Treatment of Dissolved Perchlorate, Nitrate, and Sulfate Using Zero‐Valent Iron and Organic Carbon

Waters containing ClO 4 − and dissolved NO 3 − , derived from detonated explosives and solid propellants, often also contain elevated concentrations of other dissolved constituents, including SO 4 2− . Four column experiments, containing mixtures of silica sand, zero‐valent Fe (ZVI) and organic C (OC) were conducted to evaluate the potential for simultaneous removal of NO 3 − , SO 4 2− and ClO 4 − . Initially, the flow rate was maintained at 0.5 pore volumes (PV) d −1 and then decreased to 0.1 PV d −1 after 100 PV of flow. Nitrate concentrations decreased from 10.8 mg L −1 (NO 3 –N) to trace levels through NO 3 − reduction to NH 4 + using ZVI alone and through denitrification using OC. Observations from the mixture of ZVI and OC suggest a combination of NO 3 − reduction and denitrification. Up to 71% of input SO 4 2− (24.5 ± 3.5 mg L −1 ) was removed in the column containing OC, and >99.7% of the input ClO 4 − (857 ± 63 μg L −1 ) was removed by the OC‐ and (ZVI + OC)‐containing columns as the flow rate was maintained at 0.1 PV d −1 . Nitrate and ClO 4 − removal followed first‐order and zero‐order rates, respectively. Nitrate >2 mg L −1 (NO 3 –N) inhibited ClO 4 − removal in the OC‐containing column but not in the (ZVI + OC)‐containing column. Sulfate did not inhibit ClO 4 − degradation within any of the columns.