Low-Dosage Ozonation in Gaseous VOCs Biofilter Promotes Community Diversity and Robustness

Abstract BackgroundOzonation of biofilter is known for alleviating clogging and pressure drop issues while maintaining removal performances in biofiltration systems treating gaseous VOCs (Volatile Organic Compounds). The implications of ozone on the biofilter microbiome, in terms of biodiversity, community structure, metabolic abilities and dominant taxa correlated with performance remain largely unknown.MethodsThis study investigated two biofilter treating high concentration toluene operating in parallel, with one acting as control and the other exposed to low-dosage (200 mg/m3) ozonation. Microbial community diversity, metabolic rates of different carbon sources, functional predictions and microbial co-occurrence networks of both communities were examined. ResultsConsistently higher biodiversity of over 30% was observed with microbiome after ozonation, with increased overall metabolic abilities for amino acids and carboxylic acids. Relative abundance of species with reported stress tolerant and biofilm forming abilities significantly increased, with a consortium of changes in predicted biological pathways, including shifts in degradation pathways of intermediate compounds, while correlation of top OTUs and genus with performance indicators show diversifications in microbiota responsible for VOCs degradation. Co-occurrence network of the community shows a decrease in average path distance and average betweenness with ozonation. ConclusionShifts in major degrading species and increase in biodiversity could explain the consistent performance commonly seen in ozonation of biofilters despite the decrease in biomass. Increased presence of stress tolerant microbes in the microbiome coupled with decentralization of the co-occurrence network suggest that ozonation could not only provide amelioration for clogging issues but also provides a microbiome more robust to loading shocks seen in full-scale biofilters.