Benefits of High Shear Rate Dynamic Nanofiltration and Reverse Osmosis: A Review.

Dynamic filtration permits to increase permeate flux and membrane selectivity, as compared to crossflow filtration. It consists in creating the shear rate by a disk rotating near the membrane or by rotating or vibrating the membrane, avoiding the need for large feed flow rates. The benefits of high shear rates are important in microfiltration and ultrafiltration, but they are even larger in nanofiltration (NF) and reverse osmosis (RO). The reduction in concentration polarization by high shear rate can increase the permeate flux by a ratio of 3 to 5 as compared to a spiral wound module and augments also solutes rejection as their diffusive transfer through the membrane is reduced by a factor of 4 to 5. This paper describes available dynamic filtration modules suitable for NF and RO and reviews the treatment of dairy effluents, desalination, oil emulsions, and oligosaccharides recovery using a rotating disk module or a VSEP module with vibrating membranes and compares their performances with those of crossflow filtration. These examples confirm the high potential of dynamic NF and RO when operated at high shear rate and high TMP. The availability of large rotating NF ceramic membrane disks could permit the fabrication of highly efficient modules. [ABSTRACT FROM AUTHOR]