Multiple-scale dynamic leaching of a municipal solid waste incineration ash

Area of Science:

• Environmental Science
• Geochemistry
• Waste Management

Background:

• Predicting pollutant impacts on subsurface and groundwater requires understanding the "source term" of waste materials.
• Municipal solid waste (MSW) incineration ash is a potential pollutant source requiring accurate source term characterization.
• Standard laboratory upward-flow percolation tests are used to define source terms for granular waste.

Purpose of the Study:

• To evaluate the LIMULE project's (Multiple-Scale Leaching) findings on extrapolating laboratory percolation test results to other scales and conditions.
• To determine the applicability of the liquid versus solid ratio (L/S) for predicting pollutant behavior at different scales.
• To assess the suitability of coupled chemistry-transport modeling for reactive elements.

Main Methods:

• Conducted upward-flow percolation tests at three distinct scales: laboratory column (30 cm), lysimeter cells (1-2 m), and a large instrumented column (5 m).
• Collected concentration data for dissolved elements from percolating water across all experimental scales.
• Analyzed data by plotting concentrations against the liquid versus solid ratio (L/S).

Main Results:

• For non-reactive constituents (e.g., Cl, Na, K), concentration data plotted against the L/S ratio showed good agreement across scales, indicating successful extrapolation.
• For reactive elements (e.g., chromium, aluminum), the L/S ratio did not provide a reliable means of extrapolation due to kinetic control on reactions.
• The study highlighted the limitations of the L/S ratio for reactive components.

Conclusions:

• The liquid versus solid ratio (L/S) is a viable method for extrapolating the behavior of non-reactive pollutants from laboratory percolation tests to larger scales.
• Extrapolation of reactive pollutant behavior requires more sophisticated approaches, such as coupled chemistry-transport modeling, due to complex reaction kinetics.
• The LIMULE project provides valuable insights into scaling up leaching behavior of waste materials for environmental impact assessments.