Hi guys,
I wanted to explore the potential of sea water. In Australia and in particular Melbourne [ down south ] we have a chronic problem of reducing fresh water supplies. Our dams are less that 50% full and we have had water restrictions in place for some years. [ drought conditions persist in the state generally] It appears that our shortage of fresh water will eventually become a massive issue as the growth of our cities is directly impinged upon.
I understand that this is not just a local problem, and that globally fresh drinkable water is in high demand.

The question I wanted to raise in a general sort of way is:
Is it possible to utilise our worlds significant salt water researves [ oceans ] in some way to alleviate this problem?

What obstacles are their to the de-salination of sea water?

Obviously if a method could be found to use sea water for crop irrigation etc after treatment that was cost effective, the problem would be more or less solved.
It is also obvious that this is not a new suggestion and their must be significant problems [ mostly cost I would presume] in the use of sea water as we would already be using it if there were not.

Care to discuss. ;)

What obstacles are their to the de-salination of sea water?

Cost ...it's as simple as that! We can build pipelines thousands of miles from glaciers, mountains, etc much, much cheaper than we can build de-salination plants that would provide the same amount of water.

I have a question, though .......what are we to do when we have so many people that we pump the oceans dry, too?

Baron Max

I have a question, though .......what are we to do when we have so many people that we pump the oceans dry, too?

How many people would there have to be, to need approx 1,400,000,000 km3 of water?

How many people would there have to be, to need approx 1,400,000,000 km3 of water?

Are you forgetting irrigation for food crops and for the cattle to drink, too? Not to mention flushing the toilets and bathing?

As to how many people? I don't know, but at some point we'd begin pumpiing the ocean levels down ...it only makes sense, logical sense. We used to say that we had all the water we'd ever need, didn't we? Now look!

Baron Max

well ....most countries have access to salt water but not many have access to glaciers. here in Aussie land we already tap our mountains [ opps sorry...I mean hills...ha]

From what i read there seems to be about three or four popular methods currently being tried or in service.
But I wonder if there is nto a more efficient way to do the job....

The ideal I think would be to develop a method of getting all the salt to lump together, a form of self de-salination....but I don't think we have the tech for that yet.

Baron I think you may be underestimating how big and deep the oceans are? And doesn't water go through a cycle anyway? It doesn't just dissappear down a black hole.

Are you forgetting irrigation for food crops and for the cattle to drink, too? Not to mention flushing the toilets and bathing?

As to how many people? I don't know, but at some point we'd begin pumpiing the ocean levels down ...it only makes sense, logical sense. We used to say that we had all the water we'd ever need, didn't we? Now look!

Baron Max

well, but the water doesnt dissapear to the toilet, most of the sewage goes back to oceans, we just need more energy to reclean it.

*damn, I missed Nickelodeon´s post, anyhow...

...The ideal I think would be to develop a method of getting all the salt to lump together, a form of self de-salination....but I don't think we have the tech for that yet.Forget that, as that would be a move from great disorder to extreme order. (Entrophy reduction always requires input of energy.) - it costs much less energy to convert 3% salinity to 3.1% in large volume of ocean water by removing some fresh water. The three ways* to do this are all in use as about the same cost.
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*(freeze, boil, and reverse osmosis)

How many people would there have to be, to need approx 1,400,000,000 km3 of water?Many, but still not nearly enough to drain the oceans as bladders can only hold a couple of liters. :D

Many, but still not nearly enough to drain the oceans as bladders can only hold a couple of liters. :D
But then you'd have to purify more than salt out of the oceans :D

well, but the water doesnt dissapear to the toilet, most of the sewage goes back to oceans, we just need more energy to reclean it.

Isn't that similar to what people in the past thought and said about the Earth's fresh water supplies???? ....and now all of the rivers and lakes are so polluted that we can't drink from it without expensive purification equipment and pipelines.

"Oh, hell, that's crazy, Maude, there'll always be enough water in the river for us to drink ....don't worry, Maude, everything's gonna' be just fine!"
Baron Max

I drink from a muddy ditch, and i am fine.

I read of one method of desalinization (it was in an old New Scientist article) where sea water was pumped into a desert area and dripped down fabric.

Either a breeze or fans would then blow through the fabric while the sun evaporated the sea water and the mist was used to water crops.

It worked so well that the guy who designed the system could grow carrots, broccoli, spinach and other crops that needed high amounts of water in the Saudi Desert.

I drink from a muddy ditch, and i am fine.

And how long will the water in the muddy ditch remain?

Baron Max

As long as I piss in the ditch, who knows?

As someone already pointed out, the water cycle takes care of us running "out" of water. It simply won't happen, not without a technological level FAR beyond anything we have now. Notice I'm not saying its impossible, just impossible using current technologies. However, what we DO run out of us fresh water. Natural processes take care of filtering and cleaning water for us, but natural processes don't care where we want to live or at what rate we want to use the fresh water. The easy solution is to do these processes ourselves. This however takes an input of energy (just as the natrual processes did, usually from the sun either directly or indirectly). Unfortunately, we are not at a point where energy is cheap enough to warrant this in all cases. Hopefully we'll devise more energy efficient ways and better ways of producing energy.

Unfortunately, it seems that all problems come down to energy. Its the ultimate currency.

-AntonK

"if we make the salt heavier than water wouldn't it sink to the bottom leaving fresh water on top"
just add chemical "X" and stir.....

just dreaming......ha

As someone already pointed out, the water cycle takes care of us running "out" of water. It simply won't happen, not without a technological level FAR beyond anything we have now. Notice I'm not saying its impossible, just impossible using current technologies. However, what we DO run out of us fresh water. Natural processes take care of filtering and cleaning water for us, but natural processes don't care where we want to live or at what rate we want to use the fresh water. The easy solution is to do these processes ourselves. This however takes an input of energy (just as the natrual processes did, usually from the sun either directly or indirectly). Unfortunately, we are not at a point where energy is cheap enough to warrant this in all cases. Hopefully we'll devise more energy efficient ways and better ways of producing energy.

While we don't necessarily lose water, we lose it in places where we need it and have grown accustomed to having it. The danger of a changing environment isn't the change per se, it's the fact that we then have infrastructure and people in the wrong places.

What happens when California runs out of water? Millions of refugees? The world's fifth largest economy collapsing?

"if we make the salt heavier than water wouldn't it sink to the bottom leaving fresh water on top"
just add chemical "X" and stir.....

just dreaming......ha

That's a pretty good idea.
What about some sort of plant or fungus that did it? Put it to the water, add some light and nutrients, and it'd pull all the salt out.

The percolation system of irrigation in arid climates was a pretty cool design. I wish I could find that article on the net.

"if we make the salt heavier than water wouldn't it sink to the bottom leaving fresh water on top"
just add chemical "X" and stir.....

just dreaming......ha

The problem is, salt water doesn't contain salt. It contains sodium and chlorine ions. Its not until you evaporate the water that it reforms into NaCl (salt).

-AntonK

The problem is, salt water doesn't contain salt. It contains sodium and chlorine ions. Its not until you evaporate the water that it reforms into NaCl (salt).

-AntonK

ahhh!! and important distinction...thanks for that...I simply thought like a lot of other people would that salt water was just water with tiny crystalised salt in suspension.

so really we are not talking about water are we.....if you want to be pedantic.The sea or oceans do not have water as such but something very different.....just trying to get the right perspective on it.....please excuse me.

edit:

Silly post..... sorry......

Affordable fresh-water for Hotels etc.
Desalination of sea-water for less than 1 $ per m3.

http://us.st11.yimg.com/us.st.yimg.com/I/hohcanarias_1912_347004
Source: http://www.hohcanarias.net/

"FILMTEC Membranes Continue to Lower the Cost of Seawater Desalination

"If we could ever competitively, at a cheap rate, get fresh water from saltwater,…(this) would be in the long range interests of humanity which could really dwarf any other scientific accomplishments." John F. Kennedy, September 22, 1961

FilmTec is helping enable this vision with new products, technology and strategies for lowering the cost of desalinated water. Today FilmTec makes available the new FILMTEC™ SW30XLE-400i element, a reverse osmosis (RO) element with the lowest energy requirement in the industry to deliver the lowest total cost of water across a wide range of seawater desalination applications. In addition, our new FILMTEC SW30HR LE-400i element can reduce your desalination costs by as much as 20%, depending on whether you are seeking lower pressure, higher productivity or a system with fewer elements. See: http://www.dow.com/liquidseps/prod/sw.htm

The problem is, salt water doesn't contain salt. It contains sodium and chlorine ions. Its not until you evaporate the water that it reforms into NaCl (salt).

-AntonK

I totally forgot that particles disassociate in water.

Do filters work at all for desalinization?

[edit]
ah, it seems FILMTEC is doing it.

Thats not the only company, one of the Local water companies in the UK created a similar "Mobile" desalination unit with the intension of using them in places that have droughts or floods.

There are also Mobile Sewerage treatment units that you'll find on Ocean Liners, Ferries and of course Military vessels that can apparently take raw sewerage and convert it to clear drinking water, although most people tend to pass up the offer of drinking it when they know where the water came from.

...What about some sort of plant or fungus that did it? Put it to the water, add some light and nutrients, and it'd pull all the salt out....Because sea's salt is mainly ionic Na+ and Cl- in H20 (which is also partly split into ions H+ and OH-) the idea of making crystal "heavy" to sink to the bottom is nonsense, but not far from a possible approach to get fresh water from the sea at lower cost.

Already several ocean birds dirnk sea water almost exclusively* as they have gland that can farther concentrate the salt, giving them fresher water for general use (blood etc). There is no reason why (almost sure) genetic engineered simple organisms could not do the same. I.e. concentrate Na+ and Cl- above the sea level in their bodies. They could be raised in shallow ponds, and use sunlight for energy, perhaps getting most of what they need from water and air as green algae does. Filtering them out would at the very least leave the water less salty, perhaps directly useful in agriculture (with salt tolerant genetic engineered plants, of course.)

Summary - while in original form wrong, idea is worth serious consideration, not crazy.
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*Fish too have been known to live in the sea, drinking only sea water. ;)
PS - If I were to try I think I would give "brine shrimp" a serious looking over as they can live in salt water several time more salty than the sea (like Utah's great salt lake) but I do not know if they concentrate salt relative to their surounding water. Probably a good source of food also when harvested.

To make a "triple threat" one could look at negative locations (There is a hugh one in North Africa nearly, as I recall, 100 meters below sea level) that can be flooded with relatively near by sea water and generate great amounts of electic power, (For more than 1000 years in the case of the big negative depression of N. Africa as sun of that now desert evaporates the water, perhaps forever functioning.) The increased rain fall in other near-by parts of the desert would be welcome and also is more completely fresh water.

To make a "triple threat" one could look at negative locations (There is a hugh one in North Africa nearly, as I recall, 100 meters below sea level) that can be flooded with relatively near by sea water and generate great amounts of electic power, (For more than 1000 years in the case of the big negative depression of N. Africa as sun of that now desert evaporates the water, perhaps forever functioning.) The increased rain fall in other near-by parts of the desert would be welcome and also is more completely fresh water.

There was an attempt in the 19th century to flood the Sahara.

Filtering them out would at the very least leave the water less salty, perhaps directly useful in agriculture (with salt tolerant genetic engineered plants, of course.)

I'm told that in California, constantly growing crops in the same area is leeching salt out of the earth and leaving the fields barren. The same thing happened in Sumer, which became the desert wastes of Iraq.

Pumping brackish water into agricultural areas me be rather dangerous. It would probably be safer to genetically engineer a mangrove to produce food.

Have you reference to old attemp to make salt lake in Sahara? I read many years ago proposal for electric generation on scale of water influx = evaporation for infinite life.

You are 100% correct about the need to have some fluid leave agricultural land to prevent salt build up, but note it can leave downward in some cases. Irrigation in a desert is a big long-term problem. - Possibly some of the lowest levels should be reserved for conversion into "salt flats" - collectors for the relative fresher water that "washes" the accumulating salt from the agricultural land. Perhaps only rain in near by lands is used for agriculture. - I am not very knowledgeable in this but, like you, recognize it is a big, but I think soluble, problem to get some agricultural yield.

With fish drinking sea water (salt water vs. fresh water fish) you're getting into their differences in osmotic metabolic functions and internal osmotic pressure differences in how they maintain equilibrium. It's a different metabolic function than humans have. I could go into that if anyone wants?

Since Na+ and Cl- are ions, you should be able to filter the ions out with opposite electric poles. I also remember seeing a movie where two guys were stranded in the Sahara Desert and filtered water out by creating a basin underneath a cloth filter that slowing dripped purified H20 out. Don't know if sometype of apparatus like that would work on saltwater or not?

I buy a lot of camping supplies from Campmor (www.campmor.com) and I see that they have a water purifier called "MSR MIOX Water Purifier" that runs on batteries and salt to operate, but it doesn't say if it filters out salt: "the Miox Purifier works by creating brine out of untreated freshwater and salt, passing a small electric charge through the solutuon, which results in a powerful dose of mixed oxidants. This "cocktail" is poured into untreated water leaving you with safe pure purified water."

Food for thought - or water?

With fish drinking sea water (salt water vs. fresh water fish) you're getting into their differences in osmotic metabolic functions and internal osmotic pressure differences in how they maintain equilibrium. It's a different metabolic function than humans have. ...I fully agree. My point was not that humans have the same "osmotic metabolic functions" as fish (or sea birds) but that it is obviously possible for living organisms to lower the salinity of sea water. I am confident (based on great ignorance of the field) that genetic engineering can make micro-organisms (probably single celled ones) that process sunlight for energy and when harvested (and crushed) yield less salty water (which may be directly suitable for most agriculture needs, especially if the plants too have had some genetic engineering to make them more salt tolerant.) and food (or at least fetilizer for these plants, which then yield food and fiber to man.)

Yeah, that's an interesting topic. What we have to look into is "halophile" microrganisms that live in the Dead Sea and the Great Salt Lake to see what their metabolic processes end up with. I'll get back on this.