For public health, having safe drinking water is important. However, conventional ways of disinfection have their own environmental issues. Although chlorine is low-cost and simple to use in centralized water systems, it comes at the cost of toxic chemical byproducts.
Ting Wang, a postdoctoral researcher in School of Civil and Environmental Engineering (CE), and Xing Xie, the Carlton S. Wilder Assistant Professor in CE. Image Credits: Georgia Institute of Technology.
Georgia Institute of Technology scientists have discovered a technique to employ tiny shocks of electricity to sterilize water, thus lowering energy consumption, price, and environmental impact. The technology can be integrated into the electric grid or even powered by batteries.
This is a pretty new disinfection technology, and we want to demonstrate in the small scale first, and then improve its real-world applications for point-of-use or off-grid water purification.
Xing Xie, Carlton S. Wilder Assistant Professor, School of Civil and Environmental Engineering, Georgia Institute of Technology
Xie and his postdoctoral researcher Ting Wang published the study in Nature Water in January 2023.
This ultra-fast bacteria inactivation just using the nanosecond pulses is a surprise because, theoretically, nanosecond pulses are just too short to kill the bacteria in conventional electric field treatment because the membrane takes time to charge.
Ting Wang, Postdoctoral Researcher, Georgia Institute of Technology
Localizing Electricity
Even though conventional electric field treatment (CEFT) is used to pasteurize food, it has not been extensively employed for disinfecting drinking water due to its high price. The bacteria cell membrane serves as a capacitor in a circuit when bacteria and water are exposed to electricity. Normally, in CEFT, the low conductivity of water implies nanosecond pulses will not charge the membrane quickly enough to destroy bacteria.
A locally enhanced electric field (LEEFT) was formed by the scientists, which drove the electricity directly to the bacteria. With gold nanotips building up concentrated charges directly when connected to electricity, the electrodes allow the charges to move to the membrane and destroy the bacteria more rapidly.
This ultra-fast bacteria inactivation just using the nanosecond pulses is a surprise because, theoretically, nanosecond pulses are just too short to kill the bacteria in conventional electric field treatment because the membrane takes time to charge. But with LEEFT’s nanowedges and nanostructures, the bacteria cells can be charged directly by the nanometal, quickly disinfecting water.
Ting Wang, Postdoctoral Researcher, Georgia Institute of Technology
Electric Innovation
The researchers fabricated gold nanowedges on a chip’s electrode edge to assess the technology. Later, the model bacteria Staphylococcus is added to the chip, often found in water systems and commonly used in labs. Finally, electric pulses were applied and the reaction of bacteria was watched in real-time using a microscope.
95% of nanowedges killed the bacteria efficiently upon applying electricity at 40 kV/cm for 200 nanoseconds. Upon comparison with conventional EFT, LEEFT reduces applied eclectic field strength by eight times—and quickens the treatment time by 1 million times.
“We found that even nanosecond pulses could kill the bacteria in the LEEFT and not other circumstances,” Wang stated. This near-instantaneous decontamination decreased the amount of electricity required to disinfect water, which makes this a cost-efficient sanitation option and points to a future where producing clean water might leave a lesser impact on the environment.
Journal Reference:
Wang, T. and Xie, X. (2023) Nanosecond bacteria inactivation realized by locally enhanced electric field treatment. Nature Water. doi.org/10.1038/s44221-022-00003-2.