Effect of bacterial co-culture and organic amendments on the bioremediation of hydrocarbons in a soil contaminated with spent engine oil

Bioenhancement of hydrocarbonoclastic microorganisms with suitable nutrients has a huge impact in achieving positive bioremediation of polluted environments. This study was conducted to assess the bio-enhancing effect of some organic amendments on Streptococcus pyogenes and Enterococcus faecalis co-culture with a view to remediating spent engine oil (SEO) contaminated soil. Top soil (1.5 kg) was autoclaved and thereafter contaminated with SEO at three levels. The contaminated soil was inoculated with bacterial co-culture (150 mL) and subsequently bioenhanced with compost, processed cocoa pod husk (CPH) and cow dung. The factorial experiment was laid out in completely randomized design. Concentrations of total petroleum hydrocarbon (TPH) and selected polycyclic aromatic hydrocarbons (PAH) were estimated on the first day, 5th week and 10th week of incubation. Results obtained show that bacterial co-culture bioenhanced with compost produced the most significant TPH reductions (1318 and 261 mg kg-1) on 10% SEO contaminated soil at the 5th and 10th week respectively (p<0.05). Again, bacterial co-culture bioenhanced with compost produced the most significant PAH reductions (65.9 and 55.8 mg kg-1) on 10% SEO contaminated soil at the 5th and 10th week respectively (p<0.05). The significant bioremediation capabilities exhibited by the bacterial co-culture bioenhanced with organic amendments in this study has made these bioremediation agents potential candidates in remediating soils impacted with petroleum hydrocarbons.