How can you turn seawater into drinking water?

Hook

Why and how can you turn seawater into drinking water? Oceans hold about ninety seven percent of Earth's water, but it's far too salty to drink. Desalination is how we take the salt out.

Salt

Seawater has about thirty five grams of salt in every liter. Drinking it actually dehydrates you, because your kidneys need extra water to flush out all that salt.

Boil

The oldest method is distillation. Boil seawater, and the water evaporates while the salt stays behind. Cool the steam, and you get fresh water. It works, but it takes a lot of energy.

Ro

Most modern plants use reverse osmosis. Seawater is pushed at high pressure through a membrane so fine that water molecules get through but most of the salt doesn't.

Pressure

Normally, water flows from the less salty side to the saltier side. That's osmosis. Pushing hard enough reverses it, forcing fresh water out of the salty side.

Cost

The catch is energy and leftover brine. Pumps use lots of electricity, and the extra salty water left over has to be handled carefully so it doesn't harm sea life.

Small

Now the same idea is shrinking into portable devices. Small units can make drinking water in emergencies, like after a hurricane knocks out a town's water supply.

Close

So desalination takes the salt out of seawater, mostly by forcing it through ultra fine membranes. ThatsWhyHow.