Enhanced landfill leachate treatment in sequencing batch biofilm reactors (SBBRs) amended with zeolite and biochar

BACKGROUND Biological treatment of landfill leachate is inhibited by high concentrations of ammonia and recalcitrant organic matter. This study investigated the addition of natural adsorbent materials, zeolite (clinoptilolite) and biochar, to enhance biological treatment of landfill leachate in sequencing batch biofilm reactors (SBBRs). Three bench-scale SBBRs were set up with varying types of biofilm support media: (i) lightweight expanded clay aggregate (LECA) as a control (C-SBBR); (ii) LECA + zeolite (CZ-SBBR); and (iii) LECA + zeolite + biochar (CZB-SBBR). SBBRs were operated with alternating anoxic and aerobic stages to promote total nitrogen (TN) removal via nitrification/denitrification. RESULTS Excellent TAN removal (>99%) was achieved in all three SBBRs throughout the study, most likely as a result of the favorable environmental conditions and long hydraulic retention time (HRTs) applied (nine or more days). Biochar addition in CZB-SBBR resulted in significantly higher chemical oxygen demand (COD) (61-83%) and color (82-95% as UV456) removals compared with C-SBBR (42-44% for COD and 28-33% for color) and CZ-SBBR (34-45% for COD and 20-35% for color). High effluent nitrate (NO3-) concentrations initially were observed in CZB-SBBR, most likely due to limited organic carbon availability for denitrification. However, after >1 year of operation, NO3- accumulation declined and TN removal of 81% was achieved, indicating that the main nitrogen removal pathway shifted from simultaneous nitrification/denitrification to partial nitritation/anammox. CONCLUSIONS Zeolite/biochar amended SBBRs are a promising approach for enhanced landfill leachate treatment. (c) 2021 Society of Chemical Industry (SCI).