What type of treatment process do trickling filters and wetlands provide?

Trickling filters and wetlands are classified as secondary treatment processes in wastewater treatment. This stage comes after primary treatment, where solids are removed from the wastewater. Secondary treatment focuses on the biological processes that further reduce organic matter and pathogens in the effluent.

Trickling filters utilize a bed of media that supports bacteria and microorganisms that digest organic pollutants as the wastewater trickles over it. This biological action is essential for breaking down remaining contaminants, making trickling filters effective at improving water quality.

Similarly, constructed wetlands rely on natural processes, including filtration, absorption, and microbial activity, to treat wastewater. The wetland plants and substrate provide an environment for microorganisms to thrive, enhancing the degradation of organic substances and nutrients.

Both systems contribute significantly to lowering the biological load before the treated water is released back to the environment, which is why they are distinctly categorized as secondary treatment processes.