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The biofilms generated in a fire extinguishing water supply system can cause corrosion and a reduction in the water supply capacity; thus, degrading the system performance. To mitigate microbial corrosion, appropriate disinfection measures are necessary. In this study, the secondary addition of chlorine is employed to investigate the kinetics of chlorine decay, and shock disinfection is applied to investigate the removal efficiency of corrosion bacteria, and the microbial composition of a biofilm on the pipe wall was also clarified. The results show that the residual chlorine content in the secondary chlorination process was directly correlated with the decay rate of residual chlorine and the corrosion rate of the pipe wall. Additionally, the chlorine impact disinfection method could reduce the electrochemical corrosion phenomenon of the pipe wall. When the concentration of chlorine was 3 mg/L, the removal rate of corrosion bacteria was higher in 60 min than in 30 min. Specifically, most of the bacteria were inactivated in 60 min and the biofilm was severely damaged. Shock disinfection could significantly inactivate all microflora in the biofilm; the relative abundances of microflora varied significantly, while the change of microflora at the phylum level was insignificant. This study can provide theoretical support for the secondary addition of chlorine and shock disinfection in a fire extinguishing water supply system.

The biofilms generated in a fire extinguishing water supply system can cause corrosion and a reduction in the water supply capacity; thus, degrading the system performance. To mitigate microbial corrosion, appropriate disinfection measures are necessary. In this study, the secondary addition of chlorine is employed to investigate the kinetics of chlorine decay, and shock disinfection is applied to investigate the removal efficiency of corrosion bacteria, and the microbial composition of a biofilm on the pipe wall was also clarified. The results show that the residual chlorine content in the secondary chlorination process was directly correlated with the decay rate of residual chlorine and the corrosion rate of the pipe wall. Additionally, the chlorine impact disinfection method could reduce the electrochemical corrosion phenomenon of the pipe wall. When the concentration of chlorine was 3 mg/L, the removal rate of corrosion bacteria was higher in 60 min than in 30 min. Specifically, most of the bacteria were inactivated in 60 min and the biofilm was severely damaged. Shock disinfection could significantly inactivate all microflora in the biofilm; the relative abundances of microflora varied significantly, while the change of microflora at the phylum level was insignificant. This study can provide theoretical support for the secondary addition of chlorine and shock disinfection in a fire extinguishing water supply system. [ABSTRACT FROM AUTHOR]