Application of biological methods in decolorization of azo dye containing wastewaters

A variety of synthetic dyestuffs released by different industries pose a threat to environmental safety. Azo dyescomprise huge amount of dye wastewater because of their extensive use in thetextile, paper, food, leather, cosmetics and pharmaceutical industries. These compounds are generally recalcitrant to biodegradation due to their xenobiotic and stable nature. There has been exhaustive research on biosorption and biodegradation of these resistent dye wastewaters. The ability of microorganisms and their degrading enzymes to decolorize dye containing wastewater or their adsroption has led to biological methods that could be recognized as an effective and appropriate alternative to conventional purification methods. Biological removal of dyes from wastewater of textile and dyestuff manufacturing industries offers distinct advantages over the commonly used chemicals and physical methods such as mineralization and conversion of dyes to harmless inorganic compounds )like carbon dioxide and water( and also formation of less sludge. In this paper evaluation of various biosorbents such as fungi, bacteria, algae and yeast, which are capable of decolorizing dye wastewaters is conducted. Algal and fungal biomasses have shown excellent color removal capability in comparison to other biosorbents. Also, comprehensive discussions about different mechanisms involved and the effects of various factors on dye wastewater decolorization is also performed.