A retrofitted living stream to attenuate metal-containing stormwater run-off in Western Australia

A paradigm shift in stormwater management is taking place through the adoption of stormwater green infrastructure or nature-based solution according to Water Sensitive Urban Design (WSUD) principles. In most Australian cities, it is now common practice to retain and treat stormwater within catchments to prevent the degradation of downstream waterways using a range of WSUD elements including constructed wetland (CW). This chapter investigated heavy metal containing stormwater run-off attenuation in a surface flow CW over a decadal timeframe in Western Australia. The CW was built in 2004 and retrofitted in 2010 by incorporating macrophytes, removal of sludgy sediments, creating meandering flow path etc. The implementation and monitoring of CWs come at significant cost to both government and private developers. For example, water regulatory and utility authorities are operating hundreds of CWs (with asset values amounting to hundreds of millions of dollars), many of which are reaching their "end of asset life". These agencies have allocated substantial budget to renewing these assets; however, we do not know whether a CW is achieving its pollutant reduction targets. Therefore, this chapter also investigated the role of the retrofication initiatives on overall treatment performance. The studied CW attenuated higher metal concentrations immediate after the retrofication regimes compared to that of the pre-restoration regimes. Metal attenuation increased during the higher hydraulic retention time of the system, while sediments were found as the metal sink, particularly after the restoration regimes.