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Numerous topics surrounding Legionella bacteria and Legionnaires’ disease have come up on this site. As an effort to take a step back and examine some of the basics, this post seeks to examine various forms of control and prevention for Legionella bacteria.

One effective chemical treatment is chlorine. This is particularly effective for systems with basic marginal issues however for systems with more significant problems, a ‘shock’ chlorination, i.e. when chlorine levels are raised to more than 2 ppm over 24 hours and then brought back down to 0.5 ppm can sometimes prove effective. Hyperchlorination is a somewhat similar process however it involves the water system being taken out of service so that the chlorine residual can be raised to at least 50 ppm for at least 24 hours. After the 24 hours, the water system is then flushed and brought back down to 0.5 ppm chlorine.

Another common method involves copper-silver ionization. This process is recognized by the U.S. Environmental Protection Agency and the World Health Organization for Legionella control. In order to be effective, the copper and silver ion concentrations must be kept at the correct levels depending upon the water flow and overall water usage. The overall disinfection function within a facility’s water distribution system usually occurs at around 30 to 45 days. Copper-silver ionization is not meant for cooling towers because with pH levels of 8.6 or higher, the ionic copper can begin to precipitate.

Chlorine dioxide is another treatment method and has been approved by the U.S. Environmental Protection Agency since 1945. Chlorine dioxide does not create carcinogenic byproducts like chlorine does when it is used to purify drinking water with natural organic compounds like humic and fulvic acids. Chlorine dioxide is not a considered a restricted heavy metal like copper and has proven to have excellent control of Legionella in both cold and hot water systems, all while its proficiency as a biocide is not diminished by pH.

Finally there is moist heat sterilization, where water systems are heated up to 140 °F (60 °C) and then flushed. This method is seen as a traditional nonchemical treatment that should in most cases be repeated every 3–5 weeks in order to ensure effectiveness.

This list does not represent an exhaustive list of various control and prevention methods for Legionella bacteria nor advice on how individuals should maintain their water systems since such matters would presumably depend upon individuals circumstances. That said, this post does attempt to serve as a brief introduction on the topic, a topic which one may be encouraged to learn more about if interested or potentially relevant.

Jules Zacher is an attorney in Philadelphia who has tried Legionnaires’ disease cases across the U.S.  Please visit LegionnaireLawyer.com again for updates.

Posted by jzacher">jzacher at 10:05 am

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