Remediation of Thallium-contaminated Groundwater by Permeable Adsorptive Barrier

A two-dimensional analytical model for heavy metal contaminants transport in permeable reactive barrier

Permeable reactive barrier (PRB) remediation technology has been widely used in the remediation of groundwater contamination. In numerical simulations, neglecting the non-uniform distribution of heavy metal contamination along the depth may lead to deviations between simulation results and reality. The distribution of heavy metals in the soil layer around a non-ferrous mining area in Hezhou, Guangxi, southern China was investigated, and it was found that the standard Gaussian function could well describe the non-uniform distribution of heavy metals in the soil layer. A two-dimensional analytical model solved by the finite element method was used to simulate the migration process of heavy metal contamination in the aquifer and PRB. The results show that the uniform distribution of contaminants along the depth ignores the dilution effect, which may underestimate the service life of the PRB and lead to an overly conservative design of the PRB. The breakthrough time of the PRB decreases with the increase of the maximum initial concentration (C_in,max) and the high concentration range (σ), and increases almost linearly with the barrier thickness (L_w). An optimal design method for PRB location and thickness is proposed, which can provide a reference for the engineering application of PRB.

An innovative in-situ DRAINage system for advanced groundwater reactive TREATment (in-DRAIN-TREAT)

The removal of groundwater contamination is a complex process due to the hydro-geochemical characteristics of the specific site, related maintenance and the possible presence of several types of pollutants, both organic and inorganic. In recent decades, there has been an increasing drive towards more sustainable treatment for contaminated groundwater as opposed to "intensive" treatments, i.e. with high requirements for onsite infrastructure, energy and resource use. In this study, a new remediation technology is proposed, combining the use of advanced drainage systems with adsorption processes, termed "In-situ reactive DRAINage system for groundwater TREATment" (In-DRAIN-TREAT). By taking advantage of the groundwater natural gradient, In-DRAIN-TREAT collects the contaminated groundwater via a drainage system and treats the polluted water directly into an active cell located downstream, avoiding external energy inputs. Preliminary results indicate the applicability and high efficiency of In-DRAIN-TREAT when compared with a permeable reactive barrier (PRB). In-DRAIN-TREAT is applied to remediate a theoretical aquifer with low permeability, contaminated by a 13 m wide hexavalent chromium (Cr^VI) plume. This is achieved in less than a year, via a drain DN500, 32 m long, a 30 m³ treatment cell filled with activated carbon and no energy consumption. A comparison with permeable barriers also shows a preliminary 63% volume reduction, with a related 10% decrease of remediation costs.