[Denitrification Process and NO Production Characteristics of Heterotrophic Nitrifying Bacterium YL].

Because of the massive discharge of nitrogenous wastewater, the eutrophication of a water body is becoming increasingly serious, and how to effectively remove nitrogen from this wastewater remains an urgent problem to be solved. In this study, due to disadvantages in the traditional biological nitrogen removal process, such as complex and long procedures, high energy consumption, weak impact resistance, and NO release, the nitrogen removal theory by heterotrophic nitrification was further analyzed by discussing the physiological-biochemical, heterotrophic nitrification-aerobic denitrification, and NO production characteristics of a high-efficiency heterotrophic nitrifying bacteria YL. Results show that the strain YL had an eminent heterotrophic nitrification and aerobic denitrification ability, and NH-N, NO-N, and NO-N with concentration of 100 mg·L could be completely removed during the 24-hour incubation period. There was almost no intermediate product in the process of heterotrophic nitrification, however when NO-N was used as nitrogen source, the accumulation of NO-N reached 25.55 mg·L. Meanwhile, the successful expression of denitrification genes , , and further confirmed the aerobic denitrification ability of strain YL. Gaseous nitrogen products accounted for about 30%-40% of removed TN in the heterotrophic nitrification-aerobic denitrification process by strain YL, and N was the main denitrification product. When NH-N, NO-N, and NO-N were used as the sole nitrogen source, N production amounted to 3.46, 3.49, and 3.36 mg, respectively. In contrast, only small amounts of NO were produced in the denitrification process by strain YL, and the total amount was 6.63 μg when NH-N was the nitrogen source, which was much lower than in the cases of NO-N and NO-N as the sole nitrogen source. In addition, high C/N, low pH, high temperature, high NH-N, and high NO-N conditions could result in more NO generation. Nevertheless, most environmental factors had little effect on NO production of strain YL, and the maximum NO production was significantly lower than that of short-cut nitrification system and autotrophic nitrification system. These results demonstrated that strain YL exhibited excellent abilities of nitrogen removal, NO emission control, and tolerance to environmental conditions, and could be an effective candidate for treating wastewater without secondary air pollution.