EFFECT OF PHYSICAL PARAMETERS ON THE MICROFILTRATION OF WINE ON A FLAT POLYMERIC MEMBRANE

This paper investigates the microfiltration of unfiltered red and white wines through organic polyvinylidene difluoride membranes in plate and frame systems. Various pore sizes between 0.1 and 3 mu m were first tested using a small laboratory unit and it was found that 0.4 mu m pores gave the best compromise between turbidity and flux requirements. Tests with membrane areas between 1 and 2 m(2) were carried out in a modular plate and frame system in which both gasket thickness and parallel vs. series arrangements of compartments can be modified. With red wine the permeate flux is almost independent of fluid velocity but increases linearly with transmembrane pressure, reaching 501h(-1) m(-2) at 3 bar. The permeate flux is larger in a turbulent regime than in a laminar one at the same velocity. With white wine, the permeate flux is higher and increases almost linearly with velocity reaching 1701h(-1) m(-2) at 2 bar and 3.6 ms(-1). The turbidity of the permeate was generally below 0.5 NTU for both white and red wines while initial turbidity was above 150 NTU for red and above 50 NTU for white. When several membrane compartments are placed in series, the output of the downstream compartment is reduced by 10%-15% compared with that of the upstream one owing to the drop in transmembrane pressure.