Performance of Andesite as an Inorganic Packing Material in a Laboratory-Scale Biotrickling Filter for BTEX Removal

Volatile aromatic compounds (BTEX: benzene, toluene, ethylbenzene, and xylenes) are toxic and odor-active volatile organic compounds of environmental and health concern. Conventional biofiltration systems often rely on organic packing materials that deteriorate over time, motivating the evaluation of more durable inorganic alternatives. In this study, andesite, a volcanic rock, was assessed as a packing material in a laboratory-scale biotrickling filter (BTF) for the removal of BTEX from air streams. The reactor was operated under controlled conditions at different empty-bed residence times, and BTEX concentrations were monitored using TD-GC/MS. Removal performance was interpreted in relation to biofilm development, supported by physicochemical characterization of the packing material and contextual microbial analysis of the microbial community structure by amplicon sequencing. The results showed that the andesite-packed BTF achieved high BTEX removal efficiencies after an acclimation period, with stable operation under the tested conditions. Microbial analysis revealed the dominance of bacterial groups commonly associated with aerobic degradation of aromatic hydrocarbons. These findings indicate that andesite can function as a mechanically stable and biologically compatible inorganic support for BTEX treatment in biotrickling filters at the laboratory scale. The study is limited to bench-scale operation and community-level microbial analysis; therefore, further work is required to evaluate long-term performance, scale-up potential, and functional metabolic interactions.