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A big problem for desalination is the brine, the highly saline solution left over after the fresh water is removed. You can't just dump it in the sea again, bec
by yabones 3y ago
A big problem for desalination is the brine, the highly saline solution left over after the fresh water is removed. You can't just dump it in the sea again, because its high salt content will kill all of the fish, coral, kelp, etc. So you end up with a large retention pond full of dangerous water until it dries up, then the salt is put in a landfill. It's pretty far from sustainable.
- konschubert 3y agoBrine is just water plus the salt that was in the seawater before. You have to dilute it and spread it. But, sufficiently diluted, it’s just seawater. In a sense, it’s the same effect as water evaporating over the ocean: Water goes out and salt remains.
- nemomarx 3y agoIs there a good way to dilute it without using water?
- saalweachter 3y agoAs long as you can dilute it with salt water (until it's not deadly) that shouldn't be a problem.
- sithadmin 3y agoIt's not as easy as 'dilute and spread' -- highly concentrated brine doesn't really mix readily (halocline effect) when released back into the sea.
- konschubert 3y agoCouldn’t there be some kind of dilution step in the plant, using pumps to mix it 1:10 with seawater? After that, it’s just slightly more salty seawater.
- sithadmin 3y agoRelatively small differences in dissolved salts are enough to cause halocline barriers that don't really mix well and still pose a hazard to local flora/fauna.
- pixl97 3y agoTechnically uranium is in all kinds of soil in small amounts... turns out the poison is the dose. It starts getting really expensive moving a lot of heavy brine and attempting to dilute it, especially when the amounts of water you'll need will create mountains of salt.
- throwaway22032 3y agoWhy is it unsustainable to put the salt in a landfill? There's a lot of land. I mean, sure, technically it could run out over millenia or something?
- sithadmin 3y agoThe concentrated minerals and metals in the waste, as well as the chemical additives used during the desalination process, are incredibly difficult to contain given their solubility in water.
- eppp 3y agoThere is a lot of desert where desalination is typically used. Seems like putting problematic water soluble in places where the main problem is lack of water would work out ok. Unless they are also blown around by wind in some problematic way.
- enoch_r 3y agoIs this more of an issue for evaporated brine than for regular landfills? I thought that modern landfills had pretty advanced systems for preventing groundwater contamination, but it does seem possible that the problem is harder for water soluble brine.
- mensetmanusman 3y agoBrine is just concentrated lithium for batteries: https://www.csis.org/analysis/south-americas-lithium-triangle-opportunities-biden-administration https://www.csis.org/analysis/south-americas-lithium-triangl... If we are smart about it it’s a win win win. Unfortunately we don’t have the workforce to accelerate nuclear development as Greenpeace etc. scared away investment over many decades.
- enoch_r 3y agoThe US consumes about 322 billion gallons of water per day. There are about 66.5 cubic centimeters of salt in a gallon of water. If we bury the salt in 200-foot deep landfills, that's a total of roughly 32k acres per year, less than 2% of the total landfill capacity in the US (which is roughly 1.8M acres, less than 0.1% of the total land area, so there's plenty of room for more landfills if necessary). And of course that's assuming we use desalination for 100% of water use in the entire US.