Abstract
In this study, coagulation combined with the electro-Fe0/H2O2 reaction was developed to treat refractory organics in the landfill leachate effluent of a membrane bioreactor (MBR), and the change in biodegradability was investigated. The results showed that polymerized ferric sulfate (PFS) was the best coagulant, with removal efficiencies of chemical oxygen demand (COD) and chromaticity of 74.18% and 72.22%, respectively, when the dosage was 2 g/L and the initial pH (pH0) was 6. Under the optimal conditions of pH0 of 3, current density of 5 mA/cm2, Fe0 dosage of 3 g/L, and H2O2 dosage of 0.059 M, the electro-Fe0/H2O2 reaction showed the removal efficiencies of COD and chromaticity for coagulated effluent were 76.68% and 74%, respectively. UV-vis and 3D-EEM spectral analysis showed that humic and fulvic acids were effectively degraded, and the effluent was mostly small molecules of aromatic protein-like substances. The whole process increased the BOD5/COD from 0.049 to 0.46, indicating that the biodegradability was substantially improved. This is due to the conjunction of the Fe0/H2O2 reaction with electrochemistry, which accelerated the reduction of Fe3+ to Fe2+ on the Fe0 surface and cathode and improved the efficiency of hydroxyl radical (•OH) generation, thus promoting the removal of pollutants. The operating cost was only 4.18 $/m3, with the benefits of less Fe0 loss and no pH adjustment. In summary, coagulation combined with the electro-Fe0/H2O2 reaction is a cost-effective method for treating refractory organics in leachate and enhancing biodegradability.
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