Combined disinfection method of chlorite and chloramine in water distribution system

摘要

The present inventors have studied the control of bacterial biofilms composed of ammonia-oxidizing bacteria and heterotrophic bacteria when chlorite is continuously administered with or without chloramine. Chlorite and monochloramine were added to water and the pH was fixed at 9.0 to test whether the residual concentration for sterilization remained stable. (AOB concentration of biofilm was 6.8 ± 1.3 × 10 ² MPN / ㎠) when it was applied with chlorite alone or in combination with chlorite and monochloramine, it decreased to below detection limit level (0.6 MPN / ㎠). Biofilm AOBs were inactivated much faster when treated with the combination of chlorite-monochloramine than with chlorite alone. The treatment with chlorite only had no effect on the control of heterotrophic bacteria, but the treatment with chlorite and monochloramine showed significant disinfection effect on heterotrophic bacteria. The mean log lowering of HPC (heterotrophic plate counts) in the biofilm and water after the chlorite - monochloramine disinfection process was 2.8 ± 0.5 and 2.9 ± 0.3, respectively, compared with before disinfection. In conclusion, as an effective method for controlling bacterial biofilms consisting of AOB and heterotrophic bacteria in water pipes, the present inventors invented a method of disinfection of chlorite and monochloramine combination.