Isolation, Identification Of New Aerobic Denitrifying Bacteria And The Immobilized Denitrogenation Study

There are many environmental issues appeared with the rapid development of China’s economic, agricultural and industrial. Eutrophication of the water environment is particularly prominent among these questions. Large amounts of nitrogen, phosphorus and other elements which come from human activities drains off into water, resulting in serious environment pollution and the death of fish. The development of aquaculture has also been restricted. Biological denitrogenation played an important role in the governance process of eutrophic water bodies, especially aerobic denitrification. Therefore, isolation of efficient aerobic denitrifying bacteria from the natural environment has important research value and theoretical significance.Sixteen aerobic denitrifying strains were isolated from the soil samples in wushan Hubei Province where were polluted by the nitrogen for long-term. Three of these strains exhibit outstanding denitrification ability. Among the three strains, one strain named WS-11 was chosed to be the target after denitrification stability test.Strain WS-11 was preliminary identified as Pseudomonas genus (Pseudomonas sp.) through the morphology observation, physiological and biochemical characteristics of identification and molecular identification and phylogenetic analysis. The growth characteristics results show that WS-11 could utilize a variety of carbon sources for growth and denitrification, the best carbon and nitrogen ratio is 5:1, the optimum growth temperature is 30 to 35℃, the optimum pH range from 7.0 to 9.0.The results of degradation of nitrate by WS-11 shows that under the aerobic conditions, in a particular medium, the nitrate removal rate reached 95% for 12h and the maximum tolerated concentration of nitrate is 20mmol/L. The result of degradation of nitrite by WS-11 shows that WS-11 could grow by utilize nitrite as the sole nitrogen source. The nitrite removal rate was 79.8% and 100% for 12h and 24h, respectively. The pH value had evident effects on the degradation of the nitrate. The degradation rate of nitrate under pH 7.0 and 9.0 was obviously higher than that of other pH conditions. The pH value had evident effects on the degradation of the nitrate. The degradation rate of nitrate under pH 7.0 and 9.0 was obviously higher than that of other pH conditions. Dissolved oxygen experiments result showed that nitrate removal rate under the low dissolved oxygen concertration was significantly lower than that under the high dissolved oxygen concertration, causing the growth of WS-11 was restrained. WS-11 could carry out denitrification when the dissolved oxygen concertration above 3 mg/L.Immobilization experiment results show that:under the suitable conditions, the denitrification capacity of WS-11 immobilized by the mixed carrier was better than the single immobilization carrier. The nitrite removal rate was 95% by WS-11 immobilized by sodium alginate, polyving akohol and activated carbon, and the nitrite removal rate was 38.5% by WS-11 immobilized by sodium alginate. The denitrification capacity of non-immobilized WS-11was better than immobilized WS-11 under the optimal condition. The percentages of nitrite removal by immobilized WS-11 were significant higher than that of non-immobilized bacteria under high temperatures, low temperatures, alkaline or acidic conditions demonstrating the stable and efficient denitrification capacities of immobilized pellets.