Heavy metals in crude oil-polluted soil and the remediation potentials of heat-stable biocatalytic remediation cocktail (HBRC) and its residue

Abstract

This study investigated heavy metals in crude oil-polluted soil and the remediation potentials of Heat-Stable Biocatalytic Remediation Cocktail (HBRC) called Garbage Enzyme and its residue (HBRCR). The Crude oil-contaminated soil sample was collected from Agbura Community, Yenagoa, Bayelsa State. HBRC was produced from three substances; water, fruit skin (orange, pineapple, watermelon, plantain and banana peels) and brown sugar in a ratio of 10: 3: 1 respectively. They were subjected to fermentation for 90 days. The soil sample was divided in to ten groups. Group 1 served as the control, Group 2 untreated while Groups 3 to 10 were given different treatments for 180 days. Heavy metals (Hg, Cr, Cd, Pb and Ni) concentrations were analyzed using an Atomic Absorption Spectrophotometer (AAS). Significant decreases at p≤0.05 of Hg, Cr, Cd, Pb and Ni were observed in groups 3 to 10 when compared to groups 1 and 2. Results obtained from the study revealed that there was a decrease in concentrations of various heavy metals. Hg concentrations in Groups 1 to 10 were reduced by 0.00%, 9.97%, 76.36%, 63.61%, 65.61%, 60.93%, 83.17%, 69.50%, 68.41% and 79.35% respectively. Similarly, Cr concentrations in Groups 1 to 10 were reduced by 19.73%, 11.78%, 96.05%, 36.17%, 51.79%, 74.45%, 92.09%, 55.07%, 85.12% and 80.70% respectively. Also, Cd concentrations in Groups 1 to 10 were reduced by 40.00%, 26.67%, 100.00%, 98.02%, 100.00%, 86.36%, 100.00%, 100.00%, 100.00% and 100.00% respectively. In like manner, Ni concentrations in Groups 1 to 10 were reduced by 18.52%, 33.68%, 45.48%, 69.55%, 47.11%, 44.05%, 51.05%, 64.57%, 65.49% and 65.41% respectively while Pb concentrations in Groups 1 to 10 were reduced by 8.09%, 3.32%, 48.05%, 55.74%, 60.77%, 55.32%, 100.00%, 41.25%, 100.00% and 63.54% respectively. The Results from this study showed that HBRC and HBRCR elicited significant removal of heavy metals from crude oil-contaminated soil and they could be used as remediation agents for heavy metals.