Bio-enhanced removal of hydrocarbon contents from spent engine oil contaminated soil using Staphylococcus aureus and Bacillus cereus co-culture

The study assessed the removal of total petroleum hydrocarbon (TPH) and polyaromatic hydrocarbons (PAHs) from spent engine oil (SEO) contaminated soil through bioenhancement of bacteria isolated from SEO polluted soil. Sterilized soil was subjected to a three level of SEO contamination before the addition of sterilized biostimulants including powdered cow dung (CD), powdered cocoa pod husk (CPH) and compost (made from fresh CPH and CD). Bacterial inoculum being Staphylococcus aureus and Bacillus cereus co-culture (150 mL) was added to the mixture in polyethylene bags. It was a factorial experiment that was laid out in a completely randomized design (CRD). The TPH and PAHs were estimated in the first day, fifth week and the tenth week that the room incubation lasted. Results generated from the influence of biostimulants on TPH and PAHs degradation potential of the bacterial co-culture showed that degradation of the hydrocarbon contents was significantly enhanced (p < 0.05). At the tenth week, compost enhanced the most TPH reductions (315 and 380 mg kg–1) compared with other biostimulants on 5% and 15% SEO contamination levels, respectively. Compost equally enhanced the most PAHs reductions (48.8, 39.6 and 94.6 mg kg–1) compared with other biostimulants on 5%, 10% and 15% SEO contamination levels respectively. However, the quantity of SEO contents degraded was significantly higher in the bioaugmented and biostimulated soil samples compared with the control employed. The technology adopted in this study can be effectively employed for the bioremediation of petroleum hydrocarbon related pollution.