk fir' Temp pH O3 dose HRT CTSWTR Br-emuent Hi-"JJI converTTVA*J T ^254 effluent AUVA2S4 BrO 3"DOC 1.00 0.95 0.35 0.67 0.30 0.37 0.33 0.23 0.43 -0.02 -0.36 0.26 -0.20 0.87 0.83 -0.15UVA254 1.00 0.60 0.63 0.27 0.26 0.28 0.14 0.44 -0.01 -0.39 0.14 -0.21 0.87 0.91 -0.19SUVA 1.00 0.23 0.00 -0.02 0.00 -0.04 0.29 -0.09 -0.40 -0.06 -0.14 0.43 0.63 -0.18NH3-N1.00 0.08 0.37 0.42 0.36 0.30 -0.11 -0.29 0.40 -0.23 0.71 0.45 -0.14Alkalinity1.00 0.32 0.14 0.08 0.03 -0.07 -0.08 0.13 -0.06 0.23 0.25 0.21Br"1.00 0.33 0.35 0.25 -0.20 -0.04 0.94 -0.22 0.31. 0.18 0.22Temperature1.00 0.19 0.20 -0.39 -0.38 0.28 -0.19 0.27 0.23 0.14pH1.00 0.02 -0.30 -0.20 0.44 -0.22 0.24 0.04 0.09O3 dose1.00 0.12 -0.27 0.18 -0.07 0.31 0.45 0.16HRT1.00 0.44 -0.26 0.48 0.02 -0.04 0.03CTgWTR1.00 -0.08 0.38 -0.39 Br effluent**1 converAUVA2S4BrO3"1.00 -0.24 1.00 0.24 -0.22 1.00 -0.37 0.03 -0.16 0.60 1.00 0.480.140.54-0.19-0.161.00Samples 78 78 78 78 78 78 77 78 75 66 40 78 78 78 78 78Table 3.14: Top Five Highest Correlating Parameters to Bromate for Single-Linear Regression Analysis of the CumulativeDataParameterCTswTRfir'AlkalinityUVA254UVA254-effluentRank Correlation Index r value1++ 0.482+ 0.223+ 0.214-0.195-0.19

3.5 DISCUSSIONWith the exception of the three French waters, the composite results from this survey should begenerally indicative of levels of bromate formation and the conditions under which bromate isformed, in the United States. This study was complimentary to a European study conductedearlier, entitled "A Survey of Bromate Ion in European Drinking Water" (Legube, 1996). Theresults of the European study were compared against those of this study.3.5.1 United States Bromate Formation SurveyOn average, bromate formation in 88 percent of the survey waters with current treatment (basedon Giardia inactivation, at ambient pH) was less than the Stage 1 Disinfectant / Disinfection By-Product 10 ng/L bromate maximum contaminant level. Conversely, 12 percent of the samplesanalyzed were shown to be in excess of the MCL indicating some form of bromate controlstrategy may need to be implemented. It was also observed that under current treatmentconditions, typically less than 10 percent of the bromide is converted to bromate (mass bromidebasis).The average CTswra value reported (a subset of 40 samples) was 0.91 mg/L-min. This can bethought of as an average CT value under current ozonation levels targeted for Giardiainactivation. Because Cryptosporidium is becoming the controlling organism dictating ozonedisinfection levels, higher CT values will be needed in order to achieve an adequate log-kill. Acurrent estimate of CTfor 1-log inactivation of Cryptosporidium at 15°C using ozone is 2.5 mgmin/L(Oppenheimer, et al., 2000). This fact, coupled with the observation that CT was the mostinfluential parameter on bromate formation, could result in an increased average bromate levelproduced during disinfection at water treatment plants that use ozone as the new levels ofdisinfection are implemented.3.5.2 Comparison to European Bromate Formation SurveyThe European Union (EU) Bromate Survey was comprised of thirty-eight European waterworksand spanned two sampling rounds, the first during the summer and fall of 1993 and the secondduring the spring of 1994 (Legube, 1996). The EU survey included the same water quality andtreatment condition parameters as the US survey, except for the UV analyses (UVA, SUVA,UVA after, and AUVA254) and CT. Thus, the EU and US survey were compared based on the 12remaining parameters monitored. A composite analysis of the EU data is presented in Table3.15.Similar values of bromate formation were measured in both surveys. The average concentrationswere 3.6 ug/L and 3.9 ug/L, for the EU and this study, respectively. The average temperature,pH and DOC values were generally consistent. The primary differences in water quality wereobserved with the alkalinity (139 mg/L for EU vs. 100 mg/L for US), ammonia-N (0.08 mg/L vs.0.18 mg/L) and bromide ion concentrations (84 ug/L EU vs. 53 ug/L US).45

Table 3.15: Water Quality and Treatment Condition Summary of European UnionBromate SurveyParameterStd Dev Range10th % 50th % 90th %Temperature (°C)9.0-•26.8Bf(ng/L)10-•400BrO3' (ug/L)0.05 -19.62.5--430Br'after (f^g/L)Br conversion to BrO3'(%)pHAlkalinity (mg/L)NH3-N (mgVL)O3 dose (mg/L)HRT (min)DOC (mg/L)Mean17.4843.6874.77.31390.081.6112.73.6871.33.7482.65.580.5676.20.130.987.521.630.15.76.50.0010.13.00.25-30-8.6-277-0.60-4.2-40-8.512.5201.0130.56.4250.000.74.01.417.0602.0592.67.51510.051.59.02.222.01558.8187127.92490.203.0205.0Number6769706869686766605569As a final comparison, a Pearson correlation matrix was calculated for the EU survey to probethe most influential parameters in relation to their effect on bromate (Table 3.16). This analysisindicated that the most influential parameters were determined to be ozone dose, HRT andtemperature, followed by pH and ammonia-nitrogen. It generally appeared that for the waterssampled in both surveys, bromate formation appeared to be influenced more by ozone treatmentconditions than water quality.46

Table 3.16: Pearson Correlation Matrix for European Union Bromate SurveyParameter -0.16 0.06-0.24 -0.180.02 0.03-0.43 -0.100.36 0.400.17 0.240.25 0.470.33 0.45-0.38 -0.061.00 0.84DOC NH3 Alkalinity Br' Temperature pH O3 dose HRT Br"after Br" conver BrO3"DOC 1.00 0.30 -0.13 0.37 0.00 -0.16 0.43 0.08 0.43 NH3-N 1.00 -0.27 0.19 -0.10 -0.46 -0.04 -0.13 0.19 AlkalinityBrTemperaturePHO3 doseHRTBr"after**r conver1.00 0.00 1.00 -0.09 -0.24 1.00 0.43 -0.01 0.16 1.00 -0.04 0.11 0.09 0.07 1.00 0.08 -0.07 0.35 0.14 0.25 1.00 0.08 0.95 -0.24 0.00 0.22 -0.01 1.00 BrO3 _______________________________________________________________1.00Samples_____69 66 67 69_____67_____68 60 55 68_____69_____70

CHAPTER 4. TRUE-BATCH INFLUENCE OF NOM AND TEMPERATURE ONBROMATE FORMATIONThis chapter emphasizes the use of true-batch simulations to probe important issues related todeveloping a comprehensive understanding of bromate formation for different levels ofdisinfection, as represented by CT^or ozone exposure (OE). These include the influence of bothNOM's concentration and character on bromate formation during disinfection and temperatureeffects on both bromate formation and disinfection. Each of these issues was probed through theuse of completely-mixed true-batch reactors to estimate bromate formation potential (FP) atdifferent levels of ozone exposure.4.1 INFLUENCE OF NOM ON BROMATE FORMATIONUnderstanding the influences of NOM is critical to elucidating the mechanisms that contribute tobromate formation and affect disinfection (CT or OE). Distinct formation pathways have beenidentified including the molecular ozone pathway (direct oxidation) and the hydroxyl radicalpathway (indirect oxidation). Initial research attributed the majority of bromate formation innatural waters to the direct pathway, with a minimal influence from the indirect pathway (vonGunten and Hoigne, 1994). Recent research has indicated evidence to the contrary, suggestingthat the hydroxyl radical pathway can contribute up to 100 percent of the bromate formation insource natural waters (Ozekin et al., 1998; von Gunten & Oliveras, 1998).The effort to develop bromate minimization strategies requires an understanding of the influenceof specific pathways for bromate formation. Natural organic matter can affect the chemistry ofozone processes in several ways. Direct reactions between ozone and NOM can effectivelyreduce the extent of ozone and bromide reactions. Specific NOM sites (e.g., humic and fulvicacids) can react with hydroxyl radicals to produce chain carriers of ozone decomposition, thusincreasing the hydroxyl radical formation rate. Other NOM sites may react with hydroxylradicals to produce compounds that do not react with ozone, and thus inhibit the ozone decaycycle without further production of oxidizing agents. Overall, variations in NOM can influencethe ratio of hydroxyl radical exposure and ozone exposure with natural waters, resulting invarying bromate formation rates even in those waters with similar water qualities (Elovitz et al.,1999b).The dependence of bromate formation on various inorganic and organic parameters has beenextensively investigated. However, organic parameters have mainly consisted of DOCconcentrations, specific NOM fractions, or molecular size of NOM. The role of functional NOMfractions has not been investigated, except for limited research on hydrophobic organic acids(Westerhoff, 1995). One objective of this research effort was to correlate NOM characteristicswith bromate formation, specifically looking at the role of functional fractions and averagemolecular size. A correlative statistical analysis was used to determine the influence ofinorganic and organic parameters using a cumulative database of the fourteen project sourcewaters.49

4.1.1 Source WatersFourteen source waters were evaluated representing a geographic distribution of ozone plantsthroughout North America and Europe. Samples were collected from utilities in California (6);Texas (3); Florida (1); New Jersey (1); Michigan (1); Ottawa; Canada (1); and Paris, France (1).One utility used a groundwater source, one used a combined surface/ground water mix, and theremaining twelve utilities used surface water sources.4.1.2 True-Batch Ozonation ExperimentsTrue-batch ozonation experiments were used to assess ozone exposure and the resultant bromateformation potential. As indicated in Chapter 2, experiments were conducted under constantconditions for pH (7.0), temperature (20°C) and ozone dose (1 mg-Oa/L per 1 mg-DOC/L).After dosing the samples with ozone stock solution, kinetic data were collected as ozone residualmeasurements with time. Ozone residual measurements were taken every minute for the firstfive minutes and then were gradually spaced over longer intervals. Integration of the generatedozone decay curve was used to estimate OE. Once the ozone residual had decayed to below theminimum detection limit, samples were collected from the reactor and analyzed for bromate.The true-batch reactor was mathematically equivalent to plug-flow conditions, relating ozonedecay over time. Moreover, kinetics for ozone decay can be represented by a first-order rate law:where, [Os] = ozone concentration, mg/Lk = experimentally derived first-order rate constant for ozone decayThe relationship between bromate and OE has been shown to be approximately linear under nonbromidelimiting conditions. To compare bromate formation between source waters at a givenOE, the linearity assumption was used to develop a relationship between the experimentallyderived OE and bromate concentrations. A linear function passing through the origin wascalculated for each set of experimental results. The resultant linear function is represented as:[BrO3"]=K*OE;where, K = slope coefficient, pg/mg-minThe different source waters were then compared against one another using the K value as anindicator of expected bromate formation at a given OE.The linear representation of the bromate formation versus OE or CT relationship was meant to bea simple model for trending purposes. For a given reactor, the slope (K = BKV/OE (or CT)) isreflective of the set of water quality and ozone dose conditions that affect both bromateformation and disinfection (CT or OE). For different reactors, the slope (K) is also reflective ofthe unique hydrodynamic conditions. This simple model was not intended to be used forpredictive purposes but rather for trending comparisons among different water quality conditions50

for a given reactor, and among different reactors for a given set of water quality conditions.Departures from linearity are most strongly influenced by bromide-limiting conditions.4.1.3 Results4.1.3.1 NOM CharacterizationBefore investigating trends in the formation of bromate at various levels of disinfection, initialefforts were focused on characterizing the natural organic matter in the various project watersamples to determine if these characteristics might affect bromate formation. Thecharacterization of NOM properties consisted of measures of DOC concentrations, spectroscopicproperties, fractional DOC distribution, and molecular size distribution. Results of the analysesare presented in Table 4.1; refer to Section 2.4 for extended descriptions of the methods andanalyses used to characterize the parameters. These parameters and properties collectivelydescribe the size, structure, and functionality of NOM; these are important because NOM exertsan ozone demand and serves as both a scavenger and promoter of hydroxyl radicals. All sampleswere filtered through 0.45 urn filters and initially analyzed for DOC and UVA.Representative UVAioo-soo spectra for each water are presented in Figure 4.1. UVAaoo-soo can beconsidered to reflect the specific character of water in terms of aromatic carbon content. TheCGE spectrum is characterized by a very high absorbance below 240 nm; this phenomenon maybe due to interference by inorganics (i.e., NOs") present in the matrix. The nitrate level in theCGE sample was determined to be 19.6 mg/L, corroborating the noticeable difference inabsorbance compared to the other waters.Specific ultraviolet absorbance was calculated by normalizing the UVA254 with DOC. SUVAhas been shown to correlate well with both aromatic carbon content and aliphatic carbon content(inversely) of NOM isolates (Westerhoff et al., 1999). SUVA is a parameter that has been usedto relate relative characteristics of humic content; a high SUVA represents NOM that largelyconsists of humic material, and a lower SUVA indicates a less-humic nature of the NOM.Conventional treatment practices (i.e., coagulation) and ozone treatment are known to reduce thehumic nature of a water, effectively shifting the molecular size distribution and humic nature tolower molecular sizes and a non-humic nature. The source waters, arranged from high SUVAdescending to low SUVA, are presented in Figure 4.2. The range of SUVA values observed forthe water sources was from 3.8 L/mg-m (WPB) to 1.4 L/mg-m (AMA). Generally, waters withhigher SUVA are more reactive with ozone.Through the use of macroporous, nonionic resins, the NOM was fractionated into hydrophobic,transphilic, and hydrophilic fractions. Examples of the compounds in the transphilic (TPI)fraction includes carboxylic acids, amino acids, carbohydrates, and volatile hydrocarbons. Thehydrophilic (HPI) fraction is characterized by sugar acids, volatile fatty acids, hydroxy acids, andcomplex polyelectrolytic acids with many carboxylic and hydroxyl functional groups. Thehydrophobic (HPO) fraction is mostly made up of humic and fulvic substances that exhibit anaromatic nature and contain electron rich double bonds and conjugate bonds that arepreferentially oxidized by ozone (Westerhoff et al, 1999; Thurman, 1985).51

K)Table 4.1: NOM Characterization of Raw Source WatersWater SUVA Natural Organic Matter FractionHydrophobic Transphilic Hydrophilic Hydrophobic TransphilicWPBHOUCCDNJASACCGESPWLAWACDOTTDALANNCRWAMAAverageMedianStd DevRange(L/mg-m) (% NOM)3.83.53.42.72.62.52.42.32.22.12.01.91.61.42.52.40.71.4-3.8666254515347455449524245453550507.935-66(% NOM)181720211719232021202224242721212.917-27(% NOM)162126282934322631283630313729305.616-37(mg-C/L)6.95.81.01.50.90.71.31.00.81.4.9.1.2.0.9.2.90.7 - 6.9(mg-C/L)1.91.60.40.60.30.30.60.40.40.51.00.60.70.80.7 •0.60.50.3-1.9Hydrophilic WeightAveraged(mg-C/L) (Daltons)1.72.00.50.80.50.50.90.50.50.71.60.80.81.00.90.80.50.5-2.0Molecular Weight PolydispersivityNumberAveraged(Daltons)1350 10201.31250 7201.71250 9601.31020 5801.81210 9151.3810 6401.31090 8501.31300 9401.41590 11001.4885 7301.2985 7101.4680 5201.3980 6301.6990 7901.31099 7931.41055 7601.3241 175 0.2680-1590 520-1100 1.2-1.8

u11.00.8°- 60.40.21.CGE2.WPB3.HOU4.NJA5.SPW6.CCD7.AMA8. CRW9.ACD10.DAL11. ANN12.0TT13. SAC14. LAW0.0200- 220 240 260Wavelength (nm)280 300Figure 4.1: Source Water Ultraviolet Adsorbance Spectra129- 10E• SUVA(L/mg-m)D DOC (mg/L)uo/——NIWPB HOU CCD NJA SAC CGE SPW LAW ACD OTT DAL ANN CRW AMAFigure 4.2: Source Water DOC and SUVA Values53

NOM fractions were calculated on both a relative distribution basis (mass of fraction per mass ofbulk DOC) and a mass (mg-C/L) basis to account for the difference in DOC concentrations. Forthose waters with higher DOC concentrations, the mass of the fractions were much larger thanfor waters having a low DOC. For example, HOU and SAC waters have equal percentages ofthe TPI fraction (17 percent), but the mass varies between, 1.6 mg-C/L for HOU water and 0.3mg-C/L for SAC water.The percent of NOM fractions for all of the waters are presented in Figure 4.3. The HPOfraction predominates (average = 50 percent), followed by the HPI (29 percent) and TPI (21percent) fractions. The distribution of fraction percentages was relatively consistent except forthree waters; WPB and HOU were observed to reflect up to 66 percent of the HPO fraction andAMA analyses indicated a balance between the HPO and HPI fractions. Both of these watershad DOC concentrations significantly greater than the other waters. The fractions generallyfollow a trend relating to SUVA. The waters with high SUVA show a predominant percentageof HPO matter; waters lower in the SUVA range exhibit an increasing percentage of TPI matterand, to a somewhat lesser extent, HPI matter.100%80%Io03Io>g60%40%20%0%WPB HOU CCD NJA SAC CGE SPW LAW ACD OTT DAL ANN CRW AMASource WaterFigure 4.3: Distribution of NOM FractionsApparent molecular weight (AMW) results ranged from 680 to 1590 daltons based on weightaveraged (Mw) values, with a median of 1055 daltons. The range for the number averagedAMW (Mn) was observed to be 520 to 1100 daltons with a median of 760 daltons. Arepresentative size exclusion chromatogram for CCD water is presented in Figure 4.4. As withthe fraction percentages, the molecular weight distribution is observed to follow similar trends,hi general, as SUVA decreases, the AMW, calculated as Mw, decreases. The AMW calculatedas Mn did not portray a similar trend and was variable for all waters. Polydispersivity was usedas a measure of NOM heterogeneity. The observed polydispersivities ranged from 1.2 (OTT) to54

1.8 (NJA). A value of 1.0 indicates ideal homogeneity of the AMWs; therefore, values closer to1.0 indicate more homogeneous and uniform NOM.8000i [ i i inMwAve =1250 daltonsStDev = 80 daltons6000 h CV = 6.1%I ICCDRunlCCD Run 2CCD Run 3oaoC3i_40002000Ave = 960 daltons•StDev = 35 daltonsCV = 3.5%PolydispersivityAve =1.3StDev = 0.07CV = 5.3%010 100 1000Molecular Weight (daltons)Figure 4.4: Size Exclusion Chromatography Chromatograms for CCD Water1000C4.1.3.2 True-Batch Ozonation ResultsPrepared aliquots of raw water samples were ozonated per the true-batch procedure explained inSection 2.2.1.1. The data derived from these experiments were used to estimate ozone decay,bromate formation potential (FP), and OE. The slope coefficient, K, for the bromate FP versusOE relationship was calculated based on the experimental data. Table 4.2 displays the overallresults for the true-batch ozonation of the fourteen source waters.Ozone Decay KineticsOzone decay rates were estimated by fitting a first-order rate equation to the measured ozonedecay data. The decay curves developed for the fourteen waters and Milli-Q water are presentedin Figure 4.5 and Figure 4.6. The curves for low DOC waters (3 mg/L), are presented separately. For all waters, a rapid initial decay rate was observed,characterized by a linear (constant) decay. Linearity for this region is assumed since the ozonedecay was very rapid and accurate measurements could not be reproducibly made until oneminute had passed. This initial phase could probably be modeled as a steep exponential drop inozone residual. For consistency, however, the first stage of ozone decay was characterized byozone decomposition as expressed by:55

= [O3]o - [O3]twhere, Ainjtiai represents the amount of ozone loss during this phase of the reactionand reflects a "pseudo" zero-order reaction (Westerhoff, 1995). The initialperiod persisted up to three minutes, followed by an apparent pseudo-firstorder rate of ozone decay.Table 4.2: Summary of Bromate Formation Potentials and Ozone Exposure ResultsWaterBr"OE Br03 " K* Dilution£TAOs initial-')(Hg/L) (mg-min/L) (Hg/L) (Hg/mg-min) (%) (mg/L) (xlO"3 secAMA WPB SPW CRW ANN ACD CCD LAW CGE HOU NJA DAL OTT SAC Mean Median 182119 13166 6048 37 3022 15 18 18 15 47 5842 18 3.3 12 27 1123 5.0 12 7.9 4.5 3.5 6.9 4.5 6.0 10 7.4 35 4.2 23 18.1 11 17 8.5 7.6 1.2 1.9 1.5 2.4 1.4 7.7 107.7 1.90 1.27 1.92 0.660.970.73 1.70 0.650.150.42 0.43 0.35 0.31 1.28 10.7 9 30 10 8 8 13 6 8 5 28 12 14 10 6 12 9.5 1.3 6.6 1.0 1.7 1.0 1.5 0.5 0.9 0.5 6.7 1.6 2.2 1.2 0.6 1.9 1.3 1.3428.42.491.022.911.025.231.311.9322.711.54.968.483.2373.1StdDev 51 7.7 10.0 0.6 7.7 2.0 8.5Range 15-182 3.3 - 27 1.0-35 0.15-1.92 5-30 0.6-6.7 1.02-28.4* Based on diluted sample bench-scale experimentst First order decay constants estimated using ozone decay data and exponential curve fitNatural organic matter has been shown to exert an influence on ozone decay (Westerhoff et al.,1999). Organic matter of an aromatic nature has been shown to be highly reactive with ozone.The waters with HPO fractions greater than 50 percent (WPB, HOU, CCD, NJA, SAC, OTT,LAW) were generally observed to have higher ozone decay rate constants ranging from 2.49x10"sec" to 28.4x10"3 sec" 1 . The range of rate constants for those waters with less than 50 percentHPO (CGE, SPW, ACD, DAL, ANN, CRW, and AMA) was less variable, ranging between1.02x10" sec" 1 and 4.96x10"3 sec" 1 . These decay constants are in agreement with published datafor natural waters (Elovitz et al, 1999b).56

Residual Ozone Concentration (mg/L) Residual Ozone Concentration (mg/L)99IS3ereIInCfQ erOonC/5Orsre1 ooorereOsoBreOrens9onVcroIO NOorerersne9oIoo

After ozonation, the sample was measured for AUVA254. These results are presented in Table4.3. The change in the aromatic character of the NOM was represented by the decrease in theUVA254 after ozonation. Representative spectra, normalized to diluted DOC, are presented inFigure 4.7 for comparison. The difference of UVA at a particular wavelength is indicative of thereactivity of specific NOM sites with ozone; decreases in UVA254 is indicative of the reactivearomatic portions of the NOM molecules (Westerhoff et al., 1999). The observed AUVA254ranged from 0.018 cm" 1 for AMA to 0.139 cm" 1 for WPB. The relative change in the WPB andHOU waters was far greater than the other AUVA254 values observed for the remaining waters(0.018 cm" 1 to 0.046 cm" 1). Both the WPB and HOU waters were characterized by predominantHPO fractions. The CGE spectrum was influenced by a high nitrate concentration and thereforeshould not be considered as a true representation of NOM reactivity with ozone.I1. LAW2. HOU3. WPB4. CGE5. NJA6. CRW7. ACD8. SPW9. ANN10. OTT11. SAC12. CCD13. AMA14.DALP0200 220 240 260Wavelength (nm)280 300Bromate Formation PotentialsFigure 4.7: ASUVA Spectra of Ozonated Project WatersOnce the ozone residual concentration in each of the bromate formation potential tests (dosed 1mg Os per mg DOC) had decayed to below detection limits, sample aliquots were collected forbromide and bromate analyses. The results are presented in Table 4.3. In order to attempt toclose the bromine mass balance, total organic bromine (TOBr) was modeled using a relationshipdeveloped by Amy et al. (1997). The modeling results predicted only 0.0 to 2.5 ug/L of thebromide might be incorporation into TOBr. Alone, these predicted levels of bromideincorporation into TOBr would not be able to explain the amount of unaccounted bromide.58

Dilution(%)302861265108131014889121085-30WaterWPBHOUCCDNJASACCGESPWLAWACDOTTDALANNCRWAMAMeanMedianStd Dev.RangeAUVA254(cm' 1)0.1390.1460.0260.0350.0230.0210.0400.0420.0460.0310.0400.0320.0230.0180.0470.0330.0410.018-0.146InitialBr'(Hg/L)1702139215023145335517216572200Table 4.3: True-Batch Post-Ozonation Water Quality ParametersResidualBr'«L)926.0261543156413406.39.758301103828336.0-11BrO3(Hg/L)4.21.98.51.57.7'1.2237.6131.42.4111835107.7101.2-35UnaccountedBr'*(Hg/L)75.413.87.75.12.27.366.615.37.09.89.80.0*30.768.1ModeledTOBr**(ug/L as Br')3.40.10.20.10.00.01.90.10.40.10.10.70.62.90.80.21.10.0 - 2.5Br' to BrO3'Conversion(%)2.27.9145.1103.411161768.312171210114.92.2-17Br"Incorporation(%)236029198315157175946355403635203-60* "0.0" value indicates that the calculated Br" recovery is greater than the estimated Initial Bromide concentration (adjusted for dilution);Unaccounted Br"=[Initial Br'*(l-dilution)]-(residual Br')-(BrO :r as Br")]** TOBr estimated using Amy et al. (1997) TOBr Model where: [TOBr]=1.004(Br-/ 765(DOC)-055 '(pH)-3 -916(NH3-N)c 13(O3) U35(TIC)-°'".;where, TIC is total inorganic carbon (mg/L)

The average bromide conversion to bromate was 10 percent, with a range from 2.0 (WPB) to 17percent (CRW). The total reduction in bromide concentration, presumably as result ofincorporation into bromate, hypobromous acid, hypobromite and TOBr, ranged from 3 (ANN) to60 percent (HOU), with an average of 36 percent. In other research, HOBr had been observed toaccount for 5 to 50 percent of initial Br" molar concentration (Westerhoff, 1998).For these ozonated waters, the calculated ozone exposure values ranged from 3.3 mg-min/L forWPB to 27 mg-min/L for CRW. Bromate concentrations measured after the true-batchozonation were referred to as the formation potential (FP) concentrations. As discussed earlier,the bromate formation potential was plotted against the ozone exposure for the given water andfit with a linear function passing through the origin. Past research has shown an approximatelylinear relationship between bromate formation and ozone contact if bromide was not limiting.Additional tests were performed with LAW at elevated ozone doses to determine if this linearrelationship would be observed in the true-batch reactor. These bench-scale tests run with LAWappeared to support this general trending approach, as shown Figure 4.8.0 5 10 1520Ozone Exposure (mg-min/L)Figure 4.8: Linear Relationship Between Bromate Formation and Ozone Exposure (LAW)Bromate formation potential and ozone exposure for each water are plotted in Figure 4.9. Themaximum observed bromate FP was 35 ug/L (AMA) with an OE of 18 mg-min/L, and theminimum was 1.2 ug/L (CGE) with an OE of 7.9 mg-min/L. The mean FP and OE values were10 ug/L and 10 mg-min/L, respectively, though the corresponding median values were 7.7 ug/Land 7.4 mg-min/L. Only the data from the LAW 1:1 ozone dose ratio were included in theanalysis. The slope coefficients, K, for each water were calculated using the linear function, orquite simply [BrO3 ~ FP]/OE (Table 4.2). Assuming linearity, the slope coefficients can be usedto estimate bromate concentration as a function of OE. These coefficients ranged from 0.1560

ug/mg-min for CGE to 1.92 ug/mg-min for SPW. High K values indicate a water's propensityto form more bromate with an incremental increase in OE when compared to lower K values.oOHesoos2ca25201510SPW ———AMACCD ----- SACWPB x ANN---- ACD ———CRW*~~LAW -^—NJAa— HOU —o— DAL+--OTT —•—CGEl-Log Cryptosporidium Inactivation(1.2 - 2.9 mg-irdn/L @ 20°Q10 ^g/L Bromate MCL0 3 6 9 12Ozone Exposure (mg-min/L)Figure 4.9: Bromate Formation Potential and Ozone Exposure (20°C, pH 7)Figure 4.9 also shows a representative inactivation range for 1-log inactivation ofCryptosporidium, 1.2 to 2.9 mg-min/L, based on Oppenheimer et al. (2000) and Rennecker et al.(1999) at 20°C. Given the 10 ug/L MCL and using the upper end of this representativeCryptosporidium inactivation range (2.9 mg-min/L), bromate formation should not be a problemfor any water with a slope coefficient K consistently less than 3.4 ng/mg-min at 20°C. Thelargest K value was only 1.9, 44 percent lower than the predicted maximum. Consequently,bromate minimization strategies may not need to be investigated for these waters at 20°C if only1-log Cryptosporidium inactivation was deemed necessary. However, this might not be the casefor higher levels of Cryptosporidium inactivation or ozone exposure.Compliance AssessmentThe data derived from the true-batch experiments were used to assess the impacts of increasedCT requirements for the inactivation of Cryptosporidium. Ozone has been shown to be aneffective disinfectant for inactivation of target pathogens, particularly Cryptosporidium (Finchand Li, 1999). With the expected promulgation of up to 2.5-log of additional Cryptosporidiumremoval, ozone CT will need to be increased to achieve these levels of compliance. Currentresearch efforts are attempting to discern the necessary CT to provide ozone inactivation.Oppenheimer et al. (2000) and Rennecker et al (1999) used the Chick-Watson model to developsuggested CT values for inactivation across a range of temperatures from 0.5°C to 30°C and log-61

kills from 0.5 to 6.0. Using the K values determined for these project waters, bromate formationwas predicted using the suggested Oppenheimer et al. (2000) and Rennecker et al. (1999) CTvalues for 1-log, 2-log and 3-log inactivation at 20°C. The results from this analysis arepresented in Table 4.4. The analogous experimental parameter to CT is the OE calculated as afunction of observed ozone decay data. The CT value incorporates ozone decay into estimationof inactivation for pilot- and full-scale applications; OE incorporates ozone decay into estimationof true-batch inactivation and bromate formation at the bench-scale.Table 4.4: Estimated Bromate Formation for Cryptosporidium Inactivation (20°C, pH 7)Source WaterSPWAMACCDSAC*WPBANNACDCRWLAWHOUDALOTTNJACGEspiked to 47 ng/L Br"K1.921.901.701.281.270.970.730.660.650.420.350.310.300.15~l-Log Inactivation(1. 2-2.9 mg-min/L)2.3-5.62.3 - 5.52.0-4.91.5-3.71.5-3.71.2-2.80.9-2.10.8-1.90.8-1.90.5 - 1.20.4-1.00.4 - 0.90.4 - 0.90.2 - 0.4Bromate Formation Potential~2-Log Inactivation(2.3-5.2 mg-min/L)4.4 - 104.4 - 9.93.9-8.82.9 - 6.72.9 - 6.62.2 - 5.01.7-3.81.5-3.41.5-3.41.0-2.20.8- 1.80.7-1.60.7-1.60.3 - 0.8~3-Log Inactivation(3.5-7.5 mg-min/L)6.7 - 146.7 - 146.0 - 134.5 - 9.64.4 - 9.53.4 - 7.32.6 - 5.52.3 - 5.02.3 - 4.91.5-3.21.2-2.61.1-2.31.1-2.30.5-1.1The results shown in Table 4.4, indicate that depending on which data the EPA decides to utilizefor the development of the ozone CT values necessary for various levels of Cryptosporidiuminactivation, bromate formation may or may not be an issue for many water sources. Based onusing the suggested Oppenheimer et al. (2000) CT values, bromate formation at 20°C would notbe a concern for any of these project waters at 20°C, even in excess of credit for 3-logs ofinactivation. The more conservative Rennecker et al. (1999) suggested CT values indicated thatbromate formation at 20°C might exceed 10 ug/L for some waters (SPW, AMA, CCD) at orabove 2-logs of Cryptosporidium inactivation.Should a more stringent 5 ng/L MCL be implemented and the more conservative Rennecker etal. (1999) suggested CT values be used, SPW, AMA and CCD would be impacted at 1-log ofCryptosporidium inactivation by ozone. At 2-logs, the spiked SAC, WPB, and ANN would jointhe list of impacted project waters. At 3-logs of inactivation, nine of the project waters wouldneed to have some form of bromate minimization strategy in place at 20°C.62

BrConv OE BrO3-FP-0.11 0.31 0.27-0.51 -0.41 -0.390.02 0.31 0.73-0.44 -0.30 -0.25-0.48 -0.39 -0.32-0.44 -0.68 -0.55-0.35 -0.54 -0.620.43 0.63 0.770.29 0.46 0.47-0.49 -0.40 -0.33-0.46 -0.29 -0.16-0.42 -0.27 -0.160.29 0.10 0.040.26 0.06 0.170.01 0.05 -0.20-0.39 -0.35 -0.331.00 0.74 0.571.00 0.711.00o\U)Parameter Alk NH3 Br DOC UVA SUVAAlk 1.00 0.21 0.54 0.15 0.17 0.01NH3 1.00 0.19 0.74 0.72 0.46Br 1.00 0.28 0.24 -0.11DOC 1.00 0.98 0.61UVA 1.00 0.73SUVA 1.00HPO%TPI%HPI%HPO-DOCTPI-DOCHPI-DOCAMW-MwAMW-MnPolyAUVABr ConvOEBrO3- FPTable 4.5: Pearson Correlation Matrix for Bromate Formation Potential ExperimentsHPO%-0.030.44-0.210.640.750.881.00TPI%0.07-0.270.53-0.38-0.50-0.78-0.841.00HPI% HPO-DOC0.02 0.15-0.48 0.730.01 0.25-0.69 0.98-0.79 0.99-0.83 0.69-0.96 0.730.66 -0.461.00 -0.781.00TPI-DOC0.140.770.380.970.930.500.50-0.21-0.600.951.00HPI-DOC-0.020.690.250.880.800.340.30-0.12-0.360.830.931.00AMW-Mw0.220.190.070.350.390.460.51-0.42-0.460.320.180.071.00AMW-Mn Poly0.38 -0.310.14 0.080.23 -0.280.17 0.270.23 0.240.36 0.140.38 0.17-0.32 -0.08-0.33 -0.180.16 0.240.04 0.25-0.11 0.330.88 0.121.00 -0.361.00AUVA0.080.630.160.970.98.0.710.76-0.52-0.790.970.890.790.430.230.281.00

The results show that at 20°C, the overall impact of increased CT on low-bromide waters (

4.2 TEMPERATURE EFFECTS ON BROMATE FORMATION AND DISINFECTIONWhile the influence of temperature on disinfection can be represented by temperature-dependentCT (or OE) values, the effects of temperature on bromate formation have not been extensivelystudied; few studies report results for variations (e.g., seasonal) in temperature during ozonation.Recent efforts to characterize the impacts of variable temperatures have focused on thedecomposition of ozone and the resultant ozone exposure associated with stabilized ozoneresiduals at lower temperatures. Elovitz et al. (1999b) studied the effects of reaction temperatureon the ozonation of natural waters and observed that ozone decay rates decreased more than anorder of magnitude, from l.lxlO"2 sec" 1 to 6.0X10"4 sec" 1 , as temperatures were lowered from35°C to 5°C. To assess the impact of temperature on the indirect pathway, these authors used theRet concept (=[OH»]/[O3J) to conclude that temperature does not have an impact on hydroxylradical exposure. This was attributed to the relatively low activation energy for reactions withhydroxyl radicals, which are typically in the 5 to 10 kJ/mol range.Bromate formation under variable temperature has been suggested to be a function of theincreased reaction rates with bromide species (Siddiqui and Amy, 1993; Song, 1996). Siddiquiand Amy (1993) observed an increase in bromate formation of 20 percent, on an ozone dosebasis, as temperature was increased from 20°C to 30°C in semi-batch reactor experiments. Otherstudies utilizing various batch reaction systems indicated similar increases in bromateconcentrations over similar temperature ranges, up to a 50 percent increase between experimentsperformed at 5°C and 20°C (Siddiqui et a., 1995). It should be noted, however, that the bromideconcentrations for these experiments were 1,000 jj.g/L or greater. The effects of temperature onlow bromide waters have not been studied, but it would be expected that these waters wouldexhibit similar trends in bromate reduction with decreased temperature.Of paramount practical interest is the effect of temperature variation on the inactivation ofpathogens. Cryptosporidiwn has been shown to be more resistant to inactivation with decreasingtemperature (Oppenheimer et al., 2000; Finch and Li, 1999; Rennecker et al., 1999). SuggestedCT values reflect this resistance as they increase three to ten-fold over a temperature range from20°C to 5°C; the implications on bromate formation are obvious. With increased CTrequirements, the disinfectant dose or contact time must be increased, which in turn increases theprobability of forming bromate concentrations in excess of observed baseline conditions. Testswere conducted in this study to investigate the impact of temperature on bromate formation andcorresponding disinfection (CTor OE).4.2.1 Temperature Controlled True Batch OzonationFive waters were chosen to be used in temperature-controlled true-batch ozonation experiments:AMA, SPW, CCD, ANN and OTT. Water quality parameters for these waters were presentedpreviously in Chapter 2. The five samples were adjusted to a pH of 7.0 and buffered with 5 mLof 1 mM phosphate buffer. The reactor was constructed similar to the true-batch reactor, withthe exception of a glass water jacket. Initial tests were run on the reactor and cooling system toassess the control of temperature over time. Cooling water was recirculated through a coolerequipped with a recirculating pump. With this system, the resulting reactor sample could be65

maintained at 10 ±1°C for up to four hours. Temperature variations within the reactor wereobserved to vary less than 0.3°C along its height. Ozonation was performed in the same manneras the preceding true-batch experiments discussed in Section 4.1, and ozone kinetic data wererecorded over time.4.2.2 ResultsResults of the temperature-controlled true-batch ozonation experiments were used to assessbromate formation potential and estimate bromate concentrations based on increased CTrequirements for Cryptosporidium inactivation at various temperatures. Results from the 10°Cexperiments for the five water samples are presented in Table 4.6.ParameterInitial Bromide* (ug/L)Br(V(ug/L)Residual Br" (ug/L)Unaccounted Br"* (fig/L)Table 4.6: Results for True-Batch Ozonation at 10°CBr' to BrO3~ Conversion (%)Total Br" Incorporation (%)AUVA254 (cm'1)SUVA (L/mg-cm)OE (mg-min/L)AO3 initial (mg/L)Ozone Decay Rate (1(T3 sec'1)Dilution (%)AMA20020137347250.0190.7571.570.388SPW14511110165170.0331481.210.488Water SourceCCD394.3304.77200.0321.5140.951.155ANN655.242136280.0211.1311.180.7210OTT1715.88.94620.0221.1251.29* Initial Bromide concentration adjusted for dilution in calculations (i.e.unaccounted Br~ = (200*( 100-8)7100) - 137 - 20*(79.9/127.9) = 34 ng/L)4.2.2.1 Bromate Formation Potentials and Ozone ExposuresThe ozone kinetic data obtained from the 10°C experiments were expected to reflect decreasedozone decay rates. Significant decreases in the ozone decay rate were detected at this lowertemperature. For example, the decay rate was observed to decrease from 2.91xlO'3 sec' 1 at 20°Cto 7.2x10 sec' at 10°C for the ANN sample. Consequently, the OE values for a given ozonedose at 10°C were observed to be three to six-times higher when compared to true-batch resultsat 20°C. The highest observed OE was 57 mg-min/L for the AMA sample; the lowest was 14mg-min/L for CCD water.1.181066

Bromate formation potentials showed marked decreases as much as 54 percent for SPW (23|^g/L to 12 fJ.g/L) to 29 percent for OTT (1.4 ug/L to 1.0 ug/L). An average bromate reduction of46 percent was observed.The bromate and OE relationship was derived as presented in the previous Section 4.1. Thecalculation of the slope coefficient, K, was determined by fitting a linear function passingthrough the origin to the data point. A comparison of K values for the 10°C and 20°Cexperiments is presented in Table 4.7. The maximum K values for both temperatures wasobserved for AM A, while the minimum values were observed for OTT.Table 4.7: Effect of Temperature on True-Batch Formation of BromateTemp 10°C20°CWaterSourceAMASPWCCDANNOTTBrO3"(Ug/L)20114.35.21.0True-Batch ExperimentOE(mgmin/L)57 0.3548 0.2214 0.3031 0.1725 0.04Slope, K*(mg/mg-min)PredictedBromatefor 2-Loghiact3.9-6.02.4 - 3.83.3. -5.11.8-2.80.4 - 0.7BrO3 "(Ug/L)True-Batch ExperimentOE(mgmin/L)18 1.9012 1.925.0 1.7011 1.004.5 0.3135238.511.31.4Slope, K*(mg/mg-min)PredictedBromatefor 2-LogInact4.4 - 9.94.4-103.9-8.82.3 - 5.20.7-1.64.2.2.2 Bromate Formation Potential and Cryptosporidium InactivationThe respective linear relationships representing bromate formation as a function of OE arepresented in Figure 4.10. The suggested ranges for 2-log Cryptosporidium inactivation at 10°Cand 20°C by Oppenheimer et al. (2000) and Rennecker et al. (1999), have been included asreferences to assess the impact of increased CT requirements at lower temperatures. At 20°C,this figure shows bromate formation in SPW, AMA, and CCD close to or at the 10 ug/L MCLfor the higher CT requirements suggested by Rennecker et al. (1999). Even though the requiredCT increased dramatically to achieve the same level of inactivation once the temperature wasdecreased to 10°C, the level of bromate formation decreased just as dramatically. Using the highend of the suggested inactivation range presented in Figure 4.10, bromate formation in AMA haddecreased by 41 percent to 5.9 ug/L for the same level of inactivation. The other four watersalso underwent this dramatic reductions in bromate formation from 42 percent for CCD to 62percent for SPW.4.2.3 DiscussionIncreasing CT requirements will undoubtedly increase the potential for bromate formation.However, the impacts of temperature on bromate formation were characterized by a lower Kvalue, indicating less bromate formation per unit OE. The observations made in this analysisindicated that low bromide waters may exhibit trends that result in less bromate formation upon a67

decrease in temperature. As seasonal variations are taken into account, less bromate would beexpected to form during the winter than in the summer, based on this analysis. Ultimately, thebalance for inactivation must take into account that the strategy employed during winterconditions may result in exceeding the MCL if used during summer conditions. Thus, seasonalstrategies would be a prudent measure for facilities to maintain compliance with both pathogeninactivation and bromate formation requirements./•^K15SPW (20°C¥ AMA (20°C)y=1.92>/ y = 1.90xI.233aoPL,oa'•a12ANN (20°QCCD(20°C) 0= 1.70xAMA (10°C)y = 0.35xI2cc0 10 15 20OE (mg-min/L)25 30Figure 4.10: Ozone Exposure versus Bromate Formation Potential for 2-LogCryptosporidium Inactivation at 10 and 20°C4.3 SUMMARYThe influence of natural organic matter on the formation of bromate was illustrated through apair-wise linear regression analysis. The analysis related bromate formation potential to variousNOM characterization methods. The bromate formation potential was determined using a truebatchozone reactor operated under a standard set of testing conditions: 20°C; pH 7; 1 mg ozoneper mg DOC. The characterization of NOM was developed through measurements of DOC, UVabsorbance and SUVA. The NOM was also operationally fractionated into hydrophobic,transphilic and hydrophilic fractions using macroporous, nonionic resins. The apparentmolecular weight distribution of these organics was obtained through size exclusionchromatography.68

Through these analyses, the fourteen project waters evaluated ranged in DOC from 1.4 to 7.3mg/L. On average 50 percent of the DOC was classified as hydrophobic. The remainder was onaverage 29 percent hydrophobic and 21 percent hydrophilic. The SUVA values calculated forthese waters ranged from 1.4 to 3.8 L/mg-m.The effects of NOM on bromate formation were confounded by NOM effects on the ozonedemand, rate of ozone decay and concomitant disinfection (CT or OE). NOM properties such asSUVA appeared to have a negative correlation with both bromate formation and ozone exposure.Consequently, the obvious conclusion was that NOM removal before ozone application would bebeneficial, thereby, indicating advantages of intermediate-ozonation over pre-ozonation. Theresults presented in Section 4.1.4, however, indicated that different NOM fractions might haveeither inhibitory or promotional effects on bromate formation. As optimized conventionaltreatment preferentially removes hydrophobic (inhibitory effect) and some transphilic(promotional effect) compounds, the observed benefits of intermediate-ozonation bromateformation may be a result of a change in the ozone demand and rate of ozone decay.The results from the true-batch reactor experiments, performed at 20°C and 10°C, indicatedabout an 80 percent reduction in bromate formation potential at the lower temperature. Due tothe sensitivity of Cryptosporidium inactivation to temperature, about three times as much ozonecontact would be required at 10°C as would be required at 20°C. Even with the increasedamount of ozone contact, approximately 40 percent less bromate was formed at 10°C for thesame level of Cryptosporidium inactivation. This result was surprising as it is commonlybelieved that more bromate would be formed at a lower temperature for a given level ofCryptosporidium inactivation.69

CHAPTER 5. EFFECT OF WATER QUALITY AND MINIMIZATION APPROACHESON BROMATE FORMATIONThis chapter focuses on bromate formation and minimization strategies investigated using benchscaleand pilot-scale flow-through ozone contactors. Expanding on the results obtained usingbench-scale batch reactors, these hydraulically different flow-through ozone contactors wereused to evaluate the effects of increasing levels of Cryptosporidium inactivation, temperature,ammonia addition, pH depression, and hydroxyl radical scavenger addition on bromateformation. The tradeoffs between bromate minimization and the formation of brominatedorganic compounds were also explored.5.1 BROMATE FORMATION5.1.1 Effect of Cryptosporidium InactivationOzone exposure values for a range of Cryptosporidium inactivation were developed specific tothe unique hydraulic characteristics of the laboratory-scale continuous-flow reactor, and arediscussed further in Chapter 8. Actual Cryptosporidium parvum experiments were performed toverify the relationship between ozone exposure and Cryptosporidium inactivation for thecontinuous-flow reactor. The results of these inactivation experiments are presented later inSection 8.2.For each of.the project waters, additional testing was performed to evaluate the effect ofincreasing levels of Cryptosporidium inactivation on bromate formation. The targeted ozoneexposure values used for the waters presented in Figure 5.1 corresponded to 1-, 2- and 3-logCryptosporidium inactivation at 15°C in the laboratory-scale continuous-flow reactor used forthe project. These data demonstrate that at pH 7 and 15°C, the majority of the low bromidewaters formed less than 7 ug/L bromate at 1-log Cryptosporidium inactivation. The two watersin which problematic levels of bromate formation was observed at this level of disinfection wereCCD and WPB, at 28 and 12 ug/L of bromate, respectively. It was anticipated that WPB mightform higher concentrations of bromate as it contained 170 ug/L bromide. Based on basic waterquality parameters and NOM fractionation, it was unclear why CCD formed significantly higherconcentrations of bromate as compared to other waters with similar water qualities.As the ozone exposure in these waters was increased to achieve 2- and then 3-logs ofCryptosporidium inactivation, an increase in bromate formation was observed each time.Increasing the inactivation of Cryptosporidium from 1- to 3- logs resulted in a 2.3 to 16-foldincrease in bromate formation. The lowest percent increase, from 0.7 to 1.6 ug/L, was observedin DAL water, and the largest percent increase, from 0.6 to 9.8 ug/L, was observed with HOUwater.For SPW, CRW and SAC waters presented in Figure 5.2, a range of Cryptosporidiuminactivation between 0.5-log and 1.5-log was evaluated. The measured bromate formation for 1-log Cryptosporidium inactivation in each of these three waters at the higher pH of 8, was higher70

than the 10 ug/L Stage 1 D/DBP Rule MCL. The concentrations of bromate formed rangedbetween 24 ug/L for SAC water (initially spiked to 47 jig/L bromide) and 38 ug/L for SPWwater. While reducing the ozone exposure reduced bromate formation to in each of the waters,SPW still formed 12 ng/L bromate at 0.5-log Cryptosporidium inactivation. Understandably, theinitial 145 fig/L bromide concentration in SPW contributed to this elevated level of bromate.CRW water and the bromide spiked SAC water (47 ug/L bromide) formed less than the 10 |ig/LMCL, at 3.2 and 9.5 ug/L bromate, respectively.Log Cryptosporidium InactivationFigure 5.1: Impact of Ozone Exposure, Expressed as Log-Cryptosporidium Inactivation,on Bromate Formation in the Laboratory-Scale Continuous-Flow Ozone Contactor (pH 7,15°C)Figure 5.3 shows percent conversion of bromide to bromate in the laboratory-scale continuousflowozone contactor for selected waters. By normalizing bromate formation by the initialbromide concentrations, differences in the propensity of the different waters to form bromate canbe easily identified. Most notably at pH 7 and 15°C, only between 2 and 5 percent of thebromide in the DAL water was converted to bromate at 1- and 3-log Cryptosporidiuminactivation, respectively. It is likely that the 0.53 mg/L ambient ammonia-nitrogenconcentration was sufficient to minimize bromate formation under these conditions. Thepotential benefits of ammonia addition are discussed later in Section 5.2.2. At the other extreme,approximately 100 percent of the bromide was converted to bromate in the CCD water sample at3-logs Cryptosporidium inactivation. It is possible that even at pH 7, initial concentrations ofammonia-nitrogen (0.06 mg/L) and DOC (1.8 mg/L) were not high enough to provide sinks forbromide. Consequently, all of the bromide was available for conversion to bromate, and did soonce a sufficient amount of ozone contact had been provided. For the rest of the waters, thepercent bromide conversion to bromate ranged between 2 and 21 percent and between 20 and 60percent at 1-log and 3-logs of Cryptosporidium inactivation, respectively.71

0.5 1.0Log Cryptosporidium Inactivation1.5Figure 5.2: Impact of Ozone Exposure, Expressed as Log-Cryptosporidium Inactivation,on Bromate Formation in the Laboratory-Scale Continuous-Flow Ozone Contactor (pH 8,15°C)-•-CCD-0-WPB-A- LAW-&-NJA-•-ANN-•-OTT-0-DALLog Cryptosporidium InactivationFigure 5.3: Impact of Ozone Exposure, Expressed as Log-Cryptosporidium Inactivation,on the Percent Conversion of Bromide to Bromate (pH 7,15°C)72

5.1.2 Temperature EffectsAs previously stated, both the rate of ozone decay and the sensitivity of Cryptosporidium toozone are dependent on the temperature of the system. The true-batch ozone decay experimentsperformed at 20°C and 10°C had indicated significant decreases in the ozone decay rate asdecreases in the temperature were made. These experiments also predicted lower levels ofbromate formation at the lower temperature for the same predicted level of Cryptosporidiuminactivation. However, the opposite trend in bromate formation was observed using thelaboratory-scale continuous-flow reactor. For a given level of Cryptosporidium inactivation,decreasing temperatures generally resulted in increasing amounts of bromate formation, asshown in Figure 5.4 and Figure 5.5.-•-WPB-0-CCD-if- LAW-•-NJA-&- ANN-CHHOU10 15 2025 30Temperature (°C)Figure 5.4: Effect of Temperature on Bromate Formation (2-Log CryptosporidiumInactivation, pH 7)Since the inactivation kinetics of Cryptosporidium parvum are temperature dependent, differentamounts of ozone exposure were required to achieve the same level of inactivation at differenttemperatures. The specific levels of ozone exposure for each temperature are discussed inSection 8.2. At pH 7 and a predicted 2-logs of Cryptosporidium at each temperature evaluated,increasing the temperature from 5°C to 25°C resulted in a 28 to 85 percent reduction in bromateformation for most of the waters, as shown in Figure 5.4. The corresponding HOU analysesindicated the opposite trend with a 113 percent increase in bromate formation for the sameincrease in reaction temperature. Compared to the other waters, HOU had a high DOC (9.4mg/L), a correspondingly rapid ozone decay curve (Figure 4.6) and the lowest alkalinity (28mg/L). However, only NJA was impacted by the temperature with respect to compliance withthe 10 ng/L MCL. For the rest of the waters, those that formed bromate in excess of the MCL73

emained above the MCL at all temperatures evaluated, and for those waters that did not have aproblem with bromate formation remained that way, for this level of inactivation.15012090ofa3OSOpq603000 10 15 20Temperature (°Q25 30Figure 5.5: Effect of Temperature on Bromate Formation (1-Log CryptosporidiumInactivation, pH 8)At pH 8 and sufficient ozone exposure to inactivate a predicted 1-log of Cryptosporidium at eachtemperature evaluated, similar trends were observed. The percent reduction in bromateformation between 5°C and 25°C ranged between 17 and 83 percent for the three waters shownin Figure 5.5. Even at 25°C, all of these waters were in excess of the 10 ug/L MCL.The opposing trends observed between the true-batch reactor and the laboratory-scalecontinuous-flow ozone contactor illustrated the complexity of comparing effects on bromateformation between hydraulically different systems. The trends in temperature effects on bromateformation appear to have been significantly influenced by the hydraulic characteristics of thesystem controlling the ozone exposure requirements. Increased ozone exposure will undoubtedlyincrease the potential for bromate formation, but as seasonal variations are taken into account itbecomes unclear from this analysis if more or less bromate would be expected during the winteras compared to the summer. The results from the full-scale ozone facility survey presented inChapter 3 were also unclear. While a slightly lower average bromate level was observed duringthe winter, differences in water quality and levels of inactivation were recorded.As temperature control cannot economically be used as a bromate formation control strategy andseasonal differences in water quality generally exist for those waters that experience significanttemperature variation, utilities might be best suited to develop site-specific seasonal bromateformation information using representative water qualities. The data presented here illustrate,74

however, that this testing should be performed in a system hydraulically similar to the utility'santicipated or existing ozonation system.5.2 BROMATE MINIMIZATION5.2.1 pH DepressionIt has been reported that the depression of pH to below 7 prior to ozonation will result in thereduction in bromate formation as compared to bromate formation in water above pH 7 (e.g.,Song, 1996). This reduction has been attributed to two factors: at pH less than 7, oxidizedbromide will primarily be found as hypobromous acid (HOBr), limiting the amount ofhypobromite (OBr~) available for reaction with ozone (HOBr 4* OBr" + H+; pKa = 8.7); at thesedepressed pHs, the generation of hydroxyl radicals is reduced, resulting in more stable ozoneresiduals, limiting the amount of bromate formed through the hydroxyl radical related bromateformation pathways. The increased ozone stability at the depressed pH has the added benefit ofrequiring a lower initial ozone dose to achieve the same level of disinfection as compared to theozone dose required at ambient pH. At lower pH, the ratio of hydroxyl radical, the main oxidantfor bromate formation in natural water to ozone tends to be lower than at higher pH (Eloviz etal., 1999b).Each of the waters was again evaluated using the laboratory-scale continuous-flow ozonecontactor. As anticipated, reductions in bromate formation were observed as the pH wasdepressed from 8 to 7 to 6, as shown in Figure 5.6 and Figure 5.7. The reduction of bromate perunit decrease of pH, generally ranged between 30 to 50 percent. The decrease in bromateformation generally followed a linear trend for the range of pH values evaluated. It is importantto note that while significant reductions in bromate formation were realized through pHdepression, the concentrations of bromate formed at pH 6 for 2-logs of Cryptosporidiuminactivation in several of the project waters still exceeded the 10 ug/L MCL. In CCD, WPB andLAW waters 17, 16 and 11 ug/L bromate was formed. The other waters presented in Figure 5.6,formed less than 5 ug/L under these conditions. At pH 6 and 1-log Cryptosporidiuminactivation, less than 6 ug/L bromate formed in SPW, CRW and SAC waters. This indicatedthat pH reduction appears to be a successful approach to mitigate bromate formation for manywaters. However, in a few waters, it may be necessary to implement additional or alternativebromate formation reduction strategies to ensure the MCL is not exceeded at the higher levels ofCT required for Cryptosporidium inactivation.While lowering the pH helps to mitigate the problematic formation of bromate, this bromateminimization strategy appears to enhance the formation of various brominated organiccompounds. The concentration of TOBr in the ozonated samples was measured to determine thesignificance of pH depression on TOBr formation. The concentration of TOBr formed duringthe experiments tended to be quite low. The typical range of TOBr formation was from belowthe 4 ug/L as Br" detection limit to 20 ug/L as Br", as shown in Figure 5.8. WPB water hadhigher TOBr values in the range of 25 to 35 ug/L as Br", which was likely due to the high DOC(10.4 mg/L) and bromide (170 ug/L) concentrations. For utilities looking at pH depression tocontrol bromate, TOBr may become problematic if it becomes a regulated class of compounds.75

I•o12090-WPB -0-CCD-LAW -0-ANN-NJA -&-HOU-OTTu.aCS60O03678PHFigure 5.6: Effect of pH on Bromate Formation (2-Log Cryptosporidium Inactivation,15°C)-•-ACD-D-SPWSAC-A-CRW678pHFigure 5.7: Effect of pH on Bromate Formadon (1-Log Cryptosporidium Inactivation,15°C)76

DC-•-CCD3•o

elevated further to 1.0 mg/L as N, though it was not as significant as the net change observedwith the spike to 0.5 mg/L ammonia-nitrogen.WPB-A- LAW-A-NJA-•-ANN-D-HOU-0-DAL00.5Ammonia Concentration (mg/L-N)Figure 5.9: Effect of Ammonia Addition on Bromate Formation (2-Log CryptosporidiumInactivation, 15°C, pH 7)&3•oI ota2cc0 0.5Ammonia Concentration (mg/L-N)Figure 5.10: Effect of Ammonia Addition on Bromate Formation (1-Log CryptosporidiumInactivation, 15°C, pH 8)78

At 2-logs of Cryptosporidium inactivation and pH 7, ammonia addition to 0.5 mg/L as N lead toa reduction in bromate formation of approximately 50 percent in LAW, NJA and ANN waters.This level of reduction was sufficient for these waters to reduce bromate formation to below the10 ng/L MCL. For CCD water, the 30 percent reduction in bromate formation that correspondedto the 0.5 mg/L ammonia-nitrogen, was not sufficient to reduce the bromate concentration tobelow 10 ug/L. Ammonia addition did not appear to significantly impact those waters withbromate formation already below 10 ug/L.At 1-log Cryptosporidium inactivation and pH 8, the elevated 0.5 mg/L ammonia-nitrogenconcentration resulted in an 88 and 69 percent reduction in bromate formation for CRW andbromide spiked SAC (47 ug/L Br") waters, respectively. This was sufficient to reduce the finalbromate concentration to below 10 ug/L. In SPW a 58 percent reduction in bromate formationwas observed at the 0.5 mg/L ammonia-nitrogen concentration. While increasing the ammonianitrogenconcentration to 1.0 mg/L resulted in a total reduction in bromate formation of 70percent, about 12 ug/L bromate was formed.As the addition of ammonia can provide a temporary bromide sink to reduce bromate formation,additional analyses were performed to determine if this effect would extend to the formation ofbrominated organic compounds. Unfortunately, only four samples yielded TOBr concentrationsat or above the minimum reporting level. Consequently, it was not possible to determine ifammonia addition had an effect on TOBr formation.5.2.2.1 Pilot-Scale Plant InvestigationAmmonia was used at the Britannia pilot plant (Ottawa, Canada) to reduce bromate formationduring ozonation. The pilot-scale ozone contactor consisted of three glass columns in series, asdescribed in Section 2.2.5. The water used for these experiments was adjusted to promotebromate formation by raising the pH from 6.1 to 8.5, and spiking bromide to 0.1 mg/L, asdescribed in Section 2.2.5. It was necessary to take this step since no bromate formation wasobserved under ambient conditions (pH 6.1, 0.03 mg/L Br", 0.5°C, 30 mg-min/L CT).Three separate trials were conducted to evaluate ammonia addition as a bromate minimizationstrategy at pilot-scale. The initial trial served as the control without ammonia addition (ambientammonia < 0.05 mg/L). Ammonia (0.05 and 0.1 mg/L as N) was added to the second and thirdtrials. The data shown in Figure 5.11 suggest that adding as little as 0.05 mg/L of ammoniaresulted in about a 50 percent reduction in bromate concentrations in the water leaving the ozonecontactor. Doubling the amount of ammonia applied resulted in a smaller marginalimprovement, reducing bromate by an additional 20 percent. It is likely that the addition of morethan 0.1 mg/L of ammonia would continue the reduction in bromate formation, but only by asmall amount.5.2.2.2 ConclusionThe important conclusion from these ammonia addition experiments was that the application of arelatively small amount of ammonia could result in significant reductions in bromate formation.The magnitude of this benefit, however, was not consistent for all of the waters tested. Since79

many water treatment plants already use ammonia for chloramination, ammonia may be a readilyavailable method for reducing bromate formation without sacrificing CT targets. The presenceof ammonia can interfere with the bromate formation pathway by temporarily scavenginghypobromous acid and forming bromamine species. These species are subsequently oxidized byozone, freeing the bromide so that it could again be oxidized to hypobromite ion/hypobromousacid. This mechanism can limit the availability of hypobromite ion/hypobromous acid until allof the ammonia is consumed. As an additional benefit, the limited availability of hypobromiteion/hypobromous acid due to ammonia addition, also appears to reduce TOBr formation.5040.1 30•^«I 20Ammonia Concentration-*- O.05 mg/L as N-a- 0.05 mg/L as N-•—0.1 mg/L as N10Column 1 Column 2 ColumnsFigure 5.11: Effect of Ammonia on Bromate Formation (Ottawa Pilot Plant, 0.5°C, pH 8.5,0.1 mg/L BO5.2.3 Cumulative Effects of Ammonia Addition and pH DepressionAs the stability of the bromamines is relative to the particular species formed, which primarilydepends on the pH, ammonia concentration, and bromide concentration, additional tests wereperformed to evaluate the effects of both pH adjustment and ammonia addition. A full factorialset of experiments for pHs 6, 7, and 8, and ammonia concentrations of ambient, 0.5, and 1.0mg/L as N were conducted on CCD and SPW waters. The results of these experiments arepresented in Figure 5.12 and Figure 5.13. Significant reductions in bromate formation wereobserved in both waters for the strategies employing both pH depression and ammonia addition.A cumulative effect was observed as pH depression and ammonia addition reduced bromateformation more than either alone. For example, in SPW water at pH 8 without ammoniaaddition, 38 ng/L bromate was formed. When the pH was depressed to 6 or 1.0 mg/L ammonia80

was added separately, 5 and 12 ng/L bromate was formed, respectively. If the pH was depressedto 6 and 1.0 mg/L ammonia was added less than 1 jig/L bromate was formed.1ota.8832MpHOmg/L-N0.5 mg'L-N6 l.Omg^-N AmmoniaAdditionFigure 5.12: Effect of pH Depression and Ammonia Addition on Bromate Formation inCCD (1-Log Cryptosporidium Inactivation, 15°C)aoto asOfacs£10Omg/L-N1. Omg/L-NAmmoniaAdditionFigure 5.13: Effect of pH Depression and Ammonia Addition on Bromate Formation inSPW (1-Log Cryptosporidium Inactivation, 15°C)81

5.2.4 Hydroxyl Radical Scavenger AdditionThe addition of acid or ammonia has focused on bromate formation pathways requiringhypobromite. Even with these bromate minimizing strategies in place, bromate formation cancontinue to proceed through hydroxyl radical initiated pathways. It is likely that the addition of ahydroxyl radical scavenger, such as tertiary butanol, could limit bromate formation reactions thatrequire hydroxyl radicals. A subset of waters was tested with tertiary butanol additions of 1 and3 mM, as shown in Figure 5.14. Bromate formation was, for practical purposes, completelyinhibited in the presence of 1 mM tertiary butanol. Obviously, higher concentrations of tertiarybutanol did not provide any additional benefit. These initial experiments indicate there ispotential for the minimization of bromate formation through the addition of a hydroxyl radicalscavenger. Additional experiments should be performed to determine the minimum amount ofscavenger addition needed to effectively inhibit bromate formation and identify hydroxyl radicalscavengers suited for use in drinking water treatment plants. As the mechanism ofCryptosporidium inactivation is still being investigated, it is not clear if the scavenging ofhydroxyl radicals would adversely impact its inactivation kinetics.3 40ofe£cs30-•-WPB (pH7)-D-SPW (pH8)-A-CRW(pH8)-A-NJA (pH7)-O-DAL (pH7)o201000.1 2 3t-BuOH (mM)Figure 5.14: Effect of a Radical Scavenger (Tertiary Butanol) Addition on BromateFormation in the Laboratory-Scale Continuous-Flow Ozone Contactor (15°C)5.3 SUMMARYAs expected the higher levels of CT required for Cryptosporidium inactivation resulted in higherlevels of bromate formation. Based on the results presented in this chapter, however, bromate82

formation should not be a problem for many utilities utilizing low bromide (

formation observed in these laboratory-scale continuous-flow ozone contactors indicated thatammonia addition by itself might only be sufficient for those utilities within 10 to 20 jig/L of the10 jug/L MCL. However, it was also shown that together, the cumulative bromate reductioneffects of ammonia addition and pH depression could be used to control bromate formation inproblematic waters.It is important to note that these bromate minimization strategies also appeared to affect theformation of brominated organic compounds. While pH depression clearly enhanced TOBrformation, ammonia addition appeared to reduce TOBr formation. Should TOBr become aregulated group of compounds in the future, utilities ozonating under low pH conditions by mayhave to consider alternative bromate minimization strategies.84

CHAPTER 6. HYDRODYNAMIC IMPACTS ON BROMATE FORMATIONTo determine if hydrodynamic conditions (staged/tapered versus single-stage; counter-currentversus co-current) would significantly impact bromate formation, a series of true-batch and pilotscaleexperiments were performed. Staged ozonation was evaluated with both of the scales ofreactors, while the flow configuration was only evaluated at pilot-scale. It was hypothesized thatif a good correlation could be developed between ozone contact (CT or OE) and bromateformation, regardless of the hydrodynamic configuration, then the tests would indicate thechemical conditions were more important than the hydrodynamic conditions for bromateformation. If significant differences were observed between the different hydrodynamicconditions then it would be expected that the hydrodynamics of the ozone contactor could beused as a bromate formation minimization strategy.Krasner et al. (1993) studied the effect of staging ozone application within a contactor, i.e. ozonedosed in more than one cell, to minimize ozone residual and, thus, potentially reduce bromateformation; no appreciable difference in bromate formation was observed with staged ozonation.Targeting specific ozone residual concentrations, an ozone contactor was dosed in three separateexperiments: (1) single stage ozonation with a dose of 1.4 mg/L, (2) staged ozonation with 1.0mg/L added in the first stage and 0.4 mg/L added in the second stage, and, (3) staged ozonationwith 1.4 mg/L added in the first stage and 0.5 mg/L added in the second stage to meet CTrequirements for direct filtration. Analyses revealed bromate formations of 5 ug/L,

6.1 TRUE-BATCH STAGED OZONATIONStaged ozone tests were performed in a true-batch reactor on selected waters: NJA, DAL, SPW,ANN, and OTT. Samples were prepared for the single-stage true-batch experiments by initiallybuffering with 1 mM phosphate solution and adjusting to a pH of 7.0. A total ozone dose of 1:1mg 63 to mg DOC was applied to the water in two stages, with half of the total ozone applied toeach stage. The ozone residuals were allowed to decay below the minimum detection limit aftereach stage of ozone addition, at which point, aliquots of the ozonated samples were collected forbromate analysis. Kinetic data were used to calculate the ozone exposure for each stage.Additional discussion of the staged ozonation method is outlined in Section 2.2.1.2.The concentration of bromate formed in each of the staged ozonation experiments is presented inTable 6.1. The reported bromate concentrations were based on the cumulative bromateformation during each stage of ozonation. For example, the stage two results included thebromate formed in the first stage plus the additional bromate formed during the second stage.The residual bromide concentrations were measured after each stage. Cumulative bromateformation (stage 1 + stage 2) was observed to range from 0.7 ug/L for OTT water to 28 ug/L forSPW water. As little as 0.1 ug/L, or 14 percent of the final bromate concentration, was formedduring the second stage (OTT). The maximum second stage formation occurred in SPW water,where the bromate formed was calculated to be 15 ug/L, accounting for 53 percent of the totalamount of bromate formation.The effect of staged ozonation on bromide concentrations must be taken into account whenconsidering the second stage bromate formation. As the first stage was completed, the bromideconcentration was effectively reduced because of oxidation to bromate and reactions with NOMto form TOBr. Thus, when the second ozone dose was applied, there was less bromide availablefor reaction. It is possible that the dilution of the water by the addition of the ozone stocksolution may have also affected the subsequent formation of bromate.Ozone exposure values for each stage were calculated separately and summed to provide acumulative OE value for the second stage. The maximum observed cumulative OE was 10 mgmin/Lfor SPW; the minimum was 4.9 mg-min/L for NJA. The second stage OE values weregreater than the first stage values for all the waters. The reduction of the ozone demand duringthe first stage (i.e. oxidation of highly reactive hydrophobic compounds) was expected toincrease OE for the second stage. The second stage values of OE accounted for more than 55percent of the total OE for all of the waters. For each of the waters, the conversion of bromide tobromate (calculated as a function of initial bromide concentration adjusted for dilution) wasnearly equivalent for each stage. For example, ANN showed a conversion of bromide tobromate 4.1 percent and 8.0 percent, respectively.86

ooTable 6.1: Bromate Formation Comparison Between Bench-Scale True-Batch Staged and Single-Stage Ozonation (20°C)WaterNJADALSPWANNOTTStage Cumulative Initial* Residual CumulativeOE Bromide Bromide Bromate(mg-min/L) (ug/L) (ug/L) QigfL)12Single12Single12Single12Single12Single1.04.93.54.19.56.92.810123.89.0111.95.24.521 14131521 17149.7145 1331106465 58535817 12116.31.02.01.50.61.02.41328234.17.6110.60.71.4UnaccountedBromide(Hg/L)4.63.75.11.52.89.80.00.066.61.81.50.03.43.79.8Modeled TOBrt(jig/L as Br")0.040.030.100.030.020.101.21.01.90.250.220.700.020.020.10Total Br to BrO3"Conversion*(%)* undiluted** "0.0" value indicates that the calculated bromide recovery is greater than the estimated unozonated water bromide concentration* TOBr estimated using Song (1996) TOBr Model where: [TOBr]=1.004(Br)' 765(DOCy0551(pHy3916(NH3-N)° ^(Os) 1135(TIC)'0153* estimate of all bromide species other than bromide; adjusted for dilution by ozone stock solution addition3.26.95.12.03.68.36.014114.18.0122.32.96.0Total Bromide DilutionIncorporation*(%) (%)272719102046114517113242759714121017147121049851110

Table 6.2 lists the bromate formation and staged ozone exposure relationships developed foreach of the water samples. The relationship for each individual stage was first calculated andidentified as Kstage with KI representing stage one values and Ka representing stage two values.The KI values were calculated by assuming a linear relationship between the origin (zerobromate formation at zero OE) and the first stage bromate concentration and OE measurement.The Ka value was calculated as the slope of the linear relationship between the first and thesecond stage bromate concentrations and the first and second stage measured values of OE. TheKa value was consistently less than the KI value, indicating that less bromate formed per unit OEduring the second stage. It should be noted that the available bromide concentrations of thesecond stage were lower due to bromate and TOBr formation and the addition of ozone stocksolution during the first stage. Consequently, the slope coefficients for the second stage werereflective of the decreased bromide availability.Table 6.2: Bromate Formation Potential For Bench-Scale Batch Staged OzonationWater Stage Bromate Cumulative OE Kstage* Overall K** K^*(mg-min/L)NJADALSPWANNOTT12121212121.02.00.61.013284.17.60.60.71.04.94.19.52.810.13.89.01.95.21.000.260.150.074.642.051.080.670.320.030.43—0.11—2.91—0.88—0.16—0.43—0.35—1.92—0.97—0.22~* Slope value, K (ug/mg-min), is based on diluted sample bench-scale experiments. KI value calculatedas slope of origin and Stage 1 OE and BrO 3". K2 value calculated as slope between the Stage 1 and Stage2 data. KSmgie value calculated as slope between the origin and the non-staged single ozone dose OE andBrO3" value.** Overall K value is the slope of the best fit line between the origin and the Stage 2 OE and BrO3" value.Figure 6.1 graphically presents the cumulative bromate formation results of the staged ozonationexperiments compared to the single dose true-batch experiments initially presented in Section4.1.3.2. The comparison indicated inconclusive results with respect to the reduction of bromateformation by staged ozonation. An increase in the level of bromate formed was observed forSPW water and no effect was observed in NJA water. For the rest of the waters, the low levelsof bromate formed during either staged or single-stage application of ozone limited any furthercomparison.88

•SPW Staged• ANN Staged• NJA Staged•DAL Staged• OTT StagedSPW Single StageANN Single Stage-0- - NJA Single Stage-Q- - DAL Single StageX OTT Single Stage0 12OE (mg-min/L)Figure 6.1: Impact of Staged Ozonation on Bench-Scale Batch Bromate Formation6.2 PILOT-SCALE STAGED OZONATIONPilot-scale experiments conducted at the Britannia Water Purification Plant (Ottawa, Canada)were used to explore contactor configuration options for minimizing bromate. As a result of thepilot work being performed during the winter, all of the pilot-scale tests were performed at awater temperature of 0.5°C. Preliminary experiments with the ambient water (pH 6.1, 17 (ig/Lbromide) revealed that at this temperature and pH, no measurable bromate formed even at veryhigh CT levels. To obtain measurable bromate formation, the pH of the water was raised to 8.5by NaOH addition, and the bromide concentration was raised to 100 |ig/L using KBr. While it isacknowledged that the intent of this research was to investigate bromate formation in lowbromide waters, it was decided that the objective of determining the impacts of contactorconfigurations took precedence for these tests. Furthermore, the need to artificially raise the pHand bromide levels to obtain measurable bromate formation at high CT values in very cold waterwas an important consideration in itself. It suggests that bromate formation at low pH (6.1),bromide (17 [ig/L) and temperature (0.5°C), would not be a problem for Ottawa River watereven when ozonating to CT values as high as 50 mg-min/L.To evaluate staged ozonation, ozone was applied to the first two columns by splitting a fixed gasflow from the ozone generator. By varying the split ratio of the ozone gas, different residualozone concentration profiles were developed through the ozone contactor, as shown in Figure6.2. Both contactors were operated with ozone applied in counter-current mode. The data showthat the residual ozone concentration exiting the first column was approximately proportional tothe fraction of the total ozone applied to the column. In the two subsequent columns, however, aconvergence of the residual ozone measured for each of the four ozone split ratios was observed.89

In particular, the ozone residuals at the effluent of the third column were similar for the fourscenarios, all in the range of 2.0 to 2.4 mg/L. This trend might be expected because the coldwater (0.5°C) and relatively low DOC (2.6 mg/L) ensured a slow rate of ozone decay. Underthese conditions, applying ozone in two stages in rapid succession instead of one stage wouldappear to result in approximately the same total downstream ozone concentration, as wasobserved in the third column effluent.4r 3«5S 'tt>6 24>c o§ 1ao>O 3 Split Ratio (%/%)75/25 Col 1&250/50 Col 1&225/75 Col 1&2W 0Column 1 Column 2 ColumnSFigure 6.2: Ozone Profile Through Britannia Pilot Ozone Contactor During StagedOzonation (pH 8.5,0.5°C)With little ozone decay evident, adding more ozone in the first contactor resulted in higher totalCT values due to greater contact time, as seen in Figure 6.3. Cryptosporidium inactivation usinga given amount of ozone would therefore be maximized in this system by applying 100 percentto the first column. (It should be noted that due to the cold water and the height of the column,ozone mass transfer was not limited in this system when applying all of the ozone to onecolumn.) As shown in Figure 6.4, while CJwas greatest when adding all of the ozone to the firstcolumn, bromate formation was also maximized when using this approach. In fact, bymodifying Figure 6.4 to plot bromate against the cumulative CT through each column of theozone contactor, a consistent correlation between bromate and CT was observed regardless of thesplit ratios used, except perhaps for the "100% ozone in column 1" scenario. However, even forthe "100%" scenario, the effluent of the ozone contactor yielded a CTand bromate concentrationconsistent with the other split ratios.Based on these pilot-scale results presented here and the bench-scale results presented in Section6.1, there is no strong evidence suggesting that splitting the ozone dose between multiple cells inan ozone contactor would enable bromate formation to be reduced while maintaining the sameCT. The data in Figure 6.5 indicate that with very little variation, there exists a unique bromateconcentration for a given CT value, regardless of the split ratio used.90

25.3EwoSsU2015100Column 1 Column 2 ColumnSO3 Split Ratio (%/%)-•-100% in Coll-o- 75/25 Col 1 & 2-•-50/50 Col 1&2-^25/75 Col 1&2Figure 6.3: Cumulative CT Through Britannia Pilot Ozone Contactor During StagedOzonation (pH 8.5,0.5°C)Q 3 Split Ratio (%/%)-•-100% in Coll-°-75/25 Col 1&2-•-50/50 Col 1&2-*- 25/75 Col 1&2Column 1 Column 2 ColumnSFigure 6.4: Bromate Formation Through Britannia Pilot Ozone Contactor During StagedOzonation (pH 8.5, 0.5°C)91

O 3 Spft Ratio (%/%)-*-100% in Coll-o-75/25 Col 1&2-•- 50/50 Col 1 & 2-^-25/75 Col 1&20 5 10 15CT (mg-min/L)20 25Figure 6.5: Bromate Formation as a Function of CT (pH 8.5,0.5°C)6.3 CO-CURRENT VERSUS COUNTER-CURRENT OZONATIONAdditional pilot-scale studies were conducted at the Britannia Water Purification Plant toexamine whether co-current or counter-current ozonation would yield lower bromateconcentrations for similar CT values. For these experiments ozone was only applied to thesecond column of the three-column pilot-scale ozone contactor.The same dose of ozone was applied for two runs, with the contactor operating in co-currentmode in one run, and counter-current in the other. Figure 6.6 shows the ozone concentrationprofile under each of these conditions. As would be expected, the ozone concentration was moreuniform in co-current application as compared to counter-current (Hull, 1995). It is important tonote that the ozone concentration leaving the column was fairly similar in both cases: in countercurrentmode, the ozonated water left the contactor at the bottom (height = 0 m) with an ozoneconcentration of 1.6 mg/L, while in co-current operation, the water left at the top of the contactorwith an ozone concentration of 1.9 mg/L.As shown in Figure 6.7, the formation of bromate along the depth of the contactor was also verysimilar for both modes of operation. At the entrance of the contactor (at the bottom for cocurrentmode, and the top for counter-current), the bromate concentration was about 4 to 6 ug/L.However, at the effluent of the column the bromate was approximately 14 to 15 ug/L forcounter-current and co-current modes, respectively. Since both the bromate and residual ozoneconcentrations entering the following column were similar for both modes of operation, it wasnot surprising that the final bromate concentrations at the effluent of the third column wereapproximately the same (22 and 24 ug/L for co-current and counter-current ozonation,respectively). Overall, there was no evidence that operating the contactor in a co-current orcounter-current mode would have any significant impact on bromate formation for the sameapplied ozone dose.92

Counter-CurrentCo-Current0123Ozone (mg/L)Figure 6.6: Ozone Profile Versus Contactor Depth for Counter- and Co-CurrentOperations ,s 3oii2. 2• Counter-Current• Co-Current00 4 8 12Bromate Formation (ug/L)16Figure 6.7: Bromate Profile Across Contactor Depth For Counter- and Co-CurrentOperationFigure 6.8 shows that the mode of ozonation did, however, affect the CT achieved within thecontactor. When operating in co-current mode, more than twice the CT was obtained than whenoperating in a counter-current fashion. This was a result of the different ozone concentrationprofiles for the two operational configurations, as well as the shorter contact time for counter-93

current flow. Based on tracer tests a tio of approximately 3 minutes was calculated for countercurrentflow, and 4.5 minutes was calculated for co-current flow. In this particular contactor, itwould therefore be expected that a greater level of disinfection would be obtained during cocurrentoperation for the same applied ozone dose. Similar results have been reported in otherstudies (Hull, 1995).10-^averageCeffluentis average fromfour depths in contactoraEtwoHU642-•average0Co-CurrentCounter-CurrentFigure 6.8: Calculated CTfor Co- and Counter-Current OzonationThe CT values for co-current and counter-current ozonation were shown in Figure 6.8 usingdifferent methods of defining the ozone concentration. CT was always calculated based on thetio of the reactor. The Surface Water Treatment Rule (SWTR) allows C to be considered as (i)the average ozone concentration from multiple readings taken within the contact chamber(Caverage), (ii) the effluent ozone concentration for the chamber (Ceffl Uent) for co-current flow only,or (iii) the effluent concentration divided by 2 (CefnUent/2) for a counter-current chamber. Asshown in Figure 6.8, a difference was observed when comparing the calculated CT valuesdepending on the calculation method used, especially for the counter-current mode, hi countercurrentmode, use of Caverage led to a calculated CT that was 65 percent higher than when usingthe more easily measured Cout/2- While such differences would be site-specific, this result servesto illustrate that consideration should be given to such details when evaluating the performanceof an ozone contactor, since the calculated CT may influence ozone dose requirements. Also,when designing a contactor it may be useful and cost-effective to include internal samplinglocations to permit the determination of Caverage, rather than relying exclusively on Ceffluent orCeffluent/2-While co-current operation provided a higher CT compared to counter-current operation, whenthe additional CT from the third column was added, the total CT for the system was essentiallythe same for both modes of operation (22 vs. 23 mg-min/L), as shown in Figure 6.9. This was aresult of the total CT value being largely controlled by the CTin the third column. Since the CT94

for the third column was about the same for co-current and counter-current flows, this tended tomask the differences in CT from the second column.5040Counter-CurrentCo-Current•2 30Oto0)*^OSOPQ2010Contactor ColumnEffluentsReaction ColumnEffluents010 1520 25CT (mg-min/L)Figure 6.9: Bromate Concentration as a Function of CT for Co- and Counter-CurrentOzonationhi summary, for the overall pilot-scale ozone contactor there was no evidence that operating ineither co-current or counter-current mode was preferable in terms of reducing bromate formationwithout sacrificing CT. In this study, approximately the same bromate concentration wasobserved (22 ug/L vs. 24 ug/L) for the same total CT value (22 mg-min/L vs. 23 mg-min/L),when operating in co-current or counter-current mode, respectively.6.4 SUMMARYBased on these bench-scale and pilot-scale tests, staged (tapered) ozonation does not appear toreduce the levels of bromate formed compare to single stage ozonation, for a fixed level ofdisinfection. It was initially hypothesized that pilot-scale experiments might provide evidencethat contactor configuration, either staged ozonation or co-/counter-current application, wouldsuggest a means to minimize bromate formation while maintaining the same CT. However, therewas no evidence to support this hypothesis. Throughout these experiments, a fixed relationshipbetween bromate formation and ozone contact (CT or OE) existed, regardless of whether theozone was applied in one or two stages, or in co- or counter-current flow. The consistentrelationship between bromate formation and ozone contact indicates that the chemical conditionsare more important to bromate formation than hydrodynamic conditions.95

CHAPTER 7. A COMPARISON OF BROMATE FORMATION WITHIN DIFFERENTSCALES OF OZONE CONTACTORSBromate formation was evaluated with several different scales of ozone contactors, to determineif the bench-scale reactors could be used to assess tradeoffs between bromate formation anddisinfection for the larger pilot-scale and full-scale systems. These tests were also used todetermine if the precise concentrations of bromate formed in the pilot-scale and full-scalesystems could be predicted at bench-scale. These tests utilized several different types of ozonereactors, including: completely-mixed true-batch bench-scale ozone reactor, semi-batch benchscaleozone reactor, bench-scale continuous-flow ozone contactor, multi-column counter-currentpilot-scale ozone contactors, and under-over counter-current multi-chamber full-scale ozonecontactors. The full-scale and pilot-scale experiments took place at the Los Angeles AqueductFiltration Plant (Sylmar, California), the Neuilly sur Mame Water Treatment Plant (Paris,France) and the Britannia Water Purification Plant (Ottawa, Canada).7.1 LOS ANGELES AQUEDUCT FILTRATION PLANTA multiple-scale comparison study of ozone contactors was conducted in conjunction with theLos Angeles Department of Water and Power (Los Angeles Aqueduct Filtration Plant) in earlyFebruary of 1999. The purpose of the study was to probe bromate formation at different levelsof ozonation at each of three contactor scales, and to determine the comparability. Two differentbench-scale contactors were compared with pilot-scale and full-scale ozone contactorperformance. The bromate formation relationships developed at full-scale and pilot-scale werebased on terms of disinfection credit, or CT. For the bench-scale testing, the level of ozonationwas reported in both terms of CT and ozone exposure. The different contactors were thencompared based on the amount of bromate formed for a given amount of ozone contact (CT orOE).The full-scale and pilot-scale tests were performed on the same day using water from the LosAngeles Aqueduct. During the testing period, a large batch of the untreated water was collectedfor use in all of the laboratory-scale tests. This approach was used to minimize water qualitydifferences between the ozonation tests performed at each scale. Additional testing on this batchof water was presented throughout this report as data collected on LAW water. A summary ofthe water quality is presented in Chapter 2.7.1.1 Testing PlanOn-site ozone testing and sampling was performed at LAAFP by plant staff. Four experimentswere run each at full-scale and pilot-scale. At each scale, the experimental testing conditionswere varied by adjusting the gaseous ozone flow to either 100, 75, 50, or 25 percent of the totalozone output. The inlet and outlet of each cell was monitored for dissolved ozone residual usingHACK AccuVac vials to instantaneously quench dissolved ozone and a laboratoryspectrophotometer to measure ozone residual. Contact times were estimated from tracer studyinformation coupled with the liquid flow rates and the volumes of the contactor cells. Tracer97

studies were used to determine tio (the time for 10 percent of a tracer mass to exit the contactor)and tso (assumed equal to HRT). Utilizing the ozone concentration, HRT and tio contact time,CT values were calculated for the overall contactors and for each cell.Samples for residual ozone concentration and bromate concentration were taken at six locationsin the full-scale contactor and eleven locations in the pilot-scale ozone contactor. The sample taplocations are shown on the full-scale and pilot-scale schematics, presented in Chapter 2.As a residual ozone concentration existed at many of the sampling points, all of the bromatesamples were collected in 40-mL vials containinglOO uL of a 5 percent (by volume) solution ofdiethylamine (C^nN - an "organic ammonia") to immediately quench any ozone residual. Byquenching the ozone residual, bromate formation through the ozone contactors could beevaluated. Without quenching the residual ozone concentration, bromate formation would beexpected to continue, resulting in bromate measurements not representative of the bromateprofile through the ozone contactor at the time of sampling. These vials were then shipped to theauthors for analysis.The batch of water collected for the laboratory-scale experiments was tested using thecompletely-mixed true-batch ozone reactor and the laboratory-scale continuous-flow ozonecontactor. The details of the experimental methodologies are presented in Chapter 2. In order tocover a range of ozone exposures, three experiments were performed with the true-batch reactorand five experiments were performed with the continuous-flow contactor. Bromateconcentrations were measured following each separate experiment. The CT and OE versusbromate relationships generated for each of these reactors were compared with the bromateformation relationships developed from the full-scale and pilot-scale testing. It should also benoted that the true-batch experiments were performed at a standard 20°C while the continuousflowexperimentation for this scale comparison was conducted at 9°C, the water temperature ofboth the full-scale and pilot-scale tests.7.1.2 True-Batch Ozone ReactorIndividual relationships for the four contactors/reactors were developed. These individualrelationships were initially explored, then overall conclusions were drawn based on thesimultaneous comparison of the three scales.A series of true-batch ozonation experiments were performed to determine bromate formation forselected ozone doses: 2:1, 1.5:1 and 1:1 mg ozone to mg DOC. For each experiment, the ozoneexposure was calculated to quantify the level of ozonation and the corresponding concentrationof bromate formed was measured. The relationship between bromate formation and ozoneexposure is shown in Figure 7.1. The 1:1, 1.5:1 and 2:1 mg ozone to mg DOC doses produced7.5, 16 and 19 ug/L bromate, respectively.For all of the ozone doses evaluated, unreacted bromide was present after ozonation. At the 2:1mg ozone to mg DOC dose, 5.6 ng/L bromide remained after the ozone residual had decayed tobelow detection. The presence of unreacted bromide indicates that additional bromate couldhave been formed if additional ozone contact was provided. However, Figure 7.2 suggests that98

there might be the beginning of a slowing or plateau in bromate formation as the ozone dose wasincreased to the 1.5:1 mg ozone to mg DOC dose.25| 20y=0.63xR2 = 0.90a•2 15«£ 102 50900 5 10 15 20 25 30 35 40Ozone Exposure (mg-min/L)Figure 7.1: Bromate Formation in a True-Batch Reactor (LAW, pH 7,20°C)A BromateA Bromide0 10 20 3040Ozone Exposure (mg-min/L)Figure 7.2: True-Batch Reactor Bromide Reaction and Bromate Formation (LAW, pH 7,20°C)99

7.1.3 Laboratory-Scale Continuous-Flow Ozone ContactorFive experiments were performed with the laboratory-scale continuous-flow ozone contactor.Ozone exposure was calculated as the product of the hydraulic residence time (HRT or tso) andthe steady-state effluent ozone residual. A summary of the experimental details are presented inTable 7.1. It can be seen that a lower sample flow rate produced a higher ozone exposure. Thiswas attributed to the corresponding increase in HRT due to the increased contact times within thereactor. The resulting bromate concentrations for each of the experiments are graphicallypresented in Figure 7.3.Table 7.1: Bench-Scale Flow-Through Reactor Scaling ExperimentsExp. Qwater Qrecirc Oa Resid HRT OE Bromide Bromate Accounted Br"No. (mL/min) (mL/min) (mg/L) (min) (mg-min/L) (ug/L)-----033 01001 72 300 1.97 6.3 12197.4722 3 4 5 6 71 58 48 32 18 300 300 300 200 200 2.87 2.78 3.31 3.43 3.96 6.4 7.8 9.4 14 25 182231489916 15151611168.6161816796276836420a•Bofa1I1510y=0.56xPossible Bromide Limiting Conditions0020 40 60Ozone Exposure (mg-min/L)80 100Figure 7.3: Bromate Formation in Laboratory-Scale Continuous-Flow Reactor100

The bromate concentration measured for the experiment with an ozone exposure of 99 mg-min/Lwas no greater than the bromate levels formed at an OE of 18 mg-min/L. This result indicated aplateau at about 16 ug/L bromate, and the subsequent exclusion of the higher OE data pointsfrom the OE versus bromate relationship. It is interesting to note that this plateau was observedin approximately the same range as for the true-batch ozonation experiments. As with the truebatchreactor experiments, it is unclear why a plateau was observed with a significant amount ofunreacted bromide remaining in the continuous-flow system, as shown in Figure 7.4. Up to thisplateau, however, the bromide concentration decreased with increasing levels of ozonation. Thebromide and bromate data, indicated 70 to 80 percent of the bromide was accounted for betweenthe residual bromide concentration and the bromide incorporated into bromate. It is expectedthat the portion of bromide that was not accounted for in either the unreacted bromide or bromateformed, had been incorporated into brominated organic compounds or existed as free bromine(HOBr/OBr).A BromideA Bromate0 *0 20 40 60Ozone Exposure (mg-min/L)80 100Figure 7.4: Bromide Reaction and Bromate Formation in a Laboratory-Scale Continuous-Flow Contactor7.1.4 Full-Scale and Pilot-Scale Ozone ContactorsA summary of the results from each of the full-scale and pilot-scale test is presented in Table 7.2.As before, larger applied ozone doses ultimately resulted in greater CT values and higherbromate concentrations. Based on these data, the amount of ozone contact was calculated fourdifferent ways to compare bromate formation for the full-scale and pilot-scale contactors. TheEPA accredited CT (CTswiR-tio) was calculated as the product of the ti 0 contact time and the101

ozone residual for each cell of the ozone contactor, excluding the first cell. Surface WaterTreatment Rule (SWTR) guidelines do not allow for CT credit from the first cell (USEPA, 1989;USEPA, 1990). However, this is likely a conservative indicator for ozonation because it isbelieved that some disinfection occurs within the first cell of the ozone contactors. Therefore,CT was also calculated with an "all cells" approach in which credit from the first cell was addedto CTswjR-tio- This parameter was labeled CTALL-UO- Additional CT representations, CTswrR-tsoand (^TALL-ISO, were calculated using tso (HRT) contact times instead of tio.Table 7.2: Los Angeles Aqueduct Filtration Plant, Full-Scale and Pilot-Scale CT (9°C)___________Ozone__________ HRT tio Bromate CTSwTR-tio CTALL-tsoOutput Applied Transferred Residual(mg/L) (mg/L) (mg/L) (min) (min) (ug/L) (mg-min/L) (mg-min/L)Full-Scale Plant Summary100%75%50%25%100%75%50%25%2.952.231.550.732.552.111.360.652.722.051.400.622.552.111.360.651.161.030.700.268.88 4.378.71 4.348.92 4.428.75 4.35Pilot-Scale Summary1.15 8.38 7.270.80 8.38 7.270.53 8.38 7.270.18 8.38 7.277.03.71.20.53.51.90.80.32.552.211.210.403.703.441.340.418.377.354.291.636.785.752.870.92For the ozone conditions evaluated at full-scale, the 100, 75, 50, and 25 percent experimentsproduced bromate levels of 7.0, 3.7, 1.2, and 0.5 p.g/L, respectively. The four experimentsconducted on the pilot-scale contactor resulted in final bromate concentrations of 3.5, 1.9, 0.8,and 0.3 ug/L for the 100, 75, 50, and 25 percent tests, respectively. The CT versus bromaterelationship for each method of CT calculation has been presented in Figure 7.5. As expected,the correlation between CT and bromate formation was lower for each CTALL than for thecorresponding CTswTR due the additional CT "credit" obtained in the first cell for the samebromate concentration.Along with the overall ozone contact versus bromate trends, the data from the Los AngelesAqueduct Filtration Plant full-scale and pilot-scale components of the study yielded insight intothe bromate formation trends within the contactors. Bromate concentrations were plottedspatially along the contactor (expressed in terms of cumulative HRT through the contactor) toprovide a pattern of bromate formation while the water was ozonated and traveled from cell tocell. The full-scale and pilot-scale bromate formation trends are presented in Figure 7.6 andFigure 7.7, respectively. A large portion of the bromate appeared to form within the later stagesof the contactors for the 75 and 100 percent tests, for both scales.The corresponding trends in CTALL-t50 development were also generated for both the full-scaleand pilot-scale tests, as seen in Figure 7.8 and Figure 7.9, respectively. It is interesting to notethat an almost linear relationship was detected between HRT and CT ALL-ISO, revealing the slowrate of ozone decay.102

y=1.29x y=1.03x•'--£ xy=0.76x y = 0.66x y = 0.49x y = 0.42xR =0.88 R =0.88 R =0.89 R =0.89• FullSWTRtlOAFullALLtlO* Full SWTR150X Full ALL t50n Pilot SWTRtlOo Pilot SWTRtSOA Pilot ALL tlOX Pilot ALL t5002468CT (mg-min/L)10Figure 7.5: Effect of CT Calculation of Bromate Formation Trends3a•-§esoto"«o•D0 4O D D0 2 4 6 8 10Relative Contactor Location as Cumulative HRT (min)Figure 7.6: Los Angeles Aqueduct Filtration Plant Bromate Production103

4c1| oto2CO0 OD-0-CD-O-A-DO-2468Relative Contactor Location as Cumulative HRT (min)10Figure 7.7: Los Angeles Aqueduct Filtration Pilot Plant Bromate Production0 2 4 6 8Relative Contactor Location as Cumulative HRT (min)10Figure 7.8: CTALL-tso Development Along Full-Scale Contactor104

.3BJD4 -U002468Relative Contactor Location as Cumulative HRT (min)10Figure 7.9: CTALL-tso Development Along Pilot-Scale Contactor7.1.5 Comparison of Full-, Pilot-, and Bench-ScalesFigure 7.10 shows the combined results of the multiple-scale comparison study. Sixrelationships are shown: CTswiR-no and CTALL-tso representations for both full- and pilot-scaleozone contactors, and the two bench-scale reactor relationships. CTswra-tio and CTALL-t50 werechosen because these calculated parameters represent the extremes in CT calculations. CTswrRtio,as per the SWTR guidelines, is a conservative estimate of the ozone contact so that factor ofsafety is incorporated to insure that public health is protected against microbial contamination.CTALL-tso might be considered more representative of the chemical reactions, as the dissolvedozone was in contact with the water constituents in all of the cells and for longer than the tiocontact time. Conceptually, CTALL-tso approximates the ozone exposure calculation used for thelaboratory reactors.As expected the full-scale system CTswxR-tio generated the highest relationship between bromateformation and calculated ozone contact. By the same calculation method, the pilot-scale systemperformed better. It was believed that this difference could be attributed to the differenthydraulics of the two systems. The full-scale contactor performed similar to a completely mixedsystem with a characteristic tio/tso of 0.50, determined by tracer testing. The hydraulics of thepilot-scale ozone contactor were closer to that of a plug-flow system, with a tio/tso of 0.87. Byutilizing the best estimate of ozone contact (CTALL-tso), the bromate formation relationshipbetween the pilot-scale and full-scale contactors converged. This convergence between105

hydraulically disparate contactors indicates that a chemically controlled relationship betweenbromate formation and ozone contact exists.2016a£ ceEofeesoCQ12840l-Log Cryptosporidium Inactivation(2.5 -10 ipg-min/L @ 9°C)""•••' Yd [ig/LBfomate M'CL" • FullSWTRtlO0 10 15Ozone Exposure or CT (mg-miii/L)APilotSWTRtlOo Full ALL t50A Pilot ALL t50X Bench-Scale (TB)+ Bench-Scale(CF)20Figure 7.10: Results of Los Angeles Aqueduct Filtration Plant Multiple-Scale ComparisonStudyThese relationships were also compared to the laboratory reactor relationships. Bromateformation versus ozone exposure in the true-batch ozone reactor and laboratory-scalecontinuous-flow ozone contactor, respectively, were essentially the same. This is believed tohave been a coincidental occurrence resulting from the scatter in the data (see Figure 7.2 andFigure 7.3), as the true-batch and continuous-flow experiments were performed at differenttemperatures, 20°C and 9°C, respectively.Therefore, these data indicate that the bench-scale systems could be used to approximate theresults of the larger pilot-scale and full-scale systems, provided the methods used to calculateozone contact approximate the total exposure of ozone to the water (i.e. OE and CTALL-ISO)- Thedata also illustrate that a pilot-scale system could be used to accurately predict bromateformation in a hydraulically disparate full-scale ozone contactor.7.2 NEUILLY SUR MARNE WATER TREATMENT PLANTThe same true-batch ozone reactor and laboratory-scale continuous-flow ozone contactor wereused to generate small-scale results for a comparison to full-scale and pilot-scale ozonecontactors at Compagnie Generale des Eaux's (CGE) Neuilly sur Mame Water Treatment Plant(WTP). While the testing at the Los Angeles Aqueduct Filtration Plant was carried out byvarying the ozonation conditions of one contactor, the full-scale tests performed at the Neuilly106

sur Marne WTP involved parallel contactors simultaneously operated at different experimentalconditions. The full-scale tests involved monitoring of 3 or 4, of 5 parallel counter-currentcontactors. Ozone experiments were conducted at each scale using Neuilly sur Mame WTPclarified and sand-filtered Mame River water, in May and October of 1998. The water qualityconditions measured during the two sets of ozone experiments are presented in Table 7.3.Table 7.3: Water Quality of Clarified and Sand-Filtered Marne River WaterParameter _____Testing PeriodTemperature (°C)Bromide (ng/L)pHAlkalinity (mg/L as CaCO3) DOC (mg/L)SUVA (L/mg-m)May 1998 19427.62301.12.3October 199815307.82201.52.0A linear relationship was observed between bromate formation and ozone exposure for the truebatchozone reactor and the laboratory-scale continuous-flow ozone contactor in the clarified andsand-filtered Marne River water. Figure 7.11 and Figure 7.12 also show that this linear trendalso appeared to extend to the pilot-scale ozone contactor at the Neuilly sur Marne WTP testingas well. The limited amount of full-scale data was not sufficient to determine if the linearrelationship would be observed at this scale as well. The full-scale results can be viewed asreplicate experiments between ozone contactors operated under similar hydraulic and waterquality conditions. The ozone contact for the true-batch reactor and laboratory-scale continuousflowozone contactor was quantified by calculating the ozone exposure. For the pilot-scale andfull-scale results, however, the quantity of ozone contact was expressed asFor the same ozone exposure, bromate formation was consistently greater for the laboratoryscalecontinuous-flow ozone contactor than for true-batch ozone reactor. During both testingperiods, the full-scale results were generally bounded by the results obtained from the twolaboratory reactors. The same bromate formation relationship was calculated from the pilotscaleand continuous-flow ozone contactors during the May 1998 testing period (1.2 ug/mgmin).However, a slightly lower production of bromate per unit of ozone contact was observedin the continuous-flow ozone contactor as compared to the pilot contactor (0.93 versus 1.1ug/mg-min) during the October 1998 testing period. Overall, the slightly higher temperature (19as compared 15°C) and bromide concentration (42 as compared to 30 ug/L) in the May testingperiod resulted in slightly higher bromate formation relationships, if any difference wasobserved. As a consistent relationship between the different ozone contactors utilizing Neuillysur Marne Water Treatment Plant clarified and sand-filtered Mame River water, it was notpossible to determine why the differences existed. However, either the pilot or continuous-flowozone contactors could be used to provide a conservative (high) estimate of bromate formation atfull-scale.107

Full-Scab• Pibt-ScaleA Continuous-Flow* True-Batch0 10 20 30 40or Ozone Exposure (mg-min/L)50Figure 7.11: Neuilly sur Marne Comparison of Ozone Contactors (May 1998)FuD-Scale• Pilot-ScaleA Continuous-Flow* True-Batch0 10 20 30 40or Ozone Exposure (mg-min/L)50Figure 7.12: Neuilly sur Marne Comparison of Ozone Contactors (October 1998)108

7.3 BRITANNIA WATER PURIFICATION FACILITYAdditional tests were performed during two testing periods using clarified Ottawa River water tocompare the bromate formation in different scales of ozone contactors. For these tests, resultsobtained from the pilot-scale ozone contactor at the Britannia Water Purification Facility werecompared to the data collected in a semi-batch ozone reactor and the laboratory-scalecontinuous-flow ozone contactor. The characteristics of the water quality during the two testingperiods are shown in Table 7.4.Table 7.4: Water Quality of Clarified Ottawa River WaterParameter ______________ August 1999 _______ October 1999Ambient Temperature (°C) 22 11Bromide (ug/L) 1 5 (spiked to 3 5) 15 (spiked to 3 5)UV254(cm' 1 ) 0.109 0.089TOC(mg/l) 3.7 2.8pH 6.18 (adjusted to 8) 6.15 (adjusted to 8)Alkalinity (mg/L as CaCO3) 9.2 (adjusted to 55) 10 (adjusted to 60)Turbidity (NTU)_____________ 0.08 ____________ 0.07 ______The experiments to directly compare bench-scale and pilot-scale ozonation results wereconducted in October 1999, when the Ottawa River temperature was 11°C. Additional benchscaletests were conducted in both cold water (7°C) and warm water (22°C) to examinetemperature effects.Preliminary experiments at 1 1°C showed no bromate formation at the ambient bromide level (15ug/L). Consequently, an additional 20 ug/L of bromide was added to bring the concentration upto 35 ug/L. At ambient pH (6.2), however, no detectable amount of bromate was formed, evenat a CTALL-tso of 50 mg-min/L. As a result, the pH was raised to 8 by adding NaOH and thealkalinity was adjusted with 55 mg/L of NaHCOs. The increase in alkalinity was sufficient tomaintain an approximate equilibrium with atmosphericThe bromate formation results for these adjusted water quality conditions are shown in Figure7.13. In each case, a simple linear correlation between bromate formation and ozone contact wasobserved. At the 95 percent confidence interval, no statistical difference existed between thepilot-scale and continuous-flow ozone contactors. While similar increases in bromateconcentration for a given unit change in ozone contact was observed in the semi-batch results,the absolute bromate concentrations were approximately 3 ug/L higher than the measurementsobtained with the other contactors.An additional series of bench-scale experiments were conducted in August 1999 to determinehow the performance of the reactors would compare at temperatures above and below 1 1°C. Forthese tests, the pH, alkalinity and bromide adjusted water was tested at ambient temperature(22°C) in the continuous-flow and semi-batch reactors. The water was then cooled to 7°C and109

the tests were repeated. In Figure 7.14, the linear relationship between bromate formation andozone contact was maintained for both reactors at both temperatures. Approximately half asmuch bromate was formed at 7°C when compared to 22°C for the same CTALL-ISO- It isinteresting that the colder water resulted in only about a 50 percent reduction in bromateformation for a given CTALL-t50 value.2015aE 10ofa£pao-•-Semi-Batch-A- Continuous-Flow-•-Pifot-Scale0 10 20 30 40CTALL-tso or Ozone Exposure (mg-min/L)50Figure 7.13: Britannia Water Purification Facility Ozone Contactor Comparison (October1999,pH8)Proposed CT requirements for a target level of Cryptosporidium inactivation are approximately 6times higher at 7°C than at 22°C (Rennecker et al., 1999; Oppenheimer et al, 2000). Thisimplies that a plant may have to increase the amount of ozone contact by 600 percent to maintainthe same level of Cryptosporidium control for these temperatures, while bromate formation mayonly be reduced by 50 percent for the same temperature difference. These particular resultssuggest the potential for greater bromate formation in colder water than in warm water existswhen ozonating to a specific level of inactivation. While these findings are consistent with thosedescribed in Section 5.1.2, they are contradictory to the batch tests described in Section 4.2. It isunclear why different results were observed for these different reactors.Excellent agreement between the results from the semi-batch reactor and the continuous-flowcontactor were observed in Figure 7.14, in contrast to the lack of agreement observed in Figure7.13. The experiments in Figure 7.13 and Figure 7.14 differed not only in temperature, but alsothe time of year that the water was collected (summer versus fall). As excellent agreement wasobtained at both 7°C and 22°C, the lack of agreement at 11°C was not expected to be attributableto temperature, but may depend on the specific water matrix. A reasonable correlation wasobserved between the laboratory-scale continuous-flow ozone contactor and the pilot-scale ozonecontactor.110

3020• Continuous-Flow (22°C)A Continuous-Flow (7°C)o Semi-Batch (22°C)A Semi-Batch (7°C)ofe* 10esI0010 20 30Ozone Exposure (mg-min/L)40 50Figure 7.14: Temperature Effect on Laboratory-Scale Reactors (August 1999, pH 8)7.4 CONCLUSIONSIt was shown that bench-scale reactors could provide reasonable simulations of pilot-scale andfull-scale bromate formation trends provided an accurate estimate of the amount of ozone contactcould be generated. Likewise, pilot-scale simulations can provide useful approximations of fullscaleresults. Such simulations would be useful in assessing tradeoffs between bromateformation and disinfection (CT) under various scenarios. However, these results also illustratedthat while the simulations could be used for trending purposes, the specific bromateconcentrations formed for given amounts of ozone contact do not always match betweendifferent contactors. The results from these tests also imply that chemical conditions, as opposedto hydraulic conditions, control the formation of bromate.Comparisons between full-scale ozonation at the Los Angeles Aqueduct Filtration Plant, pilotscaletests performed at the same facility, and two types of laboratory reactors indicated that themethod of calculating the ozone contact is critical to developing accurate predictions betweendifferent contactors. If ozone contact is calculated as CTper the SWTR guidelines (CTswiR-tio),the total amount of ozone contact is underestimated and hydrodynamic differences can result inlarge discrepancies between the concentrations of bromate formed in different contactors. As themethod of calculating ozone contact is improved, the relationship between bromate formationand ozone contact in hydrodynamically varied contactors tends to converge. At the Los AngelesAqueduct Filtration Plant, identical results were obtained between full-scale and pilot-scale onceozone contact was calculated at CTALL-tio; where CT credit for the first cell is included and the111

hydraulic residence time (HRT or tso) is used to characterize the contact time instead of tio.Results from the laboratory-scale continuous-flow ozone contactor also provided a reasonableestimate of the bromate formation at both of the larger scales.Using CTALL-tio as an estimate of the ozone contact for full-scale and pilot-scale system at theNeuilly sur Mame Water Treatment Plant and the Britannia Water Purification Facility,reasonable predictions of bromate formation could be made using the laboratory-scalecontinuous-flow ozone contactor. For both of these water agencies, the use of either a true-batchor semi-batch reactor could not consistently simulate bromate formation in the other reactors.Additional experiments performed at 7°C and 22°C in clarified Ottawa River water, indicatedthat excellent correlations between reactors could be obtained at different temperatures. Thesedata also indicated that the potential for greater bromate formation in colder water than warmwater exists when ozonating to a specific level of inactivation.112

CHAPTER 8. OZONE CONTACTOR MODELING8.1 BATCH AND SEMI-BATCH REACTOR MODELINGThe initial step in modeling Cryptosporidiwn parvum oocyst inactivation for the various reactorsutilized in this study was to determine C. parvum oocyst inactivation kinetics using ozone.Results obtained for multiple C. parvum oocysts inactivation experiments with the semi-batchreactor are presented in Figure 8.1. The inactivation levels presented here were normalized toviability of the control sample to which no ozone was exposed. The results were found to beindependent of the solution pH within the pH range of 6.5-8.5, indicating that molecular ozonewas responsible for inactivation. The lag phase factor Ni/N0 and pseudo first-order inactivationrate constant k^, corresponding to the Delayed Chick-Watson model, were determined to be 3.6and 1.77 (L/mg-min) at 20°C, respectively. These parameters were used for the modelingexperimental results described throughout this chapter.-10OX)o-10 1 2 3Ozone Exposure (mg-min/L)Figure 8.1: Effect of pH on Experimental and Fitted Kinetics of the Inactivation ofCryptosporidium parvum Oocysts (20°C, Semi-Batch Reactor)Batch ozonation tests were performed with all the natural waters investigated in this study. Theozone decomposition kinetics in selected samples are shown in Figure 8.2. Also shown in thefigure are the curves obtained from fitting the data with the kinetic model corresponding to thereactions represented in Table 2.11. The empirical parameters that determine the characteristicsof NOM in specific water, such as a, (3, y> and fa>» were calibrated so that the overalldecomposition kinetics matched the experimental results. These parameters were also included113

in Figure 8.2. The NOM fraction responsible for Reaction 100 in Table 2.11 was obtained fromozone decomposition curve and represented as a fraction of DOC (Fo). The correspondingpredicted bromate formation potential for each natural water tested was compared to theexperimental data and presented in Figure 8.3. While the model prediction of ozonedecomposition was accurate, and that of bromate formation was generally acceptable, there werelarge discrepancies for a few natural waters. This limitation in bromate formation predictioncould be the result of inaccuracies in bromate measurement, imperfections in the empiricalapproach to model NOM, or a combination of these two factors.coUa-10 20 30Time [min]40 5 10 15Time [min]20 40Time [min]Figure 8.2: Batch Ozone Decay Kinetics for Selected Natural Waters (pH 7,20°C)8.2 BENCH-SCALE FLOW-THROUGH OZONE CONTACTOR MODELINGTo model the laboratory-scale continuous-flow ozone contactor described in Section 2.2.3, it wasnecessary to understand the hydrodynamic characteristics of this reactor. A tracer test wasperformed with Rhodamine WT as a tracer compound for this purpose. The concentration ofRhodamine WT was determined with an Aminco Bowman Series 2 Spectrofluorometer usingexcitation and emission wavelengths of 555nm and 580nm, respectively. The tests wereperformed on the bubble column and recirculation line separately. Tracer solution was injectedas a pulse input into the inlet of the bubble column or the recirculation line after reaching steadystate conditions. Two-milliliter effluent samples were collected at maximum time intervals of 5114

seconds for an overall period of at least five times the theoretical hydraulic residence time ofeach component.I2520aI"• Experimental!D Model FitI 50SPW* CRW ACD* ANN* CCD SAC LAW* WPB DAL HOU NJA CGE OTT* Ammonia level was adjusted to fit the bromate formation potentialFigure 8.3: Fitted Batch Reactor Bromate Formation PotentialTracer test results with normalized time and concentration scales are presented in Figure 8.4.Actual times were divided by the corresponding hydraulic residence time, and actualconcentrations were divided by the ratio of total tracer mass added to reactor component volume.Tracer curves were analyzed to obtain the mean residence time and standard deviation. Thesevalues were then used to determine axial dispersion numbers assuming closed vessel boundaryconditions. The model tracer curve was generated from an axial-dispersion reactor (ADR) modelprogram developed in C++. hi this program, a finite difference approach was used to integratethe second-order partial differential equations. Both tracer curves were accurately described bythe axial dispersion model by a dispersion number of 0.01, corresponding to Peclet number of100, as shown in Figure 8.4 The tracer curves could be also modeled as a CSTR cascade of 50reactors. This analysis revealed that each component of the bench-scale flow-through reactorbehaves similar to an ideal plug-flow reactor (PFR). Therefore, the bench-scale flow-throughreactor was modeled as a PFR-side PFR, in which PFR represents the main bubble column andside-PFR represents the recirculation line.The results obtained for experiments performed with the bench-scale flow-through reactor usingthree selected natural waters are presented in Figure 8.5 and Figure 8.6. The inactivation of C.parvum oocysts and formation of bromate was investigated simultaneously in these tests. Thebromide level was adjusted to 90 ^ig/L for LAW and OTT waters. The temperature was kept at20°C and pH was adjusted to 7.5 for all of the experiments. Figure 8.5 shows the inactivationlevel of C. parvum oocyst at different CT. The level of inactivation was independent of the typeof natural water tested as long as the same CT was attained, once again confirming that C.parvum oocyst inactivation is only affected by exposure to dissolved molecular ozone. The115

integrated model prediction for each water showed reasonable agreement with experimental dataover the CT range investigated. These results validated the use of the PFR-side-PFR model torepresent the bench-scale flow-through reactor. The corresponding bromate formationpredictions are also shown in Figure 8.6. Contrary to C. parvum inactivation, bromate formationwas greatly affected by the nature of NOM, even though the initial bromide levels for LAW andOTT were the same. This large discrepancy in bromate formation was indicative of differencesin ozone consumption and hydroxyl radical inhibition by NOM. This trend was reflected in thebromate formation model predictions shown in Figure 8.6. The model showed good agreementwith the experimental data.1.0Contactor Column ExperimentADR Model (d=0.01)0.5satuaoU•ees0.01.0Recirculation ColumnExperiment-ADR Model (d=0.01)0.50.00Normalized TimeFigure 8.4: Tracer Test Results for the Bench-Scale Flow-Through Reactor andCorresponding ADR Modeling116

A SPWLAWOTT- - - - SPW Model PredictionLAW Model PredictionOTT Model Prediction10 20CT (mg-min/L)30Figure 8.5: Cryptosporidium parvum Inactivation Results and Corresponding ModelPredictions for the Laboratory-Scale Continuous-Flow Ozone Contactoraooto8521601208040A SPWa LAW» OTT— - - SPW Model Prediction——— LAW Model Prediction—------ OTT Model Prediction0 10 20CT (mg-min/L)30Figure 8.6: Bromate Formation and Prediction for the Bench-Scale Flow-Through OzoneContactor (LAW & OTT Spiked to 90 ug/L fir")The model-predicted CT requirements for inactivation of Iowa strain C. parvum oocysts atdifferent temperatures of the laboratory-scale continuous-flow ozone contactor are summarizedin Table 8.1. The ozone concentration was assumed to be constant throughout the reactor and117

hydraulic residence time was used to calculate CT. It is important to note that the CT required toobtain the same level of inactivation in the laboratory-scale continuous-flow ozone contactor isdramatically higher than that required in a batch reactor (Table 1.1). This results from the uniquehydrodynamic behavior of the laboratory-scale continuous-flow ozone contactor that deviatesfrom ideal plug-flow. The CT table for a CSTR, the other extreme ideal case, is presented inTable 8.2. The CT requirements for this case are much greater than that for a batch orlaboratory-scale continuous-flow ozone contactor.Table 8.1: Required CJfor C.parvum Oocysts Inactivation in Laboratory-ScaleContinuous-Flow Reactor (Iowa strain Oocysts with Inactivation Kinetics Shown in Table1.1, Recirculation Ratio of 10)Temperature(°C)-Log(N/N0)0.511.522.530.5 5 10 15 20 25 30Cr[mg-min/L]41.4 126 23.2 71.0 12.5 38.2 6.87 21.0 3.85 11.8 2.20 6.74 1.283.92246 388 538 690 138 218 302 387 74.5 117 162 208 40.964.5 89.3 114 . 23.0 36.2 50.1 64.3 13.1 20.7 28.7 36.7 7.6512.016.721.4Table 8.2: Required CJfor C.parvum Oocysts Inactivation in CSTR (Iowa strain Oocystswith Inactivation Kinetics Shown in Table 1.1)Temperature(°C)-Log(N/N0)0.51.01.52.02.53.00.5 5 10 15 20 25 30CT frtig-min/Ll56.1 200 656 2.09x1 03 31.5 112 368 1 .ISxlO3 17.0 60.5 198.2 633.6 9.32 33.2 108 348 5.23 18.7 61.1 195 2.99 10.7 34.9 112 1.746.2120.465.16.65xl032.llxlO43 .74x1 03 1 .ISxlO4 2.01x10 3 6.36x1 03 1 .llxlO3 3 .50x1 03 620 1 .96x1 03 355 1.12xl03 2076548.3 PILOT-SCALE OZONE CONTACTOR MODELINGIntegrated modeling of C. parvum inactivation and bromate formation was further tested on thepilot-scale ozone contactor at the Britannia Water Purification Facility. The experimental datawere obtained with the pilot-scale ozone contactor operated in both the counter-current and cocurrentmode. In each case ozone was only applied to the second column and allowed todissipate through the third column. The hydrodynamics of this reactor were first characterizedwith a tracer test using fluoride as a tracer compound. The experimental data for the case ofcounter-current operation mode are presented in Figure 8.7 along with the corresponding axialdispersionreactor model fit. The dispersion number within the second column during ozoneapplication was determined to be 0.6, while third column chamber had a much lower dispersion118

number of 0.04. The significantly higher dispersion number in the second column wasattributable to the induced mixing by the rising gas bubbles. During co-current operation and atthe same water and gas flow rates, the tracer test was used to calculate dispersion numbers of 0.3and 0.06 for the second and third column, respectively.• Bubble diffuserD Reacting chamberADR model0.5 1.5 2 2.5Normalized Time3.5Figure 8.7: Britannia Pilot Plant Counter-Current Tracer Test and Corresponding ADRModeling (Qwater = 5L/min, Qgas = 1.42 L/min, 0.5°C)The ADR model predictions for dissolved ozone concentration profile, bromate formation and C.parvum inactivation in the bubble column and the reacting chamber were compared to theBritannia Pilot Plant experimental results, as shown in Figure 8.8. Although the model deviatedfrom the experimental data, shape of the predicted ozone profiles was similar to those of the data.It is believed that the primary major reason for the deviation was that the model was based onreaction rate constants only available at 20°C while the experiments were performed at 0.5°C.As the ozone residuals were underpredicted by the model at this low temperature, it was notsurprising that the corresponding bromate formation was underpredicted. It was believed that thepredicted level of concomitant disinfection was underpredicted as well.119

(a) Bubble Column Simulation1.00.90.80.7I)E 0.6•u

8.4 FULL-SCALE OZONE CONTACTOR MODELINGFull-scale ozone contactor performance was also simulated with the integrated bromateformation and C. parvum inactivation model. The tracer test data obtained from the Los AngelesAqueduct Filtration Plant was analyzed for the evaluation of hydrodynamic characteristics.Tracer tests were performed using Rhodamine WT introduced as a step input. The axialdispersionmodel was applied to estimate a dispersion number of 0.054 for the entire reactor, asshown in Figure 8.9. This single dispersion number was used for the modeling the differentsections of the contactor (ozone application cell, ozone reaction cells, rapid mixers) even thoughdifferent hydraulic conditions were expected, because separate tracer data was not available.1.0o oaoa>awa•aVeso0.5• Positive Step Inputo Negative Step InputADR Model0.00 1 2Normalized TimeFigure 8.9: Los Angeles Aqueduct Filtration Plant Tracer Tests and Corresponding ADRModeling (Qwater = 85 MGD, Q gas = 17.8 scfh)Figure 8.10 shows the dissolved ozone and bromate concentrations observed at various samplingtaps of the contactor. The graph is presented in terms of normalized cumulative volume of theozone contactor including rapid mixers. The model was initialized using the kinetic informationobtained from the batch ozonation test for LAW water. Simulations were performed for each ofthe experimental testing conditions: 100, 75, 50, and 25 percent of the ozone generation capacity.The model simulations had the same trends as those observed for experimental data. It isbelieved that the deviations from the data are much smaller than those observed with the pilotscaleozone contactor at the Britannia Water Purification Facility because the temperature in thiscase was 9°C, closer to the 20°C derived reaction rate constants. Based on C. parvum oocystinactivation modeling, this plant would be expected to achieve about 3-log inactivation for 75percent capacity operation at 20°C.121

IU°2.01.0 -(a)Liquid PhaseOzoneConcentrationProfile0.5 -(c)C. parvumInactivation00.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0Normalized Cumulative Volume• Experimental datafor 100% capacityO Experimental datafor 75% capacityT Experimental datafor 50% capacityV Experimental datafor 25% capacity——— Model simulationfor 100% capacity— • • • Model simulationfor 75% capacity— — Model simulationfor 50% capacity— Model simulationfor 25% capacityFigure 8.10: Los Angeles Aqueduct Filtration Plant Measured and Predicted OzoneProfile, Bromate Formation and Cryptosporidium Inactivation (pH 8.2,33 ng/L Br", 1.9mg/L DOC, 9°C Qwater = 85 MGD, Qgas = 17.8 scfh)8.5 SUMMARYIntegrated models for ozone decomposition, bromate formation, and C. parvum inactivation weredeveloped for four different types of reactors and contactors: true-batch ozone reactor,laboratory-scale continuous-flow ozone contactor with external recirculation, pilot-scale ozonecontactor and full- scale ozone contactor. While employing the same reaction mechanisms,122

different programs were developed to solve to specific mathematical problems corresponding tothe different hydrodynamic schemes. Once the empirical kinetic evaluation of NOM wasperformed in batch tests, this information was utilized to simulate the ozone contactor at eachscale. The integrated modeling provided a good strategy to simulate the ozone contactorperformance during scale-up. This simulation provided not only the final effluent watercharacteristics, but also generated the chemical species concentration profiles and C. parvuminactivation levels along the ozone contactors. However, there were modeling limitationsidentified that should be addressed in future research.• Simulations for ozone decomposition and bromate formation were possible only at 20°C, thetemperature at which the rate constants for each reaction were evaluated.• Empirical approach to model the interactions of NOM with ozone and secondary oxidantswas not adequate for some natural waters.• Accurate measurement of primary species such as ozone, bromine, and bromate, as well assecondary species, such as hydroxyl radical, were needed for more robust modeling atmechanistic level.Despite these limitations, this study suggests that the model simulation is a powerful tool tounderstand the performance of ozone contactors at various configurations and operatingconditions. The model was especially useful in assessing the actual C. parvum inactivation levelin full-scale ozone contactors for which testing with actual microorganisms is currentlyimpossible. Finally, it is expected that the model should provide a promising approach tooptimize and design ozone contactors.123

CHAPTER 9. SUMMARY AND CONCLUSIONSFacilities attempting to comply with regulations governing pathogen inactivation anddisinfection by-product minimization are faced with the challenge of balancing their systems andoptimizing their treatment processes. Impending regulations are expected to require up to 2.5-logs of additional Cryptosporidium treatment, potentially by disinfection. Ozone has beenshown to be an effective disinfectant for Cryptosporidium. The obvious implication to the use ofozone is the formation of bromate in excess of the current maximum contaminant level (MCL),with the potential for the MCL to be further decreased. Full-scale treatment plants will berequired to optimize processes to meet both requirements in reducing the acute and chronic risksassociated with Cryptosporidium and bromate.A survey of operating ozone facilities in North America and Europe was initially conducted tounderstand bromate occurrence under current levels of ozone application. The average bromateconcentration at 24 full-scale ozonation plants, based on 78 samples from three separatesampling campaigns for the existing levels of ozonation, was 3.9 ug/L. The average percentconversion of bromide to bromate was 6.7 percent. The 10th, 50th (median), and 90th percentilebromate values was determined to be 0.2, 1.2, and 13 ug/L, respectively. The survey indicatedthat there were some bromate issues with current ozonation practices at the full-scale (whichcurrently target Giardia inactivation). Specifically, several utilities were forming bromate atlevels in excess of the Stage 1 D/DBP Rule MCL of 10 ug/L; 11 percent of the samples analyzedwould be considered out of compliance. Future compliance may be difficult for a greaternumber of utilities when operating at disinfection levels capable of Cryptosporidiuminactivation.Bromate formation can be affected by many factors ranging from naturally occurring compounds(i.e., NOM), water quality and temperature. Understanding the influence of these parameters isparamount to developing minimization strategies. The ubiquitous presence of NOM in sourcewaters has implications to ozone reaction kinetics that influence bromate formation. Specificfractions (i.e., hydrophobic) are known to exert a substantial ozone demand while producingproducts that continue the ozone decomposition cycle. The heterogeneity of NOM providesreactive sites for both the inhibition and the promotion of ozone decay, which in turn influencesthe oxidation potential of bromide, by ozone, into intermediate products that lead to theformation of bromate. Understanding the role of NOM and its operationally and functionallydefinedfractions contributes to the elucidation of specific control strategies that will minimizebromate formation.The background natural organic matter of 14 natural waters was characterized by measurementsof the DOC, UV254 absorbance and UV2oo-30o absorbance. The NOM was also fractionated intohydrophobic, hydrophilic and transphilic fraction using macroporous, nonionic resins. Sizeexclusion chromatography was also used to determine the apparent molecular weight of thenatural organic matter. These various parameters were then statistically correlated to bromateformation under a set of standard ozonation conditions (true-batch ozone reactor; temperature =20°C; ozone dose = 1 mg ozone per mg DOC). For the 14 waters studied, the DOCconcentrations ranged from 1.4 to 7.3 mg/L and had a median bromide concentration of 42 ug/L.124

The SUVA values ranged from 1.4 to 3.8 L/mg-m. The average hydrophobic fraction accountedfor 50 percent of the NOM, with the transphilic and hydrophilic fractions averaging 21 and 29percent of the NOM, respectively. While all of the NOM fractions exerted an ozone demand, thehydrophobic fraction was found to exert the highest demand per unit DOC. Based on thestandard bromate formation testing the hydrophobic fraction was negatively correlated withbromate formation, while the transphilic and hydrophilic fractions were positively correlated.Bromate formation in these waters was evaluated over a range (0.5-log to 3.0-logs) of predictedCryptosporidium inactivation levels. At 1-log Cryptosporidium inactivation, approximately halfof the waters were expected to produce bromate in excess of 10 ug/L. It was noted that whilethese waters had a range of water qualities and bromide concentrations, the higher theconcentration of bromide the higher the percent of the bromide that was converted to bromate.To reduce the concentration of bromate formed, pH depression, ammonia addition and hydroxylradical scavenger addition were evaluated. By depressing the pH from 8 to 7 to 6, a generalreduction in bromate formation of 30 to 50 percent per unit decrease in pH was observed. Thisreduction in bromate formation resulted in an increase in the concentration of total organicbromide formed. The addition of 0.5 mg/L ammonia-nitrogen to these waters resulted in areduction in bromate formation for all of the waters that would normally form over 10 ug/L ofbromate. Increasing the ammonia concentration to 1.0 mg/L ammonia-nitrogen resulted in someadditional reduction in bromate formation. It was estimated that ammonia addition might be aneffective bromate formation control strategy for those waters within 10 to 20 ug/L of the MCL.It was also revealed that the cumulative effects pH depression together with ammonia additioncould be used for waters in which bromate formation was particularly problematic.A preliminary investigation of the addition of a hydroxyl radical scavenger revealed the additionof 1 mM of t-butanol prevented bromate formation. While the addition of t-butanol to municipaldrinking water supply might not currently be an acceptable practice, it does illustrate theeffectiveness of this approach. This illustrates the need for additional research to identify anacceptable hydroxyl radical scavenger and determine the minimum amount necessary toeffectively inhibit bromate formation. It was just as important to note that since the addition of ahydroxyl radical scavenger completely inhibited bromate formation, it appeared that bromateformation in natural waters does not proceed through the "direct pathway" as discussed by Songet al. (1997), but must proceed through pathways in which hydroxyl radicals are needed.Consequently, the radical scavenging by natural organic matter likely plays a significant role inthe differences observed in bromate formation between natural waters.In addition to these chemical approaches to bromate minimization, hydrodynamic strategies werealso investigated. However, through bench-scale and pilot-scale experiments, no compellingreason was identified to employ staged/tapered ozonation for bromate minimization. It was alsodiscovered that bromate formation could not be reduced by operating the ozone contactors ineither a co-current or counter-current mode. Nevertheless, the operation of the ozone contactorin a co-current mode might have provided subtle opportunities for optimizing disinfection. As aresult, these tests provided indications that bromate formation was predominantly controlled bychemical conditions and not hydraulic parameters.125

The temperature was observed to reduce bromate formation in true-batch, semi-batch andcontinuous-flow laboratory reactors. However, its impacts on the amount of bromate formed fora given level of Cryptosporidium disinfection varied between these reactors. In the true-batchexperiments, decreasing the temperature from 20°C to 10°C resulted in about a 40 percentreduction in the bromate formed for 2-logs of Cryptosporidium inactivation. Using thelaboratory-scale continuous flow reactor, decreasing the temperature from 25°C to 5°C, resultedin a 15 to 72 percent increase in the amount of bromate formed for 2-logs of Cryptosporidiuminactivation. An approximate 50 percent increase in the amount of bromate formed for 2-logs ofCryptosporidium inactivation was also observed in a semi-batch reactor as the temperature wasdecreased from 22°C to 7°C. It is unclear why different results were observed for these differentreactors.Many of the above trends were developed through bench-scale tests. Concerns over theapplicability of these results to larger scale (pilot-scale and full-scale) reactors were addressedthrough a series of comparability tests. It was shown that bench-scale reactors could providereasonable simulations of pilot-scale and full-scale bromate formation results provided anaccurate estimate of the amount of ozone contact at the larger scale could be generated. As such,the approximation of ozone contact by CT, as defined by the SWTR, resulted in a lack ofcomparability. By calculating ozone contact with the hydraulic retention time instead of tio, andby giving credit to the first cell of the pilot-scale and full-scale reactors correlations to the benchscaleresults could be developed. Likewise, pilot-scale simulations could be used to provideapproximations of full-scale results. Such simulations could be useful in assessing tradeoffsbetween bromate formation and disinfection (CT) under various scenarios. However, theseresults also illustrated that while the simulations could be used for trending purposes, the specificbromate concentrations formed for given amounts of ozone contact do not always match betweendifferent contactors. The results from these tests also lent additional credence to the theory thatchemical conditions, as opposed to hydraulic conditions, control the formation of bromate.The results of these reactor scale comparability tests were also used to validate the performanceof a series of integrated models that could be used to predict ozone decomposition, bromateformation and Cryptosporidium inactivation in four different types of reactors. While limitationsexisted, it was demonstrated that the model simulations could be used to understand theperformance of the ozone contactors at various configurations and operating conditions.126

APPENDIX1 . Solver routines for bromate formation and Cryptosporidium parvum inactivation in batch andPFR-side PFR reactor. These routines are utilized by a main function that should beprogrammed for the specific purposes. Main functions for different modeling were notincluded./*Solve the set of n Linear Equations AX=B/*******************#*******#****#*********/void ludcmp(double a[][N+l], int *indx, double *d){int i,imaxj,k;double big,dum,sum,temp;double w[N+l];*d=1.0;big=0.0;for(j=la big) big=temp;if (big = 0.0) break;w[i]=1.0/big;sum=a[i][j];for (k=l;k

for(i=l;i

if (k = kmax || k = kopt+1) {red=SAFE2/err[km];break;}else if (k = kopt && alf[kopt-l][kopt] < err[km]) {red=1.0/err[km];break;}else if (kopt = kmax && alf[km][kmax-l]

2. Routines that provide kinetic information for bromate formation. These routine are utilizedonly for the case of batch and PFR-PFR simulations _____________________double k24a = l.OelO;/*********##********#***#*#*#***********#/ double k24b = 3.3e7;/*Variable Definitiondouble k25a = 4.0e6;/****** #***************#**#**************/ double k25b = 1.3elO;double k26 = 4.4e 10;[03]double k27 = 2.0e8;// y[2] = CT_H03double k28a = l.OelO;// y[3] = VACANTdouble k28b=1.0e5;// y[4] = CT_HO2double k29=2.0e9;// y[5] = VACANTdouble k30a = 8.3e8;// y[6] = [OH]Radicaldouble k30b = l.OelO;CT_H2O2double k31 a = 4.6e2;// y[8] = CT_C03double k31b = 7.9elO;// y[9] = CT_C03rdouble k33 = 1.5e8;//y[10] =CT_PO4double k34 = 4.0e9;= [Br-]double k35=4.5e9;= [Br]Radicaldouble k36 = 2.0e9;// y[13] = [BrOH-]Radicaldouble k37 = 3.5e9;//y[14] = [Br2-]Radicaldouble k38 = 5.0e9;//y[15] = [Br3-]double k39 = 3.4e8;//y[16] =CT_HOBrdouble k40 = 8.0e7;= [Br2]double k41 = 1.9e9;= [BrO]Radicaldouble k42=2.0e9;= [BrO2-]double k43 a = 1.4e9;y[20] = [BrO2]Radicaldouble k43b = 7.0e7;= [Br2O4]double k44 = 7.0e8;// y[22] = [BrO3-]double k53 = 8.5e6;// y[23] = [t-BuOH]double k54 = 3.9e8;//y[24] =Ct_NH3double k55=4.3e7;// y[25] = [NH2Br]double k56 = l.le8;// y[26] = NOM1double k63 = 2.0e4;//y[27] =NOM2double k64 = 1.5e5;//y[28] =NOM3double k71=2.8e6;//y[29] =TOBrdouble k72=2.7e7;double k73 = 7.5e9;/****************************************/ double k74 = 7.6e8;/*Rate Constants of Reactionsdouble k75= 3.5e9;/*************************#****#*********/ double k81 = 8.0e7;double k82=4.0el;double kl = 70;double k90 = 5.9e8;double k3 = 1.6e9;double klOO;double k5 = Lle5;double klOl =4.0e8;double k6 = 2.6e8;double kl 02 = 1.0e3;double k7 = 5.0e9;double Alpha;// Fraction to Hydroxyl Radicaldouble k8 = l.OelO;double Beta;// Fraction to Superoxide Radicaldouble k9 = 5.0e9;double Gamma;// Fraction to Bromidedouble klO = l.OelO;double PRT, HYD;double kll = 5.0e9;double aO_HO3, al_HO3;double k20 = 1.6e2;double aO_HO2, al_HO2;double k21 = 3.3e2;double aO_Peroxide, al_Peroxide;double k22 = 1.0e2;double aO_CO3r, al_CO3r;double k23 = 1.0e5;double aO_HOBr, al_HOBr;130

double aO_CO3, al_CO3, a2_CO3;double aO_PO4, al_PO4, a2_PO4, a3_PO4;double aO_NH3, al_NH3;/****************************************//* Acid-Base Equilibrium Calculation/****************************************/void pHequilibrium(double pH) {// Hydrogen Ion ConcentrationPRT=pow(10,-pH);HYD =pow(10,-14.17)/PRT;//H03/03-PairaO_HO3 = PRT / ( pow (10, -8.2) + PRT );al_HO3 = l.F-aO_HO3;//H02/02-PairaO_HO2 = PRT / ( pow (10, -4.8) + PRT );al_HO2 = l.F-aO_HO2;// H2O2/HO2- PairaO_Peroxide = PRT /( pow (10, -1 1 .6) + PRT );al_Peroxide = l.F - aO_Peroxide;// HCO3.radical/CO3-.radical PairaO_CO3r = PRT / ( pow (10, -9.6) + PRT );al_CO3r=l.F-aO_CO3r;//HOBr/OBr-PairaO_HOBr = PRT / ( pow (10, -8.8) + PRT );al_HOBr = l.F - aO_HOBr;// Carbonate SystemaO_CO3 = PRT * PRT / ( PRT * PRT + PRT * pow(10, -6.35) + pow (10, -6.35) * pow (10, -10.35) );al_CO3 = aO_CO3 / PRT * pow(10, -6.35);a2_CO3 = l.F - aO_CO3 - al_CO3;// Phosphate SystemaO_PO4 = PRT * PRT * PRT /( PRT * PRT * PRT +PRT * PRT * pow(10, -2.3) + PRT * pow(10,-2.3) *pow(10,-7.2) + pow(10,-2.3) * pow(10,-7.2) *pow(10,-12.3));al_PO4 = aO_PO4 / PRT * pow(10, -2.3);a2_PO4 = al_PO4 / PRT * pow(10, -7.2);a3_PO4 = l.F - aO_PO4 - al_PO4 - a2_PO4;//NH4+/NH3PairaO_NH3 = PRT / ( pow (10, -9.3) + PRT );al_NH3 = l.F-aO_NH3;/****************************************//* Analytical Evaluation of Jacobiany**# *************************************/void jacobn(double x, double y[], double dfdx[],double dfdy[][N+l])int i;for(i=l;i

dfdy[2][9]=0.0;dfdy[2][10]=0.0;dfdy[2][ll] = 0.0;dfdy[2][12]=0.0;dfdy[2][13] = 0.0;dfdy[2][14] = 0.0;dfdy[2][15]=0.0;dfdy[2][16] = 0.0;dfdy[2][17] = 0.0;dfdy[2][18]=0.0;dfdy[2][19]=0.0;dfdy[2][20] = 0.0;dfdy[2][21] = 0.0;dfdy[2][22] = 0.0;dfdy[2][23]=0.0;dfdy[2][24] = 0.0;dfdy[2][25]=0.0;dfdy[2][26] = Alpha * klOO * y[l];dfdy[2][27] = 0.0;dfdy[2][28]=0.0;dfdy[2][29] = 0.0;dfdy[3][l]=0.0;dfdy[3][2]=0.0;dfdy[3][3] = 0.0;dfdy[3][4]=0.0;dfdy[3][5]=0.0;dfdy[3][6] = 0.0;dfdy[3][7] = 0.0;dfdy[3][8]=0.0;dfdy[3][9] = 0.0;dfdy[3][10]=0.0;dfdy[3][ll]=0.0;dfdy[3][12] = 0.0;dfdy[3][13] = 0.0;dfdy[3][14]=0.0;dfdy[3][15]=0.0;dfdy[3][16] = 0.0;dfdy[3][17]=0.0;dfdy[3][18]=0.0;dfdy[3][19]=0.0;dfdy[3][20] = 0.0;dfdy[3][21] = 0.0;dfdy[3][22]=0.0;dfdy[3][23] = 0.0;dfdy[3][24] = 0.0;dfdy[3][25] = 0.0;dfdy[3][26] = 0.0;dfdy[3][27] = 0.0;dfdy[3][28] = 0.0;dfdy[3][29] = 0.0;dfdy[4][l] = 2*kl * HYD - k3 * al_HO2 * y[4] + k6* y[6] + k71 * al_Peroxide * y[7];dfdy[4][2] = - klO * al_HO2 * y[4] * aO_HO3;dfdy[4][3]=0.0;dfdy[4][4] = - k3 * y[l] * al_HO2 - k8 * y[6] *al_HO2 - klO * al_HO2 * aO_HO3 * y[2] - k37 *al_H02*aO_HOBr*y[16];dfdy[4][5]=0.0;dfdy[4][6] = k6 * y[l] - k8 * al_HO2 * y[4] + k72 *aO_Peroxide * y[7] + k73 * al_Peroxide * y[7] +Beta * klOl * y[27];dfdy[4][7] = k71 * y[l] * al_Peroxide + k72 *aO_Peroxide * y[6] + k73 * al_Peroxide * y[6];dfdy[4][8]=0.0;dfdy[4][9] = 0.0;dfdy[4][10] = 0.0;dfdy[4][ll]=0.0;dfdy[4][12]=0.0;dfdy[4][13]=0.0;dfdy[4][14]=0.0;dfdy[4][15]=0.0;dfdy[4][16] = - k37 * al_HO2 * y[4] * aO_HOBr;dfdy[4][17]=0.0;dfdy[4][18]=0.0;dfdy[4][19]=0.0;dfdy[4][20] = Q.O;dfdy[4][21] = 0.0;dfdy[4][22] = 0.0;dfdy[4][23] = 0.0;dfdy[4][24] = 0.0;dfdy[4][25]=0.0;dfdy[4][26]=0.0;dfdy[4][27] = Beta * klOl * y[6];dfdy[4][28] = 0.0;dfdy[4][29] = 0.0;dfdy[5][l]=0.0;dfdy[5][2]=0.0;dfdy[5][3]=0.0;dfdy[5][4] = 0.0;dfdy[5][5]=0.0;dfdy[5][6] = 0.0;dfdy[5][7]=0.0;dfdy[5][8]=0.0;dfdy[5][9]=0.0;dfdy[5][10] = 0.0;dfdy[5][ll] = 0.0;dfdy[5][12]=0.0;dfdy[5][13]=0.0;dfdy[5][14]=0.0;dfdy[5][15] = 0.0;dfdy[5][16]=0.0;dfdy[5][17]=0.0;dfdy[5][18] = 0.0;dfdy[5][19]=0.0;dfdy[5][20] = 0.0;dfdy[5][21]=0.0;dfdy[5][22]=0.0;132

dfdy[5][23]=0.0;dfdy[5][24] = 0.0;dfdy[5][25] = 0.0;dfdy[5][26] = 0.0;dfdy[5][27] = 0.0;dfdy[5][28] = 0.0;dfdy[5][29] = 0.0;dfdy[6][l] = - k6 * y[6] + k71 * alJPeroxide * y[7];dfdy[6][2] = k5 * aO_HO3 - k9 * y[6] * aO_HO3;dfdy[6][3] = 0.0;dfdy[6][4] = - k8 * y[6] * al_HO2;dfdy[6][5] = 0.0;dfdy[6][6] = - k6 * y[l] - 4*k7 * y[6] - k8 * al_HO2* y[4] - k9 * aO_HO3 * y[2] - k24a * y[l 1] - k35 *al_HOBr * y[16] - k36 * aO_HOBr * y[16] - k41 *y[19] - k42 * y[20] - k53 * al _CO3 * y[8] - k54 *a2_CO3 * y[8] - k63 * al_PO4 * y[10] - k64 *a2_PO4 * y[10] - k72 * aO_Peroxide * y[7] - k73 *al_Peroxide * y[7] - k90 * y[23] - klOl * y[27];dfdy[6][7] = k71 * y[l] * al_Peroxide - k72 *aO_Peroxide * y[6] - k73 * al J>eroxide * y[6];dfdy[6][8] = - k53 * al_CO3 * y[6] - k54 * a2_CO3* y[6];dfdy[6][9]=0.0;dfdy[6][10] = - k63 * y[6] * al_PO4 - k64 * y[6] *a2_PO4;dfdy[6][ll]=-k24a*y[6];dfdy[6][12] = 0.0;dfdy[6][13]=k24b;dfdy[6][14] = 0.0;dfdy[6][15]=0.0;dfdy[6][16] = - k35 * y[6] * al_HOBr - k36 * y[6] *aO_HOBr;dfdy[6][17] = 0.0;dfdy[6][18]=0.0;dfdy[6][19]=-k41 * y[6];dfdy[6][20] = - k42 * y[6];dfdy[6][21]=0.0;dfdy[6][22]=0.0;dfdy[6][23]=-k90*y[6];dfdy[6][24] = 0.0;dfdy[6][25] = 0.0;dfdy[6][26] = 0.0;dfdy[6][27]=-k!01*y[6];dfdy[6][28]=0.0;dfdy[6][29] = 0.0;dfdy[7][l] = - k71 * al_Peroxide * y[7];dfdy[7][2] = k9 * y[6] * aO_HO3 + 2* kl 1 * aO_HO3* aO_H03 * y[2];dfdy[7][3] = 0.0;dfdy[7][4] = 0.0;dfdy[7][5] = 0.0;dfdy[7][6] = 2 * k7 * y[6] + k9 * aO_HO3 * y[2] -k72 * aO_Peroxide * y[7] - k73 * al_Peroxide * y[7];dfdy[7][7] = - k71 * y[l] * alJPeroxide - k72 *aO_Peroxide * y[6] - k73 * al_Peroxide * y[6] - k74* al_Peroxide * aO_HOBr * y[16];dfdy[7][8] = 0.0;dfdy[7][9] = 0.0;dfdy[7][10]=0.0;dfdy[7][ll]=0.0;dfdy[7][12.]=0.0;dfdy[7][13]=0.0;dfdy[7][14] = 0.0;dfdy[7][15]=0.0;dfdy[7][16] = - k74 * al_Peroxide * y[7] *aOJHOBr;dfdy[7][17]=0.0;dfdy[7][18]=0.0;dfdy[7][19] = 0.0;dfdy[7][20] = 0.0;dfdy[7][21]=0.0;dfdy[7][22]=0.0;dfdy[7][23] = 0.0;dfdy[7][24]=0.0;dfdy[7][25] = 0.0;dfdy[7][26] = 0.0;dfdy[7][27] = 0.0;dfdy[7][28] = 0.0;dfdy[7][29] = 0.0;dfdy[8][l]=0.0;dfdy[8][2] = 0.0;dfdy[8][3] = 0.0;dfdy[8][4] = 0.0;dfdy[8][5] = 0.0;dfdy[8][6] = - k53 * al_CO3 * y[8] - k54 * a2_CO3* y[8];dfdy[8][7] = 0.0;dfdy[8][8] = - k53 * al_CO3 * y[6] - k54 * a2_CO3*y[6];dfdy[8][9] = k55 * al_CO3r * al_HOBr * y[16] +k56*al_CO3r*y[19];dfdy[8][10]=0.0;dfdy[8][ll] = 0.0;dfdy[8][12] =0.0;dfdy[8][13] = 0.0;dfdy[8][14] = 0.0;dfdy[8][15]=0.0;dfdy[8][16] =k55 * al_CO3r * y[9] * al_HOBr;dfdy[8][17]=0.0; •dfdy[8][18] = 0.0;dfdy[8][19] = k56 * al_CO3r * y[9];dfdy[8][20]=0.0;dfdy[8][21] = 0.0;dfdy[8][22] = 0.0;dfdy[8][23]=0.0;dfdy[8][24] = 0.0;dfdy[8][25] = 0.0;dfdy[8][26] = 0.0;133

dfdy[8][27]=0.0;dfdy[8][28] = 0.0;dfdy[8][29] = 0.0;dfdy[9][l]=0.0;dfdy[9][2]=0.0;dfdy[9][3] = 0.0;dfdy[9][4]=0.0;dfdy[9][5]=0.0;dfdy[9][6] = k53 * al_CO3 * y[8] + k54 * a2_CO3 *y[8];dfdy[9][7]=0.0;dfdy[9][8] = k53 * al_CO3 * y[6] + k54 * a2_CO3 *y[6];dfdy[9][9] = - k55 * al_CO3r * al_HOBr * y[16] -k56 * al_C03r * y[19];dfdy[9][10] = 0.0;dfdy[9][ll] = 0.0;dfdy[9][12] = 0.0;dfdy[9][13] = 0.0;dfdy[9][14] = 0.0;dfdy[9][15] = 0.0;dfdy[9][16] = - k55 * al_CO3r * y[9] * al_HOBr;dfdy[9][17] = 0.0;dfdy[9][18] = 0.0;dfdy[9][19] = - k56 * al_CO3r * y[9];dfdy[9][20] = 0.0;dfdy[9][21]=0.0;dfdy[9][22] = 0.0;dfdy[9][23] = 0.0;dfdy[9][24] = 0.0;dfdy[9][25] = 0.0;dfdy[9][26] = 0.0;dfdy[9][27] = 0.0;dfdy[9][28] = 0.0;dfdy[9][29]=0.0;dfdy[10][l] = 0.0;dfdy[10][2] = 0.0;dfdy[10][3]=0.0;dfdy[10][4]=0.0;dfdy[10][5]=0.0;dfdy[10][6] = - k63 * al_PO4 * y[10] - k64 *a2_PO4 * y[10];dfdy[10][7]=0.0;dfdy[10][8] = 0.0;dfdy[10][9] = 0.0;dfdy[10][10] = - k63 * y[6] * al_PO4 - k64 * y[6] *a2_PO4;dfdy[10][ll] = 0.0;dfdy[10][12]=0.0;dfdy[10][13] = 0.0;dfdy[10][14] = 0.0;dfdy[10][15]=0.0;dfdy[10]f!6]=0.0;dfdy[10][17] = 0.0;dfdy[10][18] = 0.0;dfdy[10][19] = 0.0;dfdy[10][20] = 0.0;dfdy[10][21] = 0.0;dfdy[10][22] = 0.0;dfdy[10][23] = 0.0;dfdy[10][24] = 0.0;dfdy[10][25] = 0.0;dfdy[10][26] = 0.0;dfdy[10][27] = 0.0;dfdy[10][28] = 0.0;dfdy[10][29] = 0.0;dfdy[ll][l] = - k20 * y[ll] + k21 * al_HOBr * y[16]+ k82 * y[25];dfdy[ll][2] = 0.0;dfdy[ll][3] = 0.0;dfdy[ll][4]=0.0;dfdy[ll][5]=0.0;dfdyfl I]f6] = -k24a*y[ll];dfdy[l 1][7] = k74 * al_Peroxide * aO_HOBr * y[16];dfdy[ll][8]=0.0;dfdyfl 1][9] = 0.0;dfdy[ll][10] = 0.0;dfdy[l 1][1 1] = - k20 * y[l] - k24a * y[6] - k27 *y[13] - k28a * y[12] - k30b * y[17] - k31b *aO_HOBr * y[16] * PRT;dfdyfl l]f 12] = -k28a*y[ll]+k34*al_HOBr*dfdyfl 1][13] = k24b - k27 * y[ll];dfdyfl 1][14] = k28b + 2 * k29 * y[14] + k40 * y[19];dfdyfl I][15] = k30a;dfdy[ll][16] = k21 * y[l] * al_HOBr-k31b *aO_HOBr * PRT * y[l 1] + k34 * y[12] * al_HOBr +k74 * al_Peroxide * y[7] * aO_HOBr + Gamma *k!02 * y[28];dfdy[l 1][17] = - k30b * y[l 1] + k31a;dfdyfl 1][1 8] = 0.0;dfdyfl I][19] = k40*y[14];dfdyfl 1][20] = 0.0;dfdyfl 1][21] = 0.0;dfdy[ll][22] = 0.0;dfdyfl 1][23] = 0.0;dfdyfl 1][24] = 0.0;dfdyfl I][25] = k82*y[l];dfdyfll][26] = 0.0;dfdyfl 1][27] = 0.0;dfdyfl 1][28] = Gamma * k!02 * y[16];dfdy[ll][29] = 0.0;dfdy[12][l]=-k33*y[12];dfdy[12][2]=0.0;dfdy[12][3] = 0.0;dfdy[12][4] = k37 * al_HO2 * aO_HOBr * y[16];dfdy[12][5]=0.0;dfdyfl 2] [6] = 0.0;134

dfdy[12][7]=0.0;dfdy[12][8]=0.0;dfdy[12][9] = 0.0;dfdy[12][10]=0.0;dfdy[12][ll] = -k28a*y[12];dfdy[12][12] = - k25b * HYD - k28a * y[l 1] - k33 *y[l]-k34*al_HOBr*y[16];dfdy[12][13] = k25a + k26 * PRT;dfdy[12][14]=k28b;dfdy[12][15]=0.0;dfdy[12][16] = - k34 * y[12] * al_HOBr + k37 *al_HO2 * y[4] * aOJHOBr;dfdy[12][17] = 0.0;dfdy[12][18] = 0.0;dfdy[12][19] = 0.0;dfdy[12][20] = 0.0;dfdy[12][21] = 0.0;dfdy[12][22] = 0.0;dfdy[12][23] = 0.0;dfdy[12][24] = 0.0;dfdy[12][25] = 0.0;dfdy[12][26] = 0.0;dfdy[12][27] = 0.0;dfdy[12][28] = 0.0;dfdy[12][29] = 0.0;dfdy[13][l] = 0.0;dfdy[13][2] = 0.0;dfdy[13][3] = 0.0;dfdy[13][4]=0.0;dfdy[13][5] = 0.0;dfdy[13][6]=k24a*y[ll];dfdy[13][7] = 0.0;dfdy[13][8] = 0.0;dfdy[13][9] = 0.0;dfdy[13][10] = 0.0;dfdy[13][l 1] = k24a * y[6] - k27 * y[13];dfdy[13][12] = k25b * HYD;dfdy[13][13] = - k24b - k25a - k26 * PRT - k27 *dfdy[13][14] = 0.0;dfdy[13][15] = 0.0;dfdy[13][16] = 0.0;dfdy[13][17] = 0.0;dfdy[13][18]=0.0;dfdy[13][19] = 0.0;dfdy[13][20] = 0.0;dfdy[13][21] = 0.0;dfdy[13][22] = 0.0;dfdy[13][23] = 0.0;dfdy[13][24]=0.0;dfdy[13][25] = 0.0;dfdy[13][26] = 0.0;dfdy[13][27]=0.0;dfdy[13][28] = 0.0;dfdy[13][29]=0.0;dfdy[14][l]=0.0;dfdy[14][2] = 0.0;dfdy[14][3]=0.0;dfdy[14][4]=0.0;dfdy[14][5] = 0.0;dfdy[14][6] = 0.0;dfdy[14][7]=0.0;dfdy[14][8] = 0.0;dfdy[14][9]=0.0;dfdy[14][10] = 0.0;dfdy[14][l 1] = k27 * y[13] + k28a * y[12];dfdy[14][12] = k28a*y[ll];dfdy[14][13] = k27*y[ll];dfdy[14][14] = - k28b - 4*k29 * y[14] - k40 *dfdy[14][15] = 0.0;dfdy[14][16] = 0,0;dfdy[14][17] = 0.0;dfdy[14][18] = 0.0;dfdy[14][19] = -k40*y[14];dfdy[14][20] = 0.0;dfdy[14][21] = 0.0;dfdy[14][22] = 0.0;dfdy[14][23]=0.0;dfdy[14][24] = 0.0;dfdy[14][25] = 0.0;dfdy[14][26] = 0.0;dfdy[14][27] = 0.0;dfdy[14][28] = 0.0;dfdy[14][29] = 0.0;dfdy[15][l] =dfdytl5][2] =dfdy[15][3] =dfdy[15][4] =dfdy[15][5] =dfdy[15][6] =dfdy[15][7] =dfdy[15][8] =0.0;0.0;0.0;0.0;0.0;0.0;0.0;0.0;dfdy[15][9] = 0.0;dfdy[15][10]dfdy[15][ll]dfdy[15][12]dfdy[15][13]dfdy[15][14]dfdy[15][15]dfdy[15][16]dfdy[15][17]dfdy[15][18]dfdy[15][19]dfdy[15][20]dfdy[15][21]dfdy[15][22]dfdy[15][23]dfdy[15][24]dfdy[15][25]= 0.0;= k30b*y[17];= 0.0;= 0.0;= 2*k29*y[14];= - k30a;= 0.0;= k30b*y[ll];= 0.0;= 0.0;= 0.0;= 0.0;= 0.0;= 0.0;= 0.0;= 0.0;135

dfdy[15][26] = 0.0;dfdy[15][27] = 0.0;dfdy[15][28] = 0.0;dfdy[15][29] = 0.0;dfdy[16][l] =k20 * y[ll] -k21 * al_HOBr * y[16] -k22*al_HOBr*y[16];dfdy[16][2] = 0.0;dfdy[16][3] = 0.0;dfdy[16][4] = - k37 * al_HO2 * aO_HOBr * y[16];dfdy[16][5]=0.0;dfdy[16][6] = - k35 * al_HOBr * y[16] - k36 *aO_HOBr*y[16];dfdy[16][7] = - k74 * al_Peroxide * aO_HOBr *dfdy[16][8] = 0.0;dfdy[16][9] = - k55 * al_CO3r * al_HOBr * y[16];dfdy[16][10] = 0.0;dfdy[16][ll] =k20 * y[l] - k31b * aO_HOBr * y[16]*PRT;dfdy[16][12] = - k34 * al_HOBr * y[16];dfdy[16][13] = 0.0;dfdy[16][14]=k40*y[19];dfdy[16][15] = 0.0;dfdy[16][16] = - k21 * y[l] * al_HOBr - k22 * y[l]* al_HOBr - k3 Ib * aO_HOBr * PRT * y[l 1] - k34 *y[12] * al_HOBr - k35 * y[6] * al_HOBr - k36 *y[6] * aO_HOBr - k37 * al_HO2 * y[4] * aO_HOBr -k55 * al_CO3r * y[9] * al_HOBr - k74 *al_Peroxide * y[7] * aO_HOBr - k81 * aO_HOBr *al_NH3 * y[24] - k!02 * y[28];dfdy[16][17] = k31a;dfdy[16][18] = 2 * k38 * y[18] + k39 * y[19];dfdy[16][19] = k39 * y[18] + k40 * y[14];dfdy[16][20] = 0.0;dfdy[16][21] = 0.0;dfdy[16][22]=0.0;dfdy[16][23] = 0.0;dfdy[16][24] = - k81 * aO_HOBr * y[16] * al_NH3;dfdy[16][25] = 0.0;dfdy[16][26] = 0.0;dfdy[16][27]=0.0;dfdy[16][28] = - k!02 *dfdy[16][29] = 0.0;dfdy[17][l] = 0.0;dfdy[17][2] = 0.0;dfdy[17][3] = 0.0;dfdy[17][4] = 0.0;dfdy[17][5] = 0.0;dfdy[17][6]=0.0;dfdy[17][7] = 0.0;dfdy[17][8] = 0.0;dfdy[17][9]=0.0;dfdy[17][10] = 0.0;dfdy[17][l 1] = - k30b * y[17] + k31b * aO_HOBr *y[16]*PRT;dfdy[17][12] = 0.0;dfdy[17][13]= 0.0;dfdy[17][14] = 0.0;dfdy[17][15] = k30a;dfdy[17][16] = k31b * aO_HOBr * PRT * y[l 1];dfdy[17][17] = - k30b * y[l 1] - k31a;dfdy[17][18] = 0.0;dfdy[17][19] = 0.0;dfdy[17][20] = 0.0;dfdy[17][21] = 0.0;dfdy[17][22] = 0.0;dfdy[17][23] = 0.0;dfdy[17][24] = 0.0;dfdy[17][25] = 0.0;dfdy[17][26] = 0.0;dfdy[17][27] = 0.0;dfdy[17][28] = 0.0;dfdy[17][29] = 0.0;dfdy[18][l]=k33*y[12];dfdy[18][2]=0.0;dfdy[18][3]=0.0;dfdy[18][4]=0.0;dfdy[18][5]=0.0;dfdy[18][6] = k35 * al_HOBr * y[16] + k36 *aO_HOBr*y[16];dfdy[18][7] = 0.0;dfdy[18][8]=0.0;dfdy[18][9] = k55 * al_CO3r * al_HOBr * y[16];dfdy[18][10] = 0.0;dfdy[18][ll] = 0.0;dfdy[18][12] = k33 * y[l] + k34 * al_HOBr * y[16];dfdy[18][13] = 0.0;dfdy[18][14] = k40*y[19];dfdy[18][15] = 0.0;dfdy[18][16] = k34 * y[12] * al_HOBr + k35 * y[6]* al_HOBr + k36 * y[6] * aO_HOBr + k55 *al_C03r * y[9] * al_HOBr;dfdy[18][17] = 0.0;dfdy[18][18] = - 4 * k38 * y[18] - k39 * y[19];dfdy[18][19] = - k39 * y[18] + k40 * y[14];dfdy[18][20] = 0.0;dfdy[18][21] = 0.0;dfdy[18][22] = 0.0;dfdy[18][23] = 0.0;dfdy[18][24] = 0.0;dfdy[18][25] = 0.0;dfdy[18][26] = 0.0;dfdy[18][27] = 0.0;dfdy[18][28] = 0.0;dfdy[18][29] = 0.0;dfdy[19][l] = k22 * al_HOBr * y[16] - k23 * y[19];136

dfdy[19][2]=0.0;dfdy[19][3] = 0.0;dfdy[19][4]=0.0;dfdy[19][5]=0.0;dfdy[19][6] = -k41*y[19];dfdy[19][7]=0.0;dfdy[19][8] = 0.0;dfdy[19][9] = - k56 * al_CO3r * y[19];dfdy[19][10] = 0.0;dfdy[19][ll] = 0.0;dfdy[19][12] = 0.0;dfdy[19][13] = 0.0;dfdy[19][14] = -k40*y[19];dfdy[19][15]=0.0;dfdy[19][16] = k22 * y[l] * alJJOBr;dfdy[19][17] = 0.0;dfdy[19][18] = 2 * k38 * y[18] - k39 * y[19];dfdy[19][19] = - k23 * y[l] - k39 * y[18] - k40 *y[14] - k41 * y[6] - k56 * al_CO3r * y[9];dfdy[19][20] = 0.0;dfdy[19][21J=k44*HYD;dfdy[19][22]=0.0;dfdy[19][23] = 0.0;dfdy[19][24] = 0.0;dfdy[19][25]=0.0;dfdy[19][26] = 0.0;dfdy[19][27] = 0.0;dfdy[19][28] = 0.0;dfdy[19][29]=0.0;dfdy[20][l] = 0.0;dfdy[20][2] = 0.0;dfdy[20][3] = 0.0;dfdy[20][4] = 0.0;dfdy[20][5] = 0.0;dfdy[20][6] = k41 * y[19] - k42 * y[20];dfdy[20][7] = 0.0;dfdy[20][8] = 0.0;dfdy[20][9] = k56 * al_CO3r * y[19];dfdy[20][10] = 0.0;dfdy[20][ll] = 0.0;dfdy[20][12] = 0.0;dfdy[20][13]=0.0;dfdy[20][14]=0.0;dfdy[20][15] = 0.0;dfdy[20][16] = 0.0;dfdy[20][17]=0.0;dfdy[20][18]=k39*y[19];dfdy[20][19] = k39 * y[18] + k41 * y[6] +k56 *al_C03r * y[9];dfdy[20][20] = - k42 * y[6] - 4*k43a * y[20];dfdy[20][21] = 2*k43b;dfdy[20][22] = 0.0;dfdy[20][23] = 0.0;dfdy[20][24] = 0.0;dfdy[20][25] = 0.0;dfdy[20][26]=0.0;dfdy[20][27] = 0.0;dfdy[20][28] = 0.0;dfdy[20][29]=0.0;dfdy[2 !][!]= 0.0;dfdy[21][2] = 0.0;dfdy[21][3] = 0.0;dfdy[21][4] = 0.0;dfdy[21][5]=0.0;dfdy[21][6]=0.0;dfdy[21][7]=0.0;dfdy[21][8]=0.0;dfdy[21][9] = 0.0;dfdy[21][10] = 0.0;dfdy[21][ll] = 0.0;dfdy[21][12] = 0.0;dfdy[21][13] = 0.0;dfdy[21][14] = 0.0;dfdy[21][15] = 0.0;dfdy[21][16] = 0.0;dfdy[21][17] = 0.0;dfdy[21][18] = 0.0;dfdy[21][19] = 0.0;dfdy[21][20] = 2 * k43a * y[20];dfdy[21][21] = - k43b - k44 * HYD;dfdy[21][22]=0.0;dfdy[21][23] = 0.0;dfdy[21][24] = 0.0;dfdy[21][25] = 0.0;dfdy[21][26] = 0.0;dfdy[21][27]=0.0;dfdy[21][28] = 0.0;dfdy[21][29] = 0.0;dfdy[22][l] = k23*y[19];dfdy[22][2] = 0.0;dfdy[22][3] = 0.0;dfdy[22][4] = 0.0;dfdy[22][5] = 0.0;dfdy[22][6] = k42* - y[20];dfdy[22][7] = 0.0;dfdy[22][8] = 0.0;dfdy[22][9] = 0.0;dfdy[22][10]dfdy[22][ll]dfdy[22][12]dfdy[22][13]dfdy[22][14]dfdy[22][15]dfdy[22][16]dfdy[22][17]dfdy[22][18]dfdy[22][19]dfdy[22][20]dfdy[22][21]= 0.0;= 0.0;= 0.0;= 0.0;= 0.0;= 0.0;= 0.0;= 0.0;= 0.0;= k23*y[l];= k42*y[6];= k44*HYD;137

dfdy[22][22] = 0.0;dfdy[22][23] = 0.0;dfdy[22][24] = 0.0;dfdy[22][25] = 0.0;dfdy[22][26] = 0.0;dfdy[22][27] = 0.0;dfdy[22][28] = 0.0;dfdy[22][29] = 0.0;dfdy[23][l] =dfdy[23][2] =dfdy[23][3] =dfdy[23][4] =dfdy[23][5] =dfdy[23][6] =dfdy[23][7] =dfdy[23][8] =dfdy[23][9] =dfdy[23][10]dfdy[23][ll]dfdy[23][12]dfdy[23][13]dfdy[23][14]dfdy[23][15]dfdy[23][16]dfdy[23][17]dfdy[23][18]dfdy[23][19]dfdy[23][20]dfdy[23][21]dfdy[23][22]dfdy[23][23]dfdy[23][24]dfdy[23][25]dfdy[23][26]dfdy[23][27]dfdy[23][28]dfdy[23][29]0.0;0.0;0.0;0.0;0.0;- k90 * y[23];0.0;0.0;0.0;= 0.0;= 0.0;= 0.0;= 0.0;= 0.0;= 0.0;= 0.0;= 0.0;= 0.0;= 0.0;= 0.0;= 0.0;= 0.0;= - k90 * y[6];= 0.0;= 0.0;= 0.0;= 0.0;= 0.0;= 0.0;dfdy[24][l]=0.0;dfdy[24][2] = 0.0;dfdy[24][3] = 0.0;dfdy[24][4] = 0.0;dfdy[24][5] = 0.0;dfdy[24][6]=0.0;dfdy[24][7] = 0.0;dfdy[24][8]=0.0;dfdy[24][9] = 0.0;dfdy[24][10] = 0.0;dfdy[24][ll]=0.0;dfdy[24][12]=0.0;dfdy[24][13] = 0.0;dfdy[24][14] = 0.0;dfdy[24][15] = 0.0;dfdy[24][16] = - k81 * aO_HOBr * al_NH3 * y[24];dfdy[24][17] = 0.0;dfdy[24][18] = 0.0;dfdy[24][19] = 0.0;dfdy[24][20] = 0.0;dfdy[24][21] = 0.0;dfdy[24][22] = 0.0;dfdy[24][23] = 0.0;dfdy[24][24] = - k81 * aO_HOBr * y[16] * al_NH3;dfdy[24][25] = 0.0;dfdy[24][26] = 0.0;dfdy[24][27] = 0.0;dfdy[24][28] = 0.0;dfdy[24][29] = 0.0;dfdy[25][l]=-k82*y[25];dfdy[25][2]=0.0;dfdy[25][3]=0.0;dfdy[25][4]=0.0;dfdy[25][5]=0.0;dfdy[25][6]=0.0;dfdy[25][7]=0.0;dfdy[25][8]=0.0;dfdy[25][9]=0.0;dfdy[25][10] = 0.0;dfdy[25][ll] = 0.0;dfdy[25][12]=0.0;dfdy[25][13]=0.0;dfdy[25][14]=0.0;dfdy[25][15] = 0.0;dfdy[25][16] = k81 * aO_HOBr * al_NH3 * y[24];dfdy[25][17]=0.0;dfdy[25][18]=0.0;dfdy[25][19] = 0.0;dfdy[25][20] = 0.0;dfdy[25][21]=0.0;dfdy[25][22]=0.0;dfdy[25][23] = 0.0;dfdy[25][24] = k81 * aO_HOBr * y[16] * al_NH3;dfdy[25][25]=-k82*y[l];dfdy[25][26] = 0.0;dfdy[25][27] = 0.0;dfdy[25][28] = 0.0;dfdy[25][29] = 0.0;dfdy[26][l]=-klOO*y[26];dfdy[26][2] = 0.0;dfdy[26][3]=0.0;dfdy[26][4] = 0.0;dfdy[26][5] = 0.0;dfdy[26][6]=0.0;dfdy[26][7] = 0.0;dfdy[26][8]=0.0;dfdy[26][9]=0.0;dfdy[26][10] = 0.0;dfdy[26][ll]=0.0;dfdy[26][12]=0.0;dfdy[26][13]=0.0;138

dfdy[26][14]=0.0;dfdy[26][15] = 0.0;dfdy[26][16]=0.0;dfdy[26][17] = 0.0;dfdy[26][18]=0.0;dfdy[26][19] = 0.0;dfdy[26][20] = 0.0;dfdy[26][21]=0.0; 'dfdy[26][22] = 0.0;dfdy[26][23] = 0.0;dfdy[26][24] = 0.0;dfdy[26][25] = 0.0;dfdy[26][26] = - klOO *dfdy[26][27] = 0.0;dfdy[26][28] = 0.0;dfdy[26][29] = 0.0;dfdy[27][l] = 0.0;dfdy[27][2] = 0.0;dfdy[27][3] = 0.0;dfdy[27][4] = 0.0;dfdy[27][5] = 0.0;dfdy[27][6] = -klOl *y[27];dfdy[27][7] = 0.0;dfdy[27][8] = 0.0;dfdy[27][9] = 0.0;dfdy[27][10] = 0.0;dfdy[27][ll] = 0.0;dfdy[27][12] = 0.0;dfdy[27][13] = 0.0;dfdyf27][14] = 0.0;dfdy[27][15] = 0.0;dfdy[27][16] = 0.0;dfdy[27][17] = 0.0;dfdy[27][18] = 0.0;dfdy[27][19] = 0.0;dfdy[27][20] = 0.0;dfdy[27][21] = 0.0;dfdy[27][22] = 0.0;dfdy[27][23] = 0.0;dfdy[27][24] = 0.0;dfdy[27][25] = 0.0;dfdy[27][26] = 0.0;dfdy[27][27] = -k!01*y[6];dfdy[27][28] = 0.0;dfdy[27][29] = 0.0;dfdy[28][l]=0.0;dfdy[28][2] = 0.0;dfdy[28][3] = 0.0;dfdy[28][4]=0.0;dfdy[28][5] = 0,0;dfdy[28][6] = 0.0;dfdy[28][7] = 0.0;dfdy[28][8]=0.0;dfdy[28][9] = 0.0;dfdy[28][10]=0.0;dfdy[28][ll] = 0.0;dfdy[28][12] = 0.0;dfdy[28][13] = 0.0;dfdy[28][14] = 0.0;dfdy[28][15] = 0.0;dfdy[28][16] = -k!02*y[28];dfdy[28][17] = 0.0;dfdy[28][18] = 0.0;dfdy[28][19] = 0.0;dfdy[28][20]=0.0;dfdy[28][21] = 0.0;dfdy[28][22] = 0.0;dfdy[28][23] = 0.0;dfdy[28][24] = 0.0;dfdy[28][25]=0.0;dfdy[28][26] = 0.0;dfdy[28][27] = 0.0;dfdy[28][28] = -k!02*y[16];dfdy[28][29] = 0.0;dfdy[29][l]=0.0;dfdy[29][2]=0.0;dfdy[29][3]=0.0;dfdy[29][4]=0.0;dfdy[29][5] = 0.0;dfdy[29][6] = 0.0;dfdy[29][7] = 0.0;dfdy[29][8]=0.0;dfdy[29][9] = 0.0;dfdy[29][10] = 0.0;dfdy[29][ll] = 0.0;dfdy[29][12]=0.0;dfdy[29][13] = 0.0;dfdy[29][14] = 0.0;dfdy[29][15] = 0.0;dfdy[29][16] = (1-Gamma) * k!02 * y[28];dfdy[29][17]=0.0;dfdy[29][18] = 0.0;dfdy[29][19] = 0.0;dfdy[29][20] = 0.0;dfdy[29][21] = 0.0;dfdy[29][22]=0.0;dfdy[29][23]=0.0;dfdy[29][24] = 0.0;dfdy[29][25] =- 0.0;dfdy[29][26] = 0.0;dfdy[29][27] = 0.0;dfdy[29][28] = (1-Gamma) * k!02 * y[16];dfdy[29][29] = 0.0;/*********#*****#************************/// Calculation of Differential Steps. Kinetics Routine139

void derivs(double x, double y[], double dydx[j){//printf ("\n derivs");nrhs-H-;/*Rate Equations// Ozone decompositiondouble Rl = kl *y[l] *HYD;// kl[O3][OH-]double R3 = k3 * y[l] * al_HO2 * y[4];//k3[O3][O2-]double R5 = k5 * aO_HO3 *y[2];/7 k3[HO3]double R6 = k6 * y[l] * y[6];// k6[HO][O3]double R7 = k7 * y[6] * y[6];// k7[HO][HO]double R8 = k8 * y[6] * al_HO2 * y[4];//k8[HO][O2-]double R9 = k9 * y[6] * aO_HO3 * y[2];//k9[HO][H03]double RIO = klO * al_HO2 * y[4] * aO_HO3 *y[2];// klO[02-][H03]double Rl 1 = kl 1 * aO_HO3 * y[2] * aO_HO3 *kll[H03][H03]// Bromate Formationdouble R20 = k20 * y[l] * y[lI];// k20[O3][Br-]double R21 = k21 * y[l] * al_HOBr * y[16];//k21[03][OBr-]double R22 = k22 * y[l] * al_HOBr * y[16];//k22[O3][OBr-]double R23 = k23 * y[l] * y[19];// k23[O3][BrO2-]double R24a = k24a * y[6] * y[l I];// k24a[OH][Br-]double R24b = k24b * y[13];// k24b[BrOH-]double R25a = k25a * y[13];// k25a[BrOH-jdouble R25b = k25b * y[ 12] * HYD;//k25b[Br][OH-]double R26 = k26 * y[13] * PRT;// k26[BrOH-][H+]double R27 = k27 * y[13] * y[l 1]; // k27[BrOHdoubleR28a = k28a * y[12] * y[l I];// k28a[Br][Br-]double R28b = Jc28b * y[14];// k28b[Br2-]double R29 = k29 * y[14] * y[14];// k29[Br2-][Br2-]double R30a = k30a * y[15];// k30a[Br3-]double R30b = k30b * y[17] * y[lI];//k30b[Br2][Br-]double R31a = k31a * y[17];// k31a[Br2][H2O]double R31b = k31b * aO_HOBr * y[16] * PRT *y[ll];// k31b[HOBr][Br-][H+]double R33 =k33 * y[l] * y[12];// k33[O3][Br]double R34 = k34 * y[12] * al_HOBr * y[16];//k34[Br][OBr-]double R35 = k35 * y[6] * al_HOBr * y[16];//k35[OH][OBr-]double R36 = k36 * y[6] * aOJHOBr * y[16]; //k36[OH][HOBr]double R37 = k37 * al_HO2 * y[4] * aO_HOBr *y[16];// k37[O2-][HOBr]double R38 = k38 * y[18] * y[18];//k38[BrO][BrO][H20]double R39 = k39 * y[18] * y[19];//k39[BrO][BrO2-]double R40 = k40 * y[14] * y[19];// k40[Br2-][Br02-]double R41 = k41 * y[6] * y[19];// k41[OH][BrO2-]double R42 = k42 * y[6] * y[20];// k42[OH][BrO2]double R43a = k43a * y[20] * y[20];//k43a[Br02][Br02]double R43b = k43b * y[21];// k43b[Br2O4]double R44 = k44 * y[21] * HYD;//k44[Br2O4][OH-]// Carbonatedouble R53 = k53 * al_CO3 * y[8] * y[6];//k53[HCO3-][OH]double R54 = k54 * a2_CO3 * y[8] * y[6];//k54[C032-][OH]double R55 = k55 * al_CO3r * y[9] * al_HOBr *y[16];// k55[CO3-][OBr-]double R56 = k56 * al_CO3r * y[9] * y[19]; //k56[CO3-][BrO2-]// Phosphatedouble R63 = k63 * y[6] * al_PO4 * y[10];//k65[OH][H2PO4-]double R64 = k64 * y[6] * a2_PO4 * y[10];//k66[OH][HPO42-]// Hydrogen Peroxidedouble R71 = k71 * y[l] * al_Peroxide * y[7];//k71[O3][HO2-]double R72 = k72 * aO_Peroxide * y[7] * y[6];//k72[H2O2][OH]double R73 = k73 * al_Peroxide * y[7] * y[6];//k73[HO2-][OH]double R74 = k74 * al_Peroxide * y[7] * aO_HOBr *];// k74[HO2-][HOBr]// Ammoniadouble R81 = k81 * aO_HOBr * y[16] * al_NH3 *y[24];// k91[HOBr][NH3]double R82 = k82 * y[l] * y[25];// k92[NH2Br][O3]// Radical Scavengerdouble R90 = k90 * y[23] * y[6];// k95[t-BuOH][OH]140

Natural Organic Matterdouble R100 = klOO * y[26] * y[l];//klOO[NOMl][O3]double R101 = klOl * y[27] * y[6];//k!01[NOM2][OH]double R102 = k!02 * y[28] * y[16];//k!02[NOM3][HOBr]tot/*Differential Equationsdydx[l] = - Rl - R3 - R6 - R20 - R21 -R22 - R23 -R33-R71-3*R82-R100;dydx[2] = R3 - R5 - R9 - RIO - 2*R1 1 + Alpha *R100;dydx[3] = 0.0;dydx[4] = 2*R1 - R3 + R6 - R8 - RIO - R37 + R71 +R72 + R73 + Beta*R101;dydx[5] = 0.0;dydx[6] = R5 - R6 - 2*R7 - R8 - R9 - R24a + R24b -R35 - R36 - R41 - R42 - R53 - R54 - R63 - R64 +R71 - R72 - R73 - R90 - R101;dydx[7] = R7 + R9 + Rl 1 - R71 - R72 - R73 - R74;dydx[8] = - R53 - R54 + R55 + R56;dydx[9] = R53 + R54 - R55 - R56;dydx[10] = -R63-R64;dydx[l 1] = - R20 + R21 - R24a + R24b - R27 - R28a+ R28b + R29 + R30a - R30b + R31a - R3 Ib + R34+ R40 + R74 + R82 + Gamma * R102;dydx[12] = R25a - R25b + R26 - R28a + R28b - R33- R34 + R37;dydx[13] = R24a - R24b - R25a + R25b - R26 - R27;dydx[14] = R27 + R28a - R28b - 2*R29 - R40;dydx[15] = R29 - R30a + R30b;dydx[16] = R20 - R21 - R22 + R31a - R31b - R34 -R35 - R36 - R37 + R38 + R39 + R40 - R55 - R74 -R81-R102;dydx[17] = R30a - R30b - R31a + R31b;dydx[18] = R33 + R34 + R35 + R36 - 2*R38 - R39 +R40 + R55;dydx[19] = R22 - R23 + R38 - R39 - R40 - R41 +R44 - R56;dydx[20] = R39 + R41 - R42 - 2*R43a + 2*R43b+R56;dydx[21] = R43a - R43b - R44;dydx[22] = R23 + R42 + R44;dydx[23] = - R90;dydx[24] = -R81 ;dydx[25]=R81-R82;dydx[26] = - R100;dydx[27] = -R101;dydx[28] = -R102;dydx[29] = (1-Gamma) *.R102;3. Solver routines for bromate formation and Cryptosporidiwn parvum inactivation in AxialDispersion Model. These routines are utilized by main function that should be programmedfor the specific purposes. Main functions for different modeling were not included_____/****************************************/// pinvs(ic3,ic4,j5,j9Jcl,kl,c,s) Called from solvde/#****#**********#******************#****/void pinvs(int iel, int ie2, int jel, int jsf, int jcl, int k,double ***c, double **s){intjsljpivjpje2jcoff,j,irow,ipiv,id,icoff,i,*indxr;double pivinv,piv,dum,big,*pscl;indxr=ivector(ie 1 ,ie2);pscl=vector(ie 1 ,ie2);je2=jel+ie2-iel;jsl=je2+l;for(i=iel;i

indxr[ipiv]=;jpiv;pivinv=l .0/s[ipiv][jpiv];for (j=Jel;j

inticl=l;int ic2=ne-nb;intic3=ic2+l;int ic4=ne;intjcl=l;intjcf=ic3;for(it=l;it

elseif(k>k2) {if (current=l) {for(i=l;i

double R24a = k24a * 0.5*(y[6][k]+y[6][k-l]) *0.5*(y[ll][k]+y[ll][k-l]);// k24a[OH][Br-]double R24b = k24b * 0.5*(y[13][k]+y[13][k-l]);//k24b[BrOH-]double R25a = k25a * 0.5*(y[13][k]+y[13][k-l]);//k25a[BrOH-Jdouble R25b = k25b * 0.5*(y[12][k]+y[12][k-l]) *HYD;// k25b[Br][OH-]double R26 = k26 * 0.5*(y[13][k]+y[13][k-l]) *PRT;// k26[BrOH-][H+]double R27 = k27 * 0.5*(y[13][k]+y[13][k-l]) *0.5*(y[ll][k]+y[ll][k-l]); // k27[BrOH-][Br-]double R28a = k28a * 0.5*(y[12][k]+y[12][k-l]) *0.5*(y[l l][k]+y[l l][k-l]);// k28a[Br][Br-]double R28b = k28b * 0.5*(y[14][k]+y[14][k-l]);//k28b[Br2-]double R29 = k29 * 0.5*(y[14][k]+y[14][k-l]) *0.5*(y[14][k]+y[14][k-l]);// k29[Br2-][Br2-]double R30a = k30a * 0.5*(y[15][k]+y[15][k-l]);//k30a[Br3-]double R30b = k30b * 0.5*(y[17][k]+y[17][k-l]) *0.5*(y[l l][k]+y[l l][k-l]);// k30b[Br2][Br-]double R3la = k31a * 0.5*(y[17][k]+y[17][k-l]);//k31a[Br2][H20]double R31b = k31b * aO_HOBr *0.5*(y[16][k]+y[16][k-l]) * PRT *0.5*(y[ll][k]+y[ll][k-l]);// k31b[HOBr][Br-][H+]double R33 =k33 * 0.5*(y[l][k]+y[l][k-l]) *0.5*(y[12][k]+y[12][k-l]);//k33[03][Br]double R34 = k34 * 0.5*(y[12][k]+y[12][k-l]) *al_HOBr * 0.5*(y[16][k]+y[16][k-l]);//k34[Br][OBr-]double R35 =k35 * 0.5*(y[6][k]+y[6][k-l]) *al_HOBr * 0.5*(y[16][k]+y[16][k-l]);//k35[OH][OBr-]double R36 = k36 * 0.5*(y[6][k]+y[6][k-l]) *aO_HOBr * 0.5*(y[16][k]+y[16][k-l]); //k36[OH][HOBr]double R37 = k37 * al_HO2 * 0.5*(y[4][k]+y[4][k-1]) * aO_HOBr * 0.5*(y[16][k]+y[16][k-l]);//k37[02-][HOBr]double R38 = k38 * 0.5*(y[18][k]+y[18][k-l]) *0.5*(y[18][k]+y[18][k-l]);// k38[BrO][BrO][H2O]double R39 =k39 * 0.5*(y[18][k]+y[18][k-l]) *0.5*(y[19][k]+y[19][k-l]);// k39[BrO][BrO2-]double R40 =k40 * 0.5*(y[14][k]+y[14][k-l]) *0-5*(y[19][k]+y[19][k-l]);// k40[Br2-][BrO2-]double R41 =k41 * 0.5*(y[6][k]+y[6][k-l]) *0.5*(y[19][k]+y[19][k-l]);// k41[OH][BrO2-]double R42 = k42 * 0.5*(y[6][k]+y[6][k-l]) *0.5*(y[20][k]+y[20][k-l]);// k42[OH][BrO2]double R43a = k43a * 0.5*(y[20][k]+y[20][k-l]) *0.5*(y[20][k]+y[20][k-l]);// k43a[BrO2][BrO2]double R43b = k43b * 0.5*(y[21][k]+y[21][k-l]);//k43b[Br2O4]double R44 = k44 * 0.5*(y[21][k]+y[21][k-l]) *HYD;// k44[Br2O4][OH-]// Carbonatedouble R53 =k53 * al_CO3 * 0.5*(y[8][k]+y[8][k-1]) * 0.5*(y[6][k]+y[6][k-l]);// k53[HCO3-][OH]double R54 = k54 * a2_CO3 * 0.5*(y[8][k]+y[8][k-1]) * 0.5*(y[6][k]+y[6][k-l]);// k54[CO32-][OH]double R55 = k55 * al_CO3r * 0.5*(y[9][k]+y[9][k-1]) * al_HOBr * 0.5*(y[16][k]+y[16][k-l]);//k55[C03-][OBr-]double R56 = k56 * al_CO3r * 0.5*(y[9][k]+y[9][k-1]) * 0.5*(y[19][k]+y[19][k-l]); // k56[CO3-][Br02-]// Phosphatedouble R63 = k63 * 0.5*(y[6][k]+y[6][k-l]) *al_PO4 * 0.5*(y[10][k]+y[10][k-l]);//k65[OH][H2PO4-]double R64 = k64 * 0.5*(y[6][k]+y[6][k-l]) *a2_PO4 * 0.5*(y[10][k]+y[10][k-l]);//k66[OH][HPO42-]// Hydrogen Peroxidedouble R71 = k71 * 0.5*(y[l][k]+y[l][k-l]) *al_Peroxide * 0.5*(y[7][k]+y[7][k-l]);//k71[03][H02-]double R72 = k72 * aO_Peroxide *0.5*(y[7][k]+y[7][k-l]) * 0.5*(y[6][k]+y[6][k-l]);//k72[H202][OH]double R73 = k73 * al_Peroxide *0.5*(y[7][k]+y[7][k-l]) * 0.5*(y[6][k]+y[6][k-l]);//k73[HO2-][OH]double R74 = k74 * al_Peroxide *0.5*(y[7][k]+y[7][k-l]) * aO_HOBr *]);// k74[HO2-][HOBr]// Ammoniadouble R81 = k81 * aO_HOBr *0.5*(y[16][k]+y[16][k-l]) * al_NH3 *0.5*(y[24][k]+y[24][k-l]);// k91[HOBr][NH3]double R82 = k82 * 0.5*(y[l][k]+y[l][k-l]) *0.5*(y[25][k]+y[25][k-l]);// k92[NH2Br][O3]// Radical Scavengerdouble R90 = k90 * 0.5*(y[23][k]+y[23][k-l]) *0.5*(y[6][k]+y[6][k-l]);// k95[t-BuOH][OH]// Natural Organic Matterdouble R100 = klOO * 0.5*(y[26][k]+y[26][k-l]) *0.5*(y[l][k]+y[l][k-l]);// klOO[NOMl][O3]double R101 =k!01 * 0.5*(y[27][k]+y[27][k-l]) *0.5*(y[6][k]+y[6][k-l]);// k!01[NOM2][OH]double R102 = k!02 * 0.5*(y[28][k]+y[28][k-l]) *]);// k!02[NOM3][HOBr]tot145

C. parvum Inactivationdouble RI1 =kNl * 0.5*(y[l][k]+y[l][k-l]) *0.5*(y[3][k]+y[3][k-l]);double RI2 = kN2 * 0.5*(y[l][k]+y[l][k-l]) *0.5*(y[5][k]+y[5][k-l]);// Mass Transferdouble Rka = ka * 0.5*(y[30][k]+y[30][k-l]) / m - ka- 0.5*(y[l][k]+y[l][k-l]);for(n=l;n

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ABBREVIATIONSACDADRAMAAMWANNAPHAAWWAAwwaRFBAG°CCCDCGEC,cmcm" 1CRWCSTRCTALL-tlOCT ALL-t50CTswTR-tlOCTsWTR-t50CUWACVdD/DBPDALDBFDO 3DOC^initialAUVA200-400AUVA254South Bay Aqueduct, Fremont, Californiaaxial dispersion reactorLake Meredith and Ogallala Aquifer mix, Amarillo, Texasapparent molecular weightHuron River, Ann Arbor, MichiganAmerican Public Health AssociationAmerican Water Works AssociationAwwa Research Foundationbiological activated carbondegrees CelsiusSacramento/San Joaquin Delta, Concord, CaliforniaMarne River, Paris, Franceconcentration of chemical speciescentimeterinverse centimeterColorado River, La Verne, Californiacontinuous-stirred tank reactoran "all cells" approach where CT credit for the first cell (effluent ozoneresidual multiplied by the first cell tio) was added to the CTswTR-tiocalculated by summing the tso multiplied by the effluent ozone residual foreach cell in the contactorCT required to overcome the initial time lagconventional CT using tio contact time times and effluent ozone residualfor each cell of the ozone contactor excluding the first cellusing tso (HRT) instead of tio for the corresponding contact time for eachcell excluding the first, multiplied by the corresponding cell's effluentozone residualCalifornia Urban Water Agenciescoefficient of variationdispersion numberDisinfectants and Disinfection By-ProductsTrinity River - Elm Fork, Dallas, Texasdisinfection by-productdissolved ozone residualdissolved organic carbonrepresents the amount of ozone loss during this phase of the reaction andreflects a "pseudo" zero-order reactiondifferential ultraviolet absorbance spectra between 200 and 400nanometersdifferential ultraviolet absorbance at 254 nanometers153

ECEUFDfiFPGACHBrHOBrHOUHPIHPLCHPOHRTIOAkKkJ/molkNEuropean CommunityEuropean Unionfraction of dissolved organic carbonoverall rate function corresponding to the relevant chemical reactionsformation potentialgranular activated carbonhydrogen bromidehypobromous acidLake Houston, Houston, Texashydrophilichigh performance liquid chromatographyhydrophobichydraulic residence timeInternational Ozone Associationexperimentally derived first-order rate constant for ozone decayslope coefficientkilojoule per molepseudo first-order inactivation rate constantL/mg-mL/minLAWLT2ESWTRmMM/DBPMCLMCLGmg NH3-N/Lmg-min/Lmg/Lmg/L/minmg-C/Lmg-CaCO3/Lmg-DOC/Lmg-Os/LminmLmL/minliter per milligram per meterliter per minuteLos Angeles Aqueduct, Los Angeles, CaliforniaLong-Term 2 Enhanced Surface Water Treatment RulemetermolarMicrobial/Disinfection By-Productmaximum contaminant levelmaximum contaminant level goalmilligram ammonia as nitrogen per litermilligram minute per litermilligram per litermilligram per liter per minutemilligram of carbon per litermilligram calcium carbonate per litermilligram dissolved organic carbon per litermilligram ozone per literminutemillilitermilliliter per minute154

mMMRLMWu,mug/LN/NONJAnmNOM•OHOEOTTPACPFRPQLpsiPSSQAQCSACSECsec" 1SPWSUVASWTRttiotsoTOBrTOCTPI6UCUIUPUSEPAUTmillimolarminimum reporting levelmolecular weightmicrometermicrogram per litersurvival ratiolag phase factorDelaware River, New Jerseynanometernatural organic matterhydroxyl radicalozone exposureOttawa River, Ottawa, CanadaProject Advisory Committeeplug-flow reactorpractical quantification limitpounds per square inchpolystyrene sulfonatequality assurancequality controlSacramento River, Californiasize exclusion chromatographyState Project, La Verne, Californiaspecific ultraviolet absorbancesurface water treatment ruletimetime for 10 percent of the total mass of tracer to exit the reactortime for 50 percent of the total mass of tracer to exit the reactortotal organic bromidetotal organic carbontransphilichydraulic residence time in the chamberUniversity of ColoradoUniversity of IllinoisUniversity of PoitiersUnited States Environmental Protection AgencyUniversity of Toronto155

UV ultravioletUV200-300 ultraviolet absrobance between 200 and 300 nanometersUV254 ultraviolet absorbance at 254 nanonmetersUVA ultraviolet absorbanceWEF Water Environment FederationWPB Floridian Aquifer, West Palm Beach, FloridaWTP water treatment plantz normalized downward distance from the water surface156

AWWAResearchFoundationkm Advancing the Sderm of Water*6666 W. Quincy Avenue, Denver, CO 80235(303)347-61001P-4C-90866-10/01-CM