Bioremediation of heavy metals in spent engine oil-contaminated soil using mycorrhiza and cattle rumen digesta

Spent engine oil (SEO) is a complex mixture of petroleum hydrocarbons, heavy metals, and chemical additives and its contamination of agricultural soils poses severe challenges to soil health and fertility. The traditional remediation techniques have cost implications. Nevertheless, bioremediation is a cost-effective and sustainable remediation strategy. The aim of this study was to determine the efficacy of mycorrhizae and cattle rumen digesta in remediating heavy metals (Cr and Cu) in SEO-contaminated soil. Mycorrhiza, cattle rumen digesta and SEO were at two levels each. Data on Cr and Cu concentrations, bacterial and fungal populations were collected and analyzed using ANOVA at α 0.05. The results of the study reveals that mycorrhiza and cattle rumen digesta application yielded significantly higher bacterial and fungal populations leading to significant (p<0.05) reductions in Cr and Cu concentrations in SEO-contaminated soil. The combined application of mycorrhiza with 40 g/pot cattle rumen digesta had significantly (p<0.05) lower Cr and Cu concentrations compared to single application of either mycorrhiza or cattle rumen digesta. Mycorrhiza and cattle rumen digesta are therefore recommended for use in bioremediation of Cr and Cu contaminated soil.