Tennessee Wastewater Operator Practice Exam

What effect does adding ferric chloride to the influent for odor control have on primary sludge production?

1. It decreases sludge volume

2. It has no effect on sludge production

3. It increases primary sludge production

4. It improves sludge stability

The correct answer is: It increases primary sludge production

Adding ferric chloride to the influent for odor control tends to increase primary sludge production. Ferric chloride acts as a coagulating agent, which helps in the aggregation of suspended solids and increases the removal efficiency of organic matter. This results in a higher concentration of solids in the effluent treatment process, which ultimately translates to an increase in the volume of primary sludge generated. This increase in primary sludge production occurs because the chemical reactions initiated by ferric chloride can enhance the precipitation of organic solids. As more particulate matter is formed and stabilized by the ferric chloride, there is a corresponding rise in the quantity of sludge produced during the primary treatment phase. Therefore, recognizing the role of ferric chloride in promoting coagulation and improving solid separation efficiency is key to understanding its impact on sludge production. In the context of this process, it becomes clear that ferric chloride not only serves the purpose of odor control but also influences the overall dynamics of the sludge generation in wastewater treatment systems.