State and parameter estimation for phosphorus removal in an alternating activated sludge process

Abstract Biological phosphorus removal involved in the advanced activated sludge process requires more efficient on-line monitoring and process control. However, the substantial complexity of the process behaviour and the limited availability of reliable on-line measurement challenge the application of advanced process control techniques. This paper presents an application of state and parameter estimation techniques in an altering activated sludge process with regard to biological phosphorus removal. A simplified model describing the phosphorus dynamics in an alternating activated sludge process is proposed based on insight into the process with a mechanistic activated sludge model. State and parameter estimation problems relating to the non-measurable dynamics of a most important limiting substrate poly-hydroxy-alkanoate (PHA) are formulated and discussed. Several schemes are presented which involve a state estimator designed with the extended Kalman filter algorithm, two specific parameter estimation procedures and an adaptive scheme for simultaneous state and parameter estimation. All these schemes are oriented to practical application and therefore some techniques dealing with the implementation are also provided. Simulations and experimental demonstrations are presented which illustrate the performance of these procedures and schemes.