Harvesting of Microcystis aeruginosa using membrane filtration: Influence of pore structure on fouling kinetics, algogenic organic matter retention and cake formation

Abstract

Different membrane pore structures can affect filtration characteristics and membrane fouling during membrane harvesting of algae suspensions. In this study, four membrane materials with different pore structures (MC-5, PC-3, PVDF-5, and PVDF-100KDa) were employed to filter Microcystis aeruginosa suspensions to compare their filtration characteristics, retention of algogenic organic matter and membrane fouling. The correlation between membrane performance and pore structure characteristics, such as pore size, porosity, surface free energy, zeta potential, and surface pore area, were analyzed by a redundancy analysis method. The results revealed that PVDF-100KDa had the lowest deionized water flux compared with the microfiltration membranes due to its smaller pore size, and its high retention of organic matter aggravated membrane fouling. In addition, the track-etched single-pore PC-3 membrane exhibited fast flux decline and the highest cake layer resistance. PVDF-5 had strong adsorption capacity for aromatic protein-like compounds, which can increase irreversible fouling. Overall, MC-5 exhibited the best average flux and better flux recovery with a lower retention of organic matter and the maximum roughness observed by optical coherence tomography. For further insight, a conceptual model was proposed, which clarifies the effect of pore structure on fouling kinetics, algogenic organic matter retention and cake formation and thus provides valuable guidance for the development of membrane harvesting of algae suspensions.