Measuring the background concentration in a constructed stormwater treatment wetland

Abstract

Urban stormwater wetlands have been widely embraced by the community as a beneficial part of the stormwater infrastructure. Although a reasonably large body of research has been undertaken into the treatment efficiency of wetlands during storm events, relatively little is known about inter-event processes. Environmental effects such as wind direction and speed, wildlife and other anthropogenic activities have a significant impact on these processes. The development of a suitable model of these processes is limited by a lack of fundamental data on the movement of contaminants within a stormwater wetland during these inter-event periods. This paper describes a study that has been undertaken to determine the background concentration of suspended solids and nutrients in a constructed stormwater treatment wetland. The study has included an intensive monitoring programme of a recently constructed wetland in Brisbane, Australia. The study has identified that design issues such as the characteristics of the inlet structure play a significant role in the resuspension and movement of suspended solids through the wetland system. Wildlife and anthropogenic activities are also identified as playing an important role during inter-event periods. However, it is clear that the distribution and density of vegetation influence the removal of suspended solids and nutrients within the system during these inter-event periods. The importance of vegetation in the wetland system is also demonstrated by the relatively high C∗ values observed, which are more similar to those expected from a pond system rather than a wetland system.

Keywords:

• Background concentration
• Best management practice
• Constructed wetlands
• Nutrients
• Stormwater treatment
• Suspended solids
• Urban stormwater management
• Urbanization
• Water quality

Acknowledgements

The authors are grateful to Margaret Greenway and Ian Phillips at Griffith University, for their constructive advice and support during this project. Carolyn Polson also provided invaluable support and guidance during the sampling and analysis phase of the project. The authors are also grateful to the CRC for Catchment Hydrology for the financial support for this project.