What Pollutants Does Landfill Leachate Contain?

(1) Organic pollutants

The main constituent of municipal landfills is household waste, which contains large amounts of kitchen waste. Such kitchen waste consists mainly of organic matter and is readily oxidized and decomposed. Water-quality monitoring of leachate from China's operating landfills shows that its chemical oxygen demand (COD) fluctuates significantly. This indicator is mainly composed of three classes of substances: low-molecular-weight volatile fatty acids (VFA) with molecular weight below 500, medium-molecular-weight fulvic acids with main components between 500 and 10000, and high-molecular-weight humic acids with main components between 10000 and 100000.

(2) Heavy metal pollutants

Because China's current household waste sorting and disposal system is still incomplete, large amounts of electronic waste enter landfills together with ordinary household waste. During waste decomposition, heavy metal ions contained in electronic products (especially batteries) are continuously released and migrate into the leachate. Test results show that the concentrations of heavy metal ions such as copper, iron, zinc, chromium, cadmium, and lead in the leachate can reach hundreds of times those of ordinary domestic sewage.

(3) Ammonia nitrogen pollutants

As the main persistent inorganic pollutant in leachate, ammonia nitrogen typically exceeds 5000 mg/L (as NH3-N). When total nitrogen exceeds 40%, it markedly inhibits microbial growth, making the biodegradation of leachate extremely challenging.