The sludge developed in such systems acquires high biomass concentration, better settling properties, high chemical oxygen demand (COD) removal efficiency, and good phosphorus removal capacity (de Kreuk et al., 2005b). In addition, simultaneous nitrification–denitrification can occur simultaneously in granules due to the bulk oxygen concentration and granule size (Mosquera-Corral et al., 2005). Aerobic granular sludge has mainly been cultivated using sequencing batch reactor (SBR) systems, some using airlift or bubble column reactors. Several lab scale studies have broadly identified the most crucial aspects influencing the development of aerobic granular sludge such as organic loading rate, settling time, hydrodynamic shear force and substrate composition (Adav et al., 2008). However, the formation of aerobic granular sludge is a challenging ecological process, in which many components need to be further inspected.