Water. desalination + reuse

RESEARCH August-September 2014 | Desalination & Water Reuse | 37 | Combined cooling and desalination "limits environment impact" Scientists at the University of Technology, Sydney have devised a forward osmosis system which they claim could reduce the energy used in desalination deployed for irrigation by up to 80%. Australia uses 60% of its water supply for irrigation. Research leader, Dr Hokyong Shon, said the process had much to offer a country that uses so much of its water for irrigation. "By reducing the demand that irrigation places on our traditional water supplies, we are conserving precious water for domestic use in our homes," said Shon. Researchers from the university's Centre for Technology in Water and Wastewater (CTWW) have exploited the developing technology of fertiliser drawn forward osmosis (FDFO). The FDFO system draws water from saline via osmosis by employing high-concentration, soluble fertilisers - typically ammonium hydrogen phosphates - on the opposite side of a membrane filter. Forward osmosis relies on osmotic pressure and so requires less energy than reverse osmosis. And the CTWW researchers claim membrane fouling is much less prevalent in the forward process. A pilot installation of a FDFO system has been adopted by New South Wales State Water through the National Centre of Excellence for Desalination Australia and is currently being used at a coal-mining site to desalinate groundwater. Scientists' findings could reduce irrigation demand on desalination Studies by a company proposing to construct a groundbreaking combination of desalination plant and data centre have shown the facility will cause only limited negative impact to the environment according to the researchers. The three-year study by DeepWater Desal found that the 125 Ml/d desalination plant proposed for a site on the central California coast would: • reduce emissions by using coolant water from a proposed data centre; • kill few fish; • meet current and future restrictions on release of brine into the ocean; and • create fewer geological risks than drilling owing to its use of a deepwater canyon as its seawater source. "What's exciting for us is that our theories have been validated by these studies," said DeepWater spokesman, David Armanasco. A full environmental review of the project is to come following DeepWater Desal's submission of its plans to the State Lands Commission on 30 May. The plant has been proposed as a future water source for supplier Soquel Creek Water District. The proposal calls for drawing cold seawater from the Monterey Submarine Canyon. After using that water to cool a proposed data centre on the site, the then warmed water will pass to a reverse-osmosis desalination plant. The heat absorbed in the data centre cooling will reduce the energy needed for desalination. This combination of data centre cooling and desalination is unique and will emit significantly less carbon than would both facilities operating separately, DeepWater Desal said. DeepWater Desal foresees the proposed plant as producing water for Santa Cruz County. Soquel Creek's expression of interest is the only one to date. Soquel Creek serves 35,000 people and relies currently on an overdraughted groundwater basin. Researchers in the USA have unveiled a new device that could be used in a solar-powered, near-equivalent of flash distillation to improve the sustainability of seawater desalination. The sponge-like device developed at the Massachusetts Institute of Technology (MIT) consists of a 10 cm diameter disc comprising a layer of graphite flakes with porous carbon foam attached beneath it. The device floats on water where, according to the researchers, it converts 85% of solar energy into heat to form steam. It applies the heat to a small volume of water - a principle behind flash distillation: "Basically, if you heat up the whole volume of the water, you don't raise the temperature very much. However, if you only heat up a small amount of water, then the temperature rise could be high," explained MIT professor of mechanical engineering, Gang Chen. Chen explained that by floating the graphite on the surface of the water, the researchers were able to concentrate the maximum amount of incoming sunlight. He went on: "In remote areas where the sun is the only source of energy, if you can generate steam with solar energy, it would be very useful." Chen said he was excited about the potential for the material in water treatment, desalination or treating wastewater. The potential, he said, could be huge for water treatment in isolated, impoverished areas. He was careful to emphasize, however, that his team's recent breakthrough in the laboratory was just a first step. Carbon sponge could decarbonize desalination Nanofiltration market poised to soar Desalination is one of the primary forces behind nearly three quarters of 15% growth forecast in the nanofiltration (NF) market worldwide that will take it above US$ 445 million by 2019 according to market researcher BCC Research. In its latest report, Global markets and technologies for nanofiltration, BCC has predicted the water and wastewater treatment market will generate 74.6% of the UF market share, reaching US$ 338 million in 2019. Revenues will be "driven by sales of nanofiltration membranes for water softening, desalination, and wastewater treatment," according to BCC. Growth in the sector was forecast by BCC at more than 16%. BCC attributed the increased market penetration of NF products to factors including: rising demand for potable water and reduced freshwater sources; environmental restrictions on industrial and municipal wastewater discharges; and lower operating costs compared to, for example, reverse osmosis.

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