A high concentration of poorly flocculating sus-pended matter in the wastewater is detrimental to the development of granular sludge. Also Hulshoff Pol et al. reported that in liquid wastes with a high fraction of finely dispersed suspended solids, the attachment of bacteria to the dispersed particles can lead to the wash-out of viable bacteria. According to Hulshoff Pol et al, a high concentration of dispersed inert solids is prejudicial to the granulation process because in the case that the surface area offered for growth is very big for the bacteria available, concentrated growth will be limited. As granulation is strongly dependent on bacterial growth, a reduced growth leads to a slow down in the granulation process.