ORIN successfully implemented pilot-scale, in-situ chemical remediation using sodium permanganate to treat chlorinated solvents in bedrock. Chlorinated solvent levels were reduced from 2,000 micrograms per liter (ug/L) to less than 12-ug/L over a three-month period. ORIN’s approach saved the client approximately $45K over traditional remediation approaches.

Site Characteristics

  • Site: Farm field/wooded lot near Hudson, Wisconsin.
  • Geology: Sandstone and limestone bedrock 160 feet below ground surface (ft. bgs)
  • Groundwater velocity: 10-3 cm/sec
  • Contaminants: Trichloroethene (TCE) – 2,000 ug/L

Remediation Approach

  • Treatment chemistry: Sodium permanganate.
  • Treatment application: In-situ chemical injection through a series of nested temporary injection wells.

Chemistries used during injection

Permanganates have been shown to reduce levels of chlorinated solvents in multiple remediation designs without the formation of intermediate compounds commonly found with biodegradation. A benefit of a permanganate remediation approach is the complete mineralization of the contaminant.

For example, the breakdown of TCE with sodium permanganate is as follows:

  • 2NaMnO4 + C2HCl3 → 2MnO2 + 2Na+ + 3Cl- + H+

Summary of Implementation

The purpose of the pilot study was to provide information on the feasibility and logistics of full-scale treatment. Contaminant levels three months after the pilot study were reduced to 12 ug/L. The chemistry was designed for the oxidation of TCE in the groundwater at the site. Prior to ORIN mobilization, three nested temporary injection wells were installed. Five injection wells, screened at different intervals, were installed at each of the three locations. Each of the fifteen injection wells received approximately 150 gallons of permanganate treatment chemistry. Evidence of oxidant influence was observed during the injection by the increase of key groundwater parameters such as DO, ORP and conductivity in monitoring wells down and side gradient while color change occurred in wells within the targeted plume area.

Effectiveness

Three months following the injection, monitoring wells were purged and sampled for VOC constituents. Average TCE concentrations were reduced from 2,000 ug/L to 12 ug/L within the pilot test area. Down gradient wells outside of the active injection area also showed a significant reduction.

The Bottom Line

ORIN successfully reduced contaminant levels in the pilot study area by injecting permanganate chemistry through a series of injection wells over a three-month period. Performing the pilot study demonstrated the effectiveness and feasibility for full-scale injection at this site, reducing full-scale costs by $370K and shortening project timeframe by years over traditional remediation approaches.