Geotechnical Characterization and Potential Ecological Risk Assessment from Soil-Like Material Obtained from Landfill Mining

Landfill mining targets the issue of legacy waste at municipal solid waste (MSW) dump sites, and the soil-like material or fine fraction is one of the four primary residues of landfill mining. This fine fraction constitutes around 45-80% of the overall landfill-mined residues, hence its utilization is of the utmost significance. However, due to the distinct waste composition and heterogeneity of the fine fraction, its valorization becomes challenging. This study investigates the geotechnical characterization, heavy metal analysis, as well as the assessment of potential ecological risks caused by fine fraction from landfill mining at the Boragaon dump site in Guwahati, India. The findings indicated that soil-like material is classified as well-graded, non-plastic sand with low specific gravity and bulk density values of 2.15 and 1.01 g/cc, respectively, and high porosity of 69% owing to organic matter. The OMC and MDD values were reported to be 28.75% and 1.32 g/cc, respectively, and the shear strength parameters were determined to be 10.7 kPa and 40.3°, indicating characteristics typical of organic soil. The permeability of the fine fraction was 4.7E10-8 m/s showing medium to low permeability. The fine fraction also demonstrated elevated measures of total heavy metals. Based on the potential ecological risk assessments, Pb had high risk, followed by Cu and Ni contributing to moderate risk, and Cr and Zn contributing to low risks. Given the evident ability of the soil-like material to cause pollution within the geoenvironment, appropriate treatment methods have been suggested.

Keywords: Landfill mining, Fine fraction, Soil-like material, Municipal solid waste, Geotechnical characterization, Potential ecological risk assessment, Heavy metal pollution.