Thermal inactivation of <italic>Bacillus anthracis</italic> surrogate spores in a bench-scale enclosed landfill gas flare: Fid-Bau Portal

Thermal inactivation of Bacillus anthracis surrogate spores in a bench-scale enclosed landfill gas flare

McBrian Tufts, Jenia A. / Rosati, Jacky A.

A bench-scale landfill flare system was designed and built to test the potential for landfilled biological spores that migrate from the waste into the landfill gas to pass through the flare and exit into the environment as viable. The residence times and temperatures of the flare were characterized and compared to full-scale systems.

Geobacillus stearothermophilus and Bacillus atrophaeus, nonpathogenic spores that may serve as surrogates for Bacillus anthracis, the causative agent for anthrax, were investigated to determine whether these organisms would be inactivated or remain viable after passing through a simulated landfill flare. High concentration spore solutions were aerosolized, dried, and sent through a bench-scale system to simulate the fate of biological weapon (BW)-grade spores in a landfill gas flare. Sampling was conducted downstream of the flare using a bioaerosol collection device containing sterile white mineral oil. The samples were cultured, incubated for seven days, and assessed for viability.

Results showed that the bench-scale system exhibited good similarity to the real-world conditions of an enclosed standard combustor flare stack with a single orifice, forced-draft diffusion burner. All spores of G. stearothermophilus and B. atrophaeus were inactivated in the flare, indicating that spores that become re-entrained in landfill gas may not escape the landfill as viable, apparently becoming completely inactivated as they exit through a landfill flare.

Following the release of biological weapons and subsequent cleanup efforts, large quantities of potentially contaminated wastes may be generated and require disposal. Landfill disposal is an option. However, data demonstrating the fate of viable pathogenic spores in a landfill do not exist in the literature. These data may be of interest to emergency response authorities, state and local permitting agencies, and waste management industries in the event that biological weapons residues from building decontamination wastes are transported to a landfill for disposal. The methodology developed here and the subsequent results may also be relevant to other landfill migration and release concerns, such as the release of other toxic particulate-based contaminants.

The U.S. Environmental Protection Agency through its Office of Research and Development funded the research described here under Cooperative Training Agreement number CR83323601 to the Department of Environmental Sciences and Engineering, University of North Carolina at Chapel Hill. This paper has been subject to Agency review, but does not necessarily reflect the views of the Agency. No official endorsement should be inferred.