The amount of chlorine in mg/L that is used up by reactions with organics and inorganics is called:

The term that refers to the amount of chlorine in mg/L that is consumed by reactions with organic and inorganic substances is known as demand. This concept is crucial in water treatment processes, especially in understanding how much chlorine is initially required to effectively disinfect the water.

When chlorine is added to water, not all of it will remain available for disinfection; some of it will react with impurities, including organic materials, bacteria, and other substances present in the water. This reaction effectively "consumes" the chlorine, which means that the amount of chlorine used up in these reactions defines the chlorine demand.

Understanding demand is critical for water operators because it impacts the final concentration of free chlorine available in the water after treatment. It helps ensure that sufficient chlorine is dosed to not only meet the disinfection needs but also account for those reactions that consume chlorine. This guarantees that the water leaving the treatment facility has adequate disinfectant residual for ongoing protection against pathogens as it moves through the distribution system.