Biodegradation of Benzene in a Laboratory-Scale Biobarrier at Low Dissolved Oxygen Concentrations

A laboratory-scale permeable biobarrier exhibited high removal efficiencies of benzene at inlet concentrations of 0.4 to 35.1?mg/L and with a limited supply of dissolved oxygen. The supplied oxygen was less than the demand for a complete aerobic oxidation of benzene. Stainless steel pieces or granulated peat moss were used as packing material for microbial support in the biobarrier. Removal efficiencies ranged from 63.9% to 99.9% in the stainless steel-packed biobarrier and from 70.4% to 97.2% in the peat moss-packed biobarrier, while benzene elimination rate changed from 0.2 to 10.4?mg/L-d and from 0.1 to 3.7?mg/L-d in the two biobarriers, respectively. The consumption of sulfate and the presence of sulfate-reducing bacteria suggested the contribution of anaerobic metabolism in the biodegradation of benzene. The biodegradation of benzene under microaerophilic conditions (defined as dissolved oxygen concentrations <2?mg/L) was demonstrated during independent batch experiments. The maximum specific rate of benzene biodegradation with concentrations of 22.0 to 65.9?mg/L under microaero-philic conditions was 2.6 mg/mg biomass-d.