Membrane fouling control in a submerged membrane bioreactor with porous, flexible suspended carriers

Membrane fouling has been the main obstacle to the wide application of membrane bioreactors (MBR). A hybrid membrane bioreactor (HMBR) with porous, flexible suspended carriers was explored that was efficient in controlling membrane fouling, especially cake layers. In order to investigate the influence of suspended carriers on the filtration performance of the HMBR, two kinds of bioreactors - MBR and HMBR - were tested in parallel processing. In the short-term trials, the critical flux of HMBR increased by 20% and the cake resistance of HMBR decreased by 86% in comparison with MBR. During the long-term experiments, the increase rate of suction pressure for HMBR accounted for 30% of that for MBR, indicating that the degree of membrane fouling for HMBR was far lower than that for MBR. These observations revealed that suspended carriers play an important role in governing the filtration conditions and decreasing fouling resistance. In order to understand the influence of suspended carriers better on the system performance, several parameters such as cake layers of membrane surface, characteristics of the mixed liquor and filterability of the supernatant and the activated sludge suspension were investigated.