Hydrodynamics in Membrane Modules and Membrane Performance Optimization

The spiral-wound element is an industry standard because of its high membrane area packing density, low cost of manufacture, and extensive installation base worldwide. Plastic mesh spacers create a feed-channel between facing membrane leafs and promote turbulent flow, which aids to reduce solute concentration polarization and related scaling and fouling phenomena. Computational and experimental studies have demonstrated complex hydrodynamics that vary depending on the spacer geometry, thickness, and membrane packing density. Analyses of fouling deposits on RO membranes, removed from spiral wound elements, have revealed that channel spacers strongly influence foulant deposition patterns. For example, the presence of ill-designed feed spacers can create stagnant zones with elevated concentration polarization. These stagnant regions adversely affect membrane performance by promoting fouling and scaling locally, thus reducing flux, limiting water recovery, and lowering permeate quality.