"Remediation of thallium-contaminated groundwater by permeable adsorptive barrier"

The deterioration of groundwater quality is a widespread concern mainly originating by accidental discharges and soil/landfills leaching. Permeable Adsorptive Barriers (PAB) represents a challenging in situ remediation technology, which consist of a continuous trench penetrating the aquifer at a full depth. A PAB is filled with an adsorptive material; groundwater flow moves under natural gradient and the remediation naturally occurs. This paper deals with the application of a PAB for the remediation of thallium Tl(I) contaminated groundwater in Falciano del Massico, Italy. The polluted site is a solid waste landfill, where many wastes were dumped over the past decades, particularly during the crisis of waste and landfill management in large areas of the region of Campania (Italy). Sawdust is chosen as reactive material for PAB, as it showed good Tl(I) removal capacity. Based on the hydrogeological and geotechnical characterization of the polluted aquifer, a 3D numerical model is developed to describe pollutant transport and adsorption mechanisms onto the barrier. Numerical simulations are accurately performed over a long time span, by means of Computational Fluid Dynamic approach developed in COMSOL® Multiphysics. PAB configuration and design parameters are determined, in terms of location, shape and main dimensions, using a procedure previously developed. Results shows that the designed PAB is effective for the remediation of the contaminated aquifer, being Tl(I) concentration flowing out the barrier always lower than Italian regulatory limit. Furthermore PAB has been demonstrated to be an efficient long term method for groundwater protection.