Which statement best matches tertiary sewage treatment?

Which statement best matches tertiary sewage treatment?

• A. Mechanical filtration
• B. Biological treatment
• C. Sedimentation
• D. Chemical treatment removes nutrients, toxins, and pathogens

Answer: (D)

Tertiary sewage treatment is the advanced stage that pushes water quality beyond what secondary treatment achieves by removing remaining nutrients, toxins, and pathogens through chemical and other enhanced processes. After the biological breakdown of waste in secondary treatment, the water still needs purification to prevent environmental problems like eutrophication and health risks. Chemical steps are commonly used here: phosphorus can be removed by chemical precipitation, and disinfection (such as chlorination or UV) eliminates pathogens. Adsorption and advanced oxidation can help remove dissolved toxins and lingering contaminants, making the effluent suitable for release or reuse. That’s why the statement about chemical treatment removing nutrients, toxins, and pathogens best captures what tertiary treatment does. Mechanical filtration, sedimentation, and biological treatment describe earlier stages and do not fully represent the extra purification achieved at this level.

Tertiary sewage treatment is the advanced stage that pushes water quality beyond what secondary treatment achieves by removing remaining nutrients, toxins, and pathogens through chemical and other enhanced processes. After the biological breakdown of waste in secondary treatment, the water still needs purification to prevent environmental problems like eutrophication and health risks. Chemical steps are commonly used here: phosphorus can be removed by chemical precipitation, and disinfection (such as chlorination or UV) eliminates pathogens. Adsorption and advanced oxidation can help remove dissolved toxins and lingering contaminants, making the effluent suitable for release or reuse. That’s why the statement about chemical treatment removing nutrients, toxins, and pathogens best captures what tertiary treatment does. Mechanical filtration, sedimentation, and biological treatment describe earlier stages and do not fully represent the extra purification achieved at this level.