Development of an economical and efficient adsorbent for arsenic removal from groundwater

Abstract

Population census data carried out in Cambodia indicate that 2.25 million people live within the arsenic affected area. A portion of this population uses tube-wells for drinking and cooking. Some of these wells are highly contaminated with arsenic. This study found that the concentration of arsenic in the groundwater system (rural area of Cambodia) is in the range of 365 - 736 ppb, which is over the WHO limits (10 ppb). A total of 27 units of household filters have been constructed and placed in three different places at Toul ta Chan village, Chbar Ampor district, Cambodia, for arsenic-free groundwater supply. Three types of household filters were constructed; laterite filter (L-filter), biosand filter (B-filter) and laterite + biosand filter (LB-filter). The household filters had been in operation for 193 days to filter 7760 L of groundwater highly contaminated with arsenic. During that period, the filtered water (filter‘s effluent) has arsenic concentration below WHO limits (10 ppb). Filters performance are as follows; 96% of arsenic, 99% of iron, 8.27% of silicate and 77% of phosphate were removed by L-filter. 94% of arsenic, 99% of iron, 1.28% of silicate and 78% of phosphate were removed by B-filter. 99% of arsenic, 99% of iron, 15% of silicate and 84% of phosphate were removed by LB-filter. The constructed filters have different range of effluent flow rates; 0.08 - 0.66 L min-1 for L-filter, 0.26 - 2.27 L min-1 for B-filter and 0.22 - 0.8 L min-1 for LB-filter. The presence of silicate and phosphate in the groundwater system has no effect on the filter performance to remove arsenic. While the concentrations of sulfate and fluoride is below the limit of detection. The laterite used in household filter has an arsenic capacity of 0.005 mg g-1 before the filter‘s effluent exceeds 10 ppb (WHO limits).