"Legionella" control by chlorine dioxide in hospital water systems

This study evaluated the safety and efficacy of chlorine dioxide (ClO2) fed into the incoming main water line to control Legionella bacteria in two hospital water systems. In both hospitals A and B, positivity of all distal outlets (sinks and showers) for Legionella decreased from 60% to ≤ 10% after the ClO2 treatment. In hospital B, the heterotrophic plate count bacteria in hot water were reduced from 15,400 cfu/mL to 2,900 cfu/mL after ClO2 treatment. Mean concentrations of ClO2 and chlorite (ClO2 ‐) in cold and hot water did not exceed the maximum residual disinfection level of 0.8 mg/L and the maximum contaminant level of 1.0 mg/L, respectively. No cases of healthcare acquired legionellosis have been identified in the postdisinfection period in these two hospitals. The study indicates that ClO2 is a promising disinfectant for controlling not only Legionella, but also other microorganisms in drinking water