Influence of operating parameters and membrane materials on fouling of ceramic hollow fibre membranes

• Fouling behaviour of Al2O3 and SiC coated ceramic hollow fibre membranes was studied.
• Sodium alginate was used as model compound for extracellular polymeric substances.
• Influence of TMP, cross-flow velocity and Ca2+ concentration was investigated.
• Ca2+ addition leads to a significant change of filtration characteristics.
• CF experiments without Ca2+: SiC membranes show higher fluxes than Al2O3 membranes.

Fouling is one of the critical issues in membrane filtration, especially in the field of wastewater treatment. In this study sodium alginate was used as model compound for extracellular polymeric substances (EPS) in order to investigate the filtration and fouling characteristics of two newly developed ceramic hollow fibre membranes. The membranes studied have an asymmetrical structure consisting of an Al2O3 support layer, which is covered by an active layer. Two different active layers (Al2O3 and SiC) were studied under various operating conditions (dead-end and cross-flow filtration) by filtering sodium alginate solutions in the presence and absence of calcium ions. Fouling mechanisms taking place in dead-end mode were evaluated according to the cake filtration model. Dead-end filtration experiments revealed a change in fouling mechanisms from pore blocking and cake filtration in the absence of calcium ions to cake filtration only in the presence of calcium ions. Furthermore, cross-flow filtration experiments showed a big influence of calcium ions on the removal of the resulting alginate layer from the membrane surface due to shear forces induced by cross-flow. In the absence of calcium ions, the filtrate flux was found to depend strongly on transmembrane pressure (TMP) and cross-flow velocity, whereas in the presence of calcium ions, the chosen cross-flow velocities (1–3 m/s) were not sufficient to control alginate fouling. Cross-flow experiments without calcium addition revealed a higher flux for SiC membranes compared to Al2O3 membranes. For dead-end filtration experiments, no significant difference was found.