I have recently watched "How Many People Can Live on Planet Earth?" documentary with David Attenborough. In it, in the main factors that will limit total human population Earth can support the limited amount of fresh water was named. There also was a part where it described how on International Space Station fresh water is distilled from astronaut urine.
My current understanding is that all the water (fresh or not) in nature (i.e. on planet Earth) is infinitely going through water cycle, and thus non-fresh water is sort of distilled into fresh, by this natural process.
My questions are:
- Where am I wrong in my assumption about natural water distillation (i.e. is rain water not as clean as it should be in theory)?
- Why don't we collect rain water (at least for plant watering, if it is not suitable for drinking)?
- Theoretically: after an animal consumed some amount of water, say a glass, how long will it take, given that animal just urinated on the ground, for that water to go through water cycle and become ready for drinking again?