The Research Of Activated Sludge Model No.3 For Simulating And Predicting In WWTP

The Activated Sludge Model No.3 (ASM3) was proposed by International Water Association (IWA) based on the Activated Sludge Model No.1 (ASM1) and No.2 (ASM2) . It relates to ASM1 and corrects for some defects of ASM1. In ASM3 organic nitrogen is regarded as a part of organic material and storage of soluble organic substrates is added as an intermediate.m. The lysis process is exchanged for an endogenous respiration process,which makes it more approach the real biological process. Moreover, ASM3 introductsthe composition matrix lk,i together with the stoichiometric matrix vj,i.In this paper, a mathematical model for activated sludge system was constructed based on ASM3 and Takacs settling model,with the transfer process model. In order to solve the differential equations in the model, a computer program for the comination of ASM3 and second settling tank model has been developed on the basis of Matlab 7.1, which is a kind of computer language mainly used in engineering calculation. Also another computer program has been developed for analyzing the sensitivity of the principal effluent targets, including COD, TN and NH3-N, The result showed that only a limited number of model parameters influenced the model output water quality significantly. Most parameters have no or a bit influence on COD output, a few parameters have big influence on TN and NH3-N.According to the result of sensitivity analysis for 8th month and 10th month after running the modeling program with the default parameters recommended by IWA, ASM3 proved well capable of describing the operation state of the WWTP with adjustment of only one default parameters, namely, autotrophic bacteria productive coefficient from 1.0g(COD)/g(COD) to 0.925 g(COD)/g(COD) for 8th month and from 1.0g(COD)/g(COD) to 0.712g(COD)/g(COD) for 10th month.the modeling results and the simulating results expressed that there is a good agreement between the modeling values and the practical measurements for COD and TN and NH3-N. The relatively error is below 0.05%,0.55%,0.56% for 8th month and 0.03%,0.17%,0.32% for 10th month.In order to predict the effluent quality under different conditions, such as influent volume, SRT, external reflux ratio and volume ratio between denitrifying zone and nitrating zone, steady simulations and dynamic simulations for the operating state in a few continous days has been implemented by using the calibrated and validated model, Steady simulations and dynamic simulations for the operating state in a few continous days has been implemented by using the calibrated and validated model, the relative errors of COD ,TN and NH3-N through steady simulations without considering temperature for 8th month is 21.90%, 11.95%, 12.68% and 26.00%, 7.73%, 15.40% for 10th month. Also the relative errors of COD ,TN and NH3-N through steady simulations with considering temperature for 8th month and 10th month are showed. The results indicates that this program can better simulate the operating state of WWTP.In the end the developed program has been used to predict disposal effectiveness under different kinds of schemes and when the WWTP is in a full load running state. By simulating and modeling the running state of WWTP, we can get the optimum control parameters. When SRT equals to 15 days, the effluent dates of COD, TN and NH3-N can reach the standard with low running cost. The modelling results and prediction could provide a valuable reference data for the administration of WWTP.