Treating Soil Contaminated by Chemical Warfare Agents

Problem/Opportunity

Soils contaminated by chemical warfare agents pose a unique remediation problem for military installations. At Rocky Mountain Arsenal, near Denver, chemical and incendiary munitions have been produced and dismantled since the 1940s. The chemical warfare agents most likely to be encountered at the Arsenal are the blister agents, mustard and lewisite, and the nerve agents, GB and VX. Success in identifying effective remediation technologies will pave the way for full-scale treatment of the Arsenal's agent-contaminated soil. Technologies that Argonne National Laboratory identifies as promising may also have applicability to other kinds of contamination problems.

Approach

Argonne, a pioneer in studying the problem of agent-contaminated soils, is evaluating different treatment technologies for treating such soils at Rocky Mountain Arsenal.

Argonne is helping Rocky Mountain Arsenal choose the most appropiate
remediation path for treating soils contaminated by chemical warfare agents.

The laboratory work, which will be performed on simulants to the agent, has two phases. The first is a small-scale screening of the technologies, using small samples (1 to 20 grams). Experiments are conducted over a wide range of values to establish operational parameters. Findings will help identify a narrower set of values to be tested during the second phase. The second phase features bench-scale feasibility tests using larger (1-kilogram) soil samples, which will provide better insight into the mechanisms of handling large soil volumes.

Argonne is pursuing two cleanup technologies: thermal desorption and solvent washing. Thermal desorption involves the removal of contaminants that have adhered to the soil matrix (adsorption) or are held in voids between particles (absorption). Solvent washing extracts compounds by dissolving them in a fluid. Because the agents in question are highly toxic, more benign compounds with similar chemical properties are used to "spike" test soils in the laboratory.

In thermal desorption, treated soil and off-gases will be analyzed for the simulated agent and expected degradation products. Later, in Phase Two, 1-kilogram soil samples will be treated in an indirectly heated, batch, rotary-kiln desorption unit.

Triethylamine is currently being studied for solvent washing. Laboratory screening will test for triethylamine's solubility with target compounds, maximum extractability, and removal efficiency.

Results

Preliminary to laboratory experiments, Argonne conducted an extensive literature review on agent chemistry, toxicology, decontamination, potential treatment technologies, and applicable laws and regulations. A database of 300 entries was compiled. Using the findings from the literature search, Argonne conducted an evaluation of 26 in-situ and ex-situ technologies. Each technology was screened for cost-effectiveness, implementation potential, and decontamination effectiveness. From these paper studies, Argonne then chose its two candidate technologies to test for feasibility at the laboratory scale: thermal desorption and solvent washing.

Soil spiking, analytical development, and preliminary screening are progressing. There are no data to report as yet.

Future Plans

Both solvent washing and thermal desorption have been tested on pesticide-contaminated soils at Rocky Mountain Arsenal. One of the goals is to use either process to treat pesticide- and agent-contaminated soil simultaneously.

If the experimental program has positive results, commercial vendors will be screened by Argonne and invited to demonstrate their processes with full-scale prototypes. A final evaluation will be prepared for each vendor process, including projected costs. Argonne expects to continue as an unbiased, expert consultant that can screen potential treatments for specific contaminated sites and assist in the testing, evaluation, and selection of appropriate vendors to provide full-scale remediation.

Principal Investigator:

Linda Shem

08May97 mv&ls