Paula Krauter

A series of polymer solutions were developed for the purpose of immobilizing aerosolized 1–10 μ m sized hazardous biological particles. The polymer solutions were designed as tools for emergency response and remediation personnel. The inhibition of secondary aerosolization and migration of biothreat particles has important implications for public health protection and contamination cleanup. Limiting further dispersion of particles such as Bacillus anthracis spores may reduce inhalation hazards and enhance remediation efficiencies. This study evaluated film-forming polymers that have multiple functional groups capable of attracting and binding particles; these included acrylates, cellulosics, vinyl polymers, and polyurethanes. The selected polymers were combined with appropriate solvents to design solutions that met specific performance objectives. The polymer solutions were then evaluated for key characteristics, such as high adhesion, high elasticity, low density, short drying time, low viscosity, and low surface tension. These solutions were also evaluated for their adhesion to biothreat agent in a series of wind tunnel experiments using highly refined aerosolized Bacillus atrophaeus spores (a simulant for anthrax, 1–3 μ m). Results demonstrated that a polymer solution, an amphoteric acrylate identified as NS-2, was the best candidate for attaching to spores and inhibiting reaerosolization. This polymer solution was anionic, thus providing the electrostatic (coulombic) attraction to cationic spores, had low surface tension, and performed well in wind tunnel tests.

This project examined dry, fluidized spore reaerosolization in a heating, ventilating, and air conditioning duct system. Experiments using spores of Bacillus atrophaeus , a nonpathogenic surrogate for Bacillus anthracis , were conducted to delineate the extent of spore reaerosolization behavior under normal indoor airflow conditions. Short-term (five air-volume exchanges), long-term (up to 21,000 air-volume exchanges), and cycled (on-off) reaerosolization tests were conducted using two common duct materials. Spores were released into the test apparatus in turbulent airflow (Reynolds number, 26,000). After the initial pulse of spores (approximately 10 ¹⁰ to 10 ¹¹ viable spores) was released, high-efficiency particulate air filters were added to the air intake. Airflow was again used to perturb the spores that had previously deposited onto the duct. Resuspension rates on both steel and plastic duct materials were between 10 ⁻³ and 10 ⁻⁵ per second, which decreased to 10 times less than initial rates within 30 min. Pulsed flow caused an initial spike in spore resuspension concentration that rapidly decreased. The resuspension rates were greater than those predicted by resuspension models for contamination in the environment, a result attributed to surface roughness differences. There was no difference between spore reaerosolization from metal and that from plastic duct surfaces over 5 hours of constant airflow. The spores that deposited onto the duct remained a persistent source of contamination over a period of several hours.

We have developed a method to remove perchlorate (14–27 μg/L) and nitrate (48 mg/L) from contaminated groundwater using a wetland bioreactor. The bioreactor has operated continuously in a remote field location for more than 2 yr with a stable ecosystem of indigenous organisms. This study assesses the bioreactor for long-term perchlorate and nitrate remediation by evaluating influent and effluent groundwater for oxidation-reduction conditions and nitrate and perchlorate concentrations. Total community DNA was extracted and purified from 10-g sediment samples retrieved from vertical coring of the bioreactor during winter. Analysis by denaturing gradient gel electrophoresis of short, 16S rDNA, polymerase-chain-reaction products was used to identify dominant microorganisms. Bacteria genera identified were closely affiliated with bacteria widely distributed in soils, mud layers, and fresh water. Of the 17 dominant bands sequenced, most were gram negative and capable of aerobic or anaerobic respiration with nitrate as the terminal electron acceptor (Pseudomonas, Acinetobacter, Halomonas, and Nitrospira). Several identified genera (Rhizobium, Acinetobactor, and Xanthomonas) are capable of fixing atmospheric nitrogen into a combined form (ammonia) usable by host plants. Isolates were identified from the Proteobacteria class, known for the ability to reduce perchlorate. Initial bacterial assessments of sediments confirm the prevalence of facultative anaerobic bacteria capable of reducing perchlorate and nitrate insitu.