What does CT99.9 refer to in water treatment?

CT99.9 specifically pertains to the CT value necessary for achieving 99.9 percent inactivation of Giardia lamblia cysts in water treatment processes. The CT value is a critical measurement that combines the concentration of a disinfectant (such as chlorine) and the contact time with the water being treated. This value ensures that water treatment facilities can effectively reduce pathogen levels to meet safety standards.

This specific CT value is essential since Giardia lamblia, a protozoan parasite that can cause gastrointestinal illness, requires a distinct CT value that differs from other pathogens, like E. coli. The focus on 99.9 percent inactivation highlights the rigorous standards that are often required to prevent potential outbreaks and safeguard public health.

Other options refer to different aspects of disinfection or target pathogens, but they do not correctly define the CT99.9 designation pertaining to Giardia lamblia. This emphasizes the importance of understanding which CT values apply to specific pathogens during water treatment planning and operations.