Succession of microbial communities and synergetic effects during bioremediation of petroleum hydrocarbon-contaminated soil enhanced by chemical oxidation

Biotechnologies integrated with chemical techniques are promising in treating the soils contaminated by petroleum hydrocarbons. Experiments by applying the degrading consortium and the modified Fenton (MF) with the chelator sodium citrate simultaneously were carried out to investigate the effects of the MF reagents on the degradation of total petroleum hydrocarbons (TPHs), changes in enzyme activities and the succession of microbial communities at the 0, 20, 100 and 500 mmol/kg hydrogen peroxide concentration levels. The ratio between hydrogen peroxide, ferrous sulfate and sodium citrate in the MF reagents was 100:1:1. The results indicated that the degradation of TPHs conformed to first-order kinetics and MF treatments increased the total removal rates of TPHs (4.73–24.26%) and activated dehydrogenase and polyphenol oxidase activities. A shift in microbial communities from Proteobacteria to Bacteroidetes was observed during the enhanced bioremediation, and the predominant genus shifted from Pseudomonas with an average relative abundance (ARAs) of 76.61% at the beginning to Sphingobacterium with ARAs of 52.06% at the later stage. The MF reagents at the proper level could simplify the relationship among the community populations, alleviate their competition and strengthen their associations, which would optimize the removal efficiency.