Which operation must be continuously monitored every 5 minutes in water treatment facilities?

Free chlorine levels must be continuously monitored every 5 minutes in water treatment facilities because maintaining appropriate levels of free chlorine is crucial for effective disinfection. Free chlorine is the form of chlorine that is available to kill bacteria and other pathogens in the water. Regular monitoring ensures that disinfection processes are effective in reducing microbial contamination and that the water remains safe for public consumption.

In contrast, while water hardness, pH, and temperature are also important parameters in water treatment, they do not require such frequent monitoring. Water hardness can be tested less frequently, as it tends to remain relatively stable, and significant changes in pH levels, although important, do not occur as rapidly as fluctuations in chlorine levels. Water temperature is important for treatment processes and can influence disinfection, but it also does not typically require minute-to-minute tracking unless specific conditions necessitate such close monitoring.