Study On Domestic Wastewater Treatment By Simultaneous Nitrification-Denitrification In SBR Reactors

Simultaneous nitrification and denitrification(SND) is a new biological nitrogen removal process.Compared with traditional biological nitrogen removal technology,this new process can save alkalinity,and it can also yield less waste biomass while keep pH stable in the reactor during treatment process,so it attracts more and more attentions all around the world.Taking synthetic domestic wastewater as the object, this paper studies the main factors such as aeration, C/N(C0D/NH₄⁺-N) and alkalinity affected SND in SBR reactor; At the same time,the mechanism of SND activity is also investigated in the reactor; and the influences of feed mode of organic carbon and the type of organic carbon on SND were studied in SBR too. In the end,the kinetic models of simultaneous nitrification-denitrfication are built up. The following conclusions are obtained in this paper:(1) The existence of SND is confirmed by the loss of TN in the aerobic stage in the reactor, so we can conclude safely that biology denitrogenation is completely feasible with a single stage.(2) DO is considered to be one of the controlling factors of the SND.So the effect of aeration on SND was studied in SBR reactors in this paper.The results shows that under the test condition,SND activity could take place no matter of the aeration quantity, and the coexistence of aerobic and anoxic zone in a floc could be a good reason to the happening of SND under low DO.(3) With a low dissolved oxygen(DO), the influences of C/N on SND was investigated by changing the quantity of carbon source. The results shows that SND could happen under different C/N,and the TN removal efficiency improves with the C/N,and when the C/N is 10,the removal rate of TN can reach about 50% and the TN removal efficiency reaches its highest level.(4) At low DO, the effects of alkalinity on SND is also investigated in this study. The result shows that with the influent ammonium nitrogen 40 mg/L and COD 400 mg/L ,the nitrogen removal improves with alkalinity,and about 56% of nitrogen is removed when the alkalinity is 12 g/g NH₄⁺-N. (5) The influences of glucose,sodium acetate,the mixture of sucrose and starch on SND were investigated while changing the type of carbon source at low DO.The results show that under the test condition,the mixture of sucrose and starch is more appropriate to be used as a carbon source for SND than biodegradable organic matters such as sodium acetate or glucose. More than 60% of the TN removal rate could be reached at 40 mg/L of ammonium nitrogen and 400 mg/L of COD using the mixture of sucrose and starch as carbon source,while took glucose or sodium acetate as single carbon ,the TN removel rate was 39% and 50% respectively.(6) The influences of feed mode of organic carbon on SND were studied in SBR too. The results show that 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,60 mg/L each time. When the influent concentration of ammonia nitrogen is 30 mg/L ,C/N is 7.5:1 and the carbon source is added intermittently,the effluent concentrations of ammonia nitrogen and TN can be decreased to 0.45 mg/L and 2.16 mg/L respectively.The removal rate of TN can reach 90%,which is 2.2 times higher than a one-time dosage of carbon source in influent under the same condition.(7) After analyzing the process of simultaneous nitrification-denitrfication,the kinetic equation of simultaneous nitrification-denitrfication is built upAnd the parameters of the kinetic model was computed base on the data of experiment. The result as follow:...