Persistence of Non-pathogenic Bacillus Spores on Sewer Infrastructure Surfaces and Assessment of Decontamination Using Chlorine
Citation:
Szabo, Jeff. Persistence of Non-pathogenic Bacillus Spores on Sewer Infrastructure Surfaces and Assessment of Decontamination Using Chlorine. U.S. Environmental Protection Agency, Washington, DC, EPA/600/R-17/284, 2017.
Impact/Purpose:
The potential for biological contamination of sewer system infrastructure is one area of concern. In the event of a drinking water distribution system contamination incident involving a biological agent, contamination of the sewer system infrastructure could result from flushing of the drinking water distribution system to remove the contaminant. In addition, in the event of a biological contamination incident over a wide outdoor area or a building exterior, contamination of the sewer system could result from wash down activities or rain releasing biological agents into a sewer system. An open question is whether biological agents like pathogenic Bacillus spores, which are hardy and resistant to inactivation in the environment, will persist on wastewater infrastructure and if they can be removed via flushing or disinfection. This study examined the persistence of Bacillus atrophaeus subsp. globigii (B. globigii) spores (a surrogate for pathogenic B. anthracis spores) on the surface materials that make up common sewer systems. The secondary objective of this study was to determine the effect of adding chlorine bleach on the persistence of B. globigii adhered to various sewer infrastructure materials. Results show that should Bacillus spore contamination flow into a sewer during a real contamination event, most of the spores will flow with the water. Spores that do adhere to infrastructure do so in a largely transient manner, and most are washed off of the infrastructure material in the days after the contamination event. There could be spores adhered to the infrastructure for at least 42 days on clay, PVC, rubber and especially on iron, where the spores were most persistent. It is possible that spores might persist longer, but times frames beyond 42 days were not addressed in this project. Adding chlorine to a wastewater system to decontaminate spores is largely ineffective.
Description:
Report