It is hard and expensive to diffuse the brine that's left after the freshwater is extracted. The whole ocean is not affected but it's the area around the plant.

It is hard and expensive to diffuse the brine that's left after the freshwater is extracted. The whole ocean is not affected but it's the area around the plant. Which can be a very large. https://www.scientificamerican.com/article/slaking-the-worlds-thirst-with-seawater-dumps-toxic-brine-in-oceans/#:~:text=But%20desalination%20plants%20are%20energy,underground%20or%20spread%20on%20land https://www.scientificamerican.com/article/slaking-the-world....