Constructed wetlands are among the recently proven efficient technologies for wastewater treatment. Compared with conventional treatment systems, constructed wetlands are low in cost, easily operated and maintained, and have a strong potential for application in developing countries, particularly by small rural communities. Nevertheless, the use of constructed wetlands for the improvement of drinking water quality (such as the purification of river water for drinking purposes) is still uncommon. Treatment technologies that use natural processes and/or passive components continue to be of interest to many segments of society for a wide variety of applications. This article summarizes information on the current methods used for water treatment using constructed wetland systems and presents several case studies.