Leachate injection using vertical wells in bioreactor landfills

Area of Science:

• Environmental Engineering
• Geotechnical Engineering
• Water Resources Management

Background:

• Leachate recirculation in landfills offers significant economic and environmental advantages.
• Effective design of recirculation systems is crucial for optimal performance and environmental protection.

Purpose of the Study:

• To numerically evaluate key design variables for vertical well leachate recirculation systems.
• To assess the impact of various parameters on liquid pressure head and wetted width.

Main Methods:

• Utilized the finite-element model HYDRUS-2D for numerical simulations.
• Evaluated parameters including hydraulic conductivities, injection rates, well dimensions, and leachate collection system properties.
• Simulated steady-state flow conditions to analyze pressure head on the liner and wetted width of the waste.

Main Results:

• Well diameter, backfill conductivity, screen height, and depth showed minimal impact on wetted width.
• Increased waste hydraulic conductivity decreased wetted width and injection pressure.
• Liner pressure head increased with reduced vertical distance between the well screen and leachate collection system.
• Higher injection flux correlated with lower leachate collection system conductivity.
• Pea gravel backfill resulted in significantly lower liner pressure heads compared to sand.

Conclusions:

• Waste hydraulic conductivity and leachate collection system design are critical factors in leachate recirculation.
• Optimizing these parameters can effectively manage pressure on landfill liners and enhance recirculation efficiency.
• The choice of backfill material, like pea gravel, can substantially reduce liner pressure.