A step forward for an energy-saving desalination process

An alternative desalination process that reduces energy consumption by over 50% compared to best available technology (BAT) has been successfully piloted by the Industry Sector of Siemens AG (Munich, Germany; www.siemens.com), in collaboration with Singapores national water agency, PUB, and Singapores Environment and Water Industry Program (EWI). Results of the Siemens demonstration unit, which has been operating since December 2008 and treating 50-m3/d of seawater, were presented last month at the Singapore International Water Week (Singapore; July 4–8). Siemens, in cooperation with PUB, plans to build a full-scale system by 2013. Instead of using reverse osmosis (RO), which requires high-pressure pumps to force water through semipermeable membranes, Siemens process combines electrodialysis (ED) and continuous electrodeionization (CEDI), both of which draw sodium and chloride ions across ion-exchange membranes. Because the process runs at low pressure, power consumption is lower than that required for RO. Seawater is first pretreated with a self-cleaning disk filter, followed by Memcor ultrafiltration modules. The pilot desalination plant is composed of three ED units in series to handle the high concentrations of salt. These…