Florida Drinking Water Operator "B" Practice Test

What can be done to neutralize chlorine in water before discharge?

1. Add baking soda

2. Add sulfur dioxide

3. Add potassium permanganate

4. Add calcium carbonate

The correct answer is: Add sulfur dioxide

To neutralize chlorine in water before discharge, sulfur dioxide is an effective chemical choice. When sulfur dioxide is added to chlorinated water, it reacts with chlorine to form sulfate and hydrochloric acid. This reaction effectively removes chlorine from the water, making it safe for discharge into the environment. This process is often used in large water treatment facilities as it is efficient and can be controlled to ensure complete neutralization of chlorine. The other options, while they may have various uses in water treatment, do not effectively neutralize chlorine. Baking soda is primarily used to adjust pH, not to neutralize chlorine. Potassium permanganate is a strong oxidizing agent and can actually lead to the chlorine being transformed into other chlorinated compounds rather than neutralizing it. Calcium carbonate is typically used to adjust the hardness of water and influence pH, but it does not neutralize chlorine. Therefore, sulfur dioxide stands out as the correct solution for the purpose of chlorine neutralization in this context.