Water and air ozone treatment as an alternative sanitizing technology

Aims. We investigated the effectiveness of ozone (aqueous and gaseous) treatment as an alternative sanitizing technology to common conventional disinfectants in reducing the microbial contamination of both water and air. Methods. Ozone was added for 20 minutes to a well-defined volume of water and air by the system named "Ozonomatic®". The effectiveness of ozonation was determined by counting CFU/m3 or ml of bacteria present in samples of air or water collected before (T0) and after (T1) the addition of ozone and comparing the microbial load of different bacteria present in ozonized and non-ozonized samples. Results. When the ozonisation equipment was located at 30 cm from the surface of the water in the bath tub in which the bacteria investigated were inoculated, the treatment was able to reduce the total microbial load present in the aerosol by 70.4% at a temperature of 36°C for 48 hours. Conversely, at 22°C for 5 days, only a modest decrease (9.1%) was observed. Escherichia coli and Pseudomonas aeruginosa were completely eliminated. A 93.9% reduction was observed for Staphylococcus aureus, followed by Streptococcus faecalis (25.9%). The addition of ozone to water was able to almost eliminate Staphylococcus aureus (98.9% reduction) and also to exert a strong impact on Legionella pneumophila (87.5% reduction). Streptococcus faecalis and Pseudomonas aeruginosa showed a decrease of 64.2% and 57.4%, respectively. Conversely, only a 26.4% reduction was observed for the bacterium Escherichia coli. This study showed that the addition of ozone in the air exerted a modest reduction on microbial load at 36°C, whereas no effect was observed at 22°C. Conclusions. Aqueous and gaseous ozone treatments were effective against microbial contaminants, reducing the CFU of the microorganisms studied. These results confirm the efficacy of the ozone disinfection treatment of both water and air; particularly, it constitutes an extremely promising alternative, allowing the possibility to reuse contaminated water