3D-printed membrane spacers aim to reduce biofouling in filtration systems

Membrane filtration is considered an established technology in water treatment, but deposits on the membrane surface and in the feed channel often limit operating time. A key role is played by so-called membrane spacers, which structure the flow channel and define the distance between the sheets. A research team from the Universiti Kebangsaan Malaysia and other institutions has published an overview of current developments in this field in Frontiers of Chemical Science and Engineering. The focus is on geometrically modified and additively manufactured spacers for fouling mitigation.

Conventional polypropylene spacers with a simple mesh structure often generate dead zones and increased pressure drop as filtration performance rises, and promote biofilm-forming microorganisms. The authors summarize studies in which parameters such as filament thickness, mesh angle, layer height and multilayer structures were systematically varied. Numerical 2D and 3D flow simulations show that alternative geometries such as honeycomb or multilayer grids can promote turbulent mixed flows, reduce dead zones and thus slow down deposit formation.

Particular attention in the review is paid to 3D-printed spacers. Using SLS, DLP, PolyJet and FDM, complex, flow-optimized structures can be produced that are hardly feasible with conventional extrusion processes. In addition to standard polymers, metallic materials are used, as well as functional materials with zinc oxide coatings or graphene-embedded fillers that provide antimicrobial effects and modified surface energy. According to the researchers, experimental data indicate that such spacers can reduce pressure drop, improve hydrodynamic performance and decrease the energy demand per cubic meter of permeate.

In their conclusion, the authors point to the need to combine simulation-based design approaches with long-term trials under real operating conditions. Additively manufactured spacers are regarded in the technical literature as a flexible platform for iteratively adapting geometry, material and surface functionality and for specifically optimizing membrane modules for demanding applications such as seawater desalination or industrial wastewater.