What is the general purpose of a disinfectant residual map?

• A. To monitor weather effects on disinfection chemicals.
• B. To compare energy use of different disinfectants.
• C. To track residual disinfectant levels across the distribution system ensuring adequate protection.
• D. To locate the nearest disinfection facility.

Answer: (C)

A disinfectant residual map visualizes the levels of disinfectant still present at multiple points throughout the water distribution network. The general purpose is to track these residual disinfectant levels across the system to ensure adequate protection against microbial contamination. By displaying where chlorine (or another disinfectant) remains above the minimum required levels, operators can quickly spot zones with too-low residuals, which could allow microbial growth, and take timely actions such as flushing, adjusting booster stations, or modifying hydraulics to restore adequate disinfection. It also helps identify stagnant or low-flow areas and supports trend tracking over time to maintain safety and regulatory compliance. This tool isn’t about weather effects, energy use, or locating facilities; it’s focused on verifying and maintaining safe disinfection throughout the distribution system.