Constructed wetlands for wastewater treatment: five decades of experience.

The first experiments on the use of wetland plants to treat wastewaters were carried out in the early 1950s by Dr. Käthe Seidel in Germany and the first full-scale systems were put into operation during the late 1960s. Since then, the subsurface systems have been commonly used in Europe while free water surface systems have been more popular in North America and Australia. During the 1970s and 1980s, the information on constructed wetland technology spread slowly. But since the 1990 s the technology has become international, facilitated by exchange among scientists and researchers around the world. Because of the need for more effective removal of ammonia and total nitrogen, during the 1990 s and 2000s vertical and horizontal flow constructed wetlands were combined to complement each other to achieve higher treatment efficiency. Today, constructed wetlands are recognized as a reliable wastewater treatment technology and they represent a suitable solution for the treatment of many types of wastewater.