Impacts of nitrate and electron donor on perchlorate reduction and microbial community composition in a biologically activated carbon reactor

The sensitivity of perchlorate reduction and microbial composition to varied nitrate and acetate loadings was studied in a biologically activated carbon reactor with perchlorate loading and empty bed contact time fixed at 5 mg/L and 226 min, respectively. In stage 1, the sole electron acceptor ClO4- realized complete removal with >= 21.95 mg C/L of acetate supply. As nitrate loading gradually increased to 5 mg/L (stage 2), perchlorate reduction was slightly promoted and both ClO4- and NO3- were completely removed at an acetate loading of 29.7 mg C/L. When nitrate loading continued increasing to 10-60 mg/L (stage 3), perchlorate reduction converted to be inhibited, along with nondetectable NO3- and approximately exhausted DOC in effluent. When acetate loading increased to 43.9 mg C/L in stage 4, both ClO4- and NO3- were again removed, though lags still existed in perchlorate reduction. beta-Proteobacteria accounted for about 60%, 55%, 58%, 61% and 12% in samples from the base and top of the filter in stage 1 and those from the base, middle and top in stage 4, respectively. These findings implied that ratio of NO3- to ClO4- loadings and acetate loading were two key factors impacting ClO4- reduction and microbial structure along the filter. (C) 2016 Elsevier Ltd. All rights reserved.