What defines chlorine demand in wastewater treatment?

Chlorine demand in wastewater treatment is defined as the difference between the dose of chlorine that is added to the wastewater and the residual concentration of chlorine that remains after the treatment process. This measurement indicates how much chlorine has been consumed by various substances in the wastewater, such as organic matter, ammonia, and other pollutants.

When chlorine is added to wastewater, it reacts with contaminants present in the water, leading to a decrease in the amount of chlorine that remains in the effluent. The residual concentration reflects the effective dose of chlorine that remains after these reactions have taken place. Understanding chlorine demand is critical for wastewater treatment operators, as it informs them about the efficiency of disinfection processes and helps in determining the appropriate amounts of chlorine to achieve desired disinfection without excessive chemical use.

In contrast, the other options refer to different concepts. The volume of chlorine added to the system does not account for the amount consumed, while the concentration of chlorine in the effluent does not provide insight into the demand. Similarly, the capacity of chlorine to neutralize contaminants indicates potential interactions but doesn’t define the total consumption in terms of demand. Thus, the concept of demand is particularly focused on the balance between what is added and what remains active in the system.