I wonder. It would have to dissolve, a big block of salt would take a while, kind of like the erosion of cliffs where the salt comes from in the first place. Eh, I guess you're right though, the fish wouldn't like that at all.

It doesn't need to be crystalline salt. Just mix the brine with seawater at a really high ratio of sea water to brine then dump that out. 100:1 ratio should be fine I would guess. Quick search suggests seawater salinity variance is already like 10%-15% or so. Even better if you pipe it offshore where currents will take it and not somewhere that doesn't circulate.

Yes, that's my point: if you're next to the ocean, disposing of brine is extremely easy.

You could put it back into old salt mines.

Even better, just package it up and eat it instead of digging underground and creating more pollution.

It's not every day that industrial waste happens to be not only edible but also tasty. Too tasty, in fact. Salt is addictive.

It’s not going to be pure NaCl though; making Morton salt with it would make sense only if it wouldn’t cost more to process it (net of its resale value) than just disposing of it somewhere not particularly sensitive. I’d propose the Utah salt flats or indeed, kinda love the idea of just sticking them in a salt mine that is all tapped out. If it used to be chock full of salt it seems pretty environmentally fair to make it salty again.

The impurities are exactly what give sea salt from various regions their distinctive flavors and mineral profiles. The salt should be edible as long as it wasn't pulled from seriously polluted waters. It might even sell for a premium.