Fouling mechanisms of model polymeric substances

Extracellular polymeric substances (EPS) and soluble microbial products (SMP) have been identified as the main foulants in membrane bioreactor (MBR) operation. For a better understanding of the fouling mechanisms of these substances, filtration of model solutions with submerged membranes was carried out. Filtration was conducted following the flux-stepping method. In this work alginate was used as a model for polysaccharide, bovine serum albumin (BSA) as a model for protein, and yeast (washed and unwashed) and bentonite were used for suspended solid contents. Fouling behaviours and rejection propensities were also assessed for one-component and two-component solutions and provided explanations for fouling mechanisms of carbohydrate and its interaction with protein and membrane in MBR systems. During the filtration of most foulants (except BSA), introducing the alginate increased the reversible fouling more than the irreversible one. In addition, a different behaviour was observed for the mixture of BSA and alginate. Fouling rate was also affected by the introduction of alginate. (c) 2007 Curtin University of Technology and John Wiley & Sons, Ltd.