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

摘要

Waters containing ClO4- and dissolved NO3-, derived from detonated explosives and solid propellants, often also contain elevated concentrations of other dissolved constituents, including SO42-. 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 NO3-, SO42- and ClO4-. 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 (NO3- N) to trace levels through NO3- reduction to NH4+ using ZVI alone and through denitrification using OC. Observations from the mixture of ZVI and OC suggest a combination of NO3- reduction and denitrification. Up to 71% of input SO42- (24.5 +/- 3.5 mg L-1) was removed in the column containing OC, and >99.7% of the input ClO4- (857 +/- 63 mg 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 ClO4- removal followed first-order and zero-order rates, respectively. Nitrate >2 mg L-1 (NO3- N) inhibited ClO4- removal in the OC- containing column but not in the (ZVI + OC)-containing column. Sulfate did not inhibit ClO4- degradation within any of the columns.