Collaborative removal of NOx and toluene in flue gas driven by aerobic denitrifying biotrickling filter

Nitrogen oxides (NOx) and volatile organic compounds (VOCs) may cause ozone formation and photochemical smog pollution, which may damage to human health and ecological environment seriously. An aerobic Denitrifying BioTrickling Filter (DBTF) for collaborative removal of nitrogen oxides (NOx) and toluene in flue gas was investigated. NOx and toluene removal efficiency were up to 90% and 95%, respectively. Mycobacterium, Comamonas and Pseudomonas were predominant bacteria; Mycobacterium, Pseudomonas, Comamonas, Microbacterium, Reyranella, Stenotrophomonas and Alicycliphilus were the core toluene oxidizing-denitrifying genera, denitrification genes (narGHI, nirK, nasB, napAB, nosZ and norC) and toluene oxidation genes (tom, E1.14.13.7, xyl, cat, todE, tes, mhp, pch, pob, pca, lig, gal) responsible for bacterial oxidation of toluene and NOx reduction, as shown by16S rDNA and metagenomic sequencing. Bacterial oxidation of toluene was coupled to NOx reduction in which toluene served as the electron donor while NOx served as the electron acceptor and thereby redox between toluene and NOx was formed, toluene was degraded through the classical aerobic aromatic compound degradation pathway. DBTF was capable of both toluene oxidation and NOx reduction by denitrification. These results show that the DBTF is achievable and open new possibilities for applying the DBTF to simultaneous removal of NOx and VOCs.