Bacterial Reduction of Perchlorate and Nitrate in Water

Abstract A bacterial isolate, strain perclace, was shown to reduce the ground water contaminant perchlorate (ClO−4) to levels <0.005 mg L−1 when grown on acetate under anaerobic conditions. The ability of perclace to simultaneously reduce perchlorate and another ground water pollutant, nitrate (NO−3), was examined in batch studies and in a sand‐packed column under saturated flow conditions. Nitrate removal was monitored using ion chromatography, and perchlorate removal was monitored using a perchlorate specific electrode or ion chromatography, depending on the study. In batch studies, the reduction of 0.089, 0.92, 12.0, and 122 mg L−1 perchlorate was examined in the presence and absence of 62 mg L−1 NO3. Perchlorate was reduced more rapidly in the absence of NO−3 than in its presence. However, both perchlorate and NO−3 were reduced by more than 10‐fold within 48 h. A sand‐packed column (2.8 by 14 cm) inoculated with perclace simulated a flow‐through biotreatment system for water contaminated with a low level of perchlorate (0.130 mg L−1) and a much higher level of NO3 (125 and 20 mg L−1). Biotreatment could reduce perchlorate to <0.005 mg L in a 3 h residence time. The addition of NOr initially decreased the efficiency of perchlorate removal, however within 1 d the biotreatment system had adjusted such that there was complete removal of perchlorate and the reduction of NO−3 to <1 mg L−1.