Bioremediation of a polycyclic aromatic hydrocarbon-contaminated soil by using different aerobic batch bioreactor systems

The intrinsic depuration capability of a soil contaminated by polycyclic aromatic hydrocarbons (PAHs) originating from a contaminated industrial site was evaluated in this study by using different aerobic batch bioreactors: a slurry-phase bioreactor, a blade-agitated bioreactor, and a rotary vessel bioreactor. For each bioreactor, the disappearance of 14 target PAHs and of the total extractable organic matter was monitored. The three treatments exhibited rapid and extensive removal of the PAHs, which disappeared at different degradation rates according to their molecular weight and aromaticity degree. PAHs with two, three and four aromatic rings were degraded in sequence, with average rates that generally decreased as the number of molecule rings increased. A slight increase in the bacterial biomass concentration and significant CO2 production were also observed during the time course of the treatments. Among the three treatments, the slurry-phase system provides the most effective and fastest removal of the PAHs and the organic extractable matter. However, the semisolid-phase systems exhibited PAH depletion capabilities higher than those reported in the literature for sails with similar particle size distribution in solid-phase conditions.