Characterization of air submicrobubbles for water treatment under different generation conditions

Micro-nanobubble (MNB) technology has been proven to be effective in water and wastewater treatment. Submicrobubbles (SMBs) are considered to be a subgroup of MNBs ranging from 1 to 10 μm with limited studies related to their fundamental properties. This study focused on the fundamental characteristics of SMBs and the effect of generation conditions such as temperature, aeration time, and water volume on their properties. SMBs were generated under high pressure using shear force and their size and distribution were measured using the dynamic light scattering method. Dissolved oxygen (DO) concentrations were monitored during and after the generation. The zeta potential of the generated bubbles was also measured to assess bubbles stability. SMBs with a median diameter of 2 μm persisted in water even after the generator was stopped, indicating the high longevity of SMBs in water. Regardless of the aeration time or water volume used, the zeta potential of SMBs was highly negative with average values ranged between - 28 and - 30 mV, indicating high stability in water. DO concentration increased by up to 1.5 folds within a few minutes of generation and slightly decreased over 1 h. Results demonstrate that air SMBs are stable with long lifespan and high DO concentration.