Performance enhancement of spiral-wound reverse osmosis membrane elements with novel diagonal-flow feed channels

Abstract

Spiral-wound reverse osmosis membrane elements have been widely applied in household water purification which usually demand a high water recovery rate. Membrane scaling remains an intractable hurdle which would deteriorate the performance of membrane elements. In this study, we developed a novel feed channel with diagonal flow direction, for which the performances were examined by filtration experiments on real membrane elements and the impacts of channel configuration were analyzed via the coupling of computational fluid dynamics simulation with response surface methodology. The results showed that the membrane element with the novel diagonal-flow feed channels exhibited a higher water flux along with lower declining rate and higher salt rejection than the conventional one with axial flow direction. The alteration of water flow direction could considerably increase the average cross-flow velocity in the channel, thus enhancing mass transfer and reducing concentration polarization. For a targeted water recovery of 75% and water flux of ~45 L/(m2·h), the optimal configuration regarding the width ratios of the wide and the narrow openings at inlet/outlet of diagonal-flow feed channels are suggested within the range of 20–43% and 5–10%, respectively. The diagonal-flow feed channel has a promising application prospect for membrane scaling control.