ABSTRACT

Wetlands are complex, natural, shallow, lentic water regimes dominated by hydrophytes (aquatic plants) providing enormous opportunity for environmental restoration especially the waters. Natural wetlands have been used to provide tertiary treatment to municipal wastewater as a cost-eective alternative to conventional methods [85]. Constructed wetlands (CW) or engineered wetlands are designed to utilize the benets of natural wetlands and processes for various purposes ex-situ. CWs were initially developed 50 years ago in Europe and North America for the treatment of wastewater and have been developing fast over the last few decades and it represents a widely accepted

water treatment alternative [62]. Constructed wetlands used for treatment include articial marshes, ponds, and trenches [96]. Macrophytes (large aquatic plants) are assumed the main biological component of wetlands depending on their biological characteristics such as interspecic competition and ability to tolerate the changing characteristics of the residual water [30]. Aquatic macrophytes, especially the submerged roots, provide substratum to the bacterial community to grow on the submerged roots and stems. In fact, these bacterial communities are instrumental in the removal of colloidal biochemical oxygen demand (BOD) from wastewaters [96]. Constructed wetlands typically are of two types: (1) surface ow (free water surface) and (2) subsurface ow having emergent aquatic plants as the

56.5 Hybrid Constructed Wetlands ..............................................................................................752 56.6 Summary and Conclusions ....................................................................................................752 References .............................................................................................................................................753