Simulations of novel mixed-patterned membrane surfaces: Enhanced hydrodynamics and concentration polarization to mitigate fouling in water treatment

Abstract

The accumulation of particles and salt ions on the membrane surface is the main challenge in different water treatment applications, such as microfiltration (MF), ultrafiltration (UF), reverse osmosis (RO), and nanofiltration (NF), undesirably affecting the membrane's water permeance and salt rejection. This study used computational fluid dynamics (CFD) simulations to investigate novel mixed triangular-rectangular (mixed tri-rec) shaped patterned membrane surfaces toward reducing membrane fouling and increasing water flux. These outcomes were compared with previously reported flat, triangular (tri), and rectangular (rec) patterned surfaces. The fluid flow behavior and transport of diluted species under laminar flow conditions were investigated in the vicinity of different patterned membrane surfaces. Parameters such as diffusion coefficient, pressure difference across the membrane, and feed solute concentration remained fixed during the investigation. The key parameters evaluated were the velocity streamline profile, shear stress, concentration polarization (CP), and permeate flux (PF). The overall wall shear stress (OWSS) and local wall shear stress (LWSS) were also evaluated, and unobvious behavior was observed in both cases. Also, interesting behavior emerged when the averaged CP and PF were analyzed as a function of varying crossflow velocities. Further, the results indicate that pattern geometry significantly affects the PF. Additional simulations varying pattern sizes parametrically were performed, and the influence of pattern size ratio on CP, PF, and consequently, boundary layer thickness was investigated. Overall, this study presents a new understanding of fouling mitigation and enhanced permeate flux while comparing a novel mixed tri-rec-shaped membrane surface with previously reported homogeneous patterned surfaces.