Fouling mechanisms of membrane filtration of mixed microalgal biomass grown in wastewater

Membrane fouling mechanisms of the filtration of a mixed-culture microalgal biomass grown in real wastewater were investigated using crossflow filtration experiments. The results of flux measurements, scanning electron microscopy (SEM) and atomic force microscopy (AFM) analyses for three membranes, two microfiltration (PES01 and PES003) and one ultrafiltration (UC030), showed that the UC030 membrane may be more appropriate for microalgae harvesting due to its higher steady flux rate and lower flux reduction during filtration compared to the initial flux (44% for UC030, compared to 86% for PES01 and 79% for PES003). It was also observed that the membrane resistance due to concentration polarization was the dominant membrane resistance in this study for all three membranes, constituting about 67%, 61% and 51% for PES01, PES003, and UC030, respectively. The next largest membrane resistance was provided by pore blocking, while the resistance provided by cake formation was found to be very small for all membranes (3%, 15% and 18% for PES01, PES003 and UC030, respectively), which were also supported by SEM and AFM analyses.