Process Duration and Water Consumption in a Variable Volume Diafiltration for Partial Demineralization and Concentration of Acid Whey

Process duration and fresh water consumption were determined (experimentally and statistically) for variable volume diafiltration (VVD) of cottage cheese through a flat sheet membrane (0.046 m2). The VVD process was performed at two volume decreasing ratios (α = 0.75 and α = 0.5). The VVD-0.75 process lasts much longer than the VVD-0.5 process if the same concentration degree is required. The VVD-0.5 process lasts longer than the VVD-0.75 process if it is aimed to achieve the same purification degree. At low purification degrees, both processes require similar quantities of fresh water, but better demineralization is possible after higher dilution, which is typical of the VVD-0.75 process. The mathematical model applied in estimating the duration of the process proved very accurate, which cannot be said about the fresh water consumption model.