"This primordial drive toward greater and greater union produced Whole structures and communities in the sea which, oh so gradually, sought the light and then more light and then more yet." - Bob Macoskey, Process, 2000

Constructed wetlands treatment systems are engineered systems that have been designed and constructed to utilize the natural processes involving wetland vegetation, soils, and their associated microbial assemblages to assist in treating wastewater. They are designed to take advantage of many of the same processes that occur in natural wetlands, but do so within a more controlled environment. Some of these systems have been designed and operated with the sole purpose of treating wastewater, while others have been implemented with multiple-use objectives in mind, such as using treated wastewater effluent as a water source for the creation and restoration of wetland habitat for wildlife use and environmental enhancement.

Constructed wetlands treatment systems generally fall into one of two general categories: Subsurface Flow Systems and Free Water Surface Systems. Subsurface Flow Systems are designed to create subsurface flow through a permeable medium, keeping the water being treated below the surface, thereby helping to avoid the development of odors and other nuisance problems. Such systems have also been referred to as "root-zone systems," "rock-reed-filters," and "vegetated submerged bed systems." The media used (typically soil, sand, gravel or crushed rock) greatly affect the hydraulics of the system. Free Water Surface Systems, on the other hand, are designed to simulate natural wetlands, with the water flowing over the soil surface at shallow depths. Both types of wetlands treatment systems typically are constructed in basins or channels with a natural or constructed subsurface barrier to limit seepage.

Constructed wetlands treatment systems have diverse applications and are found across the country and around the world. While they can be designed to accomplish a variety of treatment objectives, for the most part, Subsurface Flow Systems are designed and operated in a manner that provides limited opportunity for benefits other than water quality improvement. On the other hand, Free Water Surface Systems are frequently designed to maximize wetland habitat values and reuse opportunities, while providing water quality improvement.(Source: US Environmental Protection Agency Office of Water, 2003).

For more information on Constructed Wetlands and Wildlife Habitat, visit http://www.epa.gov/owow/wetlands/construc/content.html