Title:
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Use of waste glass for arsenic removal from drinking water in Bangladesh : a laboratory and field-based study
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A number of low-cost synthetic filtration media have been proposed for the removal of arsenic (As) from drinking water in areas such as Bangladesh, where exposure to environmental arsenic is a major human health issue. This PhD research project examines the application of recycled glass and waste stainless steel fragments as a practical medium for arsenic removal at a household scale. To assess the performance of recycled glass media as a practical filter bed, glass granules were differentiated by colour, size and mode of glass size reduction (imploded and ground). The selected glass granules were used as media for batch adsorption and column filtration experiments using a prepared As (III) test solution and using natural As-contaminated water in Bangladesh, where recycled glass in column filtration mode was used to treat arsenic contaminated natural water in the presence of other metalloids. Filter media made from recycled glass and waste stainless steel fragments were characterized via SEM and PXRF. SEM study also gave information about the mechanism of arsenic removal by glass granules. Sequential extraction experiments were also performed on used filtration media to assess arsenic removal and adsorption processes. Results indicate that glass granules associated with stainless steel fragments (sstl) can remove arsenic from drinking water at an efficiency suitable for household application. Arsenic removal effectiveness depends largely on the presence of stainless steel fragments with glass (introduced with the glass media during the recycling and preparation process). The glass particle size and mode of size reduction was also found to influence the removal of arsenic: ground glass performed better than imploded glass and smaller ground glass particles (s < 0.5 mm) performed better than imploded glass of the same size. Batch experiment results concluded that glass colour may have minor influences on arsenic removal although the differences were not significant. Further results also revealed that < 0.05 kg sstl can remove arsenic to below acceptable limits from a 0.50 ppm arsenic solution with an effectiveness > 0.168 mg/g sstl. It was found that 57 kg of small clear DSGF (dry sieved ground fresh) glass (s < 0.5 mm) can treat 132.5 l of water with 100% removal of arsenic from starting concentrations of 0.50 ppm, using a recycled glass filter column. There is a scope for improvement of the glass filter media by adding stainless steel fragments but the study did not determine the potential and further work is required to optimize the ratio of DSGF glass and stainless steel fragments. Considering the price and operational drawbacks of other existing filters in Bangladesh, recycled glass has potential to be used in more sustainable arsenic filter filtration units. The results, coupled with the low cost of waste glass, indicate that waste glass should be investigated further for use in domestic water filtration for arsenic removal.
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