| Water is an important natural resource for human survival.With the rapid development of human society,more and more artificial nitrogen enters the natural water body through various ways,which leads to a series of environmental problems.Biological denitrification technology is a hot research topic in the field of environmental protection nowadays.Many new ideas of microbial denitrification have been put forward based on the traditional denitrification technology to optimize the current process.The researchers found that some microorganisms could perform aerobic denitrification under heterotrophic conditions,so that the nitrification and denitrification of microorganisms could be carried out in the same reactor,thus reducing the investment and operation cost of biological denitrification process.However,the research on the influencing factors and reaction mechanism of the denitrification process of heterotrophic nitrification-aerobic denitrification(HNAD)functional microorganism is not enough.Pseudomonas sp.ZSY was a HNAD denitrifying bacterium screened from Binzhou estuary of Guangxi province.The ability of the bacterium to degrade ammonia and produce nitrogen under aerobic conditions has been previously demonstrated,but the effect of a number of factors on the HNAD process and its mechanism have not been explored.In this study,Pseudomonas sp.zsy was selected as the research object,and its ability to degrade nitroso and nitroso in aerobic conditions,as well as its HNAD and synchronous nitrification denitrification(SND)reaction process were investigated by changing different reaction conditions.The results are as follows:Pseudomonas sp.ZSY had the strongest aerobic denitrification ability when sodium citrate was used as carbon source,C/N was 15,and the inoculation amount was 1%(V/V).Higher temperature and initial pH value do not inhibit the degradation process of nitrate nitrogen and nitrite nitrogen,but seriously inhibit the process at low temperature and low pH value.The higher the DO in the system,the faster the degradation rate of nitroso.Under optimized reaction conditions,the bacteria showed good aerobic denitrification performance and could remove 97.4%of nitrate nitrogen within 12 h.When Pseudomonas sp.ZSY took ammonia nitrogen as the only nitrogen source,it could reduce ammonia nitrogen to nitrogen under aerobic conditions,and the reaction system basically had no accumulation of hydroxylamine,nitrate nitrogen and nitrite nitrogen.When C/N was less than 15,ammonia nitrogen in the system could not be completely degraded,and higher C/N slightly inhibited the HNAD process of the bacterium.The bacteria can tolerate higher ammonia nitrogen concentration to a certain extent.When the initial ammonia nitrogen concentration is 720 mgN/L,the bacteria can still degrade 28.7%ammonia nitrogen within 48 hours.The higher rotating speed of the shaking table was beneficial to the degradation of ammonia nitrogen,promoted the HNAD process of the bacterium,and accelerated the degradation rate of ammonia nitrogen.Pseudomonas sp.ZSY had obvious synchronous nitrification and denitrification when various inorganic nitrogen sources were used as nitrogen sources.When ammonia nitrogen and nitrate nitrogen were used as nitrogen sources,the bacteria preferentially degraded ammonia nitrogen,and then nitrate nitrogen and ammonia nitrogen were degraded simultaneously.With the increase of added carbon source,the denitrification process was inhibited and the degradation rate of nitrate nitrogen decreased.When ammonia nitrogen and nitrogenous nitrogen were used as nitrogen sources,the bacteria had the same priority to degrade ammonia nitrogen,but the degradation of nitrogenous nitrogen was lagging behind.The optimal C/N of the SND process is 15,and when the C/N continues to increase,the degradation rates of both ammonia and nitrite nitrogen will be affected.When there is no ammonia nitrogen in the system,the degradation process of nitrite nitrogen will not be affected. |
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