Activated Sludge Model(ASM3) And Its Computer Simulation Study

The Activated Sludge Models developed by the International Water Association offer a valuable instrument for design, optimization and operation of biological wastewater treatment processes, and it has been widely and successfully applied in Europe and America. However, it has developed comparatively late in China and still in the intial starting stage. In the paper,a mathematical model for activated sludge system was constructed based on ASM3 and advection-dispersion.The research involve a lot of contents including the model platform selection, model set up , model calibration and validation.At first the development of activated sludge mathematical model is reviewed. Some mechanism models, steady-state models and dynamic models which had broad influence in the world were introduced. The trace and future of the activated sludge mathematical model are indicated clearly.The ASM3 procedure using Visual Basic 6.0 based on Windows XP operation system is programed. Then analyzing the sensitivity of the principal effluent targets, including COD, NH₄⁺-N, and NO₃^--N, the results show that only a limited number of model parameters influenced the model output significantly.Wastewater characterization is the base of applying the mathematical model. Menstruation theory and methods of wastewater characterization are investigated. The results of menstruaing wastewater characterization indict that SI accounts for 5.47 percent of total COD, S_S accounts for 15.43 percent of total COD, XS accounts for 64.57 percent of total COD and XI accounts for 14.53 percent of total COD.Running the simulator with the default parameters recommended by IWA, the simulating results suggested that there are certain disparities between the modeling values and the practical measurements for COD, NH₄⁺-N, and NO₃^--N. The simulator is proved well capable of describing the operation state of the anoxic-oxic nitrogen removal process with adjustment of only three default parameters: adjust f_XI to 0.25, adjust i_{N , XS} to 0.035, and adjustμ_A to 1.07.The choice of parameters to calibrate is done on the basis of sensitivity analysis.Finally, the simulator is used to simulate the anoxic-oxic nitrogen removal process. The steady state simulation results and dynamic ones correlate well the measured values, and also confirm the practicability.