Basic Wastewater Operator Practice Exam

Which condition is likely to consume the most chlorine during treatment?

1. Low organic content

2. High organic content

3. Stable temperature

4. Stable pH

The correct answer is: High organic content

High organic content in wastewater is likely to consume the most chlorine during treatment because chlorine acts as a disinfectant that not only kills pathogens but also reacts with organic materials present in the wastewater. When wastewater contains a significant amount of organic material, chlorine has a greater demand, meaning more of it will be used up in reaction with these substances rather than being available for disinfection. In scenarios with low organic content, the chlorine demand is reduced since there are fewer organic compounds to react with, allowing more of the chlorine to remain effective for disinfecting pathogens. Stable temperature and stable pH conditions can influence the efficiency of chlorine disinfection but do not directly relate to the organic content in wastewater and, therefore, do not significantly impact chlorine consumption in the same way that high organic levels do.