Citation:

Mikelonis, A., K. Ratliff, AND S. Youn. Laboratory results and mathematical modeling of spore surface interactions in storm water runoff. JOURNAL OF CONTAMINANT HYDROLOGY. Elsevier Science Ltd, New York, NY, 235:103707, (2020). https://doi.org/10.1016/j.jconhyd.2020.103707

Impact/Purpose:

These findings provide new insights in selecting a nonpathogenic surrogate microorganism to use in field and laboratory studies focused on storm water transport of B. anthracis. B. anthracis is a pathogenic microorganism with a history of terrorist use. This study demonstrated that components of stormwater equalize the surface charge differences between different commonly used surrogates for B. anthracis. It also shows that the runoff water reacted with the surface of concrete and asphalt and that these changes dominated the adhesion predictions. The results are useful in theorizing how to remove pathogenic spores from the surface of materials and indicate that NOM could make the removal of spores from these surfaces by water more challenging. This study provides information to aid in modeling the spread of biological contamination during emergency response and recovery, which informs activities such as creating sampling maps, deciding where to stage waste, and developing strategic decontamination plans.

Description:

Development of numerical models to predict stormwater-mediated transport of pathogenic spores in the environment depends on an understanding of adhesion forces that dictate detachment after rain events. Zeta potential values were measured for Bacillus globgii and Bacillus thuringiensis kurstaki, two common surrogates used to represent Bacillus anthracis, in synthetic baseline ultrapure water and laboratory stormwater. Zeta potential curves were also determined for materials representative of urban infrastructure (concrete and asphalt). These data were used to predict the interaction energy between the spores and urban materials using Derjaguin-Landau-Verwey-Overbeek (DLVO) modeling. B. globgii and B. thuringiensis kurstaki sourced from Yakibou Inc., were found to have similar zeta potential curves, whereas spores sourced from the U.S. military’s Dugway laboratory were found to diverge. In the ultrapure water, the energy barriers between the spores and the urban materials were tunable through compression of the double layer of the spores via changes of ionic strength and pH of the water. In the runoff water, charge neutralization dominated surface processes. The cations, metals, and natural organic matter (NOM) in the runoff water contributed to equalizing the zeta potential values for Dugway B. globgii and B. thuringiensis kurstaki, and drastically modified the surface of the concrete and asphalt. All DLVO energy curves using the runoff water were repulsive. The highest energy barrier predicted in this study was for Dugway B. globgii spores interacting with a concrete surface in runoff water, suggesting that this would be the most challenging combination to detach through water-based decontamination.

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