Generation mechanisms, environmental behaviors, and treatment technologies of conventional and emerging contaminants in landfill leachate: A review

Landfill leachate, derived from municipal solid waste landfills, is generated by external factors (e.g., rainfall erosion, solar radiation) and internal processes (e.g., physical sedimentation, chemical reactions, biodegradation). With high concentrations of heavy metals, organic pollutants, pathogens, microplastics (MPs), and antibiotics, this highly toxic effluent seriously threatens surrounding environments (soil, groundwater, etc.) and human health if improperly discharged/leaked. Thus, this paper systematically reviews the generation mechanisms, environmental behaviors, and treatment technologies of conventional pollutants (e.g., COD, BOD5, ammonia nitrogen) and emerging contaminants (e.g., MPs, PFASs, PPCPs) in leachate. To date, various technologies (e.g., adsorption, AOPs, microbial treatment, phytoremediation) have been developed to reduce leachate ecotoxicity and meet discharge standards: membrane separation and AOPs perform well among physicochemical methods, while anaerobic-aerobic coupled systems and constructed wetlands excel in biological approaches. However, leachate composition is highly heterogeneous (pollutant types/concentrations affected by landfill age, climate, etc.), greatly challenging treatment efficiency—this reduces conventional process effectiveness and raises operational time/costs. Thus, future research should focus on developing efficient, low-consumption collaborative systems, optimizing process combinations, and enhancing leachate full-life-cycle management to support sustainable landfill environmental governance. • Landfill leachate exhibits high heterogeneity, emerging contaminants (MPs, PFAS, PPCPs) pose significant challenges. • Integrated physicochemical-biological systems demonstrate superior efficiency, combining membrane separation, advanced oxidation, and microbial-plant synergies. • Membrane technologies and advanced oxidation processes are preferred for high-concentration organic and refractory pollutant removal, though fouling and energy costs remain limitations.