Using a dense oxidizing agent to remediate a DNAPL

Abstract

Fenton's reagent (hydrogen peroxide and ferrous iron) was evaluated for its use in remediating trichloroethene (TCE) in a loess soil over a fractured limestone in Missouri. Fenton's reagent, a dense liquid, has the potential to follow similar pathways as product TCE, a dense non-aqueous phase liquid (DNAPL). Bench-scale testing was carried out to assess the performance of Fenton's reagent in oxidizing TCE both in water and as a non-aqueous phase. The investigation evaluated the rate of the reaction, the quantity of Fenton's reagent required for treatment, and the by-products of the reaction. Fenton's reagent effectively oxidized non-aqueous phase and dissolved TCE, rapidly reducing the concentration from saturation (1,100 mg/L) to less than 2 μg/L TCE concentrations decreased to below detection within 1 day of reagent addition. By-products of the incomplete reaction included tetrachloroethane, trichloroethane, dichloropropene, chloroform, and carbon tetrachloride. The treatment effectiveness was directly related to the concentration of Fenton's reagent; 100 mL of Fenton's reagent (at 3%) destroyed 0.38 mL of the TCE solvent. Given this ratio, to completely convert 500 gallons of TCE would require over 10,000 gallons of the reagent.