Application of Al species in coagulation/ultrafiltration process: Influence of cake layer on membrane fouling

The membrane fouling is a challenge for the application of ultrafiltration, one of which the cake layer is the main influencing factor. However, the pros and cons of cake layer generated in the coagulation-ultrafiltration (C-UF) process needs to be explored. This study was carried out to investigate that the effect of a cake layer on the membrane fouling behavior with three Al species coagulants for different effluents. The results indicated that the fouling mechanisms of cake layer under different effluents conditions were diverse due to the particle characteristics. The Al hydrolysis that accompanied by the interaction between Al species coagulants and the -OH/-COOH functional groups of humic acid were conducted, and the effluents of Al-a presented lighter membrane fouling. Meanwhile, the components mainly trapped by the membrane were soluble microbial products, protein, polypeptides and amino acid-like materials during C-UF process, because of the decrease in the proportion of fluorescence response. For the less/compact cake layer (system 2), the average of the external and internal membrane resistances were about 25 x 10(10) m(-1) and 21 x 10(10) m(-1), respectively, which caused severe membrane fouling. It was concluded that the poriferous/loose cake layer could effectively alleviate membrane fouling by re-adsorbing some organic matters.