Assessing the bioaugmentation potentials of individual isolates from landfill on metal-polluted soil

Heavy metals from leachate are persistent pollutants in soil, especially when landfills lack liners and basic structural system that prevents overflow of leachate beyond restricted areas. It is not ideal to rely only on physical and chemical options for the reclamation/restoration of such contaminated soil. Therefore, it is imperative to adopt bioremediation through the enhancement of microbial potentials. The present study investigated the use of individual isolates for the remediation of soil contaminated by leachate-metals. This is a way to understand the discrete potentials of the gram-positive bacteria species. Environmental isolates taken from contaminated soil were used to remedy soil characterized with various concentrations of metals (Al, Cd, Cr, Fe, Ni, Pb and Zn). Treatments A, B, and C amended with Bacillus sp., Lysinibacillus sp., and Rhodococcus sp., respectively, demonstrated better metal reduction potentials than the control experiment (Treatment D; zero microbial amendment) that depended solely on natural attenuation. With the exception of Ni, the degree of reduction of other metals was less than 50% for all treatments. This study suggests that such result reflects the potential ability of the microbes to metabolize selectively in the presence of metal pollution. However, it is difficult for the individual microbes to attain higher metal reduction efficiency (above 50%) except when blended in the appropriate formulation.