The Dangers of Uncalibrated Activated Sludge Simulation Packages

Activated sludge simulation packages are useful tools, but it can be dangerous to rely on them if they are used incorrectly. How dangerous? To determine potential pitfalls, we compared the activated sludge tank volumes predicted by three simulation packages used directly out-of-the-box without calibration. We sought to identify the underlying reason for differences in predicted required volumes.We analyzed a simple activated sludge plant to determine the relative volumes required to achieve effluent total ammonia of 1 milligram per liter (mg/L) identify abbreviations. The programs show substantial variation in projected plant performance. Plant designs based on the simulation programs would thus differ substantially. This paper shows how plant designs would vary by analyzing solids retention time (SRT), effluent ammonia, apparent yield, and relative volumes.We completed an extensive evaluation of the kinetic and stoichiometric parameters in each of the models. However, once these parameters were set to the same values, we continued to find variation in the projected plant performance.