A review on conventional and plasma-based technologies for landfill leachate treatment: Mechanisms, challenges, and perspectives

Landfill leachate (LFL) treatment has been a global problem for a long time. Conventional treatment methods like chemical and electrochemical coagulation, adsorption, membrane separation, biological treatment, and advanced oxidation processes are hindered by limitations such as high energy demands, sludge generation, fouling, and incomplete removal of refractory organics or ammonia. Therefore, integrating plasma-based methods capable of generating reactive species to degrade persistent pollutants with conventional processes offers a pathway toward more efficient and scalable LFL remediation. In this review, the advantages and disadvantages of different technologies for LFL treatment have been discussed. Furthermore, the technological development over time in LFL treatment research, with a focus on the plasma technique, was reviewed. The mechanisms and principles of plasma technology, along with variables influencing LFL treatment, including pH, voltage, carrier gas, electrode materials, ionic strength, and catalysis, were reviewed. Various plasma reactors and their performance in several works were compared. The effectiveness of plasma in removing viruses, micropollutants, pesticides, and pharmaceuticals was evaluated. Challenges related to energy consumption and scalability of plasma systems were analyzed, providing a roadmap to guide future research and inform readers. Overall, plasma-based technologies offer a multifunctional and rapid approach to LFL treatment, particularly for sustainable organic, ammonia, and emerging pollutants without requiring additional chemicals. They demonstrate high COD and ammonia removal efficiencies (often exceeding 80 %) under ambient conditions, achieving detoxification and color reduction with minimal sludge and reduced secondary pollution. Their scalability, energy efficiency, and compatibility with hybrid configurations make plasma methods a promising solution for sustainable LFL management.