Capstone Report on the Application, Monitoring, and Performance of Permeable Reactive Barriers for Ground-Water Remediation: Volume 1: Performance Evaluations at Two Sites
Abstract
Research results discussed in this report explore the geochemical and microbiological processes within zerowalent iron Permeable Reactive Barriers (PRBs) that may contribute to changes through time in iron reactivity and decreases in reaction zone permeability. Two full-scale PRBs were evaluated in this study: the U.S. Coast Guard Support Center PRB located near Elizabeth City, North Carolina, and the Denver Federal Center PRB in Lakewood, Colorado. Detailed water sampling and analysis, core sampling, and solid-phase characterization studies were carried out to: 1) evaluate spatial and temporal trends in contaminant concentrations and key geochemical parameters; 2) characterize the type and nature of surface precipitates forming over time in the reactive barriers; and 3), identify the type and extent of microbiological activity within and around the reactive. Trends in geochemical parameters (e.g., pH and oxidation-reduction-potential) may signal changes in system performance, but no clear correlations between these parameters and decreased system performance have been observed to date at the sites studied. Long-term trends in geochemical parameters are consistent with contaminant removal trends observed at both sites. Spatial and temporal variations in the concentration distribution of terminal electron accepting species (e.g., sulfate), specific conductance, and Eh suggest that both anaerobic iron corrosion and microbial activity play important roles in controlling the oxidation-reduction potential in iron barriers. Low Eh values (<%1OO mV relative to the standard hydrogen electrode) and decreases in the specific conductance of ground water between upgradient contaminant plumes and sampling points within reactive iron media are consistently observed in normally operating PRB systems.
Document Details
- Document Type
- Technical Report
- Publication Date
- Aug 01, 2003
- Accession Number
- ADA487285
Entities
People
- Richard T. Wilkin
- Robert W. Puls