What natural processes do constructed wetlands utilize for wastewater treatment?

Constructed wetlands utilize the interaction of soil, plants, and microbes as their primary mechanism for wastewater treatment. In these systems, the plants provide surface area for biofilms to form, where beneficial microbes can reside. These microbes play a crucial role in breaking down organic matter, transforming nutrients, and removing pathogens from the wastewater. The soil acts as a medium that helps filter out contaminants and provides a habitat for various microorganisms essential for the biological processes involved in treatment.

This natural process is holistic, leveraging ecological functions to purify water efficiently without relying heavily on mechanical or chemical methods. While other options may touch on aspects of wastewater treatment, they do not encompass the full integration of biological, chemical, and physical interactions that occur in constructed wetlands, which is why the interaction of soil, plants, and microbes is the correct answer.