Effects of different pore sizes on membrane fouling and their performance in algae harvesting

Abstract

Membrane fouling caused by the deposition of algae cells and extracellular organic matter (EOM) is a major challenge for algae filtration. To find a suitable membrane pore size for microalgae harvesting, membranes with different pore sizes (0.03, 0.05 and 0.1 μm) were utilized in algae filtration in this study. The 0.1-μm membrane had the highest reversible fouling and the lowest irreversible fouling, in comparison with 0.03- and 0.05-μm membranes; thus, the 0.1-μm membrane was more suitable for algae harvesting than the 0.03-μm and 0.05-μm membranes. The molecular weight distribution of reversible EOM was primarily under 1 kDa whether irreversible EOM was over 100 kDa. Moreover, the larger the pore size, the more likely it was fouled by low molecular weight organics, regardless of reversible fouling or irreversible fouling. Fluorescence excitation-emission matrix spectra analysis showed that for protein-like and humic/fulvic acid-like substances, protein-like substances were more likely to cause reversible fouling while fulvic acid-like substances were more apt to cause irreversible fouling. The 0.1-μm membrane had better repulsion to fulvic acid-like substances than the 0.03- and 0.05-μm membranes, leading to less irreversible fouling. The results obtained from this study have many microalgae applications. For example, employing membrane technology in microalgae harvesting can help treat rivers and promote ecological restoration. In addition, applying this technique in sewage treatment plants will not only lead to wastewater treatment, but it will also acquire biomass resources.