| Nitrogen(N) is one of the main causes of water pollution in China. Technology of Nitrogen removal, especially the biological nitrogen removal due to its economic, efficient and harmless, caused widespread concern all over the world. Microbial is the core of biological wastewater nitrogen removal technology, but the nitrogen removal efficiency is easily affected by the water quality conditions such as salinity stress factors.In this study, a strain named HN-02 of heterotrophic nitrification-aerobic denitrification bacteria(Aeromonas hydrophila sp.) was the object, which was from the laboratory screening of freshwater. Studied the impact of the different salinity(NaCl concentration of 0~20g/L) nitrogen removal performance and antioxidant enzyme system response characteristics of strain HN-02 under salt stress. And then, HN-02 was domesticated through different salinity. In addition, comparative study of nitrogen removal characteristics and antioxidant response characteristic of domestication was started. Studies showed that:(1) HN-02 is a strain of Facultative halophiles. It could toleranced the salinity shock between NaCl concentration of 0~20 g/L. The growth of strains and the nitrogen removal rate and salt concentration had a negative correlation, 6 h, 0 g/L, 5 g/L, salinity, 10 g/L, 15 g/L and 20 g/L of ammonia nitrogen degradation rate were 3.66 mg/L·h, 2.95 mg/L·h, 2.82 mg/L·h.1.92 mg/L·h and 1.08 mg/L·h.(2) HN-02 in the event of emergency response to salt stress, antioxidant enzyme in the body was a system, such as SOD and POD are synergistic effect. The sensitivity of antioxidant enzyme under salinity stress: SOD>POD, but the variation of enzyme activity: CAT>SOD>POD, the activity of CAT were compared with SOD, POD amplitude increased by 32.06 U/g and 117.24 U/g.(3) Acclimation improved the salt tolerance of HN-02 on nitrogen removal performance. The growth and nitrogen removal rate of domestication of HN-02 was inversely correlated with salinity concentration. In 6 h, OD600 and growth rate of salinity of 5 g/L, 10 g/L, 15 g/L and 20 g/L were 0.647(0.097 h-1), 0.590(0.087 h-1), 0.522(0.076 h-1) and 0.233(0.028 h-1), respectively. The growth rate increased 0.647(0.097 h-1), 0.590(0.087 h-1), 0.522(0.076 h-1) and 0.233(0.028 h-1), which compared with before acclimation; the nitrogen removal rate respectively were 5.17 mg/L·h, 5.21 mg/L·h, 3.87 mg/L·h and 2.14 mg/L·h, respectively, which increased 2.22 mg/L·h(75.14%), 2.39 mg/L·h(85.04%), 1.95 mg/L·h(101.25%) and 1.06 mg/L·h(98.10%)compared with before acclimation.(4) SOD of HN-02 in salt tolerance played a key role. Acclimated by salt, HN-02 could induce SOD to defense quickly. SOD in the whole stress period will play a role, and the stress was more sensitive in the early stage.(5) Acclimated, the activity of POD was inhibited under salt stress was greater than SOD, the ability to generate induced by POD may be less than SOD. At the same time, the antioxidant enzyme system to play the role of the order maybe was: SOD>POD>CAT, but when POD is not enough to clear the harm of H2O2, CAT and POD at the same time synergy regulation of the adverse effects of the body to relieve stress.(6) NaCl concentration 15 g/L may be terminated or alleviate the critical salinity of HN-02. Within the salinity of 15 g/L, the activity of SOD increased with the salinity increased, the maximum average increase rate(salinity 15 g/L) was 30.05 U/g·h. When the salinity was higher than 15 g/L, POD and CAT activity was inhibited.(7) When HN-02-05, HN-02-10, HN-02-15 and HN-02-20 were by shocked salinity of 20 g/L, ammonia degradation ability and growth was not a linear relationship. The average growth rate was 0.027 h-1, 0.033 h-1, 0.058 h-1 and 0.013 h-1, respective, in which HN-02-15 had the strongest salt tolerance and the fastest growth rate. On the nitrogen removal ability, more close to the impact of salinity acclimation salinity(20 g/L) nitrogen removal effect was better, the ammonia nitrogen degradation rate were 1.71 mg/L·h, 5.92 mg/L·h and 6.99 1.91mg/L·h, mg/L·h, respective, and HN-02-20 has the best effect.At present, the heterotrophic nitrification-aerobic denitrification bacteria used in high salt wastewater nitrogen removal is still in the research stage. It was the lack of the mechanism of salt tolerance study. Studied on characteristics of microbial nitrogen removal characteristics in response to salinity stress and antioxidant enzyme system could improve the wastewater biological nitrogen removal under salt stress, and provide reference for the strategy and technology research. |
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