New London building uses cooling tower bleed off as grey water
Bleed-off water from cooling towers serving the Ropemaker building in London is being used to provide grey water for flushing toilets for this 54 500 m2 building. The direct use of bleed-off water for this purpose is made possible by the use of ozone treatment for the cooling towers, rather than chemicals and biocides.
Ropemaker aims to be one of the most sustainable buildings ever developed in London. Designed by Arup Associates, it is on target to achieve 15% lower predicted carbon emissions than required by Building Regulations and has a BREEAM ‘Excellent’ rating.
Using bleed-off water from the cooling towers is expected to save about 12 000 m3 of water and over £20 000 a year. The investment recovery period is expected to be less than two years.
The water-treatment technology was developed and installed by Waterwise, which worked closely with Arup throughout the design process. There is no need for additional treatment.
John Fielder of Waterwise explains, ‘Cooling towers operate by evaporation and therefore require a bleed-off drain to control the build-up of mineral salts in the cooling-tower basin. It is this bleed off that can be recycled for re-use. Because the rate of bleed off can be calculated and determined in the design of the plant, this provides a consistent and reliable source of water for recycling in this way. In comparison, the availability of harvested rainwater is both unpredictable and intermittent.’
