What is one of the main goals of the secondary treatment stage in wastewater treatment?

One of the primary objectives of the secondary treatment stage in wastewater treatment is to further reduce biochemical oxygen demand (BOD) and suspended solids. This stage primarily involves biological processes where microorganisms break down organic matter present in the wastewater. By doing this, the secondary treatment aims to significantly lower the concentrations of BOD, which measures the amount of oxygen that bacteria will consume while decomposing organic matter, and suspended solids, which consist of particles that can interfere with the treatment process and lead to water quality issues.

The success of secondary treatment is crucial because it enhances the overall quality of the effluent water, making it safer for discharge into the environment and more suitable for potential reuse applications. This reduction in BOD and suspended solids is key to preventing pollution and protecting aquatic ecosystems.

In contrast, while reducing sludge volume is important overall, it is not the main goal of secondary treatment specifically. The removal of heavy metals is typically addressed in different processes, and pre-treatment usually refers to the initial stages of wastewater treatment before primary treatment occurs. Therefore, the focus on reducing BOD and suspended solids accurately captures the essence of the goals of secondary treatment.