Isoloation And Characteristics Of Aerobic Denitrifying Bacterium In Thermophilic Conditions

Because of the advatantages such as low cost, low secondary pollution and so on,biological denitrification process has been applied in various industrial and agriculturalwastewater treatment. As one of the newest biological denitrification technologies, aerobicdenitrification could achieve higher nitrogen removal efficiency, has strong adaptability and iseasy to control, when compared with traditional anaerobic denitrification technologies.Therefore it has been widely studied in recent years.A bacterium with high nitrogen removal efficiency was newly isolated from a biofilterwhich used to remove NOXfrom flue gas thorough BTB medium and dilution-platemethod.The isolate was identified as Bacillus licheniformis by biochemical studies and16SrDNA gene sequencing analysis. It could use both nitrate and ammonium as nitrogensources, and their removal efficiencies both achieved more than99%within48hours.Optimal conditions for the cell growth and denitrification included sodium citrateascarbon source, C/N of16and shaking speed of160r/min. It is worth mentioning that this strainhas a strong adaptability to temperature changes. The effect of trace metal ions on the growthand denitrifying process was also studied and the result showed that only Fe2+, Ca2+and Mo2+contributed to the removal of nitrogen. Plackett Burman design and response surfacemethodology were used to optimize the aerobic denitrifying medium constitunents includingsodium catrate, monopotassium phosphate, magnesium sulfate and so on. The mediumcompositions were proved to have obvious influence on the growth and denitrifying processof JH8, thereinto, FeSO4·7H2O and CaSO4·2H2O influenced most. Optimal concentrations ofFeSO4·7H2O and CaSO4·2H2O were obtained as0.07and0.04g/L by response surfaceregression model analysis. The denitrification rate increased from7.57±0.13to9.74±0.08mg·L-1·h-1in the following verification test, which confirmed the feasibility of improvingdenitrification effect through optimizing medium compositions by response surfacemethodology.Finally, combined two aerobic denitrifying bacteriaisolated by our laboratory, to dealwith artificial wastewater and found that the mixed bacteria has the same efficientdenitrification ability, even played better than pure starins.These aerobic denitrifying bacteriawill be widely used in the wastewater treatment.