Which of the following components is NOT typically found in activated sludge systems?

In an activated sludge system, the primary objective is to treat wastewater through biological processes involving microorganisms. The key components of this system are designed to facilitate aeration, biological treatment, and separation of treated water from the biological solids.

The aeration tank is where the actual biological treatment occurs. It provides an environment for the microorganisms to thrive, to break down organic matter in the wastewater through aerobic digestion.

The clarifier, also known as a secondary clarifier, is essential for separating the activated sludge (the biomass containing microorganisms) from the treated water after aeration. This separation process allows for the recovery of solids, which can be returned to the aeration tank as return activated sludge, maintaining the necessary concentration of microorganisms for efficient treatment.

Return activated sludge (RAS) is a portion of the settled sludge returned from the clarifier to the aeration tank. This practice is crucial as it ensures that a sufficient amount of microorganisms is present in the aeration tank to maintain effective treatment of incoming wastewater.

While filtration units can be part of wastewater treatment processes, they are not standard components specifically within the activated sludge system. Filtration may be utilized in other parts of a treatment plant, such as after clarification or in advanced treatment systems, but it's not integral to