Containment of Bacillus Globigii spores by bioretention cells: Results of simulated runoff events

Countries worldwide have become increasingly concerned with the threat of bioterrorism. Anthrax [Bacillus anthracis (BA)] can lead to severe infections within human and animals. Research is needed to understand how to control these spores in the environment following accidental or purposeful release; stormwater may be a conveyance for such spores to green stormwater infrastructure, which might need to be decontaminated. In this study, the effectiveness of bioretention cell and high flow media filter stormwater control measures (SCMs) in Huron, Ohio, was evaluated for removal of Bacillus globigii (Bg) spores (a harmless cognate of BA). Three 4-8 mm simulated events for each SCM were created using a fire hydrant and Bg spores were injected into the runoff. Flumes, weirs, bubblers, and automated samplers were utilized to measure the runoff hydrograph and take flow proportional water quality samples at the inlet and outlet of each SCM. The traditional BRC consistently outperformed the high flow media filter in reducing the Bg concentrations and loads with an average log reduction of 1.9 (~99% reduction) compared to 0.4 (~60% reduction), respectively. It was determined that the infiltration rate of the media and subsequent retention time within the filters was the probable critical design factor, with slower hydraulic conductivity resulting in better Bg spore containment. After 3 months, soil samples yielded detectable Bg spores within the top 15cm of media, with an increase of spore concentrations where ponding occurred for longer durations during the tests.