The NH3-N inhibition kinetics of 3 Nitrosomonas at adhesive status

Abstract:

[Background] The activity of Nitrosomonas was significantly influenced by NH₃-N concentration, but the inhibition kinetics of NH₃-N concentration of the adhesive Nitrosomonas were still unknown. [Objective] The influence of NH₃-N concentration on 3 strains of adhesive Nitrosomonas (Nitrosomonas eutropha CZ-4, Nitrosomonas halophila C-19 and Nitrosomonas europaea SH-3). [Methods] Three strains of Nitrosomonas (N. eutropha CZ-4, N. halophila C-19 and N. europaea SH-3) were cultured under different initial NH₃-N concentrations (ranged from 25-1 000 NH₃-N mg/L) with calcium carbonate as the adsorption matrix. The accumulation rate of NO₂^--N and the specific growth rate were measured, the inhibition kinetic equations of ammonia oxidation were also established by Edwares2 model. [Results] The accumulation of NO₂^--N of N. halophila C-19 was fastest when the initial NH₃-N concentration was 50-100 mg/L, while the NO₂^--N accumulation rate was maximum when the initial NH₃-N concentration was 50-200 mg/L for N. europaea SH-3 and 50-400 mg/L for N. eutropha CZ-4, respectively. The maximum specific growth rate of N. eutropha CZ-4 occurred at the initial NH₃-N concentration of 50-400 mg/L, which was much higher than N. halophila C-19 (25-100 mg/L). There was no significant difference in growth rates for N. europaea SH-3 when the initial NH₃-N concentration ranged from 50 mg/L to 800 mg/L. The K_I of N. europaea SH-3 (922.76 mg/L) was significantly higher than N. eutropha CZ-4 (597.88 mg/L), and also the K_I of N. eutropha CZ-4 was significantly higher than N. halophila C-19 (186.24 mg/L). Moreover, the K_m (72.06 mg/L) of N. europaea SH-3 was significantly higher than N. halophila C-19 (23.23 mg/L). [Conclusion] The three strains of adhesive Nitrosomonas showed great differences both in ammonia oxidation activity and growth. The results may not only help to understand the functions of different Nitrosomonas in wastewaters with different NH₃-N concentrations, but also contribute to develop corresponding engineering technologies.