Examining the Effect of Brewery Effluent Fertigation on Bioremediation of Heavy Metals from Crude Oil-contaminated Soil

The application of biostimulants to crude oil-contaminated soils enhances the proliferation of indigenous soil microorganisms. Brewery effluent (BE), one of the largest brewery wastes in volume, is scarcely used as a biostimulant despite its rich rate-limiting nutrient content. This study evaluated the effect of BE on the proliferation of hydrocarbon-utilising microbes and their potential in the removal of heavy metals from crude oil-contaminated soil. This study was carried out in the Research Farm of Rivers State University, Port Harcourt in the Niger Delta region of Nigeria. Simulated crude oil contaminated soil was fertigated with various volumes of BE, giving soil-crude oil-BE mix ratios of 8:1:0, 8:1:0.5, 8:1:1, and 8:1:1.5 and labelled, reactors A, B, C, and D, respectively. The experimental setup was a complete randomised block design of 4-triplicate reactors, including the control (A). The treatment lasted for 60 days. Soil samples were analysed for electrical conductivity (EC), pH, and hydrocarbon-utilising microbes using standard analytical methods. Heavy metals, including Cd, Cr, Cu, Ni, Pb, and Zn, were also analysed by Atomic Absorption Spectrophotometer. A one-way Analysis of Variance (ANOVA) was conducted to examine the impact of the different BE mix ratios on crude oil-contaminated soil. Results of the study showed that soil pH, EC, and heavy metal percentage removal increased with treatment duration and volume of BE. The order of microbial count for the soil samples was similar to the metal removal efficiency (D > C > B > A) indicating that increased microbial population increased chemosorption active sites for heavy metal biosorption. The order of removal efficiency for individual metals was Ni > Cd > Pb > Zn > Cu > Cr with 99.5%, 98.4%, 87.5%, 79.9%, 79.6%, and 75.6%, respectively. Heavy metal removal efficiency was linearly related to remediation duration and volume of BE applied. This suggests that BE is a good biostimulant for the bioremediation of heavy metals in crude oil-contaminated soil.