title: Nitrite oxidation inhibition by hydroxylamine: experimental and model evaluation.
abstract: A proposed approach for biological nitrogen removal significantly reduces cost by reducing biomass production and carbon requirements via inhibition of nitrite oxidation (NO2- to NO3-). Batch experiments were conducted to examine the effect of hydroxylamine (HM) on nitrite oxidizers, ammonia oxidizers, and nitrite reducers. Hydroxylamine effect experiments were done at initial pH values of 7.4-8.4, nitrogen concentrations of 100 mg N/L, biomass concentrations of 100-400 mg VSS/L and HM dosages up to 43 mg/L. Nitrite oxidizer activity was completely inhibited by HM at dosages of 7.0 and 8.9 mg/L for pH values of 8.4 and 7.6, respectively. Relatively low HM concentrations (0.35-5.5 mg/L) can be used to completely inhibit nitrite oxidation, but do not significantly affect ammonia oxidizers and nitrite reducers. A model developed to describe the effect of pH on nitrite oxidation rate fits the data well (R2 = 0.89) with values for Vmax of 0.372 (mg N/mg VSS-hr), pH* of 7.72, and the inhibition constant Kh of 0.154. Incorporation of HM inhibition into the model provided a good fit to relative nitrite oxidation rate as a function of undissociated HM concentration (R2 = 0.80, Vmax = 0.028 mg N/mg VSS-hr, pH = 7.89, Kh = 0.302, a = 0.195, and Ki= 0.277 mg/L).
authors.affiliation: Department of Environmental Science, Faculty of Science, Silpakorn University, Nakhon-pathom Province, Thailand 73000. pongsak@su.ac.th
authors.forename: P Lek
authors.initials: PL
authors.lastname: Noophan
authors.forename: L A
authors.initials: LA
authors.lastname: Figueroa
authors.forename: J
authors.initials: J
authors.lastname: Munakata-Marr
mesh_terms: D018533:Biomass; D005069:Evaluation Studies as Topic; D006863:Hydrogen-Ion Concentration; D019811:Hydroxylamine / Q000494:pharmacology*; D008956:Models, Chemical; D009566:Nitrates / Q000737:chemistry / Q000378:metabolism; D009573:Nitrites / Q000737:chemistry* / Q000378:metabolism; D010084:Oxidation-Reduction; D000644:Quaternary Ammonium Compounds / Q000737:chemistry / Q000378:metabolism; D013997:Time Factors; D014865:Waste Disposal, Fluid / Q000379:methods*
chemical_list: D009566:Nitrates; D009573:Nitrites; D000644:Quaternary Ammonium Compounds; D019811:Hydroxylamine