Laboratory tests and modeling of a reactive multibarrier for the remediation of a contaminated aquifer system

This study presents the treatability tests and modeling aimed at dimensioning of an in-situ reactive multibarrier, designed to purify an aquifer contaminated with a range of chlorinated organic compounds and arsenic, with 1,2-dichloroethane (1,2-DCA) presenting a significant resistance to conventional treatments.The remediation strategy involves the implementation of a reactive multibarrier system comprising  two series-connected reactive filters: the first filled with millimetric zerovalent iron (ZVI) to remove arsenic and most of the chlorinated hydrocarbons through abiotic reductive dehalogenation, and the second with granular activated carbon (GAC) to adsorb 1,2-DCA and other residual organic contaminants.To optimize the site-specific design and sizing of the reactive filters, groundwater treatability tests were conducted in the laboratory. Initial batch tests compared various ZVI and GAC types to select the most effective materials. Subsequent column tests assessed the treatment chain's efficacy under flow conditions and determined the longevity of the reactive materials. The results demonstrated the multibarrier's high effectiveness, with the ZVI filter removing 99.9% of several chlorinated solvents and all arsenic, and GAC achieving complete removal of the remaining contaminants to meet water quality standards. Mathematical models were employed to interpret the experimental findings and provide quantitative parameters essential for designing a large-scale multibarrier, such as kinetic constants for contaminant removal, reactive material longevity, and reagent volumes. A multicomponent adsorption model specifically aided in designing the GAC filtration step. he preliminary results of the pilot test, which is still ongoing, confirmed the potentiality of the reactive multibarrier to effectively remediate groundwater in site-specific conditions.