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 (O3-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 O3/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 O3/UVC process, with pseudo-first-order rate constant for DOC and COD removal, 2.0 and 1.4 times higher than for the O3-only, respectively. Ozone-driven processes considerably enhanced the leachate biodegradability from 17% to 79% (O3/H2O2), 81% (O3-only), 85% (O3/H2O2/UVC) and 91% (O3/UVC), after a 3 h reaction period. With FluHelik/BC-Venturi system, the O3/UVC process stands out as the most efficient and cost-effective (6.0 €/m3), ensuring an effluent that meets discharge legal limit for COD (150 mg/L) after further biological oxidation.
Keywords: Biodegradability; Gas-liquid devices; Ozonation; Ozone-based AOPs.
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