Building & Facilities Management, Nov 2009
Ropemaker first in UK to recycle cooling tower water
Ropemaker is the first ever commercial building in the UK to directly recycle cooling tower water, made possible through the use of ozone treatment.
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 set out in the Building Regulations and has an 'Excellent' BREEAM rating.
As part of the sustainability measures, Ropemaker will be harvesting rainwater to reduce their mains water requirements but will also be re-using water from ozone treated cooling towers to provide enough grey water for the flushing of toilets throughout the 586,000 square feet of office space.
It is expected that, as well as providing a larger and more predictable water supply than rainwater, the cooling tower re-use will save approximately 12,000 cubic metres of water and £20,160 per year.
The technology was developed and installed by water treatment experts Waterwise who worked closely with Arup throughout the design process.
Jon Fielder of Waterwise comments:
"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, either for toilets, wash-down of yard areas or run to surface drainage. 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.
"With chemically treated cooling towers, the water contains chemicals and biocides, some of which can cause skin irritation and possible staining of sanitary ware and fittings, making it unsuitable for the use of toilet flushing.
"Whilst it is possible to re-process chemically treated wastewater using Reverse Osmosis (RO), the capital and operating costs of the plant and additional maintenance caused by chemical use remain less attractive with only 75% of the water able to be recycled.
"The use of ozone for biological control in cooling towers however, eliminates the need to use any chemical biocides. As a result the bleed-off water is ideally suited for recycling or re-use as grey water without the need for any additional pretreatment. In the Ropemaker application it is possible to recycle 100% of the cooling tower bleed-off and we expect the investment recovery period to be less than two years."