Investigation of the Biological Treatment of Effluent From Landfill Leachate Preoxidized by the Fenton Process Combined With a Semiaerobic Aged Refuse Biofilter

Semiaerobic aged refuse biofilters (SAARBs) have demonstrated effectiveness in removing organic substances and nitrogen pollutants from landfill leachate. Nevertheless, prolonged direct recirculation via MBR-treated landfill leachate effluent (MBRE) with low biological efficacy may lead to pollutant accumulation within the SAARB, impairing its treatment efficacy. Drawing on the principle that the Fenton method can significantly reduce the refractory organic matter in MBRE and improve its biodegradability, a combined Fenton and SAARB process has been developed for treating MBRE. This study revealed that direct recirculation with MBRE into SAARB resulted in reduced pollutant removal efficiency, with the chemical oxygen demand (COD) and ammonium (NH₄ ⁺) removal rates declining to 41.60% and 29.02%, respectively. However, with the recirculation of Fenton-preoxidized MBRE (FLE), there is a notable improvement in pollutant removal efficiency, with the COD and NH₄ ⁺ removal rates increasing to 75.42% and 81.30%, respectively. This treatment also restored the nitrogen pollutant removal efficiency (the removal capacity of nitrogen pollutants under the same organic matter removal rate). Additionally, 16S rRNA analysis indicated that long-term direct recirculation with MBRE, does not favor the enrichment of dominant functional bacteria. Conversely, recirculation with FLE altered the community composition of bacteria in SAARB, leading to the enrichment of Hydrogenispora, Syntrophaceticus, and unclassified_f Peptococcaceae. This shift contributes to the enhanced treatment performance of SAARB. This study provides a novel approach for the advanced treatment of MBRE.