Research on method of adsorption and oxidation enhanced by microwave treating urban landfill leachate

Abstract

To address the high cost and low efficiency in treatment of refractory organics in landfill leachate, the treatment efficiency of landfill leachate by microwave-enhanced adsorption and Fenton oxidation was studied. Landfill leachate with high concentration COD and ammonia nitrogen (initial COD and ammonia nitrogen concentration were 33384.17mg/L and 3588.16 mg/L.), which were difficult to be biodegraded directly. Based on species and dosage of adsorbent and oxidant, pH, microwave intensity and duration, a series of experimental studies were carried on, concluding that absorption and oxidation enhanced by microwave process using zeolite (15 mesh) as adsorbent and Fenton reagent as oxidant, the dosage of zeolite was 40g/L, pH 3, the best dosage of Fenton reagent was 1g/L FeSO 4 and 0.1L/LH 2 O 2 , microwave intensity was 640W, microwave initial temperature was 80°C. In order to improve the treatment efficiency, flocculation and sand filtration treatment was settled to treat landfill leachate before this process, mainly to remove suspended solids and colloidal wastewater in substance and to clarify the water. Under optimal conditions, through absorption and oxidation enhanced by microwave treatment, the removal rate of COD and ammonia nitrogen (making the concentration after filtration as the initial concentration) were 51.60% and 76.82%. The mechanism findings indicated: Adsorption and oxidation worked meanwhile, the skeleton-like crystal structure of zeolite provides oxidation carrier for oxidants, which improved the efficiency of the oxidation. Microwave not only decomposed the refractory organic matter and strengthened the zeolite dispersion force and electrostatic adsorption of the role of ammonia, but also activated H 2 O 2 to produce hydroxyl radical to oxidize wastewater with Fenton's reagent. Through microwave-enhanced absorption and oxidation process, foul odor of landfill leachate disappeared, the color changed from thick black to colorless, concentration of organic matter and ammonia nitrogen decreased significantly.