Why is it difficult to turn seawater into drinking water?

Discussion in 'General Science & Technology' started by Saint, May 31, 2012.

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  1. Neverfly Banned Banned

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  3. KilljoyKlown Whatever Valued Senior Member

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  5. Neverfly Banned Banned

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    That's what we've been sayin' goofy!
     
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  7. KilljoyKlown Whatever Valued Senior Member

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    Okay, but I didn't get it that way. Felt more like pulling teeth.

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  8. Neverfly Banned Banned

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    Irrelevant. I will not allow my lack of clarity to stop me from casting judgment on you.
    I have termed you as 'goofy' and goofy you shall stay.

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  9. Fraggle Rocker Staff Member

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    What you're saying is that so long as a nation is in misery we should try to keep their birthrate down. Not doing that is one of the major causes of the misery in the Third World. We gave them vaccines and antibiotics, without realizing that the average number of children per family to reach puberty was going to skyrocket, and this would lead to a population crisis.
    No, of course it is not enough. But it is essential, because without survival nothing else matters.
    Well then take heart from the fact that the second derivative of population went negative around 1980, because it turns out that the most effective contraceptive is prosperity. The population will reach ten billion around the end of this century and then start falling, for the first time in tens of thousands of years.

    Of course then you'll have to worry about the economy. Every economic model since Adam Smith assumes (without comment) that a steadily increasing number of producers and consumers will be its engine of prosperity.
    Your argument is persuasive. But then why did I have to launch a food drive for Ethiopia in the early 1980s? Why weren't they munching away on all those cheap American corn flakes that you claim are for sale in every bazaar?
    China has a long history of colonialism that is nothing like the form practiced by the Western nations. Their Buddhist monks brought the Iron Age to Japan and Korea, complete with (their own) written language and (their own) legends and other cultural motifs, without absorbing them into China. Of course Vietnam wasn't so lucky. And neither is Tibet, who already had their own Buddhist monks, written language and Iron Age technology.

    We're still expecting China to "rescue" Greece by making an offer they can't refuse.
    The sun sets on every empire eventually. Who knows when it will be our turn? If we don't start electing a better class of politicians, then perhaps within our (yours and mine) lifetime.
     
  10. Asguard Kiss my dark side Valued Senior Member

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    Strange, how about the WHO for a reference (referencing amongst others the CDC)

    Then there is the issues with low calcium and magnesium

    http://www.who.int/water_sanitation_health/dwq/nutdemineralized.pdf
     
  11. KilljoyKlown Whatever Valued Senior Member

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    But I just read a report that said you could get all the minerals you need in your diet. So the only time pure water would be much of an issue is if you have a sub-nutritional diet. I know many millions of people in this world do have a sub-nutritional diet. Currently I do not.
     
  12. Asguard Kiss my dark side Valued Senior Member

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    Did you read the article? Paticually the bit I posted about the magnesium and calcuium in diet not making up for deficiency and the deficiency is a separate mater from water intoxication which is a lethal condition caused by the intake of to much pure water. Follow the link I posted and actually read it
     
  13. Billy T Use Sugar Cane Alcohol car Fuel Valued Senior Member

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    During atypical times, like draughts, westerners with surplus food should help feed the hungry and starving; but not chronically supply food. During the draught, it is the lack of rain, not cheaper food available than local production can provide that is why adequate food is not produced locally.

    I don´t think boxes of cereal are sent, bulk items like rice etc. that are part of the native diet are sent now. This supply is not always available. Basically mainly when there are production surpluses that can not be more profitable sold. Soon, if not already the destruction of local farming by well meaning organizations will end. There are ever more people of means in China, etc. and they are eating more meat too. Thus, the demand is or soon will be chronically greater than even the fertile Mid West can produce with its very industrialized mass production agriculture - a modern miracle.

    What will be interesting to follow, is when poor Americans can not even afford “Franks & Beans” as the Chinese, etc. can and will be bidding the prices up with demand greater than supply. Imports by China of basic grains (to feed their pigs - more than all in the rest of the world! etc.) are increasing at about 15% per year now.

    In the US´s capitalistic system, it will be hard to tell privately owned Cargill they can not sell to the highest bidder. There may be food riots, and serious political changes coming in the next decade. The Chinese curse (May you live in interesting times) is being made real by the Chinese both in food demand and dollar problems.

    Just to put in a few "on topic" words, I note (and very few know) that there is more energy stored in a barrel of salt* than in a barrel of oil but no one has yet figured out how to utilize it and great quantities of fresh water would be required plus the power level would be low. The osmotic pressure across a membrane of pure salt against pure water will lift a column of water several hundred (I forget exact value) feet high. I.e. greater hydrostatic pressures than most hydroelectric dams have available.

    * This may seem more plausible to you when you think of the solar energy absorbed to turn a inland sea into a salt flat. When some salt enters into water solution it "falls down" into a very deep energy hole. Fundamentally, this is why it takes a lot of energy to separate salt from H2O. Again, it is sad that no one has discovered how to economically capture the energy being released, as we can when a rock falls down into a deep gravity hole. A few salt / water motors exist, but they are just toys.
     
    Last edited by a moderator: Jun 3, 2012
  14. Saint Valued Senior Member

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    Why is seawater salty?
    Where is the source of NaCl for seawater?
     
  15. Saint Valued Senior Member

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    Can we us seawater for irrigation?
    Will it kill the crops?
     
  16. Asguard Kiss my dark side Valued Senior Member

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    You ever herd of soil salinity problems, huge sections of farm land in Australia have been destroyed because of salt from rising water table caused by irrigation. What do you think would happen if that irrigation water was also brine.

    You ever seen a salt farm on the coast line, sea water is allowed to flow in and then evaporate leaving the salt. You think anything will grow there apart from salt bush?
     
  17. Billy T Use Sugar Cane Alcohol car Fuel Valued Senior Member

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    NaCl dissolves in rivers and ends up in the sea.

    About 200 years ago, when the age of the Earth was a subject of much discussion (Religious folk stating it was less than 6000 years old as that is what the bible tells) a calculation, not badly done*, was made to get a scientific estimate of the age of the Earth, based on the salt content and flow rates of many rivers. (Assuming that at "T=0" the oceans were pure H2O.)

    * Giving a very much too small answer; however, very much greater than 6000 years.
     
  18. Billy T Use Sugar Cane Alcohol car Fuel Valued Senior Member

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    Here is some graphical data showing how Africa is ever more dependent upon the US´s surpluses being dumped there, instead of becoming self sufficient in food with local production:

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    The road to hell is paved with good intentions! (Let´s feed the hungry.)
     
    Last edited by a moderator: Jun 4, 2012
  19. Fraggle Rocker Staff Member

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    That will not happen soon. It's well documented that the greatest nutritional problem among America's poor is obesity! When foreigners tell me they want to come to America and interview our poor people to find out for themselves what their lives are like, I always tell them that the easiest way to find a large number of poor Americans is to go to McDonalds.

    The only poor people who are undernourished are the ones with mental issues. In the 1960s and 70s, we decided as a society that it was unfair to lock people up in mental institutions against their will just because they were not taking care of their health. So today you have to let them out after three days.

    I understand. It seems that most homeless people eventually end up in Los Angeles because you can sleep outside there about 330 days a year. I'd rather sleep in a park in L.A. and panhandle for food than be locked up in a psych ward. (My wife worked in one for many years so she feels the same way. Just being there not locked up was horrible.)

    When you get down to the people who are so crazy or so poorly adjusted that they literally can't take care of themselves, then you find people who don't get enough to eat. But that's a ridiculously small segment of the population. I have seen people walk up and stuff hot dogs in their mouths. In a culture like ours where the "average weight" is now what we used to call "overweight," we can't stand the sight of someone who isn't eating enough.

    AIDS, gunfights, drug addiction, domestic abuse, drunk driving, yatta yatta, we'll put up with all that. But starvation??? No way! Everybody eats in America. Even our pets are overweight.
    That's an urban legend. It was made up by an Englishman who had never been to China.

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  20. Billy T Use Sugar Cane Alcohol car Fuel Valued Senior Member

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    To Fraggle:

    I agree with you- America´s main nutritional problem currently is obesity. That is partly caused by the very cheap food and the profits to be made by selling it. Food is very small part of typical frugal, middle class, American´s budget in part because of the fertile Mid West, but more due to the oil based agriculture that has developed in the US.

    There was a study more than 20 years ago that concluded ~95% of the cost of an Idaho potato, eaten in NY City, was the oil (and gas or electricity) used to produce it, ship it, and cook it there (and it is much worse now as back then oil was much cheaper).

    If the dollar has collapsed, only the military (and martial law forces) will get much oil derived products. This combined with fact that typical items on your table have traveled more than 1000 miles, often by truck, to get there, will solve America´s obesity problem –to vastly under state the effect of a collapsed dollar on the food consumption in the US.

    Part of the problem as I mentioned in recent post, is the US´s capitalistic system is not well designed to tell food processors, like privately owned Cargill, that they can not sell to the highest bidder (which with dollar collapsed and many without jobs in the US, that would be China.)

    China is already at the limits of its internal food production capacity and with a population that is rapidly increasing in wealth and eating much more meat. Why their imports of basic food stocks, (grains etc) are growing about 15% annually. Pork is the favorite meat in China; they currently have more pigs than all the rest of the world combined does. Already they cannot feed them without these grain imports. Their demand for food (including animal feed) will only grow worse. “Dr China” will cure the US´s obesity problem in only a few years.

    ---------------------

    “… The number of Americans receiving food stamps rose to a record 41.8 million in July {2010} as the jobless rate hovered near a 27-year high, the government said.

    Recipients of Supplemental Nutrition Assistance Program subsidies for food purchases jumped 18 percent from a year earlier and increased 1.4 percent from June, the U.S. Department of Agriculture said today in a statement on its website. Participation has set records for 20 straight months. ..." From October 2010 article here: http://www.bloomberg.com/news/2010-...-41-8-million-americans-in-july-u-s-says.html

    With both rapidly growing food needs and rapidly rising prices, how long do you think the US can afford this cost, especially if Republicans get control of either house of Congress. US already has serious budget* problems, with baby boomers now collecting Social Security, instead of being in their peak earning and tax paying years.

    * Except the US government is so dysfunctional it does not even have a budget and has not had one for three years!
     
    Last edited by a moderator: Jun 4, 2012
  21. DaveC426913 Valued Senior Member

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    Look up electrolyte balance.

    The way it can kill you is by knocking your Na, C and K electrolytes out of balance, causing your muscles (such as your heart) to stop working.

    It is identical but opposite to dehydration (electrolyte balance is the reason athletes drink vitamin-enhanced drinks instead of (or at least in addition to) plain water).
     
  22. DaveC426913 Valued Senior Member

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    The problem with providing fresh water (and food while we're at it) to the impoverished parts of the world is not one of how to make it or where to get it. The problem is distribution and cost of processes. All those desalination plants and the resources they require for building, transporting and maintaining just cost too much. Impoverished countries can't afford them.

    We have solutions, what we don't have is money.

    There are two ways to obviate this:
    1] Someone must invent a cheap, and inexpensively-maintained-onsite device that can be mass-produced. And until they do,
    2] Other nations must donate their money to build, transport and maintain the expensive versions. And that means citizens need to donate.
     
  23. Saint Valued Senior Member

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    Why not every home has a reservoir to collect rainwater and purify it?
     
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