QFT MULTIVARIABLE CONTROL OF A BIOLOGICAL WASTEWATER TREATMENT PROCESS USING ASM1 MODEL

This paper deals with the robust control of the wastewater treatment process, considered as a multivariable system, using QFT (Quantitative Feedback Theory) method. The wastewater treatment process is described by a simplified variant of ASM1 (Activated Sludge Model 1) model. Since the process is multivariable an analysis of the channel interaction, using RGA (Relative Gain Array) method, is done. According to this analysis two command channels can be emphasized. The process model was linearized in three functioning points (rain, normal and drought) and a robust controller, using QFT method, has been designed. The multivariable control structure was validated through numerical simulation in every regime, the results of the effluent quality being according to the limits imposed by the law.