Decolorization of azo-reactive dyes and cotton-textile wastewater using anaerobic digestion and acetate-consuming bacteria

An anaerobic digestion technique was applied to azo-reactive dye aqueous solutions and cotton textile wastewater aiming at the color elimination. A batch-mode water-jacketed anaerobic reactor and acclimatized acetate-consuming bacteria initially derived from the anaerobic digester sludge of a municipal wastewater treatment plant were used for this study. Acetic acid solution and a pH-controller were utilized to maintain the pH at the desired level (6.6-7.2) while the temperature was kept constant at 37 degreesC using an external water-bath. Acetic acid also served as an external substrate (electron-donor) supply for the bacteria metabolism. Complete decolorization of all dye solutions was succeeded in 4-5 days of experimental run. The biodegradation ability of cotton textile wastewater was also examined without the addition of external substrate supply (acetic acid) resulting to poor decolorization results. However, anaerobic digestion of the same wastewater using the acetate-consuming bacteria and acetic acid as an external substrate supply lead to the complete decolorization of the wastewater in 4 days of experiment. (C) 2003 Elsevier B.V. All rights reserved.