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darkingz t1_j20pujr wrote

Reply to comment by Surur in UIUC Researchers propose a new way to get fresh water from seawater, without the disadvantages of traditional desalination. They say that a vertical “capture surface” that is 210 m wide and 100 m tall, could extract enough vapor floating above warm oceans to supply 500,000 people with freshwater by lughnasadh

The problem isn’t “the ocean” it’s the local environments.

The problem with brine is basically it’s toxic. You can’t really repurpose the salt and toxins that are filtered out for consumption. It’s especially bad if it happens in estuaries and small areas which really depended on fresh water. A single desal plant might help an area. The next problem is scale. Does this mean you can run 16 desal plants without issues? Not really.

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Surur t1_j215a9r wrote

Like I said, the closely monitored environment in San Diego has not shown any ill effects.

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SatanLifeProTips t1_j21it5s wrote

Brine only has 2-3x the local salt content. If you are running a giant RO system for every 1 litre of water I get out of the system I am creating around 0.5-0.6L of reject water at best. Maybe the new membranes can get down to 0.3? I don’t know what the state if the art is.

(I care for a RO system that can do 10,000L/hour).

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darkingz t1_j21q6c1 wrote

I haven’t read the full paper but: https://www.sciencedirect.com/science/article/abs/pii/S0025326X20308912

> A major issue of desalination is the co-produced waste called ‘brine’ or ‘reject’ which has a high salinity along with chemical residuals and is discharged into the marine environment. In addition to brine, other main issues are the high energy consumption of the desalination and brine treatment technologies as well as the air pollution due to emissions of greenhouse gasses (GHGs) and air pollutants. Other issues include entrainment and entrapment of marine species, and heavy use of chemicals.

It does suggest that depending on the type of desal, you’ll find different products and outputs. Part of it is that the water output could contain chemicals used to treat the water and other by products that still make it through the filter. The problem is that if you just blindly support desal, without considering environmental impacts, you definitely could run afoul and ruin multiple ecosystems easily. I am personally a little skeptical it can scale across the world to supply the fresh water needed for the human race without some impact to local ecosystems. I don’t think it’d impact the global ocean, so it’s kinda sus that the conversation is like “well the ocean is fine”. But the problem has always been the local environment, not a global ocean problem.

Edit:

To your comment, brine at 2-3x saltier than normal is pretty damaging to fish (and people) who aren’t used to that much brine. It’ll almost undeniably cause a lot of species to just die. That’s the problem. Life might adapt but it might not. And should we take a chance that the ecosystem will collapse?

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SatanLifeProTips t1_j2251y1 wrote

Hence why you put them in areas with ocean currents. Spend any time scuba diving? There are a LOT of areas that are absolute deserts in the ocean. Sandy and empty. There’s nothing around for miles.

And the currents. Oh my. Does water move. You get caught in one and you are going for a ride. Planning current dives is very popular. Relax in the current, go for a ride. Arrange for a boat to pick you up or sometimes it’s a long wall dive and you end up a long ways out.

The ocean? It’s big. Real big. Insanely big. As long as you have some water movement, you could put a city sized discharge pipe into of these areas and with a 2kph current the brine uptick would be basically undetectable 1km away. The sheer volume of water is nuts.

As long as you locate where water is moving and away from a big habitat area there is ZERO issues.

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sharksfuckyeah t1_j21w9py wrote

> You can’t really repurpose the salt and toxins that are filtered out for consumption.

Maybe we can, though:

https://energycapitalpower.com/researchers-develop-sea-salt-battery-4-times-the-capacity-of-lithium/

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darkingz t1_j21x46w wrote

That’s a way different thing than desal but does present an opportunity I suppose but the problem always comes to the unpure water products that come out.

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