eli5: Why is it so difficult to desalinate sea water to solve water issues?
In: 1972
It’s not difficult. It’s pretty easy really.
But it’s also super expensive to do at an industrial scale. And then exporting the water to where it’s needed is expensive too.
Is there any progress in desalination each year? Is there a cool ‘Moore’s Law’ type chart showing that the cost per Gigalitre is dropping and when it reaches $X it will be better than dams & artesian bores etc ?
One other item others haven’t mentioned is what to do with the brine (ultra salty waste). If you’re filtering enough water to make desal useful, you get quite a bit of leftover brine. If you continue throwing this back into the ocean in the same place, the spot becomes toxic to creatures around it. Similar if you try and throw it away on land. It’s always better to not create more environmental problems than you’re solving.
It isn’t difficult in the sense that there is no means to do it. In fact it is a fairly simple process.
The difficulty is cost and the main elements are cost of the capital (buildings, equipment) and cost of energy required to accomplish desalination.
We use a lot of water, so facilities for desalination have to be very large to make a difference. This introduces many capital cost factors – like land, disposal of brine etc.
Desalination is energy intensive and energy is expensive. Water, unfortunately, has traditionally been “sold” at a very low cost. In this sense, many parts of society consider it a “right” etc which makes it a politically and socially difficult product to sell at the price that would support desalination (ie pay for the capital and energy needed)
Having said this, there are places and countries like Saudi Arabia, Israel and Singapore who have integrated desalination into their water infrastructure. So it is not impossible, it is simply uneconomical or politically difficult to do in many cases.
The science of it is pretty easy. You can do it in your kitchen. Doing it at the scale needed to actually make it useful requires a lot of facilities, and uses up a lot of energy.
it is extremely energy-intensive which makes it very very expensive.
the salt dissolves in the water so you cant separate them with a sieve or something similar.
It isn’t. It’s quite easy. But it’s not as cheap as just sucking it out of a hole.
Many things are “easy” but they’re just harder to make profitable.
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