Of course water is not destroyed. It gets contaminated. And to clean it up, you need energy. Basically, we can simplify those equation to pretty much single argument: energy. Whatever you do, it needs energy. And people really really comes very lighty to that problem and waste management. If we would really like to recycle everything property I suspect global energy usage 10x fold at least. For now, its just better (I mean more economical) to just "store" that waste somewhere.