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Three identical upflow laboratory-scale biofilters, inoculated with the benzene-degrading strain Pseudomonas sp. NCIMB 9688 but filled up with different packing media (PM), specifically raw sugarcane bagasse, sieved sugarcane bagasse and peat, were employed to eliminate benzene from waste air. Biofilters performances were evaluated by continuous runs in parallel at different influent benzene concentrations, sequentially stepped up through three different superficial gas velocities (31, 61, and 122 m h(-1)). The peat-packed biofilter exhibited the best performances over the whole experimentation, ensuring removal efficiency of 100% for influent benzene concentrations < or = 0.05 g m(-3), regardless of the superficial gas velocity, and up to 0.4 g m(-3) at 31 m h(-1). Maximum elimination capacities of biofilters packed with raw and sieved sugarcane bagasse and with peat were 3.2, 6.4 and 26 g mPM(-3) h(-1) at 6.1, 12 and 31 g mPM(-3) h(-1) loading rates, resulting in 52, 53 and 84% removals, respectively. The bacterial concentration distribution along the medium was shown to depend on the benzene loading rate and a correlation between specific benzene elimination rate and biomass concentration was established for biofilters packed with sieved sugarcane bagasse and peat. The macrokinetics of the process were also studied using the profiles of benzene and biomass concentrations, collected under different conditions over the height of both biofilters, and a zeroth-order kinetic model was shown to describe successfully the degradation process.

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