Which of the following is true about the effectiveness of chlorine?

Which of the following is true about the effectiveness of chlorine?

• A. The higher the pH, the better the disinfection with chlorine
• B. Chlorine is the most effective at pH=10
• C. The lower the pH, the better the disinfection with chlorine
• D. Chlorine is the most effective at pH=12

Answer: (C)

Chlorine's effectiveness as a disinfectant is highly dependent on the pH of the water being treated. At lower pH levels, chlorine exists primarily in its hypochlorous acid form (HOCl), which is a more effective germicide compared to its ionized form, hypochlorite ion (OCl-), that predominates in higher pH levels. As the pH increases, the equilibrium shifts in favor of the hypochlorite ion, which has a lower disinfection capability. Therefore, maintaining a lower pH is essential for optimizing chlorine-based disinfection processes. This is why the statement about the lower pH ensuring better disinfection with chlorine is accurate. It underscores the importance of controlling water pH levels for effective chlorination in water treatment systems. Understanding this principle is crucial for water distribution operators, as it informs them about the conditions necessary to achieve maximum disinfection efficiency in the treatment of drinking water.

Chlorine's effectiveness as a disinfectant is highly dependent on the pH of the water being treated. At lower pH levels, chlorine exists primarily in its hypochlorous acid form (HOCl), which is a more effective germicide compared to its ionized form, hypochlorite ion (OCl-), that predominates in higher pH levels.

As the pH increases, the equilibrium shifts in favor of the hypochlorite ion, which has a lower disinfection capability. Therefore, maintaining a lower pH is essential for optimizing chlorine-based disinfection processes. This is why the statement about the lower pH ensuring better disinfection with chlorine is accurate. It underscores the importance of controlling water pH levels for effective chlorination in water treatment systems.

Understanding this principle is crucial for water distribution operators, as it informs them about the conditions necessary to achieve maximum disinfection efficiency in the treatment of drinking water.