Assessment of Traditional Biosolids Disposal Methods for Biosolids Contaminated with Bacillus globigii Spores
Citation:
Burdsall, A., M. Magnuson, J. Szabo, AND J. Heckman. Assessment of Traditional Biosolids Disposal Methods for Biosolids Contaminated with Bacillus globigii Spores. 2023 U.S. Environmental Protection Agency (EPA) International Decontamination Research and Development Conference, Charleston, SC, December 05 - 07, 2023.
Impact/Purpose:
Should biosolids be contaminated with an intentional malicious release or natural outbreak of Bacillus anthracis spores, a water resource recovery facility (WRRF) may need to consider whether their treatment processes can sufficiently inactivate this pathogen. The three methods commonly employed to treat biosolids (lime stabilization, aerobic composting, and incineration) were investigated in the study described in this presentation through literature review and bench-scale experimentation. This research seeks to understand the parameters of these traditional methods of pathogen treatment in wastewater biosolids that may lead to the organisms surviving treatment. The literature research indicated that lime stabilization introduces calcium ions that the organism uses during sporulation, making it counterproductive to the goal of spore inactivation. Therefore, the experimentation in this investigation focused on aerobic composting and incineration using laboratory-scale models with a drum composter and a bench scale fluidized bed furnace incinerator to mimic aspects of full-scale systems. Conditions were identified that might permit viable Bacillus spores to survive treatment. The results from this investigation may help WRRFs to assess the methods their facility uses to treat biosolids and how they might be able to adjust their system to meet the needs for treatment of Bacillus contaminated material that enters their facility.
Description:
Should biosolids be contaminated with an intentional malicious release or natural outbreak of Bacillus anthracis spores, a water resource recovery facility (WRRF) may need to consider if their treatment processes can sufficiently inactivate this pathogen. Three methods commonly employed to treat biosolids--lime stabilization, aerobic composting, and incineration—were investigated in the study described in this paper through literature review and bench-scale experimentation. This research seeks to understand the parameters of these traditional methods of pathogen treatment in wastewater biosolids that may lead to the organisms surviving treatment. The literature component of this investigation indicated that lime stabilization introduces calcium ions that the organism uses during sporulation, making it completely counterproductive to the goal of spore inactivation. Therefore, the experimental component of this investigation solely focused on aerobic composting and incineration. Although one 60°C control experiment inactivated Bacillus globigii to below detection limits, aerobic composting could not do so due to difficulty in achieving and maintaining sufficient temperature to inactivate Bacillus globigii without also inactivating the organisms that perform aerobic composting. In a bench-scale fluidized bed incinerator designed to mimic full-scale incinerators, there were conditions under which incineration may leave viable organisms, particularly when the contaminated biosolids were fairly dry upon entering the incinerator. The results from this investigation may help WRRFs to assess the methods their facility uses to treat biosolids and their ability to answer the needs for treatment of Bacillus contaminated material that enters their facility.