A kind of algae, Chlorella sp., is concentrated using plane-sheet crossflow microfiltration in this study. The Chlorella sp. cells with sizes ranging from 3 to 12 µm were filtered using a 0.1 µm membrane made of mixed cellulose ester. The effects of operating conditions, such as crossflow velocity and trans-membrane pressure, on the filtration flux and cake properties were measured and are discussed. The filtration flux increased with increasing crossflow velocity and trans-membrane pressure. The overall filtration resistance is mainly contributed by the cake formed from the algae cells. The order of magnitude of the average specific filtration resistance of cake formed by Chlorella sp. is as high as 1013 m-1, and the cake compressibility is ca. 0.74. An increase in crossflow velocity led to higher wall shear stress which resulted in reduced cake mass.
A force balance model for cell deposition is applied to obtain the relationship between cake mass and operating conditions. The cake mass decreases linearly with the ratio of wall shear stress to filtration flux. The filtration flux can be estimated using the basic filtration equation once the cake mass and filtration resistance are analysed. The calculated results of filtration flux agree fairly well with experimental data.
