[Nitrogen Removal by Heterotrophic Nitrifying Bacterium Pseudomonas putida YH and Its Kinetic Characteristics]

Due to the low nitrogen removal efficiency, lengthy procedure, and vulnerability to high loads of ammonium of the traditional sewage treatment process, the physiological characteristics, nitrogen removal characteristics, influencing factors, and kinetic analysis were systematically studied for the heterotrophic nitrifier Pseudomonas putida YH, which has efficient nitrogen removal ability. The results showed that strain YH exhibited efficient heterotrophic nitrification ability with a low accumulation of nitrification products. The maximum ammonium removal rate was 99.1%, and nearly 53% of the removed TN was converted to intracellular nitrogen. In addition, nitrite and nitrate could also be metabolized by strain YH under aerobic conditions, with a maximum removal rate of 99.8% and 99.5%, respectively. Additionally, the successful PCR amplification of the napA and nirK genes further improved the aerobic denitrification characteristics of strain YH. The bacterial growth process of strain YH matched the Logistic model (R²>0.99), and the nitrogen degradation conformed to the Compertz model (R²>0.99). The order of the maximum conversion rates of nitrogen (R_m) was ammonia > nitrate > nitrite, and that of the lag time (t₀) was nitrate > nitrite > ammonia. The optimal conditions for heterotrophic ammonium oxidation with strain YH were succinate as the carbon source, C/N=10, T=30℃, r=160-200 r·min^-1, and pH=7.0. Under the optimal conditions, the average ammonia oxidation rate and R_m were 8.35 and 16.71 mg·(L·h)^-1, respectively. Strain YH could adapt to a broad range of ammonium loads. A high ammonium removal rate was observed under high ammonium concentrations (1000 mg·L^-1), indicating the high potential of strain YH for application in high-strength ammonium wastewater treatment.