Published on June 30th, 2013 | by James Ayre


Desalination With Small Electrical Fields — Simple New Method May Revolutionize Seawater Desalination

June 30th, 2013 by  

Seawater desalination with nothing more than a small electrical field? A simple new method of creating freshwater from seawater — that uses far less energy than conventional methods do — has just been developed by researchers at the University of Texas at Austin and the University of Marburg in Germany.

"A prototype 'water chip' developed by researchers at The University of Texas at Austin in collaboration with a startup company." Image Credit: University of Texas at Austin

“A prototype ‘water chip’ developed by researchers at The University of Texas at Austin in collaboration with a startup company.”
Image Credit: University of Texas at Austin

The new method — electrochemically mediated seawater desalination — uses no membranes, is considerably simpler than conventional methods, and is so low-energy that it can be performed with the energy provided by store-bought batteries. Those are big improvements on all fronts — if the process can be adequately scaled up, it’s a potentially revolutionary development. Freshwater scarcity is expected to become a significant problem in many regions of the world in the coming decades, but as it stands now, saltwater desalination isn’t particularly economical…. A cheaper, simpler method than those currently available would be of great use — one which could be used on larger scales than simple solar stills are.

The new method/technology is patent-pending and is currently in commercial development by startup company Okeanos Technologies.

“The availability of water for drinking and crop irrigation is one of the most basic requirements for maintaining and improving human health,” said Richard Crooks of The University of Texas at Austin. “Seawater desalination is one way to address this need, but most current methods for desalinating water rely on expensive and easily contaminated membranes. The membrane-free method we’ve developed still needs to be refined and scaled up, but if we can succeed at that, then one day it might be possible to provide fresh water on a massive scale using a simple, even portable, system.”

The researchers think that the new method could be of particular use to those in the world’s poorer, more water-stressed regions — more than a third of the world’s people live in such regions. While lacking in freshwater, the majority of these regions have access to vast seawater resources, just not an economical means to desalinate it.

“People are dying because of a lack of freshwater,” said Tony Frudakis, founder and CEO of Okeanos Technologies. “And they’ll continue to do so until there is some kind of breakthrough, and that is what we are hoping our technology will represent.”

The University of Texas at Austin explains the method:

To achieve desalination, the researchers apply a small voltage (3.0 volts) to a plastic chip filled with seawater. The chip contains a microchannel with two branches. At the junction of the channel an embedded electrode neutralizes some of the chloride ions in seawater to create an “ion depletion zone” that increases the local electric field compared with the rest of the channel. This change in the electric field is sufficient to redirect salts into one branch, allowing desalinated water to pass through the other branch.

“The neutralization reaction occurring at the electrode is key to removing the salts in seawater,” stated Kyle Knust, a graduate student and co-author on the new research paper.

“Like a troll at the foot of the bridge, the ion depletion zone prevents salt from passing through, resulting in the production of freshwater.”

As of now, the best that the researchers have achieved is 25% desalination — drinking water requires 99% desalination. The researchers are confident, though, that the 99% goal is very achievable.

“This was a proof of principle,” stated Knust. “We’ve made comparable performance improvements while developing other applications based on the formation of an ion depletion zone. That suggests that 99% desalination is not beyond our reach.”

The process will also need to be scaled up — as of right now, the microchannels are about the size of a human hair, and produce about 40 nanoliters of desalted water per minute. In order for the technology to be of practical use, a device would have to produce several liters — at least — of water per day.

The researchers are confident that this can be achieved, creating “a future in which the technology is deployed at different scales to meet different needs.”

“You could build a disaster relief array or a municipal-scale unit,” said Frudakis. “Okeanos has even contemplated building a small system that would look like a Coke machine and would operate in a standalone fashion to produce enough water for a small village.”

The new research was just published in the journal Angewandte Chemie.

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About the Author

's background is predominantly in geopolitics and history, but he has an obsessive interest in pretty much everything. After an early life spent in the Imperial Free City of Dortmund, James followed the river Ruhr to Cofbuokheim, where he attended the University of Astnide. And where he also briefly considered entering the coal mining business. He currently writes for a living, on a broad variety of subjects, ranging from science, to politics, to military history, to renewable energy. You can follow his work on Google+.

  • Vinay N

    I had this idea in 2006, but none of the technology transfer people were interested in my back of an envelope calculation which showed it could work.

  • Orville

    Bagging it too hard is a bit like looking at the Wright bros first flight and commenting “I can’t ever see it lifting a hundred tons and flying at 500 mph”.

  • agelbert

    Twenty five % desalination has a huge application right now! At present, the desalination plants along the Persian Gulf are causing over concentration of high salt % sea water where the plants are. This is killing sea life that requires a normal salt concentration in the sea water.. If they can use this method to treat the thick brine before it reaches the sea (and maybe harvest sea salt as a byproduct to sell), it could help the environment and pay for itself in salt exports.
    All desalination plants should be required to NOT put high salt concentration brine in the ocean.

    • Bob_Wallace

      What’s the math on that? How many gallons of water at what level of concentration are being returned? How large is the Persian Gulf and what is the water exchange rate?

      I’m kinda thinking that the amounts here are not important.

      • agelbert

        Here’s some “math” for you. I don’t write this stuff here just to read my words, Bob. These are comments, not articles. I don’t have to give you chapter and verse. You’ve got google just like I do. If you disagree with something anybody here writes, just research it and challenge it.

        The Gulf is a small water body, it is more like a lake,” he said. “It is open to the ocean at the Strait of Hormuz, but because the opening is narrow, water is replaced once every eight to nine years.”

        “Between the tankers, pollution from urban centres and the brine disposed from desalination plants, the Gulf is almost dead.” Because of its shallowness and the high evaporation rates in the hot summer season, the Gulf is one of the saltiest seas, and this is already a challenge for even the latest desalination technologies.

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        • Bob_Wallace

          ” I don’t have to give you chapter and verse. You’ve got google just like
          I do. If you disagree with something anybody here writes, just research
          it and challenge it.”

          Got to say that brought a smile to my face. Considering all the time I spend backing up my comments.

          • agelbert

            Glad to be of service. :>)

    • Nathan Rogers

      Then you are misunderstanding the terms used by the author. 25% desalination means that 25% of the salt was removed. In other words the water is still too salty to be drinkable by a long shot. 99% desalination means that 99% of the salt is removed bringing it down to a palatable usable level.

  • Tahuaya Armijo

    Water, water, everywhere but not a drop to drink. The Rime of the Ancyent Marinere by Samuel Taylor Coleridge was on to something.
    Lack of fresh water is a barrier to development and keeps many in poverty. This might not work out but I am thankful that many people are working on this problem. Someday, the problem will be solved.
    By the way, Ancyent Marinere is not misspelled. That was the way it was originally written.

  • BlueJay

    There are a couple of problems here… first of all, 3V is twice the voltage needed to electrolytically decompose water into hydrogen and oxygen… and that means the method, right now, has an abysmally low thermodynamic efficiency. One would expect that a few hundred mV can get the trick done. This may require to reduce the size of the device by a factor of 10, though, which would reduce the flow by up to five orders of magnitude (I don’t know if the laminar flow theory for pipes applies to these small geometries, but I guess it does). And with that, the total throughput would be far to small.

    • Rich

      So……what are you trying to say……

    • Sully

      Well laminar flow theories definitely still apply even on a micro or nano scale – ‘Microfluidics.’ We always only hear about integrated circuits and new chips but there is plenty of research to develop microfluidic systems for things like drug delivery and now apparently water desalination. It’s just research done in a University…there’s quite a ways further to go.

  • guenter strubinsky

    It was developed by Universities – I would expect the patent to be sought for the sole reason that no commercial profiteering can be made. Universities -especially those funded indirectly by tax payers- pay that way back to society. There should be no financial interest in propagating the new technology to those in need.

    • BlueJay

      That’s not how it works. The university gets the patent to license it to private companies. Licensors will pay an upfront fee, then milestones and eventually royalties, when the IP becomes a profitable product.

      Universities need these revenue streams. Research grants are given solely for the purpose of research and they usually only pay the researcher’s salary and, with some luck, materials. They do not pay for buildings, administrative costs or even the office supplies. There are very tight rules what research grants can and can not be used for. Grant management is a complex and often frustrating matter.

      In order to pay for the additional costs of the university, the government usually lets it keep the IP that stems from publicly funded research. There are counterexamples, like in the defense space and in case of certain vaccines, but it is usually the university which gets unlimited rights to out-license.

      Now, in this case I wouldn’t worry. I can see several problems with this invention, already. This may never work wall to begin with.

  • nadya suleman

    there are 100 different methods already ahead of this…jeez what a long way to go…no story her move along’.’.’.’.’.’.

  • Andres Espina

    To increase the overall performance of the desalination by ion depletion, the 25% desalinated water could be passed thru several stages. Also, the addition of a centrifugal force might help to the electric field to separate the heavier brine from the freshwater.

  • Jouni Valkonen

    With cheaper and cheaper solar panels water desalination will come very attractive on environmental standpoint. If all agriculture products are produced on deserts or vertically, this would free up the size of South America land mass of the most fertile soil for Nature.

    As more than 99 % R&D star-up firms fail, I would not put my money on this either, but membraneless desalination would be nice, because it is cheaper and presumably longer lasting. Energy requirements are non-issue where there is scarcity of fresh water!

    • Xira

      Unless you just use guns to keep the masses of dying people outside the gates where all the expensive water is stored. Then your choices become death by dehydration or death by gunshot.

      An entirely likely outcome for our country. <- my blog

      • agelbert

        The “blue gold” future water scarcity panic is just an excuse to try to jack up the price of potable water.

        As long as people have a SMALL (it doesn’t need to be more than a few kW) solar panel , a water generator and a relative humidity above 30%, they WILL ALWAYS HAVE FRESH, POTABLE WATER.

        Water generators are available for a family of four for about $1,000. AND, if they were mass produced like cars are, could be SO CHEAP that ALL PLUMBING INFRASTRUCTURE EVERYWHERE would be UNNECESSARY.

        Scoff if you want. Just like individually distributed power in homes from PV or wind eliminates the need for a centralized power utility AND saves about 15% on energy from transmission line loses, individually distributed water generation would save BILLIONS in water pipes and treatment facilities. Same deal for sewage (distributed compost and fertilizer making in homes beats sewage treatment plants!).


        The logical answer to the world’s fresh water crisis.”

        • Bob_Wallace

          I assume you’re low on facts.

          You’re shouting.

          • agelbert

            You assume wrong. You can check my facts using google just like anybody else out there. Are getting lazy in your old age?
            I’ll avoid caps from now on since that seems to get your drawers in a bunch. I’m surprised someone like you that has lived off grid hasn’t done the math on what is costs to provide a nationwide potable water pipe network and how unnecessary water generators in every home would make said network. The millions of dollars saved in avoiding fixing burst frozen water lines alone would be worth it. Instead of saying, “Hear, Hear!”, you come at me with some classroom professorial pseudo-erudite snark.

            Have a nice day, PAL!

          • Bob_Wallace

            I tried to check some facts on the device you’re hawking.

            I found none. Just some testimonials, one from a person whom I know was fired from a major web site for making stuff up. No independent testing.

            I rather doubt you’ve considered the cost of providing houses with $2,695 “water capturing from the atmosphere” devices and the 7 kW per day to run them. At $2/watt that would be another $3,000 or so.

            The cost of repairing frozen water lines would certainly pale in comparison.

          • agelbert

            Bob, they are not mass produced now are they. No, I don’t have one. I just know that as long as you are not in a desert, you can reclaim water from the atmosphere and keep it pure with a germicidal UV light.
            No more pipes, no more work crews digging for them or laying them, radically changed site preparation for houses along with less no city water purification plants using chemicals.
            Use your imagination Bob. You sound like those people that say EV cars will never work because they cost too much. Shame on you.

          • Bob_Wallace

            I can use my imagination. But I can’t dream up a large enough fantasy to make this approach work.

            Close to $10k for 17 liters of water a day.

            Time to return to the days of a weekly bath with all the family using the same tub full….

          • agelbert

            I’m down to three times a week so I’m working on it. :>)
            But, you know, you haven’t subtracted from your numbers what people now pay for plastic bottled water in plastic one, two and five gallon containers. That would all disappear. And at first people could just use their machines for drinking water. This uses a lot less energy than your numbers are pointing at.
            Finally, our infrastructure has been given D to F by our own engineers. Do you think they are just talking about roads and bridges!!? Some of water pipes are over a century old (In Rutland they have some hallowed out logs in some places).
            All these pipes need upgrading and we don’t have the money. I think evaporation and condensation is what the biosphere favors for moving water around this planet and we should do the same.

          • Bob_Wallace

            I don’t buy water. But I notice that you can fill a gallon container at my grocery store for $0.10/gallon. 17 liters. 4.5 gallons. $0.45 per day. $164.25 per year. 60 year payback, assuming everything works without problem for 60 years.

            I guess I could do the math with boutique water, but it seems pointless when one considers the amount produced.

            4.5 gallons. That’s drinking, cooking and some careful dish washing for a family. A “gallon bucket” bath every few days.

            No toilet flushes there. No laundry.

            “All these pipes need upgrading and we don’t have the money.”

            I feel like I’ve fallen down the rabbit hole….

          • agelbert

            A deep and expensive rabbit hole:

            [High-quality drinking water and wastewater systems are essential to public health, business and quality of life. The American Water Works Association and others have documented that water and wastewater infrastructure in North America is aging and that many communities must significantly increase their levels of investment in its repair and rehabilitation to protect public health and safety and to maintain environmental standards.

            Local role

            AWWA believes the public is best served by water and wastewater systems that are self-sustaining through rates and other local charges. In 2005 the United States invested $84 billion to build, operate and maintain water and wastewater infrastructure, with more than 95 percent of those funds representing state and local monies without federal assistance or subsidies, according to the U.S. Conference of Mayors.]


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