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New method turns ocean water into drinking water, without waste

rochester.edu

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

#51

Post by [deleted] »

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.

[deleted]

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

#52

Post by qurren »

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.

Why? Just build mountains out of it and maybe even open a salt-ski park in the tropics for people who don't have snow.

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

#54

Post by SoftTalker »

ceejayoz wrote: post #48
xyzzyz wrote: post #44

Earlier quoted context omitted.

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.

> Brine is very easy to dispose of: you just pump it back to where it came from. Easy, but not necessarily good for the spot you're pumping concentrated salt back into.

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.

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

#55

Post by galaxyLogic »

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.

I think I read somewhere that salt can be used as energy storage medium? So we could get both water and batteries for renewal energy.

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

#57

Post by SoftTalker »

LogicFailsMe wrote: post #41
LarsAlereon wrote: post #40

Earlier quoted context omitted.

It takes too much energy and produces water too slowly to scale. In general any area with sufficient moisture in the air to explore this also has easier access to rain and ground water.

Great point, in my case in the PNW, the water from my local well is infested with manganese (as in clogging the household plumbing in the absence of a sediment filter) and other contaminants and the water company providing it is owned by private equity. Legally, I can drill my own well for non-potable irrigation, but god forbid I filter and/or chlorinate it for my own household use. So I end up considering options li…

You don't need to chlorinate water from your own well, unless maybe you have a cistern that you are filling for storage.

And who's going to know if you are drinking it or watering your garden?

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

#58

Post by ceejayoz »

SoftTalker wrote: post #54
ceejayoz wrote: post #48

Earlier quoted context omitted.

> Brine is very easy to dispose of: you just pump it back to where it came from. Easy, but not necessarily good for the spot you're pumping concentrated salt back into.

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?

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

#59

Post by Animats »

Nifty3929 wrote: post #31
Animats wrote: post #29

The paper: [1] They're still at lab scale in glass. They haven't built a usable system, even a small one. The big claim here is that it doesn't clog; capillary action moves the salt out of the active area to another area, where some yet to be developed mechanism removes it. That needs to be demonstrated. If they can come up with something that runs for years without clogging or replacing the active material, that's a…

It reminds me of how the Panama canal was built, and actually the first major attempt failed and they gave up. What they learned for the second attempt was that digging was not the hard(est) part to solve - it was how to move the dirt! So much dirt! Great book on this BTW: Path Between the Seas. I couldn't put it down.

Fragility is a common problem in surface treatments, sometimes called "nanotechnology". There are super hydrophobic surface treatments that are very effective. They generate a surface which is a forest of tiny sharp points. The surface tension of water is too high to cling to such a surface. You can make something that just will not get wet. The problem is that the points are fragile, and wear destroys the effect.

Another example is ultra black coatings. Those are a forest of tiny black objects arranged so that light gets reflected multiple times and is absorbed. The commercial version is called "Vantablack". It doesn't wear well, but for optical applications such as the insides of camera lenses and telescopes, that's fine.

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

#60

Post by SoftTalker »

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?

The analogy would be if you "un-enrich" it. Then it's safe. Or at least no worse than when you took it out of the ground.
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