A constructed wetland can clean drainage water of nitrogen and phosphorus. The drainage water passes through three basins, which constitutes a form of natural treatment plant, where microorganisms reduce the nitrogen concentration in the drainage water before it passes on to the aquatic environment.
Requirement for minimum size of the constructed wetland is adjusted according to the size of the catchment area, a constructed wetland of 1 hectare will be able to clean drainage water from about 100 hectares.
Example of project with focus on constructed wetlands: iDræn
Constructed wetland with open basins, SEGES.