Water. Desalination + reuse
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RESEARCH February-March 2016 | Desalination & Water Reuse | 29 | Study dEmonStRAtES good vibRAtionS foR dESAlinAtion Researchers in Israel and China have reported how computer emulation findings suggest a novel nanotechnology-based strategy to improve water filtration. The research looked at minute vibrations of water-carrying carbon nanotubes called phonons which could enhance the diffusion of water through filters. The researchers showed how phonons could improve filtration efficiency using computers to simulate the flow of water molecules through nanotubes. The results have important implications for membrane desalination. According to Professor Michael Urbakh of the Tel Aviv University school of chemistry, phonons can triple the energy efficiency of water passage through filters used in water disinfection and reverse osmosis desalination "Water filtration systems require a lot of energy due to friction at the nano-level. With these oscillations, however, we witnessed three times the efficiency of water transport, and, of course, a great deal of energy saved, " Urbakh said. SAlt-tolERAnt bACtERiA Could End nEEd foR CoppER minE dESAlinAtion Researchers at Australia's national science agency, the Commonwealth Scientific and Industrial Research Organisation (CSIRO) claim to have found a means to end the need for desalinated water in a major copper mining process. The scientists have discovered a bacterium that can tolerate high salinity and acidic conditions which could be used to leach copper minerals from ore - a process that currently requires high volumes of fresh water. Some 5% of copper mined worldwide is mined using bacterial leaching from low-grade ore CSIRO environmental microbiologist, Suzy Rea, said fresh water was a major cost item in the mining industry. "In Chile, the biggest copper mine in the world is right next to the sea. So if we have found bacteria that can manage salty water, then they wouldn't have to either build desalination plants or transport water in, and that would save a lot of money and be useful environmentally too," she said. The salt-and-acid-tolerant bacteria were found in drains on farmland near Merredin and Beacon in Western Australia. It has yet to be shown to be capable of bioleaching copper but Rea said the bacteria had already been shown to withstand high sulphate concentrations – a prerequisite for the leaching process which is based on oxidation of sulphides to sulphates. RESEARCHERS Simplify oil And gAS wAStEwAtER tREAtmEnt Engineers at the University of Colorado Boulder have invented a process that they claim simplifies the treatment of oil and gas wastewater by simultaneously removing salts and organic contaminants while producing energy. The Colarado researchers have published a technique that uses a microbe-powered battery. "The beauty of the technology is that it tackles two different problems in one single system," said University of Colorado Boulder associate professor of environmental and sustainability engineering and senior author of the paper Zhiyong Jason Ren. "The problems become mutually beneficial in our system – they complement each other – and the process produces energy rather than just consumes it." The new technology - microbial capacitive desalination - exploits the energy-rich hydrocarbons in the wastewater by deploying microbes that consume them and release their energy. The energy is used to create a positively charged electrode on one side of a cell and a negatively charged electrode on the other, essentially setting up a battery. Lead author of the paper, Casey Forrestal, who is working to commercialize the technology said: "We use microbes to generate an electrical current that can then be used for desalination." Ren added: "Right now oil and gas companies have to spend energy to treat the wastewater. We are able to treat it without energy consumption; rather we extract energy out of it." Egypt RESEARCHERS unvEil nEw low-CoSt mEmbRAnE foR dESAlting Researchers at Alexandria University in Egypt have published what they claim to be a new low-cost-desalination technology that uses little energy and cheap membrane materials. The technology uses pervaporation – vaporization of permeate drawn through a membrane. The researchers developed a cellulose acetate membrane combined with other components, to filter particles and bind salts before permeate is vaporised using a heat source. The researchers, led by associate professor of agricultural and biosystems, Engineer Ahmed El-Shafei, said the system desalinated simulated seawater of "exceptionally high concentration" to produce a high flux of potable water with over 99.7% salt rejection. It used a once-through, purge-air pervaporation. In their report in Water Science and Technology, El-Shafei's team said the best result was at 70°C, where flux varied from 5.97 l/m²h at a sodium chloride concentration of 40 g/l, to 3.45 l/m²h for 40g/l. "The membrane we fabricated can easily be made in any laboratory using cheap ingredients, which makes it an excellent option for developing countries," said El-Shafei. RESEARCHERS' dESAlinAting gREEnHouSE uSES unExplAinEd bubblE pHySiCS Researchers at Murdoch University, Australia, have designed a small-scale greenhouse that deploys desalination technology based on an "unexplained" bubble formation phenomenon to bring food production to remote regions with high-salinity groundwater. The researchers claimed the so-called bubble greenhouse outstrips existing small-scale desalination technologies in its fresh water production capacity. It uses a novel humidification-dehumidification process powered by solar or wind generation. A regenerative blower pushes air through sinter discs in a six-chamber column evaporator filled with saline water. This creates thousands of fine bubbles that saturate with water to be released in a multi-stage condenser to collect fresh water to humidify the greenhouse Research team member, Mario Schmack, said the large air/water interface created by the fine bubble column was enhanced by the use of saline rather than freshwater in the humidification step. He said saline water maintained the air/water interface by inhibiting coalescence of the bubbles by "a still unexplained property." The researchers said a 150-m² greenhouse could produce up to 30 kg of crops daily while generating fresh desalinated water overnight. Schmack said simplicity was at the heart of the design, as desalination technologies such as reverse osmosis have proven untenable in remote areas due to their complicated nature. "The bubble greenhouse system relies on basic technology such as regenerative blowers and technically undemanding water pumps, so it's easy to implement and easy to maintain and repair by local people with limited technical means," Schmack said. The project was poised for scaling-up with industry partners.