What is the minimum combined chlorine residual required in all parts of a distribution system?

The minimum combined chlorine residual required in all parts of a distribution system is established to ensure that the treated water remains safe for consumption and maintains its disinfection properties. A residual of 1.0 mg/l is considered adequate for maintaining effective disinfection throughout the distribution network. This level helps to prevent the regrowth of pathogens and ensures that the water remains safe as it moves from the treatment plant to consumers.

Maintaining a minimum combined chlorine residual is crucial because it indicates a continuous presence of chlorine in the system, which is essential for controlling bacteria and preventing waterborne illnesses. A value of 1.0 mg/l strikes a balance, providing sufficient disinfection without posing excessive risks to public health, such as taste and toxicity concerns, associated with higher chlorine levels. This makes it the standard practice in many regulations and guidelines for water quality management.

In contrasting levels, lower residuals may compromise disinfection effectiveness, while higher levels could lead to unpleasant tastes and potential health hazards from overexposure to chlorine, making 1.0 mg/l the optimal choice.