Tennessee Wastewater Operator Practice Exam

A tertiary trickling filter placed after the secondary clarifier is primarily intended to remove which substance?

1. Nitrogen

2. Phosphorus

3. Ammonia

4. Suspended solids

The correct answer is: Ammonia

A tertiary trickling filter, positioned after the secondary clarifier in a wastewater treatment process, is primarily designed to remove ammonia. This stage of treatment focuses on further enhancing water quality by targeting nutrients and other specific compounds that may still be present after the secondary treatment. In this context, ammonia is a key substance because it often remains in the effluent after secondary biological treatment processes. Tertiary treatment aims to reduce ammonia levels to prevent negative impacts on receiving waters, where high ammonia concentrations can be toxic to aquatic life. The trickling filter works by providing a habitat for specialized microorganisms that specifically target and convert ammonia into less harmful substances, effectively improving the overall nitrogen removal from the wastewater. The other substances listed—nitrogen, phosphorus, and suspended solids—might also be addressed in various stages of wastewater treatment, but the tertiary trickling filter's primary function is significantly focused on ammonia reduction.