What is the required contact time for free chlorine residuals to react completely?

The required contact time for free chlorine residuals to react completely is indeed 10 minutes. This timeframe is significant because it ensures that the chlorine has adequate time to effectively disinfect water by breaking down pathogens and organic materials present. The contact time needed can vary depending on factors like the initial concentration of chlorine, temperature, and the presence of other substances in the water.

In water treatment operations, achieving the right contact time is crucial for ensuring that disinfection is both effective and efficient. Insufficient contact time may lead to incomplete reactions, resulting in inadequate disinfection, which can compromise water safety. Therefore, understanding that 10 minutes is the standard required contact time for free chlorine allows operators to ensure effective treatment and compliance with safety standards.