Utilization of Different Microbes in Bioremediation of Hydrocarbon Contaminated Soils Stimulated With Inorganic and Organic Fertilizers

Abstract

Different microbes (E.coli, Proteus, Klebsiella and Pseudomonas sp) were utilized in degradation of different hydrocarbon (Engine oil/diesel, kerosene and fuel) contaminated soils amended with inorganic (NPK and urea) and organic (cow dung and poultry litter) fertilizers and in some their combination. The incubation period ranged from 3-18 days. Bacterial population count and residual hydrocarbon were determined .Results showed that bacterial population count increased as the microbes utilized hydrocarbon for carbon and energy sources, the increase in population count and degradation of the hydrocarbons was stimulated by the fertilizer. It was also observed that as the population count increased due to hydrocarbon utilization for carbon and energy, residual hydrocarbon decreased and percentage degradation increased. Urea fertilizer was the best amendment for E.coli to degrade kerosene, NPK and cow dung differently aided the same E.coli in degrading engine oil. Pseudomonas and Proteus species degraded kerosene and fuel better in the presence of NPK fertilizer. Klebsiella specie degraded diesel and engine oil better when amended with poultry litter and cow dung respectively at least for the first 9 days. More than 90% of the hydrocarbons were degraded within each incubation period. The microbes began to die as from the 15 th day of incubation, this may be due to secretion of toxic secondary metabolites. Control experiments revealed that there was initial increase in population count of the microbes as they utilized the hydrocarbon for carbon and energy, but they began to die because of non-stimulation with fertilizer, therefore less than 50% of the hydrocarbons were degraded in all the control experiments. Maize seeds grew on the remediated soil within six (6) days of planting.