Simultaneous mercury oxidation and NO reduction in a membrane biofilm reactor

This work demonstrates bacterial oxidation of mercury (Hg-0) coupled to nitric oxide (NO) reduction in a denitrifying membrane biofilm reactor (MBfR). In 93 days' operation, Hg-0 and NO removal efficiency attained 90.7% and 74.1%, respectively. Thauera, Pseudomonas, Paracoccus and Pannonibacter played dual roles as Hg-0 oxidizers and denitrifiers simultaneously. Denitrifying bacteria and the potential mercury resistant bacteria dominated the bacterial community. Denitrification-related genes (norB, norC, norD, norE, norQ and norV) and enzymatic Hg-0 oxidation-related genes (katG, katE) were responsible for bacterial oxidation of Hg-0 and NO reduction, as shown by metagenomic sequencing. XPS, HPLC-ICP-MS and SEM-EDS indicated the formation of a stable mercuric species (Hg2+) reasulting from Hg-0 oxidation in the biofilm. Bacterial oxidation of Hg-0 was coupled to NO reduction in which Hg-0 served as the initial electron donor while NO served as the terminal electron acceptor and thereby redox between Hg-0 and NO was formed. MBfR was capable of both Hg-0 bio-oxidation and denitrifying NO reduction. This research opens up new possibilities for application of MBfR to simultaneous flue gas demercuration and denitration. (C) 2018 Elsevier B.V. All rights reserved.