Biodegradation of treated refinery wastewater using mutant strains of selected microbial species.

Abstract

Due to high cost of treatment technologies, petroleum industries discharge their wastewater (effluent) without effective treatment, thereby causing pollution. This research was done to determine the microbial and physicochemical parameters of treated effluent of Warri petrochemical company and the petroleum degradability of modified Bacillus and Pseudomonas species on the effluent. Isolates from refinery effluent were determined using standard bacteriological methods and modified using x-ray mutagen. Microbial degradation of total petroleum hydrocarbon (TPH) in the refinery effluent revealed that Pseudomonas sp had a higher degradation potential than Bacillus sp. Greater reduction in biochemical oxygen demand (BOD) values was observed in the modified strain of isolates than their parents. TPH values for Bacillus + Effluent reduced from 0.98 to 0.26 and 0.98 to 0.18 for Bacillus + Effluent +fertilizer. Mutant Bacillus+ Effluent and MutantBacillus+Effluent+fertilizer reduced from 0.98 to 0.25 and 0.22 respectively. Similarly, TPH values for Pseudomonas + Effluent and Pseudomonas +Effluent +fertilizer reduced from 0.98 to 0.11 and 0.04 respectively. Mutant Pseudomonas + Effluent and Mutant Pseudomonas +Effluent +fertilizer reduced from 0.98 to 0.12 and 0.22 while the consortium of organisms +Effluent +fertilizer and control reduced from 0.98 to 0.20 and 0.67 respectively. The highest TPH degradation of 95.9% was observed for Pseudomonas +Effluent +fertilizer while the least (73.5%) was observed for Bacillus + Effluent. Statistical analysis of variance at 95% confidence level indicates that there was significant difference between the bioremediation potentials of both parents and their mutants. Therefore, Pseudomonas species and their mutants should be employed in bioremediation of petroleum hydrocarbon wastewater