Battery Turns Saltwater Into Drinking Water

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Battery Turns Saltwater Into Drinking Water

Posted by timothy on Saturday February 11, 2012 @02:59AM from the we-call-it-elon-water dept.

An anonymous reader writes "German researchers have developed a battery that can remove sodium and chloride ions from seawater. In theory, their invention could be far more energy efficient than thermal desalination or reverse osmosis. This would cut the cost of using salt water for drinking or irrigation. It could also be used to make compact desalination systems for boats and life rafts, or crops. Each battery is made with manganese oxide nanorod electrodes, which absorb sodium when an electrical current passes through them. When the current is reversed, they dump the sodium ions out into waste water."

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How much energy? by CapOblivious2010 · 2012-02-11 03:03 · Score: 5, Interesting

Interesting, but how much energy does it take to run this thing? (they call it a 'battery', but I don't think it actually generates electricity). Many of the places that are short on fresh water are also short on electricity (especially "green" energy), so this may not be as helpful as it sounds.
1. Re:How much energy? by Smallpond · 2012-02-11 03:08 · Score: 5, Informative
  
  They call it a battery because it is a series of electrical cells. The term "battery" means the series arrangement; it comes from a military term for a series of guns. Generating electricity is the best-known use of an electrical battery, but isn't the definition.
2. Re:How much energy? by mrmeval · 2012-02-11 03:16 · Score: 2
  
  It's "an electrochemical cell that can desalinate seawater".
  You can thank Aaron Rowe for calling it a battery. I'm sure he plays with his food with his feet.
  
  --
  I'd go on a Vegan diet but the delivery time from Vega is too long. --brownkitty
3. Re:How much energy? by errandum · 2012-02-11 03:46 · Score: 4, Interesting
  
  What I'd really want to know is if it is more efficient to use a solar panel to charge the battery to then separate the salt or simply to use the sun to desalinate the water using the tradition process.
4. Re:How much energy? by jonadab · 2012-02-11 03:54 · Score: 5, Informative
  
  Batteries don't generate energy. They store it, chemically. (Well, the ones we usually think of as "batteries" work chemically.)
  
  Nonetheless, I don't know how they propose to be more energy efficient than a mirror-based distillation rig. Besides keeping the parabola aimed at the sun, which requires negligible energy, the main costs of running such a rig are keeping it supplied with water to distill and flushing it out with solvent once in a while to prevent salt buildup. (You can even use filtered seawater for the solvent.) The latter costs seem unavoidable for electrical-cell-based desalination, and the former is, as I said, negligible.
  
  Of course, it only works in parts of the world that get a lot of sunshine, so for example it would be a non-starter in northern Ohio. (Not that we need desalination in Ohio. Most of our water management issues involve finding ways to get the water to drain away more efficiently so it doesn't flood our basements; that seems likely to be common in places that don't get enough sunshine to boil water with a parabolic mirror... but I suppose there could be exceptions.)
  
  --
  Cut that out, or I will ship you to Norilsk in a box.
5. Re:How much energy? by tqk · 2012-02-11 03:59 · Score: 4, Informative
  
  Interesting, but how much energy does it take to run this thing? (they call it a 'battery', but I don't think it actually generates electricity).
  Re-read TFA. They came up with this desalination gizmo by reversing another gizmo that does create electrical energy.
  I think this's brilliant thinking. They didn't just read the paper. They read it, understood its implications, and extrapolated them in the opposite direction. That's what I expect from scientists. I wish I saw that kind of thinking more often.
  As for this gizmo, I'd like to see it built as a group of looping boxes, progressively yielding purer product as it goes through them in sequence. Add other boxes in the chain to filter out other stuff that this gizmo doesn't filter, and you end up with an office water-cooler machine that produces pure water and recyclable sludge. I'd definitely buy one!
  
  --
  "Tongue tied and twisted, just an Earth bound misfit ..." -- Pink Floyd.
6. Re:How much energy? by Jack+Malmostoso · 2012-02-11 04:06 · Score: 4, Informative
  
  Interesting, but how much energy does it take to run this thing?
  From the abstract: "Here, we demonstrate an energy consumption of 0.29 Wh lâ"1 for the removal of 25% salt using this novel desalination battery, which is promising when compared to reverse osmosis ( 0.2 Wh lâ"1), the most efficient technique presently available."
7. Re:How much energy? by brusewitz · 2012-02-11 04:34 · Score: 5, Funny
  
  Of course, it only works in parts of the world that get a lot of sunshine, so for example it would be a non-starter in northern Ohio.
  
  I think the fact that Ohio is not near any source of saltwater would be the real non-starter.
8. Re:How much energy? by couchslug · 2012-02-11 04:38 · Score: 4, Informative
  
  As with " battery hens", few readers will know what "battery" means in that context.
  Cannon artillery analogies are as obsolete as ballista analogies.
  
  --
  "This post is an artistic work of fiction and falsehood. Only a fool would take anything posted here as fact."
9. Re:How much energy? by TheLink · 2012-02-11 04:41 · Score: 2
  
  RO water is much purer though. However efficient it gets I doubt this method will remove the other crap from the water, including crap...
  
  Isn't this similar to electrodeionization?
  --
  
  Too many replies beneath your current threshold
10. Re:How much energy? by mosb1000 · 2012-02-11 05:16 · Score: 2
  
  Isn't this similar to electrode ionization?
  Yes, though the closest analogue is probably electrodialysis reversal. The difference is that no existing technology has been able to economically remove salt in concentrations as high as seawater (though they have been used for brackish water).
11. Re:How much energy? by waimate · 2012-02-11 05:30 · Score: 2, Informative
  
  Very pure water is bad for you, as it leeches good minerals out of your cells (reverse reverse osmosis, if I'm not mistaken aka osmosis). If your desalination does too good a job, you have to "cut" that water with impure water.
12. Re:How much energy? by VolciMaster · 2012-02-11 05:56 · Score: 1
  
  Of course, it only works in parts of the world that get a lot of sunshine, so for example it would be a non-starter in northern Ohio.
  I think the fact that Ohio is not near any source of saltwater would be the real non-starter.
  Love how you excised the OP's context-clarifying statement that said, "Not that we need desalination in Ohio"
  Still pretty darn funny, though
  
  --
  antipaucity
13. Re:How much energy? by gadget+junkie · 2012-02-11 06:05 · Score: 1
  
  Interesting, but how much energy does it take to run this thing? (they call it a 'battery', but I don't think it actually generates electricity). Many of the places that are short on fresh water are also short on electricity (especially "green" energy), so this may not be as helpful as it sounds.
  True, but there are many countries that would be all agog if it would work more efficiently than reverse osmosis, places where salt water is abundant but drinking water is scarce, and energy is (relatively) abundant; think Persian Gulf states, north africa coastal states etc.
  
  --
  "If a boss demands loyalty, give him integrity. But if he demands integrity, give him loyalty." (John Boyd, 1927-1997)
14. Re:How much energy? by MagusSlurpy · 2012-02-11 06:11 · Score: 4, Informative
  
  Actually, the authors call it a battery in their paper. And it is.
  Here's the salient part of the paper:
  
  In this work, we demonstrate a novel electrochemical cell named a “mixing entropy battery”, which extracts energy from the difference in concentration of two solutions and stores it as chemical energy inside the electrode material’s bulk crystal structure. This approach allows us to overcome the challenges of supercapacitor electrodes based on activated carbon. This device consists of a reversible electrochemical system where the salts in the electrolyte are the reactants and the electrode stores ions. We employed two different electrodes: an anionic electrode, which interacts with Cl ions selectively; and a cationic electrode, which interacts with Na+ ions selectively. These electrodes are initially submerged in a low ionic strength solution (river water) in their discharged states, when the electrode materials contain the respective ions incorporated in their structures. In this dilute solution, the battery is charged by removing the Na+ and Cl ions from the respective electrodes (Figure 1a, step 1). Successively, the dilute electrolyte is exchanged for a concentrated solution (seawater), which is accompanied by an increase in the potential difference between the electrodes (Figure 1a, step 2). At this higher potential difference, the battery is discharged, as the anions and cations are reincorporated into their respective electrodes (Figure 1a, step 3). The concentrated solution is then removed and substituted by the dilute electrolyte (river water), which results in a decrease in potential difference between the electrodes (Figure 1a, step 4). We note that the exchange of solution could also be carried out via a flow process, which could be attractive for large scale energy extraction.
  
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15. Re:How much energy? by TheLink · 2012-02-11 06:33 · Score: 2, Insightful
  
  Any scientific study to back that up? e.g. proof that total amount of "good minerals" excreted in urine per day is more when you drink pure water. AFAIK if I drink RO water, I pee more often, but the pee is clearer in colour and if I'm losing more sodium that's a plus not a minus - since I'm a sedentary person who probably consumes more sodium than the RDA, and I'm not an athlete.
  
  Passing pure water through plumbing is a bad idea since it would dissolve all sorts of bad stuff (some places still have lead pipes so they need "hard water") and then you'd drink it... And drinking pure water without taking enough salts and minerals in your diet would cause problems. But that doesn't prove it's bad for you. That's like saying fruits are bad for you because you're not getting enough calcium from them.
  
  And I've had RO and distilled water that wasn't actually pure - some had the taste of acetone, some had some other weird acrid taste. So if the study is not done correctly with actually pure water you might be poisoning the animal/human with the impurities. The problems might not be the pure water.
  
  You want enough minerals, eat more sardines with bones for calcium and a potato/banana for potassium.
  --
  
  Too many replies beneath your current threshold
16. Re:How much energy? by demonlapin · 2012-02-11 06:38 · Score: 2
  
  No, no, no. No. What comes out of you is a function of your kidneys. Drinking distilled water as your only source of water is absolutely harmless. There are limits, of course, to how much your kidneys can concentrate or dilute your urine, but unless you are trying to kill yourself with water intoxication or have a disease, you'll be fine. You do need a certain electrolyte intake, but it's actually quite small. People who have electrolyte disturbances almost always have them because they have no kidney function, or they're taking drugs that alter kidney function, or they're intentionally taking electrolytes, or they're unable to feed themselves and are dehydrated.
17. Re:How much energy? by Adriax · 2012-02-11 06:46 · Score: 4, Informative
  
  Seriously?
  We already do utilize the water that falls from the sky, you know those river things that run into the ocean and most communities were built around?
  Water is finite, even that magic skywater. Upstream communities cannot take all the water they want, as downstream communities rely on the same water source. Desalinization technologies not only allow coastal communities to grow where there isn't a major river, but also frees up water for greater upstream use.
  
  --
  I don't suffer from insanity, I enjoy every minute of it!
18. Re:How much energy? by tqk · 2012-02-11 06:51 · Score: 2
  
  Actually, the whole understanding the implications and building something based on [it] isn't science, it's engineering. Science investigated phenomena; Engineering makes use of those phenomena.
  Engineering is a superset which includes science. Engineering isn't engineering without the scientific component.
  Is the LHC science or engineering, or both? NASA? :-)
  
  --
  "Tongue tied and twisted, just an Earth bound misfit ..." -- Pink Floyd.
19. Re:How much energy? by Anonymous Coward · 2012-02-11 06:55 · Score: 1
  
  So you believe in the Sam Kenison method of eliminating world hunger:
  http://www.youtube.com/watch?v=vN7ehccspao&feature=related
20. Re:How much energy? by Anonymous Coward · 2012-02-11 07:11 · Score: 5, Informative
  
  A report reviewing some of the research as of 1980: Health Risks from Drinking Demineralised Water.
  
  Low-mineral water markedly: 1.) increased diuresis (almost by 20%, on average), body water volume, and serum sodium concentrations, 2.) decreased serum potassium concentration, and 3.) increased the elimination of sodium, potassium, chloride, calcium and magnesium ions from the body.
21. Re:How much energy? by mcgrew · 2012-02-11 07:12 · Score: 1, Offtopic
  
  Water is finite
  No it isn't. In an infinite universe, nothing is finite. Water on earth is finite, even if there is an enormously huge amount of it. But water isn't used up; there is as much water as there ever was. The trouble is its management, not its quantity.
  
  --
  Free Martian Whores!
22. Re:How much energy? by mcgrew · 2012-02-11 07:21 · Score: 1
  
  That depends on your definition of "generate". Generators don't create energy either, they just convert it from kinetic energy. Batteries (except rechargeable batteries) just convert chemical energy to electricity.
  
  --
  Free Martian Whores!
23. Re:How much energy? by crutchy · 2012-02-11 10:28 · Score: 1
  
  beowulf is a "network" of cumpyewters
24. Re:How much energy? by crutchy · 2012-02-11 10:32 · Score: 1
  
  So I guess everyone is stupid for paying ridiculous water bills since we could just collect water from the sky.
  You sound like you been smoking too much fucking dope.
25. Re:How much energy? by FunkDup · 2012-02-11 11:08 · Score: 2
  
  the dude said generate electricity, not energy
  
  --
  Great spirits have always encountered violent opposition from mediocre minds -- Albert Einstein
26. Re:How much energy? by Anonymous Coward · 2012-02-11 11:13 · Score: 1
  
  Batteries don't generate energy.
  Well, thermodynamics preaches that nothing generates energy.
27. Re:How much energy? by docilespelunker · 2012-02-11 12:24 · Score: 1
  
  You clearly don't live in Wales. We have neither sun nore drout...
28. Re:How much energy? by Anonymous Coward · 2012-02-11 13:29 · Score: 2, Funny
  
  Sounds like a prima facie case of A Salt and Battery...
29. Re:How much energy? by TooMuchToDo · 2012-02-11 14:10 · Score: 1
  
  The theory is the science; applying it is the engineering.
30. Re:How much energy? by tqk · 2012-02-11 14:43 · Score: 1
  
  The theory is the science; applying it is the engineering.
  I think we're getting pretty close to splitting hairs here (or arguing about how many angels can dance on the head of a pin).
  Some of the !@#$ NASA does looks like engineering ("implementation"/engineering), but they're really just making it up as they're doing it ("inventing"/science). Ditto, LHC.
  It's a fine line, is all I'm saying.
  I'm not trying to diss either engineers or scientists, btw. I love 'em both for what they bring to the table. I'm personally more comfortable around engineers, but I (not so secretly) idolize scientists.
  Mmmm, Samantha Carter, mmmmm, ...
  
  --
  "Tongue tied and twisted, just an Earth bound misfit ..." -- Pink Floyd.
31. Re:How much energy? by blackicye · 2012-02-11 15:45 · Score: 2
  
  Interesting, but how much energy does it take to run this thing?
  From the abstract: "Here, we demonstrate an energy consumption of 0.29 Wh lâ"1 for the removal of 25% salt using this novel desalination battery, which is promising when compared to reverse osmosis ( 0.2 Wh lâ"1), the most efficient technique presently available."
  My first impression was that this is was largely just an academic project / exercise, there are other way more interesting applications for these nanorods. 15 times the energy to remove only 25% of the salt? geez, I guess it works, but not to make potable water in any quantity.
  Reverse osmosis is already deployed at a comparatively low cost, and scales very well, I don't see this or anything else displacing that as a desalination process any time in the near (or even somewhat further) future.
32. Re:How much energy? by Malvineous · 2012-02-12 01:06 · Score: 1
  
  Graeme: "Are all your hens battery hens?"
  Uncle Tom: "No. Some of them run off the mains."
  -- The Goodies
33. Re:How much energy? by Maxo-Texas · 2012-02-12 04:20 · Score: 1
  
  Sweet Irony... a +5 post followed by a Troll post. Now it just needs to be down-modded to -1.
  And it wasn't a troll or flame bait. Redundant would be a better mod.
  I think Slashdot needs more mods tho.
  More +1's and more -1's.
  
  --
  She was like chocolate when she drank... semi-sweet at first and then increasingly bitter.
34. Re:How much energy? by CapOblivious2010 · 2012-02-12 04:43 · Score: 1
  
  You're just jealous because you didn't get the first post.
35. Re:How much energy? by crutchy · 2012-02-12 08:32 · Score: 1
  
  if it were really that easy, everyone would do it. its like everything on those diy shows, they say things like "simply just", but in many cases people simply just aren't handy at that sort of thing. everyone has something they are good at, and its not always home diy. you are technically correct (i know of ways i could extract water from my own urine), but in cities it isn't always practical (and in some cases it isn't permitted).
36. Re:How much energy? by Anonymous Coward · 2012-02-12 13:29 · Score: 1
  
  Batteries do not generate electricity. They simply STORE electricity and make it available for use. Batteries need to be recharged by other devices which do generate electricity.
37. Re:How much energy? by jonadab · 2012-02-13 02:42 · Score: 1
  
  > I think the fact that Ohio is not near any source of saltwater would be the real non-starter.
  
  Granted.
  
  --
  Cut that out, or I will ship you to Norilsk in a box.
Almost there! by cashman73 · 2012-02-11 03:04 · Score: 5, Informative

The desalinated water that comes from the battery still contains too much salt for drinking, La Mantia says: “We removed up to 50% of the original salt, but we need to arrive at 98%.”
Not sure what math they're using when 50% removal of ions is considered "de-salinated". I guess they're getting there, so by publishing this article, maybe they'll be able to snag some venture capital?
1. Re:Almost there! by captain_sweatpants · 2012-02-11 03:10 · Score: 2
  
  Indeed. The 'Saltwater to drinking water" headline is a bit misleading, but saltwater to partially desalinated water just doesn't have quite the same ring to it...
2. Re:Almost there! by Ihmhi · 2012-02-11 04:01 · Score: 1
  
  Couldn't they run it through a few times to get it desalinated further? Or is it like how some fish will always be small enough to slip through a net?
  
  --
  Random Thoughts From A Diseased Mind (Not For Dummies)
3. Re:Almost there! by timeOday · 2012-02-11 08:15 · Score: 3, Informative
  
  I doesn't put a 50% limit:
  
  "We removed up to 50% of the original salt, but we need to arrive at 98%."
  Doing several cycles of ion removal with the battery would further desalinate the water, but those extra cycles cost energy, so La Mantia hopes to improve the efficiency enough so that the battery can remove the salt in a single pass.
  
  If they're really the first to implement a new chemical process here, then the GP implying this is not significant in itself and they just published it so they could get venture capital is pretty sad. There used to be this thing called "research." Most of it went nowhere, yet it created the world we live in.
4. Re:Almost there! by eugene+ts+wong · 2012-02-11 13:20 · Score: 1
  
  I think that they can start using it now. According to Wikipedia, we might be able to drink 2 cups of sea water per day, when mixed with a cup of fresh water. So, if we take 2 cups of the "almost there" water, and then add a cup of fresh water, we can get something fairly useable. No?
  
  --
  testing out my trending skills
Hee'uk by sgt+scrub · 2012-02-11 03:07 · Score: 1

Maganese oxide? I thought Maganese was used for Galvanizing metal. Doesn't that mean it doesn't "oxidate"? :P

--
Having to work for a living is the root of all evil.
1. Re:Hee'uk by tqk · 2012-02-11 03:46 · Score: 2
  
  Maganese oxide? I thought [Manganese] was used for Galvanizing metal.
  Don't you mean zinc?
  
  --
  "Tongue tied and twisted, just an Earth bound misfit ..." -- Pink Floyd.
2. Re:Hee'uk by jo_ham · 2012-02-11 14:23 · Score: 1
  
  Manganese is a transition metal, and it certainly oxidises very readily - down to +7 in fact. I'm sure most people who have done high school chemistry remember the dark purple KMnO4 solution.
  Zinc is also a transition metal, and is what is used in the galvanising process.
3. Re:Hee'uk by sgt+scrub · 2012-02-12 01:41 · Score: 1
  
  Yeah. One of Maganese's uses is to control rust in steel. I used Galvanizing as a generalized term. I should have know better on /.
  
  --
  Having to work for a living is the root of all evil.
4. Re:Hee'uk by tqk · 2012-02-12 03:47 · Score: 1
  
  Maganese oxide? I thought [Manganese] was used for Galvanizing metal.
  Don't you mean zinc?
  Yeah. One of [Manganese's] uses is to control rust in steel. I used Galvanizing as a generalized term. I should have [known] better on /.
  It averages out. I didn't know that about manganese. Now we're both richer. :-)
  Some of us (well, I am anyway) are a veritable bottomless pit full of useless information. Put me in a room with iron ore, coal, and zinc, and I doubt I'd be coming out with any galvanized steel any time soon.
  
  --
  "Tongue tied and twisted, just an Earth bound misfit ..." -- Pink Floyd.
a total bust, not energy efficient at all by rubycodez · 2012-02-11 03:10 · Score: 2

requires electricity, unlike thermal desalination which can use free (as in beer) energy, and doesn't produce anything useable. was this summary written to attrack potential investors? it most likely will be a waste of time and money....
1. Re:a total bust, not energy efficient at all by rubycodez · 2012-02-11 03:32 · Score: 3
  
  solar ones at municipal scale are being built now in australia, india, spain.
2. Re:a total bust, not energy efficient at all by Oligonicella · 2012-02-11 03:33 · Score: 1
  
  Show me a sodium battery that produces drinkable water, thereby making it *useful* on a lifeboat.
3. Re:a total bust, not energy efficient at all by jackbird · 2012-02-11 04:41 · Score: 1
  
  I can show you a reverse osmosis rig with a solar-powered pump and a manually-operated backup mode....
4. Re:a total bust, not energy efficient at all by TheRaven64 · 2012-02-11 05:05 · Score: 5, Informative
  
  I remember in the '90s the Innovations catalogue sold inflatable thermal desalination rafts. You inflated them and they floated on the sea concentrating sunlight on the surface like a greenhouse. The water evaporated and then condensed on the inside of the glass and trickled out into the edges. They produced about 2 pints of water per day and were intended to be kept on life rafts (they couldn't operate on them, but they could float beside them and work, as long as there was sunshine). I presume they haven't stopped existing in the last 15 years...
  
  --
  I am TheRaven on Soylent News
5. Re:a total bust, not energy efficient at all by ras · 2012-02-11 11:52 · Score: 4, Informative
  
  http://www.landfallnavigation.com/memss.html
Battery? by Hentes · 2012-02-11 03:11 · Score: 2

Isn't this called electrolysis?
1. Re:Battery? by Anonymous Coward · 2012-02-11 03:40 · Score: 1
  
  Isn't this called electrolysis?
  Most electrolysis cells deposit the metal on the elctrode; you can't do that with sodium, because it reacts with the water. The trick here seems to be that the sodium gets absorbed into the electrode, and so is actually removed from the water. Neat, but no coconut - yet.
Hmm by RenHoek · 2012-02-11 03:13 · Score: 5, Informative

Of course, (good) reverse osmosis cleans out a LOT more out of the water then just salt, e.g. bacteria, viruses.
1. Re:Hmm by perl6geek · 2012-02-11 03:52 · Score: 2
  
  I'm pretty sure there is room for both techniques. For irrigation you don't need the same quality as for drinking.
2. Re:Hmm by Anonymous Coward · 2012-02-11 03:58 · Score: 1
  
  For things like those, it's easy to go through a filtration system. Salt on the other hand tends to clog up filters relatively fast making filtration on a mass scale difficult (as in costly which is why you don't see much desalination plants for water).
3. Re:Hmm by Colonel+Korn · 2012-02-11 04:39 · Score: 4, Informative
  
  Of course, (good) reverse osmosis cleans out a LOT more out of the water then just salt, e.g. bacteria, viruses.
  Do you have a sense of how dramatically expensive RO is and how much cheaper it would be if 50% of the salt in seawater could be removed in a relatively low cost preliminary separation? Somehow most of the comments on this story, both positive and negative, seem to assume its main use needs to be as a desalinization gadget where you put the saltwater in one side and delicious drinking water comes out the other. That would be amusing but not particularly useful or realistic. The value of a separation technique is going to come in the form of energy and labor savings. If I talked about this tech at work I'd hear comments like, "imagine the RO fouling reduction!"
  
  --
  "I zero-index my hamsters" - Willtor (147206)
4. Re:Hmm by Anonymous Coward · 2012-02-11 06:47 · Score: 2, Funny
  
  It's electrolytes!! That's what plants crave!
5. Re:Hmm by MattskEE · 2012-02-11 06:57 · Score: 3, Interesting
  
  You might be right that the place for this tech is a pre-treatment for an RO process, but it isn't mentioned in the article and the researchers appear to be looking for a gadget "where you put saltwater in one side and delicious drinking water comes out the other":
  
  The desalinated water that comes from the battery still contains too much salt for drinking, La Mantia says: “We removed up to 50% of the original salt, but we need to arrive at 98%.”
  Doing several cycles of ion removal with the battery would further desalinate the water, but those extra cycles cost energy, so La Mantia hopes to improve the efficiency enough so that the battery can remove the salt in a single pass.
  I'd be dubious about the efficiency of doing this electrochemical desalinization to remove so much of the salt, I would think that the resistance of the water is going to rise substantially as salt leaves so it seems like more and more electrical energy will be required per mole of salt ions as the concentration drops.
  So by pre-treating water to remove much of the salt before sending it to RO the membranes will last longer before replacement? How much of the operating cost of an RO plant is determined by this? Would there be an impact on the RO process energy consumption?
6. Re:Hmm by idji · 2012-02-11 08:30 · Score: 1
  
  And don't forget Boron removal.
7. Re:Hmm by catprog · 2012-02-12 12:26 · Score: 1
  
  http://www.membraneshop.com.au/products/BW30%252d2540-Filmtec-2.5%22-x-40%22-Brackish-Water-Membrane.html
  $289.00 15.5 bar GPD-850
  http://www.membraneshop.com.au/products/SW30%252d2540-Filmtec-2.5%22-x-40%22-Sea-Water-Membrane.html
  $390.00 Bar-55 GPD-700
  So about $100,40 bar,150GPD better for Brackish over salt.
  
  --
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Re:P.S. First! (sorry, I couldn't resist!) by TaoPhoenix · 2012-02-11 04:04 · Score: 1, Informative

Please do. Help End the Dumb First Post meme.
(Dr. Emmett Brown) "According to my calculations, the nature of the First Post directly influences the quality of the entire thread. When a really good First Post is made, the quality of the thread increases between 25-75%, because in most neutral (non flame bait) stories, once the "famous first slot" is taken, and then there are some five to seven good replies, trolls don't bother as much with low grade slots down farther in the chain. The improvements to the quality include a 20% drop in "Slashdot sux" comments too.
(/Dr. Emmett Brown)
Say what you like about those awesome back to the future movies, Doc Brown was awesome because his math was almost never wrong.

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My first Journal Entry ever, in 8 years! http://slashdot.org/journal/365947/aphelion-scifi-fantasy-horror-poetry-webzine
Re:Life Rafts by Anonymous Coward · 2012-02-11 04:12 · Score: 2, Informative

I think they already have RO filters with hand pumps that would fit that niche.
Re:Life Rafts by perpenso · 2012-02-11 05:18 · Score: 1

I think they already have RO filters with hand pumps that would fit that niche.
There are also inflatable solar stills. They generate a lot less water but they are passive and you can use a bunch of them at a time.
Re:Ah, I got it ... by Nos9 · 2012-02-11 06:24 · Score: 1

actually we'd probably dump the salt back into the sea, since most of the water that is being added to the system has very low salinity. It would lower sea levels and bring the salinity to a more normal level.
A long way from being useful by Animats · 2012-02-11 06:33 · Score: 2

No, you don't put in salt water and get energy and fresh water out. You put in salt water and energy and get somewhat less salty water out.
As with most desalinization systems, getting rid of the salt and other crud is a big problem. They haven't solved that yet. "Researchers need to find ways to remove sulfates from seawater, lower the cost of the electrodes, and protect the system from deposits of biofilm and scale that could cripple the device." It took a long time (from 1748 to 1965) before reverse osmosis membranes were developed that could handle that problem. Reverse osmosis systems require an occasional freshwater flush, but this takes far less water than the system produces. It's not clear how the numbers work out on this new approach.
Re:P.S. First! (sorry, I couldn't resist!) by mikael · 2012-02-11 08:37 · Score: 1

Maybe the priviledge of the first post should go to the article submitter or someone with meta-moderation status?

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Re:P.S. First! (sorry, I couldn't resist!) by chromas · 2012-02-11 09:55 · Score: 2

Thanks for making me read that entire paragraph in Christopher Lloyd's dramatically hurried voice.
Re:P.S. First! (sorry, I couldn't resist!) by crutchy · 2012-02-11 10:26 · Score: 1

almost = mathematical uncertainty (also a handy disclaimer)
Re:P.S. First! (sorry, I couldn't resist!) by hairyfeet · 2012-02-11 10:49 · Score: 1

Hey who doesn't love ole Doc Brown? BTW just FYI but if you watch the first chase scene between Marty and the Libyans? look closely at the "Marty" driving the car. In several scenes you'll see Marty has RED hair because they had originally cast Eric Stoltz as Marty but he read the character way too dark so when Michael J Fox became available they fired Stoltz and reshot the movie but they didn't have it in the budget to reshoot the chase sequence.
As for TFA isn't calling this thing a battery kinda misleading? When I first read the headline I thought "What a breakthrough, this will help the poor get electricity AND drinking water! This person should get the Nobel Prize!" but reading TFA this thing doesn't really act like a battery at all, what a letdown.

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ACs don't waste your time replying, your posts are never seen by me.
Late arrivals at the desalination party by WaffleMonster · 2012-02-11 14:51 · Score: 3, Informative

Just the other day it was discovered water magically evaporates thru sheets of graphene about as fast as you can pour.
Kind of makes it difficult to see the point of experiments involving basic chemistry with lousy effeciency falling off a cliff as concentration of salt is reduced.
Re:true today. by TaoPhoenix · 2012-02-13 03:58 · Score: 1

It's definitely Non-Random, and positive. That's why I threw a big range at it.
The easy way to look at it: In those second tier stories that only get some 40 comments, a couple of typical Forrest Posts will waste about 10 comments all by themselves.
No less than NYCL himself complained about this problem, in that story updating us on his ReDigi client.

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My first Journal Entry ever, in 8 years! http://slashdot.org/journal/365947/aphelion-scifi-fantasy-horror-poetry-webzine
Why? by hesaigo999ca · 2012-02-13 06:06 · Score: 1

>When the current is reversed, they dump the sodium ions out into waste water.
Why not just keep the salt, and make it into a packaged sea salt so as to use all of the elements and save money by making even more money from the process.