I’ve seen several refineries and Chem plants that had to significantly clean the canal, river etc before the water can be used in the plant. The resulting release water is often cleaner than the original intake.
“I’ve seen several refineries and Chem plants that had to significantly clean the canal, river etc before the water can be used in the plant.”
Yes. Using multiple filters to remove mud, dirt and what have you to protect the cooling water system equipment from deposits, plugging, etc.
“The resulting release water is often cleaner than the original intake.”
No. Only “clearer” water. The back flush of filters using same river water is pumped back in the river. IOW, you saw the clearer water but not the back flush carrying what was in it in the first place because of a different exit point into the river downstream the first one.
Assuming not adding any chemicals to a one through cooling system, the effluent temperature shouldn’t exceed certain temperature according to regulation and may have to be cooled before pumping back to the river.