Heterotrophic Nitrification-Aerobic Denitrification Performance of Strain Y-12 under Low Temperature and High Concentration of Inorganic Nitrogen Conditions

An aerobic nitrite-denitrifying bacterium Pseudomonas putida Y-12 was used to remove sole and mixed nitrogen sources at 15 °C. When strain Y-12 was incubated for 4 days with a sole nitrogen source and initial NH4+-N, NO3−-N, and NO2−-N concentrations of 208.1, 204.7, and 199.0 mg/L, respectively, the removal ratios of NH4+-N, NO3−-N, and NO2−-N were 98.8, 73.6, and 77.1%, respectively. The average removal rates of NH4+-N, NO3−-N, and NO2−-N reached 2.14, 1.57, and 1.60 mg/L/h, respectively. Intermediate products (NO3−-N and NO2−-N) were detected at a low level. Total nitrogen removal was mainly achieved during the stationary phase in the denitrification process. All the results indicated that strain Y-12 could perform heterotrophic nitrification and aerobic denitrification at 15 °C, which was beneficial for future applications in wastewater treatment at low temperatures.