Effects of oxygen and water content on microbial distribution in the polyurethane foam cubes of a biofilter for SO2 removal

The performance of a biofilter for off-gas treatment relies on the activity of microorganisms and adequate Oand HO. In present study, a microelectrode was applied to analyze Oin polyurethane foam cubes(PUFCs) packed in a biofilter for SOremoval. The Odistribution varied with the density and water-containing rate(WCR) of PUFCs. The Oconcentration dropped sharply from 10.2 to 0.8 mg/L from the surface to the center of a PUFC with 97.20%of WCR. The PUFCs with high WCR presented aerobic–anoxic–aerobic areas.Three-dimensional simulated images demonstrated that the structure of PUFCs with high WCR consisted of an aerobic "shell" and an anoxic "core", with high-density PUFCs featuring a larger anoxic area than low-density PUFCs. Moreover, the HO distribution in the PUFC was uneven and affected the Oconcentration. Whereas aerobic bacteria were observed in the PUFC surface, facultative anaerobic microorganisms were found at the PUFC core, where the Oconcentration was relatively low. Oand HO distributions differed in the PUFCs, and the distribution of microorganisms varied accordingly.