What is a common stormwater treatment practice used to remove heavy metals?

Constructed wetlands are considered a common stormwater treatment practice for removing heavy metals due to their ability to mimic natural wetland processes. They provide a complex environment where various physical, chemical, and biological interactions occur. The vegetation in constructed wetlands can uptake some heavy metals, while soil microbiota can facilitate the transformation of these metals into less harmful forms. Additionally, the sedimentation process in constructed wetlands aids in trapping suspended solids that may contain heavy metals, effectively reducing their concentrations in stormwater runoff.

The alternative options also have merits in stormwater management. For instance, rain gardens and bioretention systems are excellent for managing water quantity and quality, but their effectiveness in heavy metal removal can be more site-specific and less robust compared to constructed wetlands. Sand filters can remove some contaminants and can be designed to target heavy metals, but they generally focus more on sediment and may require more maintenance to sustain their filtering capacity. Therefore, constructed wetlands are often favored in situations where heavy metal removal is a primary concern due to their comprehensive and natural treatment approach.