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

Abstract

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.