Abstract:
Extracellular polymeric substances (EPS) are viewed as major fouling components during filtration of biological feeds in industry. However, very few studies investigated the fouling mechanisms of polysaccharides, one major group of macromolecules in EPS. In this work, cross flow filtration of Xanthan, Actigum CS 11 and Glucan, model polysaccharides, were carried out and analyzed using "resistance in series model" and "classical filtration laws". The Xanthan and Actigum CS 11 polysaccharide were obtained as powders and Glucan was obtained as concentrated aqueous suspension directly after fermentation step during manufacturing. The cake filtration model appears to fit the entire range of the ultrafiltration data for the polysaccharide solution at low concentration of 20 mg/1 with both "resistance in series model" and "classical filtration laws". It was difficult to detect/identify the predominant fouling mechanism with higher concentration of polysaccharide feed suspension with the use of above models. This indicates that the fouling could be the result of combination of two or more fouling mechanisms. For the two types of polysaccharide suspension it was observed that (i) the investigated model polysaccharides contained micro aggregates and the concentration of 'micro aggregates decreased during filtration runs and it is more pronounced with the aqueous polysaccharide suspension; (ii) viscosity analysis of polysaccharide in the retentate showed that the polysaccharide accumulated in the retentate and removed from the membrane surface and (iii) concentration measurements showed that the major portion of the polysaccharide remained in suspension.
