Researchers Develop Low Energy, Cost-Effective Wastewater Purification System

New innovation can remove up to 99 per cent recalcitrant impurities from industrial wastewater without using chemicals or generating sludge.

Researchers from NUS Faculty of Engineering have come up with a novel wastewater purification system that can remove up to 99 per cent of hard-to-treat organic compounds found in industrial wastewater.
Researchers from NUS Faculty of Engineering have come up with a novel wastewater purification system that can remove up to 99 per cent of hard-to-treat organic compounds found in industrial wastewater.

Wastewater, containing the hard-to-treat organic compounds, can now be purified up to 99 percent. A team of scientists from the National University of Singapore has come up with an efficient wastewater purification system operates on low electrical power. The system uses electricity as a reagent for purification as well it does not generate secondary waste, such as sludge, that requires further costly residual waste processing such as incineration.

“Despite the great advances in wastewater treatment technologies, the removal of refractory organic compounds remains a costly and challenging process. Our invention provides an environmentally friendly solution and helps to raise the overall standard of industrial wastewater treatment,” said Assistant Professor Olivier Lefebvre from the Department of Civil and Environmental Engineering at NUS Faculty of Engineering, who is the leader of the research team.

This highly requisite water purification system is efficient to purify wastewater from the electronics and pharmaceutical industries which may contain the high concentration of solvents and mixtures of complex organic substances, while wastewater from farmlands may contain the high concentration of pesticides or herbicides. These organic compounds are not biodegradable and can be harmful to humans and the environment.

Assistant professor Lefebvre said, “Our electrochemical system has shown that it can achieve complete mineralization of any organic pollutant. This means the system can completely remove organic compounds in the wastewater by degrading them into water and carbon dioxide.”

“This novel system can also be incorporated as a pre-treatment to an existing wastewater treatment scheme. It operates on low electrical power and the system could easily be combined with solar power and other purification methods such as using membranes and biological treatments.”

Purification process starts with the pumping of wastewater into the system’s chamber. As electric current is passed, electrodes in the chamber generate hydrogen peroxide and hydroxyl radical (one of the most powerful oxidizing agents) that will react with the complex organic compounds in the water.

Now, the generated hydrogen peroxide and hydroxyl radical are completely used up during the treatment and they continuously break down the complex compounds into simpler molecules, until all organic contaminants have been degraded into water and carbon dioxide. This complete system uses electrochemistry to treat water and does not require chemicals to be physically added to the system.

Assistant Professor Lefebvre, who is also a Principal Investigator at NUS Engineering’s Centre for Water Research said, “When we started this project in July 2014, we aimed to use our expertise in electrochemistry and know-how in reactor design to create a robust, highly efficient and easy to operate water purification system for industrial wastewater that can reduce the need for third-party processing or disposal.”

“Our low-voltage electrochemical system can be installed in manufacturing plants of many different industries. The factories can easily reuse the treated water for their other processes and even control how pure the water is, according to their different needs.”

Considering, today’s need of large volumes for ultrapure water for processes, the team of NUS scientists comes up with a system which will not only purify water from farmland, electronics and pharmaceutical industries but also be utilised by heavy manufacturing industries such as mining, oil and gas, textile industries and the shipping industry for the disinfection of problematic ballast water from ships.

It could also be applied to treat micropollutants in domestic wastewater as well as manage water purity in the various outdoor environment such as in controlling algal growth in water bodies and purifying landfill leachate.