Seawater desalination has really changed over the last ten years, both in technology and cost. Today, modern seawater reverse osmosis (SWRO) systems, especially those with energy recovery, can make fresh water for just $0.40-$0.80 per cubic meter in big plants. That’s competitive with traditional water treatment methods in places where water is scarce. This guide will walk you through how SWRO works, what makes energy and capital costs different between systems, how to think about getting rid of brine, and what’s next for desalination technology as we head into 2026 and beyond.<\/p>\n
About 97% of the world’s water is salty, mostly ocean water with 33,000-37,000 ppm of total dissolved solids (TDS). The other 3% is freshwater, but two-thirds of that is stuck in glaciers and ice caps. The freshwater we actually use, like surface water and shallow groundwater, is under huge stress. Think population growth, farming needs, industrial use, and climate-driven droughts all hitting it at once.<\/p>\n
The that by 2025, half the world’s people would live in water-stressed areas. The International Desalination Association reports that global desalination capacity topped 100 million cubic meters per day in 2023, a big jump from 65 million in 2015. SWRO now accounts for roughly 70% of all global desalination capacity.<\/p>\n Seawater reverse osmosis uses hydraulic pressure to push seawater through a special semi-permeable membrane, going against its natural osmotic flow. Seawater has an osmotic pressure of about 390 psi (27 bar). To get water through the membrane, the pressure you apply has to be higher than that, usually 800-1,200 psi (55-83 bar) in commercial SWRO systems.<\/p>\n The membrane blocks dissolved ions like sodium, chloride, magnesium, sulfate, and many others, but lets water molecules pass through. Modern SWRO membranes can reject 99.5-99.8% of salt, making permeate with 150-400 ppm TDS from seawater that started at 35,000 ppm. The water that doesn’t go through exits as a concentrated brine, around 50,000-70,000 ppm TDS, and at pretty much the same pressure as the incoming water.<\/p>\n Energy makes up 30-50% of the cost to run a seawater desalination plant. Without energy recovery, an SWRO system uses 7-12 kWh for every cubic meter of water it produces. But with modern pressure exchanger ERDs, which are over 95% efficient, energy use drops to 2.5-4.0 kWh\/m-. That’s a 60-70% reduction, and it completely changed how affordable SWRO became over the last 15 years.<\/p>\n\n
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