| Facing the increasing deterioration of the water environment quality and the increasingly serious eutrophication phenomenon, high efficiency and rapid removal of nitrogen in water was an important subject in the field of water pollution prevention. Because discontinuity and low efficiency of traditional biological denitrification process greatly limited the application and development of the biological denitrification technique, heterotrophic nitrification and aerobic denitrification bacteria was found to overcome this defect and provided a new way for the new biological denitrification technology. In order to provide theory and technical support for basic research of wastewater biological nitrogen removal, denitrification characteristics of heterotrophic nitrification and aerobic denitrification bacteria was deeply researched in this paper.(1) A strain of heterotrophic nitrification and aerobic denitrification bacteria YX02 was screened from aerobic activated sludge in the experiment. By biological identification and 16 S r DNA homology analysis, the bacteria was identified as a strain of Burkholderia sp.. The most appropriate nitrogen removal conditions for the bacteria was: carbon source sodium succinate,temperature 30 ℃, p H 7.0, C/N 10.5 and shaking speed 120 r/min. When heterotrophic nitrifying,the ammonia removal rate was 88.7% within 72h; When aerobic denitrifying, the nitrate removal rate was 55.3% within 72 h, but the nitrite removal rate was almost zero. In the mixed system of hydroxylamine and nitrate, hydroxylamine removal competed with nitrate and then nitrate removal assumed absolute superiority. Only when the hydroxylamine was abundant(namely NH2OH:NO3--N more than 7:3) hydroxylamine preferred removing, and hydroxylamine would suppress nitrate removal. The enzymology indicated that HAO and NAP was the key enzymes in nitrogen removal, they decided the denitrification characteristic of the strain. Combining with the end denitrification product analysis, we speculated that the mechanism of nitrogen removal by the strain might be: Under aerobic condition, when ammonia nitrogen regarded as the only nitrogen source, ammonia was first nitrified to hydroxylamine, then denitrified to gaseous nitrogen; When nitrate as the sole nitrogen source, part of nitrate was assimilated by the strain,others was directly denitrified to gaseous nitrogen; but nitrite could not be removed.(2) The optimal reaction conditions of ammonia nitrogen and organic wastewater byenhancing treatment was: temperature 25℃, p H 7.0, C/N 10, embedding ball quantity 80g/L.Under this condition, the ammonia nitrogen and COD removal rate were 90.7% and 82.4%,respectively. The embedding ball quantity had the biggest effect on the treatment efficiency. And under different influent flow rate and ammonia nitrogen concentration conditions, compared with bioaugmentation by adding the bacteria directly to the continuous flow reactor, bioaugmentation by adding embedding immobilized bacteria could not only enhance the ammonia nitrogen and COD removal rate obviously, but also the resistance ability of ammonia nitrogen loading and organic loading.(3) The microbial diversity in the reactor was rich, the microbial structure existed differences in different operation phases. The microbial communities in the system of succession eventually formed a stable niche. The operation of the reactor collected closely with the change of diversity index, the diversity index was significantly different with each other between the sludge samples, later phase formed a new community structure. UPGMA analysis divided the operation processes into three stages, and different stages existed certain evolution relationship.PCA showed that during the operation of the reactor, inferior strains was largely eliminated,predominant strains survived, and later period formed a new structure composed of embedding bacteria. CCA showed that NO2--N had the biggest effect on microbial community structure,NO3--N, NH4+-N and COD followed, p H had the weakest effect. |
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