At what temperature is chlorine most effective in water sanitation?

Chlorine's effectiveness as a disinfectant in water sanitation relies significantly on temperature, pH, and contact time. The correct answer is rooted in the fact that chlorine is most effective at higher temperatures due to increased kinetic energy and reactivity, which enhances its disinfection capability.

While various studies support that chlorine's disinfection efficiency improves with increasing temperatures, it generally shows optimal effectiveness in the range of approximately 80 to 90 degrees Fahrenheit. Therefore, while 78 degrees Fahrenheit is a reasonable temperature where chlorine can still perform effectively, it is slightly below the most effective range.

Temperature promotes faster chemical reactions, which in turn allows chlorine to break down pathogens more rapidly and efficiently. Thus, the 85 degrees Fahrenheit option represents a more optimal temperature where chlorine demonstrates its maximum level of disinfectant activity, making it the best choice for water sanitation.