Can't you just dump it back in the ocean where it came from?
The sea critters are already happy to swim around in it, and you're not going to meaningfully change the concentration of the ocean. You could mix it with sea water near the exit point to avoid temporarily raising the concentration there.
Nope, not if it's not carefully dispersed. Brine is denser than saltwater. It tends to sink to the bottom, where there is little wave action or tidal flow, and remain there. It's believed that many marine organisms are negatively affected by the increased salinity, although the overall impacts are not well understood.
The sea critters are already happy to swim around in it, and you're not going to meaningfully change the concentration of the ocean. You could mix it with sea water near the exit point to avoid temporarily raising the concentration there.