Screening Of Heterotrophic Nitrifier-Aerobic Denitrifier Acinetobacter Sp. Y1and Characterisation Of Its Nitrogen Removal

Nitrogen is one of the most important pollutants in the water pollution. The excessive emission of nitrogen is a major cause for the eutrophication. Nowadays, biological nitrogen removal had become an important method to remove the excessive nitrogen in the polluted water. The heterotrophic nitrification bacteria were widely existed in the nature with a large quantity of species, multi-strains of which were isolated with the characteristic of aerobic denitrification. Although these bacteria had both heterotrophic nitrificated ability and aerobic denitrifying ability, they belonged to different bacteria genus and displayed different characteristics in nitrification performance, nitrification products, denitrification performance and heterotrophic nitrification-aerobic denitrifcation performance. Thus it is necessary to isolate new heterotrophic nitrification-aerobic denitrification bacteria from different circumstances and conduct further researches on their characteristics, which can help enrich nitrogen-removal microbiological species and related methods.At present, the isolation of heterotrophic nitrification bacteria and its related research were concentrated on the natural environment, including the river, lake, ocean, forest soils and so on, and on the low-nitrogen concentration domestic sewage. The researches about the high-conentration amonia nitrogen industrial sewage were rare. In this study, a strain of heterotrophic nitrification bacteria Y1with high-performance amonia nitrogen removal characteristic was seperated, isolated and purified from the activated sludge in the coking wastewater biological treatment plant and the elaborated studies on its characteristics were conducted.The colony of Yl is ivory yellow, opaque. Strain Yl is short rod-shaped, gram-negative and aerobic.The identify of strain Y1result shows that it was identified as Acinetobacter by phylogenetic analysis of its16S rDNA gene sequence, and named Acinetobacter sp.Yl.Characteristic of heterotrophic nitrification by Acinetobacter sp.Yl show that, ammonia nitrogen can be degradated from110mg/L to0.95mg/L in20h under culture conditions of C/N=14,30℃,120rpm.The most efficient on growth and nitrogen removal of strain YL was obtained in supplemented with sodium citrate as carbon source. When sodium citrate supplemented as carbon source the best C/N condition for Y1is15, and the most efficient NH4+-N removal and growth rate occurred under the conditions of pH7,150rpm and30℃. And high concentration of ammonium range from400mg/L to1600mg/L could be degradated well by strain Y1.The nitrification products and enzyme activity test shows that hydroxylamine (NH2OH), nitrite (NO2-) and nitrate (NO3-) were not detected during heterotrophic nitrification. And the activity of HAO was lower than NR and NIR.To aerobic denitrification, hydroxylamine could not be used by strain Y1. High concentration of nitrite (200mg/L) and nitrate (200mg/L) could be removed by strain Y1, when they were provided as sole N-source, respectively. The most efficient nitrogen removal was occurred at C/N=20when nitrite or nitrate was offer as sole N-source.