A pilot-scale submerged membrane bioreactor (MBR) was used to treat the bathing wastewater for more than 90 d. Several factors affecting membrane fouling were studied, including the variation in transmembrane pressure (TMP), changes in extracellular polymeric substance (EPS), and distribution of membrane resistance (R). The relationships between R and EPS concentration were found to be R = 0.00008(EPSS)2.915 in the mixed liquor (EPSS) and R = 0.2853(EPSm) - 0.824 on the membrane surface (EPSm). The constant resistance of the clean membrane (Rm), the resistance due to concentration polarization (Rp), the cake layer resistance (Rc), and the resistance due to pore blocking (Ri), were 0.006%, 20.15%, 54.13%, and 25.72% of R, respectively. The results indicated that Rc had the greatest contribution to the total membrane resistance. The obtained membrane resistance model was R(t) = 4.609 × 108(1 + 0.01t)0.5. Molecular-based methods (polymerase chain reaction-denaturing gel gradient electrophoresis (PCR-DGGE) and ?uorescent in situ hybridization (FISH)) were used to study the bacteria attached on the membrane. The 16S rDNA gene sequence analysis suggested that certain phylogenetic group of bacteria, for example, Pseudomonas sp. and Nitrobacter sp., might have contributed to the formation of membrane on biofilms.
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