Isolation, Identification And Characteristics Of Aerobic Denitrifying Bacteria

In recent years, many domestic and foreign researches and reports have confirmed the existence of aerobic denitrifying bacteria. This discovery broke through the traditional theory, provided a brank-new idea for the biological nitrogen removal, and developed the nitrogen removal technology in sewage which is simultaneous nitrification and denitrification(SND). There are two predominance for aerobic denitrification, one of new technology for biological nitrogen removal, compared with traditional: first aerobic denitrifying bacteria can remove nitrogen under aerobic condition, which makes simultaneous nitrification and denitrification possible. The nitration product may directly become the denitrification substrate, which will suppress the accumulation of the nitrate and nitrous acid and accelerate the process of nitrification and denitrification.Simultaneously, the denitrification compensates the alkalinity consumed during nitrification, stabilizes pH value of reaction system, reduces the operation difficulty and the running cost. Second,aerobic denitrification has been adapted to disposing of large scale sewage due to the characteristic of aerobic denitrification bacteria: excelled adaptability, fast growth, high yield, relative low requirement for dissolved oxygen, fast denitrifing speed and complete reaction. Therefore it is necessary to exploit more aerobic denitrification bacteria and research them profoundly.In order to enrich the aerobic denitrification bacteria, The activated sludge was domesticated in sequencing batch reactor (SBR) reactor by adding rations nitrate and controlling the aeration intensity of reactor to enhance the removal of nitrate under aerobic condition. We screened five aerobic denitrifing bacteria, determined their phylogenetic status by phylogentic analysis based on partial 16SrDNA, and cloned their partial napA gene was cloned, the gene was subunit of periplasmic nitrate reduutase(NAR), which was considered to be relartive to aerobic denitrification.The carbon source test showed that as C/N ratio was 9, all strains can complete denitrification. When sodium succinate was used as electron donor, the denitrification effect was obviously more than that of carbon source and nitrogen removal rate were above 96%. We discussed the co-effect of pH radio and temperature to the denitrification efficiency of strains G2 and G5. When temperature was at 25℃～35℃and the optimal pH value was about 7, the nitrogen removal rate can reach up to 90%. Removal of wastewater containing nitrate nitrogen was performed using the activated sludge with aerobic denitrifying bacteria on continuous-flow reactor. The results showed that the average removal rate of nitrate nitrogen can be up to 98.35%, the average removal rate of COD can be up to 91.11% and the nitrite nitrogen in the effluent was kept in a lower level during the stable operating period, with pH radio was 6.3～7.5, influent COD loading of 402.14～288.57g/ (m~3·d) and nitrate nitrogen loading 105.98～91.56g/(m~3·d) at 20℃～25℃, and the dissolved oxygen concentration was kept at a high level(≥5mg/L). The results of DGGE showed that during the stable operating period, the aerobic denitrifying bacteria, G2 and G5, existed steadily, which were the dominant microorganisms all the time.