Artificial or constructed wetlands are an emerging technology particularly for tropical areas with water scarcity. For big cities, the challenge of a sustainable management of water resources that consider its proper use and care is always present. From this point of view, this book considers multiple case studies. As plants and microorganisms are a fundamental part of the correct functioning of these systems, their contribution to the degradation of the organic matter and to the removal and transformation of the pollutant compounds present in the wastewaters, including those of emerging concern, is also a highlight of this book.