I have no medical education whatsoever, so I have no real basis to refute dustfromamoths writeup. I can, however, recognize false scientific reasoning when I see it:

"Far from being "toxic," urine (which is about 95% water) may actually contain some of the purest water that we can drink."

Right. Whenever you add anything to pure water, that makes it impure. Therefore it's nonsense to speak of 95% pure water; the 5% other stuff is exactly what makes it impure!
No doubt there is some very pure water present in the most polluted rivers, but that does not make them any less toxic...