What is the maximum allowed free chlorine or chloramine residual as a running average in surface water systems?

The maximum allowed free chlorine or chloramine residual as a running average in surface water systems is 4 mg/L. This standard is established to ensure effective disinfection while minimizing potential adverse effects on human health and the environment. Free chlorine and chloramines are commonly used for water disinfection in surface water systems, and maintaining this level is crucial to prevent the growth of pathogens and to provide safe drinking water.

Using 4 mg/L as a threshold balances the need for disinfection with the potential for unpleasant tastes, odors, and possible negative effects on aquatic life if concentrations are too high. Monitoring the running average helps provide consistent disinfection levels while accounting for fluctuations in water quality that may occur due to changes in source water or treatment processes. This regulatory approach contributes to the overall safety and reliability of public water systems.