Effect of bioaugmentation and natural attenuation on physicochemical characteristics of soil contaminated with graded concentrations of spent engine oil

In this study, the role of Alcaligenes aquatilis and Bacillus subtilis isolated from spent engine oil-impacted soil in Mechanic Village, Uyo, using the enrichment culture technique in stimulating the removal of petroleum hydrocarbons from contaminated soil was assessed. The effect of graded concentrations of spent engine oil application on the physicochemical properties of University of Uyo garden soil, Akwa Ibom State, Nigeria, were determined before and at the end of eight weeks of degradation studies. Nine experimental microcosms were prepared with 4 kg of garden soil and contaminated at 5 %, 10 %, 15 % and 20 % respectively. Statistical analysis (ANOVA) of data obtained from the studies revealed a significant difference (p<0.001) between the physicochemical properties of untreated and treated soil samples. The initial pH values of polluted soil were 5.7±0.05, 6.1±0.03, 6.50±0.11 and 6.84±0.01 but increased at the end of remediation studies to a range between 7.25±0.01 to 8.35±0.04. The post-treatment results on the properties of the test soil revealed improvement in the levels of plants' essential nutrients. Based on the results of this work A. aquatilis and B. subtilis is strongly recommended for the cleanup and bioremediation of spent engine oil-impacted soil in contaminated sites.