How do Integrated Constructed Wetlands work?
An Integrated Constructed Wetland is series of shallow ponds (generally 4-7) connected by pipework and densely planted with a mix of emergent wetland vegetation. Effluent is generally pumped from the village or faciilty to a tank or settlement pond where it flows by gravity to each pond before discharge to a stream or river. ICWs are licenced under the same EPA discharge licence system as traditional wastewater treatment systems.
Effluent is treated in a number of ways:
- Reduction of flow volume and velocity using dense planting.
- Slow rate of water movement aids the settling of pollutant particles. e.g Phosphorus
- Atmospheric processes e.g evapotranspiration and interception
- Trapping of sediment.
- Biochemical processes that take place as water enters, is stored in,or leaves a wetland.
- Plant develop a microfilm on their roots that facilitates microbial communities that in turn ‘feed’ on nutrients in the wastewater.
- Anaerobic digestion (along with other processes) are carried out in the leaf litter that settles to the base of the ponds.
- The wetland environment provides opportunities for a diversity of other (non emergent) plants and animals, the interaction of which contributes to the overall biological function of the constructed wetland.