ORIN successfully implemented a pilot study combining in-situ and exsitu chemical oxidation to treat contaminated soil and groundwater at a manufacturing facility. Chlorinated hydrocarbons were the remedial drivers. However, during the tank pull and subsequent ex-situ remediation, a large quantity of petroleum hydrocarbons was also present. ORIN’s approach saved the client approximately $65K over traditional remediation approaches.

Site Characteristics:

  • Site: Manufacturing facility near Dallas, TX.
  • Geology: silty sand with gravel lenses.
  • Groundwater velocity: average 10-3 cm/sec
  • Contaminants:
    • 41 mg/L PCE
    • 3 mg/L TCE
    • 38 mg/L DCE

Remediation Approach:

  • Treatment chemistry: Sodium permanganate and Fenton’s Reagent.
  • Treatment application: Chemical injection through direct push and mixing of chemical and soil with an excavator.

Chemistries used during injection

A benefit of a permanganate remediation approach is the complete reaction of the contaminant without the formation of intermediate compounds commonly found with biodegradation. The Fenton’s Reagent treatment chemistry includes the addition of acid to reduce the pH to < 5 and an iron catalyst.

The preferred Fenton’s Reaction is:

  • Hydrogen Peroxide + Ferrous Iron ➜ Hydroxyl Radical +
  • Hydroxyl Ion + Ferric Iron

The hydroxyl free radical is an extremely powerful oxidizer (second only to fluorine) against organic compounds.

Summary of Implementation

The purpose of the pilot study was to provide information on the feasibility and logistics of full-scale treatment. ORIN injected sodium permanganate side and up gradient of the excavation. During the ex-situ remedial phase, permanganate was seen below grade as the excavator scraped the boundaries of the excavation. Evidence of oxidant influence was observed visually during the ex-situ implementation and observed during the injection by the increase of key groundwater parameters such as DO and ORP in monitoring wells within the plume.

Effectiveness

Post treatment sampling in June 2006. Awaiting approval of full-scale implementation.

The Bottom Line

Performing the pilot study demonstrated the effectiveness and feasibility for combining in-situ and ex-situ chemical oxidation, reducing costs by $65K over traditional remediation approaches.