In terms of water treatment, what does "dose-residual" refer to?

The term "dose-residual" in water treatment refers to the amount of a chemical or treatment substance applied to the water (the "dose") and the amount that remains effective in the water after its initial application (the "residual").

When discussing water treatment, it is essential to ensure that the applied treatment, such as chlorine for disinfection, has an adequate residual level in the water to maintain its effectiveness throughout the distribution system. This allows for the killing of pathogens and helps in maintaining water quality as it travels through pipes.

In this context, the concept of "demand" is closely related because it represents the amount of treatment that is consumed or utilized by the water's natural organic matter and other substances present. The remaining amount, or the residual, indicates the effectiveness of the treatment in keeping the water safe from microbial contamination. Therefore, understanding the relationship between dose and residual is crucial to ensure that the water treatment process is functioning optimally and that the necessary residual amounts are achieved to protect public health.