Assessment of Different Designs of Arch-Type Filament Spacers for Spiral-Wound Membrane Filtration

Abstract

Feed spacers are essential components of any spiral wound membrane module, maintaining the integrity of feed channels and enhancing fluid turbulence. However, they increase channel pressure gradients and create local stagnation zones, thereby exacerbating membrane fouling. These issues result in additional costs in the water treatment process. Now to fully utilize the potential of membrane filtration technology, it is necessary to reduce the problem of membrane fouling through the development of improved membrane feed spacers. Previously an Arch-Hole (Spacer-4) configuration was introduced, and herein three new configurations with higher channel porosity and shear force than the original Spacer-4 design have been assessed alongside that design. The four innovative feed spacers were studied experimentally under conditions that generate biofouling. Channel porosity and shear stress play important roles in biofouling development. Spatial distribution of shear stress was obtained via computational fluid dynamic simulations. Findings suggest that achieving uniformity of the shear force and eliminating dead zones are more crucial than high shear stress values. Such conditions were achieved with Spacer-4 type which maintained superior flux and gave for the module itself a relative specific energy consumption of 0.26 kWh/m³, significantly better than the next best value at 0.43 kWh/m³.