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Bioremediation of modelled petroleum-contaminated soils of the Niger Delta and the impact of zeolite augmentation
Williams, Joseph
Williams, Joseph
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2014-04
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The bioremediation of modelled petroleum oil-contaminated soils of the Niger Delta by a mixed culture of three hydrocarbon-degrading bacteria, Acinetobacter sp, Rhodococcus sp and Pseudomonas sp, was investigated. These bacterial strains were selected based on criteria that they were able to utilize hydrocarbons (hexadecane and sodium benzoate) as the sole source of carbon and energy and were able to show significant growth in crude oil at an optimum temperature of 30oC. For maximal bacterial growth and degradation effective aeration and agitation was required, thus the choice of the shake flask method over the bioscreen growth analyzer for this investigation. The influence of hexadecane concentrations (0.5%, 1.0% and 2.0%) on the bacterial isolates was investigated and it revealed that the Rhodococcus sp because of its different metabolic pathway showed a more rapid growth on hexadecane concentrations as compared Pseudomonas sp and Acinetobacter sp. Amongst the bacterial isolates, Pseudomonas sp exhibited a more rapid growth on 0.5% sodium benzoate while the two others showed minimal growth. Pseudomonas sp Rhodococcus sp and Acinetobacter sp showed a synergistic association when grown on basal salt medium supplemented with 1.0% w/v petroleum crude oil. The influences of a zeolite (clinoptilolite), soil structure and particle size on biodegradation of crude oil in modelled silt-clay and sandy soil of Niger Delta was investigated. Soils from the Hilton site, East-Shropshire, United Kingdom were used for the Niger Delta soils formulation. Geochemical properties of the soil samples from the x-ray fluorescence showed major elements are sodium, magnesium, aluminum, potassium, iron with silicon having high percentage, while x-ray diffraction analysis revealed minerals such as quartz, kaolinite, illite and smectite, which are similar to those of the Niger Delta. The preliminary investigation showed a more rapid and greater extent of apparent oil removal with the addition of both bacterial consortium and clinoptilolite on soil amendment experiments at 30oC for a period of 30 days. There was 79% oil removal by the bacterial consortium in the soil amended with clinoptilolite as compared to 67% in the case of the amended soils without clinoptilolite. Although the addition of both bacterial consortium and clinoptilolite enhanced the removal of the crude oil, however the effect of clinoptilolite may be one of abiotic removal. The soil structure investigation without clinoptilolite augmentation showed that oil removal in the silt-clay soil was significantly greater than that of the sandy II soil after 30 days period (p< 0.0001). There was 72.7% ± 0.8% oil removal by the bacterial consortium in the silt-clay soil as compared to 55.6% ± 0.7% in the case of the sandy soil. However, there was 79.1% ± 0.4% oil removal by the bacterial consortium in the silt-clay soil amended with clinoptilolite as compared to 67.3% ± 0.8% in the case of the amended sandy soils with clinoptilolite. Gas chromatographic profile showed appreciable reductions in hydrocarbon, the rate of which depended upon the particular hydrocarbon. Quantitative analysis of residual oil extract from the silt-clay and sandy soil amended with and without zeolite showed a high rate of degradation for lighter hydrocarbon components (C10– C18) compared to the heavier ones (C24 – C28) by the bacterial consortium. Hydrocarbon components (C10– C18) from both silty-clay and sandy soils amended with zeolite were degraded by the bacterial consortium to 92.1% - 57.7% and 74% - 43.7% respectively, while the soils without zeolite showed degradation rate of 80.4% - 44.8% (silt-clay) and 69.4% - 42.8% (sandy). Hydrocarbon components (C24– C28) from both soils showed an apparent low rate of degradation. The results of this study indicate that the application of the bacterial consortium and clinoptilolite lead to greater rates of biodegradation in the clay soil then in the sandy soil. Studies showed that nutrient addition and aeration both affected the rate of hydrocarbon utilization. The postulated application of selected bacteria in the bioaugumentation of oil contaminated environment in the Niger Delta region was discussed.
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Williams, J. (2014) Bioremediation of modelled petroleum-contaminated soils of the Niger Delta and the impact of zeolite augmentation. University of Wolverhampton. http://hdl.handle.net/2436/322349
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en
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A thesis submitted in partial fulfilment of the requirements of the
University of Wolverhampton for the degree of Master of Philosophy.