Water scarcity is worsening across cities from Cape Town to Lima; traditional sources aren’t keeping up. The UN forecasts that in five years demand for fresh water may outpace supply. To respond, some companies are developing subsea desalination: using deep-sea water and pressure rather than big energy inputs at the surface, reports Scientific American.
The idea is to position reverse osmosis (RO) devices at depths of around 500 meters (≈1,600 feet). At that depth, the natural hydrostatic pressure helps push seawater through RO membranes, reducing how much energy surface pumps have to supply. Purified water then gets pumped back to shore. This setup can cut energy use by 40–50% compared to standard desalination plants.
Flocean, a company based in Oslo, is a lead player. Its CEO says its system is “a subsea pump cleverly coupled to existing membrane and filter technology”; nothing extremely new, but combining efficient components with thoughtful deployment. Depth brings other benefits: fewer microorganisms and algae, more stable temperature and pressure conditions, less chemical pretreatment of feed water, and less disruption to land-based landscapes or coastal aesthetics.
But subsea desalination still faces hurdles. Although energy savings are promising, the cost remains high. Pumping purified water up from 500–600 meters to land consumes energy and demands reliable infrastructure. The scale hasn’t yet proven viable. Membrane maintenance is also an issue; fouling still happens, though researchers are exploring self-cleaning or electrically conductive membranes to mitigate it.
Environmental impact is another concern. The intake of water, disposal of brine, and effects on deep-sea habitats, particularly the “twilight zone” where life is less understood, must be evaluated carefully. And not all coastal regions are suitable; steep drop-offs are preferred, as shallow continental shelves would require long pipelines and higher costs.
Subsea desalination is an intriguing way to produce fresh water more sustainably. It does reduce energy use and can avoid many drawbacks of land-based plants, but it still must prove itself at a large scale, economically and ecologically, before it becomes a mainstream solution.