Sewage sludge to landfill: some pertinent engineering properties

Area of Science:

• Environmental Engineering
• Geotechnical Engineering
• Waste Management

Background:

• Increasing volumes of sewage sludge require efficient disposal methods due to stringent wastewater discharge regulations.
• Current sludge-to-landfill practices face challenges from stricter legislation, higher landfill taxes, and operator reluctance towards slurry-state sludge.
• Need for improved strategies to address engineering and drying properties of municipal sewage sludge for landfilling.

Purpose of the Study:

• To present the engineering and drying properties of municipal sewage sludge.
• To apply these properties to the design, construction, and performance of sewage sludge monofills.
• To determine optimal conditions for sludge handling and landfill construction to maximize landfill capacity and operational life.

Main Methods:

• Characterization of engineering and drying properties of municipal sewage sludge.
• Application of properties to the design and construction of sewage sludge monofills.
• Analysis of sludge handling within specific water content ranges (85%-95%) for optimal compaction and density.

Main Results:

• Optimal water content for sludge handling and landfill construction is between 85% and 95%.
• Standard Proctor compaction within this range achieves maximum dry density of approximately 0.56 tonne/m3.
• Undrained shear strength and effective stress-strength parameters were determined for landfill stability analysis.

Conclusions:

• Sludge handling and landfill construction are most effective within a specific water content range, maximizing storage capacity and landfill life.
• Achieving maximum dry density through compaction enhances landfill operational efficiency.
• Landfill subsidence due to decomposition is significant but slows over time, requiring long-term consideration.