I. Bortone

Remediation of an aquifer polluted with dissolved tetrachloroethylene by an array of wells filled with activated carbon.

In this work, an array of deep passive wells filled with activated carbon, namely a Discontinuous Permeable Adsorptive Barrier (PAB-D), has been proposed for the remediation of an aquifer contaminated by tetrachloroethylene (PCE). The dynamics of the aquifer in the particular PAB-D configuration chosen, including the contaminant transport in the aquifer and the adsorption onto the barrier material, has been accurately performed by means of a computer code which allows describing all the phenomena occurring in the aquifer, simultaneously. A PAB-D design procedure is presented and the main dimensions of the barrier (number and position of passive wells) have been evaluated. Numerical simulations have been carried out over a long time span to follow the contaminant plume and to assess the effectiveness of the remediation method proposed. The model results show that this PAB-D design allows for a complete remediation of the aquifer under a natural hydraulic gradient, the PCE concentrations flowing out of the barrier being always lower than the corresponding Italian regulation limit. Finally, the results have been compared with those obtained for the design of a more traditional continuous barrier (PAB-C) for the same remediation process.

A procedure to design a Permeable Adsorptive Barrier (PAB) for contaminated groundwater remediation.

A procedure to optimize the design of a Permeable Adsorptive Barrier (PAB) for the remediation of a contaminated aquifer is presented in this paper. A computer code, including different routines that describe the groundwater contaminant transport and the pollutant capture by adsorption in unsteady conditions over the barrier solid surface, has been developed. The complete characterization of the chemical-physical interactions between adsorbing solids and the contaminated water, required by the computer code, has been obtained by experimental measurements. A case study in which the procedure developed has been applied to a tetrachloroethylene (PCE)-contaminated aquifer near a solid waste landfill, in the district of Napoli (Italy), is also presented and the main dimensions of the barrier (length and width) have been evaluated. Model results show that PAB is effective for the remediation of a PCE-contaminated aquifer, since the concentration of PCE flowing out of the barrier is everywhere always lower than the concentration limit provided for in the Italian regulations on groundwater quality.

Permeable Adsorptive Barrier (PAB) for the remediation of groundwater simultaneously contaminated by some chlorinated organic compounds

In this paper, a Permeable Reactive Barrier (PRB) made with activated carbon, namely a Permeable Adsorptive Barrier (PAB), is put forward as an effective technique for the remediation of aquifers simultaneously contaminated by some chlorinated organic compounds. A design procedure, based on a computer code and including different routines, is presented as a tool to accurately describe mass transport within the aquifer and adsorption/desorption phenomena occurring inside the barrier. The remediation of a contaminated aquifer near a solid waste landfill in the district of Napoli (Italy), where Tetrachloroethylene (PCE) and Trichloroethylene (TCE) are simultaneously present, is considered as a case study. A complete hydrological and geotechnical site characterization, as well as a number of dedicated adsorption laboratory tests for the determination of activated carbon PCE/TCE adsorption capacity in binary systems, are carried out to support the barrier design. By means of a series of numerical simulations it is possible to determine the optimal barrier location, orientation and dimensions. PABs appear to be an effective remediation tool for the in-situ treatment of an aquifer contaminated by PCE and TCE simultaneously, as the concentration of both compounds flowing out of the barrier is everywhere lower than the regulatory limits on groundwater quality.

A Heuristic Procedure to Optimize the Design of a Permeable Reactive Barrier for In Situ Groundwater Remediation

This paper deals with a procedure to optimize the design of permeable reactive barrier (PRB) built with activated carbon for the in situ remediation of a polluted aquifer. A simulation-based heuristic procedure is developed to define, with an iterative procedure, the optimal position and geometrical dimensions of the barrier itself, which simultaneously assure the respect of pollutant concentration limits and minimum barrier size. A computer code is used to describe the field motion of the aquifer, the contaminant transport and the adsorption phenomena occurring inside the barrier. A real aquifer polluted by tetrachloroethylene (PCE) situated in the area north of Naples (Italy) is presented as a case study. Simulation results show that a PRB formed by sections of different width, tuned to the different values of PCE concentration in the plume, can assure an effective remediation of the site.

Design of Permeable Adsorptive Barriers (PABs) for groundwater remediation by COMSOL Multi-physics simulations

AbstractThis work deals with an innovative approach to design a permeable reactive barrier (PRB) filled with activated carbon, namely a permeable adsorptive barrier (PAB). A 2D numerical model, solved using a finite element approach via COMSOL Multi-physics, was used to describe the pollutant transport within groundwater and the pollutant adsorption onto the barrier. The PAB design procedure was applied to a benzene-contaminated aquifer situated in the metropolitan area of North Naples (Italy), lately hit the headlines as “Gomorra’s land”. Model results showed that PAB is an effective tool for the remediation of the aquifer under analysis, since the pollutant concentration downstream the barrier resulted everywhere lower than the regulatory limit set for groundwater. A sensitivity analysis was carried out to evaluate the influence of some site parameters on the PAB design, i.e. hydraulic conductivity and dispersivity. Finally, the simulation results allow estimating the long-term efficiency of the treatme...

Application of a discontinuous permeable adsorptive barrier for aquifer remediation. A comparison with a continuous adsorptive barrier

AbstractThis work presents an innovative configuration of a permeable adsorptive barrier (PAB) for the in situ remediation of benzene-contaminated groundwater in the area of Naples (Italy). A PAB is a type of permeable reactive barrier (PRB) made with adsorbing materials (e.g. activated carbon). This particular PAB is a discontinuous permeable adsorptive barrier (PAB-D), consisting in an array of deep passive adsorptive wells whose hydraulic conductivity is higher than the surrounding soil. The design was based on COMSOL Multi-physics® simulations, which allow for the description of pollutant transport in groundwater and adsorption onto the barrier by means of a 2D model solved using a finite element approach. Based on a hydrological and geotechnical characterization of the entire polluted aquifer, the design and optimization of PAB-D parameters (location, orientation, number of wells and dimensions) were defined. The influence of hydraulic conductivity and dispersivity on the total number of wells for a ...