Which measurement is used to assess disinfectant levels in shipboard potable water?

• A. Free available chlorine
• B. Total Bromine Residual
• C. pH level
• D. Water temperature

Answer: (A)

Disinfection level is assessed by measuring the free available chlorine in the water. This value represents the portion of chlorine that remains active and capable of killing microorganisms as water travels through the ship’s potable-water system. Keeping a small, detectable residual—typically around 0.2 to 0.5 mg/L in many shipboard systems—ensures ongoing protection against microbial growth and contamination.

The other factors—bromine residual, pH, and temperature—play roles in how effectively chlorine works, or describe different properties of the water, but they do not directly measure the amount of active disinfectant present. Bromine residual would be used if bromine were the disinfectant, while pH and temperature influence disinfection efficiency rather than indicating the actual chlorine level.