Drinking the Ocean: New report strengthens the environmental case for subsea desalination
Environmental considerations have limited where desalination can deploy. New DNV modeling finds Flocean One’s subsea concentrate plume is limited to just a few meters—showing how seawater can become fresh drinking water without disrupting critical marine ecosystems.
The world is running out of fresh drinking water. The ocean is the largest untapped water source—but scaling desalination means proving we can turn seawater into drinking water without creating new environmental harm.
To understand that impact, Flocean commissioned an independent brine dilution study from DNV to study what happens to the extra salt left behind when seawater is turned into freshwater. If that salt stays too concentrated over a large area, it can disrupt marine life, but subsea desalination is designed to keep that impact tightly contained and away from sensitive ecosystems.
Across all three modeled current conditions, DNV found that salinity from Flocean One’s brine discharge returned to within 2 ppt of ambient levels within just 1.9–2.4 meters of the outlet. Even at the tighter 0.5 ppt threshold, the modeled impact remained within 8.7 meters. That means the area exposed to elevated salinity is limited to just a few meters around the system, rather than spreading across a broader marine environment. Additionally, during our last ROV inspection of Flocean One we used a CTD to measure the salinity of the outfall. Results showed that the salinity was less than 2 ppt above ambient within 2 meters of the discharge pipe, aligned with the simulations from DNV.
For comparison, DNV references California’s widely recognized desalination benchmark, which allows the same 2 ppt increase within a 100-meter mixing zone. Flocean One reaches that threshold within only a few meters.
The result supports a core premise behind Flocean: moving desalination offshore and into deep water can produce freshwater at scale while sharply limiting its impact on the marine environment.
A smaller marine footprint
Conventional desalination produces a concentrated seawater stream that has to go back into the ocean. If elevated salinity spreads too far, it can affect marine organisms and habitats. Conventional plants can also use treatment chemicals that become part of that discharge.
Flocean One is designed differently. Operating at roughly 500 meters depth, the system uses natural ocean pressure and abundant feedwater to run at a lower recovery rate, producing a less saline concentrate stream. It also operates without treatment chemicals, so the discharge is concentrated seawater only.
DNV modeled Flocean One’s discharge in still water, following-current and opposing-current conditions.
Across all three scenarios:
salinity returned to within 2 ppt of ambient within 1.9–2.4 meters
at the tighter 0.5 ppt threshold, the plume extended 3.5–8.7 meters
DNV notes that real-world ocean variability would generally increase dilution beyond the modeled conditions
For context, DNV compared the results with California’s desalination benchmark of 2 ppt above ambient within a 100-meter mixing zone. Flocean One reached that same threshold within roughly 2–4% of that distance. DNV concluded that the results compare favorably with the benchmark.
What this means: Flocean One’s salinity impact is confined to a very small area around the system. Combined with siting away from critical marine ecosystems, that means subsea desalination can produce freshwater at scale while keeping its impact on the surrounding ocean tightly contained.
What it means for subsea desalination
The significance goes beyond Flocean One. If desalination systems can be placed away from critical marine ecosystems and keep their salinity impact confined to just a few meters, the ocean becomes a far more viable source of fresh drinking water.
This study strengthens that case. Flocean One’s modeled plume remains tightly contained around the outlet, supporting freshwater production at scale with a much smaller marine footprint.
Flocean is continuing that validation work with real-world salinity measurements, underwater noise and vibration testing, and biodiversity monitoring.
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