Effect of solution chemistry on membrane resistance and flux decline

Variations in the membrane resistance due to the adsorption of cakes of Glutamicum onto polysulphone membrane surface were evaluated by measuring the change in the permeation of pure water at constant pressure. Relations giving the membrane resistance as a function of contact time at varying bulk concentration, pH and ionic strength were obtained, by analogy with adsorption laws. Static (zero pressure) and dynamic (crossflow) experiments were then compared in order to determine the effect of convective flow and electrostatic interactions on cell adsorption, irreversible resistance and flux decline. Although convective forces tended to increase the amount of material accumulated near the membrane surface, it was electrostatic interactions that strongly affected cell adsorption and irreversible resistance, as evident in the irreversible adsorption and resistance results from the static and dynamic cases. Cell-cell interactions affect the porosity of the cake layer on the membrane, while cell-membrane interactions affect irreversible adsorption onto the membrane. Solution chemistry affects both types of interactions, as evident in the increased irreversible resistance of the cake layer and irreversibly adsorbed cells at the isoelectric point of cells (IEP). Additionally, the irreversible resistance of the fouled layer is dependent on its compactness, which is directly affected by solution chemistry. The flux decline rapidly decreased after the first 10 minutes of filtration. Flux decline is more pronounced at the IEP of the cell, also indicating that fouling and adsorption are strongly dependent on cell-cell and cell-membrane interactions.