Causing sea or river water to boil removes all salts and pollutants. But adding heat is very expensive! Even here we can reduce the scot of making pure water by a factor of 9.
We pass the steam through a turbine, and generate power: We need to produce the steam at 4 atmospheres pressure, and 120oC.
We vent the steam down to 4 atmospheres, so we produce dry, super heated steam. So we generate 20kW of electricity. We convert into mains AC.
We then use some of this power, to drive a Carnot heat pump, so the steam meets a cold, low pressure gas in a helical turbulence heat exchanger.
So we get out liquid water at 10oC. We use to pump off to cold storage. The heat into high pressure gas we return to the boiler room – where it heats the water.
We use the rest of the power to drive heating elements in the boiler. It looks rather like, once started, we will only need supply 2% of the heat we use today. And get off pure water.
From sea or river water – we need the facility to draw off some of the dirty/salty water, the we pass over another Carnot system.
So produce brown or brine water – which we discharge into the sea or river – using the second Carnot system to remove the heat before we get rid of the unwanted salt/contaminants.
But there is an easier sustem. We produce vacuum, using a small wind teurbine, solar panel or little diesel motor. E=PV, and as we want ony l0.1 atmospheres – we need very little power.
The solar panel can charge up a batterym to see us through the night. The water boils at 0.1 atmospheres – losign all saltys or contaminants, So we exert the pressure on a conical structure 1m high.
So the cold brine/river water carreis the contaminants away from the plant – as the cold water sinks, and flows away from the plant naturally.
We then have a chain of vacuum pumps, to carry the fresh water vapour to high storge.
In areas o9n a canal, we can convert the water into pure water – for 1% the cost of mains power. So we carry the water vapour to a high preservoir, and they loads the water at hgih pressure int othe mains. So massively flashing the cost of mains water.
To and cities tend to be build on rivers – so we suck pure water out above the town, and as theriver flows through the town, it gets back the same water – with contaminants in. So we massively flash the cost of mains water.
We could use a steam plasma tube, as a source of heat and so power. A 50x1cm steam plasma tube at 4 athmospheres, releases a constant 1.2MW of heat – so it will drive a heat water purification plant.
We can boil off steam, and generate ½MW. Thsi will power a vacuum desalination plant, t oproduce unlimited quantities of pure, drinkable water. For free.
If we site a semuicircle of 1mx2cm steam plasma tuybes around harbours, the will relse 8.6MW each – and we have 20 od them. 130MW of heat.
This will warm the environment, and give an ice area the climate of North Europe. We then site these tubes in rivers in the interior. We melt all permafrost – and keep the water way open, with no need of ice breakers.
An old style town water company, can sell water for 5% the costs of mains water.