What role do biofilters play in tertiary treatment?

• A. They provide primary treatment of wastewater.
• B. They disinfect effluent before discharge.
• C. They use biological processes to remove remaining pollutants.
• D. They aerate water to enhance oxygen levels.

Answer: (C)

Biofilters are essential components in tertiary treatment processes, specifically designed to further purify effluent by utilizing biological mechanisms. During tertiary treatment, the goal is to remove any remaining contaminants that are not eliminated during primary and secondary treatment stages. Biofilters achieve this by promoting the growth of microorganisms on a media layer, where these bacteria and microorganisms break down and assimilate residual organic matter and nutrients, such as nitrogen and phosphorus.

By effectively using biological processes, biofilters enhance the quality of the effluent before it is released into the environment or reused. This is crucial for meeting stringent discharge standards and protecting aquatic ecosystems.

In contrast, primary treatment involves the removal of large solids and is not the focus of biofilters, while disinfection processes typically involve methods such as chlorination or UV treatment to eliminate pathogens rather than biological removal of contaminants. Similarly, while aeration can enhance oxygen levels, it is a distinct process used in earlier treatment stages to facilitate microbial activity rather than the specific function of biofilters in tertiary treatment.