Aerobic granular sludge (AGS) has demonstrated a lower fouling propensity than floc sludge in membrane bioreactors (MBRs) due to various hypotheses, including differences in particle size and the efficacy of physical scouring. However, controversy exists regarding the dominant cause of this lower fouling. Therefore, in this work, we systematically investigated the contribution of four potential mechanisms of AGS on membrane fouling alleviation in MBRs: 1) loosening cake layer
2) scouring of the membrane surface
3) regulating soluble microbial product (SMP) secretion
and 4) changing the rheology of the bulk solution. Our results showed that, regardless of granular size range, AGS hardly caused cake fouling due to its low hydraulic resistances (<
0.8 × 10