Chapter 22 - Microbial chromium removal as sustainable water treatment strategy

Abstract

Various industrial activities result in the discharge of chromium-contaminated effluents which is a potential threat to the environment and health. Among different species of chromium, its hexavalent form Cr (VI) is more toxic due to its solubility and ease of diffusion through the cell membrane. It is carcinogenic, teratogenic, and mutagenic unlike its trivalent counterpart Cr (III) which is relatively insoluble in water and nontoxic. There are conventional processes for chromium removal like chemical precipitation, coagulation/flocculation, electrochemical treatment, ion exchange, and membrane filtration. However, they are inefficient in removing Cr (VI) when high concentration or large volume of effluent is concerned. In view of the background, this chapter elaborates the promises of microbial process for bioremediation of chromium. Various bacteria like Acinetobacter baumannii L2, Arthrobacter crystallopoietes ES 32, Bacillus megaterium, Bacillus sp. KCH3, Cellulosimicrobium funkei AR6, Microbacterium sp. MP30, Pseudomonas sp. GT7, etc., with promising chromium removing potential are discussed. Further, chromium removal by several fungi like Aspergillus niger, Candida tropicalis, Fusarium oxysporum (NCBT-156), Hypocrea tawa, Mucor racemosus, Neurospora crassa, and many others is also detailed. Microbial mechanisms like biosorption, bioaccumulation, and biotransformation employed for metal removal and toxicity reduction are also discussed. Finally, the promises of developing bioreactor-based optimized bioprocess for Cr (VI) removal are emphasized that can revolutionize the future of water treatment process to ensure clean and safe water.