Which is a different problem than your original comment. The ‘what to do with the brine’ is more or less covered by the article you linked. It’s not an unsolvable problem.
And the energy problem is what the original article is about, using solar energy.
The problem with comments like this is they make it sound like the issue is unsolvable when really it’s just a matter of engineering and balancing costs.
In the use case in the article, drawing saline from a saltwater aquifer, you could pump the brine right back down (in a different spot of course) to help maintain the pressure in the aquifer, maybe mixing it with treated wastewater (assuming you’re not simply recycling that to begin with, which would reduce the amount of fresh water that needs to be added to the system). You would need to model the aquifer to determine exactly where and how much brine you could pump in without ruining the feedwater quality, but that’s just part of the process.
If the feed comes from the ocean, you could dilute the brine right back into the ocean. You’d need to spread it out to avoid creating too intense of a salinity gradient, of course. The size of the required leach field might make this approach prohibitively expensive, but it’s at least worth looking into. Or again, you could mix it with treated wastewater that was likely heading out that direction anyway.
By the way, I have no idea if any of this is discussed in the article you linked because the site hit me with a paywall.
These are well known problems with desalination. The problem of “what to do with the salt” has been known for at least two decades, if not four. You literally can’t just “put it back” without fucking up the ocean wherever you dump it.
It doesn’t take much salt to make the ocean unlivable like the Dead Sea. It’s a huge problem and “make salt lamps” isn’t going to cut it.
Of course you’re going to cause problems if you just dump the brine back in the ocean in a single spot. That’s not at all what I was suggesting.
You do realize the ocean isn’t uniformly saline, right? There’s already natural gradients everywhere and most species of flora and fauna are going to tolerate certain ranges of it.
It doesn’t take much salt to make the ocean unlivable like the Dead Sea.
The Dead Sea is literally 10x more saline than the ocean average. 34% vs 3%.
Dumping into different spots to spread it out could be a solution. It would add expense to the process, though, and we know how capitalism handles that. As for aquifer charging, the brine is thicker than what was taken out. This adds to the problem in that you’ll need much higher pressure to drive it, or you’ll clog the system at the output point.
If you’re going to go the route of least expensive solution, find an area that is unattractive to human life, preferably a desert near the ocean. Pipe in the seawater, using RO to remove as much fresh water as possible. Then take the brine and send it out to evaporation beds covering a large area. You can recover some more water through that process, but, most importantly, removing the water and leaving the salts and minerals requires little energy input this way. The downside is the acreage required.
If you had a geothermal vent to provide heat, it would make the entire process almost carbon-neutral.
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