Size effect on lysimeter test evaluating the properties of construction and demolition waste leachate

Lysimeters are always utilized to simulate the landfill environmental conditions due to their relatively low expense and the short duration of the research. However, lysimeters tend to be operated with various geometrical characteristics (e.g. height/width ratio and height) which can result in changes to the physical and thermodynamic characteristics, and affect the waste decomposition rates and leaching behavior. Considering these points, in this study, the lysimeter test was conducted using six lysimeters to evaluate the size effect on leachate generation and leaching behavior of construction and demolition waste residue (C&D waste). According to the lysimeter test results, increasing the width of the lysimeter can reduce the potential of side-edge-wall flow, and the filtration water can have a perfect flushing inside lysimeters with shorter lengths. Increasing the height merely results in an increase in upper loading, and results in waste with a denser micro-structure and with closer cohesion at the bottom of the lysimeters, which was not suitable for the leaching out of soluble constituents or heavy metals. The lysimeters with low height/width ratio can promote the leaching behavior and accelerate the dilution of landfill leacahte. In addition, the emission behaviors of some inorganic ions indicate microbial activity can have a significant effect on leaching behavior, which cannot be neglected when researching landfill waste. It is suggested that lysimeters with lower height and a lower H/W ratio are a better choice when investigating leaching behavior or microbial activity. These results contribute to establishing standardized feasible designs for laboratory-scale lysimeter tests.