The term used for the amount of chlorine injected into water until the demand is satisfied is known as:

The concept of "breakpoint" refers to the specific point at which chlorine is added to water, and all chlorine is utilized to satisfy the chlorine demand before any residual chlorine is detected. During water treatment, chlorine is typically injected to achieve disinfection. However, the initial chlorine serves to address both the pathogens and organic matter in the water, consuming the chlorine in the process.

Once the chlorine demand (which includes both the amount needed to react with contaminants and to maintain a desired level of disinfection) is met, additional chlorine begins to form a residual level in the water. The "breakpoint" is critical in water treatment because it signifies the moment all reactive substances are neutralized, and any further chlorine becomes effective for disinfection, resulting in measurable residual chlorine. This is essential for ensuring that treated water remains safe for distribution and consumption.

Understanding breakpoint is vital for water treatment operators to ensure that sufficient chlorine is injected to not only fulfill the demand but also to provide safe and clean drinking water.