Isolation,Identification And Nitrogen Removal By A Novel Heterotrophic Nitrification-Aerobic Denitrification Bacterium Ochrobactrum Anthropi LJ81

Nitrogen contaminants are widespread presence in waters,expecially in municipal and industrial wastewater,which have been an urgent environmental issue nowadays.There are many disadvantages of the traditional biogical methods of nitrogen removal,such as large occupation,sludge disposal and N₂O potential release.The discovery of heterotrophic nitrification and aerobic denitrification?HN-AD?bacteria gives an alternative for biogical nitrogen removel,due to its high performance of nitogen and carbon remval and the accompliment of simultaneous nitrification and denitrification?SND?.Here,we chose HN-AD bacteria as the subject of this study,explored the properties of growth and nitrogen removal and constructed a biogical aerated filter?BAF?with bioaugmentation to achieve efficient ammonia removal.In this study,we isolated an HN-AD bacterium termed as LJ81 with high performance of nitrogen removal.Phylogenetic tree was constructed based on sequencing 16S rRNA.The morphology and aerobic denitrification reductases were characterized.The growth and nitrogen removal propertites of strain LJ81 under different conditions were investigated.The mechanism of HN-AD process by strain LJ81 was illuminated,and the growth and nitrogen remival kinetic models were developed.In addition,we combined a BAF with bioaugmentation of strain LJ81,and its possibility of achievement of SND was evaluated.The results indicated as follow:?1?Intermittent aeration with selective medium accelerated the enrichment of aerobic denitrificans.The 16S rRNA sequence?1330 bp?and phylogenetic tree indicated that strain LJ81 affiliated to genus Ochrobactrum anthropi with high similarity?100%?.The genes of aerobic denitrification reductases were amplified by using specific primers,suggesting that the genes of nirK,nirS,cnorB and nosZ,which encode copper-dependent Nir,haem-dependent Nir,Nor and Nos,respectively,were detected in strain LJ81.Among these,the co-occurrence of nosZ and nirS genes meant that nirS-type denitrificans were more likely to conduct completely denitrification without accumulation of N₂O;The co-occurrence of nirK and nirS genes confirmed that there might be less nitrite accumulation during HN-AD process.?2?O.anthropi LJ81 could survive in a wide range of pH?5-9?condition and achieved the highest performances of growth and nitrogen removal under higher levels of DO(6.08 mg L^-1)and COD?C/N>20?.Besides,O.anthropi LJ81 could utilize ammonia,nitrite and nitrate as sole nitrogen source efficiently,and their removal rates were 3.846,4.12 and 4.16 mg-N L^-1h^-1,respectively.?3?O.anthropi LJ81 had the outstanding performance of HN-AD process and could accomplish SND process.Moreover,strain LJ81 conducted nitrification prior to denitrification without nitrite accumulation during HN-AD process.The nitrogen removal by O.anthropi LJ81followed complete nitrification-denitrification process,and there might exist partial nitrification-denitrification.In addition,the kinetics of substrate utilization were obtained by combination of the cell growth and nitrogen removal kinetics,and the models were suitable and strong correlation under all conditions.?4?The bioaugmentation of one-stage BAF with O.anthropi LJ81 enhanced nitrogen removal performance significantly and realized SND process in lab-scale.The average removal efficiencies of COD,TIN and ammonia of BAF increased by 8.2%,50.9%and 9.0%.The bioaugmentation of one-stage BAF was feasible for improving its nitrogen removal performance,which provided the reliable experimental foundation for developing a one-stage BAF with bioaugmentation by HN-AD bateria and the achievement of SND of bioreactor.