Performance and microbial community evolution of toluene degradation in the presence of acetone vapors using hybrid membrane-aerated biofilm reactors (HMABRs)

Biological treatment methodologies offer cost-effective and eco-friendly solutions for volatile organic compounds (VOCs) removal, but they face limitations in effectively treating hydrophobic VOCs. Herein, this study introduces the Hybrid Membrane Aerated Biofilm Reactor (HMABR) for VOC treatment. The HMABR integrates a bio-trickling filter-like spraying function with MABR technology to construct a non-submerge system. What's more, introducing hydrophilic gases enhances the degradation of hydrophobic VOCs in pollutant biotreatment. While hydrophilic VOCs are readily degraded by microorganisms, the mechanisms of their co-degradation remain understudied. Toluene and acetone, common industrial VOCs, were examined in the HMABR system. HMABR exhibits outstanding toluene removal, reaching a maximum capacity of 142.04 gm−3h−1. The addition of acetone boosts this capacity by 70.1 gm−3h−1, altering EPS composition, and notably increasing the PN/PS ratio from 0.35 to 2.76. It can be inferred that acetone's presence enhances biofilm EPS hydrophobicity, aiding toluene breakdown. Besides, when adding acetone, the biofilm EPS sample exhibited a more compact secondary protein structure. Analysis of the microbial community in the HMABR system identified a dominance of Pseudomonadota, with an increased abundance of Rhodanobacter, which correlated strongly with toluene degradation in the presence of acetone. Gene analysis revealed an increase in toluene degradation genes in Rhodanobacter when acetone was added. Furthermore, acetone activation was found to enhance metabolic pathways related to xylene degradation and the tricarboxylic acid (TCA) cycle, thereby improving toluene removal efficiency. These findings provide insights into co-metabolism in treating hydrophobic pollutants in HMABR and contribute to designing more effective treatment systems for VOCs.