How does a biofilter contribute to sewage treatment?

A biofilter plays a crucial role in sewage treatment by providing a structure or medium for beneficial microorganisms to grow and thrive. This microbial community is essential for the biological treatment of wastewater, as these microorganisms break down organic matter and other pollutants present in the sewage. As wastewater flows through the biofilter, the microbes metabolize contaminants, converting them into less harmful substances, which effectively reduces the overall pollutant load in the treated water.

The function of a biofilter is integral to processes such as trickling filters or constructed wetlands, where specific conditions encourage the growth of bacteria and other microorganisms that enhance the degradation of organic materials. This biological action is what makes biofilters an effective component of sewage treatment systems, as they help ensure that the treated effluent meets the required quality standards before being discharged into the environment or reused.

Other methods outlined in the incorrect options, such as chlorination, heavy metal removal, and ionization, involve different processes and technologies that address specific contaminants but do not capture the fundamental biological treatment aspect offered by a biofilter.