Abstract

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Soil contamination by spent engine oil from mechanical parts of machines is a growing concern in many countries. Biostimulation of contaminated soil with agro-waste like Citrullus lanatus (water melon) and Citrus sinensi (orange) peels offers an environmentally friendly and cost-effective method for remediating the contaminated soil. In this study, biostimualtion of 200g soil contaminated with 20 ml spent engine oil was enhanced using water melon peel (WP), orange peel (OP) and water melon and orange peels compost (WP+OP). This was undertaken for a period of 56 days under room condition. The result showed that the hydrocarbon utilizing bacteria (HUB) counts obtained from the nutrient-treated sample when compared with those from the oil-amended-untreated were statistically significant (P < 0.05). The presence of Micrococcus spp., Pseudomonas spp., Bacillus spp., Klebsiella spp. and Proteus spp. were detected after amendment with watermelon and orange peels agro-wastes from the contaminated soil. The result also showed that amendment with 40g orange peels had higher percentage degradation (75%) compared to the watermelon peels (56%). The half-life (t½) of the amended soil sample treated with combined agro-waste was observed to be 8.45 days as compared to 9 days and 10.66 days observed after individual treatments with orange and watermelon peels respectively. This study has proven that water melon and orange peel samples have stimulating potential in the biodegradation of spent engine oil from the contaminated soil. Keywords: Agro-wastes, biostimulation, contaminated soil, spent engine oil

Keywords: Agro-wastes, biostimulation, contaminated soil, spent engine oil