2.1. Free Water Surface Constructed Wetlands
A typical FWS CW with emergent macrophytes is a shallow sealed basin or sequence of basins,
containing 20–30 cm of rooting soil, with a water depth of 20–40 cm. Dense emergent vegetation
covers a significant fraction of the surface, usually more than 50% (Figure 2). Besides planted
macrophytes, naturally occurring species may be present [13]. Plants are usually not harvested and the
litter provides organic carbon necessary for denitrification which may proceed in anaerobic pockets
within the litter layer.