Coupling ARB-based biological and photochemical (UV/TiO₂ and UV/S₂O₈²⁻) techniques to deal with sanitary landfill leachate

The aim of this study was to provide an alternative way to remove bio-refractory organics and ammonical-nitrogen from mature municipal solid waste (MSW) landfill leachate by combining biological and photochemical processes. To achieve this objective, the effectiveness of anoxic aged refuse-based bioreactor (ARB) for biological leachate pretreatment followed by Advanced Oxidation Processes (AOPs) by heterogeneous photocatalysis (TiO₂/UV) and persulfate (S₂O₈²⁻) oxidation were tested. The results obtained after ARB based pre-treatment demonstrated a mean 72%, 81% and 92% degradation of COD, NH₄[sbnd]N and TN, respectively. However, this treated leachate cannot be discharged without another treatment; hence, it was further treated by UV-mediated TiO₂ photocatalysis and S₂O₈²⁻ oxidation. An average 82% of COD was abated at optimum condition (1 g L⁻¹ TiO₂; pH 5) whereas, using an optimum 1.5 g L⁻¹ persulfate at pH 5, 81% COD reduction occurred. Acidic and alkaline pH favored COD and NH₄[sbnd]N removal respectively. The results of this study demonstrated that coupling ARB with AOPs is potentially applicable process to deal with bio-recalcitrant compounds present in mature landfill leachate.