High levels of arsenic in well water are causing widespread poisoning in Bangladesh. In a typical aquifer in southern Bangladesh, chemical data imply that arsenic mobilization is associated with recent inflow of carbon. High concentrations of radiocarbon-young methane indicate that young carbon has driven recent biogeochemical processes, and irrigation pumping is sufficient to have drawn water to the depth where dissolved arsenic is at a maximum. The results of field injection of molasses, nitrate, and low-arsenic water show that organic carbon or its degradation products may quickly mobilize arsenic, oxidants may lower arsenic concentrations, and sorption of arsenic is limited by saturation of aquifer materials.

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Over the last several decades, much of population of Bangladesh and West Bengal switched their water supply from surface water to groundwater. Tragically, much of the region's groundwater is dangerously contaminated by arsenic, and consumption of this water has already created severe health effects. Here we consider how groundwater flow may affect arsenic biogeochemistry and we compare the vertical patterns of groundwater chemistry at our intensive study site with the average values across the country. Detailed hydraulic data are presented from our field site that begins to characterize the groundwater flow system.

Water safety plans (WSPs) are promoted by the WHO as the most effective means of securing drinking water safety. To date most experience with WSPs has been within utility supplies, primarily in developed countries. There has been little documented experience of applying WSPs to small community-managed systems, particularly in developing countries. This paper presents a case study from Bangladesh describing how WSPs can be developed and implemented for small systems. Model WSPs were developed through consultation with key water sector practitioners in the country. Simplified tools were developed to translate the formal WSPs into a format that was meaningful and accessible for communities to use. A series of pilot projects were implemented by Non-Governmental Organisations (NGOs) across the country covering all major water supplies.The results show that WSPs can be developed and implemented for small community managed water supplies and improve the sanitary condition and water quality of water sources. Hygiene behaviour improved and household water quality showed a significant reduction in contamination. Chlorination was found to be important for some technologies, thus increasing the costs of water supply and raising important problems with respect to transfer to the communities. Simple tools for community monitoring were found to be effective in supporting better water safety management.