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COLUMN TESTS ON ARSENIC REMEDIATION USING ZEROVALENT IRON
Citation:
Su, C. AND R W. Puls*. COLUMN TESTS ON ARSENIC REMEDIATION USING ZEROVALENT IRON. Presented at Soil Science Society of America, Charlotte, NC, 10/21-25/2001.
Description:
It is urgent to find cost-effective remediation technologies to deal with arsenic contamination of groundwater if the current EPA allowable maximum contamination level of 0.05 mg As per liter is lowered to 0.01 mg As per liter in drinking water. We performed three column tests each with duplicate columns to study the behavior of arsenic removal by permeable reactive barrier (PRB) materials under dynamic flow conditions in the absence, as well as in the presence, of added phosphate and silicate. The column consisted of a 10.3-cm depth of 50 : 50 (Peerless iron : Oil Creek sand) in the middle and a 10.3-cm depth of Elizabeth City sediment in both upper and lower portions of the 31-cm long glass column. The flow rate was maintained at 28 mL per hour during the three- to four- month experiments. Consistent with previous batch studies in this laboratory, dissolved phosphate (0.5 or 1 mg P per liter) and silicate (10 or 20 mg Si per liter) showed strong inhibition for arsenate and arsenite (1 mg As(V) per liter + 1 mg As(III) per liter in 7 mM NaCl + 0.86 mM CaSO4) removal by Peerless iron in the column tests. Competition between arsenate and phosphate (also silicate) for the sorption sites on the Peerless iron seems to be the cause of the observations. This effect should be considered when designing a PRB of zerovalent iron for field use.