Bacteriological analysis of spent engine oil contaminated soil planted with cowpea (Vigna unguiculata)

Abstract

The bacteriological analysis of soil contaminated with spent engine oil (SEO) planted with cowpea was investigated. The aim of this study was to detect the microbial degradation of SEO in soil and how it affects the microbial activity and the effects of SEO on the growth of cowpea. SEO collected from a mechanic workshop in Ilorin was introduced into soil in varying concentrations. The experimental set up was in triplicates with six treatments of SEO. Soil samples were taken every week for the duration of six weeks for laboratory analysis. Plant growth parameters were measured every week after planting. The pH of the soil and the bacterial population of the soil were also observed. Findings revealed that the plant growth parameters were significantly reduced as the concentration of SEO increased in the soil. Bacterial counts were also determined and a total of six bacterial species were isolated from the soil samples. Bacillus subtilis, Micrococcus luteus, Pseudomonas aeruginosa and Pseudomonas putida occurred in the control and contaminated soil samples. Bacterial counts ranged from 1.89×10⁵ to 4.25×10⁵ cfu/ml in the soil samples with the highest occurring in the control and the least occurring in 224ml of SEO. SEO contaminated soil has adverse effect on cowpea and on bacterial flora of the soil. The results of this study revealed that Pseudomonas aeruginosa, Micrococcus luteus and Bacillus subtilis can utilize SEO in the soil. They could be harnessed for use in bioremediation of soil polluted with petroleum and petroleum products.

Key Words: Bacteria, Spent engine oil, Soil, Cowpea