What does CT stand for in disinfection calculations, and what is it used for?

What does CT stand for in disinfection calculations, and what is it used for?

• A. It measures breakpoints in chlorine demand.
• B. C × T is the product used to verify inactivation of Giardia, viruses, and crypto.
• C. It is a measure of filtration rate.
• D. It relates to jar testing dosage.

Answer: (B)

CT is the exposure concept used in disinfection calculations. It stands for the product of the disinfectant concentration (C, in mg/L) and the contact time (T, in minutes). This product quantifies how much disinfectant exposure the pathogens receive. It is used to determine whether the water treatment process provides enough exposure to inactivate target organisms, such as Giardia, viruses, and cryptosporidium. In practice, you calculate CT for your system and compare it to the required CT for the given pathogen at your water’s pH and temperature. If the actual CT is at least as high as the required CT, the disinfection is expected to achieve the needed inactivation; if not, you adjust by increasing chlorine residual or increasing contact time. This concept is distinct from filtration rate, jar testing dosage, or chlorine demand breakpoints, which relate to other parts of treatment design.

CT is the exposure concept used in disinfection calculations. It stands for the product of the disinfectant concentration (C, in mg/L) and the contact time (T, in minutes). This product quantifies how much disinfectant exposure the pathogens receive. It is used to determine whether the water treatment process provides enough exposure to inactivate target organisms, such as Giardia, viruses, and cryptosporidium. In practice, you calculate CT for your system and compare it to the required CT for the given pathogen at your water’s pH and temperature. If the actual CT is at least as high as the required CT, the disinfection is expected to achieve the needed inactivation; if not, you adjust by increasing chlorine residual or increasing contact time. This concept is distinct from filtration rate, jar testing dosage, or chlorine demand breakpoints, which relate to other parts of treatment design.