Plan for constructed wetlands for a renewable, decentralised urban water cycle—demonstrating the integration of technical design with social justice through a democratic and accessible urban infrastructure
Context
The supply and dispersal of water in cities is an enormous problem that is being made more difficult by climate change. Firstly, maintaining a year-round supply of fresh water in places with irregular rainfall, polluted water bodies, and vast areas of cities disconnected from municipal piped networks, is incredibly complex and leaves the most vulnerable at the greatest risk of outages. Secondly, the ability of dense and hard-paved settlements to cope with both sewage and increasingly sudden rainfall is limited by insufficient wastewater networks. The result is the discharge of raw sewage into lakes, rivers, and seas, as well as the risk of flash flooding during rainfall.
One solution to this problem is the modernist infrastructural approach of building more and bigger drains—such as the “super sewer” Thames Tideway Tunnel (TTT) in London. Aside from the environmental impact of such large-scale infrastructures in itself (the TTT consumed nearly a million tonnes of concrete), they are always going to be chasing an unattainable target: one day soon, we will need more tunnels. Another approach is to rethink and decentralise how we manage water in cities.
Practice
In Rio de Janeiro, Água Carioca is a proposal for a scalable, decentralised urban water system in a city where 70% of the population are not connected to an urban sewer network. Developed by OOZE, a practice committed to the design and implementation of systems for circularity, the proposal hinges around three elements: rainwater harvesting, septic tanks, and constructed wetlands. Each one stalls water at different points in the existing linear water system to create opportunities for reuse and treatment in situ, rather than relying on expensive and energy-intensive infrastructure for moving vast volumes of water around the city.
Rainwater harvesting catches water from rooftops for use in the home, such as for bathing, cleaning, or watering plants, in order to take pressure off the potable water supply. Septic tanks keep household sewage in the locality for treatment in constructed wetlands—shallow tanks filled with substrate and planting that serve as natural filtration systems for wastewater. Design proposals at a number of scales “ranging from one school building to a whole city district” have been drawn up to show how the system might be deployed. Meanwhile, a pilot project in the estate of landscape architect Roberto Burle Marx prototypes each element of the system and serves as a demonstration piece and hub for advocacy.
“Água Carioca fundamentally turns around how we deal with water in urban areas: it is a scalable sanitation solution treating and recycling wastewater directly where it is produced. Residents engage in the process, implementing constructed wetlands into their community and creating a healthy habitat.”
The project was developed through a process of deep research and intensive participation with stakeholders. A documentary film dedicated to the process, and including an animation depicting the intervention into existing water systems, was exhibited as part of a public exhibition. These aspects of collaboration and communication are vital to both the development and implementation of the project and reflect OOZE’s wider working methods at the intersection of social and technical solutions. Operating across multiple scales, the combinations of strategic and particular, grounded and novel collaboration and expertise make Água Carioca a model for climate-oriented urban design that is both socially and ecologically sustainable.