| China is drought and lack of water strictly,with the development of the cities in China,the amount of wastewater is going up greatly and eutrophication of natural waters is severe,the amount of water resources measuring up the standard reduces rapidly. Economy development is limited by the shortage of water resources. The key issue for controlling eutrophication is improving the wastewater treating rate and reducing the amount of nitrogen in the effluent. So it is important to develop high efficiency and energy-saving middle and small-scale process for point-sources nitrogen removal.This project developed a new style wastewater treatment process for nitrogen removal based on the theory of biological nitrogen removal and the characteristics of biological fluidized beds,that is suspended carriers biological fluidized bed reactor.This process settled aerobic and anoxic zone into one reactor and put suspended carriers into aerobic zone to enhance nitrifying capacity of the system. There is no liquid directing device in aerobic zone and mix gas-liquid-solid equably by changing the position of aeration devices. Stirrer and three-phase separator was settled in anoxic zone to ensure the efficiency of denitrification. In this reactor wastewater goes up from the bottom. This will resolve the problem of occupying large area existed in traditional processes and predigest the process. Carriers is the core part of the process and its material is polypropylene. The outer and inner surface of the carriers is moiréand is easy to be attached by microorganisms. In the recess of the biofilm is thick,the amount of MLSS is high and can reach 9 500～11 000mg/L. At the same time the thick part of the biofilm can form anaerobic zone and simultaneous nitrification and denitrification can achieve. So the efficiency of total nitrogen removal will improve. The density of carriers is low of 0.4～0.45×103kg/m3 and can save power when mixing three phases.This project first studied the efficiency of nitrogen removal using suspended carriers biological fluidized bed reactor. The results show that this process is an effective process for urban wastewater treatment and is suitable for the change of water quality of influent to some extent. The removal efficiency of COD and ammonia is upper and obvious to TN. During the period of experiment the average concentration of COD is 23.59mg/L,the average removal efficiency is 89.52% and the top value can reach 98.38% ; To ammonia the average concentration of the effluent is 6.91mg/L and the average removal efficiency is 83.66%,the top value can reach 96.38%;To total nitrogen the average removal efficiency is 52.49% and the top value is 69.71%.Also the project studied the influence factors for nitrogen removal using suspended carriers biological fluidized bed. This paper discussed influence factors to nitrogen removal such as organic load,influent temperature,pH value and reflux ratio of nitrated liquid. The results show that when organic load is less than 15kgCOD/m3.d,the average COD concentration of effluent is 20.72mg/L and reach the first class of Sewage Comprehensive Discharge Standard; the removal efficiency of ammonia reduced with the increase of influent organic load; but of TN goes up. When the organic load is less than 7 kgCOD/m3.d,TN removal efficiency is low because of the shortage of carbon sources. When it is more than 17kgCOD/m3.d,TN removal efficiency goes down because denitrification is limited with bad nitrification. Temperature is also an important influence factor. The removal efficiency of COD,ammonia and TN go down with the water temperature,and when the temperature is less than 10℃,the activity of bacteria goes down deeply and the removal efficiency of COD,ammonia and TN reduced to 69.62%,62.53%,17.51% respectively,so the critical temperature of this reactor is deemed to 10℃. Nitrifying liquid reflux ratio has little effect to COD and ammonia removal but it affected TN removal greatly. When reflux ratio is 2:1,the average removal efficiency of TN is 48.97% and the value is 59.31 when the ratio is 4:1,and when reflux ratio is 3:1,the average removal efficiency of TN can reach 61.90%This paper also studied the simultaneous nitrification and denitrification in aerobic zone. The concentration of total nitrogen in aerobic zone is lower than that of in anoxic zone and that shows simultaneous nitrification and denitrification exists and approximately 19.53% is removed by simultaneous nitrification and denitrification. According to the results,dissolved oxygen is an important factor to simultaneous nitrification and denitrification. The reaction rate of nitrification and denitrification is close to each other when controlling the DO value in the range of 2.8～3.7mg/L and the removal efficiency of TN is well. When the value of DO is 3.7mg/L,TN efficiency is the best and can reach 57.98%. The organic load should be controlled in a best range for getting a good TN removal result because of mutual function of autotrophic bacteria and heterotrophic bacteria in the process of simultaneous nitrification and denitrification. In this pilot the organic load should be controlled in the range of 9～17kgCOD/m3.d. Dynamics equation of simultaneous nitrification and denitrification in the aerobic zone was derived based on Monod model and analysis of the experiment data.By the observation of microscope and scanning electron microscopy,it was found that the variety of microorganisms in the reactor make the system has higher energy and substances transforming efficiency. This make the reactor has higher treatment efficiency and show good results when temperature and load exchanging greatly. These make sure that the system has stable removal efficiency. Also the process can run normally because of having these characteristics.Finally,basing on the analysis of experimental data,the actual principles of the process was studied. According to Monod equation,kinetic models of organic degradation and simultaneous nitrification and denitrification were achieved.
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