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Macrofiltration-A leap towards high efficiency microalgal harvesting: A case study using Scenedesmus acuminatus

Xiao, Jingrong, Liu, Rui, Yang, Li, Hu, Qiang, Zhang, Xuezhi
Algal research 2019 v.37 pp. 1-10
Scenedesmus, biomass, case studies, cellulose, commercialization, fouling, harvesting, microalgae, porosity, scanning electron microscopy, ultrafiltration
In order to develop efficient membrane based harvesting techniques to accelerate microalgal commercialization, macrofiltration membranes of mixed cellulose with pore sizes of 0.45, 1.2, 3, 5, and 8 μm were evaluated for Scenedesmus acuminatus harvesting. The influences of pore size on the changes in membrane flux and flux recovery were investigated, followed by a SEM analysis of the fouled membranes. The performance of S. acuminatus harvesting using the 5 μm membrane was then compared with an ultrafiltration membrane, with both operating under a cross-flow mode. Macrofiltration operated with dead-end mode was further developed to achieve higher flux and higher solid content in the harvested biomass. The results showed that the 5 μm mixed cellulose membrane achieved the highest average flux due to its excellent anti-fouling performance. SEM images revealed that the presence of non-cellular and cellular foulants were responsible for the fouling of the smaller sized membranes, and membranes larger than 5 μm, respectively. Macrofiltration membrane harvesting was more efficient when a dead-end rather than a cross-flow operation was used. The average flux from a multiple-times filtration cycle reached 1845 ± 105 L·m−2·h−1 for the dead-end operated 5 μm macrofiltration membrane, which was 16-fold higher than that obtained using a cross-flow ultrafiltration membrane (107 ± 14 L·m−2·h−1). The solid content of macrofiltration-harvested biomass was 24%. This high flux and high solid content achieved through macrofiltration represents a great leap towards high-efficiency microalgal harvesting.