The waste water from a coal power station is not the water that was used to produce steam to spin the turbines.  That water is very very clean and largely remains in a sealed system. <br>The water at the bottom of the cooling tower was used to cool the sealed system, but doesn't come in contact directly.<br>Generally the water is taken from a nearby river and when it's put back after use it's a lot cleaner than when it was taken out (and obviously thus gas to comply with strict regulations).  It's been known for the warm water to serve other purposes before returning to the river, for example used for an eel farm!<br><br>Another enjoyable video and I was happy to hear you on the no such thing as a fish podcast last week