I've read about some pretty interesting recent developments in desalination and other water "cleaning" technologies lately, but they're all still "in the lab" a

I've read about some pretty interesting recent developments in desalination and other water "cleaning" technologies lately, but they're all still "in the lab" as it were. Nothing of the newest and most amazing stuff I've read about has yet progressed to the point of being in any widespread use. As another reply mentions, existing technologies that are in use tend to be quite expensive (in terms of cost and power/resource usage required to get the job done on any sort of large scale).