| With the increasing severity of the eutrophication, the removal of nitrogen pollution has become a focus problem in wastewater treatment field. Bio-nitration is a common technique about the removal of nitrogen in wastewater at present. Two forms of nitrogen element in the water are organic nitrogen and inorganic nitrogen. Because of the different requirement of the different nitrifiers and denitrifiers for nourishment, the process of removal of nitrogen is very complex and the application is limited. Recently, some new typical bacteria by which nitrogen can be effectively removed have been found. This provides a new method for developing the application of the biological removal of nitrogen. In this experiment, a strain of bacteria which has the capacity of aerobic denitrigenation and heterotrophic nitrification was screened. Because of their advantages such as enhancing the treatment effect, reducing the area and reducing the treatment process flow etc, simultaneous nitrification and denitrification process has been widely put attentions. The process was studied heterotrophic simultaneous nitrification and denitrification was studied in SBR.A method of screening of heterotrophic nitrification bacteria that had higher nitrogen removal efficiency was introduced through combining the traditional separating and the modern molecule biology method. The effect of organic carbon on the nitrification was discussed. The results showed that as the organic concentration of influent gradually decreased, the removal rate of ammonia nitrogen escalated, ammonia nitrogen concentration of the effluent decreased. The average ammonia nitrogen removal rate was 64.38% in 15~21day. The PCR-DGGE profiles showed that as the organic carbon decreased, the nitrifiers dominated over heterotroph in their competitions. At the same time, a mass of heterotroph, those of which had weak adaptability or heavy depended on organic carbon source, were eliminated. Microorganism varieties decreased dramatically in the process of evolvement of bacterial community structure. There were co-genus and also relatively specific germ genus in different operation periods of bio-ceramic reactor. All germ in bio-ceramic reactor constructed a ecological community frame. 2 heterotrophic nitrobacteria and 6 autotrophic bacteria were screened from bio-ceramic reactor. The process of removing ammoniac nitrogen was done by setting the heterotrophic nitrification bacteria and aerobic denitrifiers on the sequencing batch reactor. The average ammonia nitrogen removal rate was 59.8% in 22-31day. The profile show that In day 15, the species of microorganism has a high variety, and has more dominant species (19 species). In day 15 and 30, different microorganism species have a high species-similarity (85.71%). The process of species evolvement seems that the structure of germs trends to be steady.SHY5 which can develop and increase is dominant bacterium in SBR reactor.6 heterotrophic nitrobacteria screened from bio-ceramic reactor was adopt the sodium acetate and ammonium chloride as the culture medium to research the character of nitration. Through the 12 days'culturing the COD removal rate could reach to over 45 %,TN and NH4-N removal rate could reach over 60 %, and it also had the function of producing NO2-N. According to the physiological biochemical index, six strains of heterotrophic nitrobacteria are generally identified respectively such as Pseudomonas.sp ,Acinetobacter.sp. The ecological factors affecting the nitrification efficiency of heterotrophic nitrifying bacteria were discussed. The results showed that the best temperature for heterotrophic nitrobacteria wgy5,wgy21 and wgy33 was 30℃, the best pH is the weak alkaline. The process of removing ammoniac nitrogen was done by setting the heterotrophic nitrification bacteria on the sequencing batch reactor. And the efficiency of ammoniac nitrogen removal can reach up to 82.96% as the reactor works smoothly. When the temperature is 29℃, the removal rate of the ammonia-nitrogen and TN are 82.28%and 47.27%, so with the higher of the temperature the heavier of the removal rate. The pH also has the more effect on the removal rate. As the pH is 8.0 the removal rate of ammonia-nitrogen is 80.15%, and in the acidity it doesn't have the nitration effect at all. The denitrification is good at the pH 7. As the C/N rate is less than 4.5, the removal rate of the ammonia-nitrogen and the TN increased. As the C/N rate is 6, the removal rate of the ammonia-nitrogen is 73.37. As the C/N rate is 9, the removal rate of the ammonia-nitrogen reached down to 52.84. The PCR-DGGE profiles showed that the wgy5, wgy21 w gy68 were the dominant bacterium in SBR reactor.The process contained sludge acclimation for enrichment of aerobic denitrifiers, bacteria isolation and purification, initial screening by measuring TN concentration and second screening by measuring trace of nitrogen element. After second screening, 5 strains were confirmedly capable of co-respiring by using nitrate and oxygen as electron acceptor and molecular nitrogen was the end product of denitrification. Dentitrification mainly occurred in LOG pH ase of the strains and during the denitrification of the strains, pH in the culture medium increased while ORP in the medium decreased. According to their physiological and biochemical index analysis and the sequence analysis of 16SrDNA, it was confirmed that the strain f1, f2, f3, f4andf5 showed that the f1, f3, f4, f5 strains belong to Pseudomonas sp., the f2 belongs to paracoccus sp., respectively. The removal rate of 5 strains denitrifiers are 100%, 99.98%, 99.98%, 94.91% respectively. As C/N ration was above 5, it can be denitrificated completely. The 5 straits of denitrifiers basicly don't have the ability of nitrification. It showed that the 5 strains of denitrifiers can use the ammonia-nitrogen to develop and increase but the removal rate of ammonia-nitrogen is below 30%. We set up a continuous flow reactor with the 5 screened denitrifiers. As the reactor run into the steady level, the removal rate of nitrate is at about 98.16%.By the analysis of PCR-DGGE the f3 and f5 became the superiority bacteria. At the end we use the heterotrophic nitrobacteria, aerobic denitrifiers and the COD degradation bacteria with high efficiency to set up the SBR reactor, the removal rate of ammonia-nitrogen can reach to 92.12%, the average removal rate of TN is about 74.15%, and the removal rate is 86.27%.As the reactor run into the steady level, the removal rate of ammonia-nitrogen can reach to 91.14%, the average removal rate of TN is about 79.03%, and the removal rate is 87.18%. Through the experimentation it showed that the heterotrophic nitrobacteria and the aerobic denitrifiers have the important role in the SND, and it provide the environment factor influence microorganism hypothesis, the most important is that it developed the microbiology and bring forward the hypothesis of the environmental bacteria.
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