Reclarified vinegar for vegetables
Geest Prepared Foods processes a wide range of fruits and vegetables, including carrots, celery, apples, onions and peppers, which are sold through a number of retail chains. Before the fruits and vegetables are sliced and cooked, it is important that they are thoroughly cleaned and disinfected to remove any remaining dirt or unwanted biological and microbial matter.
Disinfection is carried out by dipping the fruit or vegetables in a spirit vinegar bath. Previously, it had been necessary to empty the vinegar bath at regular intervals and to refill it with new clean vinegar, tankered in from a supplier. The old vinegar and the waste it contained was then passed through an on-site chemical treatment plant, with the liquid treated effluent being discharged to drain and the solid material tankered away. However, to ensure continued conformity with environmental discharge limits and to reduce overall process costs, Geest decided to investigate the possibilities of on-site recycling of the vinegar.
As a result, on-site trialling of membrane filtration technology, using portable ultrafiltration plant from Koch Membrane Systems, was carried out and these trials proved so successful that a full-scale plant, featuring two five-inch diameter special hollow fibre membrane modules manufactured from vinegar-resistant epoxy, was installed.
In operation, the used vinegar from the dipping bath is pumped from a storage tank to the ultrafiltration plant, where it is circulated through the inside of the hollow fibres by a centrifugal pump. Re-clarified, recycled vinegar passes to the outside of the fibre into a clear cartridge shell, while any vegetable matter and colour is retained by the membrane and passed to a storage tank. The recycled vinegar can be passed back to the dip tank for further use. The concentrate from the filtration process is pumped on to the existing on-site chemical treatment plant, where a much reduced volume than before is passed to drain, while the remaining solid waste is tankered away.
The plant offers product recovery of more than 99%, enabling savings in cost of bought-in vinegar, which is now used simply to top up the bath and maintain pH levels.