| In recent years, excessive nitrogen of our surface water is very serious, which has significant impact on resource function and utilization value of surface water bodies. Existing ecological floating bed technology are widely used in surface water purification with its less investment, great effectiveness, convenient operation and maintenance, and no secondary pollution. But denitrification of traditional ecological floating bed mainly relies on aquatic plants, subject to the amount of floating bed plants, so combination of ecological floating bed research is necessary. The main contents of this paper include:enrichment screening denitrifying bacteria, denitrifying bacteria, nitrification bacteria, ammoniated bacteria, embedding denitrifier bacteria group with sodium alginate, adding inorganic carrier to strengthen the mechanical properties of biology base and studying the optimal solution of bio-base preparation. The research chooses five supplied experimental plant, Iris tectorum Maxim, calamus, Lythrum salicaria,Umbrella plant,Canna indica to build combined floating bed in order to study the impact of HRT, illumination conditions and dissolved oxygen concentration on denitrification effect of combined floating bed. Finally, combined floating bed is applied to natural water bodies to study the denitrification effect of natural water bodies. Main connsclusio of this research are as follows:(Ⅰ) an efficient denitrifying bacteria strain XH2 is chosen from the mud mixture of the reflux wells in Wangtang sewage treatment plant, with its ammonia and nitrogen degradation rate of 60.4% and the strain is identified as Klebsiella Oak Esposito, an efficient denitrifying bacteria FXH1, which has 73.5% removal rate against NOx-N reached percent, is identified as Bacillus; an efficient ammoniated bacteria AH2, is preliminarily identified as Klebsiella; a nitrification bacteria YXH-5 is identified as β-Proteobacteria Nitrosomonas sp.(Ⅱ) Sodium alginate as embedding body, through bio-based comprehensive performance study, the immobilized optimum conditions is finally determined as 1.5% sodium alginate concentration,12 h crosslinking time,2 g cell dosage, and the best inorganic carrier is charcoal with4g dosage. In addition, through mixing 3% CaCO3 powder in sodium alginate, denitrification effect and mechanical strength of the biology base can be improved. Biology base prepared through this way has advantages of large bio-based microbial density, fast response, and strong resistance to environmental impact and reaction process easier to control and so on.(Ⅲ) When HRT equals to 5 d, combination of ecological floating bed has the best purification effect on TN, NH3-N in the simulated wastewater, in which removal rate of Canna combined floating bed against TN, NH3-N is up to 93.6%,96.6%. Light condition has greater impact on plant’s height, branch length and leaf area. Under weak lighting conditions, plants are prone to vain growth, while under strong lighting conditions, suppression phenomenon may appear to reduce photosynthesis photoinhibition, resulting in the decreased growth rate of plants. Dissolved oxygen concentration has a certain impact on nitrification and denitrification of plant roots and microorganisms. For combined ecosystems, oxygen secretion of influent DO, atmospheric oxygen, and plant roots can meet the demand for oxygen quantity of the combined floating bed, without additional increase of aeration equipment. When HRT equals to 3d, combination of ecological floating bed has a good nitrogen removal rate against natural water bodies. Thereinto, Canna combined floating bed has the best effect and its removal rate against TN、NH3-N is 86.5%,93.7% respectively, which makes effluent water quality up to III standard of the surface water. |
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