I was thinking more along the lines of the local environment where tons of salt is being pumped into the ocean, which may impact on local ecosystems....presumably it takes a while to disperse even while it is constantly being pumped. Which may be an issue, I don't really know.
It doesn't take long to disperse. It's the ocean, it has currents and Eddie's.
Make your discharge pipes long--release it below the level where most things live.
Most things having consequences, I wonder what the downside to large scale world wide desalinization may turn out to be.
It would be salt; discharged back into the sea, it would create massive, hypersaline dead zones.
"Eventual dispersion" doesn't matter. In most places dispersion would be slow: witness the eutrophic dead zones at the mouth of the Mississippi, or in some of the American Great Lakes -- and eutrophication is slow. Hypersalinity is fast. It can kill fish, coral or phytoplankton in minutes.
The discharge water isn't all that salty. My understanding is that desalinization is normally done by reverse osmosis. As fresh water is extracted the salinity on the salty side goes up, it's harder to pump. Thus you are better off discharging the water without raising the salinity too much, especially if you have a system to recapture some of that energy. (You have high pressure water in the discharge--use that to turn a pump which pumps in more water. It's not 100% efficient so you still need power but not as much.)
Also, overall salinity is actually dropping with melting glaciers permanently adding fresh water, while the water taken out doesn't stay out very long.
Also, overall salinity is actually dropping with melting glaciers permanently adding fresh water, while the water taken out doesn't stay out very long.
It does if used for agriculture.
I drink water and expel the water same day. Water for agriculture takes much longer than a day to go back into the water cycle.
Longer, but on a scale to affect the salinity of the oceans it doesn't matter. And if it somehow became one do some old fashioned salt harvesting and toss the salt in a dry cave somewhere.
Just don't dump all brine in one place. Wikipedia says sea water must be treated with chemicals before processed in desalination plant and it could be a problem too. And 3 kWh per 1 m^3 of water, that's not that expensive
Looking at local rates we pay 10x as much for water as it would cost to desalinate that much water. It's not cost prohibitive by any means.