Bioremediation of hydrocarbon contaminated gasoline station soil by a bacterial consortium

A study was undertaken to find methods for enhancing rates of hydrocarbon biodegradation in gasoline-contaminated soil by ex-situ bioremediation. Garden soil was treated with gasoline-spilled soil from a gasoline station and different combinations of amendments were prepared using mixed bacterial consortium, poultry litter, coir pith and rhamnolipid biosurfactant produced by Pseudomonas aeruginosa. Bacterial growth, hydrocarbon degradation and growth parameters of Phaseolus aureus RoxB (including seed germination, chlorophyll content, shoot and root length) were measured for a period of 90 days. Approximately 78% of the hydrocarbons were effectively degraded within 60 days in soil samples amended with all additives. Maximum germination rate, shoot length, root length and chlorophyll content in Phaseolus aureus were each recorded after 60 days. Further incubation to 90 days did not cause significant improvements. Statistical analysis using Analysis of Variance and Duncan's Multiple Range test revealed that the level of amendments, incubation time and combination of amendments significantly influenced bacterial growth, hydrocarbon degradation, seed germination and chlorophyll content (1% probability level). All tested additives, including rhamnolipid biosurfactant, had significant positive effects on the bioremediation of gasoline-contaminated soils.