Florida Wastewater Practice Test

What formula defines chlorine demand?

1. Supply + Residual = Demand

2. Supply - Residual = Demand

3. Residual / Supply = Demand

4. Demand - Supply = Residual

The correct answer is: Supply - Residual = Demand

Chlorine demand is defined as the amount of chlorine that is consumed by the wastewater before any residual chlorine can be detected. To quantify this, the formula that accurately represents the relationship between chlorine supply, residual chlorine, and demand is Supply - Residual = Demand. In practical terms, the supply of chlorine refers to the total amount introduced to the system, while the residual chlorine is the amount remaining after it has reacted with the substances in the water, such as organic matter, bacteria, and other contaminants. By subtracting the residual from the supply, you isolate the chlorine that has been consumed, thereby providing the chlorine demand. Understanding this concept is essential for effective wastewater treatment management and ensuring proper disinfection levels are achieved.