Superior Water Disinfection via Ozone Micro-bubble Aeration: Performance and Mechanism

Ozone has been widely applied in water disinfection because of its high oxidation potential (2.07   V). However, slow ozone gas–liquid mass transfer results in high ozone requirements and operating costs. Micro-bubble aeration can effectively increase the ozone mass transfer efficiency while reducing ozone dose. Here, we used a ceramic ultrafiltration membrane for ozone micro-bubble aeration. The disinfection performance and mechanism of ozone micro-bubble aeration towards pathogenic microorganisms were studied. Micro-bubble aeration reduced the total ozone dose by > 60% for 6-log inactivation of Escherichia coli and MS2 coliphage. It also improved the disinfection efficiencies for Gram-positive bacteria by 3-log. Both ozone and • OH oxidation was enhanced via micro-bubble aeration because of efficient gas–liquid transfer. The equilibrium aquatic ozone concentration increased by 1.38 times and the • OH yield increased by 2.40 times compared with those with milli-bubble aeration. Consequently, ozone micro-bubble aeration caused severe membrane damage to bacterial cells and fragmented the bacterial DNA, which caused a rapid decrease in the bacterial metabolic activity (> 80%). This study demonstrates that ozone micro-bubble aeration can boost broad spectrum disinfection and effectively reduce the ozone dose, which will facilitate the application of ozonation with a lower cost and reduced environmental impact.