There are two counterpoints to the issue of excess salt being an environmental hazard.
A) brine can be introduced back into the ocean combined with waste water. In the Cape Town drought of 2017 some small desalination plants were brought into service very quickly, and the brine was expelled in the same pipe as the outflow from a (treated waste) sewerage plant.
B) the ocean is big - very big - and at least by our coast seldom "calm". So outflow of anything would disperse very quickly. Hot-water outflow from a nuclear power station dissipates very quickly for example - typically within tens of metres of the outflow.
C) the natural salinity of the ocean varies a fair bit at the very local level - think river mouths - storm water - evaporation etc. Outside of specifc closed bodies of water (Dead Sea etc) we'd need desalination on a massive scale to even measure the impact.
A) brine can be introduced back into the ocean combined with waste water. In the Cape Town drought of 2017 some small desalination plants were brought into service very quickly, and the brine was expelled in the same pipe as the outflow from a (treated waste) sewerage plant.
B) the ocean is big - very big - and at least by our coast seldom "calm". So outflow of anything would disperse very quickly. Hot-water outflow from a nuclear power station dissipates very quickly for example - typically within tens of metres of the outflow.
C) the natural salinity of the ocean varies a fair bit at the very local level - think river mouths - storm water - evaporation etc. Outside of specifc closed bodies of water (Dead Sea etc) we'd need desalination on a massive scale to even measure the impact.