Membrane fouling by sodium alginate in high salinity conditions to simulate biofouling during seawater desalination

•During sodium alginate microfiltration, fouling mechanisms depend on SA concentration.•Na+ (0.6 M) reduces membrane fouling during SA microfiltration.•Ca2+ and Na+ together leads to quick deposit formation regardless of SA concentration.•In low ionic strength conditions (0.03 M) binding of SA by Ca2+ decreases.•In high ionic strength conditions (0.6 M), SA is highly rejected by MF membrane.

This study aims to better understand biofouling by algal organic matters (AOM) during seawater pretreatment by microfiltration (MF). To simulate AOM biofouling, sodium alginate (SA) solutions with three different concentrations (2, 20 and 50 ppm) were filtered in dead-end mode with MF membrane. A modelling approach with blocking laws was used to identify the fouling mechanisms behind flux decline with time. The effect of SA concentration and cations such as Na+ (0.6 M) and Ca2+ (0.015 M) addition to SA solution on fouling mechanisms was studied. While for low SA concentration (2 ppm), fouling occurs within two phases: a pore constriction phase followed by cake formation phase, for high SA concentration (50 ppm), fouling occurs within only one phase controlled by cake formation. The addition of Na+ (0.6 M) or Ca2+ (0.015 M) to SA solution mitigates membrane fouling, however, the addition of both cations enhances fouling by formation of dense cake layer on membrane.

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