Having set a new energy saving benchmark for seawater desalination, Siemens is now poised to transition to the product development phase. As a result of a research and development initiative that commenced in October 2008, a demonstration plant was built in Singapore to treat seawater to drinking water quality.
The results, which will be presented at Singapore International Water Week, show that the new process reduces desalting energy by more than 50% compared to best available technology. The next step for Siemens is to set up a full-scale system in cooperation with Singapore’s national water agency by 2013.
In Singapore, seawater is becoming increasingly important in replenishing the supply of drinking water. However, to desalinate it for potable use is an extremely energy-intensive process.
Instead of using reverse osmosis, which requires high-pressure pumps to force water through semi-permeable membranes, the Siemens engineers turned to electrochemical desalination. 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, 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. Besides the energy savings, other advantages are low vibration and noise levels, and improved safety.