Nanobubbles for algae cleanup: Q&A with researcher Wen Zhang

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One of the most powerful environmental cleaning technologies in recent years is too small to see with the naked eye. Nanobubbles—tiny gaseous bubbles with diameters of around 100 nanometers—can clean up a range of harmful pollutants in water, from oil spills to algae.

Wen Zhang, a New Jersey Institute of Technology professor of civil and environmental engineering, knows a thing or two about nanobubbles. He is the principal investigator of NJIT's AI-Enabled Advanced Materials and Systems for Environment and Agriculture Laboratory and has led efforts using nanobubbles to mitigate harmful algal blooms.

Zhang's patented nanobubble technology is used by PureNanoTech, an NJIT-supported startup company providing nanobubble generation systems for research and industrial purposes.

Nanobubbles were recently in the news as a potential solution to an algae problem in Washington, D.C., when the U.S. Department of the Interior announced that they were using "high-tech nanobubbler ozone technology" to tackle an algae bloom in the Lincoln Memorial Reflecting Pool. Algae growth spiked there after the completion of a renovation, fueled by warm weather and nutrients in the water.

While Zhang was not involved in the Reflecting Pool cleanup, he shared insights addressing the technology's capabilities and how nanobubbles might perform in a project of this scope.

Nanobubble technology involves injecting extremely small gas bubbles into water, typically using gases such as air, oxygen or ozone. In water treatment, the main value is not just "tiny bubbles" but the fact that they can improve gas transfer, create a very large gas-water contact area, and stay suspended longer than ordinary bubbles.

In practice, that can improve oxygen delivery, oxidation, and contact between the treatment gas and algae-affected water. Nanobubble systems are already being studied and applied in water and wastewater treatment, aquaculture, and related environmental uses.

For algae control, the effect depends strongly on the gas being used. Air or oxygen nanobubbles are generally a gentler ecological approach; they can increase dissolved oxygen and may stimulate heterotrophic bacteria and other aerobic processes that compete with algae for nutrients, so they can suppress blooms indirectly rather than simply "poisoning" algae.

Ozone nanobubbles are much more aggressive. Ozone is an oxidant, so it can damage algae cel