| As a new tool, the Activated Sludge Model No.2 (ASM No.2) developed by the International Water Association (IWA) has been available in the design, performance administration, nitrogen and phosphorus removal upgrading and the development of new wastewater treatment technology and process, which has been widely used in many developed countries. However, this had not been reported in our country. This paper developed Modeling and Simulating Programs for Activated Sludge Model No.2 (MSPASM2), which was used to dynamically model and simulate the operation state of WWTP Tangjiaqiao in Chongqing, and to study its upgrading methods for biological nutrition removal.In order to solve the differential equations in the model, a computer program was developed by the author himself on the basis of Matlab 5.3, a kind of computer language mainly used in engineering calculation. Also another computer program was developed for analyzing the sensitivity of the principal effluent targets, including COD, TN, TP, NH4-N and NO3-N, to all stoichiometric and kinetic parameters and the ratio of readily biodegradable substrate to slowly biodegradable substrate. The result showed that only a limited number of model parameters influenced the model output significantly. Running the modeling program with the default parameters recommended by IWA, the modeling and simulating results suggested that there was a good agreement between the modeling values and the practical measurements for TN and TP, but it was not a case for COD. ASM No.2 proved well capable of describing the operation state of the WWTP Tangjiaqiao with adjustment of only three default parameters, namely, hydrolysis rate constant Kh from 3.00d-1 to 2.85 d-1, saturation coefficient for Xs from 0.10 gCODg-1COD to 0.13gCODg-1COD, rate constant for lysis of heterotrophic organisms bH from 0.40 d-1 to 0.48d-1. The choice of parameters to calibrate was done on the basis of sensitivity analysis. A continuous dynamic simulation for the operation state in several days was done in order to validate the model's universality. A very satisfied agreement between the modeling values and practical measurement values was obtained. The effluent quality was predicted by the calibrated and validated model when the conditions arechanged, such as influent volume, influent COD concentration, the dissolved oxygen concentration and wastewater temperature in the aeration pond. The results could provide a valuable reference data for the administration of WWTP Tangjiaqiao.Aiming at to increase the efficiency of nitrogen and phosphorus removal in WWTP Tangjiaqiao, some upgrading schemes were studied by only changing the pattern of performance without high construction costs. So two processes were considered: A/O (anoxic-oxic), a biological nitrogen removal process, A2/O (anaerobic-anoxic-oxic), a simultaneous biological nitrogen and phosphorus removal process. The efficiency of each scheme was evaluated through simulating with MSPASM2. The optimum control parameters, including the inner cycle ratio of mixed liquid, the dissolved oxygen concentration in anoxic zone and the volume ratio of each zone, were optimized through the modeling and simulating of the schemes. The results showed that: (1) The efficiency of TN removal could be increased from 34.2% to 58.6% by A/O process, if 1/4 of the existing aeration pond was changed as an anoxic zone, the dissolved oxygen concentration was 0.10 mg/L in the anoxic zone, and the inner cycle ratio of mixed liquid was 100%. Meanwhile, the effluent COD concentration could also meet the standard and the TP was hardly influenced. (2) The efficiency of the TN removal could be increased from 34.2% to 62.3% and the TP from 41.7% to 78.3% in A2/O process, if 12% of the existing aeration pond was changed as an anaerobic zone and 24% as an anoxic zone, the dissolved oxygen concentration was 0.10 mg/L in the anoxic zone, the inner cycle ratio of mixed liquid was 100%. (3)The effect of the reverse A2/O process was almost same to the A2/O process, but the former was more...
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