I've definitely swum in power plant wastewater.  That said, I'm from BC.  Since we're almost 100% reliant on hydro power, we call power plant wastewater "a river," and literally the only environmental concern about that water is that someone made a lake bigger 50 years ago, and they have a system in place to deal with the salmon life cycle disruptions caused by building a giant concrete wall in the middle of the river. <br><br>("someone made a lake bigger" is very reductionist - depending on the size of the dam in question, that can be a huge change to the region.  But the local dam is very small, mostly just big enough to regulate the water flowing out of the lake that is also our city's reservoir so we don't run out of water and we don't have massive floods when the big storms hit.  (We get them when the dam has to dump a lot of water in preparation for the next big storm when the power company didn't get their water management plan right.)  Making it also a power plant is really just a bonus.  So in my local case, it's not that big of an effect.  Also, the dam was built a very long time ago, and it seems likely that if there was going to be any significant fallout from that (see the Vajont Dam in Italy for "signifcant fallout"), it would have happened by now.)