Sainsbury’s slashes waste water from cooling towers
The treatment and re-use of waste water from cooling towers at Sainsbury’s new distribution centre in Dartford is expected to reduce bleed-off water by 75%. Oasis recycling units from Waterwise Technology are being used to recycle cooling water.
A typical cooling tower rejecting 5 MW of heat operating at full load discharges about 3.6 m3/h as waste water. At an average load of 30%, the bleed off will be 1.08 m3/h. Based on Thames Water’s charges for metered premises of 168.9 p/m3, the cost is £15 976 a year.
Reducing bleed-off by 75% achieves a saving of £11 980 a year in water and effluent costs.
The annual operating cost of an Oasis unit is less than £2000, and they achieve a payback in less than two years.
The system uses a combination of filtration, ion exchange and reverse osmosis to purify bleed-off water from cooling towers and enable it to be used as fresh make-up water. The effectiveness of the process is such that the quality of the recycled water is as good as or, in most cases, better than water from the mains supply.