What are nanobubbles and how do they disinfect water?

Scientists say nanobubble research has boomed in the past decade and has led to many benefits for agriculture, medicine and wastewater management.

At the forefront of the work is a group from the University of Calgary, which has experimented with the technology and produced unique results.

“When I introduce nanobubbles into water, I’ve introduced a whole bunch of extra surfaces into the system, which is a very reactive environment that can lead to a lot of interesting chemistry,” says Dr. Peter Kusalik, professor in the U of C’s department of chemistry in a press release.

Kusalik is working with Dr. Susana Kimura Hara on the research.

“I am interested in nanobubbles because they can make water treatment processes more efficient and faster, which can help increase water sustainability,” said Kimura Hara.

Nanobubbles are small gas bubbles that are measured in nanometers (nm) – one billionth of a meter – and have better gas transfer properties than their larger equivalents.

To give an example of their size, a DNA molecule is 2.5 nm wide, while a human hair is 60,000 to 100,000 nm wide.

One of the industrial applications of nanobubbles is their role in wastewater and water treatment.

“Nanobubbles can be used to introduce ozone – a strong water disinfectant – into water to disinfect and break down stubborn contaminants, and the unique properties of the nanobubbles will make this process faster,” the U of C said in a press release .

Testing new methods to make them

One of the challenges of working with nanobubbles is the enormous amount of energy required to create them, researchers said.

Currently, nanobubbles can be produced by mechanical methods of rapid and aggressive churning or flowing water.

Instead, researchers from Calgary use electric fields to produce large amounts of nanobubbles in water, while using much less energy.

“In this process, a grid of insulated wires is immersed in water and a voltage is applied, and the electric field generated between the wires produces nanobubbles,” the U of C said.

“The electric field method is not only more energy efficient, but can also generate a solution containing only nanobubbles with a population of approximately 100 billion per liter of water.”

Nanobubble montage by Jon Tallon, graphic designer. (Credit: Professor Niall English, UCD School of Chemical and Bioprocess Engineering)

Better plants, better beer

Nanobubbles have also proven beneficial to agriculture, officials said.

In one experiment, the school says nanobubble-filtered water was used on plants grown for a high school student’s science fair project.

The seedlings grew 40 percent more than those watered with plain water, officials said.

In addition to plant growth, the school says the large surface area produced by the nanobubbles improves the fermentation process in brewing, resulting in a higher quality product.