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Chapter 82 : Monochloramine Disinfection of Biofilm-Associated Legionella pneumophila in a Potable Water Model System
This chapter aims at determining the susceptibility of biofilm-associated Legionella pneumophila to free chlorine and monochloramine. A biofilm reactor was developed to grow biofilms containing L. pneumophila on 24 replicate stainless-steel surfaces in potable water. The ability of this reactor to produce reproducible biofilms was validated by the fact that the standard deviations of the base biofilm densities on stainless-steel coupons (n = 3) ranged from 0.06 to 0.18 log CFU per coupon. When Legionella containing biofilms were exposed to the same dosages of monochloramine for identical contact periods, the treatments were significantly more effective. In summary, the authors have shown that biofilm-associated L. pneumophila are significantly less susceptible to chlorine than are planktonic L. pneumophila, while susceptibility of planktonic and biofilm-associated L. pneumophila to monochloramine are similar. When monochloramine and free chlorine were compared under identical conditions, monochloramine was significantly more effective, indicating that monochloramine may be an effective disinfectant for the inactivation of L. pneumophila within potable water distribution systems. Further research using open system biofilm reactors and model distribution systems is needed to determine the utility of monochloramine as a disinfectant against biofilm-associated L. pneumophila.