Food processing waste dewatering by electro-osmosis

Abstract

Orsat, V., Raghavan, G.S.V. and Norris, E.R. 1996. Food processing waste dewatering by electro-osmosis. Can. Agric. Eng. 38:063-067. As a result of changing waste-handling technologies, many industrial food processing wastes now being fed to animals were once considered to be without economic value. Other factors which have increased the interest in wastes utilization as animal feed include increasing costs ofdisposal and transportation and increasing environmental restrictions. This has brought about the necessity of separating the solid waste from the liquid waste for potential reuse of both fractions. This study examines the use of pressure alone and pressure combined with an electric field for dewatering purposes. Separation trials were conducted at various combinations of pressure and electric current with three types of food wastes. The results indicated that combining an electric field with mechanical dewatering can increase the percent solids from 30 to 49% for brewer's spent grain (BSG), from 23 to 53% for apple pomace, and from II to 67% for vegetable waste. The dewatering improvement of combining an electric field to mechanical dewatering is of the order of 2 to 8% (increase in solids) depending on the applied electric field and the produce being dewatered. All separation trials yielded an energy consumption, per kilogram of water removed, considerably less when compared to thermal drying. Aujourd 'hui, avec les developpements technologiq ues dans Ie domaine du traitement et de la manutention des dechets, les residus de production de l'industrie alimentaire ont une valeur ajoutee et sont maintenant reutilises comme engrais ou aliments pour animaux. La reutilisation des dechets est amenee par I'augmentation des restrictions environnementales. Ceci amene la necessite de separer les fractions solides/liquides de la masse de dechets pour reutilisation potentielle des deux fractions. La presente etude examine une methode d 'extraction associant electro-osmose et pression mecanique. Plusieurs essais ont ete entrepris adifferents niveaux de pression et de courants electriques pour trois types de dechets. Les resultats obtenus indiquent que l'association de l'electro-osmose a une pression mecanique, peut augmenter Ie taux de solide du dcchet aplus de 50%, et ce, avec une fraction de la consommation d'energie qu'i1 en couterait si les dechets etaient traditionnelIement seches a l'air chaud. En effet, nos essais ont augmente Ie taux de solide de 30 a49% pour la dreche de brasserie, de 23 a 53% pour Ie marc de pomme de meme qu 'une augmentation de II a67% pour des dechets maraichers.