Landfill leachate: Sources, nature, organic composition, and treatment: An environmental overview

In the landfill environment context, leachate is the liquid materials that drain from stockpiled material or land. Therefore, leachate comprises of high levels of offensive components derived from the material it has passed through. Landfill leachates are also produced as secondary products of the solid organic decomposition processes. The most hazardous products of such leachate are four major types of constituents: soluble organic matters, inorganic components, heavy metals, and xenobiotic organic compounds. Leachates of high concentrations from these components in the early acid phase are mainly due to strong decomposition. During methanogenic phase, a more stable leachate, at relatively lower concentrations, low BOD/COD ratio, and low heavy metals concentrations were recorded. On the contrary, ammonia concentration does not reduce, constituting one of the long-term pollutants within landfill leachate. These chemical constituents can cause serious environmental pollution. The behavior of landfills, its impact on the environment, and treatment methods are discussed. Nowadays, many treatment plants throughout the world are operated by expertise producing high effluent quality. Several treatment technologies are discussed presenting highly efficient system including four basic groups: (1) leachate transfer: based on recycling and combined treatment with domestic sewage, (2) Biological treatment: biodegradation: applying aerobic and anaerobic techniques and (3) chemical and physical procedures: air stripping, adsorption, chemical oxidation, chemical precipitation, coagulation / flocculation, sedimentation / flotation, and (4) membrane technologies.(c) 2023 THE AUTHORS. Published by Elsevier BV on behalf of Faculty of Engineering, Ain Shams University. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/ by-nc-nd/4.0/).