There are no perfect solutions.

Of course, we'll put the brine back into the ocean. We can run pipelines out miles to disperse the brine and dilute it. We'll need regulation to ensure this, because no capitalist corporation will do anything that cuts into profits without regulations forcing it.

Second only to air, fresh water is what we all need. We'll do what we must to have it. Of this I'm certain.

Would it be posible to salinate the waste water that goes back to the ocean from treatment plants?

I've always wondered why we can't contain the brine and pack it into abandoned salt mines for long-term storage. It would probably inspire some maintenance on abandoned salt mines and prevent cave-ins.

Maybe have ocean voyaging ships (e.g. container ships) do controlled release of brine through their journey?

Though probably no way of achieving this via current economic and legal systems. Even if attempted today, ships would probably be incentivized to dump the entire payload the moment they cross into internal waters.

Clump it into a big ball and send to space!

Scooped out and put where?

Depends if they also evaporate.

Most molecules aren't smaller than water, however filters that are small enough to only let water through clog pretty quickly. That said, most heavy metals and salts won't evaporate in a decent still (which is good, because atoms and ions are often smaller than water). I'm not sure about PFAS and microplastics, but I expect they don't evaporate.

You are ignoring that saltwater is available in many, many more places than freshwater. Building a local efficient desalination plant can absolutely be more cost-efficient than transporting freshwater for hundreds of kilometres. Don't simplify so much you lose all perspective.

My presumption is that the desalinated water might be cheaper than tap, but would still require further processing to be considered potable, which would raise the price on par or above conventionally sourced tap water. I imagine there’s a lot of costal areas though with ready access to saltwater and minimal access to freshwater where it’s worthwhile.

It won’t be cheaper than tap water.

Wait a few years.

That guy was annoying as hell.

It is the same thing.