Dichloromethane removal and microbial variations in a combination of UV pretreatment and biotrickling filtration

•DCM removal performance of the combined UV–BTF was much better than the single BTF.•Different sections in BTF contributed differently to DCM removal and mineralization.•Ozone remaining from UV controlled the secretion of EPS and thus maintained normally.•Pyrosequencing analysis showed a drastic change of bacterial community in biofilters.•The microbial diversity was higher and biomass distributed evenly in combined BTF. Biofiltration of hydrophobic and/or recalcitrant volatile organic compounds in industry is currently limited. A laboratory-scale system integrating ultraviolet (UV) photodegradation and a biotrickling filter (BTF) was developed to treat dichloromethane (DCM), and this was compared to BTF alone. A combined UV–BTF approach permitted faster biofilm formation and greater removal than BTF. DCM distribution and its photodegradation intermediates revealed that the lower filter of the UV–BTF contributed more to CO2 production; the upper filter assisted more with DCM removal. The UV–BTF kept secretion of extracellular polymeric substances at a normal level with an evenly distributed biomass. Pyrosequencing analysis showed that the dominant population in the combined biofilter was more diverse than that in BTF alone. Our data provide a foundation for understanding the effect of UV pretreatment on BTF performance and the microbial community.