Well, yeah,
just discard somewhere far away from the intake!
That doesn’t change the issue.
The effluent is very high salinity and toxic. Enough so that it will kill at the out fall.
If the currents push enough of the effluent to the inlets, you destroy the RO membranes or foul the evaporators.
All that doesn’t even touch the power requirements, which is well beyond what the grind can support.
This is going to be billions of gallons. It isn’t feasible. Most of the population in desert areas are going to have to move or die. You can not support millions of people in a place where you import or use wells for your water. It always ends the same.