Chromium in Environment, Its Toxic Effect from Chromite-Mining and Ferrochrome Industries, and Its Possible Bioremediation

Chromium has long been recognized as a toxic, mutagenic and carcinogenic metal. It is toxic to microorganism, plants, animals and humans. Chromium exists in environment in two stable forms: Cr(VI) and Cr(III). Cr(III) is less toxic and insoluble, while Cr(VI) is extremely toxic and highly soluble. Chromium is used in many industrial applications, but it poses a threat to local environment. The effluents and solid wastes from the mining, chrome-plating, leather-tanning, and dye-manufacturing industries are high in chromium concentration and identified as a major health hazard because of pollution to the environment. Industrial waste is used in landfilling, which causes the seepage, and the leaching of toxic chromium from soil into water bodies poses a threat to the environment. Ferrochrome industry is one of the biggest contributors of the chromium pollution to the water bodies. South Africa has the world's largest chromium reserve. The waste materials produced by ferrochrome industry are slag, dust and processed water. These wastes have high chromium concentration that can cause pollution to the environment. Inhalation is the major exposure route of the Cr(VI) toxicity in humans. The bioremediation of Cr(VI) to Cr(III) in the polluted site is a cost-effective and ecofriendly solution for preventing chromium detoxification. Bioremediation can be in situ or ex situ, and choice of remediation method depends upon the extent of pollution and the nature of the site. This paper summarizes the chromium pollution caused by ferrochrome industries, current remediation method adopted by ferrochrome industries, and the possible new methods for effective bioremediation. This paper focuses mainly on bioremediation techniques to convert the high-toxic form of chromium to less-toxic and mobile form of chromium.