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 tocontamination of landfill leachate rich in heavy metals. Identification of contaminant flow and implementation ofremediation technologies, such as permeable reactive barriers (PRB) are highly demanded and applicable. In thisstudy, a groundwater model, Geo-Environmental Risk Assessment System (GERAS) has been used to simulatetwo-dimensional heavy metal transport in an aquifer at solid waste dumpsite and to estimate the effectiveness ofvirtual PRB on trap heavy metals. First, two cases were examined: 1) Open dumping of waste located above theaquifer and 2) Buried dumping of waste into the aquifer. Concentration changes of heavy metals (Cd and Pb) insidethe aquifer beneath the waste unit, inside PRB, upstream and downstream points to PRB were examined bychanging the hydraulic gradient, distribution coefficient, and pollution load. Results showed the numericalsimulations well captured the wash-out process of heavy metals from the pollutant source. The time required forfull wash-out was highly dependent on the hydraulic gradient, distribution coefficient, pollution load and the wayof waste dumping. In Case 2, a sudden pollution plume was observed with high heavy metal concentrations, bycreating greater risk at the downstream. Next, a virtual PRB was set in downstream of the aquifer by installing asection 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 waterquality standards.