title: The effect of sodium chloride on the two-step kinetics of the nitrifying process.
abstract: Sodium chloride affects the transformation rate of several compounds in bioreactors. Most authors report a decrease in microorganism activity at increasing salt concentrations. In this work, a kinetic model that relates sodium chloride concentration with the rates of each step of the nitrification process is proposed; thus, the effect of sodium chloride concentration (0 to 60 g/L) on the nitritation and nitratation rates was separately studied. To carry out the independent study of each step, a combination of the respirometric method with sodium azide, an inhibitor of the nitratation step, was performed. The dot-blot hybridization technique with 16S rRNA-targeted probes was used to determine the ammonia-oxidizing and nitrite-oxidizing bacterial fraction, then it was possible to relate the culture's function with its biological composition. Rates of both steps were linearly reduced at increasing salt concentrations: the nitratation rate was more affected than the nitritation rate. Simulations carried out in a nitrifying sequencing batch reactor indicate that nitrite might accumulate at high salt concentrations. Sodium chloride exerts a reversible inhibition on ammonia oxidation and nitrite oxidation.
authors.affiliation: Department of Chemical Engineering, University of Conceptión, Chile.
authors.forename: Omar
authors.initials: O
authors.lastname: Sánchez
authors.forename: Estrella
authors.initials: E
authors.lastname: Aspé
authors.forename: María C
authors.initials: MC
authors.lastname: Martí
authors.forename: Marlene
authors.initials: M
authors.lastname: Roeckel
mesh_terms: D001419:Bacteria / Q000235:genetics; D019149:Bioreactors; D007700:Kinetics; D008962:Models, Theoretical; D009584:Nitrogen / Q000032:analysis* / Q000378:metabolism*; D012336:RNA, Ribosomal, 16S / Q000032:analysis; D012965:Sodium Chloride / Q000737:chemistry*
chemical_list: D012336:RNA, Ribosomal, 16S; D012965:Sodium Chloride; D009584:Nitrogen