Improving dairy wastewater treatment with nanobubble technology

South Dakota State University Endowed Alfred Chair associate professor in dairy manufacturing Maneesha Mohan is utilizing nano-sized bubbles to improve the efficiency of dairy wastewater treatment.

When dairy products are produced, wastewater is generated. This wastewater, containing pathogens, organic compounds, nutrients and other pollutants, must be treated before it is discharged into surface water as the pollutants can be harmful to human health and can create environmental issues.

Dairy plants often have their own treatment plant to handle the large volume of wastewater that is generated each day. The treatment plants must be well designed to handle the challenging differences in volume and concentrations of wastewater on a day-to-day basis.

Maneesha Mohan, South Dakota State University’s Alfred Chair in Dairy Manufacturing and an associate professor in the Department of Dairy and Food Science, is utilizing a simple but innovative technology to help dairy plants treat their wastewater: nanobubbles.

Nanobubbles are 2,500 times smaller than a grain of salt but have unique characteristics that have led to their applications in a variety of industries, including drug delivery, agriculture and water pollution. Mohan first learned of nanobubbles in New Zealand. There, the technology is used to extend the shelf life of harvested fish. The findings are published in the journal Trends in Food Science & Technology.

“As a dairy scientist, I have been very interested in incorporating nanobubbles into the dairy field,” Mohan said. “When I came here, I started investigating ways in which we can utilize nanobubbles.”

Nanobubble technology works through a generator, into which liquid is pumped. Inside the generator, swirling action—hydrodynamic cavitation—puts gas into the low-pressure area, breaking the bigger gas bubbles into nano-size bubbles (nanobubbles).

These gas-filled bubbles remain stable in the liquid for extended periods of time (even a few months), allowing them to interact with different compounds. They can also increase oxidation rates. This characteristic is beneficial in wastewater treatment as it allows for increased degradation of organic compounds and total solids found in wastewater.

“The nanobubbles improve the quality of the wastewater that is discharged,” Mohan said.

To put this technology to use, Mohan investigated the application of nanobubble technology in dairy wastewater treatment.

Mohan and her master’s student, FNU Akshit, started working in the lab to enhance their understanding of nanobubbles and the ways to apply them in dairy wastewater treatment. The results were promising. They found nanobubbles significantly reduce biochemical and chemical oxygen demands along with suspended solids by 10.6%, 5.77% and 16.5% respectively, while increasing dissolved oxygen by 134%.

In 2024, Mohan and Akshit implemented nanobubble technology at Valley Queen Cheese— one of the largest dairy processing facilities in South Dakota. Valley Queen Cheese, located in Milbank, is one of the first dairy manufacturers to use nanobubbles in their wastewater treatment and, according to Mohan, the incorporation has been rather successful as they no longer need to use chemicals in their wastewater treatment.

“The nanobubble generators have been playing a major role in helping Valley Queen control how they handle their wastewater, and their effluent treatment plant has been more efficient after incorporation of nanobubbles,” Mohan explained.

The generator used at Valley Queen Cheese was from a commercial company. But as Mohan notes, they identified ways that nanobubble generators can be improved specifically for the dairy industry. Mohan is now working with faculty members in the Jerome J. Lohr College of Engineering to design their own nanobubble generator.

“In our lab, the whole idea is to look at sustainability and a holistic approach,” Mohan said. “We work to improve process efficiencies in different food processing systems.”

Last spring, Mohan and Akshit published a paper overviewing nanobubble technology in dairy processing applications.