Analysis of overall perchlorate removal rates in packed-bed bioreactors

Perchlorate (ClO-⁴) can be used as a terminal electron acceptor by some bacteria for cell respiration during the oxidation of substrates. Packed-bed biofilm reactors have been used to treat perchlorate-contaminated waters with rates varying over six orders of magnitude (0.0007 to 20 mg/L-min). While this range implies large differences in treatment efficiencies, it is demonstrated in this report that these rates are correlated to concentrations of perchlorate in the reactor. Overall perchlorate reduction rates obeyed first-order kinetics for reactors using organic substrates as electron donors (acetate or a complex high-protein medium). Higher reaction rates appear possible in hydrogen-gas feed reactors rather than in organic-feed reactors, although additional work is necessary to confirm this preliminary result. Findings of first-order perchlorate kinetics will help engineers design packed-bed reactors for the remediation of perchlorate-contaminated waters.