BUILDING A WATER RESILIENT TOWN
Integrated water cycle saves water at Googong
C H Wong, K Hurley, C Harris
Publication Date (Web): 16 August 2017
In the 2000’s, Australia experienced the Millennium Drought which affects water supply of almost all major cities. In the midst of the drought, a new township was being planned near the inland city of Queanbeyan, some 25 minute drive south west of Canberra. Being an inland city, seawater desalination is not a water supply option for the new township of Googong. To drought proof the new town, embedded in the township’s master plan is an integrated water cycle (IWC) that comprises of a multitude of water conservation measures.
- At the infrastructure level, it includes a water recycling plant, dual reticulation system for recycled water and potable water (including dual water reservoirs), a bulk water supply connection, three sewage pumping stations, and water urban sensitive urban design for stormwater management.
- At the residential level, all dwellings need to comply with a Design Guide that mandates a minimum residential BASIX water score of 50. This promotes the uses of water efficient fixtures, rainwater harvesting, and uses of recycled water.
The IWC means that recycled water and rainwater will be used in place of precious drinking water for open space irrigation, flushing toilets, watering gardens, washing machines and firefighting. All this together targets to reduce potable water consumption in the community by up to 60%. This paper reports on the key challenges and lessons learnt for the planning and implementation of the IWC.
At the planning level, one of the major challenges is to balance the competing effluent quality requirements for phosphorous and total dissolved solids (TDS). In a semi-closed water cycle, TDS will accumulate in the water cycle unless it is adequately managed. Dynamic models for water and TDS balances were employed to elucidate impacts of treatment technology, choices of end uses on the competing effluent quality objectives. Key outcomes include selection of phosphorous removal technology that uses the least amount of chemicals, adjusting recycled water end uses and appropriate lot sizing to maximise irrigation of recycled water onto land.
At the concept design level, the membrane bioreactor (MBR) process was selected to minimise the footprint of the WRP. The entire plant is also covered and acoustically treated to minimise the odour and noise footprints. At the community engagement level, a recycled water community education strategy was jointly implemented by the developer and the local council, which include community workshops, production of key fact sheets, letterbox drops etc to educate the residents on appropriate uses of recycled water.
To date, Stage 1 of the IWC infrastructures have been delivered. These include a state-of-the-art water recycling plant, two sewage pumping stations, interim water reservoirs and dual water reticulation networks that supply more than 500 homes. To validate the design assumptions, flow monitoring is currently in place to elucidate actual consumption of potable and recycled waters, as well as wastewater generation from the township.
In summary, Googong’s IWC is an example of a progressive approach to create a water resilient inland community. When fully developed, the township of 18,000 people will only use the same amount of water that 6,500 normally would.
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