Horizontal subsurface flow constructed wetlands: a natural wastewater treat-ment system

Liquid wastes such as wastewater are the main way of pollutants entrance to environment. Espe-cially in developing countries. Municipal wastewater and industrial wastewater contain easy biodegradable organic matter, organic and inorganic chemical substances, toxic and pathogens discharge into aqueous environments (lakes, rivers, oceans). There are wide ranges of treatment systems that can be used to treat wastewater. The conventional wastewater treatment systems have some weakness such as high capital cost, high energy consumption, need to expert operation and sludge disposal, while natural wastewater treatment methods because of low energy consump-tion, environmental friendly, easy operation etc., are considerable to use. Constructed wetlands is one of successful natural wastewater treatment system. Constructed wetlands is an artificial wetland created for the purpose of treating municipal or industrial wastewater, greywater or stormwater runoff. Horizontal subsurface flow constructed wet-lands are a class of wide use constructed wetlands. This class of wetlands is able to treat both municipal and industrial wastewater successfully. In this paper we tried to describe this class of wetlands, the components, treatment mech-anisms, efficiency of worldwide operating examples, advantages and limitation, as well as the carried out research with this treatment system. The review of literatures showed horizontal subsurface flow constructed wetlands can be efficient and trustworthy system to treat municipal and industrial wastewater naturally.