Recently,　the　wastewater　treatment　process　has　become　an　effective　tool　to　improve　the　ecological　environment.　Due　to　the　inevitable　actuator　faults,　the　load　capacity　of　the　equipment　and　the　purification　efficiency　of　the　wastewater　are　reduced.　How　to　improve　the　purification　and　economic　efficiency　is　a　huge　challenge.　Therefore,　a　prescribed　performance-based　fault-tolerant　optimal　control　method　with　multivariable　is　designed　in　this　paper.　First,　the　error　transformation　function　based　prescribed　performance　is　introduced　to　achieve　stable　tracking　control.　Second,　the　fault　approximation　based　adaptive　control　method　is　used　to　solve　the　problem　of　unavoidable　actuator　faults.　Subsequently,　the　multivariable　optimal　controller　is　structured　to　guarantee　the　control　accuracy　and　equipment　energy　consumption　simultaneously.　Finally,　the　steady　state　and　transient　performance　are　analyzed　and　the　optimality　is　verified　by　some　experiments.　　©　1993-2012　IEEE.