The technologies of aerobic granular sludge sequencing batch reactor (SBR) and membrane bioreactor (MBR) were combined in an attempt to develop an aerobic granular sludge membrane bioreactor (GMBR). The objectives were to determine the mechanisms controlling the formation of granules and granule stability in the GMBR as well as to evaluate the filterability of the granular sludge. The GMBR was operated in parallel with a SBR. In the SBR granulation was achieved after 16 days while no granulation was observed in the GMBR even after 10 weeks of operation. Filterability of the GMBR biomass, which was dominated by flocs, was compared with the filterability of granules cultivated in the SBR. The results showed no significant difference in filterability of granular sludge versus flocular sludge. Also, the clean water flux obtained after filtering flocular sludge was higher than after filtering granular sludge, suggesting that irreversible membrane fouling caused by adsorption of soluble extracellular polymeric substances (sEPS) was more important in the granules than in the flocs. According to the results of this study, granular sludge might not be able to alleviate the membrane fouling problem in MBRs. Furthermore, it could lead to irreversible membrane fouling in a major extent than that produced by conventional flocular sludge
