Isolation And Denitrification Characteristics Of An Aerobic Denitrifier With High Nitrogen Removal Efficiency

Through the accumulation of samples, a strain of aerobic denitrifying bacteria A. faecalis DB-19with high denitrification activity was chosen by second screening. Through colony morphology observation and microscopy examination, it shows that the single colony of A. faecalis DB-19is round, neat edged, surface smooth, milky white, and transparent. DB-19single cells are rod-shaped, gram negative bacteria by microscopic examination. The analysis results of16S rDNA sequence show that, strain DB-19and Alcaligenes faecalis16S rDNA is highly homologous, identified as Alcaligenes faecalis.The influences of different environmental factors, which affect its performance of aerobic denitrification, were discussed by single factor experiments. The results showed that the optimum culture of denitrification was sodium succinate as carbon source, COD/N ratio of5,35℃,120rpm. Under this condition,420mg/L nitrate could be significantly removaled within30h; the nitrate removal rate was98.72%, with removal rate high to10.09mg/L·h, TN removal efficiency reached52.58%, which means that high efficient removal of nitrate under the aerobic condition was achieved. Strains DB-19showed wide rage of pH tolerance, and it could proceed aerobic denitrification effectively in the initial pH widely between6and8. The increase of inoculation amount could accelerate its denitrification rate, shorten the denitrogen cycle.A. faecalis DB-19has the capability of heterotrophic nitrification-aerobic denitrification, ammonia can be converted into gaseous products under aerobic conditions, and the toxic substances nitrate and nitrite have not been accumulated, illustrating the ability of simultaneous nitrification and denitrification by a single strain. Through optimization of its heterotrophic nitrification conditions, under the best condition namely succinate as carbon sources, C/N ratio of5,35℃,120rpm, the initial385mg/L ammonia was removed rapidly within36h, and removal efficiency achieved100%, among which16.26%eliminated through aerobic denitrification process,83.73%used for bacteria assimilation synthesis, the maximum ammonia removal rate reached23.23mg/L·h. This showed the high efficient of ammonia degradation ability.These results confirm that A. faecalis DB-19has the efficient heterotrophic nitrification and aerobic denitrification performance.