Fouling resilient perforated feed spacers for membrane filtration

Sarah Kerdi; Adnan Qamar; Johannes S Vrouwenvelder; Noreddine Ghaffour

doi:10.1016/j.watres.2018.04.049

Fouling resilient perforated feed spacers for membrane filtration

Water Res. 2018 Sep 1:140:211-219. doi: 10.1016/j.watres.2018.04.049. Epub 2018 Apr 24.

Authors

Sarah Kerdi¹, Adnan Qamar¹, Johannes S Vrouwenvelder¹, Noreddine Ghaffour²

Affiliations

¹ King Abdullah University of Science and Technology (KAUST), Water Desalination and Reuse Center (WDRC), Biological and Environmental Science and Engineering (BESE), Thuwal 23955-6900, Saudi Arabia.
² King Abdullah University of Science and Technology (KAUST), Water Desalination and Reuse Center (WDRC), Biological and Environmental Science and Engineering (BESE), Thuwal 23955-6900, Saudi Arabia. Electronic address: noreddine.ghaffour@kaust.edu.sa.

PMID: 29715645
DOI: 10.1016/j.watres.2018.04.049

Abstract

The improvement of feed spacers with optimal geometry remains a key challenge for spiral-wound membrane systems in water treatment due to their impact on the hydrodynamic performance and fouling development. In this work, novel spacer designs are proposed by intrinsically modifying cylindrical filaments through perforations. Three symmetric perforated spacers (1-Hole, 2-Hole, and 3-Hole) were in-house 3D-printed and experimentally evaluated in terms of permeate flux, feed channel pressure drop and membrane fouling. Spacer performance is characterized and compared with standard no perforated (0-Hole) design under constant feed pressure and constant feed flow rate. Perforations in the spacer filaments resulted in significantly lowering the net pressure drop across the spacer filled channel. The 3-Hole spacer was found to have the lowest pressure drop (50%-61%) compared to 0-Hole spacer for various average flow velocities. Regarding permeate flux production, the 0-Hole spacer produced 5.7 L m^-2.h^-1 and 6.6 L m^-2.h^-1 steady state flux for constant pressure and constant feed flow rate, respectively. The 1-Hole spacer was found to be the most efficient among the perforated spacers with 75% and 23% increase in permeate production at constant pressure and constant feed flow, respectively. Furthermore, membrane surface of 1-Hole spacer was found to be cleanest in terms of fouling, contributing to maintain higher permeate flux production. Hydrodynamic understanding of these perforated spacers is also quantified by performing Direct Numerical Simulation (DNS). The performance enhancement of these perforated spacers is attributed to the formation of micro-jets in the spacer cell that aided in producing enough unsteadiness/turbulence to clean the membrane surface and mitigate fouling phenomena. In the case of 1-Hole spacer, the unsteadiness intensity at the outlet of micro-jets and the shear stress fluctuations created inside the cells are higher than those observed with other perforated spacers, resulting in the cleanest membrane surface.

Keywords: CFD; Filtration; Fouling; Novel design spacers; Optical coherence tomography (OCT); Perforated spacers.

Publication types

Research Support, Non-U.S. Gov't

MeSH terms

Biofouling
Equipment Design
Filtration / instrumentation*
Filtration / methods
Hydrodynamics
Membranes, Artificial
Pressure
Printing, Three-Dimensional
Water Purification / instrumentation*
Water Purification / methods

Substances

Membranes, Artificial