Degradation of recalcitrant organics in nanofiltration concentrate from biologically pretreated landfill leachate by ultraviolet-Fenton method

Abstract In this work, we investigated the feasibility of degrading recalcitrant organics in nanofiltration concentrate from biologically pretreated landfill leachate by ultraviolet (UV)-Fenton method at room temperature and atmospheric pressure. Both lab-scale experiments and pilot-scale studies were conducted to explore its effectiveness. Experimental results showed that the degradation efficiency of UV-Fenton method was superior to UV-H2O2 method and Fenton method. Effects of initial pH, initial temperature, Fe (II) dosage, H2O2 dosage and the dosing mode of H2O2 on the removal of organics were examined. The COD removal efficiency could reach 93% via the continuous dosing of H2O2 under the optimal conditions of initial pH 3, initial temperature 25℃, reaction time 3 h, FeSO4∙7H2O dosage 7.2 mmol/L and H2O2 dosage 400 mmol/L. The effluent COD concentration was reduced to less than 100 mg/L, which meets the Chinese national discharge standard of typical landfill leachate. Results from pilot-scale studies indicated that UV-Fenton method could provide an efficient treatment of the leachate nanofiltration concentrate with varying COD content. Biodegradability analysis, fluorescence excitation-emission-matrix combined with parallel factor analysis, and gas chromatography-mass spectrometer analysis of the treated water further verified the effectiveness of UV-Fenton method in removing recalcitrant organic pollutants and improving the biochemical properties of the leachate nanofiltration concentrate.