Modeling the Permeability Loss of Metallic Iron Water Filtration Systems

Over the past 30 years the literature has burgeoned with in situ approaches for groundwater remediation. Of the methods currently available, the use of metallic iron (Fe 0 ) in permeable reactive barrier (PRB) systems is one of the most commonly applied. Despite such interest, an increasing amount of experimental and field observations have reported inconsistent Fe 0 barrier operation compared to contemporary theory. In the current work, a critical review of the physical chemistry of aqueous Fe 0 corrosion in porous media is presented. Subsequent implications for the design of Fe 0 filtration systems are modeled. The results suggest that: (i) for the pH range of natural waters (>4.5), the high volumetric expansion of Fe 0 during oxidation and precipitation dictates that Fe 0 should be mixed with a non‐expansive material; (ii) naturally occurring solute precipitates have a negligible impact on permeability loss compared to Fe 0 expansive corrosion; and (iii) the proliferation of H 2 metabolizing bacteria may contribute to alleviate permeability loss. As a consequence, it is suggested that more emphasis must be placed on future work with regard to considering the Fe 0 PRB system as a physical (size‐exclusion) water filter device.