Thermal inactivation of viable Geobacillus stearothermophilus and Bacillus atrophaeus spores in a bench-scale landfill gas flare

Abstract

A bench-scale, landfill flare system was designed and built to test the potential for heat-resistant spores to survive the flaring process and enter the environment. The residence times and temperatures of the flare were characterized and compared to full-scale systems. Experiments were conducted using Geobacillus stearothermophilus and Bacillus atrophaeus spores as surrogates for Bacillus anthracis. Spore solutions were aerosolized, dried, and sent through the bench-scale system. Sampling was conducted downstream of the flare using a bioaerosol collection device. The samples were cultured, incubated for seven days, and assessed for viability. Results showed that the bench-scale, landfill flare system was comparable to a full-scale combustor flare with a single-orifice diffusion burner. All spores of G. stearothermophilus and B. atrophaeus were inactivated in the bench-scale system, suggesting that spores that pass through the flare in a full-scale system will become inactivated as well