Enhancement of PVDF membrane anti-fouling ability based on critical flux: Effects of fabrication parameters and membrane properties

Anti-fouling behavior of polyvinylidene fluoride (PVDF) membrane in membrane bioreactors (MBRs) can be enhanced by improving its physicochemical properties. To evaluate the membrane anti-fouling ability, this study comprehensively investigated the effect of variation in fabrication parameters (i.e. PVDF and polyvinylpyrrolidone (PVP) concentration, scraper clearance and evaporation time) on membrane properties, especially critical flux. The result illustrated that membrane properties could be significantly improved (p < 0.05) with a lower PVDF concentration, appropriate PVP concentration and prolonged evaporation time. Under the optimal parameter (9 wt% PVDF, 5 wt% PVP, 40 s evaporation time and 200 mu m scraper clearance), the membrane was obtained with porous structure (68.16 f 0.49 % of porosity), guaranteed permeability (3316.85 f 32.74 L/(m(2)& sdot;h) of pure water flux) and improved hydrophilicity (59.33 f 0.39 degrees of contact angle). The membrane with high porosity and pure water flux was more likely to enhance its critical flux through correlation analysis, and the optimized membrane also achieved the highest critical flux (42.35 f 4.65 L/(m(2)& sdot;h)). Its anti-fouling performance was verified successfully in anaerobic-anoxic-oxic MBR system compared with the selected commercial membrane for long-term operation (41 days) and lower membrane resistance (214.52 x 10(7) m(-1)).