The brine is a thing that needs handled, but there are ways to handle it.

Unfortunately it is the kind of thing where the best solutions, like drying it and storing the salts, or pumping it underground, are expensive (and therefore hard to convince anyone to use), and the cheap solutions, like just dumping it back in the ocean, can have severe negative effects, like killing everything in the water around where it is dumped.

Edit to add: although looking at this, depending on how they actually build it, it might sort of just turn ocean water into brine on the spot as it removes water. That would be basically like dumping it bqck in the ocean as far as effects, and doesn’t seem ideal