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Critical fouling conditions were studied during wine cross-flow microfiltration using a multichannel ceramic membrane (0.2 m). The aim was to determine critical operating conditions in order to limit fouling caused by wine colloids (tannins, pectin and mannoproteins) and enhance process performances. The method used is a square wave filtration based on the determination of the reversibility and irreversibility of fouling. Filtrations were performed with filtered red wine (FW) added with different concentrations of colloids. Considering FW, critical flux for irreversibility was beyond the studied range of pressure (≥1.4 × 10 −4 m/s). No clear critical flux could be determined for any of the tested molecules in the studied range of pressure. On the other hand, an upper limit of fluxes range has been identified (below which critical flux could be found). Irreversible fouling always takes place from the beginning of the filtrations and even at low pressures. For FW containing 0.2 g/l mannoprotein and 0.5 g/l pectin, a loss of average fluxes is observed beyond a given limit of transmembrane pressure. This fact was attributed to the compaction of a gel layer. Finally, a criterion (R if /R m ≤ 1) has been suggested to determine the so-called "threshold flux" below it, fouling remains acceptable.

The purpose of this work is to examine the interplay between hydrodynamic conditions and physicochemical interactions from filtration experiments of microparticles. Experiments are performed in microfluidic filters with real-time visualization at pore scale. Both flow rate and pressure are measured with time to analyze the dynamics of pore clogging and permeability. Flux stepping experiments are performed at different physicochemical conditions to determine the different clogging conditions. The results allow distinguishing different clogging behaviors according to filtration conditions which are discussed by considering particle-particle and particle-wall colloidal interactions whose main characteristics are an important repulsive barrier at 0.01 mM, a significant secondary minimum at 10 mM, and low repulsive barrier at 100 mM. Clogging delay at moderate ionic strength and deposit fragility and associated sweeping out of aggregates of particles at high ionic strength are discussed from the deposit structure, specific resistance, and deposit relaxation analyses. It has also been observed that an opening angle at microchannel entrance causes rapid clogging, this effect being more pronounced when the repulsion is partially screened. Three different scenarios are discussed by analogy to crowd swarming: panic scenario (0.01 mM) where repulsion between particles induce pushing effects leading to the creation of robust arches at pore entrances; herding instinct scenario (10 mM) where the attraction (in secondary minima) between particles enhances the transport in pores and delays clogging; and sacrifice scenario (100 mM) where the capture efficiency is high but the aggregate formed at the wall is fragile.

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