What is the main purpose of tertiary treatment in wastewater treatment?

The main purpose of tertiary treatment in wastewater treatment is to further polish the effluent and remove remaining contaminants. After primary and secondary treatments, which primarily focus on removing solids and organic matter, tertiary treatment is employed as an additional step to enhance water quality. This stage involves advanced processes such as filtration, nutrient removal, and disinfection methods to address any residual pollutants or pathogens that may still be present in the treated wastewater.

Through this refinement, tertiary treatment ensures that the water is of high quality, making it suitable for safe discharge into natural water bodies or for potential reuse in applications such as irrigation or industrial processes. This step is crucial for protecting public health and the environment by ensuring that water released back into the ecosystem meets stringent standards.

The other options do not accurately capture the overarching goal of tertiary treatment, focusing instead on earlier stages of treatment or adding substances that do not pertain to the polishing and finalization of treated water for safe discharge.