EFFECTIVENESS OF PERMEABLE REACTIVE BARRIER (PRB) ON HEAVY METAL TRAP IN AQUIFER AT SOLID WASTE DUMPSITE: A SIMULATION STUDY

Open dumping of solid waste causes a serious environmental impact on groundwater due to contamination of landfill leachate rich in heavy metals. Identification of contaminant flow and implementation of remediation technologies, such as permeable reactive barriers (PRB) are highly demanded and applicable. In this study, a groundwater model, Geo-Environmental Risk Assessment System (GERAS) has been used to simulate two-dimensional heavy metal transport in an aquifer at solid waste dumpsite and to estimate the effectiveness of virtual PRB on trap heavy metals. First, two cases were examined: 1) Open dumping of waste located above the aquifer and 2) Buried dumping of waste into the aquifer. Concentration changes of heavy metals (Cd and Pb) inside the aquifer beneath the waste unit, inside PRB, upstream and downstream points to PRB were examined by changing the hydraulic gradient, distribution coefficient, and pollution load. Results showed the numerical simulations well captured the wash-out process of heavy metals from the pollutant source. The time required for full wash-out was highly dependent on the hydraulic gradient, distribution coefficient, pollution load and the way of waste dumping. In Case 2, a sudden pollution plume was observed with high heavy metal concentrations, by creating greater risk at the downstream. Next, a virtual PRB was set in downstream of the aquifer by installing a section with a high heavy metal adsorption capacity (based on previous studies). Results showed that in both cases, the virtual PRB well trapped the target metals and reduced the contamination level less than the effluent water quality standards.