What level of residual chlorine indicates successful disinfection?

The level of residual chlorine that indicates successful disinfection is 0.5 mg/L. This concentration is recognized as sufficient to ensure effective pathogen reduction in water treatment processes. At this level, chlorine can effectively inactivate bacteria, viruses, and other microorganisms that may be present in the water, thereby contributing to safe water quality for consumption.

While lower concentrations of chlorine, such as 0.1 mg/L and 0.2 mg/L, may provide some degree of disinfection, they may not be adequate for reliable pathogen control across all conditions. 1.0 mg/L is higher than what is typically required for effective disinfection and may lead to undesirable tastes or odors in treated water. Therefore, 0.5 mg/L represents an optimal balance, ensuring sufficient disinfection without excessive chlorine residual that could negatively impact water quality.