After waste is landfilled, under the degradation action of microorganisms, inorganic substances and low-molecular-weight organic substances produced by waste degradation, along with soluble organic matter from the waste, enter the leachate, resulting in extremely high pollutant content in the leachate. The hazards of landfill leachate are mainly manifested in the following aspects.

(1) Pollution of Surface Water and Groundwater: After leachate enters surface water bodies, the water quality severely deteriorates, causing oxygen depletion and eutrophication, which seriously damages drinking water sources and other water resources; after leachate infiltrates into the ground, contamination by pathogenic bacteria (bacteria, E. coli) and organic pollution alter the physical, chemical, and biological characteristics of groundwater, making it very difficult to restore.

(2) Pollution of Soil and Atmosphere: Leachate entering the soil will damage its inherent properties, reduce the soil's self-purification capacity, and disrupt the growth and reproduction of crops; landfill leachate has a foul odor, seriously polluting the atmospheric environment.

(3) Harm to Human Health: Harmful substances in landfill leachate can enter the human body through the food chain, causing various diseases and posing a serious threat to human health.