Homeland Security Research

Research Highlights

Thermal Destruction of Building Material Contaminants

EPA has initiated a program to investigate chemical/biological agent destruction in incineration systems when the agent in question is bound on common porous building interior materials. The program includes three-dimensional computational fluid dynamics modeling with matrix-bound agent destruction kinetics, bench-scale experiments to determine agent destruction kinetics while the agent is bound on various matrices, and pilot-scale experiments to scale-up the bench-scale experiments to a more practical scale. Finally, model predictions are made to predict agent destruction and combustion conditions in two modern, full-scale incineration systems.

After a building has undergone decontamination activities following a terrorist attack with chemical warfare (CW) agents, biological warfare (BW) agents, or toxic industrial chemicals (TICs), much residual material and waste must be disposed of. This material is termed “building decontamination residue” (BDR). Although the BDR will likely have been decontaminated, trace levels of the contaminants may remain in absorbent and/or porous material such as carpet, fabric, ceiling tiles, office partitions, furniture, personal protective equipment (PPE), and other materials used during decontamination. Much of this material will likely be disposed of in high-temperature thermal incineration facilities, such as medical/pathological waste incinerators, municipal waste combustors, and hazardous waste combustors.

Although pathogens such as Bacillus anthracis present in BDR are killed at typical incineration temperatures, at gas-phase residence times, and at solid-phase residence times, some pathogens may escape the incinerator due to cold spots, bypassing the flame zones, or incomplete penetration of heat through the bed. In the early 1990s, EPA tested commercial hospital waste incinerators by placing large quantities of Geobacillus stearothermophilus (an anthrax surrogate) spores into the combustors. Researchers measured the number of spores leaving in the stack emissions and remaining in the incinerator bottom ash. In certain cases, only a 3-Log reduction in spore concentration was found, despite acceptably high operating temperatures and sufficiently long residence times.

Because of the 2001 anthrax attacks, EPA instituted a research program to investigate the thermal destruction of contaminated BDR, initially including carpeting, ceiling tile, and wallboard. Bench- and pilot-scale tests are now being performed, and a computer model is being developed to predict BDR-bound agent behavior in two commercial incinerator designs. Tested contaminants will include BW simulants (Geobacillus stearothermophilus) and CW simulants (dimethyl methylphosphonate). These tests will examine time/temperature requirements for agent destruction, verify facility compliance with relevant permits (for example, for emissions of nitrogen oxides), attempt to predict potential operational difficulties in full-scale systems, and identify which facilities may or may not be appropriate to handle certain types of BDR.

Although the methodology described in the report is useful for both chemical and biological contaminants, the completed experiments have been limited to biologicals. Bench-scale experiments on CW agent simulants are complete, but no model runs have been performed to compare to the pilot-scale results because no pilot-scale experiments on such simulants are complete.

See Also
Thermal Destruction of CB Contaminants Bound on Building Materials: Experiments and Modeling October 2006