Our waterways are becoming more and more polluted due to PFAS, plastics, medicines, drugs, and new chemicals made by companies that just hand over the responsibility of cleaning to plants paid for by public moneys. Detecting the different chemicals and filtering them out if getting harder and harder. Could the simple solution of heating up past a point where even PFAS/forever chemicals decomposes (400C for PFAS, 500C to be more sure about other stuff) be alright?
Not how reactors work, they are very much closed systems specifically to avoid this problem.
Think of it like and air conditioner or refrigerator. The the attempt that cool the inside by dumping heat outside uses a closed loop and the two mediums do not directly interact or mix, which is why your home isn’t full of pollen when running an air conditioner all day if your windows and doors all properly seal.