The main sources of leachate generated from garbage include:

(1) The infiltration of precipitation includes both rainfall and snowfall, which are the main sources of infiltration water.

(2) The inflow of external surface water includes surface runoff and surface irrigation.

(3) When the seepage water level inside the landfill is lower than the groundwater level outside the site and there is no anti-seepage system installed, groundwater may seep into the landfill.

(4) The moisture contained in garbage itself includes the moisture carried by garbage itself and the amount adsorbed from the atmosphere and rainwater.

(5) The moisture generated during the degradation process of garbage is generated when the organic components in garbage decompose in the landfill site.

These leachate containing high concentrations of pollutants are the main source of pollution in landfill treatment. If effective measures are not taken to control them, it will pollute surface water or groundwater.