Treatment of semi-aerobic aged-refuse biofilter effluent from treating landfill leachate with the Fenton method

Abstract Semi-aerobic aged-refuse biofilter (SAARB) can achieve good treatment efficiency for organics and nitrogen ammonia, but the effluent of SAARB from treating landfill leachate (SAARB leachate) has high chemical oxygen demand (COD), compared to the discharge standard (100 mg/L), and high humification degree. In this study, the conventional Fenton method was used in the advanced treatment of SAARB leachate. Fluorescent components in SAARB leachate were identified and tracked with parallel factor (PARAFAC) analysis, and the influencing factors, i.e., Fe2+ dosage, n(H2O2/FeSO4) ratio, initial pH, and reaction time, on the removal of fluorescent components were systematically investigated. UV–Vis spectra show the structural transformation of dissolved organic matter (DOM) in SAARB leachate. Results show that SAARB leachate mainly contains two fluorescent components: fulvic-like substances [C1; excitation (Ex)/emission (Em) (nm), (245)280/405] and humic-like substances [C2; Ex/Em (nm), (260)360/435]. A higher Fe2+ dosage, longer reaction time, and acidic conditions increased the degradation efficiency of organics, but excess H2O2 inhibited the treatment process. Under optimum Fenton parameters (Fe2+ dosage of 5 mmol/L, n(H2O2/FeSO4) ratio of 8, initial pH of 4, and reaction time of 60 min), removal rates of C1 and C2 were 52.97% and 77.81%, respectively. UV–Vis spectra indicate that the Fenton reaction can destroy unsaturated conjugated bonds, decreasing the humification degree, hydrophobicity, molecular weight, and condensation degree. Finally, the biodegradability (represented by BOD5 (biochemical oxygen demand for 5-days)/COD) greatly increased (from 0.05 to 0.36), thus benefiting further biological treatment. The results provide suggestions and guidance for practical applications in landfill leachate treatment.