1. Introduction
Constructed wetlands (CWs) are engineered systems that have been designed and constructed to
utilize the natural processes involving wetland vegetation, soils, and the associated microbial
assemblages to assist in treating wastewaters. 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. CWs
for wastewater treatment may be classified according to the life form of the dominating macrophyte,
into systems with free-floating, floating leaved, rooted emergent and submerged macrophytes [1].
Further division could be made according to the wetland hydrology (free water surface and subsurface
systems) and subsurface flow CWs could be classified according to the flow direction (horizontal and
vertical) [2]. A simple scheme for various types of constructed wetlands is shown in Figure 1.