Improved water treatment using less energy

As the world’s population grows, conserving as much of our limited resources as possible is essential. With more people vying for the limited water supply, ensuring everyone has clean drinking water can be difficult, and making it even harder is limiting the energy we use to treat that same water.

In this spirit, Jeff Ong, of European technical university EPFL’s Laboratory of Inorganic Synthesis and Catalysis, developed a system set to be tested in real-world situations, which combines current water treatment technologies while consuming less energy, according to a recent article by Cecilia Carron.

“For example, the prototype removes more than 99.9% of salt from seawater with the same throughput but using less energy,” Carron reports.

Traditional, large-scale reverse osmosis, one of the most common desalination technologies, can consume as much as 4-5 kWh/m3 of electricity, and have additional costs for replacing membranes and other worn components. The prototype machine’s membranes are made of an inert hydrophobic material that lasts longer than traditional membranes and can be cheaply recycled, Carron reports.

Taking it further, the machine is designed with a series of desalination modules, which are what allow it to achieve more than 99.9% salt separation. In order to decrease energy consumption, Carron reports that Ong implemented flow principles commonly used in nuclear power.

“To address the system’s main weakness—energy consumption—he made several improvements including internal heat recovery and more efficient heat transfer. By reducing the pressure, the water can be brought to a boil at a temperature of less than 80 °C,” Carron explains. “The vapor produced is cooled and recovered as fresh water. The rest of the liquid, which contains the remaining salt, passes into another cell with even lower pressure, and so forth. Heat recovery elements are used to pre-heat and vaporize the remaining saltwater, without using any energy from outside the system. At each stage, the vapor produced is cooled and the resulting fresh water is recovered. The fresh water is removed using heat exchanger devices that are positioned so as to cool the system.” 

The machine also has been optimized for throughput, now twice that of reverse osmosis systems, and also can handle salt concentrations that are four-times the capabilities of reverse osmosis.

The machine will be commercialized by start-up Aqualife Global, Carron reports.