Study On Characteristic Of Heterotrophic Nitrification And Aerobic Denitrification By A Starin Of Bacillus Licheniformis

Nitrogen is an important source of water contamination, which can causedamage to the water environment. In our country, a large amount of nitrogen isreleased into all kinds of water body in every year. At present, biologicaldenitrogenation is a method used most widely in wasterwater treatmentespecially for municipal sewage. Compared with other denitrogenation process,biological denitrogenation has advantages of low-cost, non-secondary pollution.Nitrogen is removed by biological denitrogenation from wastewater by theprocesses of nitrification followed by denitrification which is achieved bydifferent types of microbes, that is nitrifiers and denitrifiers respectly. Thenutrient source and the breath of the types of microbes are absolutely differenttherefore the biological denitrification processes are complicated and it is notbenefit to the implementation of these biological processes. With the development of the theory of biological denitrogenationtechnology, some aerobic denitrifying bacteria and heterotrophic nitrificationbacteria have been found recently. It is possible that co-existence ofheterotrophic nitrification and aerobic denitrification in one reactor. A lot of newbiological denitrogenation technologies appear in recent years.A new biologicaldenitrogenation process is widely applied in Japan and Korea.This paper studiesthe ability of denitrification of a strain of bacillus licheniformis. It is believedthat the study will contribute to the development of biological denitrogenationtechnology and the operation parameters.This paper studies on the characteristic of denitrogenation and the growthof a strain of bacillus licheniformis. The orthogonal experiment of four factorsand three levels was designed to research the best conditions of aerobicdenitrification.The conclusions are as follows:(1)Test strain were able to perform aerobic denitrification and heterotrophicnitrification by using sodium succinate as the sole carbon and energy, usingpotassium nitrate or ammonium sulfate as the nitrogen source. The strain had ahigh removal rate of concentration of nitrate nitrogen. The initial concentrationof nitrate nitrogen was152.5mg/L and it was completely degraded within36hours. Nitite nitrogen accumulation appeared during this process. Orthogonalexperiments indicated that COD/N and DO are significant influential factor andthe best condition is COD/N=14, temperature=30℃, n=70r/min, and pH=7.0. (2)With sodium succinate as the sole carbon and energy source, nitritenitrogen degradation was simulated by Haldane model at the nitrite nitrogenconcentration range of0~1000mg/L. Results show that the fitted curve had agood correlation with test results with R2=0.997, μmax=1.30h-1, KS=466.37mg/L,Ki=179.65mg/L. NIR activity assaysis indicate that tested strain in thelogarithmic phase produce a large quantity of NIR and the maximus activityreach to0.282(U/mg protein).(3)The test results of heterotrophic nitrification characteristics show thatthe ammonia nitrogen of the initial ammonia nitrogen concentration of84mg/Lcan be degraded to30mg/L within24hours. The best condition of heterotrophicnitrification is sodium succinate, COD/N=14, pH=7.0, temperature=30℃andn=110r/min.