Wastewater Treatment Operator Certification Practice Test

What are commonly used to control chlorine feed rate for disinfection?

1. BOD and MLVSS

2. pH and temperature

3. Flow and chlorine residual

4. DO and TSS

The correct answer is: Flow and chlorine residual

The control of chlorine feed rate for disinfection is primarily influenced by the flow of water and the chlorine residual present in the system. Flow rate is critical because it dictates the volume of water being treated and therefore how much chlorine is required to achieve an effective level of disinfection. As the flow rate increases, more chlorine will be needed to ensure that the disinfectant has adequate contact time with pathogens before the water is discharged or reused. Chlorine residual, which refers to the amount of chlorine that remains in the water after disinfection has taken place, is also a key parameter. Monitoring residual levels ensures that sufficient chlorine is present to eliminate harmful microorganisms effectively. If residual levels are too low, it indicates that not enough chlorine is being fed; conversely, if levels are too high, adjustments can be made to avoid potential harmful effects on aquatic life and human health. While various factors such as pH, temperature, dissolved oxygen (DO), and total suspended solids (TSS) can impact disinfection efficiency, they do not directly control the rate of chlorine fed into the system as flow and chlorine residual do. Consequently, focusing on flow and chlorine residual provides operators with the necessary parameters to maintain effective disinfection practices.