Under the Surface Water Treatment Rule, where must disinfection residuals be collected?

• A. At the water treatment facility
• B. In the distribution system at the same location as coliform samples
• C. At the consumer's tap
• D. Only at high-risk areas of the distribution system

Answer: (B)

The requirement to collect disinfection residuals in the distribution system at the same location as coliform samples stems from the need to ensure the water quality is maintained throughout the distribution network. This practice allows for an accurate assessment of both the presence of coliform bacteria and the effectiveness of disinfection processes. By monitoring disinfection residuals at these locations, water utilities can verify that the water remains safe and meets regulatory standards as it travels to consumers.

Collecting residuals at the water treatment facility would measure only the effectiveness of disinfection at the source and may not account for any changes or reduction in residual levels that might occur as the water travels through the distribution system. Meanwhile, collecting at the consumer's tap, while helpful for assessing water quality at the point of use, would not provide consistent data across the entire system. Lastly, restricting residual measurement to only high-risk areas of the distribution system fails to provide a comprehensive overview of water quality across the entire system, which is crucial for maintaining public health. Thus, sampling at the same locations as coliform samples strikes the right balance to ensure ongoing safety and compliance throughout the distribution network.