Synergistic bactericidal activity of ultraviolet radiation, ozone, and liquid-thin-film technology against Escherichia coli in water

Abstract

Abstract Providing effective and sustainable water disinfection methods, without harmful by-products, is essential to protect public health and safety. It is hypothesized that the application of liquid-thin-film (LTF) technology can enhance the bactericidal activity of both ultraviolet (UV) irradiation and ozone (O3) treatments. Therefore, this study aimed to examine the bactericidal activity and synergistic effect of the combined UV + O3 + LTF treatment against Escherichia coli in water processing. The results showed that LTF technology significantly increased the disinfection efficiency of UV and O3 in potable water production. Thus, the combined UV + LTF, O3 + LTF, and UV + O3 + LTF treatments were more effective than the individual treatments under identical conditions. Particularly, the combined double-UV (41.7 mJ cm−2) + O3 (100% O3) + LTF (65 L min−1) treatment exhibited the highest bactericidal activity, resulting in a 5.8-log decrease in the E. coli load within 30 min. Pearson's correlation analysis demonstrated a significant correlation between the synergistic effects of the combined treatments and UV dosage (r = 0.88, p < 0.0001) and aqueous O3 concentrations (r = 0.84, p < 0.0001). These findings suggest that combined UV + O3 + LTF treatment could be a viable alternative method for water disinfection.