Recent technologies for leachate treatment: a review

Municipal solid waste leachate, a kind of wastewater, can severely damage the environment and contaminate the groundwater because of its high organic matter and toxic heavy metal concentrations. Due to its complex composition, this wastewater must be properly treated prior to being discharged into the environment. In recent decades, several biological approaches (e.g., bioremediation, phytoremediation, and bioreactors) and physicochemical processes (e.g., coagulation/flocculation, air stripping, and advanced oxidation processes) have proven effective at removing the organic load and the toxicity of this effluent. Physicochemical treatments have been applied as pretreatment or post-treatment steps for biological processes, but these methods do not always provide satisfactory results and can cause secondary pollution in some cases. In addition, owing to the high concentrations of organic matter, ammonia, and trace metals in landfill leachate, combined approaches to leachate treatment have been reported to be efficient. This article highlights the advantages and drawbacks of these approaches to the treatment of leachate by providing an updated overview of the various methods that have been successfully applied in this field. Further studies should focus on improving landfill leachate treatment to maximize removal performance. Graphical abstract