In a typical industrial water treatment or water reuse process, the final steps of purification require an ultrafiltration membrane to filter out small particles, then a reverse osmosis (RO) membrane to separate water molecules from even the smallest remaining contaminants like salt, heavy metals, and other microscopic, toxic chemicals.
Pushing the water through such fine RO membranes requires high pressure — around 10 bars, or one million pascals (Pa) — and achieving that pressure means expending a lot of costly energy.
Being as energy-intensive as it is, the RO process is a prime area for potentially cutting down on costs in wastewater treatment and making strides in refining the water-energy nexus. In Singapore, a hotbed for technological innovations of all kinds, researchers may have done just that.
Scientists at Nanyang Technological University (NTU) have developed a new type of nanofilter that requires as little as one-fifth of the energy needed to treat wastewater and achieves purification at almost the same level as RO.
The nanofilter consists of a hollow fiber membrane that combines ultrafiltration and RO into a single process — requiring only 2 bars (200,000 Pa) of pressure, about the same amount found in a typical home pressure cooker.
On an island smaller than New York City, the innovation was born out of a need to conserve space as much as energy.
“In Singapore, there are many companies in the metals processing industry or the food and fragrances sector which use water for cleaning and production,” said Dr. Adrian Yeo, the chief technology officer for De.Mem, a company that commercializes NTU’s technology. “Because there is lack of space in Singapore, the real estate given to water treatment plants at industrial estates is quite scarce, so it would make sense to have a filter that could retain contaminants such as salts, heavy metals, and toxic chemicals to meet discharge standards yet use low pressure to reduce energy costs.”
De.Mem approached NTU professor and director of the Singapore Membrane Technology Wang Rong to develop a membrane that would meet their needs, Yeo said. Wang and her team of researchers developed the new membrane over two years.
“One of the main challenges faced by the industry is that current RO processes are energy intensive, with downtime needed for maintenance,” Wang said in a statement from NTU. “Our new membrane is also easy to manufacture, using low-cost chemicals that are 30 times cheaper than conventional chemicals, making it suitable for mass production.”
De.Mem operates over a dozen water treatment plants in Singapore and Vietnam and plans to build a pilot production plant to manufacture the new membranes. Yeo is working with Wang and her team to scale up the technology and vet it at a network of testbeds before implementing a full industrial production line.
Yeo did not say when the technology might be ready for use by Western treatment operations. If and when it is, it would almost certainly be welcome.