Wetland treatment systems are a sustainable option for water quality improvement and provide benefits for wildlife and people.
At WWT, we design our systems to mimic natural wetland habitats including pools, marshes and reedbeds which can support a rich diversity of wetland plants and macroinvertebrates.
All nine WWT centres have wetland treatment systems designed to improve the quality of water passing through them.
They perform a vital function in providing clean water for the wetlands at our reserves and centres but equally protect the sensitive wetland habitats that we release water into, including Strangford Lough and the Severn Estuary.
Wetland treatment systems confer many benefits compared to conventional mechanised treatment technologies. At our sites, these include the provision of wildlife habitat and recreational opportunities.
- Providing natural water treatment systems as a sustainable alternative to conventional mechanised treatment technologies
- Investigating even more effective management options within our wetland treatment systems, working with the Centre for Ecology and Hydrology and the University of Leeds
Our systems are diverse, from a single bed of common reed to multiple treatment stages of open water pools, marsh areas and reedbeds. The more complex systems contain a range of wetland plants including yellow flag, tussock sedge and water mint.
We regularly monitor water quality and have found that overall our systems are very good at reducing organic loading and nitrogenous compounds.
Nitrogen breakdown continues at a steady state and is not affected by system age. The efficiency of phosphate removal is good initially, but has been found to decrease over time as the systems saturate.
We are working with the Centre for Ecology and Hydrology and the University of Leeds to investigate phosphate cycling under different management options within our wetland treatment systems to increase their capacity for phosphate removal.
We’ve also found that with good design treatment systems can support a range of wetland wildlife. A comprehensive survey of macroinvertebrates was undertaken in 2008 to assess the conservation value of our systems (Buxton 2009). Results indicate that system diversity not only enhances their effectiveness at treating water and their aesthetics, but also their potential to support wildlife.
Plant and macroinvertebrate diversity were positively correlated, and notable species such as the water beetles Colambus confluens, Cercuon sternalis, and Rhantus suturalis were found.
Macroinvertebrate diversity was also found to be associated with the type of incoming water.
Those systems receiving effluent from the bird pools (animal waste) had greater species diversity and Biological Monitoring Working Party (BMWP) scores than those receiving human wastewater which had higher Biological Oxygen Demand (BOD) and nutrients.
Both the WWT Slimbridge South Finger and WWT Llanelli systems were assessed as having a high conservation value.
Buxton, A. 2009. An assessment of the conservation value of the WWT constructed wetlands for water quality improvement, using macroinvertebrates as indicators. WWT Report, 92pp.
- WWT & partners
- University of Glasgow
- University of Leeds
- John Moores University, Liverpool
- Centre for Ecology & Hydrology