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Inland Desalination

more biomass and water for Australia
  (+9, -1)(+9, -1)
(+9, -1)
  [vote for,
against]

The map of outback Australia shows a lot of seasonal salt lakes. In winter, they're dead seas. In summer, as I understand it, they're the crystaline skeletons of dead seas.

I propose to pick one of these and, in winter, when it's full, to line its bed with a membrane (which need not be water-tight, so it could be deployed in overlapping pieces.)

Come the summer, instead of the salt being deposited on the lake bed, it would be deposited on the membrane.

Remove the membrane, salt and all. At a great distance from the lake, either scrape or rinse the salts off the membrane, then, next winter, replace the membrane in the lake bed. Repeat ad nauseam.

Over time, the salinity of the lake will gradually fall, as all the readily soluble chemicals in the surrounding catchment area are hauled away.

Eventually, instead of being too hot and poisonous for habitation, the vicinity will be merely too hot for habitation. Cacti can be planted, and maybe even a few scraggy date palms. The cacti will jealously cling on to at least some of that winter rain right through the summer, rain which would otherwise have evaporated into the high atmosphere and would probably not have fallen as rain again until after it had left the continent. You might get a few aestivating bugs and lizards - anyway, some living things rather than none.

Initially, at least, you'd want to select a lake close to a watershed, so as to minimise the size of the upstream catchment area to be cleared of salts.

I'm not sure what would be the best thing to do with the extracted salty membranes. I picture them being dragged away on un-manned solar-powered tracked vehicles which rest by night and creep across the desert by day.

It might or might not be worthwhile at the margin to scrape off the salts for sale (though I don't imagine this would cover the overall cost of the project). The obvious alternative would be to drag them all the way to the coast and rinse the membranes in the ocean. Don't worry, it wouldn't be man-made contamination, just natural contamination, transferred from one place (where it's at high concentration) to another place (where it will be at lower concentration).

pertinax, Jul 11 2007

The Australian sea The_20Australian_20sea
a not unrelated idea [hippo, Jul 11 2007]

the price of salt http://minerals.usg...ity/salt/580302.pdf
[pertinax, Jul 12 2007]

MIT report on Hollands floating water solution http://www.technolo...Energy/18890/page6/
[IceFest, Jul 13 2007]

Organisms in space. http://space.newsci...rticle.ns?id=dn8297
[2 fries shy of a happy meal, Jul 14 2007]

[link]






       Australia is doing pretty well as a country. Why meddle?
miasere, Jul 11 2007
  

       Worsening drought? Growing population? Australia is doing well economically, but ecologically it's in trouble.   

       //Why meddle?// Call yourself a half-baker? ;)
pertinax, Jul 11 2007
  

       point taken   

       <meddles>
miasere, Jul 11 2007
  

       Great idea [+] and possibly viable from a commercial, rather than a purely environmental point of view - as an alternative means of mineral extraction.
zen_tom, Jul 11 2007
  

       You must reserve the salt and sell it on the world market. You just need a really twee name for it. Kangaroo Sprinkles, or Koala Crystals, or something. You need a someone to sell it. Do you have any celebrities who haven't been killed by wildlife yet?
Galbinus_Caeli, Jul 11 2007
  

       There's always [Unabubba]. <doffs cork-dangly bush-hat in respect>
pertinax, Jul 11 2007
  

       I wonder what proportion of the salts in these lakes actually goes into solution? Mono lake has pillars of the stuff extending up out of the water. There are dead lakes in California that have been mined for salts and borax for decades, but are not any more alive.
bungston, Jul 11 2007
  

       Why the membrane? Why not just collect the salt with a bulldozer when the lake is dry?
Texticle, Jul 11 2007
  

       [Bungston], is there any evidence that those Californian lakes have run out of salt and borax yet? And are they refilled with salt and borax from a large catchment area? And what proportion of the water's mineral load (when full and saturated) is extracted each year?   

       [Texticle], the membrane gives you a lot of salt in one hit. You can then just lift it off the bottom, not scrape it off. I don't know whether it would really be more energy-efficient, but it seemed neater that way.
pertinax, Jul 12 2007
  

       Because when you are moving hundreds of tons of raw mineral salts neatness is of the highest importance.
miasere, Jul 12 2007
  

       Exactly, [miasere], I'm glad you see it that way. ;)   

       Also, with the membrane method, you only need people on site for about two days in each year and, with sites as remote and inhospitable as the ones I have in mind, and with labour expensive and in short supply, that's important too. Not as important as neatness though, obviously.   

       [bungston], here are some numbers from the back of the trusty envelope:
Imagine a shallow lake, 100m by 100m by 1m deep, holding 10 000 cu. metres of water.
A quick Google tells me that, at boiling point, water can hold 35.7g of salt per 100ml. Let's say that our sun-baked lake holds little more than half of that concentration; that would still amount to a couple of thousand tonnes of salt.
Another quick Google tells me that the density of sodium chloride is 2.16 g/cu. cm. So, when the lake dries up, giving us 2000 tonnes of salt, that would cover the lake bed (or our membrane) with 200kg of salt per square metre, which would represent a layer about 10cm deep (unless I've misplaced a few decimal points along the way).
So, if the lake bed is currently five metres deep in salt then, neglecting replenishment of the salt by run-off from the salty catchment area, it would take a mere twenty-five years <correction: fifty years/> for the lake to be substantially desalinated. (It still wouldn't be pure, sweet water, but maybe pure enough for a few tough old Australian desert plants to gain a foothold).
  

       The linked US government commodity report seems to suggest a commodity price for salt of around 1USD per 50 grams, which seems a bit on the high side to me, but that would mean a total gross revenue of a billion USD over the life of the project. No, that can't be right, can it? There must be something wrong with this envelope.
pertinax, Jul 12 2007
  

       Sainsburys, UK, 1.5 kilos cooking salt, 49 uk pence (== about 1 us dollar). And that is at retail.
Perhaps I should start a salt export business...
Loris, Jul 12 2007
  

       Wait - I just read the note in the linked document which says 'data in thousands of metric tonnes...' I was reading it as tonnes. So, adjusting by a factor of 1000, that means 1million USD gross revenue over 25 years <correction: 50 years/>. It's still more than I would have guessed, but perhaps not entirely incredible.
pertinax, Jul 12 2007
  

       WHAT DO U THINK THIS WILL DO?? All our pelicans come here to feed when it does flood (only about every 10 years anyway) and we have fish adapted to living here and frogs Why should we kill them to get water. If we need water and grazing land then we should copy the dutch and build floating glasshouses and desalination plants   

       Robert
IceFest, Jul 12 2007
  

       // build floating glasshouses and desalination plants   

       LINKY!
TheLightsAreOnBut, Jul 12 2007
  

       OK, [IceFest], there are some interesting points there.   

       First, I'm wondering where you're talking about, and whether the points you make apply to all the seasonal salt lakes, or just to one near you.   

       I admit I haven't been to these lakes, just seen lots of them on maps, but I was under the impression that, situated deep in desert areas, they did not support any existing ecosystem. If they do, then this idea is probably not defensible.   

       New facts are welcome. There's no need to SHOUT.
pertinax, Jul 12 2007
  

       Ok that was my first post ever! so sorry for the shouting.   

       Here is the link: for the floating city: (couldnt post it) but you need to make a free logon to view it.   

       Am talking about the lakes in general as I have been to a few of then. Anyway every 7 years or so when they flood all lind of bird come to eat the fish that do breed there.   

       with that reference to near me In Australia a few hundred km isn't really that much. eg im going on work experience 500 km away to the next big city. But it looks close!   

       Anyways the dutch have the idea!! ....mabey that should be a halfbakery topic??
IceFest, Jul 13 2007
  

       Thank you for that clarification, [IceFest]. I will now vote against the idea, but will leave it in existence on the grounds that it's still interesting. [-]
pertinax, Jul 13 2007
  

       There is basically no where within a kilometer of the surface of the earth that does not have a thriving ecosystem. There are bacteria that live in clouds, blind fish in caves, scorpions in deserts, jellyfish in the oceans, mites in the cracks in glaciers.
Galbinus_Caeli, Jul 13 2007
  

       funny Organisms everywhere only not in space.   

       so the though should be: where can we kill the least organisms. well how about we do this to the aral sea?? big, empty, and should be full??
IceFest, Jul 13 2007
  

       Least by Mass? Count? Diversity? Rarity?   

       Bah, we should just leave earth to the bugs and move into space.
Galbinus_Caeli, Jul 13 2007
  

       //funny Organisms everywhere only not in space. //   

       I'm not lichen that statement. [link]   

       // Australia is doing pretty well as a country. //   

       Actually, a large proportion of Australian agriculture is in deep doo - which means that Australia is in imminent danger of being in deep doo altogether.   

       Whether this particular proposal would help in any significant way I rather doubt.
Cosh i Pi, Jul 14 2007
  

       //Whether this particular proposal would help in any significant way I rather doubt.//   

       Hmm... no; it's too long for a tagline. Pity.   

       //Australia is in imminent danger // Don't worry, we have a strong mining sector like, errm, the Congo. Oh, wait...
pertinax, Jul 15 2007
  

       Perhaps you could transfer the salt from all the the lakes into just 1 lake, so you have a "Heaping Lakeful of Lake Salt" in the summer and a "Salt Lake Island of Salt" in the winter.
quantum_flux, Nov 18 2007
  

       Quick research on the Great Salt lake in Utah (US) suggests that it has no unique animal life, and the waterfowl that inhabit it would be perfectly happy on a freshwater lake. I don't know if this applies to the Australian lakes as well, but if so, this may not be a particularly ecologically harmful approach.   

       One comment on the economic viability however, the salt that comes out of these lakes may or may not be suitable for such things as table use. Sea salt has a relatively low instance of toxic salts, some of these lakes, especially ones that are recieving industrial run-off or contaminated rainfall might have a much higher percentage (sodium cyanide, anyone?).
MechE, Nov 19 2007
  

       Why not stretch out that monstrous membrane and leave it there as a liner? Salt on the bottom, fresh on the top. Pump out the fresh water, or siphon it into subsurface tanks, to be used for ones favorite application.   

       Australia is close to Antarctica, and both begin with A. Since Antarctica is shedding its glaciers anyway, couldnt the aussies approrpiate a few?
bungston, Nov 19 2007
  

       <dragging extra-large tongs>Standing by to approrpiate, sir!</delt>
pertinax, Nov 21 2007
  

       Howard you propose to finance this, John?
4whom, Nov 21 2007
  

       The salt would be used as a preservative in all those barrels of pork.
pertinax, Nov 21 2007
  
      
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