Recovery of membrane permeability after filtration of sago starch suspension by tangential flow filtration

Abstract

Sago starch is extracted from the stems of the sago palm, Metroxylon sagu, in south-east Asia. Sago starch processing generates approximately 20 tons of starch containing effluents that can be recovered and marketed to sustain a small-scale industry. Tangential flow filtration (TFF) using microfiltration membranes (MFM) has been demonstrated as an effective method for separating suspended solids in biological effluents. When TFF was applied to concentrate sago starch suspensions (SSS), membrane permeability and lifecycle were impacted due to frequent fouling. This study evaluated cleaning methods to recover the permeability and extend the lifecycle of MFM following TFF application. Polysulfone membrane filter cassettes of pore size 0.45 µm and surface area 0.1 m2 were each used to separate starch in 100 L of SSS. Following separation, six chemical and physical cleaning methods were tested at laboratory-scale and the degree of cleaning was measured by normalized permeate flux (NPF) and normalized water permeability (NWP). The results showed that soaking the membranes in a 0.2 M NaOH solution (up to 91%, (p<0.05) within the shortest time of 72 h, (p<0.05) was the best cleaning method. The procedure has been utilized to maintain and extend the lifecycle of the MFM for streams containing starch suspensions.