Biodegradation of Spent Oil in Soil Using Citrullus Colocynthis Peels and Other Plant Wastes

Spent oil, which contains hazardous substances that pose health risk to man and his environment, are disposed indiscriminately on land in most mechanic workshops. The waste oil find its way into farmland and water bodies causing contamination of water, plants and lands. The ingestion of contaminated water, plants and animals lead to serious health issues. The abilities of plant wastes such as Citrullus colocynthis peels were investigated for the enhancement of the biodegradation of spent oil in soils. Contaminated soil in microcosms, A to J, were treated with plant wastes, duplicated to give 20 microcosms and incubated for 180 days. Periodic soil sampling from each microcosm was followed by cold extraction with dichloromethane and residual oil were analysed via Gas Chromatography/ Mass Spectrometry techniques (GC/MS). The results showed that the biostimulants accounted for 55.2 % of the total variation in the biodegradation result, P<0.001 at α = 0.05. The compounds identified ranged from C10- C35. The highest molecular weight compounds were 17-Pentatriacontene, 490.93 g/mol and 1-Hexacosene, 490.93 g/mol, while the lowest was p-Menth-8(10)-en-9-ol, cis, 154.25 g/mol. The compounds with the highest and lowest area percentage, 36.04 % and 0.97 % were 9-Octadecenamide, (Z)-, and 9, 9-Dimethyl-9-sila-9,10-dihydrophenanthrene respectively. About, four alkanes, six alkene, fourteen oxygenated, five nitrogen containing- and eight aromatic- compounds were identified after biodegradation. There was no statistical significant difference between the performances of each of the stimulant in the microcosms, P>0.1 at α = 0.05. There was an extremely significant difference between the performance of the stimulated microcosms and the natural attenuation containing NaN3, with P<0.001 at 0.05 significant level. The results show that plant wastes have abilities to enhance the biodegradation of the spent oil. Hence, Citrullus colocynthis peels generated in the Northern Nigeria and other plant waste can be used for cost-effective and safe degradation of spent and crude oil in the Southern Nigeria for the reclamations of lands for agricultural purposes.