Study On Surface Modification And Pollution Of PVDF Membrane In Membrane Bio-Reactor

Membrane bio-reactor has great effects on treating high-concentrated, difficult-to-decomposed, organic contaminants. However, there were inevitably membrane pollution problems in the operation. As the pollution was serious and membrane-separating was destroyed, resume of operation of reactors relied on replacing membrane modules, and this certainly would increase cost of reactors and intermit operation period. So producing anti-polluted membrane was the key for application of membrane technology. The aims of the paper were to alter characters of membrane surface and improve capability of anti-pollution by treating the surface of finished products.First, there were two treating methods about PVDF membrane surface :one was covering Fe(OH)₃ colloid in the surface of membrane by filtrating, the other was covering TiO₂ colloid by sol-gel. Under different treating conditions to treat membrane. the optimized term was obtained by measuring permeation flux as membrane crossed pure water, rejection rate and contact angles. Membrane was covered with Fe(OH)₃ colloid by orthogonal test under different pressures and concentrations ,the result showed that when room temperature was 25℃,pressure was 0．2MPa and concentration was 0．01%,the best membrane could be made. Membrane covered with TiO₂ was measured in different sulfonation time and different marinating time, and the optimized condition for making membrane were sulfonated for two hours and dipped in TiO₂ colloid for ten minutes.Second, through contrasting filtration of modificated and non-modificated membrane, flux variety during long runtimes and variety of effluent COD, NH₃-N, turbidity and chromaticity after filtrating were measured. The result indicated that flux of modificated membrane was better than non-modificated membrane. The contamination layer were observed by scan electron microscopic in the paper, we found that the contamination layer of modificated membrane was thinner than non-modificated membrane, and contaminated granules were lesser. Furthermore, by contrast of efficiency of resume after cleaning between modificated and non-modificated membrane, modificated membrane was better than non-modificated membrane, that was also indicated that modificated membrane had better anti-polluted effect.Third, the paper analyzed mechanism of modificated in the respect of resistance distribution. The result showed that both resistance of modificated and non-modificated membrane added, and the latter increased faster, long-term operation membrane hole were blocked more severely. Meanwhile, that resistance of modificated membrane was smaller illuminated that modification relaxed pollution. Terminal filtration of sludge rigidly accorded with sediment and filtration laws, even the process in the initial stage wasn't controlled by stop of membrane os in the filtration, it also corresponded with the result of resistance distribution. Membrane pollution were mostly caused by formation of filtration layer and gelatin layer.