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What's wrong with water desalinization? I've often wondered...

#1 User is offline   Hanoi5 

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Posted 2010-September-22, 07:30

Many countries are facing (and more will face in the future) a shortage of water. Rivers, trees and animals are also suffering from this and so I wonder what's the problem with using desalinizated sea water. Some countries have it. In fact, what about reviving rivers with it? Maybe the water cycle will start over again?

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#2 User is offline   pooltuna 

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Posted 2010-September-22, 07:36

Hanoi5, on Sep 22 2010, 08:30 AM, said:

Many countries are facing (and more will face in the future) a shortage of water. Rivers, trees and animals are also suffering from this and so I wonder what's the problem with using desalinizated sea water. Some countries have it. In fact, what about reviving rivers with it? Maybe the water cycle will start over again?

Basically a cost effective method to do this is hard to come by. As far as restoring rivers have you ever noticed the quantity of water flowing in most of them? Of course I may be biased as I live in New Orleans. Nevertheless rivers flow one direction for a simple reason and moving that much desalinated or to be desalinated seawater uphill ain't easy.
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#3 User is offline   vang 

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Posted 2010-September-22, 07:42

the problem is the cost. quote wikipedia:

"Large-scale desalination typically uses extremely large amounts of energy as well as specialized, expensive infrastructure, making it very costly compared to the use of fresh water from rivers or groundwater."
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#4 User is offline   hrothgar 

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Posted 2010-September-22, 08:12

Hanoi5, on Sep 22 2010, 04:30 PM, said:

Many countries are facing (and more will face in the future) a shortage of water. Rivers, trees and animals are also suffering from this and so I wonder what's the problem with using desalinizated sea water. Some countries have it. In fact, what about reviving rivers with it? Maybe the water cycle will start over again?

Issue 1: Do you appreciate just how much water flows down a river?

Think of the amount of energy generated by a hydro electric plant... Now consider that you are (essentially) planning to run that hydro plant in reverse. (You are going to use energy to move water from the ocean somewhere else).

The power requirements for transportation alone would be astronomical.

Issue 2: It takes an enormous amount of energy to separate salt from H20

Issue 3: Salt water is incredible corrosive.
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#5 User is offline   pooltuna 

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Posted 2010-September-22, 09:39

hrothgar, on Sep 22 2010, 09:12 AM, said:

Hanoi5, on Sep 22 2010, 04:30 PM, said:

Many countries are facing (and more will face in the future) a shortage of water. Rivers, trees and animals are also suffering from this and so I wonder what's the problem with using desalinizated sea water. Some countries have it. In fact, what about reviving rivers with it? Maybe the water cycle will start over again?

Issue 1: Do you appreciate just how much water flows down a river?

Think of the amount of energy generated by a hydro electric plant... Now consider that you are (essentially) planning to run that hydro plant in reverse. (You are going to use energy to move water from the ocean somewhere else).

The power requirements for transportation alone would be astronomical.

Issue 2: It takes an enormous amount of energy to separate salt from H20

Issue 3: Salt water is incredible corrosive.

Something might be doable on a much smaller scale using parabolic mirror troughs in a solar still configuration where the desalinated water vapor is recondensed at at some height. This would probably require desert land near a salt water source.
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#6 User is offline   Gerben42 

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Posted 2010-September-22, 10:39

Quote

Issue 1: Do you appreciate just how much water flows down a river?


Just to get a feeling, the Indus river (one of Asia's main rivers) discharges about 6600 m³ / s into the sea. That's about 20000 bath tubs per second!

The Amazon river gets close to a million bath tubs per second.
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#7 User is offline   bd71 

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Posted 2010-September-22, 10:48

National Geographic magazine had a recent issue devoted to worldwide water supply issues. Here's a link to the brief blurb they had on desalinization...

http://ngm.nationalg...09/desalination
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#8 User is offline   luke warm 

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Posted 2010-September-22, 15:59

pooltuna, on Sep 22 2010, 08:36 AM, said:

Hanoi5, on Sep 22 2010, 08:30 AM, said:

Many countries are facing (and more will face in the future) a shortage of water. Rivers, trees and animals are also suffering from this and so I wonder what's the problem with using desalinizated sea water. Some countries have it. In fact, what about reviving rivers with it? Maybe the water cycle will start over again?

Basically a cost effective method to do this is hard to come by. As far as restoring rivers have you ever noticed the quantity of water flowing in most of them? Of course I may be biased as I live in New Orleans. Nevertheless rivers flow one direction for a simple reason and moving that much desalinated or to be desalinated seawater uphill ain't easy.

yeah but cold fusion will solve all that... all we gotta do is capture that delorean next time marty comes this way and reverse engineer it
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#9 User is offline   cloa513 

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Posted 2010-September-22, 18:44

Desalination (osmosis) uses a lot of energy because you need to the water to extremely high pressure. If you have a saline water at higher level to your plant, then you can save a lot of energy and money like we could have done in Perth (Canning Dam is saline and a few hundred metres above sea level) if we didn't have our idiotic Water Corporation who rejected the idea of an independent company.
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#10 User is offline   Hanoi5 

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Posted 2010-September-22, 19:10

Ok, since I already started with the questions, isn't plastic cheaper than metal? How about plastic aqueducts to transport the water from the plants to the people/rivers? How about sending the water underground?

I'll soon make a topic for cheap energy, so that my weird ideas can be used or banned forever from my mind.

View Postwyman, on 2012-May-04, 09:48, said:

Also, he rates to not have a heart void when he leads the 3.


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#11 User is offline   mike777 

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Posted 2010-September-22, 22:52

IN general I am really in favor of cheap energy...........really cheap...

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#12 User is offline   babalu1997 

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Posted 2010-September-23, 06:57

Hanoi5, on Sep 22 2010, 08:10 PM, said:

Ok, since I already started with the questions, isn't plastic cheaper than metal? How about plastic aqueducts to transport the water from the plants to the people/rivers? How about sending the water underground?

I'll soon make a topic for cheap energy, so that my weird ideas can be used or banned forever from my mind.

i am no engineer, but anyone who has installed plastic fencing know it cracks when exposed to the sun. to keep the thing supple you have to rub all sorts of treatment on it, much worse than whitewashing the picket fence.

plastic aint chep, costs a lot in pollution, and i think it even increases some cancers.

some plastics become porous after a while, and that is why sodas in plastic bottles go on sale after 90 days or something-- the companies hasve to get rid of it.

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#13 User is offline   hrothgar 

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Posted 2010-September-23, 09:04

mike777, on Sep 23 2010, 07:52 AM, said:

IN general I am really in favor of cheap energy...........really cheap...

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

I understand the forum is NOT

I don't think anyone on the forums is opposed to cheap energy.
I'm certainly not...

Would anyone out there be virtually opposed to (virtually) free energy?

<<Sound of crickets chirping>>

I suspect that the salient distinction is how one measures the actual cost of energy.

I know that many of us would argue that a cost system that deliberately ignores many of the costs associated with energy production will produce a suboptimal solution.

30 years ago, Sulphur Dioxide was one of the most significant externalities associated with many forms of energy product. Today, people are focused on Carbon Dioxide.

Hard to tell what issues we'll run into in the future. Conceptually, if energy really became cheap enough we might need to start worrying about waste heat.
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#14 User is offline   gwnn 

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Posted 2010-September-23, 09:19

mike777, on Sep 23 2010, 04:52 AM, said:

IN general I am really in favor of cheap energy...........really cheap...

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


I understand the forum is NOT

yes please, expensive energy all the way. rich Arabs, starving poor people please.
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#15 User is offline   hrothgar 

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Posted 2010-September-23, 09:32

Hanoi5, on Sep 23 2010, 04:10 AM, said:

Ok, since I already started with the questions, isn't plastic cheaper than metal? How about plastic aqueducts to transport the water from the plants to the people/rivers? How about sending the water underground?

I can't believe that I have to post this, but...

Water flows down hill.

Seas - the areas where water collects and the area where you find lots of salt water - are typically downhill from a whole lot of places.
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#16 User is offline   Hanoi5 

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Posted 2010-September-23, 11:13

hrothgar, on Sep 23 2010, 11:32 AM, said:

Hanoi5, on Sep 23 2010, 04:10 AM, said:

Ok, since I already started with the questions, isn't plastic cheaper than metal? How about plastic aqueducts to transport the water from the plants to the people/rivers? How about sending the water underground?

I can't believe that I have to post this, but...

Water flows down hill.

Seas - the areas where water collects and the area where you find lots of salt water - are typically downhill from a whole lot of places.

Aren't there underground rivers from which people collect water sometimes or maybe even rivers? I bet some of these rivers are drying and sending water to them would keep them alive...

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Besides playing for fun, most people also like to play bridge to win


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#17 User is offline   hrothgar 

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Posted 2010-September-23, 11:39

Hanoi5, on Sep 23 2010, 08:13 PM, said:

Aren't there underground rivers from which people collect water sometimes or maybe even rivers? I bet some of these rivers are drying and sending water to them would keep them alive...

Here, once again, the basic questions are

1. How you plan to move all this water from the sea to this river?
2. How do you plan to remore all of this salt from the sea water?

In all seriousness, find a topographical map of (wherever)

Figure out the amount of energy and infrastructure necessary to move a 100 kilos of water from point A to point B.

You seem fond of aqueducts.

Lets assume that you're able to run a pipeline from the sea shore off to your desert. We'll be charitable and assume that you're able to drill through any mountains that happen to be in the way....

Figure out how high point B is relative to sea level.

You're going to need to lift each and every liter of water at least that high in order to get this scheme to work.

For kicks ang giggles, here's a map that shows the average height for each state in the US. (As a useful point of reference, Niagara Falls are 176 heigh)

Posted Image
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#18 User is offline   Hanoi5 

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Posted 2010-September-23, 14:58

Look hrothgar, I have no idea of prices world wide or economy, I live in a country where gas is much less expensive than water, there are at least 3 exchange rates for the dollar and I can use my hard earned ( :D ) money abroad only after asking for permission; and that permission is for only $3600 a year; and it can be denied.

I'm just trying to move ideas around which might get people to work on solving the problems of the world.

It's true, I didn't think about the amount of earth that would have to be moved in order to put my not-well-thought aqueducts underground, but isn't there another way to move the water? How about a natural way? You know, evaporation, condensation, etc

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Also, he rates to not have a heart void when he leads the 3.


View Postrbforster, on 2012-May-20, 21:04, said:

Besides playing for fun, most people also like to play bridge to win


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#19 User is offline   onoway 

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Posted 2010-September-24, 21:33

a thought about moving water..ram pumps can be used to move water uphill and use virtually NO outside energy except to build the pump. All it requires is a degree of water pressure from the movement of the water it is trying to move. Although these pumps are commonly used with a river, surely waves or tides could provide that? The corrosion issue is another story, but there might well be some sort of liner which might be applied so as to avoid the problem of UV degradation of plastics.

I'm not sure exactly how much water such a pump could be designed to move, it might be that it could be used to refill an aquifer more efficiently than provide water for a city, as it is constant if unspectacular in its efforts. Also, I'm not sure how high such a pump can lift water...it might be that there would have to be a series of locks with a sort of waterfall at one end of each to provide a source of water energy for the next pump...

I have seen wooden irrigation channels from about 100 years ago which managed to climb what would appear to be about 100 feet or so, powered by a river. The cost of building the pump is small, it seems basically to be a set of one way valves. Also, the question of noise might an issue which needed to be addressed..

As far as what the water moves IN..aren't some of the viaducts built by the Romans to move water still in use today? Is salt water corrosive to all types of concrete, including those concretes not using portland cement?
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#20 User is offline   mike777 

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Posted 2010-September-24, 22:43

again cheap energy will help ...not perfect energy.......in a perfect world

Of course cheap is a debatable word.....most economic words are.....

if carbons are cheap so be it......no one is against free.....clean perfect energy.....


innovation......will help......incentives will work......others will hurt...

I guess I see this more as a process not an idealogy......but in any event the middle class pushing for less pollution is part of that process......but I dont think we will stand for blackouts...

As many have said the USA has an ancient power grid based on 1860 rather than say......1960 :blink:

again blame government for that not free markets.

Bottom line incentives work.....encourage innovation....
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