Long-term Performance of Permeable Reactive Barriers Using Zero-valent Iron: An Evaluation at Two Sites; Environmental research brief

摘要

Research described in this research brief explores the geochemical and microbiological processes occurring within zero-valent iron treatment zones in permeable reactive barriers that may contribute to decreases in iron reactivity and decreases in reaction zone permeability that, in turn, may eventually lead to system plugging and failure. Using advanced surface analytical techniques together with detailed coring and water sampling programs at two geographically, hydrogeologically, and geochemically distinct iron barrier installation sites, specific objectives of this research project were to: 1) Characterize the type and nature of surface precipitates forming over time at the upgradient aquifer/iron interface, within the iron zone, and at the downgradient/iron interface. 2) Develop conceptual models that predict the type and rate of precipitate formation based on iron characteristics and water chemistry. 3) Identify type and extent of microbiological activity upgradient, within and downgradient in at least one of the chosen sites to evaluate microbiological response or effects from emplaced iron into an aquifer system. 4) Develop practical and cost-effective protocols for long-term performance assessments at permeable reactive barrier installations.