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To further control of water pollution and accelerate the realization of water resource, China's urban sewage treatment plant emission standards become more stringent. This not only makes the new sewage treatment plant to follow the high emission standards, while the existing sewage treatment plant is also facing pressure very urgent upgrading. A2 / O process is currently China's urban sewage treatment plants commonly used in a synchronous BNR technology, therefore, the use of mathematical models ASM2D A2 / O process simulation, analysis and optimization A2 / O process control methods and best technology technical parameters, in order to further tap the potential of existing processing units, has important theoretical and practical significance. In this paper, Wuhan Dragon mouth sewage treatment plant influent water quality characteristics of biological treatment systems for the study. Consecutive one-year routine water quality analysis showed that the sewage treatment plant influent dragon mouth of each pollutant index (except NH3-N external) changes by a big margin, with the seasonal changes, is divided into two stages. The first phase, from December 2009 to June 2010 index of each pollutant influent were higher, CODCr, BOD5, SS, TN, TP and PO43-averages were: 387.8mg / L, 265.9mg / L , 376.9mg / L, 40.66mg / L, 8.20mg / L and 2.07mg / L; second phase, from July 2010 to November 2010 influent each pollutant indicators are low, the average value of each index namely: 196.8mg / L, 122.3mg / L, 138.4mg / L, 25.75mg / L, 3.87mg / L and 1.56mg / L; NH3-N is not affected by environmental factors, the annual average of 18.75mg / L. Dragon mouth ASM2D model based sewage treatment plant influent water quality component further divided, the results showed that when the influent COD is less than 350mg / L, the solubility of inert non-biodegradable organics S1, readily biodegradable organics SF, volatile acid SA, particulate Slow biodegradable organics Xs and particulate inert non-biodegradable organics X1 total influent COD proportion accounted for 7.2%, respectively, 10.9%, 7.3%, 50.9% and 23.7%; when the influent COD greater than 350mg / L, the The rates were 2.6%, 6.5%, 4.3%, 29.7% and 56.9%. The establishment of a sewage treatment plant and the dragon mouth same process parameters 24m3 / d pilot plant, using material balance analysis of internal reflux ratio (300%, 200%, 100% and 0%) of the pollutants in the A2 / O process migration and transformation and nitrogen and phosphorus removal performance. Tests showed that the reflux ratio of effluent COD, BOD5, SS and NH3-N has little effect, but within a reflux ratio helps increase nitrification rate, the four kinds of working conditions, the average nitrification rates were 104gNH3-N / (kgMLVSS · d), 102gNH3-N / (kgMLVSS · d), 89gNH3-N / (kgMLVSS · d) and 86gNH3-N / (kgMLVSS · d). In this test, there is internal reflux ratio, the internal reflux ratio of TN removal little effect, but with the internal reflux ratio decreases, TN in the selection area, the percentage removal of anaerobic zone decreases; In the absence of internal reflux conditions, the aerobic zone first SND corridor there is a clear loss phenomenon, accounting for 33.4% of TN removal percentages. In this test, with the decrease of internal reflux ratio, TP and P043-removal decreases, there is hypoxia phenomena denitrifying phosphorus, and with the decrease of internal reflux ratio increases, and the percentage of phosphorus in the aerobic tank with internal reflux decreases. Based on independent research and development research group using ASMs activated sludge process simulation software, the first of a preliminary pilot model simulation and calibration results showed that heterotrophic bacteria yield coefficient YH simulate nutrient removal system has a significant influence , autotrophic nitrifying bacteria maximum growth rate μATU of effluent NH3-N have a greater impact. Corrected model simulations and measured values are in good agreement, which simulate the effluent COD, TN and N03-relative errors were: 3.2%, 1.2% and 6.5%, due to simulated effluent TP, PO43 and NH3-N value comparison itself small, but its absolute error were 0.3mg / L or less, within the normal range. The model can simulate the process of operation, can basically meet the pilot system for the analysis of trends in nitrogen and phosphorus removal. Secondly, the use of the corrected model of the test system for process optimization found lower concentrations of pollutants in the water case, the inner reflux ratio is preferably 50 to 100%, the sludge recycle ratio is preferably 50-75% , DO aerobic tank should be controlled at 1.5 ~ 2.0mg / L range, can get better water quality, and save energy. Meanwhile, pilot systems biological treatment unit processing capability has great room for improvement.
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