MICROFILTRATION OF SWEET WHEY ON ALUMINA MEMBRANES - INFLUENCE OF THEHYDRODYNAMIC CONDITIONS ON THE FOULING

It is possible to characterize the fouling of a microfilter by evaluat ing the hydraulic resistance, as made of a series of partial resistanc es during microfiltration. Different hydrodynamic conditions (4 transm embrane pressures and 3 tangential flows) have been studied during whe y microfiltration on a system made of 4 alumina membranes (Ceraflo, 0. 22 mu m pore diameter) connected in series. The hydraulic resistance o f the membranes during concentration was considered to represent the f ouling produced by adsorption, pore blocking and concentration polariz ation. The effects of transmembrane pressure and tangential velocity w ere analysed in terms of how they affect the fouling. The total foulin g was significantly affected by the transmembrane pressure, the volume concentration factor and the tangential flow. The transmembrane press ure represented the most important factor. Bovine serum albumin retent ion was total, beta-lactoglobulin was retained at > 0.55 and alpha-lac talbumin at 0.40 at the beginning of the filtration. The results were examined in terms of how the fouling could affect the retention of the 3 main whey proteins. Retention was mainly affected by the transmembr ane pressure, by the solutes concentration and very little by tangenti al flow. The geometry of the filter and the experimental results sugge st that the fouling is mainly present inside the macroporous matrix. T he strong influence of the transmembrane pressure together with the we aker influence of the tangential flow on the parameters under study su ggest that fouling is mainly present in depth of the membrane. The fou ling would be due to the deposition of protein aggregates produced by the denaturing effect of the shear forces.