Model reduction of the ASM3 extended for two-step nitrification

The Activated Sludge Model No. 3 (ASM3) extended for two-step nitrification is analyzed and reduced to enable fast and accurate simulations under typical process conditions. Due to the addition of energy storage effects, ASM3 enables the description of substrate consumption as well as Oxygen uptake with a higher precision than the older versions of the family of ASM. In addition the extension of the model to describe the two step nitrification enables the calculation of the NO2 concentration as an independent variable. An exhaustive analysis of the model results in a number of modifications which reduce the model effectively, while keeping its accuracy.