A simulated textile wastewater containing the azo dye AR14 was supplied to two anaerobic/aerobic SBR systems, one inoculated with activated sludge flocs and the other with aerobic granules.The flocculent SBR system operated in 8-h cycles but this duration could be reduced to 6 h in the granular system, mainly dueto the excellent settling properties of the aerobic granules. Afteraround 40 days of operation with a SRT of 15 days, the mixed liquor of the flocculent SBR (FSBR1 and FSBR2) reached a TSS content of5 g L−1. In the granular SBR (GSBR1 and GSBR2), the dense and fast settling aerobic granules progressively accumulated in both SBR,reaching a TSS content of 13 g L−1 with negligible biomass washoutlevels. Consequently, SRT values higher than 30 days were attainedin the granular SBR. A comparison between the overall dissolved COD removal yields of the four SBR during 41 days of operation is presented in Fig 1
The total dissolved COD removal yields attained in FSBR1 andGSBR1 were similar to those observed in the corresponding dye free controls, FSBR2 and GSBR2, respectively, suggesting that the presence of the azo dye did not affect the overall COD removal in the flocculent or in the granular systems. However, higher COD