Targeted removal of organic foulants in landfill leachate in forward osmosis system integrated with biochar/activated carbon treatment

Abstract

Forward osmosis (FO) has been adopted to treat complex wastewater such as landfill leachate due to its high rejection of organics. In this study, the in-line adsorptive process using biochar (BC) or powdered activated carbon (PAC) was applied to a cross flow FO system to enhance the mitigation of the FO membrane fouling from landfill leachate. The changes in the leachate composition along the treatments were tracked by excitation emission matrix-parallel factor analysis (EEM-PARAFAC) to identify tryptophan-like (C1), fulvic-like (C2), and humic-like (C3) components. After a single operation of FO, the Cl was found to be the main constituent responsible for membrane fouling irrespective of varying operation conditions regarding draw solute concentrations and flow rates. Both sorbents (i.e., BC and PAC) exhibited the preferential removal behavior towards C1 > C2 > C3, which was welt supported by their individual adsorption isotherm model parameters. The addition of in-line adsorption treatment to FO resulted in substantial improvements in the filtered volume (>57%) and the flux recovery (>80%) compared to the single FO operation. Without chemical cleaning of membrane, the flux was fully recovered at a dose of 10 g/L BC or 0.3 g/L of PAC. A significant and negative correlation was found between the flux recovery and the C1 of the feed leachate or the corresponding spectral peak intensity (p < 0.05) for the integrated FO system, suggesting the potential of using on-line fluorescence monitoring for the performance of the integrated system in terms of fouling mitigation. This study provided a new insight into the effectiveness of BC or PAC adsorption as the in-line integration with an FO system for the targeted removal of FO membrane foulants in landfill leachate. (C) 2019 Elsevier Ltd. All rights reserved.