In the context of very high prevalence of diarrhoeal diseases in Bangladesh, bacteriological quality received priority as a criterion for drinking water supply. Groundwater is normally free from pathogenic microbes and adequately available in shallow aquifers for development of low-cost tubewell based water supply. Bangladesh achieved a remarkable success by providing 97% of the rural population with bacteriologically safe tube well water. Unfortunately, arsenic in excess of acceptable limit has been found in tubewell water in most parts of Bangladesh. Water quality studies conducted so far...