[bloaf]

That's the thing with evaporation: you don't want your water to leave stuff behind after it evaporates because that will foul your equipment and cause lower efficiency.

You could in principle design systems with enough fouling mitigations that you'd be fine, but its likely that the cost of those mitigations is roughly the same as just purifying the water up-front.

[archagon]

But then... don't you need to distill the water anyway? It's not like blue water lacks impurities.