A reduced order model for control of a single reactor activated sludge process

The IAWQ activated sludge model n degrees 1, slightly modified by adding a nitrogen limiting growth function for heterotrophic microorganisms, has bee n validated on a sequencing single sludge wastewater reactor doing nitrific ation and denitrification. However, this model is too complex to be used fo r control design. The main purpose of this paper is to show how it is possi ble to simplify the full model from biological and mathematical considerati ons. Properties of observability, controllability and theoretical identifia bility have been analyzed. The parameter identification has been carried ou t by using the simplex method of Nelder & Mead. Simulation results performe d over a range of six hours (two aerobic / anoxic cycles), show that there exists a good fit between the simulated solution and the actual behavior of a lab scale pilot plant.