What is the CT value?

What is the CT value?

• A. The disinfectant's contact time in minutes
• B. The residual concentration of a given disinfectant in mg/L minus the disinfectant's contact time in minutes
• C. The residual concentration of a given disinfectant in mg/L
• D. The residual concentration of a given disinfectant in mg/L times the disinfectant's contact time in minutes

Answer: (D)

CT value is the exposure of microorganisms to disinfectant, defined as the product of the residual disinfectant concentration (mg/L) and the contact time (minutes). This gives units of mg·min/L and reflects how much disinfectant exposure occurs, since inactivation depends on both how strong the disinfectant is and how long microbes are in contact with it. For example, 2 mg/L of chlorine for 15 minutes yields a CT of 30 mg·min/L. Regulations or guidelines specify a required CT under certain conditions, and meeting or exceeding that CT ensures effective disinfection.

CT value is the exposure of microorganisms to disinfectant, defined as the product of the residual disinfectant concentration (mg/L) and the contact time (minutes). This gives units of mg·min/L and reflects how much disinfectant exposure occurs, since inactivation depends on both how strong the disinfectant is and how long microbes are in contact with it. For example, 2 mg/L of chlorine for 15 minutes yields a CT of 30 mg·min/L. Regulations or guidelines specify a required CT under certain conditions, and meeting or exceeding that CT ensures effective disinfection.