Singapore’s national water agency, PUB, and Hyflux Ltd have broken ground for the country’s second and largest seawater reverse osmosis desalination plant. The $890 million plant in Tuas, which begins operations in July 2013, will triple the Republic’s water desalination capacity.
That will bring Singapore closer to its goal of supplying 30 per cent of its water needs from desalination by 2061. The new plant will pump another 318,500 cubic m of water per day into the Republic’s national tap. That will add to the current 136,500 cubic m produced daily by the existing plant, which currently supplies 10 per cent of Singapore’s water needs. Singapore needs to get close to water independence because their water agreement with Malaysia expires in 2061. Singapore knows that Malaysia will try to gouge them for water supply in 2061.
At a pilot facility in Singapore, Siemens has cut the energy needed to desalinate seawater by more than 50 percent. The plant processes 50 cubic meters of water per day, consuming only 1.5 kilowatt-hours of electricity per cubic meter. The most efficient desalination technique currently in use is reverse osmosis, which consumes more than twice as much energy. The magazine “Pictures of the Future” reports that the new technique uses an electric field to remove the salt from the water. Plans call for demonstration units to be set up in Singapore, the U.S., and the Caribbean by mid-2012.
Turning one cubic meter of seawater into steam takes about 10 kilowatt-hours of electricity. By contrast, reverse osmosis, which presses the water through a filter, consumes about four kilowatt-hours for the same amount of water.
The new energy-saving system from Siemens uses electrodialysis. It extracts the salts’ positively and negatively charged ions from the water by means of an electric field. Special membranes that only allow a single type of ion to pass through create channels that collect either the resulting brine or the purified water. However, the process becomes inefficient as the salt concentration declines because the water’s electrical resistance increases. That’s why a Continuous Electrodeionization (CEDI) system is used to extract the last percentage of salt in the water. In this system, ion exchange resins located between the membranes capture the ions and transport them away from the water.
Experts from Siemens Corporate Technology are currently working on a simulation model that will help further improve the process. As part of a project sponsored by the German Research Ministry, the researchers will simulate the processes at the molecular level. They hope the model will help them to better understand the transport of the ions through the membranes as well as the dynamics of the water flow in the electric field.
Siemens developed the new desalination technique at the Singapore WaterHub, a research center for water treatment systems. The technology is part of Siemens’ Environmental Portfolio, with which the company generated about €28 billion in sales in fiscal year 2010.
It is a key technology for water reuse applications, this system uses a mechanical device that supplies irregular pulses of air to the MBR module, which increases scouring effectiveness, decreases operation and maintenance costs and reduces energy consumption by 30-40 percent over conventional MBR processes. It can also be easily retrofitted to existing plants that need to replace conventional clarification processes with membrane separation.
Energy consumption alone accounts for about 30 percent of municipal water treatment operating costs. At SIWW, Siemens will showcase energy efficient technologies and processes such as the BioFlowsheet+ process optimization program. This program integrates several key wastewater operations, including biological, solids separation, solids treatment and controls to significantly reduce energy costs. In addition, utilities strive to increase plant capacity and maintain a continuous water supply. The Siwa product family provides modular solutions that have been especially developed for water supply and wastewater treatment. Their focus is on electro-technical equipment for water transport pipelines and desalination plants, applying reverse osmosis. The portfolio encompasses systems and individual project solutions, including pipeline management, leak detection, automation packages and services for the life cycle of the plant.