Screening And Identifying Of A Novel Denitrogenation Microorganism And Study On Its Nitrogen Removal Mechanisms

Nitrogen is one of major pollutants of water pollution,and can cause water eutrophication.Biological denitrogenation is a method used most widely in wastewater treatment. But it needs two procession,} .e. aerobic nitrification and anoxic denitrification,to change ammonia to dinitrogen,which makes this method more complex. The discovery of heterotrophic nitrification bacteria recently years,which can nitrify and denitrify simultaneously, gives a new principle to biological denitrogen.But nitrite or nitrous oxide can be a harmful by product in nitrogen removal by most heterotrophic nitrifier as yet reported. In this study a strain of heterophic nitrifier was screened which could directly convert ammonia to dinitrogen and produced little nitrite and nitrous oxide.Six strains of bacteria which could heterotrophic nitrify was isolated. Strain YY-5 could' remove nitrogen most rapidly in these 6 strains,which could reduce ammonia from 58mg/l to zero in 24 h Strain YY-5 was identified as Acinetobacter genus,and named as Acinetobacter sp.YY-5.The most optimal nitrogen removal condition was 30℃, C/N=12, pH=10.0. Little nitrite and nitrous oxide,as expected,was produced during the nitrogen removal by Acinetobacter sp.YY-5, and the quantity of dinitrogen in the headspace and pH of the culture media were increased in evidence,without ammonia gas volatilization.These characters were much different from autotrophic nitrifier.Nitrogen removal mechanisms of Acinetobacter sp.YY-5 were studied by determining the nitrogen compound production during nitrogen removal and analysising some related gene and protein. The hydroxylamine oxidase(HAO) in Acinetobacter sp.YY-5 extract could remove hydroxylamine and yield Na but not nitrite ,which made it much different from those reported ones. Acinetobacter sp.YY-5 could not make aerobic denitrification but could produce dinitrogen .It's believed that the nitrogen removalmechanisms of Acinetobacter sp.YY-5 were different from the reported ones,and led us to develop a working model for the nitrogen removal of Acinetobacter sp.YY-5,i.e. ammonia was converted to hydroxylamine by ammonia monooxygenase(AMO) and then produced hydroxylamine was converted directly to dinitrogen by HAO.Nitrogen removal ability of Acinetobacter sp.YY-5 was evaluated in the domestic sewage N chemical industrial wastewater. food industrial wastewater and garbage percolate.It's found that the growth and nitrogen removal ability of Acinetobacter sp.YY-5 depended much on the quantity of small molecule carbon source ,and nitrogen removal rate of Acinetobacter sp.YY-5 in every wastewater with small molecule carbon source was evidently and ranged from 82.93%to 94.35%.