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

Abstract

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.

Freshwater microalgae harvested via flocculation induced by pH decrease

“…It has been reported that many microalgae release large amount of RPS during growth [31], and most RPS can interfere with flocculation due to their complexation with multivalent metal ions [26,32]. However, some RPS are helpful to flocculation owing to the bridging mechanism [33,34].…”

Pilot‐scale microalgae harvesting with ceramic microfiltration modules: evaluating the effect of operational parameters and membrane configuration on filtration performance and membrane fouling

“…9,11 In our study, the permeate flux decline could result in an increase in irreversible resistances that were generally related to the extracellular organic matters, including proteins, polysaccharides, and lipids released by microalgal cells during the crossflow filtration. 9,11,39 Table 3 shows EOM (protein + exopolysaccharides) content in the retentate, permeate, and rinse water sides after filtration processes. It can be observed that the amount of EOM in the retentate significantly increases with the increase in CFV.…”

“…As a result, higher amounts of cell debris and EOM released in the suspension caused severe membrane pore blockages. 12,39 The higher CFV of 6 m s −1 caused higher shear stress on microalgae cells during their passage through the valves, pumps, and the module, leading to higher EOM release. The EOM content in the rinse water at 6 m s −1 CFV is lower than that of 4 m s −1 , which suggests that a great part of the EOM released at 6 m s −1 CFV remains adhered on the membrane surface, leading to the higher irreversible resistances at 6 m s −1 .…”

The released polysaccharide of the cyanobacterium Aphanothece halophytica inhibits flocculation of the alga with ferric chloride

“…It has been reported that algogenic organic matter (AOM) is involved in the reduction of flocculation efficiency in water treatment, and the inhibitory mechanism is that AOM can form complexes with cations in flocculant, which reduces the coagulation ability of the flocculant (Cheng and Chi 2003;Takaara et al 2007). Many microalgae release large amount of polysacchrides (RPSs) during growth (Morineau-Thomas et al 2002); however, no attention has yet been given to the influence of the RPS on the flocculation of microalgal cells with multivalent metal salts.…”