Microbial Decolorization of Reactive Dye Solutions

The most widely used dyes for coloration of cotton textiles are from reactive class. However, the large amount of unfixed dye causes color in the wastewater, which is environmentally unacceptable. Decolorization of various commercially important reactive dyes in aqueous solutions was attempted by microbial treatment using the bacteria Proteus vulgaris and Proteus mirabilis, individually as well as in a consortium. Different parameters such as treatment temperature, pH, dye solution concentration, and the seed age of the bacteria were optimized to achieve maximum decolorization. Although both bacteria displayed good growth in a shake culture, the color removal was better in an anoxic static culture. The selected dyes were based on azo and anthraquinone chromophores and complete decolorization under optimized conditions could be achieved at a concentration of 30 mg/L. Good results were obtained also at dye concentrations of 60 and 90 mg/L.