On-line estimation of unmeasured inputs for anaerobic wastewater treatment processes

This paper deals with the design of an unknown input observer for anaerobic wastewater treatment plants. A key problem in bioprocessing systems is the absence, in some cases, of reliable on-line measurements for real-time monitoring applications. The objective is to develop on-line estimation of unmeasured input (i.e. unknown input) for anaerobic processes defined as unknown input affine nonlinear systems. Based on a nonlinear state space model, the design approach is to find an observable subsystem insensitive to unmeasured inputs according to the linear theory. This subsystem is used to estimate, from available on-line measurements, the state and the unmeasured inputs. This study focuses on the on-line estimation of unmeasured inputs over a wide range of simulation and a practical experimentation on a pilot plant: an anaerobic fixed bed reactor. (C) 2003 Elsevier Science Ltd. All rights reserved.