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Effectiveness of Ceramic Filtration for Drinking Water Treatment in Cambodia

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Effectiveness of Ceramic Filtration for Drinking Water Treatment in Cambodia View metadata, citation and similar papers at core.ac.uk brought to you by CORE provided by Carolina Digital Repository EFFECTIVENESS OF CERAMIC FILTRATION FOR DRINKING WATER TREATMENT IN CAMBODIA Joseph Mark Brown A dissertation submitted to the faculty of the University of North Carolina at Chapel Hill in partial fulfillment of the requirements for the degree of Doctor of Philosophy in the Department of Environmental Sciences and Engineering. Chapel Hill 2007 Approved byyyyyy Mark D. Sobsey, Ph.D. Michael D. Aitken, Ph.D. Francis A. DiGiano, Ph.D. Dana Loomis, Ph. D. David Weber, M.D. © 2007 Joseph Mark Brown ALL RIGHTS RESERVED ii ABSTRACT JOSEPH MARK BROWN: EFFECTIVENESS OF CERAMIC FILTRATION FOR DRINKING WATER TREATMENT IN CAMBODIA (Under the direction of Mark D. Sobsey, Ph.D.) For the estimated 66% of Cambodians without access to improved drinking water sources and the potentially much greater percentage without consistent access to microbiologically safe water, point-of-use water treatment coupled with appropriate storage to prevent recontamination is a promising option for securing access to safe drinking water. The ceramic water purifier (CWP) is an emerging point-of-use water treatment technology that is made locally in Cambodia and in several other developing countries based on a design originally developed in Latin America in the 1980s. Despite the filter's increasingly widespread promotion and implementation as a public health intervention within Cambodia and worldwide, its effectiveness in reducing waterborne microbes and diarrheal disease in users has not been adequately characterized. This dissertation examines: (i) the microbiological effectiveness of locally produced ceramic filters in Cambodia against bacterial and viral surrogates in the laboratory and in field use; (ii) the health impacts of the CWP and a modified CWP in a randomized, controlled trial in a rural/peri-urban village; and (iii) the continued use, microbiological effectiveness, and sustained health impacts of the CWP after up to 44 months in household use in three provinces of Cambodia. iii Results indicate filters as currently produced do reduce microbial indicators in drinking water and contribute to the reduction of diarrheal disease in users. Key findings were: (i) CWPs reduced E. coli up to 99.9999%, with mean reductions of approximately 99% in both laboratory and field testing; (ii) CWPs reduced MS2, a viral surrogate, by a mean 90-99% in laboratory testing; (iii) use of the CWP reduced diarrheal disease outcomes by approximately 40% in users versus non-users, after controlling for clustering within households and within individuals over time in a randomized, controlled trial; (iv) filters maintained effectiveness over long periods, up to 44 months in field use; (v) declining use of the CWPs after implementation was observed due to breakages of the ceramic filter elements coupled with limited availability of replacement parts in communities; and (vi) CWPs in field use were susceptible to recontamination through improper handling practices. iv I am forever indebted to my longsuffering bride, my wise and patient mentors, my generous benefactors and enablers, my steadfast friends and family, and my loyal dogs. v TABLE OF CONTENTS LIST OF TABLES………………………………………………………………... ix LIST OF FIGURES………………………………………………………………. xii LIST OF ABBREVIATIONS…………………………………………………….. xvi CHAPTER 1: INTRODUCTION AND OBJECTIVES…………………………. 1 1.1 Introduction……………………………………………………………….. 1 1.2 Objectives…………………………………………………………………. 3 1.3 References………………………………………………………………… 9 CHAPTER 2: LITERATURE REVIEW………………………………………… 10 2.1 Introduction……………………………………………………………….. 10 2.2 Summits, targets, and initiatives………………………………………….. 11 2.3 Waterborne disease……………………………………………………….. 13 2.4 Access to safe water………………………………………………………. 19 2.5 Point-of-use water treatment interventions……………………………….. 20 2.6 Ceramic filters for drinking water treatment……………………………… 33 2.7 References………………………………………………………………… 41 CHAPTER 3: LABORATORY AND FIELD EFFECTIVENESS OF LOW-COST CERAMIC FILTERS FOR DRINKING WATER TREATMENT IN CAMBODIA…………………………………………………. 51 3.1 Introduction……………………………………………………………….. 52 3.2 Purpose and objectives……………………………………………………. 55 3.3 Methods and materials……………………………………………………. 56 vi 3.4 Results…………………………………………………………………….. 70 3.5 Discussion………………………………………………………………… 78 3.6 Conclusions………………………………………………………………. 84 3.7 References………………………………………………………………… 106 CHAPTER 4: POINT-OF-USE DRINKING WATER TREATMENT IN CAMBODIA: A RANDOMIZED, CONTROLLED TRIAL OF LOCALLY MADE CERAMIC FILTERS……………………………………………………………... 110 4.1 Introduction……………………………………………………………….. 111 4.2 Purpose and objectives……………………………………………………. 115 4.3 Methods and materials……………………………………………………. 116 4.4 Results…………………………………………………………………….. 128 4.5 Discussion………………………………………………………………… 138 4.6 Conclusions……………………………………………………………….. 147 4.7 References………………………………………………………………… 164 CHAPTER 5: CERAMIC FILTERS FOR POINT-OF-USE DRINKING WATER TREATMENT IN RURAL CAMBODIA: INDEPENDENT APPRAISAL OF INTERVENTIONS FROM 2002-2005…………………………………………... 169 5.1 Introduction……………………………………………………………….. 170 5.2 Purpose and objectives……………………………………………………. 173 5.3 Methods and materials……………………………………………………. 174 5.4 Results……………………………………………………………………... 192 5.5 Discussion………………………………………………………………… 208 5.6 Conclusions……………………………………………………………….. 219 5.7 References………………………………………………………………… 243 vii CHAPTER 6: SUMMARY, CONCLUSIONS, AND FUTURE WORK……………………………………………………………………………. 247 6.1 Summary…………………………………………………………………... 247 6.2 Conclusions……………………………………………………………….. 248 6.3 Research needs and remaining questions…………………………………. 251 6.4 References………………………………………………………………… 256 viii LIST OF TABLES Table 2.1. Classification of infectious diseases related to water and sanitation………………………………………………………………….…….. 15 Table 2.2. Results of meta-analysis of effects of water-related interventions on diarrhea from Fewtrell et al. (2005)………………………….…... 23 Table 2.3. Estimates of baseline and maximum effectiveness of filter technologies against microbes in water, including porous ceramic filtration and other proposed POU filtration technologies…………….…… 32 Table 3.1. Lab-based effectiveness testing for low-cost ceramic pot-style filters: summary of evidence to date………………………………….…... 54 Table 3.2. Laboratory challenge water characteristics……………………….…….. 60 Table 3.3. Summary of laboratory effectiveness data for the CWP1, CWP2, and CWP3 ceramic filters…………………………………….……. 86 Table 3.4. Field effectiveness data summary for water treatment by boiling, the CWP1, and the CWP2 over the 18 week trial………………….…… 87 Table 4.1. Characteristics of study groups………………………………….……… 148 Table 4.2. Summary of longitudinal data for diarrheal disease (all) by biweekly surveillance point………………………………………….……... 149 Table 4.3. Summary of longitudinal data for dysentery (diarrheal disease with blood) by biweekly surveillance point……………….…….. 150 Table 4.4. Diarrheal disease prevalence proportions and filter effect estimates (CWP1) by age and sex of individuals……………………….……. 151 Table 4.5. Diarrheal disease prevalence proportions and filter effect estimates (CWP2) by age and sex of individuals……………………….……. 152 Table 4.6. Dysentery (diarrhea with blood) prevalence proportions and filter effect estimates (CWP1) by age and sex of individuals………….………. 153 Table 4.7. Dysentery (diarrhea with blood) prevalence proportions and filter effect estimates (CWP2) by age and sex of individuals…………….……. 154 Table 4.8. Measured levels of E. coli (cfu/100 ml) in household drinking water by study group……………………………………………….……… 155 ix Table 4.9. Mean E. coli counts (cfu/100 ml) and turbidity averages for samples taken in intervention households (untreated and treated water)………………………………………………….…….. 156 Table 4.10. Stratum-specific risk estimates for levels of E. coli in household drinking water samples, diarrheal disease in last 7 days…………………………………………………………………….…... 157 Table 4.11. Stratum-specific risk estimates for levels of E. coli in household drinking water samples, diarrheal disease with blood (dysentery) in last 7 days………………………………….……. 158 Table 5.1. Data summary and estimated odds ratios for selected factors. Odds ratios are adjusted for time elapsed since implementation………………………………………………….……. 221 Table 5.2. Observed levels of E. coli (cfu/100 ml) in household drinking water by study group……………………………………….….. 222 Table 5.3. Arithmetic mean total coliform and E. coli counts (cfu/100 ml) and turbidity for samples taken in intervention households (untreated and treated water)………………………….…... 223 Table 5.4. Geometric mean total coliform and E. coli counts (cfu/100 ml) and turbidity for samples taken in intervention households (untreated and treated water)…………………………….... 224 Table 5.5. Summary of log10 reduction values of E. coli by CWPs, by province………………………………………………………………….. 225 Table 5.6. Summary of log10 reduction values of E. coli by the CWP, stratified by time in use…………………………………………………... 226 Table 5.7. Summary of E. coli counts (cfu/100 ml) in filter treated water, by time in use……………………………………………………….... 227 Table 5.8. Summary of distribution of log10 reduction values of E. coli by CWPs compared with boiled, stored water……………………………. 228 Table 5.9. Selected characteristics of the intervention (households with CWPs) and control (without CWPs) groups from the longitudinal study of water quality and health………………………………………………………………………………… 229 Table 5.10. Summary of longitudinal data for diarrheal disease by surveillance point………………………………………………………..
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