BACKGROUNDUnderstanding how influent loads affect the microbial community may promote applications of aerobic granular sludge (AGS). Herein, performance and microbial community dynamics of the AGS were assessed with stepwise increasing influent loads. RESULTSAGS exhibited good structure stability and effective removal efficiency; when the influent load increased from 6.5 kg COD m(-3) d(-1) (0.255 NH4+-N m(-3) d(-1)) to 10.1 kg COD m(-3) d(-1) (0.455 kg NH4+-N m(-3) d(-1)). COD and NH4+-N removal efficiencies reached 97.1-97.9% and 84.5-98%, respectively. As indicated from the PCR-DGGE results, the microbial community and dominant species in the AGS also gradually evolved along with the increase of influent loads. A coincidence was observed, namely, three main distinct clusters of the phylogenetic tree appeared respectively in the three stages of influent loads. The microbial diversity attained a maximum in the medium loads stage. The identified bacteria mainly belonged to Proteobacteria, Actinobacteria, Bacteroidetes and Firmicutes. The dominant species were responsible for the AGS stability and pollutant removal. CONCLUSIONVariation in the influent load strongly affected the microbial community dynamics, and hence the AGS performance. These results and understanding could lead to potential improvements in guiding AGS wastewater treatment. (c) 2017 Society of Chemical Industry