ORIN successfully treated a 600 cubic yard petroleum and chlorinated hydrocarbon contaminated plume with ex-situ chemical oxidation. Petroleum hydrocarbons were reduced from 295ppm to less than 4.4 ppm and chlorinated hydrocarbons were reduced from 200 ppm to non-detect. ORIN’s approach saved the client approximately $125K over a traditional dig and haul approach.
- Site: Window Frame Manufacturing Plant.
- Soil Type: Silty Clay
- Groundwater Velocity: average 10-5 cm/sec
- Treatment chemistry: Fenton’s Reagent (hydrogen peroxide and an iron catalyst)
- Treatment application: Ex-situ remediation utilizing an excavator to mix soil/chemical
Chemistries used during ex-situ remediation
ORIN began ex-situ remediation of soils utilizing Fenton’s Reagent (hydrogen peroxide and an iron catalyst). The Fenton’s Reagent treatment chemistry included the addition of acid to reduce the pH to < 5. The iron catalyst used was ferrous sulfate heptahydrate (FeSO4 • 7H2O).
The preferred Fenton’s Reaction is:
- Hydrogen Peroxide + Ferrous Iron ➜ Hydroxyl Radical + Hydroxyl Ion + Ferric Iron: H2O2 + Fe+2 ➜ OH. + OH- + Fe+3
The hydroxyl free radical is an extremely powerful oxidizer (second only to fluorine) against organic compounds. Residual hydrogen peroxide, due to its unstable characteristics, rapidly decomposes to water and oxygen in the subsurface environment. Soluble iron amendments are precipitated out during conversion to ferric iron.
Summary of Ex-situ Implementation
Ex situ remediation at this site involved the application of the treatment chemistry directly onto the exposed soils. An excavator was present to displace a certain area of soil down to depth. A portion of that soil was then placed back into the excavated hole while the treatment chemistry was being applied to the soil. The excavator would then continually mix the soil and chemicals together until the desired amount of treatment chemistry was applied. More soil was then added from the displaced pile while additional chemical was applied and mixed thoroughly. This process was duplicated until the desired consistency and chemical volume were applied to the entire targeted soil volume.
Two weeks following treatment, soil samples were taken at various locations within the treatment area. Based on this study, Fenton’s Reagent chemistry reduced the mass of contamination by greater than 98 percent. Concentrations were reduced from 295 ppm to less than 4.4 ppm and chlorinated hydrocarbons were reduced from 200 ppm to non-detect within the treatment area.
The Bottom Line
ORIN reduced contaminant levels in the treatment area by utilizing Fenton’s Reagent chemistry. Furthermore, a reduction in cost by $125K and shortening project timeframe over traditional remediation approaches demonstrated ORIN’s effectiveness to asses, formulate and implement a plan of action.