Decolourization of azo dyes in textile wastewater by microbial processes

Abstract: Decolorization of Azo dyes in synthetic wastewater composition which is similar to real textile wastewater was carried out by microbial process. Experiments were performed in two continuous systems. Experiments were performed under anaerobic conditions in order to break the nitrogen bond of the azo group (-N=N-). A synthetic dye solution which contained 200 mg/L Reactive Black 5, 200 mg/L Procion Red MX-5B and 1 g/L yeast extract was prepared. In this study, living microorganisms were used to degrade the dyes in wastewater. Rice husks which contain bacteria and fungi were used in the reactors of continuous systems. The parameters tested on continuous system were wastewater composition, the number of reactors, the amount of yeast extract in wastewater composition, the wastewater flowrate, washing the system with wood chips solution, addition of yeast extract solution.  Results have shown that increasing the number of reactors, the retention time, the amount of yeast extract and washing the system with wood chips solution had positive effects for degradation of the dyes from wastewater. When the flowrate was increased the retention time has decreased so degradation of dyes has decreased but although the flowrate increased twice, % degradation hasn’t decreased as the same ratio. Therefore this result showed that this process can be worked for faster flowrates. Microbial process is a promising technology which might be used to treat wastewater containing azo dyes with good performance.