Constructed wetlands represent artificial wetlands with the main objective to harvest, treat and store storm-/grey water runoff in urban areas. Processes/services of natural wetlands are adapted to constructed wetlands focusing on water purification and (underground) storage. Hydrological processes of natural wetlands are simulated in constructed wetlands. Wetlands are complex systems: The established vegetation, the soil and microbiological activity play an important role for the filter performance of constructed wetlands. (salt) Marshes, swamps, peat bogs, coral reefs, mangroves or lagoons represent different types of wetlands. Constructed wetlands are basins (shallow) that are filled with substrate. The substrate type is variable but usually CWs are filled with sand or gravel. The substrate layer is planted with vegetation/aquatic plants. Constructed wetlands have an inlet (pipe) for storm water runoff. The water flows horizontal through the wetland while it is naturally filtered and cleaned. The main processes in a constructed wet roof are: settling of particles, filtration, chemical transformation, adsorption+ ion exchange e.g. on plants and substrates, uptake/breakdown/transformation of pollutants and nutrients by microorganisms and plants. The storm water runoff can flow over or through the substrate layer. The constructed wetland is equipped with an outlet (pipe, weir) for a controlled water discharge. The purified water flows into another pond where it is stored. The treated storm water can be used for different purposes (e.g. for irrigation within the city in green areas). According to the type of constructed wetlands wastewater flows 1) horizontal over the ground surface or 2) horizontal under the ground surface - through the substrate layer or 3) vertical through the constructed wetland - hybrid systems.

Basic information

Type: 
Retrofitting + Creation

Performance

Evapotranspiration 1 1
Shading none none
Reflection (Albedo) none
Water Conveyance 1
Water Infiltration 1
Water Retention 1
Water Storage 1
Water Reuse 2
Water Filtering 1
Water Bio-remediation 2
Deposition none
Bio-filtration none
Habitat Provision 2
Connectivity 2
Beauty / Appearance 2
Usability / Functionality 1
Social Interaction 2
Role of Nature / Mode of Action: 
Processes in/services of natural wetlands are adapted to constructed wetlands focusing on water purification and storage. The main processes in a constructed wet roof are: settling of particles, filtration, chemical transformation, adsorption+ ion exchange e.g. on plants and substrates, uptake/breakdown/transformation of pollutants and nutrients by microorganisms and plants.
Technical & Design Parameters: 
- less expensive than conventional wastewater treatment options - installation of water control measures - regular inspections, monitoring, maintenance - cost-effective
Conditions for Implementation: 
- suitable locations - outside floodplains - protection of biodiversity - upland location/gently sloped location - water flows by gravity through constructed wetland - near source of wastewater - enough land available - compact soils (minimized water infiltration to groundwater) - no endangered/threatened species - no archaeological or historic resources - accessible land
Benefits & Limitations: 
Benefits: - Water supply regulation - Water temperature control - Improve water quality/water purification - Provide water for different purposes (e.g. irrigation) - Flood control/mitigation - Habitat for wildlife/biodiversity - Recreation (watching birds) - Aesthetic value Potential limitations/disservices: - Require relatively large areas  implementation where free space is available

This project has received funding from the European Union’s Horizon 2020 research and innovation programme under Grant Agreement No. 730052 Topic: SCC-2-2016-2017: Smart Cities and Communities Nature based solutions