High concentration of skim milk proteins by ultrafiltration: Characterisation of a dynamic membrane system with a rotating membrane in comparison with a spiral wound membrane

The purpose of this work was to characterise the ultrafiltration of skim milk with a dynamic system with a rotating membrane regarding flux in milk protein concentration. The flux of the dynamic system showed a maximum at medium rotational speeds, probably due to the permeate backpressure or a shift in the deposited particle size range to smaller particles above a critical rotational speed. The flux increased almost linearly up to a transmembrane pressure (TMP) of 100 kPa. At higher TMP, the curves levelled off, especially at higher protein concentrations. The dynamic system was less limited by the increasing retentate viscosity and reached significantly higher volume reduction ratios (VRR) as compared with a spiral wound module (SWM). SWM are suitable to achieve VRR <5-6 before a dynamic system, possibly in combination with tubular ceramic membranes, could be used to achieve higher VRR >8.