Comparison of percolation to batch and sequential leaching tests: theory and data

Area of Science:

• Environmental Science
• Geochemistry
• Waste Management

Background:

• Leaching tests are increasingly vital for evaluating solid waste, especially concerning groundwater contamination risks.
• Water infiltration is the primary field leaching mechanism, simulated in laboratories using batch and column tests.

Purpose of the Study:

• To compare percolation leaching, using analytical solutions of the advection-dispersion equation, with laboratory batch and sequential leaching tests.
• To validate theoretical models with extensive field and laboratory data from diverse waste materials and soils.

Main Methods:

• Analytical solutions of the advection-dispersion equation were employed.
• Laboratory batch and column leaching tests were conducted on various waste materials and soils.
• Data from field lysimeters and laboratory experiments were comprehensively analyzed.

Main Results:

• Leaching behavior proved independent of test duration and physical dimensions, consistent across field lysimeters and laboratory columns.
• Laboratory batch tests generally over-predicted effluent concentrations compared to column and lysimeter tests.
• Column and lysimeter tests demonstrated good agreement with analytical solutions for specific solutes like chloride and sulfate.

Conclusions:

• Column leaching tests generally provide better reproducibility and theoretical agreement than batch tests, likely due to fewer experimental artifacts.
• Analytical models, even with simplified assumptions like local equilibrium, effectively describe leaching behavior in many waste scenarios.
• The study highlights the reliability of column tests for simulating field leaching processes and assessing groundwater risks.