Ozone-driven processes for mature urban landfill leachate treatment: Organic matter degradation, biodegradability enhancement and treatment costs for different reactors configuration

In this work, the application of ozone-driven processes for the treatment of mature landfill leachate was investigated by testing different system setups. As a first approach, ozonation (O-3-only) was tested, using a porous ceramic diffuser combined with a bubble column (BC), and the best operational conditions were established for leachate treatment (initial pH = 9.0; inlet ozone dose = 18 mg O-3/min). Then, a novel photoreactor (FluHelik) was coupled in series with the bubble column, using a diffuser or a Venturi to inject ozone into the fluid stream. The FluHelik/BC-Venturi setup led to the highest efficiency, treating 50% more leachate than BC-alone using the same ozone dose and reaction time (3 h). Following, the oxidation ability of ozone combined with H2O2 and/or UVC for leachate treatment was assessed. The highest synergistic effect was obtained for the O-3/UVC process, with pseudo-first-order rate constant for DOC and COD removal, 2.0 and 1.4 times higher than for the O-3-only, respectively. Ozone-driven processes considerably enhanced the leachate biodegradability from 17% to 79% (O-3/H2O2), 81% (O-3-only), 85% (O-3/H2O2/UVC) and 91% (O-3/UVC), after a 3 h reaction period. With FluHelik/BC-Venturi system, the O-3/UVC process stands out as the most efficient and cost-effective (6.0 (sic)/m(3)), ensuring an effluent that meets discharge legal limit for COD (150 mg/L) after further biological oxidation. (C) 2020 Elsevier B.V. All rights reserved.