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A number of pathogens of interest are susceptible to chlorine, including E. coli and Pseudomonas aeruginosa. Various studies have shown that they can be successfully deactivated following contact with chlorine for a short period of time. CT (disinfection concentration multiplied by the contact time) values for chlorine disinfection of pathogens of concern are shown in Table 2 together with resulting disinfection times expected at common swimming pool chlorine concentrations of 1–2 mg/L.

Table 2

Chlorine CT values for common pathogens in swimming pool environments

PathogenChlorine CT value (mg min/L)Disinfection time in pool conditionsSource
E. coli O157 0.04 1–2 seconds WHO (2004)  
Viruses 1.5–3 minutes AwwaRF (2004)  
Giardia 25 12.5–25 minutes WHO (2004)  
Cryptosporidium parvum 15,300 5–10 days Shields et al. (2008)  
PathogenChlorine CT value (mg min/L)Disinfection time in pool conditionsSource
E. coli O157 0.04 1–2 seconds WHO (2004)  
Viruses 1.5–3 minutes AwwaRF (2004)  
Giardia 25 12.5–25 minutes WHO (2004)  
Cryptosporidium parvum 15,300 5–10 days Shields et al. (2008)  

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