Ozone is a strong disinfectant known to kill bacteria and viruses. But when pumped into biofiltration systems at low doses ozone seems to have the opposite effect, boosting microbe activity and thus filtration performance all while relieving clogging issues by reducing overall biomass. To find out how ozone improves biofilter performance, researchers examined two toluene-treating biofilters at the microbial level. One served as the control, while the other was exposed to a low dose of ozone. The microbiome of the exposed filter consistently showed 30% higher biodiversity than the control filter with an increased capacity to break down amino and carboxylic acids. In addition, ozonation led to a higher abundance of stress-tolerant and biofilm-forming species causing a shift in the degradation pathways of certain compounds. The tighter microbial co-occurrence network observed for the filter exposed to ozone suggests a more stable microbial community robust to shocks a highly desirable feature in full-scale biofilters. These findings offer valuable insight into how and why low concentrations of ozone improve biofilter performance and could help engineers build better filters for high-value industrial applications.