What range of disinfectant residual has been observed at the public water supply point of entry?

The correct response highlights that the typical range of disinfectant residual observed at the public water supply point of entry is between 0 to 0.2 parts per million. This level is considered essential for maintaining water safety and preventing the growth of pathogenic microorganisms, including Legionella.

Disinfectant residual is crucial as it indicates the effectiveness of the water treatment process in preventing biological contamination as water moves through distribution systems. Levels above a certain threshold can be effective in minimizing microbial growth, while levels that are too low may not provide sufficient protection.

Research and guidelines from organizations focused on water quality management typically reference this range, helping to inform practices regarding regular monitoring and maintenance of water systems to ensure safety and compliance with health standards.