The performances of AGS and flocculent anaerobic/aerobic SBR systems in the treatment of dye-laden textile wastewaterwere compared. Similar decolorization profiles with high yields(around 75–80%) were attained in both AGS and flocculent systems. However, higher anaerobic and overall COD removal yields were observed in the AGS SBR. Additionally, the apparent inhibitory effect of the azo dye toward anaerobic COD removal detected inthe flocculent SBR was not present in the AGS SBR. On the otherh and, yeast-based toxicity assays revealed that the decolorization of azo dyes under anaerobic conditions results in the formation of reaction products that can have a higher cyto- and genotoxicity potential than the original dye and can be presumably attributed to colorless aromatic amines. The detoxification of the wastewater containing these products was only observed during the aerobic reaction phase of the AGS SBR system after 70 days of operation.The results from this study support the potential application