New insights into the pollutant composition of stormwater treating wetlands

With intensified climate change and urbanisation, constructed wetland (CW) serves as an alternative to conventional wastewater treatment plants. In Australia, the primary function of CW is to reduce sediments, nutrients from runoffs and attenuate floods. However, water quality analysis after construction is limited, hence, pollutant composition in established CWs and target pollutants in many guidelines remain outdated. To refresh the understanding of pollutants in urban discharges, this study reviewed two CWs in industrialised regions of Victoria, Australia. A total number of 26 pollutants were analysed in the collected water and sediment samples from both CW. The findings highlighted excessive concentrations of Zinc, Aluminium, Iron and Copper in one wetland and less commonly found pollutants like Barium, Titanium and Strontium are also detected. While Arsenic, Zinc, Copper, Nickel and hydrocarbons' accumulations are particularly significant in the other wetland. This study also reviews the pollutants discovered in 136 stormwater wetlands and covers the sources and impacts of various metal pollutants in stormwater runoffs. Overall, it is found that the concentrations of Zinc, Aluminium and Iron are particularly high in the CWs reviewed. This study brings attention to the pollutants profile of established CWs and the impact of heavy metals on the aquatic environment. The findings from this research revealed that the existing design and management guidelines for constructed wetlands in urban catchments are lacking in reduction targets for metal pollutants, thus improvements are essential to safeguard the water quality and performance of CWs.