Mangangka, Isri R. and Egodawatta, Prasanna and Rajapakse, Jay and Goonetilleke, Ashantha
(2012)
Understanding treatment characteristics of constructed stormwater wetlands.
In: The 34th Hydrology and Water Resources Symposium (HWRS 2012), Sydney-Australia.
Abstract
Constructed wetlands are a common structural treatment measure employed to remove stormwater pollutants and forms part of the Water Sensitive Urban Design (WSUD) treatment suite. In a constructed wetland, a range of processes such as settling, filtration, adsorption, and biological uptake play a role in stormwater treatment. Occurrence and effectiveness of these processes are variable and influenced by hydraulic, chemical and biological factors. The influence of hydraulic factors on treatment processes are of particular concern. This paper presents outcomes of a comprehensive study undertaken to define the treatment characteristics of a constructed wetland highlighting the influence of hydraulic factors. The study included field monitoring of a well established constructed wetland for quantity and quality characteristics, development of a conceptual hydraulic model to simulate water movement within the wetland and state-of-the-art multivariate analysis of quantity and quality data to understand correlations and define linkages between treatment performances and influential hydraulic factors. Total Suspended Solid (TSS), Total Nitrogen (TN) and Total Phosphorus (TP) concentrations formed the primary parameters used in the data analysis. The outcomes of the analysis revealed significant reduction in event mean concentrations of all the pollutants species by the constructed wetland. However, percentage reduction of pollutant loads was moderate compared to the expected performance targets. Treatment characteristics of the wetland were significantly different for storm events above and below the prescribed design event. For events below design event, TSS and TN load reduction was comparatively better and strongly influenced by increased retention time. For events above design event, TP load reduction was comparatively better and influenced by TP wash-off characteristics from catchment surfaces.
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