What pollutants are included in landfill leachate?

1. Organic Pollutants

In urban landfills, household waste constitutes the majority. This waste contains a high proportion of kitchen waste, which is mostly made up of organic materials that are prone to oxidative decomposition. Water quality analysis of landfill leachate reveals a wide fluctuation range in Chemical Oxygen Demand (COD). The components include low molecular weight (<500) volatile fatty acids (VFA), medium molecular weight (main components with molecular weights between 500 and 10,000) fulvic acid, and high molecular weight (main components with molecular weights between 10,000 and 100,000) humic substances. 

2. Heavy Metal Pollution

Currently, the waste classification and disposal systems in many countries are not well developed, leading to a large amount of electronic waste being disposed of in landfills along with regular household waste. During the decomposition of waste, heavy metals contained in these electronic products, especially in batteries, are gradually released and transferred into the leachate. Therefore, leachate contains a variety of heavy metal ions, such as copper, iron, zinc, chromium, cadmium, and lead, with concentrations often reaching hundreds of times those in regular domestic wastewater. 

3. Ammonia Nitrogen Pollution

Ammonia nitrogen is a key inorganic pollutant that persists in leachate. The ammonia nitrogen (NH₃-N) content in leachate can exceed 5000 mg/L. When the total nitrogen content exceeds 40%, it inhibits the growth of microorganisms, significantly increasing the difficulty of biologically degrading the leachate.