Mass dilution is going to be fairly expensive because you have to move a significant multiple of the water you actually process. The brine waste water is roughly double the salinity of normal sea water at 70 ppt so to get back to the 33-37 ppt that's the real average band you're looking at moving a lot of sea water to dilute the output. If you run the numbers you're looking at 15:1 of volume to get 70ppt to 37ppt using 35ppt water all while ensuring you're at a place with enough natural mixing that your inputs and outputs don't start feeding back into each other.