In rural Bangladesh people drink water from an estimated 10-11 million tube wells, many with arsenic concentrations well above the national standard of 50µg/L. Characteristic skin lesions and more serious health effects are probable. The research reported here was designed to determine the relation between arsenic concentration and skin lesions on hands and feet controlling for education, use of tube well water, protein consumption and body mass index (BMI). The investigation included a well survey, a prevalence survey and a nested case-referent analysis. Studies were conducted in two villages (population 11670) in northern Bangladesh. In the well survey 1509 wells in use were identified and measurements of arsenic concentration made in 1422 (94%). Three estimates were made for each well, which yielded correlation among repeats = 0.93. The overall median was 47mg/L and the highest recorded 1760 mg/L. Paramedics examined soles and palms of 11087 individuals for skin lesions and identified 168 cases (1.5%). In the third phase, cases (over 16 years) were matched by age, gender and village to referents (target of 3) without skin lesions. Cases and referents were interviewed about protein in diet, use of well water, education and residential history. Conditional logistic regression was used to assess the effects of arsenic concentration, controlling for confounders. Subjects with lesions had a higher median concentration (250µg/L) than those without (47µg/L). Prevalence increased with both age and arsenic concentration, reaching 26.7% in those over 50 years of age and >500 µg/L. Of the 160 cases (≥16 years) 137 were interviewed, 127 with arsenic concentration measured in well water, together with their 504 referents. Cases were somewhat more likely to have lived in the villages throughout their lives and less likely to report using tube well water for cooking. The final model confirmed the high risk of lesions associated with arsenic concentrations. Using ≤50µg/L for comparison, an odds ratio of 15.2 (95%CI 7.2-32.2) was observed for those using tube wells with concentrations >500 µg/L, adjusting for use of tube well water in cooking and lifetime residence in the villages. The results from this research provide continuing support for the use of 50µg/L as a useful national standard. While the enforcement of this standard has immediate value, it cannot be considered final without comparable information on more serious health risks.

This thesis outlines results of a series of studies investigating the removal of two common taste and odour compounds, 2-methylisoborneol (MIB) and geosmin, from drinking water using biologically active sand filtration. A combination of full-, pilot- and laboratory-scale studies were carried out. A review of long term water quality data from a South Australian water treatment plant indicated that the conventional plant was capable of removing MIB and geosmin to below detection limit without the need for additional treatment. A series of laboratory studies were carried out, validating the theory that the geosmin removal was occurring through biological activity in the rapid gravity filters of the water treatment plant. Microorganisms capable of geosmin removal were found to be present in the settled water of two South Australian water treatment plants, Morgan and Happy Valley. Laboratory sand column experiments were conducted with these waters and a range of sand media, investigating the effect of biofilm development on MIB and geosmin biodegradation. It was found that the process could produce effective removals, however long start-up periods were often required. A laboratory-scale column utilising new sand fed with Happy Valley settled water took in excess of 300 days before it was capable of removing MIB and geosmin by greater than 80%. Studies on sands with inactivated pre-existing biofilms required much shorter biofilm development periods, from 30 to 40 days. The results of the column studies indicated that a method to encourage sand filters to operate biologically for MIB and geosmin removal would be advantageous. Two methods were studied: preozonation and bacterial inoculation. Pre-ozonation was carried out at a pilot plant, constructed at the Happy Valley water treatment plant. Additional factors investigated during this study were the length of the biofilm development period and the impact of empty bed contact time (EBCT). Preozonation is often used in tandem with biological filtration to increase the fraction of biodegradable organic matter and in turn increase the biomass activity of the filter. The pilot plant consisted of two sand filters; one fed with settled water and one fed with preozonated settled water. Pre-ozonation did not enhance the biodegradation of MIB or geosmin. The pre-ozonated column was run for 550 days. Removals of MIB and geosmin were inconsistent throughout the trial. The maximum removal obtained during the study was 80% for MIB and geosmin, at an EBCT of 45 minutes, after 380 days of operation. The settled water column was run for over 650 days. By day 560, the column was able to remove 60% of the influent geosmin and 40% of the influent MIB at an EBCT of 10 minutes, which is close to that used in full-scale plants. Significant effects of empty bed contact time were not noted in the range of 10 to 30 minutes. Bacterial inoculation studies were carried out at laboratory-scale. The inoculum comprised of a geosmin-degrading consortium of three Gram-negative bacteria previously isolated from the biofilm of the Morgan water treatment plant filter sand. A sand column with a pre-existing biofilm was inoculated with the organisms, achieving 70% removal of geosmin. Inoculation of columns without biofilms gave lower geosmin removals, with an average of 41% removal. These were preliminary studies only, and further work is required. A biomass activity assay, based on the concentration of adenosine triphosphate (ATP), was developed over the course of the project. This assay was particularly helpful when studying the attachment of the inoculum in the laboratory columns. Other methods to study biomass were flow cytometry to enumerate the water-borne and biofilm associated bacteria, and scanning electron microscopy to obtain a visual observation of the biofilms on various sands. This work demonstrated the potential of biological sand filtration for MIB and geosmin control. It was shown that long biofilm development periods are evident before effective removal of the compounds can occur. The potential to minimise these long biofilm development periods by inoculation of filters with geosmin degrading organisms was demonstrated. / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1340100 / Thesis (Ph.D.) -- University of Adelaide, School of Chemical Engineering, 2008

Thesis (M.S.)--University of Nevada, Reno, 2006. / "May, 2006." Includes bibliographical references (leaves 116-121). Online version available on the World Wide Web.

Thesis (Ph. D.)--University of Nevada, Reno, 2005. / "December, 2005." Includes bibliographical references. Online version available on the World Wide Web.

Thesis (LL. M.)--University of Toronto, 2004. / Adviser: Michael Trebilcock.

Thesis (M.S.)--Virginia Polytechnic Institute and State University, 1992. / Vita. Abstract. Includes bibliographical references (leaves 123-127). Also available via the Internet.

Thesis (M.S.)--Virginia Polytechnic Institute and State University, 1992. / Vita. Abstract. Includes bibliographical references (leaves 127-133). Also available via the Internet.

Thesis (Ph.D.)--Hong Kong University of Science and Technology, 2009. / Includes bibliographical references (p. 170-191).

Thesis (doctoral)--Göteborgs universitet, 2003. / Includes bibliographical references.

Thesis (M.S.)--University of Michigan, 1995. / Includes bibliographical references.