> you can toss it back into the ocean (with appropriate dilution)
... what are you going use to dilute the brine? The water you just desalinated? What's the point then?
Seems to me if your input is seawater, and your output is a separated-out set of {fresh water, saltier sea water}, and you put the saltier sea water back in the sea, you're going to create a localized concentration of high salinity, no? Seems kind of unavoidable to me.
Not necessarily. You could mix it in processed sewage. Assuming processed sewage is appropriately disposed off in the sea at limited locations with precautions, this should work. One concern may be the sheer volume from desalination might overburden the sewage disposal.
... what are you going use to dilute the brine? The water you just desalinated? What's the point then?
Seems to me if your input is seawater, and your output is a separated-out set of {fresh water, saltier sea water}, and you put the saltier sea water back in the sea, you're going to create a localized concentration of high salinity, no? Seems kind of unavoidable to me.