The ebook edition of this title is freely available as an Open Access text. Treatment Wetlands is the seventh volume in the Biological Wastewater Treatment series, which gives a state-of-the-art presentation of the science and technology of sewage treatment. The major variants of wetland systems are covered in this volume, namely: (i) horizontal flow wetlands; (ii) vertical flow wetlands; (iii) French vertical flow wetlands; (iv) intensified wetlands; (v) free water surface wetlands; (vi) other applications of treatment wetlands. The book presents in a clear and didactic way the main concepts, working principles, expected performance, design criteria, design examples, construction aspects and operational guidelines. The book has been written by an international team of top experts in the field of treatment wetlands.