Let’s Talk Water, Part 3

Stephen DeAngelis

July 1, 2011

In the first segment of this 3-part series, I discussed some of the challenges that are going to be confronted as freshwater becomes more scarce (either because supplies dry up or the amount needed increases). In the second segment, I discussed some of the innovations that have been developed to help meet the challenge of providing potable water for humans and/or useable water for agriculture and manufacturing. In this final segment, I’d like to discuss some recent innovations involving desalination. I first discussed this subject back in 2008 in a post entitled The Future of Desalination. Desalination is going to become more important as glaciers melt and oceans rise. Since 97% of the world’s water is found in oceans, making that water useful for personal and commercial use is critical. The Economist states, “Unless some breakthrough occurs in getting the salt out of sea water, the best hope of a happy marriage between supply and demand comes from much greater restraint among water-users.” [“A glass half empty,” 20 May 2010] By “breakthrough,” I believe the magazine means an innovation that can get the salt out of sea water much more cheaply than it can be currently done. Current systems cost around $1.50 to produce 264 gallons (1 cubic meter) of fresh water.” Commercial desalination is usually done in one of two ways. The first, known as thermal desalination, involves boiling seawater above 212F, then distilling the vapors. The second, called reverse osmosis, uses hydraulic pressure to force water through a membrane that filters out salt.” [“Innovator: Robert McGinnis of Oasys Water,” by Caroline Winter, Bloomberg BusinessWeek, 10 March 2011]

 

Two things are generally included in any discussion about reverse osmosis desalination: first, the amount of power that is required for the process; and, second, the construction of membranes used in the process. One of the winners of The Wall Street Journal‘s 2010 Innovation Awards, NanoH2O Inc., based in El Segundo, CA, was singled out for its contribution “in the environment category for a nanotechnology-based reverse-osmosis membrane that promises to reduce the cost of running a typical desalination plant by as much as 25%.” [“The Wall Street Journal 2010 Technology Innovation Awards,” by John M. Leger, 27 September 2010] Leger reports:

“Reverse osmosis, which separates salt and other impurities from salt water by forcing it through a membrane at high pressure, is increasingly favored as a desalination technology. But the pumps that push water through the membranes consume large amounts of energy, and traditional membranes easily are clogged by impurities, reducing their efficiency. NanoH2O, using technology based on research at the University of California, Los Angeles, weaves nanoparticles into its membranes. The nanoparticles are more permeable to water molecules than the material in traditional membranes, and they resist fouling by bacteria, salt and other contaminants. As a result, the company says, its membranes enable desalination plants to maintain the same levels of production while reducing energy consumption, or to produce 70% more fresh water at current energy levels. The company says it has begun producing membranes and complete reverse-osmosis modules, which incorporate the membranes and can replace the filters already used in existing desalination plants. It delivered the first products in August.”

You have to admit that increasing the production of fresh water by 70% without increasing energy consumption is pretty impressive. IBM is also using nanotechnology to produce a better membrane. [“IBM’s solar-powered desalination plant to hydrate the Saudi desert,” by Jeff Salton, Gizmag, 8 April 2010] IBM believes that the combination of solar power and improved membrane technology does constitute a “breakthrough” in desalination. Salton reports:

“A new, energy-efficient desalination plant with an expected production capacity of 30,000 cubic meters per day will be built in the city of Al Khafji, Saudi Arabia, to serve its 100,000 people. Known more for its computers, IBM has joined forces with KACST (King Abdulaziz City for Science and Technology) to build the plant that will be powered by ultra-high concentrator photovoltaic (UHCPV) technology – a system with a concentration greater than 1,500 suns. … The IBM-KACST team is also working to improve nanomembrane technology that filters out salts as well as potentially harmful toxins in water while using less energy than other forms of water purification. The organizations say that by combining solar power with the new nanomembrane, they will be able to significantly reduce the cost of desalinating seawater at these plants.”

Because Saudi Arabia is basically a desert, it has become the world’s largest producer of desalinated water. If the Saudi desert is to blossom like a rose, it will need to produce even more water. “IBM says that the Saudi’s goal is to ramp up the number of desalination plants in order to provide fresh water for one million people in the coming years.” According to Salton, “The IBM and Saudi researchers … started work on a pilot plant utilizing the technology [in 2010] with a view to eventually providing an economical means of producing clean water in parts of the world where it is needed.” For more on IBM’s work, watch the attached video.

 

 

Scientists from the UCLA Henry Samueli School of Engineering and Applied Science have joined the search for a better membrane to use in the desalination process [“New reverse-osmosis membrane to improve desalination,” by Darren Quick, Gizmag, 6 April 2011]. Quick reports:

“Most of the new [desalination] facilities make use of reverse osmosis technology, but unfortunately these systems are susceptible to clogging and membrane damage, which places higher energy demands on the pumping system and necessitates costly cleanup and membrane replacement. Now researchers have unveiled a new class of reverse-osmosis membrane that resists the clogging that typically occurs when seawater, brackish water and waste-water are purified. … The new membrane developed by researchers from the UCLA Henry Samueli School of Engineering and Applied Science has a novel surface topography and chemistry that allow it to avoid such drawbacks. The highly permeable, surface-structured membrane can easily be incorporated into today’s commercial production system, the researchers say, and could help to significantly reduce desalination operating costs. Synthesized through a three-step process the researchers created a polymer ‘brush layer’ on a polyamide surface. The polymer chains of the tethered brush layer are in constant motion with water flow adding to the brush layer’s movement, making it extremely difficult for bacteria and other colloidal matter to anchor to the surface of the membrane. … Another factor in preventing adhesion is the surface charge of the membrane. [The UCLA] team is able to choose the chemistry of the brush layer to impart the desired surface charge, enabling the membrane to repel molecules of an opposite charge.”

In the article referenced above by Caroline Winter, she profiles another company, Oasys Water, started by Robert McGinnis, a former Navy Underwater Demolition Team (UDT) member who, as an undergraduate, majored in theater and wrote science-fiction “think-piece mini-epics.” McGinnis claims to have invented “a [combination forward osmosis/thermal] desalination method 10 times more efficient than alternatives.” Winter continues:

“Water molecules naturally want to flow from fresher solutions to saltier ones. Hence the ‘reverse’ in reverse osmosis: It forces water molecules to go against their tendency. McGinnis’s method makes use of forward osmosis. He’s developed a ‘draw solution’ that’s saltier than seawater. Without need for any energy, the water molecules in seawater flow across a porous membrane and into the draw solution, leaving the sea salt behind. McGinnis’s solution is as undrinkable as ocean water, but its salt compounds—’essentially just ammonium, carbon dioxide, and some other secret stuff,’ he says—vaporize at lower temperatures. McGinnis’s solution needs only 122F to burn off salts and leave behind pure water, instead of the much higher temperatures required for thermal desalination.”

McGinnis graduated from a couple of years ago with an environmental engineering degree and “co-founded Boston-based Oasys Water and raised $10 million from three venture capital firms to commercialize the technology, including developing a thin membrane suitable for forward osmosis.” Plants that use the process have yet to be built, but “Oasys plans to start taking orders in late 2011.” Analysts believe that Oasys has landed on a winner. You have to agree that an exponential increase in efficiency is pretty remarkable.

 

Obviously, researchers are continuing to explore ways of improving the desalination process and bringing down costs. Since much of the world’s population lives along coastal areas, any breakthroughs in this area will have significant impact in the decades ahead — that is, if a country has the necessary resources to build large plants. Researchers at MIT believe they have come up with a solution for people living in developing areas that have insufficient resources to build large desalination plants [“MIT develops solar-powered, portable desalination system,” by Dario Borghino, Gizmag, 27 October 2010]. Borghino reports:

“Researchers from MIT’s Field and Space Robotics Laboratory (FSRL) have designed a portable, solar-powered desalination system that is cost-effective and easy to assemble to bring drinkable water in disaster zones and remote regions around the globe. Relief efforts in the aftermath of large-scale natural disasters often call for water as one of the very first priorities: such was the case in the Haiti earthquake back in January. When coping with disasters of this scale the possibility to obtain drinkable water locally, such as by desalination of sea water, dramatically improves the effectiveness of the rescue efforts. Desalination systems, however, are usually quite large and need a lot of energy to operate; these situations, instead, call for a quick, effective way to turn seawater into drinkable water in loco, with a small and portable system that doesn’t need external sources of electrical power to work. The system developed by MIT researchers does exactly this, and its characteristics make it particularly apt to the task of assisting people in emergency situations. It’s designed so it can be cost-effectively assembled from standard parts and put into operation within hours even without the need of technicians. Its specifics mean the apparatus could also found use in remote areas where supplying energy and clean water can be logistically complex, such as desert locations or small villages in developing countries. Photovoltaic panels power high-pressure pumps that push seawater through a filtering membrane. Unlike conventional solar-powered desalination systems that run on battery power when direct sunlight is not available, this system can operate efficiently even in cloudy conditions. Algorithms in the system’s computer can change variables such as the power of the pump or the position of the valves to maximize water output in response to changing weather and current water demand. As a result, the prototype can yield as many as 80 gallons of water a day in a variety of weather conditions while a larger version of the unit, which would only cost about US$8,000 to construct, could provide about 1,000 gallons of water per day. Because of its reduced dimensions, the team estimated that one C-130 cargo airplane could transport two dozen desalination units, enough to provide water for 10,000 people.”

Clearly, desalination will play an important role in supplying water for human needs as the population surpasses the 10 billion mark at the end of this century. As research in this area continues, I’m certain that the best ideas that emerge will eventually be combined into the “breakthrough” that The Economist indicates is required to meet the needs of a burgeoning population.