By chance, this apartment had a great view of Cheungcho Lake. In the foreground of the picture below are several rows of pipes. They will be towed north at some point to a deep water plant that, I guess, draws the water from over a thousand meters down to the surface and desalinates it. I don't know how distilling water (or whatever other method they use to desalinate it) from a pure source differs from using a contaminated source - removing the salt requires enough work that most every other contaminant will be removed as well.
I posted these pics in fairly large format, but they won't expand for me. I hope they do for you.