Study On Denitrification Mechanism And Flocculation Characteristic Of Aerobic Denitrifying Bacteria

Study on aerobic denitrifying bacteria has been a hot spot at home and abroad since they were found. According to some results, aerobic denitrifying bacteria can remove nitrate under aerobic condition although mechanism of aerobic denitrification is not very clear, which overcome the defects of technology of anoxic denitrification. The bright idea is that they can get rid of nitrogen under aerobic condition and have strong potential application on nitrogen removal from wastewater. High effective aerobic denitrifier were screened and isolated from environment in the paper. Their characteristics were also studied for developing the knowledg of aerobic denitrification.Two strains of aerobic denitrifiers which were named as ADB4A and ADB7were screened and isolated. Nitrate concentration of water inflow was set as268.8mg·L-1. Nitrate loss by strains ADB4A and ADB7were83%and63%respectively at30℃,160r/min after48hours culture. They were identified as Bacillus pumilus and Bacillus licheniformis by16SrDNA sequences determination.In order to know more and properly use aerobic denitrifiers, singel factor analysis was used to discuss the best growth condition of strains and environmental effect on aerobic denitrification, which were carbon sources, nitrogen sources, C/N ratio, temperature, pH, rotate speed and inoculum size. The best parameters were obtained. The results showed that ADB4A and ADB7grew well in the condition of30℃,200r/min. The optimal carbon and nitrogen sources were sodium citrate and peptone, respectively. The best C/N of ADB4A and ADB7was9and20, respectively. Nitrate concentration of water inflow was set as265.0～275.0mg·L"1when studying on performance of aerobic denitrification. Nitrate removal rate of tow strains could reach above95%after4days culture in optimal conditions.In the process of aerobic denitrification, various forms of nitrogen including organic nitrogen, ammonia nitrogen, nitrate, nitrite were constantly transformed. The transformation of nitrogen was studied by using strain ADB4A. It was found that TN in the waste water went down continually and its removal rate was more than83%after4days. The nitrate removal rate was99%after4days. But nitrite and ammonia nitrogen were accumulated in the process.A large number of literature showed that a lot of bacteria had characteristics of aerobic denitrification and the flocculation. Flocculation of two strains ADB4A and ADB7was studied for the first time. The results indicated the flocculation rate of strain ADB7was up to22%and the strain ADB4A was up to46%. All of them had characteristics of flocculation.