Ozone microbubbles treatment with different gas–liquid mixing conditions and its application on printing and dyeing wastewater and Escherichia coli

• Published in: Desalination and water treatment 2022-03, Vol.252, p.400-407
• Main Authors: Wu, Chundu, Zhu, Kaida, Hu, Xinkang, Nkudede, Emmanuel, Hu, Shan, Zhang, Bo
• Format: Article
• Language: English
• Subjects: Disinfection; Mass transfer capacity; Mixing condition; Ozone microbubble; Wastewater treatment
• ISSN: 1944-3986
• DOI: 10.5004/dwt.2022.28256

The low solubility of ozone in water limits its oxidation reaction rate, while microbubbles can enhance the gas–liquid mass transfer process and effectively improve the mass transfer rate of ozone. In this study, we set up an ozone microbubble generation system, with an internal recycle, a self-made releasing device using 3D printing and other designs to keep the system running steadily, with constant pressure, high ozone concentrations, and slow microbubble dissipation rate. This study investigated the ozone feed rate and optimization of mixing conditions through the test. With the increase of ozone feed rate, the average concentration of ozone in the solution tends to increase linearly, then decreases slightly after reaching the maximum 13.75 mg/L. On a stable running of the system, the ozone concentration of the solution could reach 13.29 mg/L. The ozone microbubble was then investigated by calculation and measurement of bubble disappearance time, particle size and mass transfer capacity. This study found the particle size of bubbles was about 42.66 μm and KLa (20) was 10.712 min–1. The system’s applications were then studied to demonstrate the effect of ozone microbubbles. Under strong alkaline conditions and without acid adjustment, COD of printing and dyeing wastewater could reach Chinese first-class A discharge standards after treatment with ozone microbubbles. Another experiment proved that ozone microbubble solution of 8 mg/L had more than 99% killing effect on Escherichia coli.