The role of desalination membrane spacers in biofouling prevention

As water scarcity increases, there is a need for creative solutions to supplement the freshwater supply. Membranes have evolved as a key component of desalination devices, which remove the salt from seawater using reverse osmosis.

These membranes don’t work alone, however, and a review by Hu et al. discusses the important role of spacers in membrane-based desalination devices.

“As a key component in membrane modules, the optimization of feed spacers is crucial for improving system performance and mitigating fouling issues,” said author Xiao Hu.

Fouling is a common problem with membrane-based desalination devices. As water flows through a device, debris can be left behind on the membrane. Membrane fouling mainly includes contamination from biofouling (from microorganisms themselves), inorganic scaling (from deposition, precipitation, and oversaturation of inorganic substances), organic fouling (from cellular components), and colloidal fouling (from particles in the nanometer to micron range). Among these types, biofouling is the most complex to eliminate, even with pretreatment.

Keeping liquid flowing through the membrane is an effective way to combat biofouling, and spacers play an important role in reducing stagnant zones by optimizing flow channels in a desalination device. Some also have specialized coatings to inhibit microbial adhesion or use electrochemical methods to suppress biofilm formation.

The researchers found that electroconductive spacers, which help remove biofilms, are very effective in preventing biofouling. Also effective are biologically inspired spacers that enhance local shear and keep flows turbulent, and spacers with hydrophilic coatings that prevent bacterial adhesion.

“This review aims to systematically summarize research progress in spacer geometry design, anti-fouling strategies, and mass transfer enhancement, providing guidance for the development of high-performance spacers in the future,” said Hu.

Source: “Impact of feed spacers on flow dynamics in seawater desalination: A review,” by Xiao Hu, Junjie Li, Hongrui Zhao, and Yan Xia, International Journal of Fluid Engineering (2025). The article can be accessed at https://doi.org/10.1063/5.0272649 .