Constructed wetlands

摘要

Constructed wetlands are natural wastewater treatment systems, in which a variety of treatment processes take place such as filtration, sedimentation and biological degradation, which together effectively remove the contaminants in wastewater. The most efficient are the subsurface flow type (SSF), where the wastewater is filtered in extensive gravel or sand basins planted with emergent macrophyte plants. In the horizontal flow type (SSF-h), the water flows horizontally through a gravel media, ensuring good organic and solids removal. In the vertical flow type (SSF-v or VF), a distribution system on the surface allows the wastewater to percolate vertically through the filter bed, enhancing oxidation processes and permitting not only effective removal of organics and solids, but also strong nitrification. Intermittent hydraulic loading of VFs further increases the aeration, because pores in the filter bed refill with air during the resting intervals between the flushes.