What's the difference between surface-flow and subsurface- flow constructed wetlands, and which should I use?

Surface-flow wetlands – water flows above the surface of the sediment or media substrate, typically a clay or native soil that is impervious to water penetration and through the stems of aquatic plant vegetation.  Water is visible on the surface of the wetland treatment system.

Subsurface-flow wetlands – water flows through the media substrate, on which are planted aquatic plants.  Water is typically not visible in this type of treatment system.  This could have benefits for applications in more arid regions where evaporation is of concern.

The type of wetland most suited for installation at your operation depends upon a variety of factors: land availability, concentrations (load) of contaminants to be removed, volume of water to be treated, climate.  These site specific characteristics should be discussed with extension specialists, consultants, and/or engineers helping you design your treatment system.

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