Microbial decolorization of reactive azo dyes in a sequential anaerobic–aerobic system

Abstract

A sequential anaerobic–aerobic treatment process based on mixed culture of bacteria isolated from textile dye effluent-contaminated soil was used to degrade reactive azo dyes Remazol Brilliant Orange 3R. Remazol Black B and Remazol Brilliant Violet 5R. Treating synthetic dye wastewater with the combination anaerobic and aerobic process showed that the majority of colors were removed by the anaerobic process, on the other hand the majority of chemical oxygen demand (COD) was removed in the subsequent aerobic process. Samples from combined anaerobic–aerobic system at the beginning of anaerobic process, after anaerobic process and after subsequent aerobic process were analyzed by high performance liquid chromatography (HPLC). The results suggested that under anaerobic conditions, the azo dyes were reduced and the aromatic amines were generated by the bacterial biomass. After re-aeration of the synthetic dye wastewater, these amines were further degraded by the same isolates. Thus, total degradation of reactive azo dyes was achieved by using an anaerobic–aerobic treatment.