What does secondary treatment in wastewater treatment aim to achieve?

Secondary treatment in wastewater treatment is primarily focused on the removal of dissolved and suspended organic matter from the effluent. This stage of treatment typically follows primary treatment, which mainly deals with the removal of larger solids and grit. During secondary treatment, biological processes are utilized, often involving microorganisms, to degrade the organic material present in the wastewater.

The effectiveness of this process is crucial because it significantly reduces the biochemical oxygen demand (BOD) of the wastewater. High BOD levels indicate a high concentration of organic matter, which can lead to oxygen depletion in receiving waters if released untreated. By efficiently breaking down these organic compounds, secondary treatment helps to protect aquatic ecosystems and improve water quality for potential discharge or further treatment.

While reduction of solid waste and filtration of pathogens are important aspects of wastewater treatment, they are not the primary focus during the secondary treatment phase. Similarly, desalination is a specific process aimed at removing salt from water, which is not a goal of the secondary treatment process in the context of wastewater treatment.