Follow-up study on the effects on well chemistry from biological and chemical remediation of chlorinated solvents

Abstract

The enduring effects of injected materials used for the remediation of chlorinated solvents were examined. Approximately two years previous to this study, four different remediation methods were tested in an area located southeast of Oklahoma City, OK. These methods included bioremediation under both anaerobic and aerobic conditions and chemical remediation using Fenton's reagent or KMnO₄. A series of water quality tests performed in this investigation revealed that the bioremediation processes did not introduce any unexpected chemistry. However, the wells that were treated anaerobically still had water with a negative oxidation-reduction potential and had no recontamination with migrating trichloroethylene as opposed to the aerobic wells that had both positive redox potentials and trichloroethylene present. Also, chemical treatment using Fenton's reagent did not result in any long-term changes in the well chemistry, with the exception of inducing a slight acidity. This is due to the facts that addition of iron into the aquifer that is already in contact with iron-rich clay soil had little long-term effects and the radical chemistry with hydrogen peroxide is short-lived due to its reactivity. KMnO₄-based remediation results in deposition of new materials containing manganese in elevated oxidation states that may provide long-term protection against the build up of chlorinated organic compounds.