Tennessee Wastewater Operator Practice Exam

Which two chemicals can be added to activated sludge to help control filamentous organisms?

1. Chlorine and PACI

2. Sodium hypochlorite and Ferric chloride

3. Alum and Lime

4. Hydrogen peroxide and Chlorine

The correct answer is: Chlorine and PACI

The correct answer involves understanding the role of the chemicals in managing filamentous organisms within activated sludge systems. Chlorine is a strong oxidizing agent that can be used to control filamentous bacteria effectively by disinfection and oxidation. It reduces the population of unwanted filamentous organisms without disrupting the entirety of the activated sludge process. PACI (Poly Aluminum Chloride) is an aluminum-based coagulant, and it can help in aiding the settling of flocs and minimization of filamentous organisms through the enhancement of flocculation, promoting better settling characteristics. In combination, chlorine and PACI work synergistically to target filamentous growth effectively while maintaining overall system performance, leading to improved treatment efficiency and effluent quality. When considering the other options, sodium hypochlorite and ferric chloride, alum and lime, and hydrogen peroxide and chlorine do not combine effectively to specifically address the control of filamentous organisms in the same manner as chlorine and PACI. While some of these chemicals may have uses in wastewater treatment, they do not provide the targeted, dual action that is needed for controlling filamentous organisms in activated sludge systems.