Two stage anaerobic/aerobic treatment of sulfonated azo dyes

Abstract Three lab scale, two stage reactor systems were used to study mineralization of three select sulfonated azo dyes. The dyes used in the study were Acid Orange 10, Acid Red 14, and Acid Red 18. The two stage reactor systems consisted of an anaerobic fixed‐film fiuidized bed reactor followed by an aerobic suspended growth activated sludge reactor. Results indicate dye decolorization levels of greater than 90% in the first stage for the two red dyes and greater than 65% decolorization for Acid Orange 10. There was very little additional decolorization in the second stage. Analysis of the metabolic intermediates indicate extensive (>99%) metabolite removal in the first stage for all three reactors. COD removal in all three reactors reached a steady state of approximately 85% in the first stage, with very little additional COD removal in the second stage.