New water treatment process designed to manage sweet water
One of Veolia's recent projects has been to provide a water treatment process for a major international confectionary manufacturer. Sweet water, which is waste rinse water from the crystallisation and finishing stages in the manufacture of sugar coated jelly sweets, containing about 5% sugar was being discharged to drain.
New water treatment process for major sweets company
With an average flow of 1.5m3/h and high COD, the cost of discharging to sewer was significant and there was also a cost associated with the sugar, a raw material in the manufacturing process, which was being wasted. The Client was seeking a cost effective way of recovering the sugar and if possible, the rinse water for reuse.
The Veolia Water Technologies team carried out onsite trials with a pilot reverse osmosis rig; it established that the water treatment process could concentrate the sugar solution to 13% without excessive fouling occurring. The rig would also produce a clean water stream of quality better than mains water, which could be reused for non critical applications around the factory.
Veolia designed a bespoke reverse osmosis system to treat up to 1.5m3/h of sweet water at up to 50°C. The reverse osmosis membrane allows water to pass through it but rejects about 90% of dissolved salts and sugar. The resulting clean water or "permeate" stream of 1.1m3/h has a conductivity of about 50μS/cm - considerably more pure than the mains water supplied to the site, whilst the dissolved material rejected by the membrane is concentrated into a 0.4m3/h product stream containing about 13% sugar.
This is filled into 1m3 intermediate bulk containers (IBCs) for re-use within the manufacturing process. The permeate is currently discharged to drain but can be reused for boiler or cooling tower make-up or for cleaning in place as a substitute for mains water.
The initial implementation of the system, with permeate discharge to sewer, reduced the volumetric discharge by 25% but the lower COD of the discharged permeate compared to that of the sweet water delivered a major cost reduction in accordance with the Mogden formula. The recovery of sugar also gave an economic benefit by reducing the amount of raw sugar that the factory purchased. The overall effect was that the £200,000 capital cost of the plant would be repaid within two years.
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