Biotreatment of Soil Contaminated with Spent engine Oil by Locally Isolated Microorganisms

Abstract

Bioremediation is an eco-friendly process that makes use of microorganisms to break down hazardous compounds like hydrocarbons into simpler and innocuous compounds. In this study, hydrocarbon degrading microorganisms were isolated from contaminated soil samples. Isolated microorganisms were identified and screened for their biodegradation abilities in aerobic conditions. The soil samples were contaminated with 5% (w/v) of spent engine oil and total heterotrophic bacteria count (THBC) and total hydrocarbon degrading bacteria count (THDBC) were determined by plate count method, while physicochemical and heavy metals properties of the soil samples were analysed by titrimetric and atomic absorption Spectrophotometry respectively. Gravimetric analysis was used to determine Total Petroleum Hydrocarbon (TPH) after treatment with test organisms. THBC and THDBC ranged from 175 -280 × 10 5 CFU/g and 47 -95 × 10 3 CFU/g respectively for the control plot, while THBC ranged from 197 -275 × 10 3 CFU/g and THDBC was 180 -473 × 10 5 CFU/g for the contaminated plot. Six microorganisms; Pseudomonas aeruginosa, Micrococcus sp, Flavobacterium sp, Rhizopus sp, Penicillium sp and Fusarium sp were isolated from hydrocarbon contaminated sites. The results obtained from the greenhouse experiment showed a significant decrease (at p ≤ 0.05) in the nutrients content of the soil samples. There was an increase from 1.09 in the negative control to 15.5% in the content of organic matter after contamination and from 1.88% to 26.8% in the % of organic matter too. There was a significant reduction (at p ≤ 0.05) in the concentration of Fe, Zn, Pb, Cd, Cu, Cr and Ni after 10 weeks of treatment with the tested organisms, but increase in pH values was observed in all the treatments. The TPH degradation (% loss) ranged from 79.7% -89.2% after 10 weeks of treatment. P. aeruginosa had the highest level of degradation (89.2%), while Micrococcus sp and Rhizopus sp had the least degradation of 79.9%. This study showed that all the bacteria isolated from the spent engine oil contaminated soil were able to degrade the spent engine at concentration of 2% (w/v). Soil samples also supported the growth of Zea mays after six weeks of treatment. Therefore, all the isolated bacteria can be used in biodegradation experiment.Citation: Ayandele, Abiodun A, 2018. Biotreatment of Soil Contaminated with Spent engine Oil by Locally Isolated Microorganisms. Advances in Environmental Biology 12(11): 22-28.