Feasibility Study on Enhancing the Biodegradability of Fresh and Old Landfill Leachate Using Combined Chemical Precipitation and Fenton Processes Publisher Pubmed



Rasolevandi T ; Naddafi K ; Hassanvand MS ; Hadi M ; Alimohammadi M ; Yaghmaeian K
Source: Scientific Reports Published:2026

Abstract

Landfill leachate (LL), due to its high concentrations of heavy metals, ammonia nitrogen (NH₃-N), and persistent organic compounds, requires effective pretreatment before biological treatment. This study evaluated a three-stage approach—chemical precipitation with lime, ammonia stripping, and Fenton oxidation—for fresh and old leachate from the Aradkooh Waste Processing Complex in Tehran. Lime dosages of 9 g/L for fresh and 18 g/L for old leachate were determined from preliminary experiments.; these values were selected due to their favorable performance in reducing heavy metals and NH₃-N. Arsenic showed the highest removal efficiency (93% in fresh leachate, 66% in old), while NH₃-N removal reached 93% in both. The Fenton process was optimized using a Box–Behnken design (BBD) and response surface methodology (RSM), with three variables—H₂O₂: Fe2+ ratio, H₂O₂ dosage, and reaction time—and the BOD5/COD ratio as the response. Optimal conditions (A = 2, B = 10, C = 60 min for fresh; A = 2, B = 8.2, C = 75 min for old) increased the BOD5/COD ratio from 0.29 to 0.67 in fresh leachate and from 0.23 to 0.73 in old leachate. Chemical oxygen demand (COD) removal efficiencies in fresh and old leachate were 88.3% and 81.3%, respectively. These findings demonstrate that combining chemical precipitation and Fenton oxidation effectively enhances leachate quality and biodegradability, supporting improved biological treatment performance. © The Author(s) 2026.