Bioremediation techniques for heavy metal and metalloid removal from polluted lands: a review

Heavy metal accumulation increases concentrations of toxic contaminants in soil and the environment. They possess momentous warnings to ecosystems throughout the world. Industries and agricultural activities introduce heavy metals/metalloids into the ecosystem which affects agricultural crops and poses various potential health threats to humans and animals by entering the food chain. Therefore, neglecting its deleterious effects on the environment may worsen the current situation. Thus, the need for bioremediation is of paramount importance in the reclamation of polluted soils and lands. The technique involves the use of microorganisms, such as bacteria, fungi, and algae, to lower/remove the toxicity of contaminants in affected regions. It is an environment-friendly, efficient, and cost-effective solution for soil heavy metal and metalloid degradation in both in situ and ex-situ conditions. Microorganisms can also be genetically modified to be efficient for pollutant degradation. Better alternatives such as nanobioremediation, vermiremediation, and genetically modified microbes have been discussed in detail. These integrated approaches can be more effective than conventional approaches for the restitution of contaminated sites and reducing the toxicity of hazardous compounds. The present review will provide a deep interpretation of the various bioremediation techniques, their merits, and their limitations to the readers. It will also give insights on how these techniques can be implemented as future support to direct the global problem of metal remediation.