Biosand water filters for floating villages in Cambodia: safe water does not prevent recontamination

Water for Cambodia used biosand filters (BSFs) to provide microbiologically safe drinking water for people in Moat Khla floating village in 2010 and 2011. All 189 families use the lake, which by World Health Organization (WHO) standards is deemed unsafe for drinking water. Surveys from December 2010 to February 2011 compared 40 families using BSFs and 40 families not using BSFs. Over 92% of BSF households and 90% of non-BSF households were using high-risk lake source water (>100 colonies Escherichia coli/100 mL). Only 2.5% of BSF households had filtered water with bacteria in the high-risk range and only 5% of these 40 households showed recontamination in their storage water. Forty percent of non-BSF households had high-risk bacteria levels in their stored water, and most used no treatment. Storage water for non-BSF families showed a significant reduction in mean log₁₀E. coli levels compared to their lake source water. Stored water for non-BSF families showed recontamination even for UV-treated water and boiled river water. Recontamination occurs in both groups but is much less for BSF households highlighting the value of proper storage containers used by BSF households and the need for water and sanitation education for floating villages in Cambodia.