Citation:

Wood, J., A. Touati, A. Abdel-Hady, D. Aslett, F. Delafield, W. Calfee, E. Silvestri, S. Serre, L. Mickelsen, C. Tomlinson, AND A. Mikelonis. Decontamination of soil contaminated at the surface with Bacillus anthracis spores using dry thermal treatment. JOURNAL OF ENVIRONMENTAL MANAGEMENT. Elsevier Science Ltd, New York, NY, 280:111684, (2020). https://doi.org/10.1016/j.jenvman.2020.111684

Impact/Purpose:

Bacillus anthracis is a naturally occurring bacterium in soils and causes anthrax disease in wildlife, livestock, and humans. It has been suggested that B. anthracis spores may persist for several years in soil. Soils and other outdoor materials or environments will become contaminated with B. anthracis spores in the event of an intentional outdoor release of the biological agent. The efficacy of a decontaminant in inactivating B. anthracis spores is highly dependent on the material with which the spores are associated, and soil remains one of the most difficult materials to decontaminate. Thermal treatment of soil contaminated with B. anthracis soil is a potential remediation option, although the literature is sparse. This research fills some of the data gaps, by providing information and data related to the use of dry heating techniques that can be used for in-situ soil decontamination for soils contaminated with B. anthracis at or near the surface.

Description:

In the event of a wide-area release of Bacillus anthracis spores, soils and other outdoor materials may become contaminated with the biological agent. A study was conducted to assess the in-situ remediation of soil using a dry thermal treatment approach to inactivate a B. anthracis spore surrogate inoculated into soil samples. The study was conducted in two phases, using loam, clay and sand-based soils, as well as biological indicators and spore-inoculated stainless-steel coupons. Initial experiments were performed in an environmental test chamber with temperatures controlled between 80-110 °C, with and without added humidity, and with contact times ranging from 4 h to 7 weeks. Tests were then scaled up to assess the thermal inactivation of spores in small soil columns, in which a heating plate set to 141 °C was applied to the soil surface. These column tests were conducted to assess time requirements to inactivate spores as a function of soil depth and soil type. Results from the initial phase of testing showed that increasing the temperature and relative humidity reduced the time requirements to achieve samples in which no surrogate spores were detected. For the test at 80 °C with no added humidity, 49 days were required to achieve soil samples with no spores detected in clay and loam. At 110 °C, 24 h were required to achieve samples in which no spores were detected. In the column tests, no spores were detected at the one-inch depth at four days and at a two-inch depth at 21 days, for two of the three soils. The experiments described in the study demonstrate the feasibility of using dry thermal techniques to decontaminate soils that have been surficially contaminated with B. anthracis spores.

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