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Water crises

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Tweefo
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« on: January 03, 2018, 06:22:55 AM »

In my travels around the country, I've often came across this one: A town councilor, maybe even the mayor, showing off to his or friends, opened the sluice gates of the town's dam and left without closing it again. This always happened in a time of drought, on a weekend, and is then the main reason the town is running out of water or why it is so expensive. It is of course also always a black councilor, this would never have happened in the old white government days. An all SA urban legend as far as I know, but where and how did it start?
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brianvds
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« Reply #1 on: January 03, 2018, 09:44:36 AM »

I suppose it's possible that it may be based on some real event, but obviously the story just plays into everyone's frustration with officials living in wasteful luxury, and showing it off, while us plebs have to make do without. As with all such stories, it is not without its element of truth.

Anyone here from Cape Town? Any first-hand accounts of the water crisis there? I last visited the Cape around 2002; it was so beautiful I wanted to immigrate there on the spot. It's been a recurring fantasy. Nowadays I'm glad I didn't. I can deal with lots of things, but drought is not among them.

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st0nes
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« Reply #2 on: January 03, 2018, 11:17:34 AM »

Anyone here from Cape Town? Any first-hand accounts of the water crisis there? I last visited the Cape around 2002; it was so beautiful I wanted to immigrate there on the spot. It's been a recurring fantasy. Nowadays I'm glad I didn't. I can deal with lots of things, but drought is not among them.
Drought isn't that bad--yet--but when, or if, the water runs out we've got ourselves a full-blown crisis. So we're trying our best to save water wherever we can--taking a 2 minute shower every second day, making sure to take a bucket into the shower with you to catch the grey water; flushing the bog with the water from the shower (but following the maxim "if it's yellow, let it mellow, if it's brown flush it down"); swimming pool is empty (apart from the kreepy-krawly hose and a dog's old bed); car is filthy, but that cloud has a silver lining: I don't have to waste time washing it.

The irony is that we have loads of water, in fact we're surrounded by it--but hardly  any of it is suitable for consumption. It needs to be purified or desalinated first, which means a huge capital outlay for the infrastructure required. The other alternative is tapping the table mountain chain aquifer, which is said to contain six times as much water as the Vaal dam, but there are worries that extracting large quantities from it will cause sea water to infiltrate the aquifer rendering it useless in the future.

But maybe we'll have enough rain over the remainder of the summer and autumn to get us over the hump, and then the experts are predicting better winter rainfall this year....
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brianvds
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« Reply #3 on: January 03, 2018, 12:04:10 PM »

I saw an article the other day about a Capetonian who has developed a machine that extracts water from air. It looks quite suitable for home use, but models that produce a lot of water are hideously expensive.
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BoogieMonster
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« Reply #4 on: January 03, 2018, 13:46:16 PM »

I saw an article the other day about a Capetonian who has developed a machine that extracts water from air. It looks quite suitable for home use, but models that produce a lot of water are hideously expensive.

I doubt you could efficiently produce any sufficient amount of water this way. I'm extremely skeptical of stuff like this. Smells a bit snake-oily
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Mefiante
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« Reply #5 on: January 03, 2018, 15:30:46 PM »

I doubt you could efficiently produce any sufficient amount of water this way. I'm extremely skeptical of stuff like this. Smells a bit snake-oily
Correct.  There are two relatively simple ways to extract humidity (i.e., water vapour) from air: (1) chemically by means of a desiccant such as silica xerogel, or (2) thermodynamically by condensation on a cooled surface.  The first option leaves you with the problem of separating the water from the desiccant, which is usually done by heating and drying the desiccant, and water recovery would also require a condensation capture mechanism.  The second requires a refrigerating arrangement with a large surface area, e.g. finned tubes.  Both systems would require substantial amounts of energy to produce good quantities of water.  Moreover, both systems produce distilled water which isn’t very good for drinking over the long term because it’s missing lots of dissolved minerals.

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brianvds
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« Reply #6 on: January 03, 2018, 17:25:57 PM »

Found some articles online about it:

https://techcentral.co.za/sa-firm-squeezes-water-from-thin-air/58025/

https://www.news24.com/SouthAfrica/News/We-can-create-rain-during-sunshine-SA-company-makes-water-from-air-20151029-2

The larger machines look like they are a viable option for home use, but alas, they are hugely expensive. Toys for the rich.

I doubt whether the absence of minerals will be much of an issue. Surely you get more minerals from food than from the minute amounts dissolved in water? I wouldn't know. Something to go read up on when I have time.

Some years ago I saw a video with a similar gadget: a water bottle for cyclists that fills itself from the air. Probably also a very expensive gadget. Could come in handy if you get lost in the desert, mind you.
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Tweefo
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« Reply #7 on: January 03, 2018, 17:47:02 PM »

Quote
Moreover, both systems produce distilled water which isn’t very good for drinking over the long term because it’s missing lots of dissolved minerals.

Back in my farming days, I drank some distilled water and it tasted funny, not like water at all. The water was to be mixed with some stuff, I can't remember what and then injected into the sheep.
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brianvds
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« Reply #8 on: January 03, 2018, 18:27:58 PM »

Well, there ya go: distilled water will kill you:

http://www.mercola.com/article/water/distilled_water.htm

 Roll Eyes
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Mefiante
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« Reply #9 on: January 03, 2018, 20:31:38 PM »

The short of it is that many dissolved minerals occur as salts.  Dissolved in water, a concentration-dependent portion of them is in a chemically dissociated state, which makes them much easier for the body to assimilate and to process.  Our bodies are well adapted to drinking water that contains dissolved solids and mineral salts.  So, unless you’re eating mostly stews and soups, drinking distilled water over extended periods is likely to result in certain mineral deficiencies.  The funny taste of distilled water is mostly due to the absence of those minerals and the water’s pH.

Drinking distilled water won’t kill you.

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brianvds
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« Reply #10 on: January 03, 2018, 22:25:51 PM »

The short of it is that many dissolved minerals occur as salts.  Dissolved in water, a concentration-dependent portion of them is in a chemically dissociated state, which makes them much easier for the body to assimilate and to process.  Our bodies are well adapted to drinking water that contains dissolved solids and mineral salts.  So, unless you’re eating mostly stews and soups, drinking distilled water over extended periods is likely to result in certain mineral deficiencies.  The funny taste of distilled water is mostly due to the absence of those minerals and the water’s pH.


But don't those exact same salts occur in copious amounts in meat and vegetables?
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Mefiante
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« Reply #11 on: January 04, 2018, 06:04:23 AM »

But don't those exact same salts occur in copious amounts in meat and vegetables?
Other foods do contain minerals and salts but not in the same readily accessible and easy-to-extract way as they are usually found in water, i.e. in the chemically dissociated state.  The point is that it’s much harder for our metabolic processes to extract these nutrients useably from other food sources even if they do contain them in amounts similar to, or higher than, water.  And this difficulty, over prolonged periods, can eventually lead to deficiencies.

'Luthon64
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