The potential to manage releases of Bacillus anthracis using bioretention and a high flow media filter: Results of simulated runoff testing with tracer spores Bacillus globigii.

The threat of bioterrorism has spurred research on the decontamination and containment of different agents. Anthrax [causative agent Bacillus anthracis (Ba)] is a disease that can lead to severe infections within human and animals, particularly when inhaled. This research investigated the use of spore-contaminated simulated runoff events into stormwater control measures (SCMs), which are designed to retain and improve the quality of runoff and may have the potential to filter and contain the spores. In this study, the effectiveness of a bioretention cell (BRC) and high flow media filter (HFMF) in Huron, Ohio, were evaluated for removal of Bacillus globigii (Bg) spores (a harmless cognate of Ba). Three 4-8 mm simulated runoff events were created for each SCM using a fire hydrant and Bg spores were injected into the runoff upstream of the SCM inlets. The BRC significantly (p < 0.001) outperformed the HFMF in reducing Bg concentrations and loads, with an average load reduction of 1.9 log (∼99% reduction) compared to 0.4 (∼60% reduction), respectively. A probable critical design factor leading to these differences was the infiltration rate of the media and subsequent retention time within the filters, which was supported by similar disparities in suspended solids reductions. Differences in spore removal may also have been due to particle size distribution of the HFMF, which was more gravelly than the bioretention cell. At 3 and 6 months after the-simulated runoff tests, soil samples taken from both SCMs, yielding detectable Bg spores within the top 15 cm of media, with increased spore concentrations where ponding occurred for longer durations during the tests. This suggests that forebays and areas near inlets may be hotspots for spore cleanup in a real-world bioterrorism incident.

Evaluation of steam heat as a decontamination approach for SARS-CoV-2 when applied to common transit-related materials.

AIMS: The purpose of this study was to evaluate the efficacy of steam heat for inactivation of SARS-CoV-2 when applied to materials common in mass transit installations. METHODS AND RESULTS: SARS CoV-2 (USA-WA1/2020) was resuspended in either cell culture media or synthetic saliva, inoculated (∼1 × 106 TCID50) onto porous and nonporous materials and subjected to steam inactivation efficacy tests as either wet or dried droplets. The inoculated test materials were exposed to steam heat ranging from 70°C to 90°C. The amount of infectious SARS-CoV-2 remaining after various exposure durations ranging from 1 to 60 s was assessed. Higher steam heat application resulted in higher inactivation rates at short contact times. Steam applied at 1-inch distance (∼90°C at the surface) resulted in complete inactivation for dry inoculum within 2 s of exposure (excluding two outliers of 19 test samples at the 5-s duration) and within 2-30 s of exposure for wet droplets. Increasing the distance to 2 inches (∼70°C) also increased the exposure time required to achieve complete inactivation to 15 or 30 s for materials inoculated with saliva or cell culture media, respectively. CONCLUSIONS: Steam heat can provide high levels of decontamination (>3 log reduction) for transit-related materials contaminated with SARS-CoV-2 using a commercially available steam generator with a manageable exposure time of 2-5 s.

Impact of filter material and holding time on spore sampling efficiency in water.

Bacillus anthracis and other environmentally persistent pathogens pose a significant threat to human and environmental health. If contamination is spread over a wide area (e.g. resulting from a bioterrorism or biowarfare incident), readily deployable and scalable sample collection methods will be necessary for rapidly developing and implementing effective remediation strategies. A recent surge in environmental (eDNA) sampling technologies could prove useful for quantifying the extent and levels of contamination from biological agents in environmental and drinking water. In this study, three commonly used membrane filtration materials (cellulose acetate, cellulose nitrate, and nylon) were evaluated for spore filtration efficiency, yielding recoveries from 17%-68% to 25%-117% for high and low titer samples, respectively, where cellulose nitrate filters generated the highest recoveries. A holding time test revealed no statistically significant differences between spore recoveries when analyzed at the specified timepoints, suggesting that eDNA filter sampling techniques can yield and maintain a relatively high recovery of spores for an extended period of time between filtration and analysis without a detrimental impact on spore recoveries. The results shown here indicate that emerging eDNA technologies could be leveraged for sampling following a wide-area contamination incident and for other microbiological water sampling applications.

Large-scale evaluation of microorganism inactivation by bipolar ionization and photocatalytic devices.

The COVID-19 pandemic has raised awareness in the spread of disease via airborne transmission. As a result, there has been increasing interest in technologies that claim to reduce concentrations of airborne pathogens in indoor environments. The efficacy of many of these emerging technologies is not fully understood, and the testing that has been done is often conducted at a small scale and not representative of applied settings. There is currently no standard test method for evaluating air treatment technologies, making it difficult to compare results across studies or technology types. Here, a consistent testing approach in an operational-scale test chamber with a mock recirculating heating, ventilation, and air conditioning (HVAC) system was used to evaluate the efficacy of bipolar ionization and photocatalytic devices against the non-enveloped bacteriophage MS2 in the air and on surfaces. Statistically significant differences between replicate sets of technology tests and control tests (without technologies active) are apparent after 1 h, ranging to a maximum of 0.88 log10 reduction for the bipolar ionization tests and 1.8 log10 reduction for the photocatalytic device tests. It should be noted that ozone concentrations were elevated above background concentrations in the test chamber during the photocatalytic device testing. No significant differences were observed between control and technology tests in terms of the amount of MS2 deposited or inactivated on surfaces during testing. A standardized, large-scale testing approach, with replicate testing and time-matched control conditions, is necessary for contextualizing laboratory efficacy results, translating them to real-world conditions, and for facilitating technology comparisons.

Impact of test methodology on the efficacy of triethylene glycol (Grignard Pure) against bacteriophage MS2.

The COVID-19 pandemic has raised interest in using chemical air treatments as part of a strategy to reduce the risk of disease transmission, but more information is needed to characterize their efficacy at scales translatable to applied settings and to develop standardized test methods for characterizing the performance of these products. Grignard Pure, a triethylene glycol (TEG) active ingredient air treatment, was evaluated using two different test protocols in a large bioaerosol test chamber and observed to inactivate bacteriophage MS2 in air (up to 99.9% at 90 min) and on surfaces (up to 99% at 90 min) at a concentration of approximately 1.2 - 1.5 mg/m3. Introducing bioaerosol into a TEG-charged chamber led to overall greater reductions compared to when TEG was introduced into a bioaerosol-charged chamber, although the differences in efficacy against airborne MS2 were only significant in the first 15 min. Time-matched control conditions (no TEG present) and replicate tests for each condition were essential for characterizing treatment efficacy. These findings suggest that chemical air treatments could be effective in reducing the air and surface concentrations of infectious pathogens in occupied spaces, although standard methods are needed for evaluating their efficacy and comparing results across studies. The potential health impacts of chronic exposure to chemicals should also be considered, but those were not evaluated here.

Influence of wash aids on Bacillus spore removal from an asphalt parking lot using two spray-based washing methods.

AIMS: The goal of this study was to measure the removal efficacy of Bacillus atrophaeus spores from a parking lot using spray-based washing methods (a pressure washer and a garden hose) and wash aids. B. atrophaeus is a commonly used nonpathogenic surrogate for B. anthracis, the causative agent of anthrax and a deadly bioterrorism agent that would cause major disruptions and damage to public health should it be disseminated over an urban area. METHODS AND RESULTS: Five wash aids (1 mM sodium chloride, an Instant Ocean® seawater solution, 0.01% Tween 20, 0.01% sodium dodecyl sulfate, and unamended tap water) were used along with two different spray sequences in this study. Across all treatment conditions, 3.7-6.4 log10  colony forming unit were recovered in the runoff water, and 0.15%-23% of spores were removed from the surface of the parking lot. CONCLUSIONS: Pressure washing removed more spores than the garden hose, and for both types of washing methods, the first pass removed more spores than the subsequent passes. The Instant Ocean and Tween 20 wash aids were found to significantly increase the percentage of spore removal when using the pressure washer, but the overall increase was only 1%-2% compared to the tap water alone. SIGNIFICANCE AND IMPACT OF STUDY: This study provides public officials and emergency responders with baseline spore physical removal information for situations where a corrosive disinfectant might have a negative impact on the environment and washing is being considered as an alternative remediation approach.

Modeling radionuclide transport in urban overland flow: a case study.

This paper presents a case study demonstrating the process used to develop an overland flow model of radionuclide transport following an aerosol deposition from a hypothetical radiological dispersal device explosion. The process included the integration of digital elevation, building, and land cover information with hydrologic information from a calibrated Stormwater Management Model (SWMM) model. The overland flow model was used to explore the impact of washoff parameter selection and different storm events on radionuclide transport in surface flow. The range of washoff parameters used in the literature resulted in over a 7 times difference in radionuclide washoff, from a small surface removal to nearly full removal. The overland flow model illuminated the primary pathways of contaminant transport, a potentially useful tool that informs emergency response, planning, and remediation activities.

Rainfall Washoff of Spores From Concrete and Asphalt Surfaces.

After a biological terrorist attack, understanding the migration of agents such as Bacillus anthracis is critical due to their deadly nature. This is important in urban settings with higher likelihood of human exposure and a large fraction of impervious materials contributing to pollutant washoff. The study goals were to understand the removal of spores from urban surfaces under different rainfall conditions, to compare washoff of two B. anthracis surrogate spores, and to compare two empirical fits for the first flush of spores from small areas. Concrete and asphalt were inoculated with either Bacillus atrophaeus or Bacillus thuringiensis kurstaki spores and exposed to simulated rainfall. The study assessed goodness-of-fit for the Storm Water Management Model (SWMM)'s exponential washoff function compared to an alternative two-stage exponential function. The highest average washoff of spores was 15% for an hour-long experiment. Spore washoff was not significantly different for the two spore types, but there were significant differences in washoff from asphalt versus concrete with more occurring from asphalt. Average kinetic energy of the storm event impacted washoff from asphalt, but not concrete. The two-stage function had a better goodness-of-fit than the SWMM exponential function. As such, emergency responders should be aware that the spread of contamination is impacted by the droplet characteristics of the storm event and the surface material type in the contaminated area; modelers should be aware that different data-fitting approaches may be more appropriate for first-flush calculations of small washoff areas than those used for continuous long-term simulation of large subcatchments.

Laboratory results and mathematical modeling of spore surface interactions in stormwater runoff.

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 in the laboratory for Bacillus globigii and Bacillus thuringiensis kurstaki, two common surrogates used to represent Bacillus anthracis, in synthetic baseline ultrapure water and laboratory prepared 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. globigii 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 modeling results use the laboratory data to demonstrate that the energy barriers between the spores and the urban materials were tunable through compression of the electrical 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. globigii 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. globigii spores interacting with a concrete surface in runoff water, suggesting that this would be the most challenging combination to detach through water-based decontamination.

Comparison of surface sampling methods for an extended duration outdoor biological contamination study.

Bacillus anthracis, the causative agent for anthrax, is a dangerous pathogen to humans and has a history as a bioterrorism agent. While sampling methods have been developed and evaluated for characterizing and clearing contaminated indoor sites, the performance of these sampling methods is unknown for use in outdoor environments. This paper presents surface sampling data for Bacillus atrophaeus spores, a surrogate for B. anthracis, from a 210-day outdoor study that evaluated the detection and recovery of spores using five different sampling methods as follows: sponge sticks, 37-mm vacuum filter cassettes, residential wet vacuums, robotic floor cleaners, and grab samples of soil, leaves, and grass. The spores were applied by spraying a liquid suspension onto the surfaces. Both asphalt and concrete surfaces were sampled by all the surface sampling methods, excluding grab sampling. Stainless steel coupons placed outdoors were additionally sampled using sponge sticks. Sampling methods differed in their ability to collect detectable spores over the duration of the study. The 37-mm vacuums and sponge sticks consistently detected spores on asphalt through day 37 and robots through day 99. The wet vacuums detected spores on asphalt for days 1 and 4, but not again until day 210. On concrete, all samplers detected spores until day 210 except for sponge stick samplers that detected spores only up until the day 99 time point. For all sampling methods, spore recoveries were higher from concrete than from asphalt surfaces. There was no statistically significant difference in recoveries of sponge sticks and 37-mm vacuums from either asphalt or concrete surfaces. Processing of grab samples was challenging due to non-target background microorganisms resulting in high detection limits for the samples.

Blind testing of shoreline evolution models.

Beaches around the world continuously adjust to daily and seasonal changes in wave and tide conditions, which are themselves changing over longer time-scales. Different approaches to predict multi-year shoreline evolution have been implemented; however, robust and reliable predictions of shoreline evolution are still problematic even in short-term scenarios (shorter than decadal). Here we show results of a modelling competition, where 19 numerical models (a mix of established shoreline models and machine learning techniques) were tested using data collected for Tairua beach, New Zealand with 18 years of daily averaged alongshore shoreline position and beach rotation (orientation) data obtained from a camera system. In general, traditional shoreline models and machine learning techniques were able to reproduce shoreline changes during the calibration period (1999-2014) for normal conditions but some of the model struggled to predict extreme and fast oscillations. During the forecast period (unseen data, 2014-2017), both approaches showed a decrease in models' capability to predict the shoreline position. This was more evident for some of the machine learning algorithms. A model ensemble performed better than individual models and enables assessment of uncertainties in model architecture. Research-coordinated approaches (e.g., modelling competitions) can fuel advances in predictive capabilities and provide a forum for the discussion about the advantages/disadvantages of available models.

Characterizing cesium sorption in freshwater settings using fluvial sediments and characteristic water chemistries.

Cesium-137 (137Cs) is a persistent contaminant that poses a significant risk to human health and the environment. Understanding the fate and transport of 137Cs following a contamination incident is necessary for effective containment and remediation. In this study, we performed experiments to investigate how Cs+ sorption processes are affected by sediment type and varying water chemistries to better understand how Cs+ is transported in freshwater settings. Sediment was collected from various river deposits along the Susquehanna River adjacent to the Safety Light Corporation United States Environmental Protection Agency (US EPA) Superfund site (Bloomsburg, PA) and characterized prior to being used in batch reactor experiments with waters characteristic of different regions in the US (Central US and Northeast US) and with three different cation types (Mg2+, Na+, and K+) over a range of ionic strengths. Greater amounts of Cs+ sorption occurred with increasing sediment mud (silt and clay) content, although no major differences in sorption between the Central and Northeast US water types were observed. At an ionic strength (I) of 10 mM, K+ inhibited Cs+ sorption most effectively, followed by Mg2+, with Na+ having little effect on Cs+ sorption over the range of ionic strengths tested (I = 0.1, 1, and 10 mM). Our findings indicate that for the representative freshwater conditions tested here, sediment type (e.g., clay fraction) has a greater influence on Cs+ sorption processes than water chemistry. Additional reactions or processes occurring in relatively fresh water could buffer cation competition for sorption sites. Conducting experiments using site-specific sediment samples and water chemistries is useful for predicting Cs+ sorption and mobility in distinct environmental settings, particularly when the level of Cs+ contamination is high and if the waste or contaminated (or receiving) waters have a relatively high ionic strength.

PySWMM: The Python Interface to Stormwater Management Model (SWMM).

Stormwater management seeks to reduce runoff from rain or melted snow and improve water quality. Where it can absorb into soil, runoff is filtered and returns to streams, rivers, and aquifers, but in developed areas, precipitation often cannot soak into the ground because impervious surfaces (e.g., pavement, buildings), and already saturated soils can create excess runoff. This water, which can contain pollutants, then runs across urban surfaces and into storm drains, drainage ditches, and sewer systems. Stormwater runoff can cause flooding, erosion, infrastructure and habitat damage, and contamination (including combined and sanitary sewer overflows). In urban and developed areas, effective stormwater management that routes and detains stormwater helps to mitigate these impacts and improve water quality.

Spatial response of coastal marshes to increased atmospheric CO2.

The elevation and extent of coastal marshes are dictated by the interplay between the rate of relative sea-level rise (RRSLR), surface accretion by inorganic sediment deposition, and organic soil production by plants. These accretion processes respond to changes in local and global forcings, such as sediment delivery to the coast, nutrient concentrations, and atmospheric CO2, but their relative importance for marsh resilience to increasing RRSLR remains unclear. In particular, marshes up-take atmospheric CO2 at high rates, thereby playing a major role in the global carbon cycle, but the morphologic expression of increasing atmospheric CO2 concentration, an imminent aspect of climate change, has not yet been isolated and quantified. Using the available observational literature and a spatially explicit ecomorphodynamic model, we explore marsh responses to increased atmospheric CO2, relative to changes in inorganic sediment availability and elevated nitrogen levels. We find that marsh vegetation response to foreseen elevated atmospheric CO2 is similar in magnitude to the response induced by a varying inorganic sediment concentration, and that it increases the threshold RRSLR initiating marsh submergence by up to 60% in the range of forcings explored. Furthermore, we find that marsh responses are inherently spatially dependent, and cannot be adequately captured through 0-dimensional representations of marsh dynamics. Our results imply that coastal marshes, and the major carbon sink they represent, are significantly more resilient to foreseen climatic changes than previously thought.