Why Treat Ocean Water for Drinking? Desalination Explained

The Need

With 97% of Earth's water saline and freshwater scarcity rising, desalination—removing salts/minerals from seawater—is a growing lifeline for coastal regions.

Dominant Technology: Reverse Osmosis (RO)

Seawater is pressurized against semipermeable membranes that reject ~99% of dissolved salts. Permeate (fresh water) is then remineralized and disinfected to meet drinking standards.

Benefits

• Drought-proof supply for coastal cities (Israel, Saudi Arabia, UAE, California, Australia).
• Can remove contaminants (heavy metals, pathogens) alongside salt.
• Supports economic growth where no other source exists.

Challenges

• Energy Intensive – 3–4 kWh/m³ for RO; carbon footprint unless renewables-powered.
• Brine Disposal – Hypersaline concentrate (2× seawater salinity) can harm benthic ecosystems if not diffused properly.
• Capital Cost – $1,000–$2,500/m³/day capacity; high upfront investment.
• Marine Impacts – Intake impingement/entrainment; mitigated by subsurface intakes, screens.

Future

Falling renewable energy costs, membrane advances, and brine-mining (recovering lithium, magnesium) are making desalination increasingly viable worldwide.