MIT’s New Desalination System Produces Freshwater That Is “Cheaper Than Tap Water”
MIT’s New Desalination System Produces Freshwater That Is “Cheaper Than Tap Water”
MIT engineers and collaborators developed a solar-powered device that avoids the salt-clogging issues of other designs. Engineers at MIT and in China are aiming to turn seawater into drinking water with a completely passive device that is inspired by the ocean, and powered by the sun. In a pap
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The main problem I always hear with this is "where does the brine go?"
It can't easily be dumped without causing ecological chaos. In the water it can kill ocean life. On land it can make plant life never grow again in certain areas, also leeching into groundwater.
I love this technology buy am apprehensive about its deployment.
Sell it as edible salt.
This is the actual answer - you put this in evap fields with no run-off potential (so as not to harm fresh or salt water environments), dry your slurry through stages and then sell the salts commercially for further refinement and consumption.
Total US salt production is roughly 40 million metric tons (or 40 billion kg) per year.
Let's say we use this process to desalinate water for just 10% LA County's water needs. LA County currently uses 1.5mm acre-feet of water per year. In SI units, this is about 2 trillion liters each year.
There's about 35g of salt in each liter of seawater.
So... at just 10%, we're desalinating about 200 billion liters a year and producing 7 million tons of salt.
If we desalinate for the rest of the state, or the rest of the Southwest, we'll easily be producing more salt each year than all of the mining activity nationwide.
At some point the excess salt will have no buyers, and we will still need to deal with it.
I'm a fan of the simpler approach: Build long-ass pipes out into the ocean, and slowly dilute the brine so that it's not concentrated in any one spot. The total salinity of the entire ocean will not change by any perceptible amount, so long as you don't drop heavy brine in any one spot.
Sorry, forgot to add sources:
Those are going to be some long as spipes indeed if you want to pump brine out without salt spots.
quite true, although we already have long ass pipes/cables in the ocean for phone/internet connections between continents. So it's entirely doable, and is already being done for another purpose besides salt.
Yeah. It may be "simple" but it's not going to be cheap. I still think it'll be cheaper than dedicating huge swaths of coastal land to become brine-drying fields, though.
I'm pretty sure we can find more uses for ocean salt. At the amounts we're talking about people will find uses for it. One of the things people tend to ignore is that ocean water contains a lot more than just salt. It also contains metals and organic compounds. Looking over the Wikipedia article there is a significant component of magnesium, sulpher, calcium, potassium, and bromine. There are even industries devoted to extracting sodium, magnesium, potassium, and calcium from sea water. If we substantially increase the desalination of sea water we could significantly reduce the cost of extracting them. With the amount of brine you're talking about it would pretty much be free to anyone who could find a use for it, since the alternative is diluting it and pumping it back into the ocean, which is pure cost. At that scale you could likely also extract trace components in significant quantities. The page mentions lithium and uranium were attempted in the past, with uranium never seeing industrial scale due to it being too expensive, but economies of scale and all that.
Under capitalism they'd not buy the excess because they want to keep the price up but this is a good path towards post scarcity with salt
It could be used in molten-salt batteries, however I'm not sure of how efficient the technology is.
Capitalism: purchase a snack food conglomerate, lobby to remove sodium from food labels, increase salt in snack foods dramatically, and sell at a loss; this will drive up demand for the desalinated water.
Edit: add HFCS to the food and sell it at a massive profit.
Put it in empty oil tankers and have them disperse it through the ocean. Might have to retrofit them to put a port that leads to the ocean but besides that should be pretty cheap. No reason that empty tanker heading back to Saudi Arabia can't be filled with brine.
That would likely make it much more expensive than tap water, rendering the device almost pointless except in cases where they probably couldn't afford it anyways.
Not an expert here but the word that comes screaming into my head seeing that is 'rust'. Would the brine be easier to deal with solidified into salt? Even edible?.
Like how some places get salt. Put it in a pool and let it evaporate in the sun
I wonder if we could evaporate to extract salt and recover water from the brine once any harmful products are filtered out of the brine
Idk. Sodium batteries? Dump it in the desert?