Wastewater New York State Practice Exam

How does temperature affect the disinfection efficacy of chlorine?

1. Increases with temperature

2. Decreases with temperature

3. Remains unaffected by temperature

4. Fluctuates based on pH

The correct answer is: Decreases with temperature

The correct response highlights that disinfection efficacy of chlorine decreases with an increase in temperature. Chlorine is a powerful disinfectant used in wastewater treatment to kill pathogens. However, as the temperature rises, the reactivity of chlorine can lead to the formation of chlorinated byproducts, which are often less effective at disinfection. Higher temperatures can also accelerate the rate of evaporation of chlorine, reducing its concentration in the water and ultimately diminishing its disinfecting capability. While it might seem intuitive that higher temperatures could enhance the activity of chlorine, the reality is that the formation of additional compounds and the decrease in available active chlorine result in reduced efficacy. Understanding how temperature impacts chlorine's performance is crucial for wastewater treatment operators seeking to maintain effective disinfection practices.