polymer storage. Similar results were already reported for a flocculent anaerobic/aerobic SBR systems operated in 24-h cycles supplied with the same carbon source [18]. Additionally, lower COD removal levels were observed in the dye-fed SBR (FSBR1, Fig. 4),suggesting an inhibitory effect of the azo dye and its reduction metabolites (aromatic amines) toward anaerobic COD removal. Typical color and COD removal profiles of a 6-h granular SBR cycle were selected and detailed in Fig. 5 for the 5-h anaerobic/aerobic reaction phase. Similarly to FSBR1, color removal occurred during the anaerobic reaction phase of GSBR1 and, in spite of presenting a slower decolorization rate, the same residual dye concentration of around 5 mg L−1(in terms of color equivalents) was attained at the end of the anaerobic reaction. The stable aromatic amine resulting from azo dye reduction was detected by HPLC (Fig. 3B, peak a) at the end of the anaerobic reaction phase(WWanaer). The operation of the AGS systems was extended up to100 days with similarly high anaerobic color removal efficiencies. However, towards the end of the experimental period (from day 71on), the stable aromatic amine (Fig. 3B, peak a) formed under anaerobic conditions (WWanaer) was apparently further bioconverted during the aerobic reaction phase, since peak a was not observed after the end of aeration (Fig. 3B, WWfinal). This can be attributed to the higher microbial diversity promoted by the high SRT values attained in AGS systems, which might allow the development of a microbial community with aromatic amine biodegradation capability [11].