ABSTRACT
Constructed wetlands (CWs) have a low energy requirement, are environmentally friendly and are natural treatment systems. The potential of CWs for the removal of biological oxygen demand 5, chemical oxygen demand, suspended solids and nutrients from domestic wastewater is well documented. CWs have demonstrated the effectiveness of heavy metal removal from petroleum refinery wastewater. In CWs, a great diversity of microbial communities grows on wetland plant roots which enhance the pollutant removal efficiencies. A hybrid CW is a combination of two or more CWs in series that combines the advantages of the various CW systems to provide a better effluent quality than a single CW system. The laboratory and environmental field duplex-CWs were highly effective for the treatment of hydrocarbons, nutrients and other water quality parameters. Both vertical subsurface flow and horizontal subsurface flow constructed wetlands were effective in the treatment of secondary treated refinery wastewater. The chapter also presents an overview of the key concepts discussed in this book.
