What is breakpoint chlorination?

Breakpoint chlorination refers to the process of adding chlorine to water until the chlorine demand has been satisfied. This is significant because water often contains organic matter and other substances that consume chlorine, termed "chlorine demand." Until the chlorine demand is met, any additional chlorine added does not contribute to disinfection. Once breakpoint is reached, further addition of chlorine produces a rapid increase in free chlorine residual, which effectively disinfects the water by killing pathogens.

This method is crucial for ensuring that the water is adequately treated and safe for consumption, as it confirms the presence of an effective concentration of free chlorine in the water following the chemical reactions needed to address the chlorine demand. This understanding is essential for water treatment operators in managing water quality and ensuring public health safety.

The other options do not accurately describe breakpoint chlorination. The process of removing all pathogens from water is a broader concept of disinfection rather than a specific definition associated with breakpoint chlorination. Instantaneous addition of chlorine at the water treatment plant might occur, but it does not specify the critical aspect of meeting chlorine demand before free chlorine can be utilized for disinfection. Lastly, mixing chlorine with other chemicals for enhanced disinfection does not specifically address the hallmark of breakpoint chlorination which focuses on managing chlorine demand and