Reduction of bromate in a biological activated carbon filter under high bulk dissolved oxygen conditions and characterization of bromate-reducing isolates

摘要

A biological activated carbon (BAC) filter was constructed using BAC from a pilot system that exhibited the ability to reduce bromate (BrO3-)and two BrO_3~--reducing bacteria were isolated and characterized. The BAC filter could almost completely reduce BrO_3~- (60 μ gBr/L) to bromide (Br~-) at an influent dissolved oxygen (DO) level of approximately 8.0 mg/L and an empty bed contact time of 30 ± 2 min using acetate as the electron donor shortly after the start-up. Phylogenetic analysis of the 16S rRNA gene sequences of a biological sample from the BAC filter showed that among the six detected orders, Rhodocyclales-and Burkholderiales-related microorganisms were dominant and Rhodocyclaceae- and Comamonadaceae-related microorganisms may play a role in BrO_3~- reduction. Two isolated pure cultures, i.e. Sphingomonas sp. 4721 and Deinococcus sp. 4710, exhibited the ability to reduce BrO_3~- in the presence of NO_3~-. The result of this study clearly indicated that DO was a competitor of BrO_3~- as an electron acceptor while NO_3~- was not. Construction of a BAC filter which could restrict oxygen transfer within a biofilm still remains to be a challenge.