Substrates removal and growth kinetic characteristics of a heterotrophic nitrifying-aerobic denitrifying bacterium, Acinetobacter harbinensis HITLi7^T at 2 °C

In order to investigate the heterotrophic nitrification and aerobic denitrification ability of Acinetobacter harbinensis HITLi7^T at 2 °C, both the growth parameters and substrates utilization characteristics were tested and appropriated kinetic models were obtained in this study. Under the initial concentration of 5 mg/L, the maximum NH₄⁺-N and NO₃⁻-N degradation rates were 0.076 mg NH₄⁺-N/L/h and 0.029 mg NO₃⁻-N/L/h, respectively. At the simultaneous presence of 2.5 mg/L NH₄⁺-N and NO₃⁻-N, the maximum nitrate removal rate increased to 0.054 mg NO₃⁻-N/L/h (1.86 folds), while a slight decrease was observed in NH₄⁺-N removal. Two double-substrate models, Contois-Contois (1) for NH₄⁺-N and TOC, Monod-Contois (2) for NO₃⁻-N and TOC matched well with the experimental data. The kinetic parameters were determined as μ_max1 = 0.095 h⁻¹, B_A1 = 0.012 mg/L, B_T1 = 0.784 g TOC/g biomass (R₁² = 0.9997), and μ_max2 = 0.032 h⁻¹, K_N2 = 0.375 mg/L, B_T2 = 1.108 g TOC/g biomass (R₂² = 0.9731) by multiple regression equation.