Tennessee Wastewater Operator Practice Exam

Why is chlorine often applied directly to nocardia foam instead of the RAS line?

1. To improve disinfection

2. To control odors

3. Filaments concentrate in the foam

4. To enhance settling properties

The correct answer is: Filaments concentrate in the foam

Chlorine is applied directly to nocardia foam primarily because filaments concentrate in the foam. Nocardia species are filamentous bacteria that can form large clumps or foam in activated sludge treatment processes. By targeting the foam directly, operators can effectively manage the population of these filamentous organisms. When chlorine is applied to the foam, it helps to break down or inactivate these filaments, which can lead to improved treatment performance and reduced foaming issues in the system. If chlorine were introduced into the Return Activated Sludge (RAS) line, it might not only be less effective due to dilution and distribution issues but could also adversely affect the overall bacterial population in the system, including beneficial microorganisms essential for wastewater treatment. Therefore, direct application to the foam is a more strategic approach to specifically address the problem of excess nocardia and its associated fouling.