Screening And Identification Of Highly Efficient Heterotrophic Nitrifying Bacteria And Their Studies On The Characteristics Of Ammonia Denitrification

Due to the progress of the national economy to drive the rapid development of the industry,the industrial,agricultural and urban living water emissions caused by Chinese water resources suffered from ammonia nitrogen and other nitrogen compounds pollution serious,especially the lake pond water,landscape water and the river water,their degree of eutrophication is also relatively increased,not only bring threaten to the animals,plants and cycle of the ecological environment,but also on Chinese economic progress and the health of residents posed a threat.For the treatment of nitrogen pollution in water,the traditional physical and chemical denitrification process is very complex and difficult to control,and the large number of application of chemical pharmaceuticals is caused by secondary pollution.But the effect denitrification of biological nitrogen removal is remarkable,it also have the advantages of saving the resources and power and it has a good application prospects.The results showed that the heterotrophic nitrifying bacteria had the advantages of short growth period,extensive substrate utilization and strong adaptability to the environment,and the use of heterotrophic nitrifying bacteria for denitrification and shortening the reaction.The nitrification and denitrification can be carried out in the same reactor.Therefore,the biological denitrification process of heterotrophic nitrifying bacteria has been paid more and more attention.The purpose of this study is to screen out the heterotrophic nitrifying bacteria with high efficient nitrification.The immobilized compound bacteria is used to carry out the wastewater denitrification treatment to improve the degradation ability of the nitrogenous sewage.And provide a new direction for the development and application of biological denitrification process.Therefore,this paper to use the sedimentation of the sludge in the sewage sludge from the urban sewage outfall and the sedimentation tank of the sewage treatment plant to screen the heterotrophic nitrifying bacteria.Sieves and re-screening were used to screen out four strains with high ammonia nitrogen degradation effect.Morphological observation,molecular identification and phylogenetic tree were used to analyze the results.Four strains were identified as Gram-negative bacteria,club-shaped or rod-shaped cells.Strain Y1-3-1 belong to Acinetobacter sp.,A2 belong to Enterobacter cloacae,T1-2 belong to Pseudomonas aeruginosa,F4 belong to Providencia rettgeri.The effects of carbon source,nitrogen concentration,temperature,pH and speed on the growth status and nitrification characteristics of strains Y1-3-1,A2,T1-2 and F4 were studied.The results showed that four strains the optimum conditions were pH7-8,30℃,150r/min shaking culture.When the initial ammonia concentration was 100mg/L,the degradation of ammonia nitrogen was carried out with sodium acetate as the carbon source and ammonium nitrate as the nitrogen source.The rate of Y1-3-1 was 73.7%,A2 was 64.8%,T1-2 was 78.0% and F4 was 72.5%.In order to further improve the ammonia nitrogen degradation ability of the strain,the immobilized compound bacteria were constructed and the four strains were mixed and cultured.Design different factors,the orthogonal experiment was carried out to compare the inoculation amount of four strains,the best immobilized materials.The results showed that the best inoculation ratio of strain Y1-3-1,A2,T1-2 and F4 was 5: 2.5:1:5.According to the physical parameters and stability and mass transfer of immobilized pellets,the optimum ratio of immobilized material is PVA 4%,SA 2%,CaCl2 3% and zeolite 3g.The immobilization method is carried out by the immobilization method combined with adsorption and embedding method.The removal rate of ammonia was up to 96.8% and the removal rate of COD was 92.4%.Compared to single strain,the removal efficiency of nitrite and nitrate nitrogen were not found in the process of ammonia nitrogen degradation,and the bacteria had some ability to remove the total nitrogen.The effects of the factors such as the addition amount,temperature and pH on the degradation effect of immobilized compound bacteria were studied by the experiment of immobilized bacteria.The results showed that the suitable conditions of the immobilized compound bacteria were: simulated ammonia nitrogen wastewater,initial pH8.0,culture temperature 30° C,addition amount 50g/L.