Leachate Treatment in Municipal Solid Waste Landfills in Hubei,China

Project Case Study: Leachate Treatment in Municipal Solid Waste Landfills in China

Project Name: Case Study of Leachate Treatment in Chinese Domestic Waste Landfills

Pollution Type: Urban Domestic Sewage Treatment

Processing Scale: Daily capacity of 200 tons

Processing Technology: Biochemical + Physicochemical

Product used: reverse osmosis membrane scale inhibitor, cationic polyacrylamide,polyacrylamide

Characteristics and Challenges of Leachate Treatment:

1. Complex and Highly Hazardous Water Quality: Analysis reveals the presence of 63 harmful organic compounds, one carcinogen, and five mutagenic and carcinogenic substances. Six of these compounds are listed as priority pollutants for treatment in China.

2. High Concentrations of COD, BOD, and SS: Concentrations of Chemical Oxygen Demand (COD), Biological Oxygen Demand (BOD), and Suspended Solids (SS) can reach as high as 16,000 mg/l, 4,000 mg/l, and 800 mg/l, respectively. Ammonia nitrogen levels can increase with the duration of landfill operations, reaching up to 1,700 mg/l.

3. Significant Water Quality Variations: Based on the landfill's age, younger leachate (less than 5 years old) is characterized by high CODcr and BOD5 concentrations and strong biodegradability. Conversely, older leachate (over 5 years old) has a pH value close to neutral, with reduced CODcr and BOD5 concentrations, poorer biodegradability, and elevated ammonia nitrogen concentrations.

4. High Heavy Metal Content: Leachate from landfills contains more than 10 types of metal ions, including iron concentrations up to 2,000 mg/l, zinc up to 1,300 mg/l, lead up to 12.5 mg/l, and calcium even reaching 4,300 mg/l.

5. Imbalanced Microbial Nutrients: The leachate exhibits an imbalance in the proportions of Carbon (C), Nitrogen (N), and Phosphorus (P). Specifically, the BOD5/P ratio in typical landfill leachate exceeds 300. In summary, leachate treatment poses complex processes, high treatment difficulties, and substantial investment and operational costs.

Technical Features of the Solution:

1. Leachate Collection and Regulation: Leachate enters a regulation tank via a collection pipeline network, homogenizing water quality and quantity to mitigate system impacts.

2. Flocculation and Sedimentation: This system removes suspended solids from wastewater, reducing the load on subsequent treatment stages.

3. Ammonia Stripping: The effluent undergoes ammonia stripping, with the recovered ammonia utilized as fertilizer.

4. Biochemical Treatment: Wastewater is treated in an "anaerobic reactor + hydrolysis acidification + aerobic" system, effectively removing organic matter and facilitating nitrogen and phosphorus removal.

5. Membrane Filtration and Sludge Management: Effluent from the aerobic tank enters a UF/NF/RO (Ultrafiltration/Nanofiltration/Reverse Osmosis) system. UF sludge concentrate is recycled to the hydrolysis acidification tank. After UF/NF/RO filtration, water enters the clean water tank for discharge in compliance with standards. Sludge from the process is concentrated, dewatered in a filter press, and the sludge cake is transported externally. The filtrate is recycled to the regulation tank.

Treatment Outcomes:

The urban domestic sewage treatment system demonstrates excellent effluent quality, meeting discharge requirements. It effectively adapts to unstable effluent quality and non-compliant color standards. Based on actual requirements and the designed process, the "biochemical + physicochemical" combined treatment process enhances effluent quality, ensures compliance with discharge standards, and guarantees long-term stable operation of the sewage treatment system.