What does a sustainable urban water strategy look like? How can we change the way we think about water use in our urban environments to use less potable water? Or maybe best in the words of Tony Wong (CRC for Water Sensitive Cities Australia):
“why aren’t we starting to think about reusing our wastewater to flush toilets? Why do we have to have drinking water to flush our toilets?”1
“We should start to think about living with two taps coming into our house, a drinking water tap and a non-drinking water tap. And the source for the non-drinking water tap could be any combination of wastewater or greywater”1
Conventionally, the urban stormwater system in Cape Town conveys rainwater from roofs and paved surfaces to gutters or drains, to underground pipes, to concrete channels, to rivers and eventually the sea. This prevents a portion of rainwater from replenishing the underground aquifer. That's why at Ruo Emoh, we chose to install gutters that directed rainwater to infiltration basins. By calculating the annual amount of rainwater that would be infiltrating on the site, we could sustainably supply the volume required for all toilet flushing and outdoor water use of the 49 houses with groundwater.
Given the groundwater quality was of a very high standard, no further treatment was required before delivering it to all toilets and outdoor taps on the site. Toilets were fitted with a potable inlet and a non-potable (groundwater) inlet to allow the opportunity to choose the flushing source for research purposes.
The next step was to make use of the greywater produced from each household. In this case, the greywater from baths/showers and basins was directed to a simple catchpit filter and infiltrated to the root zone of trees planted at the front of the properties. These trees were generously supplied by GreenPop.
Empowered Water Management
AwareThu smart water meters were installed on the potable and non-potable line to each household which measure the hourly flow of water through each line. Residents are then given access to a cellphone application which presents their hourly/daily/weekly water use in a simple clear way. The app then empowers the homeowners to set water use targets and receive alerts if they use above their daily target or have excessive water use over an hour period (burst/taps left on). Additionally, leaks can be discovered within 24hrs as a flow during the night time will be evident on the app.
This system empowers the residents to track and manage their own water use, and even compare with their neighbours in an engaging way.
Building Thriving Cities
The combination of these various aspects of the water strategy at Ruo Emoh is an example of the vision of Isidima in action:
Isidima Design and Development - "Building thriving liveable cities"
1 Tony Wong at TEDx Canberra 2013: https://youtu.be/6KFqEmcLXk8