Presentation Description
Coupling Surfactants with Permanganate for PCE DNAPL Removal: Coinjection or Sequential Application as Delivery Methods
Surfactant-enhanced aquifer remediation (SEAR) and in situ chemical oxidation (ISCO) are two in situ flushing technologies that have shown promise for dense nonaqueous phase liquid (DNAPL) remediation. In that SEAR and ISCO are often effective as stand-alone technologies, it is reasonable that with proper engineering and design, coupling of these two technologies may be a functional strategy for remediation of DNAPL-contaminated sites. The coupling of in situ flushing remedial agents may be accomplished in two ways: (1) coinjection of surfactants (for enhanced PCE solubilization) with oxidants (for DNAPL mass destruction), or (2) sequential application of treatments using SEAR for pooled or high saturation zones, followed by ISCO as a polishing step for remaining residual and dilute plume treatment. Batch screening experiments were completed to evaluate the compatibility of coupling surfactants/cosolvents with chemical oxidants in a simulated groundwater matrix. Batch screening studies were performed with 72 surfactants and 8 cosolvents in the presence of the oxidant potassium permanganate (KMnO4). Oxidant and manganese dioxide solids (MnO2(s)) concentrations were measured at sampling time points from 3-336 hours. In addition, batch experiments were performed to quantify the rate at which KMnO4 oxidizes PCE DNAPL over a range of permanganate and surfactant concentrations. In a series of batch reactors, aqueous phase PCE concentrations were monitored over time with excess surfactant and oxidant concentrations ranging from 5 to 30 g/l. Analysis of the data was performed to quantify the oxidation reaction order with respect to PCE and KMnO4 in the presence and absence of surfactants and the reaction rate constants.

One-dimensional (1-D) column studies and two-dimensional (2-D) flow-through cell experiments were then used to investigate coupling SEAR with ISCO of tetrachloroethene (PCE) DNAPL for mass destruction. The anionic surfactants Aerosol OT and Dowfax 8390 were found to be compatible with KMnO4 and were selected for use in the 2-D cell experiments. Two delivery methods were investigated: (1) coinjection of surfactants with KMnO4 and, (2) sequential application of surfactants followed by a KMnO4 flush. For the column studies the effluent PCE, chloride, permanganate, and surfactant concentrations were measured. For the 2-D cell experiments, water quality samples were collected from eight point sampling ports, as well as effluent samples. Samples were analyzed for PCE, chloride, and permanganate. At the conclusion of the experiments, the mass of PCE removed and amount MnO2(s) generated were quantified by destructively analyzing the 1-D columns and 2-D cells.