Decontamination of Bacillus Spores from Drinking Water Infrastructure with Physical Removal (Pigging)
Szabo, Jeff, J. Hall, AND J. Goodrich. Decontamination of Bacillus Spores from Drinking Water Infrastructure with Physical Removal (Pigging). U.S. Environmental Protection Agency, Washington, DC, EPA/600/R-18/078, 2018.
The U.S. Environmental Protection Agency’s (EPA) National Homeland Security Research Center partnered with the Idaho National Laboratory (INL) to build the Water Security Test Bed (WSTB) at the INL test site outside of Idaho Falls, Idaho. The WSTB was built using an 8-inch diameter cement-mortar lined drinking water pipe that had been previously taken out of service. The pipe was exhumed from the INL grounds and oriented in the shape of a small drinking water distribution system that is 450 feet (ft) long. The WSTB can support drinking water distribution system research on a variety of topics including biofilms, water quality, sensors, and homeland security related contaminants. Since the WSTB is constructed of real drinking water distribution system pipes, research can be conducted under conditions similar to those in a real drinking water system. Decontamination was undertaken with a technique known as pigging, or physical scouring of the inner pipe surface, followed by disinfection with free chlorine. Two pigging techniques were evaluated in separate experiments. First, ice pigging technology was used via a proprietary truck mounted mobile technology developed by the Utility Services Co., Inc. (USC). Ice pigging works by pumping a slurry of ice and water down the pipe. The ice in the slurry was expected to scour the inner pipe surface. The second pigging technique used a KEG® chain cutter. In this technique, water was pumped from a combination (Vactor®) truck at high flow and pressure and through a nozzle with a chain attached to it. The water flow caused the chains to spin and scour the pipe interior. Both pigging techniques were used to decontamination the 450 ft long pipe, as well as individual sections of cement-mortar lined iron pipe, and unlined iron pipe with corrosion. The results of this study indicate that the chain cutter followed by chlorination was more effective at reducing B. globigii spores than ice pigging followed by chlorination.
This report summarizes the results of biological decontamination experiments performed at the WSTB focused on removing Bacillus globigii spores adhered to the inner surface of the 8-inch water pipe. B. globigii spores are a non-pathogenic surrogate for B. anthracis, which is the causative agent of anthrax.