I just realized this idea this morning. If water is under 29 hg's (inches) of vacuum, it will boil at 75F or 24.4C.
If the vacuum is increased to 29.42 hg's of vacuum, water boils at 59F or 15C.
A pressure head 33 ft. (9.8m) tall is supposed to create such a vacuum. If so, then very little energy would be needed to desalinize or purify water. There would be 3 pressure heads at work. One would be solute or brackish water. The second would be for brine discharge and the third, of course, would be clean water.
If the self siphoning concept can work, then it could be a self powering system. If not, then 3 pumps would be needed.
This would be to ensure a controlled flow and to maintain the necessary vacuum. And since the pipes could be welded, there might be nothing to allow air into the system except for what is in the water.
To degas water, pressure heads could be filled while almost all air is vented, When the vent is closed, water could be drawn through. And then as degassing occurs, the water level on the discharge side can be allowed tolower to maintain the vacuum.
After this, degassed water could be drawn through another set of pressure heads causing it to evaporate under vacuum. And by using the mass of the water to maintain vacuum, it should be a fairly efficient system.
Since water does cool as water evaporates, the lower temperature would need to be considered. Also, for continuous operation, 2 degassing systems may be needed.
I'm kind of wonderingif someone has tried this before.