What is the minimum free chlorine residual required at the far reaches of a water system?

The correct response is based on regulations that stipulate minimum free chlorine residuals needed to ensure adequate disinfection throughout a water distribution system. A minimum free chlorine residual of 0.2 mg/L at the far reaches of a water system is established to maintain a sufficient level of disinfection and to mitigate the risk of microbiological contamination. This level is particularly important in ensuring that the water remains safe during transit to consumers.

This requirement is crucial because chlorine acts as a disinfectant, helping to kill or inactivate harmful microorganisms, which is vital for public health. While higher residual levels can be beneficial in areas with longer travel times or larger distribution systems, the key requirement is ensuring that at least 0.2 mg/L is present at the most distant points in the system to maintain safety and compliance with health standards.