The role of exopolysaccharides in fouling phenomenon during ultrafiltration of microalgae (Chlorellasp. and Porphyridium purpureum): advantage of a swirling decaying flow.

Ultrafiltration of two microalgae species, Chorellasp. and Porphyridium purpureum, has been performed in two filtration units of different configurations: a module generating a classical tangential-plane flow and another one inducing a swirling decaying flow. The swirling motion is generated by a unique tangential inlet at the bottom of an annulus. Permeation flux obtained in each ultrafiltration unit depends on the filtered species, and specific deposits are associated to each species and module. Enhancement in permeation flux in the swirling configuration compared with that obtained in the plane unit can reach 40% during the ultrafiltration of Porphyridium purpureum and is negligible for the suspensions of Chlorella sp. The experimental data revealed the significant role of the soluble compounds in the medium culture in terms of flux limitation. It seems that the soluble products and their interactions with the microalgal cells are strongly involved in the fouling mechanism.