Enhancement of Landfill Leachate Attenuation in Sandy Soil Using Compost Amendment: A Soil Column Study

ABSTRACT

Soil's attenuation capacity is essential for protecting structures and ecosystems from natural and anthropogenic disturbances. This study investigates the natural attenuation capacity of soil using controlled laboratory column experiments to demonstrate its ability to adsorb, retain, and partially degrade leachate contaminants, thereby limiting their transport to groundwater resources. This study used two vertical soil columns: one containing poorly graded sand and the other containing the same soil enhanced with a 3:2 compost‐to‐soil ratio to increase attenuation. The leachate samples show high levels of organic pollutants, inorganic constituents, and heavy metals. The preliminary metal concentration pattern in the initial soil followed the order Fe > Al > Zn > Cr > Cu > Pb > Ni ≈ Cd, indicating the dominance of Fe and Al among native soil constituents. The pretreated leachate was percolated through both columns for 30 days under ambient laboratory conditions. The influent and effluent samples from the columns were tested for pH, electrical conductivity (EC), ammoniacal nitrogen, sulfate, phosphate, nitrate, biochemical oxygen demand (BOD), chemical oxygen demand (COD), total suspended solids (TSS), total dissolved solids (TDS), alkalinity, total hardness (TH), calcium, chloride, and heavy metals. The results reveal that the compost‐amended soil column removed more heavy metals than the natural column. The soil medium's capacity to retain nutrients is demonstrated by the consistent decrease in phosphorus concentration from leachate to effluent. Soil modification altered pH, electrical conductivity, and hardness. BOD, COD, and chloride concentrations dropped significantly in the modified column. Results indicate that natural soil possesses a significant ability to reduce leachate pollutants, but adding organic amendments, like compost, boosts its contaminant‐removal efficiency.