Aerobic Decolorization of Reactive Azo Dyes in Presence of Various Cosubstrates

S. Padmavathy, S. Sandhya, K. Swaminathan, Y. V. Subrahmanyam, T. Chakrabarti and S. N. Kaul

Abstract
Azo dyes belong to the most important group of synthetic colorants. They are generally considered as xenobiotic compounds which are very recalcitrant to biodegradation. Azo dyes are deficient in carbon content and therefore decolorization is possible only under co-metabolic condition. In this work, attempts were made to degrade these dyes aerobically. The organisms which were efficient in degrading the azo dyes-Red RB, Remazol Red, Remazol Blue, Remazol Violet, Remazol Yellow, Golden Yellow, Remazol Orange, Remazol Black, were isolated from three different sources and were mixed to get consortia. The efficiency of azo dye degradation by consortia was analyzed in presence of various cosubstrates, such as glucose, starch, lactose, sewage and whey water, and their effects on dye decolorization have been studied. It was observed that starch was the best source of carbon for decolorization of reactive azo dyes. In presence of 250 mg l–1 of starch, all the reactive dyes decolorized within 24 hours with the reduction in COD in the range of 75.15–95.9 %. The COD reduction was the maximum in Remazol Orange and Red RB followed by Remazol Yellow, Remazol Violet, Remazol Black, Remazol Red, Golden Yellow and Remazol Blue. The decolorization of above referred dyes in presence of different wastewaters such as sewage and whey waste, showed that whey is the better cosubstrate for aerobic decolorization.

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Keywords
decolorization, Aerobic biodegradation, Azo dye, wastewater