Effect of Bio-enhanced Streptococcus pyogenes and Enterococcus faecalis Co-culture on Decontamination of Heavy Metals Content in Used Lubricating Oil Contaminated Soil

Abstract

This study assessed the heavy metal decontamination potential of bio-enhanced Streptococcus pyogenes and Enterococcus faecalis co-culture in used lubricating oil-contaminated soil. The bacterial co-culture was isolated from the soil obtained from Dutse mechanic village, Nigeria. One thousand five hundred(1500) g of sterilized soil was intentionally contaminated with used lubricating oil at three levels. The sterilized soil was biostimulated with processed compost, powdered cocoa pod husk (PCPH), and powdered cattle dung (PCD). Afterward, the mixtures were bio-augmented with the bacterial co-culture (150 mL). The concentrations of Arsenic (As), Cadmium (Cd), Chromium (Cr), Nickel (Ni) and Lead (Pb) in the used lubricating oil contaminated soil were determined at the commencement, fifth and tenth week of the study. A factorial experiment which was laid out in a completely randomized design (CRD) was adopted. Results generated from the As decontamination potential of Streptococcus pyogenes and Enterococcus faecalis co-culture indicated that all the organic amendments significantly (p<0.05) enhanced its decontamination. At the fifth week, PCPH only enhanced the most Cd decontaminations (0.01020 mg kg-1, 0.00220 mg kg-1 and 0.00150 mg kg-1) compared with other organic amendments on 5%, 10% and 15% used lubricating oil contamination levels, respectively. At the tenth week, PCD only enhanced complete removal of Cd on all used lubricating oil contamination levels compared with compost and PCPH only, which attained complete removal of Cd on 5% and 15% of used lubricating oil contamination levels, respectively. The heavy metal decontamination potential of bio-enhanced Streptococcus pyogenes and Enterococcus faecalis co-culture witnessed in this study indicates its suitability in effecting bioremediation of heavy metal impacted environments.