Bioremediation of the Petroleum Contaminated Desert Steppe Soil with Rhodococcus erythropolis KB1 and Its Effect on the Bacterial Communities of the Soils

A petroleum hydrocarbon degrading bacterium Rhodococcus erythropolis KB1 was used to investigate the bioremediation efficiency of the petroleum contaminated desert steppe soils. The total petroleum hydrocarbons (TPHs) removal efficiency in the soils was analyzed with different treatments including natural degradation, bioaugmentation with R. erythropolis cells, biostimulation with nitrogen and phosphorus, and a combination of bioaugmentation and biostimulation. The petroleum contaminated soils were separately inoculated with R. erythropolis cells, nitrogen and phosphorus nutrients, a combination of the bacterial cells and the nutrients. The soil samples were kept at room temperature for 115 days of bioremediation. On the 66th day, the soil samples were strengthened with the same treatments. The results showed that the degradation rate of the natural degradation group was 20.20%. The biodegradation rates of the bioaugmentation group and biostimulation group were 36.02 and 40.10%, respectively. The combination group of bioaugmentation and biostimulation was the most effective way to remediate petroleum-contaminated soils with a degradation rate of 43.89%. In the bioremediation process the saturated hydrocarbons, especially the linear alkanes were the most easily degraded petroleum components. The cultivable bacterial counts of the soils were significantly increased in the bioaugmentation, biostimulation, and combined groups with bioaugmentation and biostimulation. The bacterial diversities of the petroleum contaminated desert steppe soil changed greatly when compared with that of the natural desert steppe soil. The bacterial structure and abundance of the soils in different treatments also changed significantly.