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June 30, 2011

Let's Talk Water, Part 2

In the first segment of this 3-part series, I discussed some of the reasons that there is likely to be a shortage of fresh water in the decades ahead and some of the challenges that could emerge should that occur. The Economist summed up the challenges this way:

"The difficulties start with the sheer number of people using the stuff. When, 60 years ago, the world's population was about 2.5 billion, worries about water supply affected relatively few people. Both drought and hunger existed, as they have throughout history, but most people could be fed without irrigated farming. Then the green revolution, in an inspired combination of new crop breeds, fertilisers and water, made possible a huge rise in the population. The number of people on Earth rose to 6 billion in 2000, nearly 7 billion today, and is heading for 9 billion in 2050. The area under irrigation has doubled and the amount of water drawn for farming has tripled. The proportion of people living in countries chronically short of water, which stood at 8% (500m) at the turn of the 21st century, is set to rise to 45% (4 billion) by 2050. And already 1 billion people go to bed hungry each night, partly for lack of water to grow food." ["For want of a drink," 20 May 2010]

In this post, I'll discuss a number of innovations that have been developed to help meet the challenge of providing potable water for humans and/or useable water for agriculture and manufacturing. Ben Coxworth provides a good introduction to the subject in an article about The Fraunhofer research organization. ["Every last drop: technologies that save water on show," Gizmag, 13 September 2010] He writes, "14 of Fraunhofer's research divisions have joined together to form the Fraunhofer Alliance SysWasser, with the aim of developing sustainable water system technologies." The technologies include: harvesting water from the air; computer-guided water management; leak repair; improved sewage sanitation; more cost-effective polluted water disposal; and increased energy production from sewage processing. He begins:

Obtaining drinking water from humidity in the air

"There's already talk of harvesting electricity from the air, so why not water, too? Fraunhofer has developed a system in which a humidity-absorbing brine (salt water) solution runs down the surface of a tower-shaped structure. That brine is then pumped via a natural vacuum effect into a tank where it is heated by solar collectors, causing the absorbed humidity to evaporate out and condense in an area where it can be collected. The system is energy self-sufficient, so it could be set up in regions where there is no electrical infrastructure."

Coxworth doesn't indicate how much water such a system can produce, but it doesn't sound practical for large agricultural use. In another article, Coxworth reports on a different system designed to harvest fog. ["Namib Beetle inspires new 'fog harvesting' research," Gizmag, 26 April 2011] He explains:

"For years, people living in high-altitude or coastal arid countries have been collecting drinking water by harvesting fog. More specifically, they've mounted pieces of fine netting over top of containers, left the setup overnight, then collected the fog droplets that got caught in the net and rolled down its fibers into the container. While it might sound like a rather insubstantial way of acquiring water, under the right conditions it can yield a surprisingly large amount of liquid. Now, a chemical engineering graduate student from the Massachusetts Institute of Technology (MIT) is looking to improve on the technique. Shreerang Chhatre was inspired by the Namib Beetle, an insect that collects water droplets on bumps on its back, then drinks them when they roll down to its mouth. His 'fog harvesters,' like those created by other scientists, use a mesh panel in place of a net. Even solid materials such as plastic sheeting will work, although they can create wind currents that carry some of the moisture away."

Like the Fraunhofer system, the fog harvester is more useful for producing potable water for human consumption than for producing the large quantities of water needed for agriculture. Coxworth indicates that the MIT fog harvester has been able to collect up to "one liter (about a quart) of water per meter of mesh, per day." Although that may sound significant, the UN suggests that each person needs 20-50 liters of safe freshwater a day to ensure their basic needs for drinking, cooking and cleaning. Coxworth indicates that "Chhatre is trying to boost that output by refining the materials that the mesh is made from, attempting to strike a balance between hydrophilic materials that attract water droplets, and hydrophobic materials that then send them on their way down into the collection container." The biggest challenge, however, is not a technical one but an economic one -- "most of the potential users likely couldn't afford such a device." I suspect that the Fraunhofer system faces a similar challenge. The next two Fraunhofer systems discussed by Coxworth are intended for more developed areas and involve the use of computers and physical inspections to look for one of the main causes of wasted water -- leaks.

Managing drinking water systems by computer

"Using HydroDyn, its water management program, Fraunhofer says that municipalities could identify and locate leaks in their water systems. The system creates a computer model of an existing water system, and compares the output figures of that idealized system with the real figures. HydroDyn is reportedly already in use in Mongolia, Libya, Saudi Arabia and several German cities."

Finding leaks

"A system like HydroDyn might tell you the approximate location of a leak, but intelligent probes that physically inspect lines from the inside will actually show it to you. Another option for pinpointing leaks is to use long-range ultrasound waves."

If you don't believe that finding and plugging leaks is important, you should know that the United Nations estimates that between 66-132 billion gallons of drinking water leaks from the supply systems in many mega cities each year. That is water that will be desperately needed in the years ahead. The final subject discussed by Coxworth is waste water. The United Nations points out that "Urban waste has value in terms of energy, agriculture and industry. Its collection and reuse can have economic and social benefit, protect the environment (especially downstream users) and improve health." ["Water for cities: responding to the urban water challenge," United Nations, 2011] Coxworth writes:

Cleaning sewage water with diamonds

"Fraunhofer has demonstrated that when diamond-coated electrodes are placed in the water, hydroxyl radicals will form on them and proceed to oxidize all water-borne substances containing carbon. According to the research group, this means that everything from solvents to bacteria to pesticides will be neutralized, leaving behind only harmless salts and carbon dioxide."

More cost-effective disposal

"When industries generate highly-polluted water, they have to pay to get it properly disposed of as hazardous waste. Needless to say, many such industries decide it would be cheaper just to sneak it into the closest river or ocean. In an effort to keep disposal fees down, Fraunhofer has devised a 'low-cost' modular vacuum evaporation process, which concentrates more pollutants in less water – companies are still getting rid of the same amount of nasty stuff, but aren't paying for the disposal of all the water that previously would have accompanied it."

Increased yields of biogas from sewage sludge

"Fraunhofer has developed a system for decreasing the volume and mass of sludge, wherein it's treated with ultrasound and then mechanically disintegrated. The process results in more biogas production, and less solid waste. A number of sewage treatment plants are already using this technology."

For more on the subject of treating sewage and waste water, read my posts entitled Sewage and Cleantech and Tomorrow's Toilets. The United Nations notes that in the developing world, over a billion people cannot get clean drinking water. It estimates that dirty and contaminated water causes 80 percent of diseases in underdeveloped areas and kills nearly 10 million people annually. For those individuals, being able to purify available water would literally be a life saver. In another article, Coxworth reports that seeds from the Moringa oleifera tree might be the answer to their prayers. ["Tree seeds could provide low-cost water purification for developing nations," Gizmag, 7 March 2010] He writes:

"What many people don't realize ... is that there are already naturally-occurring water filtration supplies available in many of these areas. They come in the form of seeds from the Moringa oleifera tree, and used properly, they can produce a 90.00 to 99.99% bacterial reduction in previously untreated water. The drought-resistant Moringa has been described as the 'world’s most useful tree', as it produces cooking and lighting oil, soil fertilizer, and highly-nutritious food in the form of its pods, leaves, seeds and flowers. It is grown in Africa, India, South East Asia and Central and South America - all places that lack sufficient potable water. It has been known for some time that its seeds can also be used to purify water, although that knowledge has never been widely disseminated, even amongst the locals. ...The purification process involves grinding Moringa seeds into a paste, mixing that paste with untreated water, waiting for the paste particles to bind with the impurities and settle to the bottom, and then decanting or siphoning the pure water off the top. The entire process is actually quite involved, so the resultant drinkable water would still be a pretty precious commodity."

Although Coxworth calls the potential reduction of disease that could result from widespread use of this process "an amazing prospect," the fact of the matter is that unless a less involved process is found for purifying water, things aren't likely to change. It's just human nature. The Economist reports that Professor "Yi Cui of Stanford University thinks he has come up with one." ["Silver threads of life," 21 October 2010] The article continues:

"Traditional filters work by forcing water through pores to weed out bacteria. That needs power, as well as frequent changes of the filter element as the pores fill up with bugs. Dr Cui's filter, though, does not screen the bacteria out. It kills them. The filter element he and his team have designed is a mesh of tiny carbon cylinders, known as nanotubes, and silver wires laid on top of a thin strip of cotton cloth. Silver is well known to kill bacteria, so Dr Cui conjectured that forcing bugs to pass close to the metal without actually trapping them might lead to their destruction. He also suspected that running an electric current through the silver might help the process, because electrical fields have the ability to break down the membranes that surround bacterial cells. Though silver is a good conductor, carbon is cheaper, and the nanotubes provide the extra electrical conductivity needed."

It turns out that Cui was correct, "when the filter was operated at -20 volts it killed 89% of the bacteria and that at +20 volts it killed 77%. At zero volts, most of the bacteria survived. In a follow-up experiment, in which contaminated water was run through three of the new filters in sequence, 98% of the bacteria were killed." The article surmises that the inclusion of silver would seem to make the filter cost prohibitive; however, since "the amount involved is minuscule, as is the quantity of electricity needed to keep the filter charged (a small solar panel would be sufficient to supply it)," the filters may be the life saver for which the developed world has been looking. As an added bonus, "the filter itself would be expected to last indefinitely."

Academics -- be they professors, like Cui, or graduate students, like Chhatre -- are involved in a number projects they hope will make access to clean water easier and cheaper. Here are a few examples:

Bicycle-powered Water Pump

"University of Sheffield student Jon Leary was required to 'make something useful out of rubbish' as part of his dissertation." He ended up making "a mobile bicycle-powered water pump" from "cast-off bicycles and discarded pumps." He taught Guatemalan farmers how to build them so that they "can irrigate their land much more easily and effectively than ever before." ["Student invention lets Guatemalans pump water on the go," Ben Coxworth, Gizmag, 1 June 2010]

Safe Water Tester

"The worldwide shortage of clean drinking water is a serious problem, although in many cases there's a relatively simple solution – just leave the tainted water outside in clear plastic bottles, and let the sun's heat and ultraviolet rays purify it. This approach is known as SODIS (SOlar DISinfection of water in plastic bottles), and it removes 99.9 percent of bacteria and viruses – results similar to those obtained by chlorine. Unfortunately, however, there's been no reliable way of knowing when the water has reached a safe level of purity. Now, four engineering students from the University of Washington have created a simple, inexpensive device that does just that. ... The students, Chin Jung Cheng, Charlie Matlack, Penny Huang and Jacqueline Linnes, developed a simple device using parts from a keychain that blinks when exposed to light. When attached to a water bottle, it monitors how much light is passing through the water. An indicator light blinks on and off as long as particulates are still obstructing the light flow, and stops blinking once the water is safe to drink. It is also able to tell when a bottle of water is present in front of it, so it's not trying to measure data when nothing's there. It is estimated that parts for each device would cost about US$3.40, although bulk buying should push that figure even lower." ["Students design electronic device that indicates safe drinking water," by Ben Coxworth, Gizmag, 24 December 2010]

The final project I'll discuss is a more sophisticated version of the "clear water bottle" solution discussed above. It's called the Solarball and was designed by Industrial Design student Jonathan Liow.

"After hearing about the need for cheap and effective water purification in Africa, he proceeded to create the Solarball for his graduate project at Australia's Monash University. The ball is reportedly capable of producing 3 liters (about 3 quarts) of drinkable water per day, using nothing but polluted water and sunlight. Users start by pouring dirty water into the Solarball. That water proceeds to get heated by the Sun's rays, which shine in from 360 degrees through the ball's transparent upper section. Condensation forms on the inside of the ball, and is guided down to a spout via an internal gutter that runs around its diameter. What comes out is pure, clean water, as the contaminants are left behind in the unevaporated water." ["Student-designed Solarball creates drinkable water," by Ben Coxworth, Gizmag, 30 March 2011]

While many of the solutions discussed above help provide potable water for human consumption, they can't enough clean water to meet the needs of agriculture and industry. The world, however, must be fed and useful products must be manufactured. Where is that water going to come from? Obviously the most abundant source of water on the planet is the world's oceans. To be useful, however, that water must have the salt removed from it. Advancements in how that can be done will be the topic of the final segment of this 3-part series.


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