Performance and fouling characteristics in a membrane sequence batch reactor (MSBR) system coupled with aerobic granular sludge

The treatment performances and membrane fouling parameters of a membrane sequencing batch reactor (MSBR) used to treat synthetic wastewater were studied over 300 days. Aerobic granular sludge ranging from 500 to 1000 µm in particle diameter was cultivated after a period of regulation in operating conditions. The MSBR with aerobic granules achieved a high removal efficiency of pollutants. The emergence of aerobic granules in the MSBR system improved the membrane performance, as indicated by the fouling rate being maintained below 0.1 kPa d− 1 when the MLSS concentration was greater than 18 g L− 1. The change in granule size and improved sludge settleability played an important role in sustaining the membrane permeability. Specifically, the reduced SVI led to a decrease in the supernatant TOC concentration that corresponded to a slower rise in TMP and less membrane fouling. Proteins were the primary components of EPS, while polysaccharides constituted a higher portion in SMP. In addition, the relative hydrophobicity (RH) and zeta potential increased in the sludge, while the protein to carbohydrate ratio (P/C) of both EPS and SMP increased after the formation of aerobic granules. These changes also enhanced the filterability of the mixed liquor.