Using Oxygen Ultrafine Bubble Injectors to Treat Various Water Types

We evaluated an oxygen ultrafine bubble (UFB) injection system as a novel method to increase and maintain high dissolved oxygen (DO) concentrations in water. The study was conducted in a greenhouse, where we tested the system's performance using 100-L samples of stormwater, groundwater, and drainage water under steady-state water conditions. The oxygen UFB system was evaluated based on three key parameters: (1) the maximum DO concentration and the time taken to reach it during the UFB injection phase, (2) the volumetric oxygen transfer rate during the injection and dissipation phase, and (3) the time taken to return to preinjection DO concentrations (dwell time) after the oxygen UFB injection. In addition, other water quality variables, including pH and water temperature, were measured for each water type. Their variation was analyzed as a function of changes in DO concentration throughout the experiment. On average, the UFB injection system increased DO concentrations to 35.23 mg/L in 17 min. The average oxygen transfer rate during the dissipation phase was 0.478, 0.411, and 0.489 mg/L/day for stormwater, groundwater, and drainage water. Groundwater was the most stable water type, with a dwell time of 15 days. Our findings suggest that the UFB injection system is a promising technology for increasing and maintaining high DO concentrations in water types for prolonged periods, which will help to mitigate hypoxia/anoxia-related environmental concerns (e.g., eutrophication and toxic algal blooms).