Nanobubble technology applications in environmental and agricultural systems: Opportunities and challenges

Abstract

In recent years, there has been growing interest in the varied applications of nanobubble technology. Given their unique physicochemical properties, such as minuscule size (< 1 µm), surface charge, and high internal pressure, nanobubbles (NB) could provide new opportunities in the fields of environmental engineering (including environmental remediation, water treatment, aerobic fermentation, anaerobic digestion, and algal biomass production), and agriculture (including agronomy, horticulture, aquaculture, aquaponics, bioponics, and hydroponics). In addition, applying NB-derived reactive oxygen species (ROS) can inactivate pathogens in water treatment, remove harmful microorganisms on food, and remove persistent organic pollutants from wastewater (removal efficacies > 60%). NB technology can also maintain high aqueous phase dissolved oxygen levels compared to conventional aeration, as demonstrated in hydroponics and intensive crop farming, where NB-treated water led to increases in plant yields (10–40%). However, a concise and comprehensive source of information on the fundamental mechanisms involving NB technology is lacking. As NB applications advance into the biological frontier, these mechanisms serve as critical knowledge areas toward understanding the NB–biomolecular and cellular mechanisms of action. In addition, mass transfer performance is not stringently assessed. To advance and summarize current understanding, this review provides an updated, in-depth discussion of the fundamental mechanisms and performance of NB technologies for various applications in environmental and agricultural fields. Mechanistic details focusing on electrostatic and hydrophobic attachment, the formation of ROS, and gas–liquid mass transfer are discussed. This review further outlines the opportunities and challenges and concludes with important research needs in NB technology.

GRAPHICAL ABSTRACT

Keywords:

• Agriculture
• mass transfer
• nanobubble
• nanobubble–cell interactions
• reactive oxygen species
• water and wastewater treatment

Handling Editors:

• Eakalak Khan and Lena Q. Ma

Author contributions

K.R.M., L.L., and S.W.: carried out the initial literature search; formulated the content, scope, and interpretation of all information; designed and drawn all figures; and prepared the first draft. K.C.S., T.S., H.T.N., and H.L.: edited and reviewed the manuscript. S.K.K.: conceptualized and formulated the initial idea, supervised the preparation, and edited and reviewed the manuscript.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

The authors would like to acknowledge funding from the National Institute of Food and Agriculture, US Department of Agriculture (Award # 2021-67019-33681), the Team Science Project (College of Tropical Agriculture and Human Resources, University of Hawaiʻi at Mānoa), and the Hawaii Department of Agriculture (Contract # 67812). This work is also partly supported by the Center for Tropical and Subtropical Aquaculture through Grant No. 2020-38500-32559 from the National Institute of Food and Agriculture, US Department of Agriculture. Special thanks to Ricardo Linares for additional proofreading the manuscript and to Sining Zhou for his help on the featured artworks.