| The mixed ammonia oxidizer culture was obtained using common activated sludge enriched for 120 days and the concentration of the ammonia oxidizers increased 300 times. The biomass yield coefficient fS were measured by batch respirometry, the value of fS,ns and fS,nb is 0.2262 and 0.2314 mg Xns COD produced/mg NH4+-NOD oxidized. Biomass concentrations were measured as chemical oxygen demand (COD) using commercially available reagents. NO2--N oxidation was completely inhibited by addition of 24μM NaN3, in order to describe the kinetics of NH4+-N to NO2--N oxidation correctly; NO2--N oxidation was completely inhibited by addition of 10mg·L-1ATU, for describing the kinetics of NO2--N to NO3--N oxidation correctly; the kinetics of NH4+-N to NO3--N oxidation was described without any inhibitor.The ammonia oxidation test was made under the mixed atmosphere of NO2/O2/CO2, The ammonia oxidation rate under anaerobic and aerobic condition were simulated respectively, in order to build kinetics equation of ammonia oxidation under multicondition, and the results were showed as follows.(1) Ammonia oxidizer could use NO2 as electron acceptor to oxidize ammonia and produce NO when there was no molecule oxygen. The maximum anaerobic ammonia oxidation rate, 0.063 mgNOD·mgCOD-1·h-1 occurred when the concentration of NO2 was 25ppm. The multielement kinetics model was built integrated the Monod function, There was the inhibition kinetics parameter of anaerobic ammonia oxidation based on NO2: the half saturate coefficient of NO2 concentration were 0.6973 umol·L-1, inhibition coefficient of NO2 concentration were 1.8561 umol·L-1, the maximum ammonia oxidation rate were 0.1343 mgNOD·mgCOD-1·h-1.(2) After adding 2%O2 to NO2, the ammonia oxidation rate increased obviously than in the anaerobic condition. The maximum ammonia oxidation rate, 0.1982 mgNOD·mgCOD-1·h-1 occurred when the concentration of NO2 in the mixed gas was 50ppm. The ammonia oxidation rate is increased obviously with the increasing of O2 when the concentration of NO2 is changeless. The change of the ammonia oxidation rate under the condition of NO2/2%O2 showed the results: under the condition of NO2/2%O2, Part of NO2 participated in anaerobic ammonia oxidation and part of the other participated in aerobic ammonia oxidation, then anaerobic ammonia oxidation and aerobic ammonia oxidation based on NO2 happened cooperant coupling.
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