For a public water system to comply with the MRDL, what is the requirement regarding annual averages?

The requirement for a public water system to comply with the Maximum Residual Disinfectant Level (MRDL) is that the annual averages must be less than or equal to the MRDL. This standard is established to ensure the safety and quality of drinking water by limiting the amount of disinfectant residuals that can be present in the water.

By keeping the annual average at or below the MRDL, water suppliers can help protect public health while still effectively disinfecting the water supply. If the average concentration exceeds the MRDL, it indicates that the water may pose a risk to health and is not compliant with regulatory standards. This approach helps to balance effective water treatment with the need to prevent potential harmful effects associated with higher levels of disinfectants.

Although monitoring frequency is important for maintaining compliance, it does not directly address the average levels required for MRDL compliance. The focus remains on maintaining levels that are protective of public health, keeping them within regulated limits.