Our Hydrologist, Rebecca Haw attended the annual Constructed Wetland Conference (CWC) in Birmingham. The conference brings together practitioners and academics from around the world to discuss constructed wetlands and their role as the world looks for more sustainable ways of managing water.
Rebecca shares her key takeaways from the conference:
A main theme of the conference was the multiple benefits of constructed wetlands. While many constructed wetlands are initiated for a single purpose, it is clear that when they are designed, implemented and managed correctly, constructed wetlands can offer multiple benefits. Constructed wetlands can provide:
• ecosystem improvements through increased biodiversity
• social benefits through providing local communities with access to blue-green spaces
• flood mitigation through attenuation of surface water runoff
• water quality benefits through treating the water within the wetlands
At the CWC, intriguing talks on the health and wellbeing benefits from wetland areas also touched on other benefits a constructed wetland can deliver. In the past, the focus of research has been on green spaces rather than blue-green spaces for health benefits. However, with water found to magnify the effects of green areas, we should really be looking at the benefits of including water within our urban designs.
Rebecca and Lee designed this poster for the CWC to illustrate the use of a 1D hydraulic drainage model in designing a wetland.
A site visit in the afternoon provided delegates with the opportunity to discuss the learnings from Hulland Ward constructed wetland/ reedbed treatment system.
Hulland Ward is an innovative constructed wetland that treats raw wastewater in a two-stage process. The constructed wetland replaced the original water treatment works constructed in the 1960s. During the first two years heavy rainfall exceeded the hydraulic capacity of the first treatment stage. Modifications were made to the second treatment stage and a forced aeration process was installed, as rest periods for the first stage were being cut too short to treat the water. This resulted in lower hydraulic conductivities as short rests meant less mineralisation of the sludge. Lessons learnt from this project were:
1. Maturing the stages of a wastewater treatment wetland/reedbed takes time, and whilst it is maturing it is not at full hydraulic conductivity – it takes longer to treat the same volumes.
2. The rest period of a wetland is key to maintain hydraulic conductivity – as a bed is fed with wastewater, the hydraulic conductivity is reduced and it takes approximately 4 to 5 days to recover.
Another hot topic in the water management sector at the moment is the ‘catchment based approach’, which was highlighted on the second day of the CWC. Through the careful location of constructed wetlands within a catchment, small scale treatment and attenuation projects can combine to have a significant impact on water quality and flood risk downstream.
Issues occurring with catchment based approaches often stem from the number of stakeholders involved. They all bring individual goals and stipulations to the situation. These objectives could be from industry wanting to comply with regulations and reduce their impact on the environment, to landowners needing to utilise their land to its maximum potential, to rivers trusts and wildlife organisations wanting to improve the overall water environment. As a natural multi-beneficial approach, constructed wetlands can meet many requirements when designed correctly. The two areas of the country that are currently implementing the catchment based approach with success are the Wyre Rivers Trust and Wessex Water.
Wetlands and blue spaces in urban areas was another interesting topic discussed at the CWC. With space at a premium within urban landscapes, innovative ways to include blue-green spaces are being developed. Strategies include using more traditional SuDS, to installing constructed wetland to replace water treatment works. A novel approach taken by one company is retrofitting floating green areas into highly urban rivers. This has a multi beneficial approach – increasing biodiversity, improving water quality and providing amenity for the local community whilst not encroaching on highly sought-after land.
Other innovative approaches to treating wastewater abroad were also discussed such as using wetlands as a low energy and low-cost solution to treating refined oil. Innovation will be key to developing a more natural approach to treating wastewater. Pressure on our natural environment is increasing so we need to act now to make sure we do not lose our blue-green spaces. A way to do this highlighted during the conference, was to sell the output from treatment systems, such as the willows or reeds used in each stage. Whilst this concept is in its infancy there is great potential to add an economic benefit to an already multi beneficial approach to treating wastewater.
Here at Envireau Water, our passion is working towards a better water environment whether rural or urban. Our surface water and wastewater teams have comprehensive knowledge and experience in locating and designing constructed wetlands, as well as other Natural Flood Management and SuDS techniques. We can help you address water quality issues in a natural way.
Get in touch with our team to see how we can support you.