Abiotic and Biotic Perchlorate removal in an activated carbon filter

Granular activated carbon (GAC) filtration experiments demonstrated that perchlorate was removed by ion exchange rather than by chemical reduction. A column ion‐exchange capacity of 0.172 mg perchlorate per g GAC was calculated. Batch tests confirmed that ion exchange was the dominant mechanism of perchlorate removal by GAC. When influent dissolved oxygen (DO) was 2.5 mg/L and an electron donor solution was supplied, efficient reduction of 50 μg/L perchlorate was achieved using biologically active carbon (BAC) filtration. Perchlorate reduction decreased as the concentration of nitrate in the filter increased. With low influent DO and nitrate concentrations and excess electron donor added, the BAC filter removed 50 μg/L perchlorate to below detection for 103 days of flow at a 25‐min empty bed contact time. Batch biological experiments verified the occurrence of biological reduction and demonstrated that microorganisms in the BAC filter converted perchlorate completely to chloride.