Why is it difficult to turn seawater into drinking water?

Why is it difficult to turn seawater into drinking water?
In order to solve water shortage problem.

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The salt is dissolved in the water and must be removed.

To do so on any large scale requires a large amount of machinery.

The Island of Aruba in the Carribean makes all of it's drinking water via the worlds largest desalinization plant.

 

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A relatively new process called nano osmosis is the most energy and cost efficient way to desalinate...

search: nano-osmosis desalination

 

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You can look up the various processes used to desalinate water. I suppose what Keith says is so, but up until now it's an expensive, nearly unfeasible process except when there is really no alternative. I've have read that while 20th century wars have been about oil, 21st century wars will be about water. And yet, the Iran-Iraq War of the 1980's was about water (and I don't know what the present war in Iraq is about anymore). Short answer to your question: I don't know. Sorry. :shrug:

 

There is more fresh water in the asteroids than can be found on Earth.
And the first commercial spaceship docked this week at the space station.
It will be an interesting century to be alive.

(Maybe a water meteor breaks up when entering earth's atmosphere, and harmlessly rains all over the place.
Then again, maybe not--maybe to best use it where it lies frozen).

 

Can we use solar energy to evaporate the seawater and then condense it?

 

Mmmmm... Well, just two things in passing, one is I think many people forget the TREMENDOUS amount of fresh water in the U.S./Canadian Great Lakes. The other is the billions of billions of gallons of fresh water in the rivers of the world (that aren't that polluted in every case) that simply runoff into the oceans every single day.

The true major problem is that much of the water is simply in the wrong place to meet human needs. But there's really no need to go looking into outer space to get it - just work on better ways to divert/transport what we have and employ the latest desal process to a greater degree in the true arid regions of the world.

 

Sure. A solar still.

 

You do realise that river mouths are important too? Esteries tend to be where most ocean fish spawn and that not even looking at what would happen if there was no ware returning to the ocean. How concentrated would it end up?

 

Water meteors!? Way out Keith! You force me to reprint this:

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How much of Jupiter's moon Europa is made of water? A lot, actually. Based on the Galileo probe data acquired during its exploration of the Jovian system from 1995 to 2003, Europa possesses a deep, global ocean of liquid water beneath a layer of surface ice. The subsurface ocean plus ice layer could range from 80 to 170 kilometers in average depth. Adopting an estimate of 100 kilometers depth, if all the water on Europa were gathered into a ball it would have a radius of 877 kilometers. To scale, this intriguing illustration compares that hypothetical ball of all the water on Europa to the size of Europa itself (left) - and similarly to all the water on planet Earth. With a volume 2-3 times the volume of water in Earth's oceans, the global ocean on Europa holds out a tantalizing destination in the search for extraterrestrial life in our solar system.
http://apod.nasa.gov/apod/ap120524.html

 

Condensed water? What do you mean? Like canned milk? Just add...water....?

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Condense the vapor.

 

The other sad part of that is that all the discharge from the cities upstream has accumulated at the estuary. Sounds gross anyway.

Another worry about fresh water is the depletion of glaciers that feed all the major rivers. Presumably there will always be snow melt, but imagine that becoming the new normal. Then if a dry spell were to set in, you could imagine the Nile or Yangtze going dry. It would be a disaster.

I like this idea of deriving fresh water from sea water. I think it's forward thinking. It would be interesting to live on an island where everybody was on the same page with ideas like this and cooperated to really do something completely new and different that actually worked as as far as low-impact living is concerned.

 

Dean Kamen developed a very similar device. It uses anything combustible (cow dung, coal, anything) and any sort of water to produce 250 gallons of drinking water a day and 200 watts of electric power. Its cost (if mass produced) would be around $1000 each.

 

It's not that it's difficult, it's just expensive when scaled up to the needs of a growing city. So it's not the first choice of a way to supply anyone's water needs. But it is an option that can be used if your back is up against the wall. As water becomes more scarce driving up it's price, the option to desalinate will become more attractive and common.

 

On Aruba, which is a desert island and has no fresh water sources, world's first land based large size desalination plant based on plate evaporator module

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Cheeeee---yeck!

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It would be great to see this come to fruition. Availability of clean water ought to be considered a basic human right.

Excellent. I'll look into that. I have played around with this wondering how it might be done using mostly natural material available to the locals. For example, suppose all they needed to import were rolls of aluminized plastic reflectors and maybe a few basic machine parts. In other words make it as dirt cheap as possible, so it's readily available to as many people as possible.

The thing I had in mind was a solar collector that uses a gutter made of clay that accepts the reflective sheets and forms a parabolic focus on a pipe -- now it gets dicey -- made of clay also? Maybe glazed? Something that can boil water for starters, without requiring fuel. Once that's worked out, the desalination comes into the reach of just about anyone. I'm not sure how easy it is to find clay in areas that would benefit from this but it was a idea that interested me nonetheless.