Simulating a biopile for understanding the bioremediation activity in a polluted soil

To evaluate the remediation activity of oil degrading bacterial strains, contained in a dried microbial consortium inoculant, it is required to distinguish between degradation activities operated by native microbiota and that due to the newly introduced strains. The effect due to chemical compounds contained into the inoculant as a support should also be considered. Previous studies showed that in an aged polluted soil the autochthonous microbial population seems to be highly specialized for diesel fuel degradation, probably due to the long period of time under such a selective pressure. Therefore, the use of microbial inoculants might fail to improve the rate of soil remediation. Previous experiments indicated that using formulation specifically designed for diesel degradation, the oil content in the soil was strongly and rapidly reduced under lab-scale if promptly applied after the contamination occurrence. The aim of this study was to investigate on the effect of both the microbial inoculant, and the chemicals compounds , on the rate of oil degradation in a newly contaminated soil. This was attained by the construction of lab-scale biopiles artificially contaminated with diesel fuel and equipped with recycling systems to simulate a field scale structure. The results obtained showed that in the inoculated biopile the diesel oil content decreased approximately to 20% of the initial value, while it remained constant in the non inoculated one. No effects were due to the chemicals contained in the formulation. DNA based techniques confirmed an effective colonization of soil by the bacterial consortium present in the inoculant