Thesis Abstract

Abstract
Soil pollution with engine oil is a significant environmental concern due to its adverse effects on soil quality and ecosystem health. Bioremediation, particularly through the use of agricultural waste and inorganic fertilizers, has been proposed as a cost-effective and environmentally friendly approach to mitigate engine oil pollution in soils. This study investigated the effect of agricultural waste (specifically rice straw) and inorganic fertilizer (urea) on the biodegradation rate of soil contaminated with engine oil. The experimental setup involved the establishment of microcosms containing soil samples spiked with engine oil at a concentration of 5% w/w. Four treatment groups were established Control (only engine oil contaminated soil), Agricultural waste (engine oil contaminated soil + rice straw), Inorganic fertilizer (engine oil contaminated soil + urea), and Combined (engine oil contaminated soil + rice straw + urea). The biodegradation process was monitored over a 90-day period by measuring the residual engine oil concentration in the soil samples. Results indicated that the addition of agricultural waste and inorganic fertilizer significantly enhanced the biodegradation rate of engine oil in the contaminated soil compared to the control group. The combined treatment of rice straw and urea resulted in the highest biodegradation rate, with a 68% reduction in engine oil concentration observed after 90 days. The agricultural waste treatment and inorganic fertilizer treatment also showed significant improvements in biodegradation rates, with 54% and 48% reductions in engine oil concentration, respectively, compared to the control group. Microbial analysis revealed an increase in microbial population and activity in the soil samples treated with agricultural waste and inorganic fertilizer, indicating enhanced biodegradation potential. The presence of rice straw and urea provided additional carbon and nitrogen sources for the indigenous microbial community, promoting the degradation of engine oil contaminants. Overall, the results of this study demonstrate the effectiveness of agricultural waste and inorganic fertilizer in enhancing the biodegradation rate of engine oil in contaminated soil. The findings highlight the potential of bioremediation strategies utilizing agricultural by-products and synthetic fertilizers to remediate engine oil pollution in soils, offering a sustainable and eco-friendly solution to soil remediation challenges.

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