Constructed wetlands for wastewater treatment in Europe

The first experiments using wetland vegetation (macrophytes) for wastewater treatment were carried by out by Käthe Seidel in Germany in the early 1950s. The first full-scale free water surface constructed wetlands (FWS CWs) for wastewater treatment were put into operation in the Netherlands during 1967 and Hungary during 1968. Free water surface CWs did not spread widely in Europe and CWs with sub-surface flow have become more popular. The horizontal sub-surface flow systems were initiated by Seidel and improved by Reinhold Kickuth under the name Root Zone Method in late 1969 and early 1970s. The use of these systems spread throughout Europe in the 1980s and 1990s. These systems use porous substrates with high hydraulic conductivity for wastewater filtration. Vertical flow constructed wetlands (VF CWs) were also originally proposed by Seidel in the late 1960s as part of pre-treatment process for horizontal flow systems, which were used at full-scale in the mid-1970s and were called infiltration fields. Vertical flow systems were not used as much as horizontal flow systems because of higher maintenance and operation costs, but were used to nitrify wastewaters. Constructed wetlands have been used for many types of wastewater including industrial, agricultural, landfill leachate and stromwater runoff. As many of these wastewaters are difficult to treat in a single stage wetland system, hybrid wetland systems which consist of various types of constructed wetlands staged in series have been used in Europe.