Why purify urine, the nutrients are already out?

Answer

Dear Amber,

it is true that normally little or no nutrients are present in our urine. But it is not just “water without nutrients”. Urine is e.g. mostly yellow, and water is not. So there are other substances in it: dyes and waste products (eg urea) that our body can do nothing with. It is important that these waste products are removed from the body, because if there are too much of it, it is harmful. The removal of these wastes is the job of the kidneys. They remove all harmful substances from the blood and, together with water, make urine. When purifying urine, the waste products are removed, so that drinkable water is created again.