Advanced hybrid electro-oxidation & O3 technology for water reuse in the fruit and vegetable process industry

Abstract

Alternative sanitising agents are required in the fruit and vegetable processing industry, capable of effectively disinfecting both the product and the washing water to increase its reuse, while not producing harmful by-products like chlorine-based agents. In the present work, electro-oxidation (EO) and ozone are proposed for vegetable process water reuse, being optimised for their individual and combined application. The application of hybrid electro-oxidation and ozone achieved 7 log reduction after 15 min of treatment in batch using boron-doped diamond (BDD) as anode material, showing important synergistic effects when compared with the individual treatments. When the process was applied in continuous mode, up to 6 log reduction of total bacteria was achieved using EO alone with Ru as the anode and stainless steel as the cathode, under 11 mA/cm2 of current density, a cell retention time of 12 s and no addition of chemical reagents (electrolyte). Under these conditions, the absence of microorganisms in water was maintained for more than 24 h, no harmful by-products (chlorate, bromate) were detected and no damage to lettuce seeds were observed when evaluating water reuse potential. HIGHLIGHTS EO and O3 for water reuse in the fruit and vegetable process sector.; Lettuce washing water was used to test the technology at laboratory scale.; The novelty lies in the application of the combined treatment for disinfection and water reuse.; 7 log reduction after 15 min in batch and up to 6 log reduction in continuous mode were achieved.; Cost reduction in terms of electrode price and durability would allow an easy up-scaling.;

Keywords

• disinfection
• electro-oxidation
• fresh-cut vegetables
• ozonation
• water reuse