Nanobubble water for the effective removal of biofilm formed by Escherichia coli.

The removal of biofilm (BF) formed by Escherichia coli using nanobubble (NB) water prepared with different gases and two generation methods was investigated. The E. coli BF removal efficiencies of all NB water samples tested were significantly higher than those of the non-NB water. In particular, nitrogen (N2) NB water exerted the greatest effect on the removal of E. coli BF. The surface tension of N2NB water was the lowest, although that of airNB water was the highest. The dissolved oxygen (O2) concentration in the O2NB water was drastically increased, although that in the N2NB and carbon dioxide (CO2) NB water was decreased. The pH of CO2NB water was significantly decreased, although that of N2NB, airNB, and O2NB water was increased. The E coli BF removal efficiencies of N2NB water were not different in the NB generators between ejector and shearing types. However, the surface tension, pH, and size distribution varied among the NB generator types. Therefore, it was found that NB water removed E. coli BF, and that its efficiencies differed depending on the gas type.