ABSTRACT

Abstract

Heavy metals emanating from anthropogenic activities which have the penchant for polluting the environment have been documented as imminent residues synonymous with spent engine oil (SEO). This study was staged to evaluate heavy metal decontamination potential of Pseudomonas aeruginosa and Alcaligenes faecalis co-culture isolated from spent engine oil polluted soil in Dutse Mechanic village. About 1.5 kg of autoclaved soil was artificially contaminated with SEO at three levels. Subsequently, the sterilized soil was supplemented with the same quantity (150 g) of biostimulants, compost, powdered cocoa pod husk (CPH), and powdered cow dung (CD). Successively, each mixture in the experimental bag was bioaugmented with 150 mL bacterial inoculants. Concentrations of heavy metals; Cadmium (Cd), Arsenic (As), Nickel (Ni), Lead (Pb) and Chromium (Cr) were determined at the beginning, 5^th and 10^th week of the study. The factorial experiment was laid out adopting a completely randomized design (CRD). Results obtained indicate that at the 5^th week, compost and powdered CD only enhanced more reductions (0.008 mg kg^-1) of Cd compared with powdered CPH only on 5% SEO contamination level while compost enhanced the most reductions (0.004 mg kg^-1 and 0.005 mg kg^-1) of Cd on 10% and 15% SEO contamination levels respectively. At the 10^th week, both compost and powdered CPH only enhanced complete removal of Cr compared with other biostimulants. At the 10^th week, powdered CD only recorded complete removal of Pb, powdered CPH only enhanced further reduction (0.005 mg kg^-1) and compost recorded the most Pb reduction (0.012 mg kg^-1) compared with other biostimulants on 5%, 10% and 15% SEO contamination levels respectively (P< 0.05). Due to the significant heavy metal decontamination prowess of the bacterial inoculants employed in this study, biostimulation of these hydrocarbonoclastic bacteria is recommended with a view to expunging heavy metals inherently detected in polluted environments.

Keywords: Spent engine oil, heavy metals, soil, bacterial co-cultures, biostimulation,

decontamination.