Abstract

Bacillus cereus and Pseudomonas aeruginosa, that possess increased potential to degrade petroleum products exposed to UV-irradiation for 30 min followed by nitrous acid treatment, were employed in the biodegradation of effluent of a Refining and Petrochemical Company treated with NPK 15-15-15 organic fertilizer. While the untreated effluent achieved 89.25 and 77.63% degradation of oil and grease, and total petroleum hydrocarbons, respectively, the mutants achieved 69.66 and 49.46%, and 15.91 and 3.49%. The combined mutants achieved 76.8 and 66.24%, respectively, for B. cereus and P. aeruginosa. On treatment of the effluent with fertilizer prior to addition of the modified organisms, B. cereus achieved 95.27 and 80.22% and P. aeruginosa achieved 88.82% and 75.24%, while the combined mutants achieved 98.25 and 87.34%, respectively, for oil and grease and total petroleum hydrocarbons. Increased petroleum product degradation was achieved with fertilizer treatment and synergism was observed on combination of the mutants. Concurrent heavy metals assimilation – lead and chromium (VI) – were observed for the modified strains with the petroleum product degradation. Increased assimilation on combination of the modified organisms and application of fertilizer were also observed. Thus, both mutants could be employed in bioremediation of refinery effluents or any environment polluted with up to 5% (v/v) petroleum product, with increased efficiency on application of organic fertilizer, either alone or when combined.

Key words: Petroleum, fertilizer, biodegradation, effluent, refinery.