Stimulation of Dechlorination by Membrane-Delivered Hydrogen: Small Field Demonstration

Biological reductive dechlorination can be used to remediate aquifers contaminated with chlorinated solvents. This process can be stimulated with the addition of hydrogen as an electron donor. A small field study was conducted in a trichloroethene (TCE)-contaminated aquifer at the Twin Cities Army Ammunition Plant site in Arden Hills, MN, to determine whether hollow-fiber membranes could be used to deliver hydrogen to the contaminated groundwater to stimulate bioremediation in situ. Nonporous silicone-coated membranes were placed in Geoprobe wells, where they were able to sustain hydrogen delivery over 20 months without a decline in gas transfer performance. High concentrations of hydrogen (168 ± 13 µM) were observed in the wells containing membrane modules. These concentrations were similar to that predicted using a clean water gas transfer gas correlation (255 µM). High acetate concentrations (662 ± 172 µM) were also observed in the wells containing membrane modules during hydrogen addition. The addition of hydrogen via the hollow-fiber membranes stimulated vinyl chloride and ethene formation, likely as a result of the activity of acetotrophic dechlorinators.