Perchlorate Reduction In A Packed Bed Bioreactor Using Elemental Sulfur

This study investigated perchlorate reduction by sulfur utilizing perchlorate reducing bacteria (SUPeRB). SUPeRB cultures were enriched from a denitrifying wastewater inoculum in medium containing elemental sulfur (S), crushed oyster shell, nutrients and perchlorate. Perchlorate was reduced from 5 to < 0.5 mg/L in approximately 15 days. The enrichment culture was subsequently inoculated into a continuous flow packedbed bioreactor containing S and crushed oyster shell medium. High-level perchlorate concentrations (5-8 mg/L) were reduced to < 0.5 mg/L with an empty bed contact time (EBCT) of 13 hours. Low levels of perchlorate concentrations (80-120 g/L) were treated varying two parameters, recirculation ratio and empty bed contact time (EBCT). Little or no recirculation was required to efficiently reduce perchlorate to < 4 g/L. The system also proved somewhat independent of EBCT. Investigations of the effect of nitrate on perchlorate removal and reactor media particle size is on going and will be presented at the meeting.