Performance enhancement and fouling alleviation by controlling transmembrane pressure in a vibration membrane system for algae separation

Although transmembrane pressure (TMP) has proven to be a significant factor in the separation of microalgae by the vibration membrane process, there is a lack of systematic research on this factor. This study introduced a multi-angle insight by analyzing hydrodynamic interaction acting on algae, compressibility of the cake layer, and quantitative evaluation of the membrane fouling performance to assess the relationship between TMPs and membrane fouling in the vibration membrane system. Supported by a collision-attachment model which illustrated the algae/membrane hydrodynamic interactions under different TMPs, the critical point in TMP was confirmed as at or beyond which membrane fouling became serious. Then, after analyzing the main membrane fouling indicators of polysaccharides and proteins, the results demonstrated that TMP had a greater effect on reversible fouling. Furthermore, using the theory of algae deposition, the study verified that the increase of TMP would lead to a greater compressibility of the cake layer, and the operation at the critical point could cause more serious membrane fouling. Finally, energy consumption and the technique for order preference by similarity to ideal solution combined with grey relational analysis (TOPSIS-GRA) could quantitatively evaluate membrane fouling performance, and the results showed that a lower TMP, especially below the critical point, was a good choice for sustainable control of membrane fouling. Over all, this insight into TMP elucidated the importance of employing lower TMP during the algae separation process under specific vibration conditions, providing a theoretical basis for the selection of TMP.