Decontamination of Biological Threats in Water Supplies

The outcome of the project was to provide the EPA with a technical resource document that could be used to guide emergency responders and for longer-term microbial decontamination of building water systems. This project was done in collaboration with the Building and Fire Research Laboratory (BFRL). Researchers in the BFRL also studied the detection and decontamination of dangerous chemicals in building water systems. The research was done on small bench-scale pipe systems and also on a large-scale system designed to simulate a multi-floor building water system. Model water systems were developed to establish biofilms, the naturally occurring microorganisms that form on the surfaces of water systems. Simulants for the real biological threats were developed based on the similar biological and chemical properties. The simulant used for Bacillus anthracis spores (that cause the disease anthrax) was Bacillus thuringiensis spores (a harmless material used for insect control). Strains of E. coli were used for other dangerous bacteria. Model proteins (enzymes) were also developed for the protein toxin ricin. Small-scale experiments were done with bacteria and protein toxins in the biosafety level 2 laboratories. The large-scale experiments were done with the harmless simulants developed in the project. The adhesion and disinfection of the biological threats to the model water systems was measured over a variety of conditions. Different concentrations of the commonly used disinfectants, chlorine and monochloramine, were used to study the disinfection process. A novel disinfection process was developed using conditions to stimulate the germination of Bacillus spores resulting in improved disinfection in the water systems.