What does a CT limit indicate in water treatment?

A CT limit in water treatment refers to the product of disinfectant concentration (C) and contact time (T) required for effective disinfection of pathogens in water. This means that the CT value provides a measure of how long and at what concentration a disinfectant, such as chlorine, needs to be maintained in contact with the water to achieve a specific level of microbial inactivation.

In practice, if the concentration of chlorine is lower, a longer contact time is necessary to achieve disinfection. Conversely, if the concentration is higher, less contact time might be sufficient. Therefore, the CT limit serves as a guideline for operators to ensure that water treatment processes are designed and managed effectively to ensure safe drinking water. This is crucial for protecting public health by preventing waterborne diseases.