Reimagining Urban Wastewater Landscapes. A re-examination of wastewater treatment through the use of treatment wetlands within an urban context.

<p><strong>Over the next 50-60 years, much of the world's grey infrastructure will have reached the end of its intended design lifespan. Heavily engineered, highly centralised and typically constructed using non-sustainable materials, there is an opportunity to consider integrating green and grey infrastructures to reduce environmental impacts from grey infrastructure alone.</strong></p><p>Green infrastructure utilising wetlands has long been an approach used for the treatment and management of sewage. Of the many ecological processes that wetlands have, phytoremediation (using plants to remediate wastewater) is key. Phytoremediaton has many downstream benefits that include enhanced biodiversity both within and between our urban environments, as well as improved public spaces that provide recreational and educational opportunities. All of which contribute to a sense of community and place.</p><p>Karori in the western part of Wellington is the ideal location for this research. It is serviced by its own wastewater treatment plant that has already reached its original design capacity and is plagued by problems that result in sewage overflows into the local stream. Karori already faces an increasing demand on its wastewater system and anticipates an increase of 7,000 people by 2050.</p><p>This thesis seeks to address a range of issues from a landscape architecture perspective for reimagining the way urban wastewater is treated. A green infrastructure model that uses decentralised treatment gardens is proposed across Karori. These gardens, based on the principles of treatment wetlands, seek to offer advantages that the current centralised grey infrastructure model cannot. Namely wastewater treatment via phytoremediation processes, enhanced biodiversity leading to improved liveability at a local level facilitated by green streetscape interventions, as well as recycled water suitable for use.</p><p>Research, field work, analysis and design-led response has been used to investigate and understand how this proposal might transpire. Importantly the development and analysis of typologies has been key in drawing conclusions about the existing landscape and the potentialities it holds.</p><p>Findings derived from this research have highlighted a need to first, integrate aspects from both green and grey water infrastructure systems to maximise functionality of green infrastructure and minimise the expansion of existing grey infrastructure. Second, to rethink land use. Underutilised suburban berm spaces have been appropriated and have a key role in improving the urban water cycle by utilising specialised plant species that also enhance local biodiversity. By enriching these spaces through small scale interventions, they facilitate an improved sociability and liveability across the suburb.</p><p>Third, it was found only greywater could be accommodated through these proposed treatment gardens, given their relatively small size and limited amount of suitable street space, while the remaining blackwater would be treated through conventional means.</p>