A critical Review of Landfill Leachate and its treatment by Electrochemical Oxidation: A Future energy-Oriented Approach for Sustainable Liquid Waste Treatment

Landfill leachate, a highly toxic liquid waste produced because of the degradation of municipal solid waste (MSW) and the ingestion of rainwater through waste layers, poses a significant environmental concern due to the presence of huge organic content, heavy metals, and other persistent contaminants. The nature and concentration of pollutants vary depending on landfill age, composition, and climatic factors. The larger the landfill age, the less will be the biodegradability of its organic content, and hence content shifts from easily degradable compounds to more recalcitrant substances, including humic and fulvic acids. Conventional leachate treatment method such as biological treatment and physicochemical techniques often possesses drawbacks of aged leachate, particularly in removing recalcitrant contaminants and achieving significant reductions in COD and ammonia levels. Hence, a multi-stage treatment approach is required to meet environmental standards. Electrochemical Oxidation (EO) is a viable approach of advanced oxidation process for leachate treatment since it fully degrades the organic content even if it is recalcitrant in nature, operating without any chemical transport, and with almost negligible sludge generation. EO is highly efficient in removing complex organics and ammonium nitrogen, especially in old leachate. This technology aligns with global sustainability goals and offers a pathway for developing compact, efficient treatment systems for challenging wastewater streams. The paper also discusses the integration of EO with biological systems and renewable energy sources (RES) to improve energy efficiency, reduce carbon footprint, and enable decentralized leachate treatment in smart cities and sustainable waste facilities.