What is the main function of secondary treatment in wastewater treatment?

The main function of secondary treatment in wastewater treatment is to biologically remove dissolved organic matter. This stage typically involves processes that utilize microbial populations to break down organic pollutants present in the wastewater. During secondary treatment, microorganisms consume and metabolize organic matter, converting it into biomass and carbon dioxide, and effectively reducing the concentration of organic pollutants in the effluent.

This biological treatment is essential for achieving the necessary reductions in biochemical oxygen demand (BOD) and total suspended solids (TSS) before the treated water is discharged or further treated. Common methods used in secondary treatment include activated sludge processes, trickling filters, and pond systems, all of which are designed to optimize the growth and activity of bacteria that feed on organic materials.

While other processes, such as filtration, can remove larger debris or pathogens, and treatments specifically target heavy metal removal, these functions do not define secondary treatment's primary role. The focus is specifically on enhancing biological processes to treat dissolved organics effectively.