What is described by stage 1 of the Chlorine Demand Curve?

Stage 1 of the Chlorine Demand Curve is characterized by the absence of any residual chlorine being formed in the water. During this initial phase, chlorine is added to the water, but it gets consumed by organic matter, ammonia, and other pollutants present in the water. Therefore, no residual chlorine remains because it is entirely used up to satisfy the chlorine demand of the water. This stage indicates that the water requires additional chlorine for effective disinfection; until all existing demands are met, the formation of a chlorine residual cannot occur.

Understanding the chlorine demand curve is crucial for water treatment professionals, as it highlights the importance of knowing how much chlorine is needed to achieve effective disinfection. It also informs decisions about the appropriate dosage of chlorine based on the water quality being treated.