Scientists at Singapore’s Nanyang Technological University, NTU, have designed a nanofilter that could reduce energy consumption at wastewater treatment plants by up to five times. The hollow-fiber membrane combines the conventional two-stage treatment process into a single step.

Typically, in the latter stages of water purification in wastewater treatment, an ultrafiltration membrane filters out small impurities before a reverse osmosis membrane is used.

De.Mem wastewater treatment plant. Source: De.Mem Pte LtdIn reverse osmosis, water is pushed through a fine membrane at high pressure to separate water molecules from any remaining contaminants such as salt, heavy metals or harmful chemicals like benzene, which can be miniscule. But this high water pressure, typically 10 bars and above, requires a lot of energy.

NTU’s hollow-fiber membrane eliminates both ultrafiltration and reverse osmosis, combining the two processes. It also requires 2 bars of water pressure, similar to that found in a typical home pressure cooker, to filter the same type of contaminants. Yet it produces water that researchers say is nearly as pure as through reverse osmosis.

“One of the main challenges faced by industry is that current reverse osmosis processes are energy intensive, with down time needed for maintenance,” says Professor Wang Rong, chair of NTU’s School of Civil and Environmental Engineering. He says the membrane is easy to manufacture using chemicals that are less expensive than conventional chemicals, possibly making them suitable for mass production.

The nanofilter is now being commercialized by an NTU spin-off company, De.Mem Pte Ltd. De.Mem owns over a dozen water treatment plants in Vietnam and Singapore, and will build a pilot production plant to manufacture the membranes. It also will test the modules at some of its wastewater facilities before scaling up to full industrial production.