Input water source: tap water, lake, river, sea, ocean. Basically any contaminated water source.
Stage 2
Multi-stage freezing process. Yes, ladies and gentlemen forget filters, membranes and other maintenance-need water treatment systems. The evolution is here.
Stage 3
We have a high purification factor for our waste water output. Only 2 liters of contaminated water is needed to produce 1 liter of pure drinking water. Additionally, we can use brine as a byproduct during desalination to produce salt.
Stage 4
Pure fresh drinking water. As a result we have the best possible water on earth.