Is so easy. We have a solar vacuum pump – maybe with a small wind turbine to supplement the power Maybe just using mains at night.
We raise the water up by 1m and it boils – so forming pure water vapour. We use a sequence of pumps to transfer it to a high reservoir – or just supply the water for a small group of farms.
It was forecast that fresh water would be the big shortage of the next century, but we only apply 1 atmosphere of vacuum, to produce pure water vapour.
We vent it above a storage reservoir, and end global hunger and thirst for ever! This will directly affect 1.38 billion – who do not have enough to eat.
And this is high school physics. There will never be a shortage of sea water – or now fresh water. This will make such a difference on Earth.
I requires light engineering – and the UN will fund the devices – to end global hunger and thirst.
If I had ermined in Sheffield I would have had the devices rolling out of the door 2003.