Abstract
The potential of six microorganisms (Pseudomonas aeruginosa, Micrococcus sp, Flavobacterium sp, Rhizopus sp, Penicillium sp and Fusarium sp) isolated from hydrocarbon contaminated site were evaluated for their biodegradation ability. The soil samples were contaminated with 5% (w/v) of spent engine oil and the rate of biodegradation of the oil was studied for a period of 10weeks under greenhouse experiment. The total heterotrophic bacteria count (THBC), total hydrocarbon degrading bacteria count (THDBC), physicochemical and heavy metals properties of the soil samples and Total Petroleum Hydrocarbon (TPH) were determined after treatment with test organisms. THBC and THDBC ranged from 0.175 to 0.280 CFUg-1 and 0.47 CFUg-1 respectively for the control plot, while THBC is ranging from 0.197 to 0.275 CFUg-1 and THDBC was 0.180 to 0. 473 CFUg-1 for the contaminated plot. There was a slight increase in the pH value of the contaminated soil sample and the treated soil samples as the experimental weeks increased. The results obtained 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 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 incubation with the tested organisms. Plant growth in the treated contaminated soil samples ranged from 32.6cm to 38.6cm, while that of the control 1 (Uncontaminated soil) was 51.2cm and 19.7cm high was observed in the Control 2 (contaminated untreated soil) after 22 days of the experiment. The TPH degradation (% loss) ranged from 79.7 to 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 at 79.9%.
All the microorganisms used in this study had the abilities to remediating soil contaminated with spent engine oil and the remediated soil samples were able to support the growth of Zea mays at 5% (w/v) level of contamination.
