[Composition and transformation of leachates during municipal solid waste composting]

Area of Science:

• Environmental Science
• Waste Management
• Soil Science

Background:

• Compost leachate poses challenges due to high salinity and heavy metal content.
• Understanding leachate evolution is crucial for effective waste management and resource recovery.

Purpose of the Study:

• To investigate the composition and evolution of inorganic anions, ammonia, heavy metals, and organic compounds in compost leachates.
• To identify suitable processing technologies for compost leachates.

Main Methods:

• Analysis of inorganic anions (F-, Cl-, SO4(2-), NO2(-)-N, NO3(-)-N), ammonia (NH4(+)-N), heavy metals (Pb, Cd, Cu, Zn, As, Cr, Ni, Fe, Mn), and organic compounds in leachates over different composting times.
• Characterization of organic matter, including protein-like and humic-like substances.

Main Results:

• Leachate concentrations of EC, F-, Cl-, SO4(2-), and NH4(+)-N decreased during composting.
• NO2(-)-N, NO3(-)-N, and Org-N levels correlated with the leachate's redox atmosphere.
• Heavy metals like Pb, Cd, Cu, Zn, and As decreased, while Cr, Ni, Fe, and Mn increased with composting time.
• Leachate organics were primarily protein-like and humic-like substances, with dynamic changes in their relative proportions.
• High salinity and heavy metal content limit leachate reflux utilization.

Conclusions:

• Compost leachate composition evolves significantly during decomposition.
• A combined biochemical and physico-chemical treatment process is recommended for compost leachates before emission or reuse.
• Effective treatment is necessary to mitigate environmental risks associated with compost leachate.