Fluid dynamic gauging of microfiltration membranes fouled with sugar beet molasses

► A 45° Brix molasses solution was filtered using a 1.5μm polysulphone (Psf) membrane. ► Fluid dynamic gauging used to track the thickness of layer formed during microfiltration. ► Simultaneous measure of flux and deposit thickness obtained through full membrane operating cycle. ► Cleaning with the permeate line closed preferable to cleaning with the permeate line open. ► An initial increase and subsequent reduction in flux during chemical cleaning was seen. Fluid dynamic gauging (FDG) was used to track the thickness of the cake layer formed during the microfiltration of a 45° Brix molasses solution using a 1.5μm polysulphone membrane. A simultaneous measure of flux and deposit thickness throughout the full membrane operating cycle is reported. Asymptotic fouling thicknesses of ca. 100μm are developed after 30min of filtration. Accordingly, flux declines are severe at ca. 93%. Permeate line closed (PLC) operation leads to the complete removal of the deposit layer, and the recovery of 60% of the flux. However, permeate line open (PLO) operation leads to only a 50% flux recovery and an asymptotic deposit thickness of 10μm. An initial increase and subsequent reduction in flux during chemical cleaning has also been recorded for both acid and alkali cleaning regimes. Effective cleaning regimes for membranes fouled by molasses require an alkali stage followed by an acid stage.