Removal of arsenic from ground water by manganese dioxide-coated sand

In a laboratory study, manganese dioxide-coated sand (MDCS), prepared by re acting potassium permanganate with manganese chloride under an alkaline con dition and in the presence of sand, showed promise as a medium for use in s mall systems or home-treatment units in developing areas of the world, for removing arsenic(III) and arsenic(V) from ground water. In ten cycles of do wnflow column tests [bed depth 400 mm; empty-bed contact time 74 min; influ ent arsenic 0.5 mg As/L of arsenic(III) and 0.5 mg Asn of arsenic(V)], brea kthrough bed volumes at the World Health Organization guideline value of 0. 01 mg As/L for arsenic in drinking water were in the range of 153-185 per c ycle. During regeneration (backwashing with 2 L, of a 0.2 N sodium hydroxid e solution), 85.0% of the removed arsenic was recovered in the first cycle, and 94.6-98.3% was recovered in subsequent cycles. A low-cost, simple home arsenic removal unit, containing 6 kg (4 L) of the MDCS medium and operate d at 6 L/h, produced 740 and 700 L of water in two cycles of runs when the influent arsenic concentration was 0.5 mg As/L of arsenic(III) and 0.5 mg A s/L of arsenic(V). No arsenic(III) or leaching of manganese from the medium was detected in the effluent. A detailed study addressing the effects of s ome important factors (water pH, concentration and type of competing anions , and cations) on the process is needed. The home arsenic removal unit shou ld be subjected to field trials to assess the long-term effects on performa nce.