Tennessee Wastewater Operator Practice Exam

What factor plays a significant role in the efficiency of chlorine disinfection?

1. pH levels

2. Chlorine concentration

3. Contact time

4. All of the above

The correct answer is: All of the above

In the context of chlorine disinfection, each factor mentioned—pH levels, chlorine concentration, and contact time—plays a crucial role, making the comprehensive answer inclusive of all these elements. The pH levels in the water influence the form of chlorine that is present, affecting its disinfection efficacy. As the pH rises, the effectiveness of chlorine decreases because more chlorine exists in the less effective hypochlorite form rather than the more active hypochlorous acid form. Chlorine concentration is also vital; higher concentrations generally lead to more effective disinfection. However, there is a balance to be struck since excessively high concentrations can lead to harmful byproducts and potential toxicity. Contact time refers to the duration that chlorine needs to be in contact with the water to effectively inactivate pathogens. Insufficient contact time can result in inadequate disinfection, as chlorine needs time to react with and kill microorganisms. Since the efficient performance of chlorine disinfection is dependent on the interaction of all three factors, the correct answer reflects the importance of understanding and controlling each of these variables in the disinfection process.