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

摘要

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 (3h). Following, the oxidation ability of ozone combined with H_2O_2 and/or (JVC 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/H_2O_2), 81% (O_3-only), 85% (O_3/H_2O_2/UVC) and 91% (O_2/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 €/m~3), ensuring an effluent that meets discharge legal limit for COD (150 mg/L) after further biological oxidation.