THE USE OF FENTON'S REAGENT TO OXIDIZE 1,1-BIPHENYL PRODUCT AT THE BEDROCK INTERFACE AND THE SUBSEQUENT EFFECT ON BEDROCK GROUNDWATER

Since EPA Region 9 established a Preliminary Remediation Goal (PRG) for the constituent 1,1- biphenyl in October 1999, ARCADIS has been exploring methods for remediating this semi-volatile organic compound at sites that used the heat transfer product Dowtherm° A. Dowtherm° A consists of 27% biphenyl and 73% biphenyl ether, has a specific gravity of 1.050 to 1.075 at 25 degrees C, a solubility in water of 13.8 ppm at 15 degrees C, and is immiscible in water. There are two distinct source areas of Dowtherm° A at the subject site: the Dowtherm° heaters and the recirculation pump. Dowtherm° A was present as pure product in vadose zone soils prior to source removal, and residual product remains at the bedrock interface and within the highly fractured zone of within the bedrock. It exists as a dense, non-aqueous phase liquid (DNAPL) in groundwater directly beneath the source areas. Groundwater is present only in the bedrock aquifer at the recirculation pump source area; however, downgradient of the recirculation pump, the bedrock interface is found at deeper elevations and 1,1-biphenyl and biphenyl ether are detected in the saprolite aquifer at concentrations greatly exceeding 1% of the solubility. Prior to conducting the full-scale project, a treatability study was conducted to evaluate the effectiveness of three oxidizers: Fenton's reagent; hydrogen peroxide; and potassium permanganate. As a result of this study, Fenton's reagent was selected for use at the recirculation pump source area. A pilot study was also conducted using Oxygen Release Compound (ORC°) in the Dowtherm° heater area where the contaminants existed solely in the overburden.