On the Verifiability of the Activated Sludge System Dynamics

Abstract: Wastewater treatment processes are inherently dynamic because of variations in the influent flow rate, concentration, and composition. The adaptive behaviour of the microorganisms further emphasizes this fact. Mathematical models and computer simulations are essential to describe, predict, and control the complicated interactions of the processes. Any attempt to model all details of the various reaction mechanisms are, however, destined to fail due to lacking knowledge and the extreme complexity required for such models. A reduced order dynamic model for an activated sludge process performing carbonaceous removal, nitrification, and denitrification is presented herein. The identifiability of the model is investigated using both off-line and on-line methods and its dynamic behaviour is verified against simulations of a recognized model - the IAWPRC Activated Sludge Model No. 1. The required data for the identification algorithms is based on directly measurable real time data. The simplified model may serve as a tool for predicting the dynamic behaviour of an activated sludge process since the parameters under varying operating conditions can be tracked on-line. The model is aimed for operation and control purposes as an integral part of a hierarchical control structure.