Current treatment techniques for landfill leachate: mechanisms, influencing factors, performance, and prospects

Landfill leachate that is directly discharged without treatment may jeopardize aquatic environments and human health because it has high organic matter concentrations and high toxicity. This review summarizes the latest research progress on landfill leachate treatment technologies and identifies the mechanisms underlying various treatment technologies, including chemical treatment technologies (e.g., advanced oxidation process, chemical precipitation, and coagulation/flocculation), physicochemical treatment technologies (e.g., adsorption, ion exchange, air stripping, and membrane filtration), biological treatment technologies (e.g., aerobic and anaerobic), and integrated treatment technologies. Additionally, it evaluates the performance of each treatment technology using the pollutant removal rate as an indicator, compares the advantages and disadvantages of each treatment technology, and explores the mechanisms underlying the factors that influence the efficiency of each treatment technology (e.g., pH, temperature, dissolved oxygen). Finally, future research directions on landfill leachate treatment technology are proposed, including membrane contamination problems, adsorbent or ion exchange resin adsorption capacity and regeneration, and new pollutant removal rates and toxicity changes. Additionally, economic and efficient integrated treatment technologies should be developed to promote the application and development of landfill leachate treatment technology.