By Claude — Desalination News
Researchers from Lund University, ENEA, Cranfield University and Politecnico di Milano have detailed a desalination concept that tries to close two gaps at once — cutting the carbon out of the power supply and cutting the brine out of the waste stream — by pairing concentrated solar power with a two-stage membrane process. The project, named DESOLINATION, was presented at the 4th International Workshop on Membrane Distillation and Innovating Membrane Operations in Desalination and Water Reuse, held in Cetraro, Italy.
The process runs in three linked stages. First, incoming seawater is concentrated using forward osmosis, drawing water across a membrane using a thermo-responsive polymeric draw solution rather than the high hydraulic pressure that reverse osmosis relies on. That diluted draw solution is then heated using waste heat recovered from a Brayton-cycle power block and passed through a coalescer, splitting it into a water-rich phase and a polymer-rich phase; the water-rich stream is polished by nanofiltration while the polymer is recycled back into the draw-solution loop. The concentrated seawater left over from the forward-osmosis step is then preheated and fed into a vacuum membrane distillation stage, squeezing out further water recovery and pushing the process toward zero liquid discharge rather than a brine stream that has to be managed separately.
Because forward osmosis needs far less hydraulic energy than pressure-driven membrane processes, and because the heat used to regenerate the draw solution is waste heat from the solar power cycle rather than fresh input energy, the team frames the combination as a route to a genuinely low-carbon desalination pathway rather than simply a renewable-powered version of a conventional plant — the same logic that has been pushing developers toward brine-minimising and zero-liquid-discharge designs more broadly as disposal of concentrate becomes a harder regulatory and environmental sell.
Much of the engineering effort described sits at the materials level. The group is developing high-flux forward-osmosis membranes made using electrospinning and layer-by-layer deposition, aimed at getting more water flux out of the low-pressure process without sacrificing salt rejection. For the membrane distillation stage, they’re using superhydrophobic ceramic membranes with silane surface grafting — ceramic rather than the more common polymeric hollow-fibre membranes, chosen for their resistance to the wetting and scaling that has historically limited membrane distillation’s run time on real seawater. Ceramic nanofiltration membranes, only recently commercialised, handle the final polishing step. Several thermo-responsive draw solution chemistries are still being screened for their osmotic performance and ease of regeneration.
The stated next step is a large-scale pilot at King Saud University in Saudi Arabia, which would be the first real test of whether the lab-scale membrane performance holds up when the whole loop — solar collection, forward osmosis, heat-driven regeneration and vacuum membrane distillation — is run continuously and at volume. Techno-economic questions that tend to decide whether concepts like this move beyond conference posters, including capital cost per cubic metre and membrane service life, are also flagged as still under evaluation rather than settled.
(Source: Lipnizki, Poirier, Patchigolla, Manzolini, Avci and Al Mhanna, 4th International Workshop on Membrane Distillation and Innovating Membrane Operations in Desalination and Water Reuse, 2025, doi.org/10.48263/BOA_MD-CETRARO_2025)