Efficient degradation of dichloromethane by novel cell-immobilized-filled biotrickling filters: Performance and mechanisms.

Dichloromethane (DCM) is a toxic and recalcitrant volatile organic compound (VOC), and its effective treatment remains challenging due to low biodegradability and slow biofilm establishment in conventional biotrickling filters (BTFs). To address this limitation, a novel composite spherical filter PU-H13@PP-AC, consisting of polyurethane foam immobilized with Methylobacterium rhodesianum H13 and packed into activated-carbon-modified polypropylene spheres-was synthesized and applied in a BTF (hereafter BTF3). To comparatively evaluate performance, two additional BTFs were operated with PU@PP (BTF1) and PU-H13@PP (BTF2) filters, and all systems were continuously tested for 155 days, including a starvation phase. PU-H13@PP-AC (BTF3) exhibited superior results, achieving biofilm formation 5-8 days faster than the controls, a removal efficiency of 88 % at 300 mg·m-3 and an elimination capacity 1.6-1.8 times higher than the other filters at an EBRT of 20 s. Following a 30-day starvation period, BTF3 rapidly recovered to 95.3 % removal within three days, demonstrating strong resilience. Mechanistic analyses indicated enhanced microbial adhesion, a higher proportion of viable cells (up to 97.5 %), and enrichment of functional taxa (Proteobacteria, Methylobacterium), accompanied by increased signaling molecules that improved stress resistance and long-term stability. These results demonstrate that PU-H13@PP-AC effectively overcomes major limitations of conventional BTFs by enabling rapid start-up, stable long-term operation, and high recovery capacity. The proposed filter therefore provides a cost-effective and environmentally friendly strategy for DCM emission control, offering practical potential for large-scale industrial VOC treatment.