Recent Advances in Australian Practice on the use of Constructed Wetlands for Stormwater Treatment Tony H F Wong * and Peter F Breen ** * Associate Professor, Department of Civil Engineering & CRC for Catchment Hydrology , PO Box 60, Monash University, VIC 3800, Australia; PH: +613 9905 2940; tony.wong@eng.monash.edu.au ** Director, Ecological Engineering Pty Ltd , PO Box 12, Darling South, VIC 3145, Australia; PH: +613 9571 0244; peter@ecoeng.com.au. Introduction The use of constructed wetlands for urban stormwater quality improvement is widely adopted in many Australian cities, many of which have been successfully incorporated into the urban landscape. Design considerations include the interaction between the wetland hydrology and hydrodynamic behaviour with the various physical, chemical and biological treatment processes. The operating conditions of these systems are stochastic in nature, with intermittent and highly variable hydraulic and pollutant loading. Research and on-going refinement to practice in Australia have provided a rigorous basis for sizing constructed wetlands for stormwater management and for its integration into landscape design. The performance of constructed wetland in the removal of stormwater pollutants is affected by many factors. Stormwater wetlands are subjected to extended periods of no inflow followed by events of high hydraulic loading and pollutant loads. Flow attenuation can be significant as the detention storage of the wetland fills and drains during these events. Hydrodynamic flow patterns within the wetland can vary at different stages of wetland inundation and thus, the detention period of stormwater inflow for each individual event can be highly variable. In addition to the above factors, design considerations of stormwater treatment wetland need to also include the botanical structure and layout of the wetland and the hydrologic regime necessary to sustain the botanical structure. Wetland macrophytes support a number very important pollutant removal mechanisms, including the removal of fine suspended solids and associated contaminants (eg. nutrients, metals, organic contaminants and hydrocarbons). Sustainable operation of constructed wetland systems for stormwater quality improvement requires particular attention to be placed on the overall life-cycle of the system (Wong and Geiger, 1998) and proper partitioning of the treatment sequences within the system. This paper discusses a number of pertinent design considerations and procedures aimed at achieving an optimal outcome, in terms of pollutant removal, in a highly dynamic operating environment. 1