Basic understanding of aerobic granular sludge (AGS) processes has mainly been obtained in laboratory-scale studies with simple synthetic wastewaters. Two approaches were applied here to make a step toward the comprehension of AGS systems treating real municipal wastewater. One approach consisted in increasing the complexity of the influent composition of an AGS sequencing batch reactor (SBR) fed with volatile fatty acids, the other in starting up four AGS SBRs with four different wastewaters. Nutrient removal could be maintained in the first approach and indications for a change in the population responsible for biological phosphorous removal were obtained (P-removal). The four reactors started up with different wastewaters showed different granulation behaviour and P-removal was impaired in the reactors fed with municipal wastewater. More detailed investigations of the microbial communities will allow to elucidate the reasons behind the observations made in this preliminary study.