Computer aided model analysis and dynamic simulation of a wastewater treatment plant

Abstract

A nitrogen removal benchmark was analyzed using the Activated Sludge Models No. 1 (ASM1) and No. 3 (ASM3) in order to establish a basis for designing an experimental comparison of the two model types. Differences in steady state effluent concentrations predicted by both models could to a large extent be explained by different model concepts. The steady state system performance was analyzed by evaluating the Monod factor values, and through a sensitivity analysis of the kinetic model parameters. Both methods complement each other. Analysis of the Monod factor values can lead to determination of parameters to be estimated during model calibration. The steady state system response to manipulation of the potential actuators for control was evaluated via a sensitivity analysis. The concept of relative sensitivity was introduced to compare the relative effect of each actuator in both models. The negative relative sensitivities of X S to four of the five control handles analyzed imply an opposite response of both models, which can be important for control structure design. The analysis of the process behavior to different disturbances showed different dynamics of both models. ASM3 simulation results are easier to interpret because the model structure is more transparent, mainly due to the simpler cell decay model principle considered in ASM3. An inverse response was obtained for the return sludge and nitrate recycle flow rate, indicating that multivariable control design is required.