Impact of ultrafiltration operating conditions on membrane irreversible fouling

PAC/UF for Removing Cyanobacterial Cells and Toxins from Drinking Water

“…With both velocities only a fraction of PAC was recycled as a suspension and just for a short period of time, and even the higher CFV did not yield a higher feed normalised turbidity. A similar PAC deposition rate was observed for both CFVs, a behaviour which is analogous to that found by Crozes et al (1997) and Matsui et al (2001). In addition, for the laminar conditions tested, a comparable membrane permeability decrease pattern was observed for CFV 0.5 m/s (Reynolds number of 463, at 20ºC) and 1.0 m/s (Reynolds number of 926).…”

Reversibility of fouling on ultrafiltration membrane by backwashing and chemical cleaning: differences in organic fractions behaviour

“…This expansion is due to the fact that UF has proved to be an effective physical barrier to particles, colloids, bacteria and certain viruses that are larger than the UF membrane pores and, hence, are retained by size-exclusion mechanisms, among others. Furthermore, UF provides extra advantages over conventional treatments such as small footprint, low energy consumption, limited chemical dosing, capability of coping with wide fluctuations in feed quality and delivering permeate of relatively constant quality, and reduced scale-up risks [1][2][3][4][5].…”

“…The removal of the irreversible fouling can be partially achieved only through aggressive chemical cleaning ("cleaning in place" (CIP)), which is usually burdensome and requires the shutdown of the unit being cleaned for several hours. Chemical cleaning causes both a reduction of the overall production plant capacity and a deterioration of the membranes, wherefore it should be minimised wherever possible [3,11]. A strategy that helps minimise chemical cleaning is the addition of chemical cleaners into the water used for BW, giving rise to the so-called "chemically-enhanced backwash" (CEB) [12].…”

“…First, these studies treat different types of water: wastewater [2,5,6,11,12,16], seawater [1,17,18] and surface water [3,10], each with different fouling behaviour potential under a given BW regime. For instance, it has been reported that a high salt concentration in the seawater might influence the interaction forces between membrane and foulants [1].…”

“…Second, the configuration of UF modules in these st8]udies is very variable: flat-sheet [10], spiral wound [17], pressurized (inside-out) [5,6,12,18] and submerged (outside-in) [1,10] hollow fibre membrane systems, also affecting the propensity to fouling [1,16,19]. Furthermore, most of them are focused on the evolution of the membrane resistance and fouling rates [2,3,5,6,16] and only a few quantify the reversible and irreversible fouling after each backwash cycle [1]. Within this context, more research is still needed on quantitatively determining the effect of BW-related variables on the reversibility of fouling on UF membranes for all scenarios and, in particular, for the outside-in hollow fibre UF for surface water.…”