Ceramic ultrafiltration membrane experiments were performed using model solutions, which were representative of polymeric membrane foulants in drinking water treatment applications. Alginate and bovine serum albumin were used to represent biopolymers, silica to represent an inorganic colloid, and Aldrich humic acid was used to represent a natural organic matter fraction. Solutions were filtered at constant pressure in all possible combinations through a 300 kDa flat sheet ceramic membrane over one hour and flux decline curves were monitored. Silica significantly increased the rate of flux decline, however, the majority of it was generally recovered with a hydraulic backwash. Conversely, humic acid and BSA showed lower rates of flux decline, but most of the flux could not be recovered with a backwash pointing to significant and almost complete hydraulically irreversible fouling. The contact angle was also measured to assess the hydrophobicity of the virgin and fouled membranes. As expected the virgin contact angle was very hydrophilic and the only foulant that substantially increased the contact angle was BSA. Nevertheless, the addition of silica allowed the membrane surface to remain relatively hydrophilic. Despite similar average sizes of BSA and humic acid, the rejection of BSA was highest, possibly due to the potential for BSA to aggregate. The rejection for mixtures with BSA tended to be higher, but in the presence of silica rejection generally decreased.
展开▼
