Enhanced performance of a semi-aerobic aged refuse biofilter for treating landfill leachate MBR effluent pre-oxidized by a microwave-activated peroxyacetic acid process

After membrane bioreactor (MBR) effluent from landfill leachate was treated with an advanced oxidation process of microwave-activated peracetic acid (MW/PAA), refractory organic compounds were transformed into small molecular organic compounds, which could potentially serve as carbon sources for microorganisms. In this study, a combined biological method involving the use of a MW/PAA process and a semi-aerobic aged refuse biofilter (SAARB) for MBR effluent treatment of landfill leachate was established. The results showed that under optimized MW/PAA process conditions (PAA concentration = 40 mmol/L, MW output power = 160 W), the absorbance removal efficiencies at 254 nm (UV 254 ) and color number (CN) were 42.24 % and 94.09 %, respectively. After the effluent was oxidized by the MW/PAA process and then biologically treated with SAARB, the removal efficiency of total organic carbon (TOC) in comparison with that of the influent reached more than 80 % due to the large amount of bioavailable carbon generated in the MW/PAA process, which promoted denitrification in the SAARB. It improved the removal efficiency of SAARB for nitrogen pollutants (TN, NH 4 + -N, NO 3 - -N, and NO 2 - -N). The oxidized effluent of the MW/PAA process was enriched in some functional microorganisms ( Proteobacteria , Chloroflexi , Actinobacteria , and Firmicutes ) involved in organic compound degradation and nitrogen cycling in the SAARB. The effectiveness of the MW/PAA process combined with biological methods for further treatment of landfill leachate was demonstrated. This study provides practical guidance for the treatment of landfill leachate by advanced oxidation processes combined with biological methods.