Experimental Study On Advanced Landfill Leachate Treatment Using Iron-carbon Microelectrolysis-fenton Process

Leachate,a high concentration organic wastewater from sanitary landfill,is characterized by complex organic components,high colority and stench.Especially,stabilized leachate(landfill age>10 years)shows the poor biodegradability properties with a low biological oxygen demand/chemical oxygen demand(BOD5/COD)ratio,recognized as a refractory wastewater.It is particularly challenging for biological methods,thus improving the biodegradability by physical and chemical methods is necessary.In this study,the leachate was treated by iron-carbon microelectrolysis combined with Fenton process.This study explores the degradation effect of refractory organics and effects on biological availability.The content of this research mainly includes the following aspects:(1)The single factors,such as initial pH,dosage of H2O2,the mass ratio of iron to carbon,iron-carbon concentration,and reaction time were investigated sequentially for COD removal efficiency.Under the optimum reaction conditions of initial pH of 3,H2O2 dosage of 12 ml/L,iron to carbon mass ratio of 3,iron-carbon concentration of 52 g/L,reaction time of 1h,the highest removal efficiency of COD was obtained when leachate was treated by iron-carbon microelectrolysis combined with Fenton process.(2)On the basis of the single factor experiment,for significant factors(initial pH,dosage of H2O2,iron-carbon concentration),response Surface Methodology(RSM)was used to further optimize the reaction conditions.According to the 3D and contour figure,the optimal independent variables of iron-carbon microelectrolysis with Fenton process were suggested as following:initial pH of 3.12,H2O2 dosage of 12.32 ml/L,iron-carbon concentration of 55.72 g/L.In this optimal condition,the COD removal rate was 74.59%,the BOD5/COD value was 0.5.(3)To investigate the influence on the composition of organic matter in leachate during Fe-C microelectrolysis-Fenton process,DOM in the raw and treated leachate under optimal condition were determined by three-dimensional excitation and emission matrix(3D-EEM)fluorescence spectroscopy and molecular weight(MW)distribution.The result of MW distribution indicated that the organic matters with MW>10 kDa were almost completely mineralized or transformed to smaller ones.The result of EEM spectra showed that the fulvic-like substances were efficiently decomposed after treatment,suggesting the significant improvement of the biodegradability of leachate.(4)column experiments were carried out at different flow rates and the breakthrough curves at different flow rates were evaluated to determine the practical applicability of the combined process.All these results show that the Fe-C microelectrolysis-Fenton reactor is a promising and efficient technology for the treatment of mature landfill leachate.