What is the hold time for residual chlorine samples?

The hold time for residual chlorine samples is 15 minutes because chlorine is a highly reactive substance that can dissipate quickly, especially when exposed to light or air. This short hold time is crucial in ensuring that the chlorine concentration measured in the sample accurately reflects the actual levels present in the water at the time of sampling. Any delay beyond this period may result in a significant decrease in chlorine levels due to its tendency to react with organic material or escape into the atmosphere, which could lead to misleading results when assessing water quality. Maintaining this strict time frame helps ensure that analyses provide reliable data for evaluating the efficiency of disinfection processes in wastewater treatment.