Application of selected microbial consortia combined with inorganic and oleophilic fertilizers to recuperate oil-polluted soil using land farming technology

Bioremediation is an important technology for the restoration of oil-polluted environments by the use of indigenous or selected microorganisms. We analyzed the efficiency of two selected microbial consortia (A and B) inoculated in combination with inorganic fertilizer (NPK) or oleophilic fertilizer (S200 commercial) on the degradation of polycyclic aromatic hydrocarbons (PAH) by applying them in land farming treatments. Consortium A was composed of Bacillus pumilus, Alcaligenes faecalis, Micrococcus luteus, and Enterobacter sp.; consortium B was composed of B. pumilus, Enterobacter sp., and Ochrobactrum anthropi. Land treatment was performed in separated plots and the evolution of biodegradation rates was followed for 7 months. Treatment with NPK and inoculation with consortium A efficiently reduced the n-alkane hydrocarbons. In contrast, the application of S200 C and inoculation with consortium B reduced the hydrocarbon removal capacity of polluted soil and they did not show any advantage respected to the non-treated control plot. In addition, the results showed that inoculation with consortium A and application of the combined treatment consortium A + NPK fertilizer gave the highest percentage of PAH removal. These results suggest that the inoculation of polluted soil with consortium A, integrated by hydrocarbon-degrading bacteria and biosurfactant/bioemulsifier-producing bacteria, would be a useful method for improving hydrocarbon biodegradation. In conclusion, inoculation with a selected bacterial consortium at the beginning of a land treatment followed by treatment with NPK fertilizer is an efficient combination treatment of bioaugmentation and biostimulation for application in the bioremediation of soil polluted with hydrocarbons.