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Beth Stackpole
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In search of fresh water
Beth Stackpole   10/25/2012 7:22:48 AM
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Very interesting development, Ann. Providing a more economical way to attack the desalination process could really make a big difference in pushing more of these projects to the fore and help them gain a foothold in developing areas that are really desparate for fresh water sources.

bob from maine
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Re: In search of fresh water
bob from maine   10/25/2012 11:13:23 AM
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When reading of flash-tube boilers I envisioned tubes heated to several hundred or more degrees, not 70-130. The concept of having water spray and evaporated steam in close proximity without excessive mixing is interesting. I wonder if flash-tube could be economically superior to Reverse Osmosis? Certainly the next 30 or so years will see the need for many more water purification methods.

Ann R. Thryft
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Re: In search of fresh water
Ann R. Thryft   10/25/2012 12:55:53 PM
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Reverse osmosis and other membrane technologies are the methods I'm more familiar with and have heard mentioned more often, so I was surprised to discover that thermal distillation is the technology used in the majority of installations. Although RO presumably uses somewhat less energy, both processes are quite intensive energy users. Re temperatures, thermal distillation is a form of vacuum distillation, which allows water to boil at a lower than normal temperature due to lower pressure. The Wikipedia article on desal is helpful.

Ann R. Thryft
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Re: In search of fresh water
Ann R. Thryft   10/25/2012 12:48:26 PM
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I've been watching the desal controversy for several years as it's been debated locally. Although it's not the only one, infrastructure cost is definitely one of the problems that must be overcome.

jmiller
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Re: In search of fresh water
jmiller   10/30/2012 9:34:48 PM
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I think often problems like this are solved by going through a set of steps where the technology to solve the problem is solved and then economics come in and are improved and then the technology to solve the problem is improved and then the economics come in.  It's a cycle of improvement that ends up developing a final solution.    It's fun for me to watch because it just shows the never give up attitude of engineers. 

NadineJ
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Re: In search of fresh water
NadineJ   10/26/2012 12:55:22 PM
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Desalinization isn't a good long term solution.  It's been used in Israel for years for crop irrigation.  The strawberries in Israel today aren't nearly as delicious or nutritious as they were decades ago.  I think the berries are telling us something.  Legalizing and building infrastructure to utilize grey water would offer a longer solution for potable water shortages.

This may be easily used for manufacturing and energy creation.  Many newer processes seem to involve massive amounts of fresh water.

Nicely written.  Very informative.

Ann R. Thryft
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Re: In search of fresh water
Ann R. Thryft   10/29/2012 11:49:53 AM
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Thanks, Nadine. Your POV is held by many here, regarding using other options such as graywater conversion and conservation. The problem with conservation in Santa Cruz County is that we've done just about as much as we can, short of graywater conversion both public and private: our water usage rates here are very low already compared to other areas of the US. And why we haven't done graywater conversion more on a public scale, I don't know--it seems so obvious.

NadineJ
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Re: In search of fresh water
NadineJ   10/29/2012 5:25:21 PM
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There are very strict restrictions on grey water usage here in California.  Regulations loosened up a little a few years ago.  Many people in the Bay Area promote grey water usage, and sell how-to kits and books.  Technically, some of the movement is breaking the law but it's moving the debate in a positve direction.

My POV is based in research and observation.  Desalinization seems like a good idea but only offers short term relief.

Ann R. Thryft
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Re: In search of fresh water
Ann R. Thryft   10/30/2012 11:51:00 AM
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Nadine, I agree about graywater usage. I live in a hotbed of it here in Santa Cruz county. If it wasn't for the expense, we would have installed one a long time ago on our own property. I still plan to, but it's still behind other homeowner fixup priorities. That's a big part of the problem in leaving it up to the private sector, i.e., homeowners. I wish there were incentives like tax deductions, such as there have been for solar.

jmiller
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Re: In search of fresh water
jmiller   10/30/2012 9:51:12 PM
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I do agree with the idea of tax breaks to encourage developement of technologies that make things better or cheaper.  But I struggle with tax breaks for homeowners just to put in the solutions.  I'd rather see the government spending money to make things more affordable, rather than giving us money to use products that aren't financially viable right now.

Ann R. Thryft
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Re: In search of fresh water
Ann R. Thryft   11/6/2012 2:44:53 PM
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jmiller, personally I'd rather see technology get implemented sooner rather than later for several reasons: makes more people aware of it, gets accepted faster, and helps bring down costs sooner, among them. Government tax breaks can help all these happen. At least using our current economic model, it's higher volumes in manufacturing that can help to make things more affordable.

jmiller
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Re: In search of fresh water
jmiller   11/29/2012 10:08:49 PM
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I'd like to see technology implemented as soon as possible. But I don't have a lot of faith in our current economic model.  I struggle to support continual government funding to in some cases force development in an area that might not be viable.

jmiller
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Re: In search of fresh water
jmiller   10/30/2012 9:39:21 PM
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So why aren't the strawberries as good. Is the water quality not as good? Did some of the salt not get our of the water? I agree with the idea of using grey water because that would be available in a lot more of the middle United States. But I'm also curious with some of the problems being experienced with current systems.

NadineJ
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Re: In search of fresh water
NadineJ   10/31/2012 5:38:17 PM
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I haven't read anything definitive about why the strawberries aren't as tasty or nutritious.  But just taking the salt out doesn't turn seawater into freshwater.  It may be drinkable but it's not the same.

Maybe a Gadget Freak will come up with something for grey water or capturing rain water for the lawn.

Ann R. Thryft
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Blogger
Re: In search of fresh water
Ann R. Thryft   11/5/2012 3:25:53 PM
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There are a lot of DIY rain barrel systems around, at least where I live. A DIY graywater system is a great idea for a Gadget Freak column.

Mydesign
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Re: In search of fresh water
Mydesign   10/29/2012 2:00:47 AM
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Beth, we know that eventhough 2/3rd of earth is covered by water, most part of the world still have scarcity of drinking/fresh water. So the best option to bridge the gap is purification or desalination of sea water. Most of such projects required huge investment and complex technology/machinery for purifying the salt water. A new more economical and simple technology has yet to be discovered and I think these new technology may comes under that category.

jmiller
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Re: In search of fresh water
jmiller   10/30/2012 9:28:05 PM
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I like articles like this that show opportunities for engineers to come through with a way to improve life in a significant way, not just make a better mouse trap.

Ann R. Thryft
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Blogger
Re: In search of fresh water
Ann R. Thryft   11/5/2012 12:19:48 PM
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jmiller, thanks for the comment--I enjoy reporting and writing articles that showcase engineers who've designed something with innovation and ingenuity, which can make major improvements in our lives, too.

Tim
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Plastic Material
Tim   10/25/2012 7:17:44 PM
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It would be interesting to know the base resin used to add the copper fibers.  The 50% letdown of copper is pretty significant.  Good article.

William K.
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Platinum
Desalination
William K.   10/28/2012 7:43:08 PM
It would seem that removing the salt and other minerals froom seawater would be the preferred method, not only because of the magnesium recovered, but because sea water is an easy to get resource that we won't be in any danger of running out of. If the berries are different after a few years it is probably because of cost being taken out of the growing process, not because of the water. What quality reduction has been implemented to increase profits?

Of course desalination does need a lot of energy, I don't know any way around that, one other option is for people to not live in that area that has no water. Did anybody ever stop and consider that some places that seem uninhabitable ARE UNINHABITABLE? Even if some developer puts houses there?

REmember the Bob Dylan quote: "One should never be where one does not belong"? It is also appropriate for areas without water. 

The problem is that while we can make potable water out of seawater, we can't make the energy to do the process.

Ann R. Thryft
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Re: Desalination
Ann R. Thryft   10/29/2012 11:50:28 AM
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William, I think that's an excellent point: some areas are simply not inhabitable by a certain number of people after a specific threshold has been passed, without either importing huge amounts of water, such as in Los Angeles, or without needing a huge, expensive, artificial infrastructure of some kind. We have come to think such an infrastructure is the norm, but it's quite recent in human history. And thanks for quoting Bob Dylan :)

jmiller
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Re: Desalination
jmiller   10/30/2012 9:43:56 PM
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I do agree there are areas we shouldn't be.  However, it's interesting how many people choose to live there.  In the case of a lot of cities, more and more people are living in a n area that just can't support the population.  In the case of some cities, we have literally built in areas below sea level.  In the end, sometimes, I think every time we build a solution to a problem.  The world finds a way to build a bigger idiot.

Mydesign
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Sea water purification
Mydesign   10/29/2012 1:23:42 AM
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Ann, I know in most of the Arab countries, they are distilling the sea water for residential purpose other than drinking. Am not sure about the technology they are using for this purification, but I heard that it's a multi stage purification, where water is evaporating to remove the salt content. In such cases I think the new technology seems to be superior and affordable.

Ann R. Thryft
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Re: Sea water purification
Ann R. Thryft   10/29/2012 11:51:49 AM
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Mydesign, that's a distillation process you describe, so it sounds like the majority form of desalination, the one I cover here. I'd be interested to know more about what exact processes are being used and what challenges, obstacles, problems, etc. the Arab countries have encountered. I'm also very curious about reverse osmosis, the much less often used method, and wonder why it isn't used more often.



Mydesign
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Re: Sea water purification
Mydesign   10/31/2012 12:23:12 AM
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Ann, RO water purifications are commonly implemented with house hold water purifiers. It's a five stage purification method and so far I had not seen it with any large scale implementation.  If my knowledge is right, Arab countries are implemented multi stage flash distillation method, where water is heating and reheating multiple times. Now there are some new technologies like osmosis technologies (Reverse, Forward), Electro dialysis and Distillation methods like Thermal Distillation, Multi-Effect distillation etc are implemented in certain countries.

Jack Rupert, PE
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Pipe Cleaning
Jack Rupert, PE   10/29/2012 10:46:11 AM
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Very interesting article, Ann.  Living in the Midwest on the shores of one of the largest bodies of fresh water in the world, I didn't have a lot of background in how desalination is accomplished.  Using the method you described, I would assume that they materials being used would have to be rather "slippery" too.  If you are spraying salt water on them specifically to cause steam and leave the salt and contaiminate behind, I would think that the pipes would be covered in a relatively short period of time...either that or there is a good method for continual cleaning.

Ann R. Thryft
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Re: Pipe Cleaning
Ann R. Thryft   10/29/2012 5:46:28 PM
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Thanks, Jack. The surface material must be both sticky and slippery, so the chemical- and salt-laden seawater stays on only long enough to evaporate completely and efficiently, but no longer. Ideally, it also must shed deposits relatively easily. There's no continual cleaning here: regular maintenance is required, as with metal, but lower process temperatures allowed by the material will help residues build up more slowly.



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