Study On The Process And Characteristics Of Shortcut Nitrification-denitrification In SBR

Conventional theory considers that biological denitrification process is NH4+- NO2- - NO3- - NO2- - N2 .Shortcut nitrification-denitrification process isNH4+ - NO2- - N2. This paper searched for the conditions in which shortcut nitrification can steady in the activated sludge system, providing theory basis on wide using of the shortcut nitrification-denitrification.This paper conferred how can shortcut nitrification-denitrification take place in various controlling conditions in SBR. We also studied on the effecting factors on the shortcut nitrification of high ammonia low carbon wastewater in the low DO concentration conditions and studied on the simultaneous nitrification-denitrification phenomenon in system. A kinetic model of denitrification is builded up in this paper. The experiment results as follow:1. Shortcut nitrification-denitrification can take place in SBR when we control proper conditions. When temperature is 30+1 C , pH is 7.8~8.7 or DO concentration changes alternately, shortcut nitrification has taken place. The ratio of NO2--N/NOx--N maintains upward 90%. The concentration of nitrate nitrogen is lower than 5mg L-1.2. The shortcut nitrification process of high ammonia wastewater (concentration of NH4+ - N is higher than 260 mg L-1) in SBR is stable when low DO concentration and high DO concentration changed alternately. In this condition,lowering the temperature or prolonging the sludge age of the system affected the rate of accumulation of nitrite nitrogen faintly. SVI of the activated sludge is lower than 100 ml g-1. The circumstances that low DO concentration and high DO concentration changed alternately is the key technology of occurring of shortcut nitrification-denitrification.The feast and famine characteristic of nitrosomonas is the biological reason of shortcut nitrification.3. When we analyzed the shortcut nitrification process in low DO concentration condition, wefound simultaneous nitrification-denitrification phenomenon in the system.The conditions of the experiment is low ammonia high carbon wastewater (COD ; NH4~N=1~3 : 1), low DO concentration (0.5~1.1 mg L-1) and large sludge floc (200~500 m). We can inference that the reason of SND phenomenon in this experiment is limitation of DO diffusion and DO gradient in the sludge floc.4. The different way of adding carbon substance affects the removal of nitrogen in SND greatly.In one reaction cycle, we added carbon substance five times, 120 mg 鈥?L"1 each time. Adding carbon substance semi-continuous can provide electron receptors demanding in denitrification process and also can maintain low DO concentration circumstances, so the rate of removal of nitrogen in SND is higher than 80%.5. Analyzing the shortcut denitrification pocess,we build up the kinetic equation of shortcut denitrification. The parameters of the kinetic model is computed base on the data of experiment. The result as follow:The result showes that in this test the concentration of COD and NO2- - N is great higher than their saturation constants respectively. Therefore, the shortcut denitrification in this paper is zero-order kinetic reaction. The denitrification rate is the function of temperature and pH.