Optimal Removal of Heavy Metals From Leachate Contaminated Soil Using Bioaugmentation Process

Bioremediation of soil contaminated with metals from leachate is a complex process because it requires understanding the microbial interaction common to such contaminated environment. Therefore, this study tried to enhance the reduction of some extractable metals such as Pb, Cu, and Al through bioaugmentation with inocula of bacterial species isolated from leachate-contaminated soil. Assessment of metal concentrations in the soil was carried out through characterization (US EPA 3050B test method). Furthermore, the persistent microbes were isolated from the contaminated soil before mixing the microbial culture in terms of combinations and concentration (1.3 ABS at 600 nm). The inoculum obtained was dispensed into the induced leachate-contaminated garden soil (10% v/w). A combination of all the isolated microbes recorded less efficiency, unlike the selective use of only three bacterial species (Lysinibacillus sp., Bacillus sp., and Rhodococcus sp.) which gave better metal removal efficiency to a significant level (p < 0.05); extractable Pb, Al, and Cu were reduced by 71, 72, and 86%, respectively. This indicates that just amending the concentrations of microbes do not give the optimal remediation potential of the microbes, rather selection is very important. Lysinibacillus sp., Bacillus sp., and Rhodococcus sp. were the only isolated Gram-positive bacteria that possibly influenced the metal removal efficiency when blended together as the bioaugmentation agent. The bioaugmentation process enhanced the reduction in concentrations of the heavy metals within the contaminated soil.