ABSTRACT
Wastewater treatment plants (WWTP) with activated sludge processes (ASP) play a vital role in removing harmful organic matter, nitrogen, and phosphorus from domestic and industrial wastewater. This chapter provides a case study that presents the design of a multi-input multi-output (MIMO) QFT robust control system for an ASP-WWTP that simultaneously reduces the concentration of ammonia and nitrates in the plant effluent to meet the environmental standards. It analyzes the dynamics of an ASP-WWTP and MIMO characteristics, proposes a set of robust stability and performance specifications, designs single-input and single-output (SISO) and MIMO control solutions, and validates them in both the frequency and time domains. The chapter presents the time-domain analysis of the controllers designed in this case study. The analysis includes the simulation of the complete MIMO ASP-WWTP with both the SISO solution and the MIMO QFT solution. The case study accomplishes four simultaneous control objectives: stability; reference tracking; rejection of unpredictable disturbances; and minimization of loop interaction.
