Laboratory-scale experiments with a powdered compost biofilter treating benzene-polluted air

Results are reported and discussed on the treatment of benzene-polluted air streams with a laboratory-scale biofilter packed with powdered compost and using an indigenous microbial consortium. Different superficial gas velocities and influent benzene concentrations were investigated to establish the optimal operational conditions. Continuous experiments were conducted over about 1 year with the airflow directed upwards. A maximum removal capacity of 20.1 g m _{packing material}^-3 h^-1 was achieved at a benzene-loading rate of 24.8 g m^-3 h^-1. Benzene and biomass concentrations profiles along the column indicate that the distribution of biomass depended on the pollutant mass loading and that a linear relationship existed between biomass concentration and specific elimination rate. A biofilm model incorporating zero-order kinetics was applied to interpret and characterize the process macrokinetics. At low benzene inlet concentration and superficial gas velocity, the system performance was well described by a diffusion limitation model, whereas possible reaction limitation took place under harder conditions.