Vertical Subsurface Flow CW's: Introduction
Horizontal subsurface flow systems often show limited nitrifying capacity. Oxygen supply is based almost exclusively on the oxygen transfer by macrophytes to the rhizosphere. Vertical subsurface flow constructed wetlands are fed intermittently. Each time the top layer is flooded.Wastewater then gradually percolates down through the substrate and is collected by drainage pipes at the bottom. The system drains completely empty and this allows air to refill the bed. This method of working leads to a good oxygen transfer and therefore an excellent nitrifying capacity.