Comparative evaluation of DRE integration algorithms for real-time simulation of biologically activated sludge process

An activated sludge process is considered in this work for comparative tests of new integration algorithms. Based on the configuration of the process and on the process kinetics for heterotrophic bacterial growth, the mathematical model of the considered process has been derived in the form of a state ordinary differential equation system. The state ordinary differential equation system describing the considered process may be both stiff and non-stiff for operator's control changes of the oxygen feeding flow rate. In the work, new discrete response equivalent (DRE) integration algorithms are proposed for simulation runs with a fixed integration step size, which is independent of the process dynamics (this possibility is due to self-adaptive features of the algorithms). The proposed algorithms have been compared with most other frequently used integration algorithms. The comparative tests show that, among the compared algorithms, only the DRE integration algorithms may be used with a fixed, arbitrarily chosen integration step size for simulation of the state ordinary differential equation system which may be both stiff and non-stiff during simulation.