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I'll have a glass of sea water, hold the salt
March 24, 2010 9:42 AM   Subscribe

Researchers at MIT and in Korea have developed a new, efficient desalinization nanotechnology that could theoretically lead to small, portable units powered by solar cells or batteries, yet deliver enough potable fresh water from seawater to supply the needs of a family or small village. As an added bonus, the system would simultaneously remove many contaminants, viruses and bacteria. MIT Press Release. Abstract and Supplementary Information from Nature Nanotechnology. (pdf)

Also see Nanotechnology and Water Treatment for an overview.
posted by zarq (32 comments total) 19 users marked this as a favorite

 
Isn't the issue with desalination (besides its cost) that it's hard to get rid of the salt without poisoning the surrounding ecosystem?
posted by KokuRyu at 9:46 AM on March 24, 2010


But will Kevin Costner be able to use it to drink his own urine?

In all seriousness, if they can make affordable family-sized units this is really swell. Thanks, Scientists!
posted by GameDesignerBen at 9:47 AM on March 24, 2010 [2 favorites]


Didn't whassisname of Segway and stair-climbing-wheelchair fame do this several years ago and try to sell it to the UN for $1000 a pop?
posted by TomMelee at 9:49 AM on March 24, 2010


I wonder how well a village-scale of this would stack up against Dean Kamen's Slingshot, which, as far as I know, is a lot further down the production line.
posted by adipocere at 9:51 AM on March 24, 2010


KokuRyu, I think the bigger problem is the efficiency. On a small scale, pouring the brine back into the ocean is not going to have a significant affect on salinity. I can imagine it being a bigger problem on a large scale, but if these are designed to be small units, it should be fine.
posted by Aizkolari at 9:52 AM on March 24, 2010


"Do you realize what that could mean to the starving nations of the earth?"
"They'd have enough salt to last forever..!"
posted by Jinkeez at 9:52 AM on March 24, 2010 [5 favorites]


MIT and Korea have discovered the sheet of plastic?
posted by DU at 9:52 AM on March 24, 2010 [1 favorite]


t's hard to get rid of the salt without poisoning the surrounding ecosystem?

Sea Salt for everyone! Down with the Sel De Mer hegemony!
posted by The Whelk at 9:52 AM on March 24, 2010


From the article: ICP has been around for a while, says Han, but it's never been used to desalinate water.
...
So you could shower with water produced by ICP alone, says Kim, but you still wouldn't want to drink it.


Heh.
posted by filthy light thief at 10:03 AM on March 24, 2010 [1 favorite]


If researchers can scale up this invention into a working device, it could generate up to a glass of fresh water per minute using about the same energy as a table lamp does.

40 watts to produce one gallon every eight minutes seems like a lot of energy. Water, water everywhere, but still not enough electricity.
posted by three blind mice at 10:04 AM on March 24, 2010 [1 favorite]


40W doesn't seem all that bad. A person on a bicycle in reasonable shape can maintain 70W pretty easily for hours. I used to use a pedal-electric desk to power my laptop, which draws about 20W. Since the desk was only about 50% efficient, this meant producing 40W. It was quite easy, and actually meant I had to stop pedaling from time to time to avoid overloading the system.
posted by kaibutsu at 10:12 AM on March 24, 2010 [2 favorites]


40 watts to produce one gallon every eight minutes seems like a lot of energy. Water, water everywhere, but still not enough electricity.

Last year, First Solar announced that their thin photovoltaic solar panels would cost less than $1 per watt.

I want to know how large a panel would have to be to generate 40 watts.
posted by zarq at 10:13 AM on March 24, 2010


KokuRyu : Isn't the issue with desalination (besides its cost) that it's hard to get rid of the salt without poisoning the surrounding ecosystem?

If done the "dumb" way, yes, that counts as one of the issues.

If you consider desalination with an eye for Waste Stream Processing, you get two products for the price of one, with close to no actual "waste" - Fresh water, and sea salt. We currently pay to have millions (billions?) of tons of really really old sea salt dug out of the ground every year. Although admittedly salt forms such convenient deposits that this has close to zero cost, doing anything useful with what would otherwise count as waste amounts to a net gain.

<cheeseburger> And best of all, hipsters - sorry, "fauxhemians" - can buy both with their food stamps! </cheeseburger>


three blind mice : 40 watts to produce one gallon every eight minutes seems like a lot of energy. Water, water everywhere, but still not enough electricity.

Conveniently enough, the places that most need desalination plants also tend to have the best conditions for solar energy. Though personally, I consider it on the absurd side to convert all that nice cheap sunlight into electricity at less than 30% efficiency, when they could use it directly to heat the water (hell they could do both, since the other 70% just converts to waste heat). No doubt smarter people than me could explain why we don't do that, but I can't realistically see "energy" as the limiting factor in efficient desalination.
posted by pla at 10:16 AM on March 24, 2010


Whatever happened to the Slingshot?
posted by HumanComplex at 10:16 AM on March 24, 2010


I want to know how large a panel would have to be to generate 40 watts.

If we are talking 10% efficiency, about 1/2 m2.
posted by DU at 10:18 AM on March 24, 2010


I want to know how large a panel would have to be to generate 40 watts.

The rule of thumb is about 10 watts per square foot on a sunny day at noon in North America, give or take. YMMV.
posted by Cool Papa Bell at 10:20 AM on March 24, 2010 [1 favorite]


40 watts to produce one gallon every eight minutes seems like a lot of energy

You can buy a 40 watt solar panel today for under $300 US. Amazon is even listing some for under $200. Makes me wonder how much of my daily electricity use I could off-load to solar with a relatively meager investment in some panels...
posted by jsonic at 10:25 AM on March 24, 2010


Me: I want to know how large a panel would have to be to generate 40 watts.

DU: If we are talking 10% efficiency, about 1/2 m2.

Cool Papa Bell: The rule of thumb is about 10 watts per square foot on a sunny day at noon in North America, give or take. YMMV.

Assuming it can be folded like this one, that's pretty damned cool.
posted by zarq at 10:27 AM on March 24, 2010


I imagine a combination of solar and mechanical would make the most sense; use mechanical (bike generator, etc) for when demand is high, use solar for when you want to just let it run and fill up some kind of cistern.

I hope it works, this is one of those kinds of things that could make the world a vastly better place for a huge number of people.
posted by quin at 10:27 AM on March 24, 2010


Makes me wonder how much of my daily electricity use I could off-load to solar with a relatively meager investment in some panels...

We got an estimate from a solar installer a few months ago. About $30k to cover our average monthly usage of 650 kW-hours. I believe a little less than half the cost was materials.
posted by electroboy at 10:35 AM on March 24, 2010 [1 favorite]


Just another tool of civil disobedience.
posted by blue_beetle at 10:36 AM on March 24, 2010


At the local solar salt extraction ponds, the final, waste stage of the process is a big pond
of what they call bittern. It is rich in potassium salts which are much more soluble than
sodium salts. If they were to release it into the bay, it would indeed kill. The outflow from
this new process is just concentrated brine, with no relative enrichment of potassium salts.

The Sydney desalination plant uses Reverse Osmosis, and has the same basic problem
with concentrated brine waste that this new process might have. You can read
their environmental documentation here.

Basically, the Sydney plant dumps the effluent a little offshore, and asserts that the salinity
of the surrounding region is disturbed by one part per thousand at 50-75 meters from the
outflow (of which I suspect there are more than one, along the length of the disposal pipe).
posted by the Real Dan at 10:40 AM on March 24, 2010


"If you consider desalination with an eye for Waste Stream Processing, you get two products for the price of one, with close to no actual "waste" - Fresh water, and sea salt."

Normally that's true, but if this technology is used in disaster situations and third world countries with significant environmental degradation, there's probably going to be a lot of other stuff floating in the brine - like mercury and arsenic. So getting rid of the waste water might be troublesome, but with proper organization some kind of system could be set up to handle it. The thing that makes this so nifty is that it could potentially make desalination much cheaper and less material intensive, which would be good for everyone.
posted by Kevin Street at 10:55 AM on March 24, 2010


The Middle East has just gotten a lot more interesting.
posted by ZenMasterThis at 11:20 AM on March 24, 2010


With the RO process (and apparently, this process) you're not really getting sea salt in a usable form, you're getting a brine solution. There's a lot of things you can do so that you're not injecting really concentrated salt solutions into the body of water you're drawing from. One option is to mix it with the outflow from a wastewater treatment plant. A lot of municipalities are looking into desalination plants to maintain their water supplies. In coastal cities, in particular in California and Florida, they're experiencing saltwater intrusion issues resulting from pumping down groundwater aquifers.
posted by electroboy at 11:50 AM on March 24, 2010


electroboyIn coastal cities, in particular in California and Florida, they're experiencing saltwater intrusion issues resulting from pumping down groundwater aquifers.

Holy crap, they really do something that stupid???

"Hey, we already don't have enough fresh water - Let's poison what we do have with the concentrated waste from a more energy-intensive source of it!"

Not with a bang, but a whimper.
posted by pla at 12:12 PM on March 24, 2010


I wouldn't call it stupid, just poor long-term planning. If your water supply is based on a proven groundwater source and you suddenly discover that you're having intrusion issues (which is affected by soil types, depth of drawdown, rate of recharge, etc) what do you do? It's a multi-year process to identify and develop new sources, so you mostly have to limp along and find a way to provide services until your new source comes on line.

There are things you can do to mitigate seawater intrusion, but in a lot of places, the damage is done by the time it's discovered.

If this really does what they claim it does, the implications are pretty staggering, for everyone. Imagine if Los Angeles could economically use seawater instead of bringing it in from Nevada or the the Colorado River. Currently, so much of the Colorado is drawn for irrigation and municipal use, the US runs a reverse osmosis plant just north of the Mexican border to fulfill treaty obligations that state that the water must be of a minimum standard.
posted by electroboy at 12:27 PM on March 24, 2010


Noam Chomsky once opined that if a cheap, efficient method of desalinization could be found, it might have a significant impact on the Isreal-Palestine conflict. He argues that one of the primary reasons the Israelis insist on holding onto the territories is that it gives them control of large quantities of fresh water. If they could get drinking water from the ocean instead...

Well, it's a theory.
posted by Clay201 at 12:47 PM on March 24, 2010 [1 favorite]


Noam Chomsky once opined that if a cheap, efficient method of desalinization could be found, it might have a significant impact on the Isreal-Palestine conflict. He argues that one of the primary reasons the Israelis insist on holding onto the territories is that it gives them control of large quantities of fresh water. If they could get drinking water from the ocean instead...

Developing a drug that suppresses religious belief and surreptitiously spraying the entire region with it would probably be more effective, given how the very idea of something being "sacred" makes compromise impossible. I'd bet that six months later, the Israelis and Palestinians would be having friendly football matches against each other.
posted by acb at 6:28 PM on March 24, 2010


pla, the saltwater intrusion is just from seawater, not from brine disposal— if you pump the freshwater out of your well fast enough, instead of the groundwater flowing outwards towards the sea and keeping the seawater out, the seawater flows inwards and eventually gets to your well.
posted by hattifattener at 12:43 AM on March 25, 2010


hattifattener : if you pump the freshwater out of your well fast enough, instead of the groundwater flowing outwards towards the sea and keeping the seawater out, the seawater flows inwards and eventually gets to your well.

Okay, that makes a lot more sense to me... But then, what does that have to do with desalination?
posted by pla at 7:53 AM on March 25, 2010


If you can desalinate cheaply, you don't need to draw from groundwater sources, which would stop the subsurface saltwater intrusion.
posted by electroboy at 8:01 AM on March 25, 2010


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