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Oxidation ditch process has convenient operation and management, low running costs, etc. advantages. In recent years, it has been widely used in wastewater treatment in China （especially the Three Gorges reservoir area）. The process uses simultaneous nitrification and denitrification technology, it is a cost-effective biological nitrogen removal treatment process. Improved Carrousel 2000 oxidation ditch process is placed the anaerobic zone and anoxic zone in front of Carrousel 2000 oxidation ditch process, it can better ensure the effect of nitrogen and phosphorus removal.Through the analysis of inflow and outflow quantity of Jingkou WWTP in Chongqing of 2009, we find the following problems: under the normal operating mode, the system has good effects of CODcr, BOD5, NH3-N, TP removal. But open five rotary aerations at the same time, the dissolved oxygen in the main trench oxidation ditch is too high,the nitrification capacity of the system is surplus , denitrification capacity is weak, so that TN has the phenomenon of excessive in the effluent at the low temperature. MLSS in system is too high, SS has the phenomenon of excessive in the effluent. And the average sewage power consumption per ton is high, about 0.31kW ? h. To solve the above problems, the test studied the hydrodynamics, the optimal operation mode and the enhanced nitrogen removal in improved Carrousel 2000 oxidation ditch.This experiment tests the trench velocity under different conditions which run of the submerged propeller and the aerate rotary disk. Be sure that the condition two （open three rotaries （A, C, D） and two propellers （X, Y）） and the condition three （open four rotaries （B, C, D, E） and two propellers （X, Y）） is relatively better working conditions. The power density of condition two is 18.87W/m3, the average flow rate of condition two is 0.124m/s, the top flow rate is 0.115m/s, the middle flow rate is 0.106m/s, the bottom flow rate is 0.150m / s. The power density of condition three is 24.38W/m3, the average flow rate of condition three is 0.140m/s, the top flow rate is 0.127m/s, the middle flow rate is 0.122m/s, the bottom flow rate is 0.172m/s.In this thesis uses RNG k–εturbulence model which was ameliorated aimed at eddy flow and curve bend wall flow to make a simulation of the experiment ditch velocity fiele of condition two and condition three. Then, the optimized deploying of the submerged propller’s and rotary’s setting place aimed at several slow area. The result shows that, the flow distribution has improved, the sludge deposits reduced. On this basis, through the test of the distribution of dissolved oxygen, sludge concentration, soluble components in improved Carrousel 2000 oxidation ditch of condition two and condition three, we find that the respective characteristics of quality components and dissolved oxygen in different segments in the ditch, it can reflect the biotransformation process of CODCr, TN, NH3-N and can divide the functional areas of biological reactions in the ditch. The condition two, sludge concentration distribution is uniform; low dissolved oxygen within the ditch, high dissolved oxygen outside the ditch; TN and NH3-N concentration decreased along the corridor, it shows that simultaneous nitrification and denitrification occurs in the oxidation ditch, and to form a multi-level AO series model. The condition three, sludge concentration distribution is more uniform than condition two; but the dissolved oxygen is too high, the bottom part is above 2.5mg/L, oxidation ditch becomes a aerobic pond, TN and nitrate concentration is unchanged in the main trench of oxidation ditch. The test for the improved Carrousel 2000 oxidation ditch process, proposed the optimized operating mode, that is condition two.
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