Potential for native hydrocarbon-degrading bacteria to remediate highly weathered oil-polluted soils in Qatar through self-purification and bioaugmentation in biopiles

Petroleum-derived contamination events constitute a unique environmental issue in the arid areas because of the weathering processes, accentuated due to harsh conditions and representing the main origin of failure of bioremediation applications. The industrial area of Dukhan and the AlZubara coast represent wethered oily-sites as an appropriate model due to the extreme weather, which characterizes Qatar. Indigenous bacteria would be highly adapted and when re-introduced or stimulated would conduct to the remediation of these sites. An appropriate approach to bioremediating-weathered oil was investigated in these two areas. Systematic soil sampling was performed, and the soil samples were analyzed. The results clearly showed the harsh chemical compositions (high salinity and contents of total petroleum components contents in the range of the oil organics). By implementation of a procedure of isolation of highly adapted bacteria, few hydrocarbon-degrading bacteria were isolated in the objective of selecting those for further application. Their identification by ribotyping showed dominance of Bacillus and Virgibacillus in AlZubara site, and Bacillus and Pseudomonas in Dukhan site. All bacterial strains were highly tolerant to 10 % diesel and showed potential of removal of 20 %–85 % of C(10) to C(36) hydrocarbons. This potential was confirmed by determination of the n-heptadecane/pristane and n-octadecane/phytane ratios, indicating in turn their potential to bioremediate oil. This was demonstrated by comparison of the self-remediation to bioaugmentation using two selected Bacillus and Pseudomonas strains using Dukhan soil in biopiles. These strains when biostimulted in such a soil increased the removal of total petroleum components to 53 % compared to 30 % with self-purification, after 90 d. The results indicated that highly adapted endogenous bacteria might be used to bioremediate highly weathered oil-contaminated soil under harsh conditions.