Changes in characteristics of soluble microbial products and extracellular polymeric substances in membrane bioreactor coupled with worm reactor: Relation to membrane fouling

The study focused on the membrane fouling mitigation observed in a membrane bioreactor (MBR) coupled with worm reactor system. During the operation time of 100 days, the transmembrane pressure (TMP) in the combined system was maintained less than 5 kPa, while the final TMP in the Control-MBR increased to 30 kPa. The changes in properties of soluble microbial products (SMP) and extracellular polymeric substances (EPS) after worm predation were investigated by means of various analytical techniques. It was found that due to the worm predation, the reduced amount of EPS was far more than the increased amount of SMP leading to a significant decrease of protein-like substances which were dominant in the membrane foulants. Except for the content decrease, worm predation destroyed the functional groups of simple aromatic proteins and tryptophan protein-like substances in EPS, making them have lower tendency attaching to the membrane in the combined system.

► A membrane bioreactor coupled with a new worm reactor was proposed.
► Effective membrane fouling mitigation in the MBR–SSBWR was obtained.
► The SMP generated by worm predation was degraded by the sludge in the MBR.
► The fouling mitigation resulted from content decrease and structural change of EPS.
► The EPS in MBR with predated sludge recycle had a lower fouling potential.