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    October 06, 2011

Australian Researchers Aim for Greener Desalination

   Phil Mercer | Sydney
   Trucks arrive at the water filling station of an aluminum smelting
   plant to get fresh water distilled from Gulf seawater in Dubai, United
   Arab Emirates (File Photo).
   Photo: AP
   Trucks arrive at the water filling station of an aluminum smelting
   plant to get fresh water distilled from Gulf seawater in Dubai, United
   Arab Emirates (File Photo).

   Researchers in Sydney are leading a new international effort to make
   desalination more environmentally friendly. Current techniques tend to
   use excessive amounts of energy or are heavily reliant on chemicals.
   The University of Technology in Sydney is working with teams from
   Singapore, Saudi Arabia and South Korea to improve the filtration
   process to make it more efficient and gentler on the environment.
   Removing salt from water
   Desalination is often seen as an expensive and energy-intensive way to
   remove salt from water. In Australia - the world's driest inhabited
   continent where rainfall has become increasingly erratic - desalination
   plants treat seawater that can produce almost half of the supplies
   needed by the major cities.
   'There is a significant increase in the trend for the desalination
   market," explained
   Professor Vigi Vigneswaran from the University of Technology in Sydney.
   He says the science has growing international value.

   "Whether we like it or not, with the global warming problems, the
   desalination will become a very important technology - one of the
   important technologies - other than the water reuse and storm water
   harvesting," Vigneswaran said.
   New techniques
   One of the projects that researchers in Sydney are pursuing is
   improving the membranes used in pre-treatment systems in desalination
   plants.
   These thin films often become clogged, reducing their efficiency and
   increasing the amount of energy used to take the salt out of seawater.
   The team in Sydney is developing new biological filters that do not
   become so congested and will not need chemicals that absorb
   contaminants.
   Researcher Christian Kazner says more effective filtration will cut
   energy usage.

   'Membranes are very sensitive to everything which is contained in the
   water," noted Kazner. "It will be stopped by the membrane and grow on
   the surface of the membrane, whether it is salts, you have scaling, it
   is blocked. Or whether it is organic contaminants they really collect
   on the surface and if you have microbes they can grow on that organic
   material. As much as you remove those contaminants before you filter it
   you improve the performance of the membrane, you reduce the energy
   demand and finally you can extend the lifetime of the membrane.'

   Forward osmosis

   While conventional desalination systems rely on a process called
   reverse osmosis that uses pressure to force water through membranes,
   work is also being done on an alternative process. Forward osmosis
   needs far less energy and allows water to effectively be sucked through
   the filters.
   Scientists in Sydney believe this method could reduce energy
   consumption in the desalination process by up to 90 percent.
   Other projects being developed include mobile salt-removal systems for
   remote Aboriginal communities where supplies from groundwater wells are
   contaminated by high concentrations of saline and nitrates.
   The aim is to export ideas and innovation overseas, especially smaller
   desalination units for use in developing countries, where safe and
   sustainable water supplies remain a distant dream for many.