The salt and minerals will go back into the ocean. They don’t use stills much anymore; desalinization is done with polymer membranes. The membranes will allow pure water through and not the salt and dissolved stuff. You wind up with pure water on one side of the membrane and extra salty water on the other.
I kinda figured as much but there is a vague “pee in the pool” aspect to dumping it back where you’re gonna pull more ;’)
That’s a lot of extra salty water to return to the sea but it seems the ocean could handle it. For the vast Pacific Ocean adding back extra salty water. would be a miniscule blip for california concerns.