IIRC These can have thier own host of problems because the 'brine' byproduct doesn't mix well back into the ocean and can settle/pool and create marine dead zones. Although suppose that will be less of a priority if people are thirsty.
The problem is strictly local: if the brine produced by the plant is dumped in an area with low flow, it can hang around and affect sea life.
If you use a big discharge pipe and put it a decent distance offshore in a current where it can mix effectively, there’s very little effect.
This is not a reason to shoot down desalination plants as a concept, it’s a design constraint to take into account when building them.
If you have ever flown into SFO you have seen the reddish pools. (By the way the red color comes from Brine Shrimp, which presumably there is also use for)
https://www.atlasobscura.com/places/salt-ponds-san-francisco
https://www.archdaily.com/994769/could-salt-be-a-material-of...
When you have a practically free resource which is waste from a large scale industrial process, cottage industries to make use of the free waste sometimes pop up. It's a solvable problem.
Is it just a case of the scale making it safe?
0: https://www.timeout.com/croatia/things-to-do/ston-salt-works
The brine slowly go down through geological layers. After 5 years it reaches groundwater reservoir.
20-50 years later, the regions become famous for its fun pod racing and for its numerous ghost cities around the old plain.
of course, a renewable powered ship
Skinner: Well, I was wrong; the lizards are a godsend.
Lisa: But isn't that a bit short-sighted? What happens when we're overrun by lizards?
Skinner: No problem. We simply release wave after wave of Chinese needle snakes. They'll wipe out the lizards.
Lisa: But aren't the snakes even worse?
Skinner: Yes, but we're prepared for that. We've lined up a fabulous type of gorilla that thrives on snake meat.
Lisa: But then we're stuck with gorillas!
Skinner: No, that's the beautiful part. When wintertime rolls around, the gorillas simply freeze to death.