Long-Term Performance of Zero-Valent Iron Permeable Reactive Barriers: A Critical Review

Abstract

Permeable reactive barriers (PRBs) have shown great promise as an alternative to pump and treat for the remediation of groundwater containing a wide array of contaminants including organics, metals, and radionuclides. Analyses to date have focused on individual case studies, rather than considering broad performance issues. In response to this need, this study analyzed data from field installations of in situ zerovalent iron (ZVI) PRBs to determine what parameters contribute to PRB failure. Although emphasis has been placed on losses of reactivity and permeability, imperfect hydraulic characterization was the most common cause of the few PRB failures reported in the literature. Graphical and statistical analyses suggested that internal E H , influent pH, and influent concentrations of alkalinity, NO 3 Ϫ and Cl Ϫ are likely to be the strongest predictors of PRBs that could be at risk for diminished performance. Parameters often cited in the literature such as saturation indices, dissolved oxygen, and total dissolved solids did not seem to have much predictive capability. Because of the relationship between the predictive parameters and corrosion inhibition, it appears that reactivity of the ZVI, rather than the reduction in permeability, is more likely the factor that limits PRB longevity in the field. Due to the sparseness of field monitoring of parameters such as E H , the data available for these analyses were limited. Consequently, these results need to be corroborated as additional measurements become available.

Effect of mineral reactions on the hydraulic properties of unsaturated soils: Model development and application

“…This allows for the simulation of numerous applied hydro-geochemical environmental engineering problems where mineral reactions have an important influence on the physical properties of partially saturated soils. Possible applications include vadose zone biodegradation processes [31,32], water management practices and irrigation techniques in arid and semiarid areas [33][34][35], salinity management [36][37][38][39] and the assessment of the longterm performance of reactive barriers [40][41][42][43][44][45][46]. Below, we present the theoretical model derivation followed by applications of the model to the case of kinetic halite dissolution in different moisture conditions and calcite precipitation due to cation exchange.…”

Characterizing the reactivity of metallic iron in Fe0/EDTA/H2O systems with column experiments

“…Iron-based permeable reactive barriers (iron walls) have been successfully used as an efficient in situ remediation technology for groundwaters contaminated with various organic and inorganic compounds over the past 15 years [1][2][3][4][5]. The real mechanism of contaminant 1 removal is yet to be elucidated.…”

“…The real mechanism of contaminant 1 removal is yet to be elucidated. Despite a broad consensus on reductive transformations [1] whereas metals, metalloids and radionuclides may be removed via reductive precipitation, surface adsorption or complexation, or co-precipitation with the Fe oxyhydroxides that are generated in the system [2][3][4]. The validity of this concept is progressively questioned [6][7][8][9][10][11][12].…”

Advances in Electrokinetic Remediation for the Removal of Organic Contaminants in Soils

“…The main advantages of the PRB are the stable operation for long treatment time, even several years, with very low invest-ment and maintenance costs. Anyway, the limited results found in several application impulse the research in several directions in order to improve the removal of the contaminants [53]. One possibility is the combination of the PRB with electrokinetic remediation.…”