Landfill leachate, also known as seepage, is a secondary pollution generated during the landfilling process. Leachate forms when pollutants contained in waste are dissolved by moisture due to compaction, microbial activity, fermentation, and other factors during landfilling, mixing with precipitation, runoff, and similar sources to create wastewater. Its water quality varies significantly depending on factors such as waste composition, local climate, hydrogeological conditions, landfill age, and landfilling methods.