| The recent years, the nitrogen pollution is becoming more and more serious. Sewage treatment plants in China are also required to reduce conceration of the tolal nitrogen in effluent. Therefore, it is necessary to optimize and research throughly the existing biological nitrogen removal technology, especially the denitrification. This article raises the idea of promoting denitrification by using goethite. What’s more, it makes research on the effect of different carbon nitrogen ratio, the amout of goethite, iron source and nitrogen source types on denitrification process. With the skills of PCR-DGGE and Fluorescence in stitu hybridization, the author makes analysis and characterization of the microbial community structure; He also makes discussion on the perliminary mechanism of enhanced denitrification by goethite, and the influence of goethite on the secondary clarifier effluent biological treatment. Experiment reesults were concluded as the follow:Goethite can promote dentrification when the carbon resource is enough, and it will inhibit dentrification when short of carbon resource. Goethite concentration and the rate of dentrification are not positive correlation. When goethite dosage is 5 mmol/L, the promotion is the most significant. At this time, the rate of nitrate reduction is 0.28 mmol/L, and the rate of N2 production is 0.11 mmol/L. Goethite can effectively reduce the accumulation of nitrite when carbon source is rich.The influence of FeCl2, Fe(OH)3 and goethite on denitrification with the nitrogen source as nitrate and nitrite is different. When nitrogen source is nitrate and nitrite, the promotion degree of Iron source on denitrification process is Fe(OH)3>goethite>FeCl2. And the dentrification reaction in FeCl2 is extremely weak with nitrite as nigrogen source. Goethite can promote secondary clarifier effluent biological treatmente. The degradation rate of ammonia nitrogen is 85.69%, nitrite degradation rate is as high as 100%, and that of nitrate is 66.7%. Concentrations of total nitrogen in the effluent is 2.67 mg/L. Besides, the solution doesn’t contain iron ions, which won’t have effect on the chroma. Labrenzia aggregata and Thauera aredominant bacterias for for denitrification. In addition, Rhodocyclaceae and Clostridiales with the capacity of dissimilatory iron reduction and nitrate dependent Fe(II) respectively are found. |
