title: Monochloramine Cometabolism by Mixed-Culture Nitrifiers under Drinking Water Conditions.
abstract: Chloramines are the second most used secondary disinfectant by United States water utilities. However, chloramination may promote nitrifying bacteria. Recently, monochloramine cometabolism by the pure culture ammonia-oxidizing bacteria, Nitrosomonas europaea, was shown to increase monochloramine demand. The current research investigated monochloramine cometabolism by nitrifying mixed cultures grown under more relevant drinking water conditions and harvested from sand-packed reactors before conducting suspended growth batch kinetic experiments. Four types of batch kinetic experiments were conducted: (1) positive controls to estimate ammonia kinetic parameters, (2) negative controls to account for biomass reactivity, (3) utilization associated product (UAP) controls to account for UAP reactivity, and (4) cometabolism experiments to estimate cometabolism kinetic parameters. Kinetic parameters were estimated in AQUASIM with a simultaneous fit to the experimental data. Cometabolism kinetics were best described by a first-order model. Monochloramine cometabolism kinetics were similar to those of ammonia metabolism, and monochloramine cometabolism accounted for 30% of the observed monochloramine loss. These results demonstrated that monochloramine cometabolism occurred in mixed cultures similar to those found in drinking water distribution systems; therefore, monochloramine cometabolism may be a significant contribution to monochloramine loss during nitrification episodes in drinking water distribution systems.
authors.affiliation: University of Texas at Austin , Department of Civil, Architectural and Environmental Engineering, 301 East Dean Keeton Street, Stop C2100, Austin, Texas 78712, United States.
authors.forename: Juan P
authors.initials: JP
authors.lastname: Maestre
authors.affiliation: United States Environmental Protection Agency , Office of Research and Development, Cincinnati, Ohio 45268, United States.
authors.forename: David G
authors.initials: DG
authors.lastname: Wahman
authors.affiliation: University of Texas at Austin , Department of Civil, Architectural and Environmental Engineering, 301 East Dean Keeton Street, Stop C2100, Austin, Texas 78712, United States.
authors.forename: Gerald E
authors.initials: GE
authors.lastname: Speitel
mesh_terms: D000641:Ammonia / Q000378:metabolism; D004202:Disinfectants / Q000378:metabolism; D060766:Drinking Water; D007700:Kinetics; D043370:Nitrosomonas europaea / Q000378:metabolism*
chemical_list: D004202:Disinfectants; D060766:Drinking Water; D000641:Ammonia