Development of a treatment train for the remediation of a hazardous industrial waste landfill leachate: A big challenge.

This study focuses on the development of a treatment train for a leachate from a hazardous industrial waste landfill (HIWL) previously treated by: (i) catalytic oxidation with hydrogen peroxide (HO) for sulphide and sulphite conversion into oxidized sulphur species, including sulphate, and (ii) chemical precipitation of sulphate as barite. The complete treatment line counted on four more stages: (iii) 1 biological oxidation for removal of biodegradable organic compounds and nitrogen species, (iv) coagulation with ferric chloride (coagulant dose of 100 mg Fe L, pH 2.8) for removal of a fraction of recalcitrant organics and suspended solids, (v) photo-Fenton oxidation using ultraviolet A (UVA) radiation (PF-UVA) (pH 2.8, initial total dissolved iron content of 140 mg L, treatment time of ~4 h) for recalcitrant organics degradation and biodegradability improvement, and (vi) 2 biological oxidation for removal of the biodegradable organic matter resulting from the PF-UVA process. The use of anodic oxidation or photoelectro-Fenton processes in stage (v) demonstrated to be unfeasible. A chemical oxygen demand (COD) below 1000 mg O L, a common limit imposed by municipal wastewater treatment plants (MWWTPs) to effluents discharged into the municipal sewer, was achieved after a feasible treatment time (~4 h) using the multistep approach. The remediation of the HIWL leachate proved to be a big challenge.