Recycled water in Council House 2

Council House 2 (CH2) is an office building for council staff that was designed with sustainability as a central theme.

Completed in 2006, the building includes a range of features and technology that conserve energy and water, while also improving the working environment for staff.

The overall water conservation design strategy for CH2, including water saving impacts of the cooling and ventilation systems, has established a total water consumption design performance target of just under 31 litres per day per person. Water management measures implemented by CH2 fall primarily into four categories:

  • water efficiency
  • water recycling by sewer mining
  • water reuse (rainwater harvesting and fire sprinkler test water)
  • innovative water saving techniques.

CH2 has the following features:

  • ‘AAAA’ fittings and fixtures throughout the building
  • taps and showerheads of low water flow rate of approximately 2.5 litres per minute and nine litres per minute respectively
  • water flow to all hand basin taps controlled by electronic sensors
  • 4L/3L dual flush toilets and two litre flush urinals.

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Water features

Water recycling and sewer mining

A Blackwater Treatment Plant was built into CH2 to treat both the blackwater (toilet) and greywater (showers and basins) waste produced by the building. The system has not been viable on such a small scale and Council is investigating the potential for the system to be modified into a precinct sewer mine to also treat sewerage ‘mined’ from the sewer in Little Collins Street, adjacent to CH2. Sewerage is usually made up of 95 per cent water and sewers can be a source of alternative water.

Reuse of fire sprinkler test water

The fire sprinkler system in the vast majority of buildings is connected to mains water and during the regular testing process the water is normally discharged to the sewer. In CH2, the fire sprinkler test water is collected and re-used, mostly in conjunction with mains water for showers and taps. It has been calculated that, over one year, this will save about 9000 litres of water per week.

Most of this water is saved from the fire pump testing. The fire pumps are connected directly to mains water, so the discharge during testing is collected and placed into the Potable Water Tank in the basement.

The water in the reticulated sprinkler pipes is considered to be potentially contaminated and this is collected and put through the Blackwater Treatment Plant.

Rainwater harvesting

The building has been designed for the total roof area to be used in capturing rainwater. The rainwater collected is used in conjunction with the recycled water from the Blackwater Treatment Plant for toilet and urinal flushing, landscape watering, cooling towers and for off-site uses such as fountain top-up and street tree irrigation. A storage tank with a capacity for one week’s capture at 15 kilolitres is located in the basement.

Shower towers and cooling towers

The shower and cooling tower systems use water as the cooling media, allowing for an energy-efficient cooling system.  Recycled water is used in the cooling towers, while the shower towers use mains water. These two features are a good example of the efficient use of a value-added product, recycled water, to improve the energy efficiency of a building while reducing greenhouse gas emissions. This is a significant factor considering drought conditions and Melbourne’s water restrictions, where the use of a limited resource may not outweigh savings in energy use and greenhouse gas emissions.


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