Generation of ozone foam and its application for disinfection^*

¹ OHNIT Co., Ltd. 3-765, 3 Sakuragaoka-higashi, Akaiwa-city, Okayama 709-0721 Japan
² Saga University, 1 Honjo-machi, Saga 840-8502, Japan

^a e-mail: yamabec@cc.saga-u.ac.jp

Received: 23 December 2014
Revised: 10 February 2015
Accepted: 4 March 2015
Published online: 15 July 2015

Abstract

Generated ozone foam was applied to the disinfection of Pseudomonas fluorescens. The effect of disinfection has been confirmed experimentally and new equipment for the disinfection of hands using this ozone foam has been put on the market for the practical use. The ozone foam was produced in the foam generator after mixing the water including surfactant (30 mL/min) and air including ozone (1000 ppm = 2.14 g/m³ ~ 1600 ppm = 3.4 g/m³, 300 mL/min). The liquid-to-gas ratio is 100 L/m³. The concentration of dissolved ozone in the thin liquid films of the bubbles was about 3 mg/L which was measured by the chemical method of the KI absorption and titration of sodium thiosulfate solution. The disinfection test samples were prepared using the PET disk on which Pseudomonas fluorescens of its number of more than 10⁸ were attached. Test sample was inserted into ozone foam set on the glass plate for one to 6 min. The survival rate log (N/N₀ decreased with time and its value of about−2.6 (i.e., ~1/400) was obtained at 6 min (2 min × 3 times repeated). It was also confirmed that the ozone foam was useful for the disinfection of hands. For more effective disinfection (in case of taking a long time for foam melting), the ozone foam was broken by force and changed into ozone water by which the survival rate decreased ×4 (i.e., N/N₀ = 1/10 000) at 4 ~ 6 min.