That water isn’t spilled, it is fed back to the water cycle. The water we use here has absolutely nothing to do with drought in Africa and other countries. Also, saying billions when there are only 7 billion people around sounds somewhat exaggerated.
Phosphoric acid doesn’t destroy very rare habitat’s irreversibly. At the same time we use a lot less of it, so I think damage caused by it is a lot smaller than that of peat.
But I get your point, we should keep in mind the downside of whatever we do.