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New method turns ocean water into drinking water, without waste

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Re: New method turns ocean water into drinking water, without waste

#81

Post by cyberax »

ajb wrote: post #4

There is a fundamental minimum amount of energy needed to desalinate: you can't take less energy to do it,than you could gain back (from osmotic pressure) if you allowed the desalinated water to expand a cylinder containing the residual brine. This is large. This paper is a thermal method, so it doesn't have an electricity input, but to justify their efficiency claim, they should really compare against what you could…

> My (limited) understanding is that conventional reverse osmosis is not far from the theoretical optimum, energy-wise, the main difficulties being operational (the membranes need declogging). And of course RO is more expensive than rain.

RO is about 2-4x the theoretical minimum, depending on how much water you're willing to reject.

Re: New method turns ocean water into drinking water, without waste

#82

Post by wagwang »

LogicFailsMe wrote: post #34

So crazy question: take a dehumidifier, attach some solar panels, and deploy at scale for non-potable water suitable for crop irrigation anywhere that isn't a desert. Does it work? And if not, why?

The humid areas where they might work probably already have a lot of water?

Re: New method turns ocean water into drinking water, without waste

#83

Post by Joker_vD »

ceejayoz wrote: post #58
SoftTalker wrote: post #54

Earlier quoted context omitted.

The brine came from the ocean. So just dilute it back to close to ambient salinity using municipal waste water that you are discharging anyway.

> The brine came from the ocean. Sure, and enriched uranium comes from the ground, but that doesn't mean it's safe to dump it back in after the enrichment process! > So just dilute it back to close to ambient salinity using municipal waste water… Wouldn't it generally be easier to process that municipal waste water, as is already fairly common?

> Sure, and enriched uranium comes from the ground

Uranium can also come from the ocean water (there is, apparently, quite a lot of it in there, relatively speaking). Japan experimented with the technology in the nineties, but it really was much cheaper to just mine it from the ground, so they abandoned it.

Re: New method turns ocean water into drinking water, without waste

#84

Post by threwrfaway »

ceejayoz wrote: post #67
SoftTalker wrote: post #65

Earlier quoted context omitted.

You could just dilute it using fresh seawater, if you used enough and (maybe) spread it over a wider area. The amount of water people need for drinking is a relative drop in the ocean.

Brine doesn't necessarily behave the way you imagine. https://en.wikipedia.org/wiki/Brinicle https://en.wikipedia.org/wiki/Brine_pool

You can dilute the brine in a facility before disposing.

Re: New method turns ocean water into drinking water, without waste

#85

Post by noripcord »

card_zero wrote: post #66
noripcord wrote: post #56

you can now extract (like mining) minerals from the ocean, sounds kind of dangerous for the ecosystem maybe? making it profitable to extract magnesium, lithium, salt... we can probably guess how this story goes. i'm hoping it doesn't scale, honestly.

You're worried we might use all the salt in the sea for some kind of ... salt pyramids, send the water back out through sewers, and consequently leave the world's oceans diluted? That's about 1 followed by 21 zeroes, I think, in liters.

no, just take the water, remove the salt & minerals. Over time it'll dilute. Water falls again in the form of rain, obviously, but not the salt.

You're not worried? If it's for batteries? For sure they'll extract whatever they can.

Re: New method turns ocean water into drinking water, without waste

#86

Post by XorNot »

joshred wrote: post #7
rconti wrote: post #5

Earlier quoted context omitted.

Sure, but typically desalination plants are located in a single physical place, so a discharge pipe dumping brine 24x7 is bad for all of the things around it, as the local concentration is extremely high.

Seems like you could run a long perforated tube to diminish that effect.

The short version is brine is weird: it's surprisingly resistant to diffusing and tends to flow more like an immisicible fluid. So you have to put quite a lot of effort into getting it to actually disperse rather then just fall to the seafloor.

Re: New method turns ocean water into drinking water, without waste

#87

Post by gaiagraphia »

jrumbut wrote: post #79
gaiagraphia wrote: post #78

Always wondered why the coast of the Red Sea isn't littered with channels which get flooded with seawater, which then evpporate into glassed ceilings; creating freshwater, and leaving behind salts for mining. Sand -> Glass -> heated saltwater -> freshwater + minerals -> ??? -> profit? Combined with some mangrove farms, surely desert coasts are able to support more life. Wonder if this is scalable tech, and how quickl…

If you've ever been to the beach, you can smell the salt air and rotting seaweed and hear the birds. It's all gonna get on the glass (from above and below), and eventually the salt left behind is going to build up. The salt left behind is very hard on any structure or machinery used to move it which makes repairing the large glass enclosure a pain. All this for a slow trickle of water is generally not worth it.

The Saudis were fucking around with the idea of solar domes at one point. Haven't heard anything about it for a while though (probably due to maths, lol). A shame, I've always been fascinated by Egypt and the empty expanses of nothingness. On long bus journeys around the country, the imagination can run wild.

https://www.solarwaterplc.com/featured-news/whats-inside-thi...

Re: New method turns ocean water into drinking water, without waste

#88

Post by gaiagraphia »

dirt_like wrote: post #80
gaiagraphia wrote: post #78

Always wondered why the coast of the Red Sea isn't littered with channels which get flooded with seawater, which then evpporate into glassed ceilings; creating freshwater, and leaving behind salts for mining. Sand -> Glass -> heated saltwater -> freshwater + minerals -> ??? -> profit? Combined with some mangrove farms, surely desert coasts are able to support more life. Wonder if this is scalable tech, and how quickl…

Slightly different idea to take Red Sea water, concentrate it, and flow into the Dead Sea to stabilize the water level in the Dead Sea which is a big problem. A billion or so was spent but the project is on hold for some combination of financial, political and environmental issues. https://en.wikipedia.org/wiki/Red_Sea%E2%80%93Dead_Sea_Water...

I love projects like this. A shame the west has handed over the baton to the Chinese and Saudis when it comes to actually being daring with megaprojects.

Some over stuff whhich are cool to read about:

Redirecting Siberian rivers into Central Asia https://en.wikipedia.org/wiki/Northern_river_reversal

Redirecting Congo basin rivers to replenish Lake Chad https://en.wikipedia.org/wiki/Lake_Chad_replenishment_projec...

Filling in a depression in Egyptian Sahara desert and fllooding it with Mediterrraanean water to generate huuuuuuuuuuuuge hydro https://en.wikipedia.org/wiki/Qattara_Depression_Project

(Similar ideas proposed for Lake Eyre, the lakes in Tunisia, and the Afar Depression in Djibouti, too).

Re: New method turns ocean water into drinking water, without waste

#89

Post by card_zero »

noripcord wrote: post #85
card_zero wrote: post #66

Earlier quoted context omitted.

You're worried we might use all the salt in the sea for some kind of ... salt pyramids, send the water back out through sewers, and consequently leave the world's oceans diluted? That's about 1 followed by 21 zeroes, I think, in liters.

no, just take the water, remove the salt & minerals. Over time it'll dilute. Water falls again in the form of rain, obviously, but not the salt. You're not worried? If it's for batteries? For sure they'll extract whatever they can.

Right, remove the salt and minerals. We don't need that much salt, so we'd have to build pyramids or something with it. We drink the water, but then it ends up back in the oceans. The reason I mention that part is because if it didn't, if we could destroy the water, then the remaining water would retain the same salinity, and the concern would be that we drain the ocean dry, which is silly (I refer you back to how big it is). But we don't destroy water when we use it, so instead the worry is that we dilute all the world's ocean, which is also silly (I again refer you back to how big it is). We need a lot of batteries, but the sea is not useful as a source of lithium except as a byproduct. Even if it was the only source, the old batteries themselves would soon become a better source, as concentrated stores of lithium compared to the very-much-not-concentrated lithium in the ocean. But anyway the good places to mine lithium are on land (and are dried-up bits of ancient ocean, I think).

(I checked, some deposits are old lakebeds like https://en.wikipedia.org/wiki/Salar_de_Uyuni and others are igneous.)

It's also possible - true, I bet - that all the car batteries and storage batteries 8 billion people could possibly use are equivalent to only a tiny fraction of all the lithium in the ocean, but it would be harder arithmetic to confirm that, as well as being irrelevant on account of land-based mines existing.

Re: New method turns ocean water into drinking water, without waste

#90

Post by cyanydeez »

xyzzyz wrote: post #44
ajb wrote: post #4

There is a fundamental minimum amount of energy needed to desalinate: you can't take less energy to do it,than you could gain back (from osmotic pressure) if you allowed the desalinated water to expand a cylinder containing the residual brine. This is large. This paper is a thermal method, so it doesn't have an electricity input, but to justify their efficiency claim, they should really compare against what you could…

Brine is very easy to dispose of: you just pump it back to where it came from. Solid crystalline salt, on the other hand, is a hassle.

yeah, if you like to kill everything in a few 100 feet radius and kill some more in the zone of reliance.

this is delusional ecological

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