Efficient removal of heavily oil-contaminated soil using a combination of fenton pre-oxidation with biostimulated iron and bioremediation

Crude oil contamination severely deteriorates soils quality. Bioremediation utilizing soil indigenous organisms could be employed to decompose petroleum hydrocarbons thanks to its low cost and minor environmental disturbance. However, slow kinetics limit the successful application of this biotechnique. Pretreating oil contaminated soils with Fenton pre-oxidation could accelerate the subsequent bioremediation process. This study was to explore the mechanisms behind the rapid propagation of indigenous petroleum-degrading bacteria (IPDB) and the efficient degradation of total petroleum hydrocarbons (TPH) in soil after Fenton pre-oxidation with biostimulated iron. Biostimulated iron and non-biostimulated iron were used in the experiments, where Fenton pre-oxidation was combined with the bioremediation of oil-contaminated soil (TPH = 13221 mg/kg). Although the amount of Fenton pre-oxidized TPH (3331-3775 mg/kg) was similar with biostimulated and nonbiostimulated irons, the biodegradation of TPH after Fenton pre-oxidation with biostimulated iron (5840 mg/kg) was much higher than that with non-biostimulated iron (3034-4034 mg/kg). Moreover, abundant nutrients and a high population of residual IPDB were found after Fenton pre-oxidation with biostimulated iron, which benefited stable consumption of NH3-N and dissolved organic carbon (DOC) by IPDB during the subsequent bioremediation. However, Fenton pre-oxidation with non-biostimulated iron either resulted in greater damage to IPDB or produced fewer nutrients, thereby failing to ensure the continuous propagation of IPDB during the subsequent bioremediation. Therefore, we propose that Fenton pre-oxidation with biostimulated iron should be applied to heavily oil-contaminated soils prior to bioremediation.

Automated summary

Crude oil contamination severely impacts soil quality. Bioremediation utilizing soil indigenous organisms offers a cost-effective and environmentally friendly approach for petroleum hydrocarbon decomposition. However, slow kinetics hinder the efficacy of this biotechnique. This study investigates the use of Fenton pre-oxidation and biostimulated iron to enhance the bioremediation process for oil-contaminated soil. Results show that the combination of Fenton pre-oxidation and biostimulated iron promotes the rapid growth of indigenous petroleum-degrading bacteria (IPDB) and increases the degradation of total petroleum hydrocarbons (TPH) in soil. However, the use of non-biostimulated iron in Fenton pre-oxidation fails to sustain IPDB propagation during subsequent bioremediation.