Low-energy seawater desalination technology ready for full-scale testing

SINGAPORE – Having set a new energy-saving benchmark for seawater desalination, Siemens said it is ready to transition its technology to the product development phase. As a result of a research and development initiative that began in October 2008, a demonstration plant was built in Singapore to treat seawater to drinking water quality. According to the company, the results, presented at Singapore International Water Week, show that the new process reduces desalting energy by more than 50 percent compared with best available technology. Next, Siemens plans to set up a full-scale system in cooperation with Singapore’s national water agency PUB by 2013.

Since December 2010, the Siemens demonstration unit has been treating 50 cubic meters of seawater per day at a PUB facility in Singapore. Instead of using reverse osmosis, which requires high-pressure pumps to force water through semi-permeable membranes, the process combines Electrodialysis (ED) and Continuous Electrodeionization (CEDI), both applying an electric field to draw sodium and chloride ions across ion exchange membranes and out of the water. As the water itself does not have to pass through the membranes, the process can be run at low pressure, and hence low power consumption.

The seawater is pretreated with a self-cleaning disk filter, followed by Memcor ultrafiltration modules. The pilot desalination plant is composed of three ED units arranged in series to handle high concentrations of salt. They are followed by three CEDI units assembled in a parallel flow configuration to remove smaller amounts of salt. The energy demand of the whole process including pumping, pretreatment, desalting, and post-treatment is less than half of what is used by the best available seawater desalination technologies today, which is typically between 3.4 kWh and 4.8 kWh per cubic meter. Besides the energy savings, other advantages are low vibration and noise levels, improved safety, and minimal pre- and post-treatment.

These achievements have been attained in close partnership with Singapore’s national water agency PUB and Singapore’s Environment & Water Industry Programme Office, which awarded a research and development grant to co-fund Siemens as a result of a Challenge Call in 2007.

More information is available at www.siemens.com/siww.