Which contaminant is most effectively reduced through secondary treatment?

The most effective reduction of contaminants during secondary treatment is indeed dissolved organic matter. Secondary treatment typically involves biological processes where microorganisms, such as bacteria, break down organic pollutants. This process is designed to convert dissolved organic matter into a simpler form that can be more easily removed from the wastewater.

In secondary treatment, bacteria consume the dissolved organic substances, resulting in a significant reduction in these compounds within the effluent. This is essential for meeting regulatory standards for water quality before the effluent is discharged into the environment or further treated for reuse.

While secondary treatment can also have impacts on nutrient removal and pathogen reduction, its primary focus is on the degradation of organic content from the wastewater. Heavy metals, which are inorganic contaminants, typically require different treatment methods, such as chemical precipitation or advanced filtration, rather than biological processes. Thus, secondary treatment is most closely associated with the reduction of dissolved organic matter.