Measuring the background concentration in a constructed stormwater treatment wetland

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