There is no coal ash in coal plant wastewater... that's literally stupid and ignorant. Coal ash made its way into the water due to the waste ash being stored near rivers.... and then containment failing. The water at a coal plant never comes in contact with anything from the combustion process in the same way water at a nuclear plant doesn't...  The wastewater at a coal steam plant is just water that has been used to cool the steam loop water in condenser loops....