The effect of microbubble (MB)-generation and treatment conditions on the characteristics of MB and MB containing water was evaluated. For MB generation, a MB generator based on the pressurizing dissolution method (operated at 0～0.5MPa) was used, and the high discharge pressure likely resulted in small bubbles and highly turbid (which indicates the MB density) MB containing water. The most effective discharge pressure for the preparation of ozonized water was 0.2 MPa. However, this pressure was different from the optimal pressure for MB generation. The MB treatment (mechanical agitation) increased the ozone dissolution rate. Moreover, the ozone dissolution rate and equilibrium concentration of dissolved ozone varied with the addition of particular substances. For example, when NaCl or a surfactant (L-150A) were added, the ozone dissolution rate and equilibrium concentration of dissolved ozone were higher and lower, respectively, than the rate and concentration of control condition (RO water) . Moreover, the addition of citric acid resulted in an ozone dissolution rate and equilibrium concentration of dissolved ozone that were similar to and higher than, respectively, the rate and concentration of control. Finally, considering the results for the discharge pressure and ozone dissolution rate, it can be concluded that the MB-generation method and MB-treatment conditions should be selected in strict accordance with the intended use of MBs.
