Florida Wastewater Practice Test

What happens to the chlorine residual when the organic content in the effluent increases?

1. The residual goes up

2. The residual stays the same

3. The residual goes down

4. The residual is eliminated

The correct answer is: The residual goes down

When the organic content in the effluent increases, the chlorine residual typically goes down due to the reaction between chlorine and the organic materials present in the wastewater. Chlorine is a powerful disinfectant, but it also reacts with various organic compounds through a process known as chlorine demand. As the organic load increases, more chlorine is consumed during these reactions, which reduces the amount of free chlorine available as a residual in the effluent. This reduction in chlorine residual is significant because it impacts the effectiveness of disinfection processes and requires careful monitoring and adjustment of chlorine dosing to ensure adequate disinfection throughout the wastewater treatment process. Therefore, an increase in organic content directly leads to a lower chlorine residual, emphasizing the need for operators to manage chemical dosing based on changes in wastewater composition.