Water. desalination + reuse

RESEARCH November-December 2014 | Desalination & Water Reuse | 39 | Russia's nuclear energy corporation, Rosatom, has formed a group of expert desalination advisors as part of a push to win customers for its thermal desalination technologies. The company was targeting world regions where clean water was scarce as a path to becoming "leaders in the global nuclear market," according to Rosatom. Following the Expert Council on Desalination's fi rst meeting, member and president of Russian nuclear research centre, the Kurchatov Institute, Evgeny Velikhov said: "Foreign customers are interested in getting the best, ready-made solution for water desalination with predictable fi nal product cost. The [council] will allow us to quickly and effi ciently develop such solutions for each client based on the specifi c needs." He said Russia had "unique competencies and historical experience in using nuclear energy to produce fresh water by means of thermal desalination." Rosatom said its focus was on seawater desalination using multiple effect distillation (MED) technologies requiring "a signifi cant amount of energy." It said the council of leading scientists and desalination specialists will develop the "best technological solutions" for water and water treatment markets customers of its international arm Rusatom Overseas. Chief executive offi cer of Rosatom Overseas, Dzhomart Aliev, said the company was "Prepared not only to construct a desalination facility based on nuclear technologies, but to operate it and ensure fi nancing too. With this approach, our aim is to become leaders in the global nuclear market". Among the council members are leading academicians and global specialists in desalination technologies with experience in design and technical evaluation of desalination facilities. Rosatom musters experts to create groundbreaking desalination plant Solar electrodialysis could bring water to off-grid villages Low-grade, waste heat produced by industry may be applicable for distillation desalination, to make fresh water where revere osmosis is not suitable according to fi ndings by the University of Western Australia (UWA). The study found that by supplementing distillation-desalination with multi-stage fl ashing increased the overall effi ciency of existing multi-effect distillation by 40–50%. UWA School of Mechanical and Chemical Engineering's Professor Hui Tong Chua said the technology was designed to maximize the low-grade – below 100ºC – heat that is often considered to be waste. Hui said the process was suitable for use with wastewater that was unfi t for reverse osmosis: "For rejected process streams from refi neries, and for high-saline, off pH, and/or high-silica content groundwater, the technology is most suitable," he said. "The technology is best suited to refi neries, such as alumina plant, where the conservation of steam is of paramount concern, and where the process fl uid cannot use reverse osmosis technology," he said. The fl ash-boosted MED required more energy than reverse osmosis for pumping and averaged a 22-34% energy penalty. "The new technology is essentially comparable to optimised MED, to within one per cent," said Hui. The system was scalable and had the potential for industry-wide adoption to produce or recover fresh water from process effl uent according to Hui. "The same technology can also be coupled with renewable energy, such as biomass, to provide a stable supply of water to remote communities," he added. Low-grade waste heat holds promise A simple set of solar panels and a battery system connected to an electrodialysis desalination unit could bring widespread relief from inadequate and unhygienic water supplies in India according to researchers at the Massachusetts Institute of Technology (MIT) in the US. The MIT scientists found that their proposed solar technique could produce potable water for Indian communities who have no connection to the power grid but have access to salty groundwater. Salty groundwater is present under some 60% of India and much of that area is not served by an electricity grid to power conventional reverse-osmosis desalination. The study, by MIT graduate student Natasha Wright and Professor Amos Winter, showed that solar-powered electrodialysis of saline groundwater could provide clean drinking water to supply the needs of a typical village. Winter said the search for optimal solutions to exploit saline groundwater – with weeks of fi eld research in India, and reviews of established technologies – "pointed very strongly to electrodialysis" – which is not commonly used in developing nations. Electrodialysis emerged as the lead candidate technology because of the low salinity of the groundwater at 500-3,000 mg/l compared with seawater at about 35,000 mg/l and the region's lack of electrical power. The health effects of drinking low-salinity water are long-term but its unpleasant taste drives people to drink dirtier sources. Pairing village-scale electrodialysis with solar panels and a battery to store the solar power creates an affordable way to produce enough palatable water for 2,000-5,000 people, the researchers concluded. Deployment of such systems would double the area of India in which groundwater could provide acceptable drinking water according to the MIT team. And groundwater carries a lower pathogen risk than surface water. Furthermore, electrodialysis recovers more than 90% of the treated water making it ideal where water is scarce. The researchers are planning to put together a working prototype for fi eld evaluations in India in January 2015. While this approach was initially conceived for village-scale, self- contained systems, Winter said it could apply in disaster relief and military use in remote locations.

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