LAUSR

We investigated the effects of the inclusion of biological activated carbon (BAC) on membrane fouling in combined process of ozonation, coagulation and ceramic membrane filtration (O3 + PACl + CMF) for treating secondary effluent. Inclusion of BAC between ozonation and coagulation reduced membrane permeability. The normalized flux decreased to 90% of the initial value after 305 h of operation in O3 + PACl + CMF, while it decreased to 20% in combined process of ozonation, BAC, coagulation and ceramic membrane filtration. BAC not only decreased residual ozone that is helpful to mitigate ceramic membrane fouling, but also released microorganisms. In addition, BAC doubled the integrated fluorescence intensity of soluble microbial products (SMP), which cause irreversible fouling. The SMP produced and accumulated by microorganisms on the BAC bed likely flowed into the BAC effluent with the microorganisms. The proportion of SMP in the extracted foulant increased from 25% without BAC to 31% with BAC. Moreover, the inclusion of BAC nearly doubled the concentration of protein in the extracted foulant to 13 g/m2 and quadrupled that of carbohydrate to 6 g/m2. BAC was effective in improving the quality of ceramic membrane permeates and reducing health risk associated with formaldehyde and N-nitrosodimethylamine. However, the release of SMP from BAC accelerated membrane fouling in subsequent ceramic membrane filtration.