You are here:
LABORATORY MICROCOSM EXPERIMENTS OF OXIDATION PROCESSES AFTER STEAM INJECTION
Citation:
Davis*, E L. LABORATORY MICROCOSM EXPERIMENTS OF OXIDATION PROCESSES AFTER STEAM INJECTION. Presented at Third International Conference on Remediation of Chlorinated & Recalcitrant Conpounds, Monterey, CA, 05/20-23/2002.
Description:
Aggressive thermal methods such as steam injection or resistive heating are known to be effective for the recovery of many types of volatile and semivolatile compounds. It has been suggested that oxidation or other chemical reactions that occur at remediation temperatures can aid in the recovery of contaminants or can provide a ?polishing step' by oxidizing small amounts of residual contaminants. Previous laboratory experiments have shown that under conditions of high temperature (up to 125 C) and pressure (500 psi), many different kinds of contaminants can be oxidized. The laboratory experiments presented here are aimed at determining whether these oxidation process can occur under conditions that are likely to be present in the subsurface after a thermal remediation.
Microcosm experiments were run using soils from two different wood preserver sites that had been steamed in the laboratory. The microcosm experiments were meant to test three sets of conditions that may be found after a steam injection in the field: 1) high temperature and high water content from the injected steam, 2) rapid groundwater infiltration which cools the soil to ambient temperatures and brings a fresh supply of the naturally occurring micoroganisms, and 3) the vadose zone where the soils would remain hot but there would be a small moisture content.
In all three cases, three lines of evidence are looked for to determine if oxidation of the residual contaminants is occurring. First, oxygen is measured in the water or air to determine if there is a measurable disappearance of oxygen from the system. Second, the soil and water are analyzed for polynuclear aromatic compounds (PAHs), the main contaminants at these sites, to determine if they are disappearing. Third, the soil and water are analyzed for oxygenated intermediates of the PAHs, to determine if they are being formed by oxidation reactions. Results to date seem to indicate that oxygen is being consumed in all three cases. Analytical results show some compounds that were not in the original soil. The compounds that form in the steamed soil for each of the cases will be discussed.