What happens to biomass during secondary treatment processes?

During secondary treatment processes, biomass primarily consists of the microorganisms that break down organic matter in wastewater. Once the biological treatment phase is complete, a significant portion of this biomass settles out in the secondary clarifier.

The secondary clarifier functions by allowing the treated water to slow down, enabling the settling of solids, including the biomass. This separation is crucial for returning a portion of the settled biomass back to the biological treatment process (in a practice known as return activated sludge) while also removing excess biomass that is not needed, which is typically sent for further processing or disposal.

The settling process in the secondary clarifier plays a vital role in improving the overall efficiency of the wastewater treatment system by ensuring that the treated effluent has a low concentration of suspended solids, thus meeting discharge standards. Moreover, this step prevents unnecessary accumulation of biomass in the treatment system, which could lead to operational issues if not managed properly.