The Simulating Of Urban Wastewater Activated Sludge Process-ASM2D

As a new tool, the Activated Sludge Model No.2D (ASM No.2D) developed by the International Water Association (IWA) has been available in the design, operating administration and the development of new wastewater treatment technology and process, which has been widely used in many developed countries. Since late 1980s, the application of Activated Sludge Models has been widely used overseas. However, it has developed comparatively late in China and still in the intial starting stage. This paper developed Simulating Programs for Activated Sludge Model No.2D (SPASM2D), which was used to steadily and dynamically simulate the operation state of a certain WWTP in Southwest, and in order to offer materials for the operating administration and upgrading of WWTP.In order to solve the differential equations in the model, a computer program has been developed on the basis of Matlab 6.1, 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, TP and NH3-N, The result showed that only a limited number of model parameters influenced the model output significantly. There are 23 parameters'sensitivity absolute values beyond 0.6, which is in the proportion of 11.5%. There are 2 parameters'sensitivity absolute values between 0.3 and 0.6, which is in the proportion of 1%. There are 19 parameters'sensitivity absolute values between 0.1 and 0.3, which is in the proportion of 9.5%. Furthermore, the rest parameters'sensitivity absolute are below 0.1, which is in the proportion of 78%.Running the modeling program with the default parameters recommended by IWA, According to the result of sensitivity analysis, ASM No.2D proved well capable of describing the operation state of the WWTP with adjustment of only one default parameters, namely, autotrophic bacteria productive coefficient from 0.24g(COD)/g(N) to 0.32g(COD)/g(N).And then a very satisfied agreement between the modeling values and practical measurement values was obtained and the relative error basically below 1%.Steady simulation and dynamic simulation for the operating state in several continuous days have been implemented by using the calibrated and validated model. The average relative errors of COD, TN, TP and NH3-N via steady simulation without considering temperature influence are 20%,11%,11% and 14%, the average relative errors of COD, TN, TP and NH3-N via steady simulation considering temperature influence are 21%,12%,12% and 12%,the average relative errors of COD, TN, TP and NH3-N via dynamic simulation are 20%,12%,24% and 15%. The result indicates that the program can better simulate the operating state of WWTP. Furthermore, the thesis has predicted the effluent quality under different conditions, such as influent volume, SRT and volume ratio between nitrating zone and denitrifying zone, the result could provide a valuable reference data for the administration of WWTP. We can get the best control parameter of WWTP by simulating the operating of WWTP. And when the SRT equals to 12 days and volume ratio between nitrating zone and denitrifying zone equals to 3, we can get a best disposal effectiveness.It is suggested that the developed program consisted of ASM2D and secondary tank model is based on Matlab and could better simulate the operation of WWTP. Furthermore, it can offer significant reference materials by simulating the operation of WWTP under different conditions. So it is worthy of carrying out a further research and wider application.