Posts Tagged ‘water’

by Jane Bird

New approaches to filtration and extracting moisture from air promise to alleviate the world’s looming water scarcity crisis.

Filtration is being transformed by thin sheets of graphene, a carbon-based material invented in 2004 at Manchester University. Rahul Raveendran Nair, the university’s professor of materials physics, says graphene has the potential to deliver large quantities of clean water via desalination and the removal of pollutants.

Meanwhile, improved technology for capturing water vapour from the air holds out hope for arid regions.

In April 2017, Prof Nair demonstrated that a multi-layer membrane made from graphene oxide can filter out the sodium chloride in seawater much more quickly and cleanly than existing techniques.

“The graphene filter is like a mesh or sieve with holes so small that salt molecules cannot pass through,” Prof Nair says. The filters were recently shown to be able to filter even the dye molecules of whisky, turning the liquid colourless.

The university is in talks with potential manufacturers with a view to enlarging the membranes — currently A4-sized — and demonstrating that the technology can be used in practical applications.

“We have shown it works in the laboratory, now we want to demonstrate it in realistic conditions,” says Prof Nair. He hopes full-sized desalination plants with graphene membranes will be possible within five years.

Commitments to existing desalination technology may hold back large-scale commercial development of graphene systems in the short term, Prof Nair says. However, he thinks that a small scale version of the graphene filter can be developed for bottles and household units within two years. To explore the possibilities, the university is collaborating with Icon Lifesaver, a company based in the east of England.

The business currently makes filters that can remove microbes, bacteria and viruses. Joe Lovegrove, technical manager of Icon Lifesaver, says: “Graphene has the potential to create the ultimate filter that can also take out chemicals, solutes, salts and compounds such as pesticides.

“Its scope is absolutely massive. It would give us effectively the ultimate water filter that you could use to convert water at any source from being dangerous to safe as quickly as you can drink it.”

Icon Lifesaver hopes to demonstrate that 400ml and 750ml bottles with easy-to-clean filters are viable for mass production. “People don’t want to spend time and effort cleaning,” says Mr Lovegrove.

“Initial studies are showing that all this is absolutely feasible with the graphene membrane — it performs superbly, better than anything else.”

Graphene filters would have the further benefit that they will not let any liquid through when they come to the end of their life. “This is an advantage over many existing water filters where it is impossible to tell if they still work properly,” Mr Lovegrove says.

During the next few months, the portable graphene filters will be tested to check that they work for chemical contaminants such as cadmium, copper, arsenic, nitrites, nitrates and pesticides.

Once volume production is under way, the bottles are likely to cost £100 to £150 each. 

In arid areas, clean water production tends to focus on extracting moisture molecules from the air and cooling them down until they form droplets.

Currently this only works where humidity is at least 60 per cent. It is also very energy-intensive, says Beth Koigi, co-founder of Majik Water, a company set up to solve the problem. Majik Water uses desiccants — sponge-like materials such as silica gel — which extract water from the air. This is then released when the gel is heated. It can be re-used many times.

“Our prototype can work in humidity of just 35 per cent, and uses simple equipment and techniques to minimise energy demand,” Ms Koigi says. Each device can generate 10 litres a day and runs on solar power.

The goal is to produce clean water for a price of one cent per litre, far cheaper than bottled water or boiling water to purify it, while removing the risk of mineral contaminants. Achieving the target price will depend on reducing the cost of the solar panels, which currently account for $1,000 of the $1,400 cost of a 20 litre device.

After initial research in California, development has transferred to Kenya where the team is testing whether customers prefer household devices producing 20 litres a day or community systems generating more than 200 litres. Research might continue in Kenya or move to the Atacama Desert Chile, the driest place on earth.

Silica gel is abundant, safe and cheap, so it will help keep costs down. The team is also watching development of metal-organic frameworks (MOFs), which can hold up to three times their own weight in water, compared with 35 per cent for silica gel. They could produce more water with less energy but are still at the stage of laboratory testing. At present they are expensive and unlikely to be widely available in the next five to 10 years.

https://www.ft.com/content/d768030e-d8ec-11e7-9504-59efdb70e12f

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By Paul Rincon

The first known interstellar asteroid may hold water from another star system in its interior, according to a study.

Discovered on 19 October, the object’s speed and trajectory strongly suggested it originated beyond our Solar System.

The body showed no signs of “outgassing” as it approached the Sun, strengthening the idea that it held little if any water-ice.

But the latest findings suggest water might be trapped under a thick, carbon-rich coating on its surface.

The results come as a project to search for life in the cosmos has been using a radio telescope to check for radio signals coming from the strange, elongated object, named ‘Oumuamua.’

Astronomers from the Breakthrough Listen initiative have been looking across four different radio frequency bands for anything that might resemble a signal resulting from alien technology.

But their preliminary results have drawn a blank. The latest research – along with a previous academic paper – support a natural origin for the cosmic interloper.

Furthermore, they measured the way that ‘Oumuamua reflects sunlight and found it similar to icy objects from our own Solar System that are covered with a dry crust.

“We’ve got high signal-to-noise spectra (the ‘fingerprint’ of light reflected or emitted by the asteroid) both at optical wavelengths and at infrared wavelengths. Putting those together is crucial,” Prof Alan Fitzsimmons, from Queen’s University Belfast (QUB), one of the authors of the new study in Nature Astronomy.

He added: “What we do know is that the spectra don’t look like something artificial.”

Their measurements suggest that millions of years of exposure to cosmic rays have created an insulating, carbon-rich layer on the outside that could have shielded an icy interior from its encounter with the Sun.

This process of irradiation has left it with a somewhat reddish hue, similar to objects encountered in the frozen outer reaches of our Solar System.

“When it was near the Sun, the surface would have been 300C (600 Kelvin), but half a metre or more beneath the surface, the ice could have remained,” Prof Fitzsimmons told BBC News.

Previous measurements suggest the object is at least 10 times longer than it is wide. That ratio is more extreme than that of any asteroid or comet ever observed in our Solar System. Uncertainties remain as to its size, but it is thought to be at least 400m long.

“We don’t know its mass and so it could still be fragile and have a relatively low density,” said Prof Fitzsimmons.

“That would still be consistent with the rate at which it is spinning – which is about once every seven-and-a-half hours or so. Something with the strength of talcum powder would hold itself together at that speed.”

Molten core

He added: “It’s entirely consistent with cometary bodies we’ve studied – with the Rosetta probe, for example – in our own Solar System.”

Co-author Dr Michele Bannister, also from QUB, commented: “We’ve discovered that this is a planetesimal with a well-baked crust that looks a lot like the tiniest worlds in the outer regions of our Solar System, has a greyish/red surface and is highly elongated, probably about the size and shape of the Gherkin skyscraper in London.

“It’s fascinating that the first interstellar object discovered looks so much like a tiny world from our own home system. This suggests that the way our planets and asteroids formed has a lot of kinship to the systems around other stars.”

A number of ideas have been discussed to explain the unusual shape of ‘Oumuamua. These include the possibility that it could be composed of separate objects that joined together, that a collision between two bodies with molten cores ejected rock that then froze in an elongated shape, and that it is a shard of a bigger object destroyed in a supernova.

In a paper recently published on the Arxiv pre-print server, Gábor Domokos, from the Budapest University of Technology in Hungary, and colleagues suggest that, over millions of years, collisions between ‘Oumuamua and many speeding interstellar dust grains could produce the object’s observed shape.

Prof Fitzsimmons said this idea was very interesting, and added: “I think what we’re looking at here is the initial flurry of scientists running around saying: ‘How did it get like this, where’s it come from, what’s it made of.’ It’s incredibly exciting.

“I think after a few months you will see people focus down on one or two possibilities for all these things. But this just shows you: it’s a symptom of what an amazing, interesting object this is… we can’t wait for the next one.”

If planets form around other stars the same way they did in the Solar System, many objects the size of ‘Oumuamua should get slung out into space. The interstellar visitor may provide the first evidence of that process.

“All the data we have at the moment turn out to be consistent with what we might expect from an object ejected by another star,” he said.

But asked about Breakthrough Listen’s initiative, he said: “If I had a radio telescope, I might give it a go.”

http://www.bbc.com/news/science-environment-42397398

By Emily Underwood

Viewed under a microscope, your tongue is an alien landscape, studded by fringed and bumpy buds that sense five basic tastes: salty, sour, sweet, bitter, and umami. But mammalian taste buds may have an additional sixth sense—for water, a new study suggests. The finding could help explain how animals can tell water from other fluids, and it adds new fodder to a centuries-old debate: Does water have a taste of its own, or is it a mere vehicle for other flavors?

Ever since antiquity, philosophers have claimed that water has no flavor. Even Aristotle referred to it as “tasteless” around 330 B.C.E. But insects and amphibians have water-sensing nerve cells, and there is growing evidence of similar cells in mammals, says Patricia Di Lorenzo, a behavioral neuroscientist at the State University of New York in Binghamton. A few recent brain scan studies also suggest that a region of human cortex responds specifically to water, she says. Still, critics argue that any perceived flavor is just the after-effect of whatever we tasted earlier, such as the sweetness of water after we eat salty food.

“Almost nothing is known” about the molecular and cellular mechanism by which water is detected in the mouth and throat, and the neural pathway by which that signal is transmitted to the brain, says Zachary Knight, a neuroscientist at the University of California, San Francisco. In previous studies, Knight and other researchers have found distinct populations of neurons within a region of the brain called the hypothalamus that can trigger thirst and signal when an animal should start and stop drinking. But the brain must receive information about water from the mouth and tongue, because animals stop drinking long before signals from the gut or blood could tell the brain that the body has been replenished, he says.

In an attempt to settle the debate, Yuki Oka, a neuroscientist at the California Institute of Technology in Pasadena, and colleagues searched for water-sensing taste receptor cells (TRCs) in the mouse tongue. They used genetic knockout mice to look for the cells, silencing different types of TRCs, then flushing the rodents’ mouths with water to see which cells responded. “The most surprising part of the project” was that the well-known, acid-sensing, sour TRCs fired vigorously when exposed to water, Oka says. When given the option of drinking either water or a clear, tasteless, synthetic silicone oil, rodents lacking sour TRCs took longer to choose water, suggesting the cells help to distinguish water from other fluids.

Next, the team tested whether artificially activating the cells, using a technique called optogenetics, could drive the mice to drink water. They bred mice to express light-sensitive proteins in their acid-sensing TRCs, which make the cells fire in response to light from a laser. After training the mice to drink water from a spout, the team replaced the water with an optic fiber that shone blue light on their tongues. When the mice “drank” the blue light, they acted as though they were tasting water, Oka says. Some thirsty mice licked the light spout as many as 2000 times every 10 minutes, the team reports this week in Nature Neuroscience.

The rodents never learned that the light was just an illusion, but kept drinking long after mice drinking actual water would. That suggests that although signals from TRCs in the tongue can trigger drinking, they don’t play a role in telling the brain when to stop, Oka says.

More research is needed to precisely determine how the acid-sensing taste buds respond to water, and what the mice experience when they do, Oka says. But he suspects that when water washes out saliva—a salty, acidic mucus—it changes the pH within the cells, making them more likely to fire.

The notion that one of the ways animals detect water is by the removal of saliva “makes a lot of sense,” Knight says. But it is still only one of many likely routes for sensing water, including temperature and pressure, he adds.

The “well-designed, intriguing” study also speaks to a long-standing debate over the nature of taste, Di Lorenzo says. When you find a counterexample to the dominant view that there are only five basic taste groups, she says, “it tells you you need to go back to the drawing board.”

http://www.sciencemag.org/news/2017/05/scientists-discover-sixth-sense-tongue-water

by David Z. Morris

A new device, developed by researchers at UC Berkeley and MIT, promises to bring clean drinking water to remote areas by drawing it directly from the air. Though the device is currently only a prototype, its early results appear extremely promising.

The device, which calls to mind the “moisture vaporators” Luke Skywalker oversaw in his youth, was developed in collaboration between chemist Omar Yaghi and mechanical engineer Evelyn Wang. It relies on a special material combining zirconium and adipic acid into what’s known as a metal-organic framework. At night, the material collects water molecules from the air. Then, during the day, sunlight causes it to release the water into a condenser.

In early tests, the device has been able to produce nearly three liters of water over 12 hours for every kilogram of the zirconium-acid material, even in very dry regions. Speaking to Science, an expert not involved in the project called the results “a significant proof of concept.”

There is one obstacle to wide deployment of the devices—the high cost of the key zirconium material. But the researchers say they’ve already had some success using cheaper aluminum instead.

Yaghi says the device would allow for taking water supplies “off-grid.” That invites a comparison to the global spread of cell phones, which, by circumventing the need to lay expensive wires, have proven more accessible in developing nations than wired phones. Their spread has had profound effects on global agriculture, education, and governance.

But the impact of a device that produces drinkable clean water, without the need for expensive pipes, filtration facilities, or even power, could be even bigger. According to the World Health Organization, 1 in 10 people worldwide lack access to clean water, and 88% of all disease in the developing world has been estimated to be caused by unsafe drinking water. For lack of water, millions die each year of cholera, malaria, diarrhea, and malnutrition. Not surprisingly, a 2009 study found that GDP growth correlated strongly with access to clean water.

Issues of water access aren’t limited to developing nations, either. Even in the U.S., clean, safe water has been a hot button issue at the center of outrage over lead contamination in Flint, Michigan and other cities and concerns over California’s drought woes. Fears the Missouri River could be contaminated by a leak from the Dakota Access Pipeline inspired the protest slogan “water is life.”

http://fortune.com/2017/04/16/drinking-water-technology/

Peña Blanca is a small agricultural community 300 km north of Santiago.

In this arid coastal region, ‘fog catchers’ — large nets strung up in areas with thick fog and high winds — are used to collect water.

The technique was pioneered in Chile in the 1950s. The fog is pushed through fine mesh where it condenses, trickles down, and gets collected below. It’s a cheap, effective, and clean way to source water.

The nets harvest precious water for crops and animals: 140 square meters provide 840 liters of water per day, shared among 85 landowners.

“Water shortage is a worldwide problem and we are not oblivious to it,” says Daniel Rojas, community leader. “It rains less and less, there is a lack of vegetation, fewer crops and people are affected in every sense. But here we have a natural resource that wasn’t being exploited.”

The ‘camanchaca’ is a thick coastal fog which rolls in most days. It blocks the sun, but the low visibility and wind is welcomed by the locals.

The Dar Si Hmad project in Morocco is significantly bigger, and uses next generation technology. The water collected here is clean enough to drink. And there are plans to use newer nets which are more efficient, doubling the amount of water they currently collect.

“They call me the fog queen,” laughs Dr Jamila Bargach.

She has good reason to smile. As director of the world’s largest fog catching project, she picked up an award at the 2016 UN climate conference in Marrakech for the work carried out by her women-led NGO.

“Our new nets have a mean average of 22 liters per square meter, which will service about 1,300 people, about 13 villages,” she says.

The fog catchers have changed the lives of women in the Sahara, who previously scheduled their days around the chore of fetching and carrying water for their families.

“The average time is 3 hours per day to get your basic 30 liters. This is becoming even more difficult because you have to walk further with the consequences of climate change: desertification and the rising temperatures,” says Dr Bargach.

“So where there’s fog, we can harness it for the community, store it when it’s needed, and then use it later, instead of looking for very expensive and fossil-based solutions like desalinizing water, or digging more bore holes, looking for even deeper aquifers.”

As with any project, it needs to be economically viable. And that’s one of the reasons Dar Si Hmad charges for its water.

“We do charge for the water, otherwise how will we keep up with the maintenance? We have aligned the prices with government prices, and we have taken 20 percent off, because we’re dealing with very poor communities. But let me tell you one thing. Even with water, the moment it becomes free, it will lose its value.”

In Chile the economic opportunities are a little different. Peña Blanca now boasts an award-winning ale from the Atrapaniebla brewery.

Marcos Carcuro and his brother have their own nets alongside those belonging to the village.

“At first they told us it was a crazy idea to brew beer from clouds”, says Carcuro. “But later, seeing the results of our first prototypes, we realized that it was going to be a better product than those made with regular water.”

Where the weather suits, and when maintenance costs are met, fog catchers provide a lifeline in vulnerable communities across the world. From Chile to Morocco, it’s a proven sustainable and scalable solution to water scarcity.

http://www.cnn.com/2016/12/28/world/eco-solutions-fog-catchers/index.html

By Helen Thomson

“When the tide came in, these kids started swimming. But not like I had seen before. They were more underwater than above water, they had their eyes wide open – they were like little dolphins.”

Deep in the island archipelagos on the Andaman Sea, and along the west coast of Thailand live small tribes called the Moken people, also known as sea-nomads. Their children spend much of their day in the sea, diving for food. They are uniquely adapted to this job – because they can see underwater. And it turns out that with a little practice, their unique vision might be accessible to any young person.

In 1999, Anna Gislen at the University of Lund, in Sweden was investigating different aspects of vision, when a colleague suggested that she might be interested in studying the unique characteristics of the Moken tribe. “I’d been sitting in a dark lab for three months, so I thought, ‘yeah, why not go to Asia instead’,” says Gislen.

Gislen and her six-year old daughter travelled to Thailand and integrated themselves within the Moken communities, who mostly lived on houses sat upon poles. When the tide came in, the Moken children splashed around in the water, diving down to pick up food that lay metres below what Gislen or her daughter could see. “They had their eyes wide open, fishing for clams, shells and sea cucumbers, with no problem at all,” she says.

Gislen set up an experiment to test just how good the children’s underwater vision really was. The kids were excited about joining in, says Gislen, “they thought it was just a fun game.”

The kids had to dive underwater and place their heads onto a panel. From there they could see a card displaying either vertical or horizontal lines. Once they had stared at the card, they came back to the surface to report which direction the lines travelled. Each time they dived down, the lines would get thinner, making the task harder. It turned out that the Moken children were able to see twice as well as European children who performed the same experiment at a later date.

What was going on? To see clearly above land, you need to be able to refract light that enters the eye onto the retina. The retina sits at the back of the eye and contains specialised cells, which convert the light signals into electrical signals that the brain interprets as images.

Light is refracted when it enters the human eye because the outer cornea contains water, which makes it slightly denser than the air outside the eye. An internal lens refracts the light even further.

When the eye is immersed in water, which has about the same density as the cornea, we lose the refractive power of the cornea, which is why the image becomes severely blurred.

Gislen figured that in order for the Moken children to see clearly underwater, they must have either picked up some adaption that fundamentally changed the way their eyes worked, or they had learned to use their eyes differently under water.

She thought the first theory was unlikely, because a fundamental change to the eye would probably mean the kids wouldn’t be able to see well above water. A simple eye test proved this to be true – the Moken children could see just as well above water as European children of a similar age.

It had to be some kind of manipulation of the eye itself, thought Gislen. There are two ways in which you can theoretically improve your vision underwater. You can change the shape of the lens – which is called accommodation – or you can make the pupil smaller, thereby increasing the depth of field.

Their pupil size was easy to measure – and revealed that they can constrict their pupils to the maximum known limit of human performance. But this alone couldn’t fully explain the degree to which their sight improved. This led Gislen to believe that accommodation of the lens was also involved.

“We had to make a mathematical calculation to work out how much the lens was accommodating in order for them to see as far as they could,” says Gislen. This showed that the children had to be able to accommodate to a far greater degree than you would expect to see underwater.

“Normally when you go underwater, everything is so blurry that the eye doesn’t even try to accommodate, it’s not a normal reflex,” says Gislen. “But the Moken children are able to do both – they can make their pupils smaller and change their lens shape. Seals and dolphins have a similar adaptation.”

Gislen was able to test a few Moken adults in the same way. They showed no unusual underwater vision or accommodation – perhaps explaining why the adults in the tribe caught most of their food by spear fishing above the surface. “When we age, our lenses become less flexible, so it makes sense that the adults lose the ability to accommodate underwater,” says Gislen.

Gislen wondered whether the Moken children had a genetic anomaly to thank for their ability to see underwater or whether it was just down to practice. To find out, she asked a group of European children on holiday in Thailand, and a group of children in Sweden to take part in training sessions, in which they dived underwater and tried to work out the direction of lines on a card. After 11 sessions across one month, both groups had attained the same underwater acuity as the Moken children.

“It was different for each child, but at some point their vision would just suddenly improve,” says Gislen. “I asked them whether they were doing anything different and they said, ‘No, I can just see better now’.”

She did notice, however, that the European kids would experience red eyes, irritated by the salt in the water, whereas the Moken children appeared to have no such problem. “So perhaps there is some adaptation there that allows them to dive down 30 times without any irritation,” she says.

Gislen recently returned to Thailand to visit the Moken tribes, but things had changed dramatically. In 2004, a tsunami created by a giant earthquake within the Indian Ocean destroyed much of the Moken’s homeland. Since then, the Thai government has worked hard to move them onto the land, building homes that are further inland and employing members of the tribe to work in the National Park. “It’s difficult,” says Gislen. “You want to help keep people safe and give them the best parts of modern culture, but in doing so they lose their own culture.”

In unpublished work, Gislen tested the same kids that were in her original experiment. The Moken children, now in their late teens, were still able to see clearly underwater. She wasn’t able to test many adults as they were too shy, but she is certain that they would have lost the ability to see underwater as they got older. “The adult eye just isn’t capable of that amount of accommodation,” she says.

Unfortunately, the children in Gislen’s experiments may be the last of the tribe to possess the ability to see so clearly underwater. “They just don’t spend as much time in the sea anymore,” she says, “so I doubt that any of the children that grow up these days in the tribe have this extraordinary vision.”

http://www.bbc.com/future/story/20160229-the-sea-nomad-children-who-see-like-dolphins


Scientists have successfully developed a method of producing electricity from seawater, with help from the Sun. Instead of harvesting hydrogen, the new photoelectrochemical cell produces hydrogen peroxide for electricity.

Researchers at Osaka University found a way to turn seawater—one of the most abundant resources on Earth—into hydrogen peroxide (H2O2) using sunlight, which can then be used to generate electricity in fuel cells. This adds to the ever growing number of existing alternative energy options as the world continues to move towards green energy.

“Utilization of solar energy as a primary energy source has been strongly demanded to reduce emissions of harmful and/or greenhouse gases produced by burning fossil fuels. However, large fluctuation of solar energy depending on the length of the daytime is a serious problem. To utilize solar energy in the night time, solar energy should be stored in the form of chemical energy and used as a fuel to produce electricity,” the researchers wrote in their paper.

Previous technologies focused on splitting the molecules of pure water to harvest hydrogen.

As previously mentioned, the new research, instead of harvesting hydrogen from pure water, turns seawater into hydrogen peroxide. Gaseous hydrogen production from pure water has a lower solar energy conversion and is much harder to store, whereas the team notes, “H2O2 can be produced as an aqueous solution from water and O2 in the air.”

It is also much easier and safer to store and transport in higher densities, compared to highly compressed hydrogen gas.

There are other methods of producing H2O2, but they are impractical in that the processes themselves require a lot of energy, essentially defeating the purpose. This is the first time someone developed a photocatalytic method efficient enough to make H2O2 use in fuel cells viable.

The process involves a new photoelectrochemical cell developed to produce H2O2 when sunlight illuminates the photocatalyst, which then absorbs photons and initiates chemical reactions with the energy, resulting in H2O2.

A test conducted for 24 hours shows that the H2O2 concentration in seawater reached about 48mM (millimolar), compared to 2mM in pure water. Researchers found that this was made possible by seawater’s negatively charged chlorine enhancing the photocatalysis.

That said, this method isn’t yet as good as other solar power processes, but it’s a start. Researchers aim to improve efficiency with better materials and lower costs.

“In the future, we plan to work on developing a method for the low-cost, large-scale production of H2O2 from seawater,” Fukuzumi said. “This may replace the current high-cost production of H2O2 from H2 (from mainly natural gas) and O2.”

http://futurism.com/theres-a-new-way-to-generate-power-using-seawater/