Removal of perchlorate in ground water with a flow-through bioreactor

The bacterium,perclace, has been shown to reduce perchlorate to less than the detection limit of 0.004 mg L-1 when grown on acetate under anaerobic conditions. In batch studies, the presence of nitrate does not significantly hinder the reduction of perchlorate. The ability of perclace to remove nitrate and perchlorate from ground water in a flow-through system is described in this study. Celite-pac ked columns of 300 mi were used to demonstrate the removal of perchlorate from ground water. At a flow rate of 1 mi min(-1), perchlorate was removed from 0.738 mg L-1 to less than detectable levels and when the pow rate was 2 ml min(-1) 92 to 95% of the perchlorate was removed. Analysis of bacterial biomass at the completion of the study revealed that most of the bacterial growth was concentrated in the inlet area of the column. A circulating pump was added, with the idea that passing the ground water multiple times through the bacterially active zone might increase the efficiency of the column. In this experiment, perchlorate in ground water was reduced from 0.550 mg L-1 to nondetectable levels at a flow rate of 1 mi min(-1). When the flow rate was increased to 2 mi min(-1), 98% of perchlorate was removed and when the now rate was 3 mi min(-1) 95% of perchlorate was removed. Rapid removal Of perchlorate by perclace immobilized in a bioreactor may provide an efficient, cost-effective technology for ground water remediation.