Energy-efficient filters for wastewater treatment process

A new type of nanofilter that could reduce the energy used to treat wastewater by up to five times has been developed by scientists at Nanyang Technological University (NTU Singapore).

Usually, for the last steps of water purification in a wastewater treatment process, an ultrafiltration (UF) membrane filters out small particles before a reverse osmosis (RO) membrane is used.In reverse osmosis, water is pushed through an extremely fine membrane at high pressure to separate water molecules from any remaining contaminants which are tiny – about a thousand times smaller than the width of a human hair, such as salt, heavy metals and toxic chemicals like benzene.

The high water pressure, typically 10 bars and above, means that the water pumps need a lot of energy.

However, NTU’s proprietary nanofiltration (NF) hollow fiber membrane already combines the ultrafiltration and reverse osmosis processes. It only requires 2 bars of water pressure, similar to the pressure found in a typical home pressure cooker, to filter out the same type of contaminants. Yet it produces water that is almost as pure as through reverse osmosis.

The breakthrough technology took NTU’s Nanyang Environment and Water Research Institute (NEWRI) about two years to develop and is now being commercialized by an NTU spin-off company De.Mem.

The company owns over a dozen water treatment plants in Vietnam and Singapore and will be building a pilot production plant in Singapore to manufacture the new membranes.

NTU Professor Ng WunJern, the executive director of NEWRI, said the new technology marks yet another huge step forward for Singapore, as it will be the first of its kind to hit the market.

“With the increasing urbanisation of cities and fast growing global population, more cities and communities will face an unprecedented challenge to meet its growing demand for clean water and wastewater treatment,” Professor Ng said.”If we are to address the ever increasing demand for clean water, what the world needs are innovative technologies like NTU’s new nanofiltration hollow fibre membrane that allow us to treat and produce extremely clean water at a low cost, yet have high reliability and are easy to maintain.”

NTU Professor Wang Rong, the director of NEWRI’s Singapore Membrane Technology Centre who led the team in designing the new NF membrane, said that the new membrane is easy to manufacture using low-cost chemicals that are 30 times cheaper than conventional chemicals, which makes it suitable for mass production.

De.Mem will test the new membrane modules in real world usage in its plants to verify its effectiveness and efficiency before scaling up to a full industrial production line.