We recently posted The shower of the future recycles its own water and heat, after which Steven M. Johnson sent us a note:
This was a recycling shower that I imagined would be used at a future time, though I was not in a position to imagine complex filtering, etc. My wife thought the idea was GROSS, showering fully or partially in your own dirty shower water. But at least I had a small filter on the shower head.
But it wasn't such a bad idea at all; it just needed a better filter.