Isolation And Identification Of Aerobic Denitrifiers And Study On Denitrification Characteristics

The situation of water pollution in our nation is very serious. In rivers and lakes nearby cities and suburbs, nitrogen pollution which may cause water eutrophication, blackening and smell is particularly acute. And some negative effect to the development of industry and agriculture and residents’daily lives is also brought by it. In this study, an aerobic denitrifier was isolated from environmental samples and its denitrification properties were explored. The primary results were as follows:(1) A high efficient denitrifier named ADH1was isolated from activated sludge by enrichment culture and BTB plates. The isolate was identified as Pseudomonas stutzeri through the phylogenetic analysis based on its16S rDNA sequence and biochemical characteristics. Two functional genes (nirS and nosZ) related to denitrification were also found in this strain. The phylogenetic analysis based on the sequences of these genes also proved that strain ADH1belongs to Pseudomonas sp.(2) Ammonium was utilized by the strain through assimilation, and the utilization rate was increasing with the raise of dissolved oxygen content. The rate could reach96.3%in12hours under rocking cultivation. It had two ways to convert nitrate. The conversion rate of nitrate got to96.1%in16hours under static cultivation, and more than84.7%nitrate was totally removed from the cultural medium by denitrification. While the strain was cultured under rocking cultivation (150r/min), the conversion rate of nitrate reached97.8%and the removing rate of total nitrogen was over40.0%in10hours. All these results indicated that ADH1was an excellent aerobic denitrifier.(3) The results from Plackett-Burman design and Response Surface Methodology indicated that the mainly influence factors of denitrification about ADH1were carbon nitrogen ratio, dissolved oxygen and temperature. When these three factors were14.9,250mL and37.35℃respectively, the removing rate of total nitrogen could reach94.3%. The denitrification efficiency of ADH1was also studied under no aeration and aeration. The trends of nitrite, nitrate and total nitrogen showed that ADH1couldn’t strengthen denitrification under no aeration. While dissolved oxygen was maintained between3.00mg/L and4.00mg/L, in the experimental group which added ADH1, the conversion rate of nitrate and the removing rate of total nitrogen were significantly higher than that of other groups. These meant the denitrification efficiency in wastewater could be significantly enhanced by ADH1under aerobic condition.(4) PCA analysis based on DGGE profiles indicated that the in situ bacterial community could be changed when carbon source or ADH1was added in wastewater. The DGGE profiles also showed that ADH1could colonize in wastewater during a given period, which demonstrated the strain had good adaptability in environment. The above researches proved that ADH1is a fine aerobic denitrifier and has a good application prospect in bioremediation for nitrogen enriched wastewater.