STRATEGIES OF TOXIC CHROMIUM (VI) MITIGATION FROM TANNERY EFFLUENTS: A REVIEW

Hexavalent chromium i.e., Cr (VI) is highly toxic and carcinogenic it enters the environment through several anthropogenic activities. It is spuriously used in various industrial operations (leather tanning, electroplating, paint and pigment production etc.) because of its hardness and stability. It is found in industrial effluents in concentrations much above the prescribed limit of the World Health Organization (50 µg/L). Detection and remediation of chromium has been the subject of research of many scientists but many previous review works have been insufficient in comprehensive information. This review conveys the basic knowledge of chromate toxicity leading to physical discomfort and sometimes life-threatening illness including irreversible damage to the vital body system in humans. Conventional methods for removing toxic chromium ions (by chemical reduction followed by precipitation, ion- exchange and adsorption on activated coal, alum, kaolinite and ash) are costly for large-scale treatment. Microbial uptake followed by reduction of toxic Cr (VI) has become very successful due to its cost-effectiveness and use as a non-toxic agent. This is referred to as bioremediation. This review emphasises various strategies for hexavalent chromium bioremediation from contaminated water. This review article, therefore, tries to highlight this aspect of bioremediation of Cr (VI) from industrial effluents by native, indigenously resident chromate-resistant bacteria.