Doesn't pumping to high pressure require a lot of energy?
Yes, it does.
But don't worry, we're going to recycle that energy in just a few more steps.
step four
pump it again
more pressure
High pressure pumps are used to increase the pressure of the water so it can be forced through the very fine filter that separates out the salts. This is called the membrane. Depending on how salty the water is and the type of membrane used, more or less pressure is needed. Seawater requires a lot of pressure. Running those very big pumps consumes a lot of energy!
