Low-Cost Separation of Arsenic from Water: With Special Reference to Bangladesh

The main objective of the study was to develop a low-cost technique for the removal of arsenic from contaminated groundwater, as found in Bangladesh. It was shown that arsenic can be removed by co-precipitation with the naturally occurring iron which is found in groundwater. Tests showed that the removal rate was largely controlled by the arsenic concentration, the iron/arsenic ratio, and pH. Iron precipitation was induced by aeration and mixing through manual shaking.
Bench-scale tests demonstrated that up to 88% of the arsenic (III) in water could be removed by settlement over a period of 24 h. This was better than the removal rate achieved by filtration. It was found that the removal rate was mainly independent of the mode of mixing. For solid-liquid separation, draw-off arrangements were studied. It was found that the sample should be drawn off with a slow flowrate (<0.5 l/min). In such conditions the treated water quality is not seriously impaired for the particular design of the container which was examined.
From maps of the known distributions of arsenic, iron and pH, it was evident that 63% of the area in Bangladesh complied with the Bangladesh standard for arsenic. By interpreting the maps and applying the potential removal identified in the study, it was estimated that a further 9% of the area would comply with the Bangladesh standard, freeing 8 million people from arsenic contamination.