Effect of selenium(IV) on biodegradation of <i>m</i> -dichlorobenzene exhaust gas in biotrickling filters

Selenium(IV) (Se(IV)) supplementation was evaluated as a biostimulant to enhance <i>m</i>-dichlorobenzene (<i>m</i>-DCB) biodegradation in laboratory-scale biotrickling filters (BTFs) inoculated with <i>Brevibacillus agri</i> DH-1. An optimal Se(IV) concentration of 4.0 mg/L increased steady-state <i>m</i>-DCB removal efficiency from 74.38% to 81.74% at an empty bed residence time (EBRT) of 90 s. When the EBRT was reduced to 30 s, BTF2 maintained a 41.74% removal efficiency, compared with only 17.64% for BTF1. Se(IV) promoted extracellular polymeric substance production, strengthened biofilm adhesion, enhanced catechol-1,2- and catechol-2,3-dioxygenase activities, and moderated surface charge to favour microbial aggregation. Fourier-transform infrared spectroscopy confirmed Se(IV)-facilitated dechlorination and aromatic-ring cleavage, while 16S rRNA sequencing revealed enrichment of key degraders including <i>Brevibacillus</i>, <i>Pseudomonas</i>, <i>Bacillus</i>, <i>Rhodanobacter</i>, and <i>Sphingobium</i>. These findings demonstrate a novel micronutrient-based strategy to improve BTF performance for treating chlorinated aromatic exhaust gases.