Purified urine

I remember one time there were two brothers in china who had been buried under a collapsed building, (or was it a mine? anyway) for several days but they survived. With no food all they got was their urine. We are humans, we strive to survive in whatever way, and they did the noblest thing no matter how you imagine it. But this time, according to the news I read, it is not just for people buried underground without food and water, and for NASA astronauts too! Astronauts would have to have a communal drinking water supply from their own urine, but of course, it is purified.