EA was contracted through the Army Contracting Command to demonstrate the remediation of simulated mustard agent-contaminated soils with a thermal desorption unit (TDU) system. Traditionally, agent-contaminated soils are incinerated to destroy any remaining chemical or biological agents present in the soil. EA and our partners, TD*X Associates, LP and El Dorado Engineering, designed a demonstration project to test the effectiveness of an indirect thermal desorption unit (ITDU). Performed in Robstown, Texas using a commercial scale ITDU, owned and operated by TD*X Associates, a series of nine tests were conducted over 36 continuous hours on clay-type soils with moisture contents ranging from approximately 20 to 30% by weight, spiked with simulated mustard agent at concentrations ranging from 525 to 3,440 milligrams per kilogram.
The demonstration tests showed conclusively that non-incineration thermal desorption technology will remediate simulant spiked soils to a condition that correlates to the Health-Based Environmental Standards for mustard of less than 0.010 milligrams per kilogram (<10 micrograms per kilogram) as specified by the U.S. Army Institute of Public Health, and achieve a commensurate removal efficiency of greater than 99.99% removal of simulant from the soil feed. An Addendum to the Test Report was prepared to provide recommended conceptual designs of two purpose-built ITDU systems for consideration by the government:
- A “high capacity” continuous feed ITDU with a nominal capacity of approximately 2.0 cubic yards per hour
- A “low capacity” batch feed ITDU with a nominal capacity of approximately 0.25 cubic yards per hour
- Discussion of the relevant EPA performance and emissions standards governing the design and operation of the ITDU
- Description of the ITDU process including process flow diagrams and equipment design and sizing calculations
- Cost estimates for the mobilization, setup, operation, teardown, and demobilization of the ITDU