Research Shows Anthrax May Survive Standard Disinfection Processes

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Public Health and Drinking Water News Briefs

February 27, 2006

Anthrax spores may survive traditional drinking water disinfection methods and attach themselves to the inside surface of water system piping, according to a research report released this month at the 2006 American Society for Microbiology Biodefense Research Meeting. The study conducted by the Air Force Research Laboratory (AFRL) at Aberdeen Proving Ground in Maryland was designed to determine how anthrax spores function in drinking water systems that use chlorine as a disinfectant.

According to the researchers, results suggest that existing water treatment methods might not be effective in the event of an anthrax spore release in the water supply, and that water treatment facilities should be prepared to employ alternate disinfection methods. These treatment methods include exposure to higher concentrations of chlorine (or an alternate disinfectant) for an extended period of time.

For the study, AFRL researchers tested anthrax spore survival in water with a concentration of 1 milligram of chlorine per liter. Findings demonstrated that after one hour of exposure, there was no significant decrease in the number of viable spores. However, higher concentrations of chlorine were far more effective. At 5mg chlorine/L water, 97 percent of spores were killed after one hour. At 10mg chlorine/L 99.99 percent were killed.

Tests were also conducted to determine the ability of anthrax spores to attach to the inside of pipes by running contaminated water in a continuous loop through sections of pipe made of either copper, chlorinated poly vinyl chloride (CPVC) or galvanized iron. After 6 hours of testing, 20 to 40 percent of spores had attached themselves to the surface of the copper and CPVC pipes, 95 percent attached to the iron pipes.

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