Like California and South Africa, isn’t the principle of water distillation relatively easy? evaporating from one end and cooling it from the other so that it becomes liquid again, leaving all the salt and pollutants behind.
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Imagine you have a big bucket of water, but you can’t drink it because it’s salty like the ocean. Some coastal cities and counties have this problem because their water sources, like rivers or underground wells, get mixed with salty ocean water. So, they can’t use that water for drinking because it tastes bad or can make them sick. To solve this problem, they need to find ways to get clean, drinkable water, which can be a big challenge
It is very easy. But it is also very expensive. California does have some desalination plants, but they are mostly not of significant size, because like I said, it’s expensive. It’s not as if people are without water there.
If California were to have an actual issue meeting demand (not just worrying about preserving the source as they are) desalination would be in full swing as the benefit would outweigh the cost.
It’s NOT distillation, it is DESALINATION which is VERY different.
It is an expensive, energy intensive process.
[https://en.wikipedia.org/wiki/Desalination](https://en.wikipedia.org/wiki/Desalination)
It’s easy, but it’s extremely expensive. Boiling water takes A LOT of power. You can try this yourself, put a pot of water on your hob and see just how long it takes for the entire pot to evaporate into steam.
Desalinating 1l of water by boiling requires 2.2 MJ of energy. Even using some of the lowest per person water usage in america (SF at 150 l/day), supplying all 39 million californians with desalinated drinking water would require 5.8 billion liters of water a day, which in turn would require 12.7 billion MJ of energy per day, or 3.5 billion kWh per day. That’s about half of the entire US’ current power consumption, and that would be JUST for california, and assuming that californians cut their water usage in half.
South Africa has a severe lack of electricity supply (generation?) as it is, let alone trying to power desal plants
The principal of water distillation is easy. The execution is hard.
You need to boil the water. This means spending energy to heat it, or spending energy to generate a partial vacuum.
The amount of energy spent is typically far more expensive than people are willing to pay for water, so it isn’t done.
Desalination is simple but VERY expensive. There are two main technologies for desalination:
1. Distillation. Like you said, evaporate and cool down. This is very expensive because water has a very high heat capacity. All that energy has to come from somewhere. On top of this you have to do something with the left over salt. If it is left in the boiler, it will build up further reducing the efficiency, increasing costs.
2. Reverse Osmosis. This involves pushing water using high pressure through a membrane that is fine enough that the salt cannot move past. This is more efficient, but slow and has to have huge scale to supply a city.
Practical engineering on Youtube has a great video explaining the processes and difficulties in desalination. [https://www.youtube.com/watch?v=mxqOPdEUNTs](https://www.youtube.com/watch?v=mxqopdeunts)
The only way desalination will become very widespread is if our electricity supply increases significantly since desalination requires a very large amount of energy.
That will only happen if we massively increase our solar and/or nuclear energy production.
Side note, it is being used
>An estimate in 2018 found that “18,426 desalination plants are in operation in over 150 countries. They produce 87 million cubic meters of clean water each day and supply over 300 million people.”
As a old water scientist, I can give a single answer.
There are a huge number of good methods for desalination, but until now we haven’t found one that isn’t both power intensive (and costly) AND ALSO environmentally friendly (as in not returning very saline water back locally).
IMHO.
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