Decolorization of an azo dye by unacclimated activated sludge under anaerobic conditions

Studies on the reductive decolorization of a complex azo dye, Reactive Red 3.1, were made as part of the development of a practical approach to better exploit the metabolic potential of biomass in wastewater treatment. Decolo rization was achieved at low and variable rates by mixed microbial cultures under various environmental conditions, including low pH and high salt con centration. It was caused by reductive cleavage of the azo bond to yield tw o aromatic amines. More reliable and effective decolorization rates, of up to 20-30 mg l(-1) h(-1), were given by unadapted activated sludge, (6 g l(- 1)) incubated with 400 mg l(-1) of Reactive Red 3.1 under anaerobic conditi ons. Decolorization also occurred best in static conditions. (C) 2000 Elsev ier Science Ltd. All rights reserved.