Water Treatment Operator-in-Training (OIT) Practice Test

Why is chlorine residual useful in water systems?

1. It provides a sweet taste to water

2. It provides disinfecting ability after the chlorine is added

3. It enhances the color of the water

4. It acts as a nutrient for bacteria

The correct answer is: It provides disinfecting ability after the chlorine is added

Chlorine residual is significant in water systems primarily because it provides disinfecting ability after the chlorine is added. This residual is the amount of chlorine that remains in the water after treatment, ensuring that the water remains safe for consumption over time. By maintaining a certain level of chlorine residual, water treatment facilities can protect against harmful pathogens that may enter the water supply after initial treatment. The presence of chlorine residual helps to kill bacteria, viruses, and other microorganisms, thus serving as a safeguard for public health. The other options do not accurately reflect the role of chlorine residual in water systems. While chlorine does contribute to water quality, it does not enhance the color or function as a nutrient for bacteria, as those would lead to adverse effects in water quality. Additionally, chlorine does not provide a sweet taste; rather, its primary function is as a disinfectant.