Dynamic membrane behaviours during constant flux filtration in membrane bioreactor coupled with mesh filter

This study investigated the long-term filtration of mesh filter with the formed dynamic membrane in bioreactor. The trend of transmembrane pressure (TMP) variations highly corresponded to the thickness and compactness index of dynamic membrane. The dynamic membrane was fractionated by applying two cleaning protocols, that is, rinsing and chemical cleaning. The desorbed fraction, consisting of soluble microbial products (>70%), provided a stickiness surface for formation of consecutive biomass layer which featured a high concentration of extracellular polymeric substances (>75%). The chemical oxygen demand (COD) removal was 70%, 89%, and 92% for period of 0-26, 26-49, and 49-67 day, respectively, which indicated that further development of dynamic membrane increased the TMP without improvement in the effluent quality (TMP: 50-200 mbar, COD removal: 89%; TMP: 200-600 mbar, COD removal: 92%). The average NH4+-N and TN removal was about 76% and 21%, respectively. The effluent turbidity fell less than 2 NTU after 26 days of filtration.