Effect of aeration rate on membrane fouling alleviation in conventional and internal circulation membrane-coupled moving bed biofilm reactors.

A conventional membrane-coupled moving bed biofilm reactor (Mc-MBBR, R1) and an internal circulation Mc-MBBR (ICMc-MBBR, R2) were operated in parallel to investigate the effects of aeration rate on membrane fouling mitigation. With the aeration rates of 0.1, 0.2 and 0.4 m³/h, the concentration of mixed liquor suspended solids (MLSS) was 1,343 ± 112, 2,566 ± 150 and 2,156 ± 134 mg/L in R1, and the value was 1,523 ± 108, 3,426 ± 196 and 2,246 ± 151 mg/L in R2, respectively. Aeration in the membrane unit and internal circulation in MBBR unit not only increased scour and collision, but also changed the particle-size distribution, extracellular polymeric substances, molecular weight distribution and MLSS concentration. Generation of membrane fouling included two periods: smooth-increase stage and abrupt-increase stage. Particle size below 10 μm and molecular weight above 100 kDa played important roles in smooth-increase stage. Increase of aeration rate and decrease of MLSS concentration delayed the initial formation of cake layer, and the appearance of abrupt-increase stage would be postponed. In the abrupt-increase stage, the value of protein/polysaccharide showed negative correlation with dTMPr/dt and MLSS concentration showed positive correlation with dTMPr/dt. Finally, aeration in the membrane unit and the configuration of the internal circulation MBBR mitigated the membrane fouling effectively. [ABSTRACT FROM AUTHOR]