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The traditional use of water in our cities severely distorts the natural water cycle, consuming potable water for purposes such as toilet flushing and irrigation, whilst discharging excessive volumes of stormwater runoff and wastewater. Water Sensitive Urban Design (WSUD) offers a new approach to urban water management, providing water treatment and harvest for reuse using green technologies such as constructed wetlands and biofiltration systems (bioretention or raingardens). In addition to waterway protection, these multifunctional systems also enhance the local microclimate, biodiversity, aesthetics and liveability of urban landscapes.
While the benefits of the existing technologies are well documented, particularly for stormwater treatment, there are multiple other polluted water streams in the urban environment. These include greywater, treated wastewater and polluted groundwater, whose characteristics differ substantially from stormwater (e.g. in composition, volume and frequency). In addition, pollutant removal performance, particularly for nutrients, may vary depending upon design, hydrological conditions and vegetation characteristics. In particular, prolonged dry periods between stormwater inflows presents a challenge for the adoption of biofiltration systems in dry climates. Instead, other wastewater sources could be treated in hybrid (or dual-mode) biofiltration systems to provide water treatment and prevent severe desiccation of the system during dry periods.
Uncertainty also surrounds the use of constructed wetlands in sandy environments interacting with high-nutrient shallow groundwater, such as the Coastal Plain in Perth, Western Australia. Further understanding of the processes and pathways of nutrient and contaminant assimilation, and how they respond to extremes in flow variability, is required to enable managers to further optimise wetland design and operation.
This project aimed to deliver hybrid systems capable of treating multiple water sources within urban landscapes. This was achieved by further optimising stormwater biofiltration technology and wetland systems, and developing new technologies. Two outcomes were key for the project – technology delivery and the development of adoption guidelines.