This is an Emergency Situation where Drought is hitting Europe, Along with Africa and other continents. We need crazy ideas, to overcome this critical problem.
Nabil Khatib Desalination is a common technologies with about 21.000 plants in operation around the world.https://en.wikipedia.org/wiki/Desalination#Applications If one can afford the cost and energy use it makes safe potable water with little problems.
In UAE, desalination of Seawater is being extensively practiced. I think it would be a viable option for "Emergency situation" as you have mentioned. I agree with Harald G. Dill in terms of taste and quality issues.
Yes! For some regions of the Earth's bioshell desalination is becoming a human necessity. See pdf book chapter and other pdfs attached herewith. Also, the next issue of Brazil's premier on-line science journal, CALIBRE, will feature a macroproject found applicable to Brazil and India.
Other than the idea of seawater desalination and wastewater recycling, we need innovative ideas in techniques to orient consumer habits! The techniques of agriculture will have to be revised!