Virus concentration by crossflow membrane filtration: Effect of hydrodynamic conditions and membrane properties

Crossflow membrane filtration is emerging as a concentration method for the recovery and detection of viruses in large volumes of water. To increase virus recovery, the membrane is usually "blocked" with a proteinaceous solution or a chemical dispersant. This study explores a novel approach using controlled and rapid (<1 h) layer-by-layer adsorption of polyelectrolytes to form an anti-adhesive, sacrificial layer on the membrane surface. Membranes coated with polyelectrolyte multilayers (PEMs) can ensure up to 2-fold higher pre-elution recoveries of P22 bacteriophage than membranes blocked with calf serum (CS). Calculations of virus-membrane interaction energies confirm that the higher recoveries with PEM-coated membranes are due to higher charge and hydrophilicity relative to the CS-blocked counterpart. The pre-elution recovery with PEM-coated membranes at high cross flow rates is >70%, which might eliminate the need for elution and backflushing steps, thus reducing both the time required for pathogen concentration and the volume of the final sample. Operating the filter at high transmembrane pressures and crossflow rates leads to a significant increase in the concentration rate; for example, for CS-blocked membranes the initial rate of 5.8 +/- 0.3 L/(min·m2) was achieved without affecting P22 recovery; this flux value is almost 4 times higher than values reported in the literature. In addition, the effects of crossflow and high permeate flow rate on the recovery and removal of infective virus from DI and surface water are evaluated using the CS-blocked membrane. An increase in the average permeate flux (up to 5-fold for DI water and 2-fold for surface water over values reported in literature) does not affect the recovery or removal of infective P22. Finally, the performance of the anti-adhesive PEM membrane coatings with complex water matrices is evaluated. The data are only preliminary as only a small number of filtrations have been performed but results seem to indicate that PEM-coated membranes can maintain their advantage over CS-blocked membrane in terms of P22 pre-elution recovery when concentrating viruses from MBR effluent. When challenged by MBR effluent, PEM-coated membranes also appear to be more resistant to fouling than their CS-blocked counterparts. With surface water however, no difference was observed.