The microbiological decolorization of an industrial effluent containing a diazo-linked chromophore

Mixed bacterial cultures from a wide variety of habitats were shown to be able to decolorize the diazo-linked chromophore of a highly coloured industrial effluent from the manufacture of nitrated stibene sulphonic acid. Decolorization was favoured by strictly anaerobic conditions and highly proteinaceous media. 10% v/v dilutions of the effluent with initial absorbances of 100 units at λmax were rapidly decolorized—ca. 85% in 2 days. When decolorized effluent was exposed to air it slowly developed a different colour which absorbed light more strongly in the visible region. The mechanisms involved in these processes and their implications for treatment of coloured effluents are discussed.