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Direct water reuse at United Milk plc, Wiltshire, England
United Milk plc, formed in 1999 has set up an innovative plant at Westbury, Wiltshire to receive milk by road tanker and process it into milk-products such as cream and butter. At full capacity it can process 2500 tonnes of milk/day.
During an assessment of its water mass balance, United Milk identified evaporative condensate as a major wastewater source. The company investigated recovering the evaporative condensate for reuse elsewhere within the plant. It was deemed suitable for reuse because it was clean (low in suspended solids) and abundant in supply. The added advantage is that the wastewater has a high temperature and the reuse applications requires hot water, thus there are energy and cost savings from not having to heat cold (potable) water.
The evaporative condensate is recovered and passed through a Reverse Osmosis semi-permeable membrane to separate the permeate (condensate passing through the membrane) from the retentate (contaminants left behind). The captured permeate has a temperature of 650C and is treated using chlorine dioxide prior to reuse. Once treated, the permeate has reuse applications such as as boiler feed or in hot cleaning-in-place operations. Reusing this wastewater has met the total water requirement of the plant (1530 m3/day) and been instrumental in producing water-related cost savings of £2000/day.
This case study is based on material provided by Envirowise, the government-funded environmental information service for UK Businesses. ( www.envirowise.gov.uk CS404 ‘Dairy profits from zero water use’)
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