Pseudomonas sp. SR-5 was isolated as a styrene-degrading bacterium. In liquid culture containing 1% (v/v) styrene, more than 90% styrene was degraded in 53 h and the doubling time of SR-5 was 2 h. The removal of styrene gas was investigated in biofilters for 31 days using an organic packing material of peat and an inorganic packing material of ceramic inoculated with SR-5. The maximum-styrene-elimination capacities for peat and ceramic packing materials were 236 and 81 g m(-3) h(-1), respectively. The percentage of styrene converted to low molecular weight compounds including CO(2) in the peat and ceramic biofilters during a 10-day operation were estimated to be 90.4 and 36.7%, respectively. As the pressure drop in the peat bioflter at the end of experiment was significantly higher than that in ceramic biofilter, a biofilter using a mixture of peat and ceramic was tested. We determined that the maximum elimination capacity was 170 g m(-3) h(-1) and the production of low molecular weight compounds was 95% at a low pressure drop for this mixed packing material filter.

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The growth of a styrene-degrading bacterium, Pseudomonas sp. SR-5, was inhibited by benzoic acid (BA), one of the styrene degradation intermediates, in liquid culture. A benzoic acid-degrading microorganism, Raoultella sp. strain A, was isolated from a peat biofilter inoculated with a wastewater. The styrene removal efficiencies of the two laboratory-scale biofilters inoculated with only strain SR-5 and a mixed culture of strains SR-5 and A were compared using a mixed packing material of peat and ceramic (1:1) for 45 days. The biofilter with the mixed culture showed a higher removal efficiency than that with a single culture of SR-5. The maximum elimination capacities of the biofilters with the mixed culture and the single culture were 141 g m(-3)h(-1) and 106 g m(-3)h(-1), respectively. In the biofilter with the single culture, 136 g of benzoic acid (m3 of dry packing material)(-1) was accumulated at the end of the experiment. However, no accumulation of benzoic acid was observed in the biofilter with the mixed culture.