Formation and treatment of leachate from garbage

Formation of leachate from garbage

Leachate from garbage is the wastewater that seeps out during the process of stacking and landfilling due to fermentation, rainwater erosion, and immersion in surface and groundwater. Its main sources include the following aspects:

Garbage itself contains moisture: Garbage carries a certain amount of moisture during collection, transportation, and stacking.

Water generated by biochemical reactions of garbage: Water is produced during biochemical reactions such as oxidation and decomposition of garbage in landfills.

Underground groundwater infiltration: Groundwater may seep into the garbage heap through the bottom or sidewalls of the landfill site.

Atmospheric precipitation: Rainwater and other atmospheric precipitation are one of the main sources of leachate, with concentration, short duration, and recurrence, accounting for the majority of the total leachate.

Leachate is a high concentration organic wastewater with complex composition, and its properties are influenced by various factors, including garbage composition, garbage particle size, compaction degree, on-site climate, hydrological conditions, and landfill time. The water quality characteristics of leachate mainly include:

The water quality is complex and harmful: the leachate contains various organic pollutants and heavy metal ions, some of which have been confirmed to be carcinogens or mutagens.

High CODcr and BOD5 concentrations: These indicators reflect the content of organic matter in wastewater, and the CODcr and BOD5 concentrations in leachate are much higher than those in general urban sewage.

High ammonia nitrogen content: The nitrogen in the leachate mostly exists in the form of ammonia nitrogen and increases with the extension of landfill time.

Significant changes in water quality: There are significant differences in the water quality of leachate from different landfill ages. Young leachate has strong biodegradability, while older leachate has higher ammonia nitrogen concentration.

High metal content: The leachate contains more than ten types of metal ions, such as iron, zinc, lead, etc., with some metal ions having high concentrations.

Treatment of leachate from garbage

For the treatment of leachate from garbage, multiple processes and steps are usually used for comprehensive treatment to achieve the goals of reduction and resource recovery. Here are some common governance methods:

Solid liquid separation: Physical methods are used to separate solids and liquids in leachate. Common solid-liquid separation methods include precipitation, filtration, pressure filtration, or centrifugation.

Biological treatment: Send the clarified liquid to the biological treatment unit for biodegradation and treatment. Biological treatment units can use aerobic or anaerobic methods to degrade organic matter in leachate through the action of microorganisms. Common biological treatment units include activated sludge process, biofilm process, biofilter, etc.

Advanced oxidation: For difficult to degrade organic substances, advanced oxidation technology can be used for further treatment. Advanced oxidation methods include UV/ozone oxidation, hydrogen peroxide oxidation, advanced oxidation reactors, etc., which can further degrade and oxidize organic substances, improving treatment efficiency.

Membrane separation: using membrane technology for solid-liquid separation and purification. Common membrane technologies include microfiltration, ultrafiltration, and reverse osmosis. Membrane filtration can remove small particles, suspended solids, bacteria, viruses, and dissolved organic matter, improving the quality of effluent.

Residue treatment: For the solid sludge and residue generated during the treatment process, further treatment is required. Common treatment methods include sludge concentration, stabilization, incineration, or landfill. These methods can reduce sludge volume, stabilize organic matter, or treat residues harmlessly.

Resource recovery: Fully quantified treatment of leachate can also include the recovery and utilization of valuable components in the treated liquid. For example, nitrogen and phosphorus can be extracted from the effluent through a nitrogen and phosphorus recovery system for the production of fertilizers or other purposes.

In summary, the formation of leachate from garbage is influenced by various factors and the water quality is complex and variable. The treatment process requires the comprehensive use of multiple processes and technological means to achieve the goals of reduction and resource recovery. In practical operation, it is necessary to choose appropriate processes and equipment for processing according to specific situations and requirements, and pay attention to good practices in operation and maintenance to ensure the stable operation and efficient performance of the processing system.