> I am singularly amused at the possibility of contaminating treated post-sewage water with river water It is bizarre, isn't it? I don't know about anyone els

> I am singularly amused at the possibility of contaminating treated post-sewage water with river water It is bizarre, isn't it? I don't know about anyone else, but I've spent most of my life thinking of rivers as quite polluted. Even when hiking in wilderness I take a giardia filter.