Regular articleEffects of irrigation and water content of packing materials on a thermophilic biofilter for SO2 removal: Performance, oxygen distribution and microbial population

•The success of a thermophilic biofilter relied on an optimum water content.•The water content of packing materials varied with irrigation interval time.•Water content influenced oxygen distribution in packing materials.•Microbial population varied with oxygen concentration in packing materials.

The water content (WCR) of packing materials is a key factor that determines the success of biofilters, particularly thermophilic bioreactors, for off-gas treatment. An optimum WCR can be accomplished by directly irrigating packing materials. In this study, the performance of a thermophilic biofilter for SO2 removal was investigated by different irrigation times. The removal efficiency of SO2 was largely influenced by the water content of packing materials, which varied with irrigation time. An average SO2 removal efficiency of 98% could be achieved when WCR was >80%. The thermophilic biofilter required daily irrigation to maintain the optimum WCR. Oxygen distribution varied in polyurethane foam cubes (PUFCs) at different WCRs. PUFCs with a high WCR provided aerobic-low oxygen-aerobic areas. Microbial population also varied accordingly. For the thermophilic biofilter in treating SO2, over 80% was the optimal WCR which could be achieved by continuous irrigation.